AudioCircle
Industry Circles => Tortuga Audio => Topic started by: tortugaranger on 1 Oct 2016, 08:17 pm
-
For quite some time now (I think 2+ years qualifies) we've been modeling, prototyping and modifying various buffer designs. In fact one of my key goals for 2016 is the release of a buffer product. Time is indeed running short to accomplishment that.
Sooner or later you have to drive a stake in the ground, stop noodling around endlessly, commit to a design and produce it. That time has come for our buffer.
One of the key decisions that's been made is whether to go solid state (JFET) or tube. TUBE it is! In fact the 6CG7. For the tubular among you the 6CG7 is the smaller 9 pin version of the venerable 6SN7 octal tube.
A key design criteria for our tube buffer is we wanted to fit the whole thing, including the power supplies, inside one of our existing 3x6x8 inch extruded aluminum cases. That meant no big black honk'n transformer riding on top of the enclosure either. Everything inside. Except the tubes themselves of course. A pair of 6CG7 tubes will be standing up through the case. Figuring out how to accomplish that took a fair bit of time. We are using a pos/neg voltage doubler to produce the main split voltage power for the tubes along with 3 separate small low-profile semi-toroidal transformers mounted on a board along with the rest of the power supply circuitry. There will be 2 separate boards, the buffer board and a power supply board.
Another key design criteria was the elimination of soul-sucking coupling caps from both the input and the output the buffer. To accomplish this the tubes are powered with a split voltage +/-125 VDC supply rather than a single sided supply. Configured as cathode followers each channel has a pair of triodes connected top to bottom with the output coming out between them at essentially 0 volts. A servo circuit is included to ensure the elimination of any remaining DC offset. In the unlikely event that the DC offset gets our of bounds there's a DC offset detection and safety isolation circuit that will disconnect the buffer output. This circuit also avoids any bumps or thumps during power up and will only connect the buffer outputs once the DC offset on the output is minimal and stable.
Since eliminating coupling caps required a DC offset eliminating servo we ended up with a high quality op amp input stage using the LM49720 op amps. Hence the reference to this being a "hybrid" tube buffer. I love the LM48720's having used them before in several designs including as upgrades in a DAC I've been using. The input stage takes direct DC input and is nominally unity gain although the design does provide for switching out a couple of removable plug-in resistors if you want to boost the gain for any reason. All of this further complicated the power supply since now we needed a split +/- 15 V supply for the op amps. It's all in there!
Barring any surprises (those never happen...not!) I expect to have a near-final prototype running later this month (October) and final-final prototype in November for release by year end. I'll post some pics as soon as we have something presentable but imagine one of our LDR3.V2 preamps with a pair of 6CG7 tubes sticking out the top and you'll get the visual gist.
To be clear, this hybrid tube buffer will NOT fit inside next to our LDR preamp board in our existing preamps. The tube buffer requires additional real estate. I do envision a possible combined buffered preamp in an single package but it will be twice the width of our existing V2 preamps which means ~ 3" tall by 12" wide by 8" deep.
Watch this space! :thumb:
(http://www.tortugaaudio.com/images/6cg7_2tubes.jpg)
-
This is so nice!
Are you planning a balanced version of the buffer that can be used with LDR1B.V2?
-
Its too bad that there aren't more current production 6cg7s. The EH 6cg7 doesn't have a very good rep SQ wise. The NOS market is thin and the prices are high especially for the ones with the inner shield between the plates. On the other hand, if you find a good NOS pair, they should last a long time.
-
This is so nice!
Are you planning a balanced version of the buffer that can be used with LDR1B.V2?
Since a true balanced buffer requires an additional 2 channel tube board there's no way we can fit 2 of the existing 2-channel tube boards in a single enclosure. Even if we could there's also the issue of doubling the heater current. We have 2 amp heater capacity and only use roughly 1.2 amp but doubling it would push it past the 2 amp limit.
I suspect that it comes down to a choice of either: 1) Use 2 separate buffer units for balanced @ twice the price, or; 2) Design a balanced version of both the buffer power supply and the buffer board that still might fit in the single enclosure.
For now we're going to defer the decision on whether to go with option 2 until after the buffer has been released and has accumulated some commercial history.
-
Its too bad that there aren't more current production 6cg7s. The EH 6cg7 doesn't have a very good rep SQ wise. The NOS market is thin and the prices are high especially for the ones with the inner shield between the plates. On the other hand, if you find a good NOS pair, they should last a long time.
Given the buffer topology we're using we may be able to accommodate a 6H30 as an alternative. Have not gotten into the details on that but intend to assess the possibility.
-
Its too bad that there aren't more current production 6cg7s. The EH 6cg7 doesn't have a very good rep SQ wise. The NOS market is thin and the prices are high especially for the ones with the inner shield between the plates. On the other hand, if you find a good NOS pair, they should last a long time.
I think the current EH 6CG7 can sound very good in modern equipment that was designed around it. I agree that it can sound a bit thin in equipment designed around NOS tubes.
-
Looking at a very interesting variation using a single 6H30 tube instead of a pair of 6CG7's per stereo channel. If this holds up under testing/listening we'll be able to fit a balanced pre (2 x 6H30's) in the existing 3x6x8 inch enclosure. Another bright shiny object to slow things down. :duh: But ultimately the results are what matter. :thumb:
-
Like the 6H30, and lots of variants are available.
-
Up until recently we were pursuing a hybrid tube buffer with an op-amp input stage (with optional gain) followed by a 6CG7 cathode follower output stage using a split voltage power supply. Now we're evaluating a possible alternative approach except the input stage uses a 6H30 tube and the output stage is a proprietary solid state buffer that also uses a split voltage power supply albeit at a far lower voltage. The 6H30 input stage would have nominal unity gain with the ability to add 3-6 dB of gain if needed. Both designs have a servo to keep the output DC offset to zero so no output coupling cap is needed. Excited about finishing the evaluation and getting the best buffer version out the door! Have high hopes for the 6H30 design approach which may yield extraordinary performance with a less complicated and costly power supply. And will only need a single tube for single ended we should be able to fit a balanced version into the same enclosure using a pair of 6H30s. :thumb:
(http://www.audiocircle.com/image.php?id=151789)
-
We've made considerable progress recently on our hybrid tube buffer design which is now in its 2nd stage prototype design. I'm hopeful only one more design iteration will be needed before final production sign-off but that's admittedly optimistic.
We made some key design tradeoff decisions last week. After considerable back and forth we opted for the hybrid design shown below rather than the cathode follower variant we'd been pursuing. This resulted in swapping around the tube and solid state ends of the hybrid such that we now have a tube input stage (with some optional gain) followed by a solid state output stage. We reluctantly gave up on eliminating the output coupling cap due to the zero DC offset design getting way too complex. This design also eliminated a very bulky and oddball split voltage power supply needed by the cathode follower. The result is an elegantly simple hybrid tube buffer that sounds absolutely fantastic while keeping the parts count and cost down and fitting within our existing enclosure design envelope.
This buffer sounds wonderful when combined with our LDR attenuator on the front end. I believe we've been able to achieve our primary goal of enhancing the already great sound of our LDR passive preamp while above all else doing no harm.
To that end we've opted to go with a Belleson super-regulator for our main DC power in our base offering rather than as an upgrade option. However, there will be a few other upgrade option paths in the final base design.
Once our 2nd prototype has been fully vetted later this month I'll be able to determine pricing and come up with a release date. As much as I'd like to release the buffer before year end I'm thinking 1st or 2nd week of January is more likely but that's still very soft.
The buffer will initially be sold as a stand alone unit that can be used with any existing Tortuga passive preamps or even other passive attenuators.
How does it sound? Adding the buffer to the output of our existing LDR passive preamp does change the sound somewhat. This isn't surprising. Most tubes impart some coloration. However, in the case of this buffer it's subtle instead of being overwhelming or overly warm. Added euphonics are there typical of the 2nd order harmonics present in all tubes. Perhaps most noticeable is how the sound is a bit bolder and punchier. All while preserving the amazing clarity, detail and unveiled natural sound typical of our LDR preamps. Same yet different. Better? I could get used to this sound!! :green:
(http://www.audiocircle.com/image.php?id=153134)
-
Looks good! I like the option of adding just a little gain. This really opens up the choice of power amp nicely.
-
Very interesting. I have thought of trying a Decware tube buffer between my Tortuga and Decware SET amp. The act of adding another power cord and set of ICs seems like it might take away some detail. This definitely seems worth trying though if it adds a little more punch to the sound.
-
To that end we've opted to go with a Belleson super-regulator for our main DC power in our base offering rather than as an upgrade option.
Morten,
Would the buffer be able to provide power to the LDR unit, and would there be any added benefit?
-
Morten,
Would the buffer be able to provide power to the LDR unit, and would there be any added benefit?
The buffer will have a 12V regulator and power takeoff that can be used to power an existing Tortuga preamp. This regulator can be optionally upgraded to a Belleson regulator as well which can benefit existing preamps. Users of our PS12B battery power supply have reported improved performance so upgraded power from the buffer should provide similar benefits.
The new V3 preamps (when finally released) will also be able to be powered via the buffer although due to the V3 having a different power arrangement a Belleson upgrade will need to be done at the V3 controller board instead of the buffers 12V supply.
-
Will the buffer be available in kit form that can be retrofitted to existing kit built Tortuga pre?
-
Will the buffer be available in kit form that can be retrofitted to existing kit built Tortuga pre?
The idea of offering the buffer in kit form has really not been considered. My focus has been on design and performance and more broadly on how the buffer will fit into our current and future preamp products. What I can say for sure at this point is there will be no kit version initially. No doubt we will revisit thst down the road.
-
The idea of offering the buffer in kit form has really not been considered. My focus has been on design and performance and more broadly on how the buffer will fit into our current and future preamp products. What I can say for sure at this point is there will be no kit version initially. No doubt we will revisit thst down the road.
I expected you'd say that. :( I certainly understand. Oh well... I tried. :)
Actually, I've been getting by very well without a buffer since the Tortuga really doesn't need one unless you have unusually low output voltage on the source. My source voltage is marginal but adequate. I expect to be getting a new DAC soon. I'll definitely make sure that it'll have more voltage. It would be nice to experiment though.
-
I expected you'd say that. :( I certainly understand. Oh well... I tried. :)
Actually, I've been getting by very well without a buffer since the Tortuga really doesn't need one unless you have unusually low output voltage on the source. My source voltage is marginal but adequate. I expect to be getting a new DAC soon. I'll definitely make sure that it'll have more voltage. It would be nice to experiment though.
Adding a tube buffer downstream of the LDR attenuator adds some "tube flavor" and perhaps some more punch but in switching back and forth between pure passive and buffered I think it comes down to personal preference in terms of which one is better or more pleasing to listen to. I'll have more to say on that subject once we have our latest prototype up and running. Design details do matter so I'm reserving my final opinions until the final design is ....well...er....final. Very soon I hope. :thumb:
-
Now your talking, I was interested in your LDR designs but really liked the sound
of the 6H30 (Thanks Gary Dood for your buffer), so I wanted to upgrade to a line
stage with this tube and also balanced since I am right under a radio station, so I
got a Audio Research LS17SE and I am loving it, have been looking at upgrading
to the LS27 since it has adjustable gain, the gain I have now is a little to high with
my class d amps, but it looks like I might have to wait for this!
-
Any "ballpark" figures for input/output impedance?
-
Any "ballpark" figures for input/output impedance?
The input impedance is somewhat arbitrary and it set by an input stage resistor. It will likely be at least 47k and may be as high as 100k. That's a fine tuning decision that we'll test in the final prototype board which we will have in-house by Friday/Saturday this week. Although the designation "final prototype board" tends to be used prematurely we are really close to finalizing this puppy.
The output impedance is approximately 20 ohms which is inherent in the output stage stage design and is not likely to change. That is a modeled value and not a test value but is very much in the ballpark of what it will really be.
-
The input impedance is somewhat arbitrary and it set by an input stage resistor. It will likely be at least 47k and may be as high as 100k. That's a fine tuning decision that we'll test in the final prototype board which we will have in-house by Friday/Saturday this week. Although the designation "final prototype board" tends to be used prematurely we are really close to finalizing this puppy.
The output impedance is approximately 20 ohms which is inherent in the output stage stage design and is not likely to change. That is a modeled value and not a test value but is very much in the ballpark of what it will really be.
That's great news, thank you!
-
The latest prototype board of our hybrid tube buffer arrives in the mail tomorrow. I'll be stuffing that board ASAP and firing it up over the weekend to see where things stand. This is the 3rd prototype revision of this particular design so I have high hopes that everything will fall into place.
Assuming this prototype performs well, we'll start accepting pre-orders (no upfront payment) in December with release scheduled for later in January.
I'll update this topic as soon as I've had some run time on the latest prototype. Getting very close!!! :thumb:
-
:thumb: Can't wait
-
Try using the 6N6P.
-
Try using the 6N6P.
I've not tried the 6N6P but no doubt there will be opportunity for tube rolling with our tube buffer. The most common constraint in trying alternative tubes is that the existing heater power supply doesn't have sufficient current capacity. That will not be the case with our tube buffer since the 6H30 is already a high current tube. It looks like the 6N6P is slightly higher current than the 6H30 but that won't be a problem. Gain may get all wonky with other tubes but if necessary this can be overcome changing out a resistor or two.
-
We just published our latest article on the website entitled "Is An Audio Buffer Right For You?"
Yes, I know that's a corny title but the purpose of the article is to educate audio enthusiasts who aren't technical experts on what a buffer does. where a buffer fits in the audio signal chain, and why you might benefit from using a buffer.
Here is the article: http://www.tortugaaudio.com/is-an-audio-buffer-right-for-you/ (http://www.tortugaaudio.com/is-an-audio-buffer-right-for-you/)
Look forward to any comments or suggestions.
Cheers,
Morten
-
Any ballpark estimate on how much this is going to cost?
Any thoughts on a tour?
-
Any ballpark estimate on how much this is going to cost?
Any thoughts on a tour?
Still a few days away from finalizing pricing. Need to confirm latest prototype design is good to go which I should know by next week.
There will definitely be a tour!! :D
-
There will definitely be a tour!! :D
Sign me up!
-
Sign me up!
Me too!!!
-
There will definitely be a tour!! :D
Don't leave me out. Sign me up too!
-
There will definitely be a tour!! :D
If we are starting the list now, please sign me up too!
-
RE: Tour - Please count me in. Glynn Wilson
-
I would absolutely want to be included on this tour. Still looking for a pre and this just might be the ticket!
Regards,
Randy
-
Holy crap this buffer sounds good!!! :o
Have it connected to the output of an LDR3.V2 Passive. Amazing dynamics. Really has some serious punch. All the great qualities of the LDR attenuator but more muscular. I was running one channel through the buffer and the other purely passive and then was switching between left/right (buffered/unfbuffered channels. The unbuffered passive is very smooth and musical - polite! The buffered version is way more in-your-face! The buffer is set up with unity gain so same volume both channels. Noticed that listening at lower volume levels is more satisfying with the buffer compared to the unbuffered passive.
Still not ready for prime time though. The heater power supply design needs more refinement to get it dead quiet. Heaters draw close to 1.7 amps. Also want to be able to use even slightly more power hungry tubes that need almost 2 amps for a pair of heaters. That means putting everything on a single board is out. May end up with a toroidal transformer with cover on the top of the enclosure. We'll see. Divide and conquer!
For those interested in a tour, I will set up a separate tube buffer tour topic to plan and manage that.
-
Hi Morten,
If there's a balanced version of the tube buffer in the works, I definitely want to try it. As you know, my biamplified system using an LDRxB-V2 (with absolute phase switching) and an LDR1B-V2 to trim the level match the bass amp is a prime candidate for a buffer.
I have to say, though, that converting both of my Tortugas to battery power took my system to another higher level altogether and I'm curious how the active power supply of a Tortuga tube buffer would affect that change.
Best,
Robert
-
Hi Morten,
If there's a balanced version of the tube buffer in the works, I definitely want to try it. As you know, my biamplified system using an LDRxB-V2 (with absolute phase switching) and an LDR1B-V2 to trim the level match the bass amp is a prime candidate for a buffer.
I have to say, though, that converting both of my Tortugas to battery power took my system to another higher level altogether and I'm curious how the active power supply of a Tortuga tube buffer would affect that change.
Best,
Robert
It's being designed so that it can be configured as either SE or balanced. There's a triode for each channel. For SE only one side (+) of each triode is used. For balanced both sides (+ & - ) are used. :thumb:
-
A quick development status update. Space constraints forced us to split the single buffer board into 2 separate boards: 1) power supply board, and; 2) tube board. The PS board sits in the lowermost slot near front of the enclosure and the tube board occupies a higher slot closer to rear of enclosure. The boards overlap slightly but they don't interfere.
We've avoided moving the heater transformer to the outside of the enclosure. The PS board now has a larger 50VA low noise toroidal type transformer for powering the dual heaters via a robust zero ripple switch mode dc-dc converter that runs at 600khz. The previous conventional transformer was working way too hard and too hot. Changing from a linear regulator to switching has also significantly reduce internal heat generation.
Prototype boards for the revised design have been ordered. I expect the boards to arrive by mid-month at which time I hope to report that the design phase is essentially done.
If all goes well I can see releasing the buffer towards the end of January.
-
Our PCB fabricator produced a bad batch of boards so they had to redo one of the prototype boards. Lost a week. :duh:
Should have latest buffer boards in house by midweek before Christmas (next week!) and check them out well enough to know whether we are done or not with initial development. If we are done then I will announce the release of the hybrid tube buffer for late January. Will take the time between now and then to accept pre-orders and get production tee'd up.
The combination of LDR attenuation with a tube preamp buffer is going to be awesome good stuff! :thumb:
Cheers,
Morten
-
Have the latest prototype boards up and running. :D Major progress and only a couple of minor setbacks. :oops: Have to share some the setbacks. This is audio sausage making.
Couldn't help but notice that after initial power up that the plate power transformer was running really hot. Like too hot to touch hot. Very strange give that the current demand is only a handful of milliamps. After chasing numerous dead ends finally realized I'd installed the wrong relay and was completely shorting out the transformer secondary. We have 2 relays in our parts bins that are same brand, size, color, and pinouts. So of course in my excitement to get the buffer running I managed to pick the wrong one. Space heater - 1 point. Engineer - 0. As a bonus for screwing up the power supply relay the Belleson Superregulator was toast. A quickly assembled LM317 module replaced the Belleson and we were back in business. Now I had hum but only in one channel. Hmmmm. Swapped the tubes and the hum changed channels. Bad tube. Development testing is hard on the hardware.
Despite these setbacks we are 98% done. The last 2% involve some minor rework on the 2 boards to optimize connectors, increase parts clearance between the 2 boards, tighten up the star grounding layout, and just generally dot the i's and cross the t's on the schematics and boards layouts.
Listening to the preamp buffer as I write this. Amazing dynamics. Best audio I've ever heard.
When we're back up and running after the New Year's break, production hardware orders will be placed with the goal of releasing the tube preamp buffer by the end of January. Over the break I'll work on finalizing pricing and set up pre-orders on the website. More on that soon.
The pics below show a close up of the tubes running in a temporary enclosure. The bottom pic is a rough shot of the prototype assembly. Power supply in foreground. Tube board in background laying on its side. Power entry module on the right. Temporary I/O jacks. It's all good!
Cheers,
Morten :thumb:
(http://www.audiocircle.com/image.php?id=155279)
(http://www.audiocircle.com/image.php?id=155280)
-
Need some info. PM sent.
-
That looks great, and I am anxious to hear my own!
Merry Christmas everybody!
Mark
-
Hi All!
We have officially set the release date for the TPB.V1 Tube Preamp Buffer (the "V1") for February 15th (this year!!!)
Between now and then we are accepting pre-orders.
More info on the TPB.V1 can be found here: http://www.tortugaaudio.com/products/preamp-buffers/tpb-v1-tube-preamp-buffer/ (http://www.tortugaaudio.com/products/preamp-buffers/tpb-v1-tube-preamp-buffer/)
The linked info is missing a detailed technical specification but that will be available soon and appended.
Good news if you're already a Tortuga Audio customer - 20% discount off the base price during the pre-order period only. Email me (morten@tortugaaudio.com) if you're interested and I'll send you a coupon.
I've been listening to the V1 buffer for a few weeks now on two different systems mated with a Tortuga Audio LDR3.V2 passive preamp/attenuator. I couldn't be more pleased with the sound. Full, lush, dynamic and with awesome bottom end. A wall of sound. I'm not a reviewer so I'm running out of clever adjectives and metaphors. It gets my most favorite accolade....it's satisfying!
Last but not least, I want to give a heartfelt shout-out to Trung Tran, Mark Nash and Richard Palmer for their ideas and help with the development of the V1. You guys are the best!
Cheers,
Morten :thumb:
(http://www.tortugaaudio.com/images/TubeBufffer_FrontView_Mockup.jpg)
-
No way to keep the tubes inside the box? :cry:
-
No way to keep the tubes inside the box? :cry:
Candidly, it never occurred to me put the tubes inside the enclosure. I could give you all the practical reasons having to do with space constraints, concerns with heat/cooling etc. but those would be secondary to the real reason.
Tubes are one of the few if only audio electronic components that has its own visual aesthetic. Simply put, they're very nice to look at. All those little bits of metal enclosed in a little (or not so little) shiny sealed glass bottle that if you we inside one you'd die from lack of oxygen and your blood would boil like it would in the vacuum of outer space (just before is froze). That's cool stuff that. Then there's "tubes at night" sitting there outside the box all warm and orangey glowly, like a failed attempt at designing a light bulb only to realize your crappy light bulb can reproduce music beautifully - what a great consolation.
Tubes are both anachronistic yet very contemporary. They all but disappeared once transistors showed up but not in guitar amps and not in audio gear. When I was a kid our TV ran entirely on tubes and the father of one of my school mates was the local TV repairman. He'd show up with a large fold-out case filled with all manner of tubes. His job along with typewriter repairmen are long gone. The typewriters also went away. But the tubes didn't.
Most people I know don't care or know squat about audio and are actually quite stunned when I tell them a good deal of audio gear today is made with tubes - on the outside! "Really?", they say. "Oh yeah", I tell them. I'm sure some of them think I'm joking.
The thermionic valve is cool looking retro kit. They sound great. They make use feel good. Can't have too much of that.
That's why the tubes are on the outside. :thumb:
-
Don't wanna say "Told Ya So!", but... :wink: I'm still loving my Tortuga w/ tube buffer I built last year.
On balanced I'd consider having the buffer SE only and use an output coupling trafo to convert from SE to Balanced... PP/differential tube circuits are going to lose some of that magic imo. Instead of not using one of the triodes in the tube use it as a plate load for the other triode.
Even with XLR in I'd just leave pin 3 disconnected to anything or attached to pin1 via a resistor with the same value as the input impedance, use a single LDR board... SE in, SE out and a Jensen or other high quality trafo to produce an XLR out.
-
Don't wanna say "Told Ya So!", but... ;) I'm still loving my Tortuga w/ tube buffer I built last year.
On balanced I'd consider having the buffer SE only and use an output coupling trafo to convert from SE to Balanced... PP/differential tube circuits are going to lose some of that magic imo. Instead of not using one of the triodes in the tube use it as a plate load for the other triode.
Even with XLR in I'd just leave pin 3 disconnected to anything or attached to pin1 via a resistor with the same value as the input impedance, use a single LDR board... SE in, SE out and a Jensen or other high quality trafo to produce an XLR out.
And then he told me so. :lol:
Glad you're enjoying your Totuga w/ buffer. I do get it.
I almost went with a similar cathode follower arrangement to what you have but opted instead for a hybrid approach after some comparison listening and thinking perhaps the world doesn't need another cathode follower when we can offer something different. Since different has been our philosophy to date, why not.
Back when we were just coming out with a balanced version of our LDR attenuator I received somewhat similar advice regarding the attenuation of balanced signals. Instead, we stayed with true independent attenuators for each phase which meant 4 channels of LDR attenuation for balanced stereo. I'm glad we did because it has worked out wonderfully.
If, as you suggest, running differential signals in parallel through a triode proves to be a disappointment we'll definitely consider your approach. So far, I've not noticed a problem with it. But one thing I've learned is that you don't really fully understand your design/product until it's out the door in other people's systems and all the "interesting" stuff that never happened in your shop shows up in other peoples' systems.
Best,
Morten
-
Using balanced circuitry has a lot of potential advantages, but in this case I expect you'll find it's more expensive and complicated for a result that may not sound as good. I would guess using single ended circuitry and putting money you'd spend for duplicate parts for a balanced circuit into better quality parts would result in a better sounding preamp. You'd also have the same preamp for SE vs XLR users instead of the XLR version costing a lot more.
Also, if you haven't, try Clarity TC caps in the last stage of the power supply, imo it completely transforms the sound of tube preamps and amps. :)
-
Using balanced circuitry has a lot of potential advantages, but in this case I expect you'll find it's more expensive and complicated for a result that may not sound as good. I would guess using single ended circuitry and putting money you'd spend for duplicate parts for a balanced circuit into better quality parts would result in a better sounding preamp. You'd also have the same preamp for SE vs XLR users instead of the XLR version costing a lot more.
Also, if you haven't, try Clarity TC caps in the last stage of the power supply, imo it completely transforms the sound of tube preamps and amps. :)
Hi Dave,
Appreciate your perspective. However, once we made the decision to dedicate a separate triode to each stereo channel this effectively made the tube preamp buffer into a balanced design that can also be configured for SE by simply leaving out parts in the SE version. Since the PS was designed to power 2 heaters there's minimal savings with the SE version. Had we come at it the other way and focused on the lowest cost SE version, we would have needed separate parallel version of the boards and certain parts etc. for the balanced version. At the end of the day we wanted the balanced buffer to be....well....balanced. :green:
We are running the 6H30's with a plate supply voltage of only 30V. That low a voltage gave us the option of using a Belleson SuperRegulator as an upgrade option to power both the tube and solid state output stage with marvelous results.
Best,
Morten
-
Last night I installed a set of V-Cap OIMP (oil impregnated metallized polypropylene) output coupling caps that had arrived earlier in the day. The stock caps are either WIMA and Vishay poly caps.
I have to say the V-Cap's really made a difference. Smoother, more realistic, greater detail and better able to handle bigger more complex bits of music like rock or big orchestral. A highly recommended upgrade for sure.
I've been reluctant to use oil-anything when it comes to capacitors due to potential leakage. But after doing a fair bit of research I'm convinced V-Cap has clearly solved that issue. Their caps come in a sealed metal can - very robust. They're much bigger physically than our stock caps but we've been able to fit them in.
-
Morten,
Thank you for letting me in the tour, can't wait.
I'm currently tube rolling a Yaqin SD-CD3 tube buffer. One thing I wish I could do is to swap out tubes in the buffer
without having to power down all my equipment. Could that be possible in your buffer for future versions?
Thanks
Steve
-
Morten,
Thank you for letting me in the tour, can't wait.
I'm currently tube rolling a Yaqin SD-CD3 tube buffer. One thing I wish I could do is to swap out tubes in the buffer
without having to power down all my equipment. Could that be possible in your buffer for future versions?
Thanks
Steve
I think the buffer itself would be indifferent to having tubes pulled and replaced while powered up. Still, I would advise against doing this. The 6H30 tubes draw close to 1 amp of heater current each. Even though it's only at 6.3 volts I don't think it's wise to hot swap anything that draws that high a current.
The biggest argument against hot swapping tubes with the rest of you system powered up and/or connected is you'll undoubtedly get a big DC bump as the tube powers down/up. You might also see a brief AC signal on top of the bump. You speaker's driver cones will likely breathe in/out significantly if only for a moment. May not do any harm but not good practice.
I would advise to ALWAYS turn off your amp 1st before shutting down anything upstream, and to turn on your amp last after turning on everything upstream on. The one exception I'm comfortable with turning on/off while leaving everything else on is our LDR passive preamps. Anything with a tube will act wonky until it heats up. Much less so with solid state gear. We opted to leave out any output relay in our buffer so this caution applies to the buffer as well.
Personally, I use a sequenced power management unit with delays so things turn on and off predictably to avoid bumps.
-
^^+100^^
What Morten said. Besides, why would you hot swap a tube and risk burning your fingers in the process? :scratch: Even if you used gloves, it's still an extra step.
There aren't that many 6H30 tube variants out there in all honesty. It's not like the 6DJ8/6922 which has a huge number of variants (amongst fakes), and far less filament current requirements.
Best,
Anand.
-
I would advise to ALWAYS turn off your amp 1st before shutting down anything upstream, and to turn on your amp last after turning on everything upstream on. The one exception I'm comfortable with turning on/off while leaving everything else on is our LDR passive preamps.
There's off and then there's OFF. I had an experience when I was making a minor change to my system and it happened to include powering off my Tortuga. As I recall I just wanted to reroute its AC power cord. The source was still sending music and the amps were on (smart guy, right?) and when I plugged the power cord back into the Tortuga the music started back up, but at full volume. This lasted several seconds until the LDRs' previous settings were automatically restored. No damage was done, but it was shall we say "disconcerting".
I've never had any kind of pop, surge, DC to the woofers, etc. when reactivating the Tortuga from its "sleep" mode, but I would avoid actually removing/restoring power to the unit without powering off at least the downstream components.
Robert
-
There's off and then there's OFF. I had an experience when I was making a minor change to my system and it happened to include powering off my Tortuga. As I recall I just wanted to reroute its AC power cord. The source was still sending music and the amps were on (smart guy, right?) and when I plugged the power cord back into the Tortuga the music started back up, but at full volume. This lasted several seconds until the LDRs' previous settings were automatically restored. No damage was done, but it was shall we say "disconcerting".
I've never had any kind of pop, surge, DC to the woofers, etc. when reactivating the Tortuga from its "sleep" mode, but I would avoid actually removing/restoring power to the unit without powering off at least the downstream components.
Robert
Very good clarification Robert. Removing/applying power from/to an LDR preamp results in a brief period during which the volume will surge. I recommend either leaving our LDR preamps powered but turned off..OR...always sequencing powering down by shutting off your amp first.
-
Nice work. Big difference between 6H30 and 6N6P is heater cathode isolation. If you are running more than 120v on the plates, you may have some issue with exceeding that spec, unless the Heater is biased to the B+. Many people ignore that spec, but I try not to. Great tube regardless. And the 6N6ps are under $3 each.
-
Nice work. Big difference between 6H30 and 6N6P is heater cathode isolation. If you are running more than 120v on the plates, you may have some issue with exceeding that spec, unless the Heater is biased to the B+. Many people ignore that spec, but I try not to. Great tube regardless. And the 6N6ps are under $3 each.
Are running a plate voltage of only 30V on the 6H30's. No problem.
-
That is where the famous Dodd buffer runs them. Good choice.
-
That is where the famous Dodd buffer runs them. Good choice.
I think Trung is involved in this project so it's of no surprise. :wink:
-
I just verified via a quick test that you can drop a set of 6CG7's into our buffer as substitutes for the 6H30's with no problem. No surprisingly the gain is a bit off (slightly higher gain with the 6CG7s) but that was just my impression and I didn't confirm this with a scope or dB meter. Sounded real good with the 6CG7's.
Someone asked if 12AU7's would work and the answer is no because the 12AU7's use a different heater circuit. Same for the 12AX.
-
Small preamp buffer.
Amazing sound.
Pretty cat.
(http://www.tortugaaudio.com/images/buffer_with_cat_rev1.jpg)
-
An update to the tour schedule would be great.
I have 2 Yaqin CD3 tube buffer's that I use in my system.
I'm ready to compare the Tortuga buffer to my Yaqin's.
-
A couple of additional buffer pics. :thumb:
(http://www.tortugaaudio.com/images/RearCorner.jpg)
(http://www.tortugaaudio.com/images/tubes_front.jpg)
-
Which connection "to and from" a Tortuga Tube Buffer makes the most since?
Phono-pre or Dac output > Tortuga Buffer > Preamp input.
Preamp output > Tortuga Buffer > Active crossover input.
Active Crossover HI-Pass output only > Tortuga Buffer > Amp for Hi-Pass Frequencies.
-
Which connection "to and from" a Tortuga Tube Buffer makes the most since?
Phono-pre or Dac output > Tortuga Buffer > Preamp input.
Preamp output > Tortuga Buffer > Active crossover input.
Active Crossover HI-Pass output only > Tortuga Buffer > Amp for Hi-Pass Frequencies.
The second. Preamp > Buffer > ...
-
:thumb:
-
Morten,
Reading this thread leaves me confused (as usual). > symbols confusing. I have my buffer after the preamp, buffer into the power amp. Is that the best way?
Randy
-
Morten,
Reading this thread leaves me confused (as usual). > symbols confusing. I have my buffer after the preamp, buffer into the power amp. Is that the best way?
Randy
Yes. Buffer downstream of attenuator/passive. It WILL work the other way around but you won't retain all the benefits of the low fixed output impedance of the buffer.
-
Per customer request I recently tested our TPB.V1 Tube Buffer with an ECC88(6922) tube instead of our standard 6H30. Since I only had a single ECC88 available I could only test it in one channel and left the other channel empty/silent. My initial impressions were quite positive. I then put a 6H30 back into the empty slot and ran the buffer with an ECC88 in one side and a 6H30 in the other. Sounded remarkably good and to my surprise the stereo was well balanced indicating that the effective gains were quite similar. I've not compared the specs sheets in detail other than to confirm that the heater current for the ECC88 is substantially lower than the 6H30 (not many 9 pin tubes run as high a heater current as the 6H30's). I've ordered a second ECC88 tube of same make/model and will give the buffer a more thorough listen once I have a pair of ECC88's installed.
While a bit preliminary, I'd say the TPB.V1 buffer is now compatible with not only the 6H30, but also the 6CG7 (the 9 pin version of the 6SN7 octal) and now most likely the ECC88 which also includes the whole 6DJ8 / 6922 / ECC88 / E88CC / CV2492 family tubes.
A tube roller's delight! :thumb:
-
Sounds great!
Especially that you say it opens up possibilities to roll the 6DJ8 / 6922 / ECC88 / E88CC / CV2492 family of tubes.
But just curious about the life of the different tubes. E.g. if some tubes are hotter, or driven harder than other tubes,
how does that effect the life of the tube (if we buy expensive NOS tubes, I would want to know that I am getting some
decent amount of life out of them).
The ability to choose a +3 or +6 dB gain is also so useful. Just thinking that a -3dB gain would also be equally beneficial
for the "loudness wars" recordings.
-
But just curious about the life of the different tubes. E.g. if some tubes are hotter, or driven harder than other tubes,
how does that effect the life of the tube (if we buy expensive NOS tubes, I would want to know that I am getting some
decent amount of life out of them).
In normal preamp/amp applications most tubes run at plate voltages in the range 100-450 volts depending on the spec of the tube. The tubes in our buffer are run at a modest 30 volts with commensurate low current since the tube is used as an input stage with default 0 dB gain. One could argue that at such a low plate voltage/current the life of most any tube in such an application is indefinite. Of course then there's the tube heaters which run at 6.3 volts DC but that's the same for all these tubes in any application and running them in our buffer isn't going to be better/worse in terms of their life as far as heater longevity is concerned. In short, our buffer does not run hot nor does it drive the tubes hard. It also uses a switch mode DC-DC regulator for the heater current so that internally the buffer power supply generates very little heat compared to using most any linear regulator. In my view this hardware, including the tubes, will last a very very long time.
The ability to choose a +3 or +6 dB gain is also so useful. Just thinking that a -3dB gain would also be equally beneficial
for the "loudness wars" recordings.
-3dB etc. is the job of your preamp/attenuator upstream of the buffer. :thumb:
-
I just changed out the stock tube with "Gold Lion" E88CC. A nice bump up in the sonics. Cleaner, clearer, richer, more transparent even before they warmed up. Impressive. An already great product takes a step up. Way more than I expected, if I expected anything, skeptic that I am.
I went for all the alternatives they offer, triode, high gain,balanced, low noise and microphonics. I really don't know what most of that means, but it sounded good, and didn't add that much to the basic cost. Maybe Morten can offer some comments.
-
I am interested in how a tube stays linear with such a low plate voltage.
-
I am interested in how a tube stays linear with such a low plate voltage.
In a buffer application you aren't asking the tube for any voltage gain so you don't need much voltage swing from the output. You are basically just tracking the linestage input which is a few volts at most. You're also operating with grid input voltage at or near 0 volts with no input coupling cap. Down in that corner near zero Vgs and low plate voltage you can actually get fairly linear operation. It can work surprisingly well.
(https://www.tortugaaudio.com/images/6h30_tube_curves.jpg)