Transcendent Grounded Grid Preamp Questions. UPDATE: Now Modification Thread

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Ray Bronk

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Now that I am getting VERY close to that "straight wire with gain" thing, with a two-tube-stage preamp no less, I made some further mods to get it even closer.  The tedious process of comparing a new mod vs. no preamp in the chain continued endlessly. 

In the end, I ended up adding FT-1 Russian teflon caps to the large VCap teflon output caps.  It's kind of counter-intuitive, but even a great cap like VCap can benefit from a small teflon bypass as the cap size increases. 

Where small teflon caps seem to really thrive is bypassing power supply electrolytics, and I added some more FT-1 teflon caps to various PS electrolytics. 

These changes ended up giving me that last 3% of extreme treble air, extension, and coherent sweetness.  I'm still surprised when improving the high frequency seems to enhance bass definition, but that happened as well once again :)



Well, you're not quite done yet lol. I believe it's the filament cap that is only a 25V and is 1000 mf? Double the value, keeping the cap's voltage the same. Will be interested in your findings.

Ray Bronk

Manolo

Re: Shunt Attenuator mod question for Rick Schultz...
« Reply #21 on: 14 Apr 2010, 07:56 pm »
Could I implement the shunt attenuator mod in an Alps volume control in my Supratek Preamp? Or this mod would require discrete resistors?

I remember that in a Reference Line preamplifier I had, it originally had an Alps volume control. Wasn''t this a shunt application?

Thanks! 

natemil


In the end, I ended up adding FT-1 Russian teflon caps to the large VCap teflon output caps.  It's kind of counter-intuitive, but even a great cap like VCap can benefit from a small teflon bypass as the cap size increases. 

Where small teflon caps seem to really thrive is bypassing power supply electrolytics, and I added some more FT-1 teflon caps to various PS electrolytics. 


Hi Jon, What voltage rating and uF were these FT-1s?  thanks, Doug

Steve

Quote from: Jon L
I have been playing with the GG, and while I was happy it already had the Goldpoint stepped attenuator, Grayhill switch, Auricap upgrade, and solid core silver wire in teflon, it still sounded like I inserted a tube preamp into my system and what that implies    :(

Before GG fans get upset, do understand that my previous system did NOT even use a preamp.  I was able to tweak the gain stages and my audio PC's digital signal output to do fine without a preamp.  When I got the GG, I simply placed it in my system, so the setup now had one more active component and another run of (same) interconnects.  And yes, I could hear them..

What was most bothersome was what I perceived as fuzzy bloom overlaying everything and slightly "puffy" bass and loss of absolute transparency of resolution, especially in the upper-midrange.  I am sure someone replacing a less-well-engineered preamp with GG would be delighted by it, but I'm comparing it to the proverbial "no preamp."

Luckily, a lot of the character I heard, I recognized from my capacitor-rolling experience with Auricaps.  I then replaced the Auricap output caps (which was already an upgrade from stock caps) with VH Audio Teflon capacitors of the same value. 

Color me impressed!  Fuzz turned into resolution,......

Yep Jon, Auricaps have problems with accuracy in absolute terms.

General comment: Shunt volume controls have a varying input impedance (Z). This presents little if any problems with DC output coupled circuits, but will with AC output coupled circuits (capacitor/transformer coupled circuits).

Another idea is to bypass the analog gain/mute sections in the cdp. You only lose approximately times 2 gain (6db) while improving the sound quality.

Cheers.

Ray Bronk

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Re: Shunt Attenuator mod question for Rick Schultz...
« Reply #24 on: 21 Dec 2010, 04:27 pm »
Could I implement the shunt attenuator mod in an Alps volume control in my Supratek Preamp? Or this mod would require discrete resistors?

I remember that in a Reference Line preamplifier I had, it originally had an Alps volume control. Wasn''t this a shunt application?
 
Thanks!

You should be able to do that with not much effort.

Ray

doorman

Check out opticoupler volume control for your GG pre.
It's transparency is evident. It makes a fine pre VERY fine!
Best, Don

Jon L

Check out opticoupler volume control for your GG pre.
It's transparency is evident. It makes a fine pre VERY fine!
Best, Don

Which opto-coupler did you use?  I do have a LDR passive (Eva), and yes its transparency is awesome, but the volume control's increments are not fine enough for my needs.  Granted, I run high-ish sensitivity system (96 dB sensitive). 

pelliott321

I got the WarpSpeed and its unbelievable.  It uses a multiturn precision pot and works great. shuts the music down completely and I have almost a full turn to control the volume.  I have tried alone and in the dodd buffer but not the GG.   

JLM

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Any updates Jon?

pelliott321

I just rewired the volume pot in my TS GG pramp from stock series, to shunt, effectively removing the pot from the signal path. The preamp does sound very different(still evaluating).
It seems so very obvious to do this mod, I have to question why would any body design a preamp any other way?
What is the possible downside?
Why would anyone ever bother with expensive discrete resistor attenuators?
What am I missing?
So it goes.........

Steve

I just rewired the volume pot in my TS GG pramp from stock series, to shunt, effectively removing the pot from the signal path. The preamp does sound very different(still evaluating).
It seems so very obvious to do this mod, I have to question why would any body design a preamp any other way?
What is the possible downside?
Why would anyone ever bother with expensive discrete resistor attenuators?
What am I missing?
So it goes.........

See post #23 for why not. One can find accurate pots on the market. But again, the problem is the varying impedances that passives inherently have, both shunt and series types, and the IC's output capacitance interaction problem. One has to impliment it in the integrated amp itself to minimize the problems.

Also, one is leaving out the following active gainstage and it's problems, which can vary wildly from integrated amp to integrated amp.

But superior pots, without ICs on the output, in typical internal chassis applications, can provide a near if not perfect signal.

Cheers.
« Last Edit: 21 Dec 2011, 12:51 pm by Steve »

doorman

Which opto-coupler did you use?  I do have a LDR passive (Eva), and yes its transparency is awesome, but the volume control's increments are not fine enough for my needs.  Granted, I run high-ish sensitivity system (96 dB sensitive).
Mine uses Silonex optocouplers, both for volume & balance, (which was also added)
best
don

Ray Bronk

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Re: Transcendent Grounded Grid Preamp Questions
« Reply #32 on: 2 Jul 2012, 06:47 am »
Jon,
If you want it to sing....you need to do the following:

bypass all the switching and the volume control.....simply wire a 10K resistor from one of the input jacks to the grid of the first tube....and from the same spot run a wire to the pot which will just be used as a shunt to ground.  Super way better sound.

Change the rectifying diodes to some IXYS soft recovery types. 

Bypass the power supply with serious caps.

Remove the fuse.

Damp the tubes.

Change those output caps.  The one I had here had Axion 1uf caps....film and foil polyprops....not bad...did not try any others.

Use two of them dual mono.  The last tube shares both channels....this is a no no in my book.  I did not listen dual mono.....even one with the above mods was pretty killer.  Certainly, with mods,  the best preamp for the money I have ever heard.....stock it is OK at best......

Ric

Hi Rick,

Ok, a couple of questions.:

1. "the rectifying diodes to some IXYS soft recovery" What do you suggest there? Can you give me values ETC. I think there are four of them to change out? What do you perceive better as a result?

2. No question, but statement. Ok, I can see a very! temporary removal of the fuse to see what sonics would be gained there.
3. "Use two of them dual mono. The last tube shares both channels....this is a no no in my book.  I did not listen dual mono" Could you explain how to get two separate caps to work in this dual mono config? To bad there isn't a way of neutralizing that 75V to ground so a cap wouldn't be needed.

Ray

Ric Schultz

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Jon,
I hope you have done more to your GG.  It deserves it....you deserve it.  Please remove the fuse or use an audiophile fuse (whatever makes you comfortable) for much better sound.  Please remove the LED for much bettter sound.  Get rid of the power switch.  Please try dual mono.  Having completely separate power supplies for each channel and having only one channel in the last tube will bring much to the table.  4 pole electrolytics in the power supplies and bypasses on every one would be cool (or all film caps in the power supply).  The heater supply needs to be tweaked too.  All film caps need to be run so their outside foil is to the output or ground.  All caps need to be run so they are not vibrating (never dangling in the air on solid core leads). The WA quantum chips will make the electrolytics sound way better.....Better diodes....tube dampers....there is much you can do.  By having two chassis and dual mono you can also go balanced too.   Balanced GG would be killer.  You could run totally tweaked balanced bridged F5 mono amps and you would die from happiness.  I am going to get two GGs and do all this myself......dual mono balanced.
« Last Edit: 21 Apr 2013, 08:02 pm by Ric Schultz »