[etcarroll]

Thoughts?  Experiences?

I need a phono pre, 6 6922 tubes are a lot of tube goodness, at least on paper.

http://www.enter.net/~cae/sades_3.htm

Gene

[poseidonsvoice]

Gene,

Here is another one that should float your boat. Read the entire page. My choice would be the Maxxed Out Phono.



Kevin Carter designs for some really big names in the industry including Art Audio and was formerly employed at VAC.

Joe Curcio isn't my favourite of designers. Although current sources are great, his applications of them make me run from the room. There are others that do the job far better and have better ears imho. Look to Kevin Carter, Allen Wright, Ralph Karsten, Dan Schmalle (Bottlehead), J. Broski (who designed the Aikido, etc...), Lynn Olson and Gary Pimm (Pimm regulators and awesome differential amps using 45 tubes).

It's better to concentrate on the designer than on what parts quality they use first. Kevin Carter in my opinion wears both hats quite judiciously. Joe in my experience does neither and I don't feel his kits are of value to be honest. Too much competition out there.

Best,
Anand.

[etcarroll]

Thanks Anand, very interesting project, though gets pricey in a hurry.

I have Bottlehead on my shortlist already, not sure how to equate the other names to product. Is it as simple as Googling them?

Gene

[poseidonsvoice]

Here's a few:

Lynn Olson/Nutshell Hifi (but he doesn't sell/design phonostages to my knowledge)

Allen Wright/Vacuum State

John Broski/TubeCad/Aikido designs

Personally just the standard (i.e.non-Maxed) SET phonostage that Kevin Carter designs should slam dunk Joe Curcio's design having heard it myself. I'm not much a vinyl guy...although I'm a wannabee... Kevin's deck is nothing to sneer at, last I remember he had a mega expensive Nottingham at his chateau...

Best,
Anand.

[JakeJ]

Gene,

Here is another one that should float your boat. Read the entire page. My choice would be the Maxxed Out Phono.



Kevin Carter designs for some really big names in the industry including Art Audio and was formerly employed at VAC.

Joe Curcio isn't my favourite of designers. Although current sources are great, his applications of them make me run from the room. There are others that do the job far better and have better ears imho. Look to Kevin Carter, Allen Wright, Ralph Karsten, Dan Schmalle (Bottlehead), J. Broski (who designed the Aikido, etc...), Lynn Olson and Gary Pimm (Pimm regulators and awesome differential amps using 45 tubes).

It's better to concentrate on the designer than on what parts quality they use first. Kevin Carter in my opinion wears both hats quite judiciously. Joe in my experience does neither and I don't feel his kits are of value to be honest. Too much competition out there.

Best,
Anand.

Here is information I needed about five years ago when I rebuilt my Dyna Mk III monoblocks.  I now have a pair of VAC PA-160 monoblocks that just blow the Dynas away in terms sound quality, and I paid less for the VAC amps than I have into the Dynas.  I've never been particularly impressed with the Dynas SQ and I wish there was something I could do to fix them but honestly I should probably just sell them and move on.

I was so impressed with the VAC amps that I sold my highly modded McCormack ALD-1 preamp and bought a VAC CPA-1 Mk II full function preamp and that was not a mistake.  One of the features I really appreciate about the VAC electronics is the ability to reconfigure the gain, phono loading of the pre and output tube type, mode of operation, and feedback of the amps.  Two levels of gain plus buffered passive of the line section, phono section offers three levels of gain (to include use of LOMC carts) plus five R loading selections and six C choices.  The amps can use any tube in the 6L6 family from 5881 through the KT88 plus selectable modes of triode, ultralinear, and pentode.  Six levels of feedback are selectable and vary slightly based on operational mode selected.

Concerning VAC and Kevin Carter.  I was under the impression the Kevin Hayes (VAC owner) did all his own designs but it would seem I am mistaken.  Can you please enlighten me some more in this area, Anand?  How have you discovered the differences in these designs and what the designer did right and what they did wrong?  Are you able to read the schematics well enough to understand how the circuit works and make decisions based on what you perceive?  I ask these questions to learn my own folly in choosing amps and kits because I am almost ready to step into the world of high efficiency speakers and SET amplification.  I made the mistake of spending way too much money on the Dyna rebuilds only to find a production product that makes mincemeat of them sonically and don't want to go down that path again.  History does have a tendency to repeat itself but if we actually learn from our mistakes it doesn't have to.

Thanks,
Jake

[JohnR]

I've never been particularly impressed with the Dynas SQ and I wish there was something I could do to fix them but honestly I should probably just sell them and move on.

I think I might try putting EL34s into mine. They have the dual bias kit from triode electronics in them so can be biased for the 34's. I really should get to it and see what happens. Having said that, I don't like monoblocks  anyway and the fiddly connections and all says I should move on too. Really just trying to think of something interesting to do with them

[JakeJ]

What don't you like about monoblock amps? I always thought they were considered the ultimate in channel separation.  What "fiddly connections" are you referring to?  In the case of my Curcio kits the octal socket that was originally there for the old PAM mono preamp is intentionally left off and the positive lead for the a meter used to bias the amps is connected to a post on the power supply board mounted inside the chassis.  It's a PITA to use and I usually left a mini hook test lead connected even though the bias holds very solid.  I always thought that was kinda cheesy.

However design and implementation of the driver section is likely the culprit for the poor SQ of the amp now.

[JohnR]

I dunno... monoblocks for stereo just annoy me. These were just "amplifiers" back in the days of mono

Mine are mostly original on the outside, so fiddly means the wimpy RCA input, the screw terminals for speakers, the need to remember which hole in the socket is for the bias measurement.

[JoshK]

Back to the OT, I share similar biases with Anand.  His audio journey parrallels mine in many ways.  Having said that, I am not familiar with Joe Curcio or his designs.

I took a look at that schematic for the Sarah.  I am not impressed with the employment of series regulators.  This is a perfect example where shunt regulators would serve so much better.  Allen Wright, Lynn Olson/Gary Pimm, Kevin Carter all use CCS loaded shunt regulators and have written why they feel they are superior.  Broskie has written many times why he doesn't like series regulators (they add their own sound) and why he now just uses shunt. 

Series regulation is pretty old skool.  Other than that, the actually RIAA circuit topology looks half-way decent at first blush.  I didn't go through the time constant calculations though. 

I've glanced at the bottlehead phono circuit and it seems like their maxxed out version is a pretty decent circuit (w/ C4S).  I think Kevin's standard phono looks pretty awesome as well. 

I am about to resume work on the Gary Pimm's phono stage.  This one isn't a kit and not really for beginners. 

[etcarroll]

Thanks Josh. 

[WGH]

I have Bottlehead on my shortlist already, not sure how to equate the other names to product.

If you are looking at DIY tube phono pre-amps then the a Hagerman Cornet2 should be on your short list. I built one to compare to the Bottlehead Seduction with C4S and there was no comparison, the Cornet2 has more of everything - tonality, inner detail, imaging, bass definition, and clearer highs. I immediately sold the Seduction to an AC member who then re-sold it a few months later.

The Hagtech Circle has a lot of Cornet2 building tips, I recommend the Mondorf SIO caps bypassed with Russion FT3's.

My old Seduction



The Cornet2 with Russian FT-3 bypass caps


Wayne

[JakeJ]

Thanks, JohnR.  Hmm...I've always liked the idea of monoblock amps both for aesthetic and sonic purposes.  Understood on the "fiddly", now, I used to have a pair of the Mark IV monoblocks and they were all original too.  Couldn't stand the screw terminal strips and don't like them on any of my vintage amps but I'm not willing to change them and chance lower their value.

Thanks to you too, Josh, for explaining what some of the "errors" are in the Sarah.  I also checked out the schematics.  I am guessing the series regulators are IC1-4 in the power supply schematic?  I'm not real certain but the voltage regulators on the signal board schematic look to be simply regulating voltage to the tube plates, is that correct?

I need to go for my morning walk so I'll be back in half an hour or so.

Thanks,
Jake

[JoshK]

I am guessing the series regulators are IC1-4 in the power supply schematic?  I'm not real certain but the voltage regulators on the signal board schematic look to be simply regulating voltage to the tube plates, is that correct?

No, the series regulators are IC151 + Q151 & IC152 + Q152.  The ICs being the error amps and the Q's are the pass device.  Note how the Qs are in series with the plate of the tubes not in parrallel as they would be in shunt (B+ to ground). 

Actually upon reviewing the power schematic, it does appear that there is also a series regulator IC1 and IC2 controls the V- voltage.  A bit weird from my eyes. 

The IC3-4 are for heater regulation (series also).  Although that is normal for heaters.

[poseidonsvoice]

No, the series regulators are IC151 + Q151 & IC152 + Q152.  The ICs being the error amps and the Q's are the pass device.  Note how the Qs are in series with the plate of the tubes not in parrallel as they would be in shunt (B+ to ground). 

Actually upon reviewing the power schematic, it does appear that there is also a series regulator IC1 and IC2 controls the V- voltage.  A bit weird from my eyes. 

The IC3-4 are for heater regulation (series also).  Although that is normal for heaters.

I looked and have seen this schematic multiple times over the years (it's about 10 years old), and I am in agreement with Josh on all accounts.

Here is information I needed about five years ago when I rebuilt my Dyna Mk III monoblocks.  I now have a pair of VAC PA-160 monoblocks that just blow the Dynas away in terms sound quality, and I paid less for the VAC amps than I have into the Dynas.  I've never been particularly impressed with the Dynas SQ and I wish there was something I could do to fix them but honestly I should probably just sell them and move on.

I was so impressed with the VAC amps that I sold my highly modded McCormack ALD-1 preamp and bought a VAC CPA-1 Mk II full function preamp and that was not a mistake.  One of the features I really appreciate about the VAC electronics is the ability to reconfigure the gain, phono loading of the pre and output tube type, mode of operation, and feedback of the amps.  Two levels of gain plus buffered passive of the line section, phono section offers three levels of gain (to include use of LOMC carts) plus five R loading selections and six C choices.  The amps can use any tube in the 6L6 family from 5881 through the KT88 plus selectable modes of triode, ultralinear, and pentode.  Six levels of feedback are selectable and vary slightly based on operational mode selected.

Concerning VAC and Kevin Carter.  I was under the impression the Kevin Hayes (VAC owner) did all his own designs but it would seem I am mistaken.  Can you please enlighten me some more in this area, Anand?  How have you discovered the differences in these designs and what the designer did right and what they did wrong?  Are you able to read the schematics well enough to understand how the circuit works and make decisions based on what you perceive?  I ask these questions to learn my own folly in choosing amps and kits because I am almost ready to step into the world of high efficiency speakers and SET amplification.  I made the mistake of spending way too much money on the Dyna rebuilds only to find a production product that makes mincemeat of them sonically and don't want to go down that path again.  History does have a tendency to repeat itself but if we actually learn from our mistakes it doesn't have to.

Thanks,
Jake

Jake, I will contact Kevin Carter about his actual role. Remember he was an employee so he learned quite a bit I am sure. But his entire world of differential/balanced push pull designs stemmed from VAC imho. Currently one of his favourite amps is a gargantuan GM70 SET (gasp!) that he is even shocked by as it isn't push pull. Lots of money in it though. Its nice that he embraces both types of topologies and I think its because he has optimized each design.

I wouldn't say that I am as well versed as the bonafide tube designers I mentioned earlier in inferring info from schematics. It comes after building quite a few designs and unfortunately your own biases can work against you. That being said I have my opinions which I detailed somewhat in the next paragraph. The biggest conclusion I want people to get is not to become an armchair audiophile. Build, listen, measure, build, listen, measure, and repeat. Then you start to realize that some topologies YOU like and others you dislike and in some cases...despise. You will also realize that there are those that claim they reinvented the wheel when in fact its the same old williamson, concertina splitter, Schmitt/long tail pair, etc...

Jim Hagerman also makes quality stuff, I'm just not as keen with the topologies I have played with using the 12AX7, 12AT7 or 12AU7 in the past, although I definitely see their applicability (notably the 12AX7 and 12AT7) in phono stages. Still, you can design without them. The designer sometimes is forced to choose these tubes not for their sonic qualities but for marketability so keep that in mind. Ask him to use a different set of tubes and suddenly you might get a better design as the tubes' spectral harmonic distortion is considerably better.

I'll tell you one thing that nobody has mentioned yet. And that is the achilles heel of amplifier design. Besides the output transformer, your driver stage has to be well designed. Basically what you will see with the state of the art amp designs that are differential is that the driver stage is almost like a small power amplifier. For example Kevin Carter's top of the line KT88 amp (he has a lot of top of the line designs you just choose the tube), he uses an interstage coupled 6BX7 driver stage, an octal tube with very low distortion but can swing oodles of volts and easily provide more than 6dB of headroom. You will always hear the driver stage in any amp design. If you could drive a 45 with 45 and still have a substantial amount of gain you would see everybody doing it. Lynn Olson does it with his Karna amp, but he had to make it a 3 stage design since there is virtually no gain in the 45 in that application. 

I hate it when I see a 12AX7 driving an 845. It makes no sense whatsoever. The sucker can't even pump out more than 1mA of current so the 12AX7 will croak all the time. Make sure you watch out for this kind of stuff. Driver stage design is very, very important.

But we are getting off topic here, and unfortunately my input is limited as I don't play with vinyl much. It's just that I've heard Curcio's Dyna rebuilds and that phono stage and it was ho hum in my mind. And his dac is ancient with a tremendous lack of detail (non-oversampling TDA1541 unit with tubes in the output stage).

Just one man's opinion.

Anand.

[WGH]

Jim Hagerman also makes quality stuff, I'm just not as keen with the topologies I have played with using the 12AX7, 12AT7 or 12AU7 in the past, although I definitely see their applicability (notably the 12AX7 and 12AT7) in phono stages. Still, you can design without them. The designer sometimes is forced to choose these tubes not for their sonic qualities but for marketability so keep that in mind. Ask him to use a different set of tubes and suddenly you might get a better design as the tubes' spectral harmonic distortion is considerably better.

There is also an octal version of the Cornet2 that uses 6SN7 tubes, some say it sounds better. An octal search on the Hagerman Circle will yield four pages of posts.
www.hagtech.com/pdf/cornetoctal.pdf

Wayne

[poseidonsvoice]

There is also an octal version of the Cornet2 that uses 6SN7 tubes, some say it sounds better. An octal search on the Hagerman Circle will yield four pages of posts.
www.hagtech.com/pdf/cornetoctal.pdf

Wayne

Slipped my mind. Thanks for that.

Concerning VAC and Kevin Carter.  I was under the impression the Kevin Hayes (VAC owner) did all his own designs but it would seem I am mistaken.  Can you please enlighten me some more in this area, Anand?
Thanks,
Jake

Kevin was involved in UPGRADES only to the Renaissance PP300B Mk III and he was also involved in only the linestage design of the Rennaissance Signature Preamplifier Mk II. He was the official Manager of Marketing and Operations.

There has been a considerable amount of misinformation set forth here on the internet regarding Kevin Carter's level of involvement with VAC design. The above statement serves to clarify, and correct those mistruths or exaggerations if you will, however innocent they may seem to be.


Anand.

[JakeJ]

Josh and Anand,

Thank you so much for taking the time to explain both circuit topology and the way a DIYer such as yourselves end up making the choices you do concerning designers and the circuits they produce.  I also appreciate the further explanation of Kevin Carter's actual involvement with VAC.

It's clear I still have much to learn and need to review the thread in which I requested teaching materials, procure said materials, and further my knowledge.  I haven't put much effort in it and I need to make it more of a priority.  Keeps my "dart throwing" to a minimum.

Best Regards,
Jake

[etcarroll]

Well, the Sarah is no longer available per designer.

So it looks like Cornet vs. Aikido phono preamp.

[WGH]

So it looks like Cornet vs. Aikido phono preamp.

Have you read about the mods tubesforever did to his Cornet2? Adding the FT-3 caps to my C2 came from his writings.

"The C2 created quite a stir during my trips.  No one thought this Hagerman could stand up to a Lamb or Thor.  No problem at all actually.  The C2 surpassed both by a comfortable margin.  The bottom line is that my slightly modified C2 beat out some big names out there."
http://www.audiocircle.com/index.php?topic=58941.msg523190#msg523190

Wayne