Hybrid Tube Preamp Buffer

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tortugaranger

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Re: Hybrid Tube Buffer
« Reply #40 on: 22 Dec 2016, 09:08 pm »
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:


 


WireNut

Re: Hybrid Tube Buffer
« Reply #41 on: 22 Dec 2016, 10:41 pm »
Need some info. PM sent.

markn

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Re: Hybrid Tube Buffer
« Reply #42 on: 22 Dec 2016, 10:42 pm »
That looks great, and I am anxious to hear my own!

Merry Christmas everybody!

Mark

tortugaranger

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Re: Hybrid Tube Buffer
« Reply #43 on: 14 Jan 2017, 03:13 pm »
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/
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:


OzarkTom

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Re: Hybrid Tube Buffer
« Reply #44 on: 14 Jan 2017, 04:38 pm »
No way to keep the tubes inside the box? :cry:

tortugaranger

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Re: Hybrid Tube Buffer
« Reply #45 on: 15 Jan 2017, 05:33 pm »
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:

DaveC113

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Re: Hybrid Tube Buffer
« Reply #46 on: 15 Jan 2017, 06:04 pm »
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.


tortugaranger

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Re: Hybrid Tube Buffer
« Reply #47 on: 15 Jan 2017, 06:42 pm »
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

DaveC113

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Re: Hybrid Tube Buffer
« Reply #48 on: 16 Jan 2017, 01:01 am »
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. :) 


tortugaranger

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Re: Hybrid Tube Buffer
« Reply #49 on: 16 Jan 2017, 02:32 pm »
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

tortugaranger

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Re: Hybrid Tube Buffer
« Reply #50 on: 16 Jan 2017, 03:07 pm »
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.

WireNut

Re: Hybrid Tube Preamp Buffer
« Reply #51 on: 28 Jan 2017, 10:39 pm »
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

tortugaranger

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Re: Hybrid Tube Preamp Buffer
« Reply #52 on: 29 Jan 2017, 01:14 pm »
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.


poseidonsvoice

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Re: Hybrid Tube Preamp Buffer
« Reply #53 on: 29 Jan 2017, 03:13 pm »
^^+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.

kernelbob

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Re: Hybrid Tube Preamp Buffer
« Reply #54 on: 29 Jan 2017, 03:22 pm »
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

tortugaranger

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Re: Hybrid Tube Preamp Buffer
« Reply #55 on: 29 Jan 2017, 03:32 pm »
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.

sfox7076

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Re: Hybrid Tube Preamp Buffer
« Reply #56 on: 30 Jan 2017, 11:05 pm »
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. 

tortugaranger

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Re: Hybrid Tube Preamp Buffer
« Reply #57 on: 30 Jan 2017, 11:48 pm »
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.

sfox7076

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Re: Hybrid Tube Preamp Buffer
« Reply #58 on: 1 Feb 2017, 01:10 pm »
That is where the famous Dodd buffer runs them.  Good choice.

jtwrace

Re: Hybrid Tube Preamp Buffer
« Reply #59 on: 1 Feb 2017, 01:47 pm »
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: