Dynaco upgrades - lets talk audio and DIY

[anarchist]

Anyone here do any upgrading of their dynaco's themselves using the SDS Labs cap boards and/or the various driver boards available? There is a "Poseidon" driver board I have seen using a 12ax7 and 12au7 (similar to another well received amplifier we are familiar with) which seems to be getting rave reviews. I have read more than a few posts saying with capacitance increased to 630 volts and a poseidon driver board utilizing a 5751 and 12bh7 as your tube choices, you can't do much better than a modded Mark III.

Anyone have any experience with these products or others? I know fini is familiar with the poseidon boards but haven't seen any info on this board.

[Guest David H]

I have the VTA MOD Dynaco ST70, and a freind of mine has the MK3's also VTA, as far as I am concerned it is the best Dynaco upgrade ever, and it doesnt take a rocket scientist to install. check it out at www.tubesforhifi.com Dynaco tube amps and Klipsch are made to be together.

[Bill Hausmann]

I have previously used the SDS (Sheldon) Cap board for a 70 that I had and it did WONDERS for it!! It was like 30-40 bucks when I bought it and worth every cent! I went an alternate route for the driver like bringing all the parts back to spec. [8-|]

[scott0527]

I installed two of those SDS cap boards over the years. I never like they way they fit so tight. Seemed like I was stuffing the thing in there hoping it wouldn't bust loose after everything was put back together. I'd second the www.tubes4hifi.com website for the best upgrade driver board. Craig NOSValves uses a version of this board although he tweaks it further.

[NOSValves]

I installed two of those SDS cap boards over the years. I never like they way they fit so tight. Seemed like I was stuffing the thing in there hoping it wouldn't bust loose after everything was put back together. I'd second the www.tubes4hifi.com website for the best upgrade driver board. Craig NOSValves uses a version of this board although he tweaks it further.

Yup and the voltages in the Stereo 70 are of no danger to the original 525V twist lock type cans readily available from AES and other parts dealer. So in the case of the Stereo 70 there is no advantage to the cap board. In fact I don't think they have any real upgrade value in them for the Mark III from a performance standpoint (only voltage) the size limitations force you to use sub minature caps that are really not designed for the ripple current present in tube audio. I have no less the 4 or 5 cap boards that I have removed from Mark III's and stereo 70's. I'm all for upgrading the filter size in the power supplies but I have figured out better ways to accomplish it even in the Mark III. The cap boards were all designed when twist locks were not available years back. The resurgence of vintage tube audio prodded some companies to offer the real deal.

I have one of Shannon's (real nice guy) ST70 front end boards here but just have had no time to play with it yet. The Posiden? is just the ST70 board cut in half and slightly modified for the Mark III. I'm sure it can be made to work real well I'd be surprised looking over the schematic if I would leave it as designed though. I just can not see how one can get really great performance out of a 60 watt amplifier using KT88's with .1uf main coupling cap value's. I suspect the design is really tuned with a stock power supply filter bank in mind. In fact that is fairly obvious to me since Shannon has stated that he see's no point in upgrading the power supply filtering. But you know how it goes in audio everyone has an opinion and no one is absolutely right. Besides I have yet to try the design so I'm really just thinking out loud here. But regardless it absolutely looks to have potencial I even would venture to say it might be better then the stock configuration from tube4hifi.

By the way while it may use a similar tube compliment it is not the same as the amp that was mentioned in a veiled fashion by the original poster in fact not really even similar.

[anarchist]

I'd second the www.tubes4hifi.com website for the best upgrade driver board. Craig NOSValves uses a version of this board although he tweaks it further.

I was not aware of this - my understanding was Craig and Mark worked together and designed the VRD driver board. I seem to remember it was voiced with an ear towards Klipsch speakers or that may have just been certain opinions. Craig?

(SDS Boards) In fact I don't think they have any real upgrade value in them for the Mark III from a performance standpoint (only voltage) the size limitations force you to use sub minature caps that are really not designed for the ripple current present in tube audio. I'm all for upgrading the filter size in the power supplies but I have figured out better ways to accomplish it even in the Mark III.

Hey, that was a mouthful and I am certain it includes some great information if you can explain it a bit? The design flaw in the Mark III was the 525 volt cap. You have a workaround for that deisgn flaw which enables the long-term use. Ok. I don't understand how voltage, ripple current, and filter size are related? You see things tossed about - larger power supply (enables more bass yada yada yada) - which appears to mean larger or more capacitors and hence voltage. I guess that is the correlation here. How does that differ from "only voltage", ripple current, and filter size? What is "filter" anyway and what does it do?

The Posiden? is just the ST70 board cut in half and slightly modified for the Mark III. I'm sure it can be made to work real well I'd be surprised looking over the schematic if I would leave it as designed though. I just can not see how one can get really great performance out of a 60 watt amplifier using KT88's with .1uf main coupling cap value's. I suspect the design is really tuned with a stock power supply filter bank in mind. But regardless it absolutely looks to have potencial I even would venture to say it might be better then the stock configuration from tube4hifi.

More good stuff and more loss of understanding on my part. ".1uf couple caps"? What do they do and could you not just bump up their values? I guess some other thing would have to be reduced - resistor? There is that power supply filter bank again... hopefully, you can explain it so I know what we are really talking about.

By the way while it may use a similar tube compliment it is not the same as the amp that was mentioned in a veiled fashion by the original poster in fact not really even similar.

I am confused but since there seems to be a misunderstanding and you used "veiled" as if I committed some offense; let me clarify my statement and ask for clarification. I understood the VRD's to use a 12ax7 and a 12au7. The poseidon uses a 12ax7 and a 12 au7. Therefore, I stated "There is a 'Poseidon' driver board I have seen using a 12ax7 and 12au7

(similar to another well received amplifier we are familiar with)", I did not claim they were the same. I am not sure what you found objectionable here? The poseidon came out in 2006 so you can't think anyone would think the VRD's used the same board.

By the way, as a demonstration of my dementia and thought processes; Poseidon immediately brings images of water to my mind. Given that, if you named your product such, wouldn't you make the board blue instead of ruby red? What does red have to do with poseidon. It is almost like creating a product called "Apple" and making the only color choice white.

[scott0527]

I'd second the www.tubes4hifi.com website for the best upgrade driver board. Craig NOSValves uses a version of this board although he tweaks it further.

I was not aware of this - my understanding was Craig and Mark worked together and designed the VRD driver board. I seem to remember it was voiced with an ear towards Klipsch speakers or that may have just been certain opinions. Craig?

Until Craig rolls out of bed, let me just say I was talking about the ST70 only and should add that on my two ST70's, Craig used a version of the tubes4hifi boards that he tweaked/upgraded. I don't know what he uses on the MKIII's or anybody elses ST70's.

[3dzapper]

I was duly unimpressed with the quality of the tubes4hifi boards for the Mark III when I built my 6550 amps. I wound up taking them out and using "new version" boards from Triode Electronics. They allow the use of different drivers by changing out a few components. I stuck with the original 12AT7/12AT7 configuration substituting a 12BH7 in the splitter slot. Since I was just using the transformers from the Dynaco, I was able to build a much larger and stiffer power supply within my 10 x 12" mono bloc chassis.

The amps rock! Butt kickin' bass up through the highs. There is an over abundance of power for Klipschorns in either the Ultralinear or triode strapped mode.

I've never heard Craig's amps, but he says he has a better output transformer wound specially for his amps. His customers seem happy. (smile)

Rick

[fini]

Robert,

Just because I own a pair of Poseidon boards doesn't mean I'm "familiar" with them! ;^)

Shannon Parks is a real nice guy. Here's his website. I'll be following this thread with interest, as I still need to plow into the various Dyna products I have here. My problem? An inability to decide which route to take. Can caps are back in fashion? Uh oh...

[fini]

I just love these forum upgrades. Now I can't even separate text into paragraphs (without going through an HTML dance, I'd guess).

[whamo]

Ok has anyone tried the Mapletree audio octal driver board? I emailed Loyd and all he had to say was that it improved bass response. I've yet to take the plunge it's $200. Mark

[NOSValves]

Anyone here do any upgrading of their dynaco's themselves using the SDS Labs cap boards and/or the various driver boards available?

=====================

I have not used the SDS board, but I looked at the web site. The blank board can be fitted with a 25mm x 25mm snap lock capacitor. This is an industry standard format for electrolytic caps and as such allows for tremendous variety in the selection of caps. There are many makers of these caps including Cornell, United Chemicon, Nichicon, Mallory Vishay and so on.

I looked up a quick example for you. A Cornell part #381LX121M350J012. This is 120uF and 350V with a 105C rating that can handle a whopping 800ma of ripple current at 120Hz at 105C. This is far, far more ripple current handling capacity that you will ever need in any Dynaco tube amplifier ever made. This cap is 25mm x 25mm exactly as called for by the SDS board. And, the cap will never see 105C in a MKIII. So, a pair of these in series is 60uF @ 700V. This is just one of many examples of caps you could use. There is an excellent series of caps made by United ChemiCon in the KMH line also. There are many others with higher and lower ratings, but that one gives you an idea of what can be done. Also, the SDS folk say that 25mm Height is the max you can use, but I am not sure if that means with covers or without, so there is even the possibility you can use taller caps like 40mm height, which will give you even more choice. Just a quick note on cap choice - the cheaper brands with less current handling will pack more "microfarads" into a given size than the better caps. So, if you see a 25mm x 25mm that is 470uF@300V and another one that is 220uF @300V, it's a good bet the current and temperature ratings are different.

Good luck!

Absolutely you end up with some good quality caps using that method. But you also end up with a whopping 60uF on the center tap of the output transformer. To me that is not nearly enough to take advantage of the performance the transformer is capable of providing. To get above this value you have to step down to the sub minature series that do not have the same ripple specs or quality construction.

So in the end what avenue you want to take depends on the end result your after. If your just wanting a slight upgrade from stock while solving the high voltage flaw of the original Mark III design then absolutely the cap board is a great option.

Like anything audio trade off abound. The best course of action is to first set your goals.

Craig

EDIT

Oh I was interupted here by a local customer and completely forget to mention all the above indeed is in reference to fitting under the original bottom cover in a neat manor.

[NOSValves]

Ok has anyone tried the Mapletree audio octal driver board? I emailed Loyd and all he had to say was that it improved bass response. I've yet to take the plunge it's $200. Mark

Another interesting option from an awesome guy!! I know Lloyd personally (over the phone) I helped prod him into many upgrade implementations on the Ultra 4A line of preamps back before the blueberry came out. I still love those little preamps.

As far as publicly giving away my methods of upgrading various products I'm sorry but I just can not give that type of information away openly. Sorry way to many competitors frequent these forums. I learned this the hard way long ago. My business it not centered around catering to the DIY crowd I don't sell parts and kits. I don't mind helping but I have to stop at some point to protect the time and money I've invested. Hope you all understand.

Craig

[Deang]

You have competitors?

[whamo]

Craig, yeah I,ve got a 4a se I love it.

[NOSValves]

Craig, yeah I,ve got a 4a se I love it.

Do you have the Tube rectified seperate power supply version or SS? I originally bought the basic 4A he produced and honestly was completely unimpressed it was noisy and just uninvolving. I went in hacked away making all kinds of changes. I called him and much to my surprise he was absolutely open to every single suggestion I made that is not common with engineers. Later I told him I would like a tube rectified power supply with a choke and he made me up a kit to match my original control unit. So in effect I thought the 4A SE should of been name the 4A nosvalves [] Not really but regardless he is a great person to deal with.

[Audio Flynn]

Craig, yeah I,ve got a 4a se I love it.

Do you have the Tube rectified seperate power supply version or SS? I originally bought the basic 4A he produced and honestly was completely unimpressed it was noisy and just uninvolving. I went in hacked away making all kinds of changes. I called him and much to my surprise he was absolutely open to every single suggestion I made that is not common with engineers. Later I told him I would like a tube rectified power supply with a choke and he made me up a kit to match my original control unit. So in effect I thought the 4A SE should of been name the 4A nosvalves [] Not really but regardless he is a great person to deal with.

It had a nice sound. Itsounded much better than my vintage AMPEX preamp before the NOS VALVES improvements[]

.

[whamo]

Yes, I have the tube rectifier it's an 6x5 tube. Another thing I like is that you can change the voltages from 6vdc to 12vdc and switch tubes out. Like right now I've got 6sn7's in there but with the flick of the switch I can put 12sn7's in. Also there's a simple mod on the Mapletree audio site where you can use 12ax7's which I'm gonna try as well since I have a mess of those lying around. Fun! Mark

[anarchist]

Thanks for the info so far. Let me ask a couple questions to the electrical and engineering gurus in the crowd. I don't know what lots of this stuff means so any clarifications of my thoughts or suppositions are welcome.

If you have the original can capacitor, are running a 5ar4 rectifier, and install an in-rush current limiter (wherever and however), this is supposed to stop the overload on the can and get you voltage of 470 or so. II don't know what this provides to the rectifier tube though nor do I know what it offers in terms of "ripple current." Solves the problem but will it provide the same or better sound than...

Install an SDS cap board which will allow you to provide 60u to the rectifier tube which is its max and allows you to provide voltage from 630 to 800 volts depending on configuration and provides tons of "ripple current" whatever that is.

What does this voltage do and what are the benefits of higher vs lower? What is and why do you want ripple current? Are there other considerations related to power supplies I shoudl be aware of? Is a power supply simply the transformer and capacitor bank which builds up the total voltage available? Is this capacitor bank what you are referring to when saying "filters"?

PS. I have recently read there are companies who will rebuild quad cans to the voltage you specify. Would it be a good thing to simply grab a couple old quad cans and have them rebuilt to 600 volts? Can it be done or is there some limit on the can itself which prevents that?

Thanks for taking the time and edumacating me. I am sure others are benefitted as well. In any case, whatever one does, it is nice to understand what the hell is going on behind the scenes and not be limited to understanding plugging a "magic box's" cord into a wall.

[3dzapper]

http://www.freewebs.com/valvewizard1/smoothing.html