Hot-Rodded ST-70 Kit (Tubes4Hifi)

[joeriz]

I'm wondering if there may be some advantage to using actual sheilded wire vs. twisted pair.

I'm sure there are some that are more than willing to disagree with what I am going to say here but I highly recommend using shielded mic line for signal applications. I guess its the pro sound experience speaking out. I have built a number of line stages as well as amplifiers and at some point in time experienced hum issues. My experience is that mic line works good for me.

Thanks. Any idea where one can buy this in less than mega-quantities? I've always wanted to try mic line but can never seem to find it in less than 100 or 250 ft. rolls...

Joe

[burnedfingers]

Thanks. Any idea where one can buy this in less than mega-quantities? I've always wanted to try mic line but can never seem to find it in less than 100 or 250 ft. rolls...

Drop me a line and I'll get you some.

My question to you is this > What quad cap were you comparing the under chassis cap board to ?

Bob, I always set up a proper comparison. The Cap was a New unit of the same values as the original. Sorry I do not support the cult following of the high dollar superior caps. My point is that the original Dynaco power supply design is flawed. The power supply is minimal at best even with your Authenticap. Never had a Dynaco Stereo 70 go above 500VDC with a 5AR4 rectifier upon turn on. I use diodes in series with the 5AR4 with the diodes rectifying and the 5AR4 to slowly bring up the power supply. I would assume that you might be correct if one used diodes in place of the 5AR4. The diodes would also warrent the use of the first stage cap being 80mfd which would exceed the rating of the 5AR4.


Personally when I build a power supply board I exceed a 550 rating and its unfair to assume that anyone buying the power supply board would not make the assumption that if diodes were used then thought should be given to proper cap ratings and I believe that there are options with respect to both cap size and ratings that you failed to mention or consider.

As to my statement I would gladly put a power supply board up against ANY quad cap because like you I haven't heard the difference. The power supply design makes the difference in ANY piece of equipment. Hell I've used motor caps which are supposed to be superior to a lot of caps and haven't heard the difference. Sorry, I will still put my money on the power supply board with the caps that I select on it against your high dollar profit making Authenticap.

[highflyin9]

Your build is excellent. I'm not putting it down by any means. I do feel that there is always room for improvement in anything and that is why I suggested the power supply board...

No offense taken at all, I appreciate the recommendations. I doubt I'll be changing anything for a while as I'm pretty happy with the sound at the moment, but anything's possible

I did actually find a comparo of the two boards on AudioKarma: http://www.audiokarma.org/forums/showth ... p?t=307160

I already find my particular build to be rather warm and bassy, it's surprising that the Dynamutt would be more-so. Do you share the opinions expressed by kirkleclaire about the Dynamutt board?

[burnedfingers]

Quote:
Do you share the opinions expressed by kirkleclaire about the Dynamutt board?

To each his own. No, I don't share the same opinions about the Dynamutt board.

[Geek]

Great comparisons!


I am a little confused though....

Earlier you said:

I would highly recommend the driver board, power supply and bias circuits available by Geek.

Followed later by:

Quote:
Do you share the opinions expressed by kirkleclaire about the Dynamutt board?

To each his own. No, I don't share the same opinions about the Dynamutt board.

And Kirk said:

....sounding great!

in his post at:
http://www.audiokarma.org/forums/showpo ... stcount=65

So, did you like it or not?

Cheers!

[burnedfingers]

If I read the article correctly kirkleclaire claimed the Dynamutts sound changed with tube rolling and with that I disagree 100%.

I feel the Dynamutt board is not affected like other boards are when tube rolling. I run an Aikido 6SN7/6SN7 linestage with the 70 driving a pair of custom Klipsch Cornwall clones. I can also setup the other two Cornwall clones with an Aikido 6SN7/6SN7 linestage and drive a different 70. My A/B switch is instant and requires no wiring delays and possibly a better and more accurate means to compare the 2) 70's.

I don't buy the idea that the Dynamutt is affected by tube rolling as I have tried it with 5691's and 5692's and received the same response as I would if I used something inferior.

The Dynamutt is by far the Best of any Dynaco driver boards on the market even surpassing the MApletree board that I am very fond of.

Soundsage difference between the VTA board and the Dynamutt board pardon me but I have to pill the bullshit cord on this one. The soundstage is not narrower on the Dynamutt board.

The ideal 70 to me is one with a Geek power supply board and Dynamutt driver board followed by individual bias capability. To be blunt everything else is junk.

Sorry for not clarifying my views better.

[Geek]

Wow, thanks!

I thought you were being vague 'cause you hated it

(for anyone who does, please say so! It's how we as a group make better things )

Cheers!

[fiftyfivefilms]

Hi,
I am the author of the Dynamutt thread over at AK, just a couple of thoughts to clarify some of my postings.
Yes the Dynamutt is the best sounding board out there! Yeah Greg! I also used his power supply with individual bias and again its great. This is my daily player and it keeps getting better.

My initial comparisons with the VTA were made using a PAS-3 pre amp with the tubes 4hifi mod, while this works well with the VTA boarded 70 I felt it lacked when paired with the Dynamutt board, subsequently I rebuilt a Eico HF-85 and that pairing with the Dynamutt is beautiful.

I still have to disagree with 6bg6ga about the tube rolling, while subtle it exists, there is a reason some tubes cost a fortune and others cost a lot less…same with cars, a Chevy Vega has 4 wheels so does a BMW…But I can’t tell you the difference, I drive a Volvo.

In a search for adjectives I described the soundstage of the Dynamutt as Narrower maybe that doesn’t sum it up in words (sound being a subjective thing) but I also stated the VTA board was more like the sound of Tele’s and likening the Dynamutt as that of Mullards… they are different but how do you put that into words?. The VTA is clear, concise and a bit cold…the Dynamutt is a more balls to the walls punchy and warm. I like it like that.
Cheers,
Kirk
6bg6ga, I'm curious about your Maple Tree? I still have a third Stereo 70 to rebuild and want to try a different board but $260 seems a bit high? did you think it was worth it?

[rmyauck]

fiftyfivefilms that schem is out on the net and It's an LTP design too, but with no CCS. I think it used a 6sj7 then 6sl7 and finally EL34. I don't think 6SJ7 is in production so I wasn't really interested in it at the time.

Greg's (Geek) is similar using the Octal tube board except he has added CCS. He has a version in schematic form on his site with a 12BH7 added in I think as the latest version of his research on the ultimate ST-70 boards as of a few months ago when I last looked!

[Geek]

Why, thank you gents! *bows humbly*

Yes rmyauck, the one with the 12BH7's is known as "DynaMutt-II" and is a point-to-point mod only... there is just not enough PCB real estate to make a board for this.
http://geek.scorpiorising.ca/contrib/Ge ... utt-II.png

The universal consensus on this is run it pure pentode - triode and UL witht he anode follower is not as nice.

The only existing version is used as a reference amp at Planet10-HiFi.com. The original PA-060 has no problems with the extra load.

I am currently in the process of a hybrid DynaMutt for the SCA35, I call "MiniMutt"

Cheers!

[fiftyfivefilms]

Greg,
Any Idea on the time-line until the PAS-K boards will be available?.....???
cheers,
Kirk

[Geek]

They are! Sorta...

I have a set boards here, but the phono has a silkscreen "oops" (only silkscreen, no trace oops).

I've been selling them as a set of 3, phono, line and PAS regulator for $75 + shipping.

Docs:
http://www.classicvalve.ca/docs/PAS-K_m ... d_docs.pdf
http://www.classicvalve.ca/docs/PAS-K_p ... d_docs.pdf

Only one each line stage and phono are in stock with more on the way.

Cheers!

[burnedfingers]

quote:
I still have to disagree with 6bg6ga about the tube rolling, while subtle it exists, there is a reason some tubes cost a fortune and others cost a lot less…same with cars, a Chevy Vega has 4 wheels so does a BMW…But I can’t tell you the difference, I drive a Volvo.

Well, I have a supercharged Z-28 Camaro. Who gives a sh**?

My build may be superior to others in respect to the quality of parts used and this may have a bearing to the outcome/performance of the board and whether I heard a distinct difference in tube rolling. Quality parts and quality build in my opinion do have an effect. I have experienced tube rolling difference when cheaper parts were used in different circuits. Everything from the line stage, amp, and speakers must be figured into the equation. My system consists of an Aikido 6SN7/6SN7 circuit that used the Russian 1578 tubes that currently retail at $200 a pair. Thats $400 in tubes in the Aikido.

Like I mentioned before MY Dynamutt has used premium Red October 5692's and 5691 and I could tell no difference between them and run of the mill set of 6SN7's and 6SL7's but maybe this is due to the quatily of the parts I used and the design of the board. Its easy to trick your self into thinking that a $100 tube sounds better than a $20 tube. More money makes it better right?





Quote:
6bg6ga, I'm curious about your Maple Tree? I still have a third Stereo 70 to rebuild and want to try a different board but $260 seems a bit high? did you think it was worth it?

I built three hand made mapletree board clones after purchasing the original board from Lloyd and put them on all the 70's I had here at the time. This was before I purchased the Dynamutt. I consider the Dynamutt to be superior to everything on the market and the Mapletree to come in a close second. By the way I could hear a difference when tube rolling with this driver board. I experimented with different parts on the three boards that I built. I could still hear a slight difference but I attribute this to the circuit.

[MouseMaster]

Thanks Geek, I'm actually restoring a PAS at the moment and am using the same power supply that you used in your tutorial.

Here's a sneak peak:

I have Sal doing the final wiring and checkout this coming week and she'll be good to go :)

Hey now... I'm a noob here, starting today. I spotted the thread on this PAS this morning. That's what drew me over here. That is some nice work you're doing. I think I know the Sal you were referring to in that thread. I was in a radio club with him last year. I couldn't keep making the meetings bacause of work. Sal is a good guy.

[highflyin9]

Thanks Mouse, I'm trying to keep most of my builds aggregated on http://www.DIYAudioBlog.com if you'd like to take a look at some of the other stuff I'm working on. Sal is a very nice guy, he's on these forums as well.

Geek, I may have to try building that PAS line circuit. I'm sure it's excellent :)