Adcom GFP-750 Modfication Question

Has anyone had their Adcom GFP-750 preamp modified or heard one thats been modified by Stan Warren at Supermods in Eugene,Oregon?
If so, does it make a big improvement?If so, in what ways?
What all does he do to it? Or, am I better off keeping it stock from the factory?
SUrprisingly Id be interested in what mods he actually does. I cant believe he does any mods to the passive circuit which is almost perfect to begin with. DOes he mess with the active stage? Sound deaded? Whats he charge?Give some details. Website etc....
He supposedly works on the active stage.Changes the capacitors to Black Gates.How much he charges, I have no idea.I hope someone will tell me.I tried to call but there was no answer.You can call him at 1-541-344-3696.Best times are between 1:00 p.m and 4:00 pm Pacific Standard Time.If you find out anything,please post it or e-mail me.
Daltonlanny is correct: the only mod Stan Warren does is to the active stage, replacing the stock capacitors with Black Gates. The improvement is significant: it brings the active mode very close to the renowned quality of the passive mode. The cost was about $150. Stan thinks that the Nelson Pass design is excellent and in need of no further modification. I've just sold mine, since I bought a used Pass X2.5. The price for performance ratio of the Black Gate modified GFP-750 certainly beats that of the Pass, though I'm very pleased with the Pass, which is clearly better in absolute terms.
Hey Lmack,
What all sonic improvements, top-end, midrange, and bottom-end did you gain after you had your former Adcom gfp-750 modified by Stan Warren at Supermods with the Black Gate caps? How substantial were the improvements? Is it worth the trouble of packing it up, sending it out, and paying $150.00 in your opinion? Please describe the sonic improvements in detail.
Black Gate caps give a warm liquidy feel to the midrange from the research Ive done and heard. Downside is break-in time. The consensus is it takes about 500-1000 hours for break-in. $150 may be worth the price if you use the Active Stage. I never needed to when I owned this unit awhile back, I was always in passive mode using all xlr's. ANd as they say, the best pre-amp is no preamp, and the closest to no preamp is a simple passive resistor with minimal traces design of Nelson Pass.
Ritteri has succintly and accurately described the added "warm liquidity" to the midrange. Further, I heard less grain throughout, which resulted in a smoother, more relaxed presentation, especially top-end, with no loss of detail. While the Black Gates did take some time to break in, I started hearing obvious improvement within a week, and not much more improvement after two to three weeks--though I had my CD player running through it during much of this time, I would at least halve the break-in time Ritteri suggested to 250-500 hours. Yes, if I wasn't clear before: the $150, trouble, and wait was worth it. (Stan also did a great job handling the unit, leaving no external trace.) In my experience and for my listening preferences, there was "gain" and almost no loss in using the Black Gate active mode as compared to the renowned passive mode.
Michael Percy Audio sells Black Gates. If all you have to do is swap out cap's maybe you could do it yourself and not have to ship out the pre.
FWIW, I asked Adcom about swapping out components and they told me they use high quality components throughout and there was no need to upgrade anything.
Improvements are as described by Lmack and Ritteri. I would not recommend just swapping out the caps yourself since the values used by Stan are not exactly the same as used by the mfg. However, the improvements are noticible immediately and the unit will continue to improve. I almost always used it in active mode, which I believed provided more lifelike dynamics. The preamp was bettered overall (in my system) by a Muse Model 3 Signature. - Good luck.
A very important question: Is there any way the sonic performance of the active stage of the Adcom GFP-750 could be DOWNGRADED by having the caps changed to Black Gates, compared to stock? My system sort of sounds dark and warm to begin with.Would there be too much warmth and an even darker sound by going with the Black Gates? Is there any improvements to soundstaging, imaging, and/or image focus by going to Black Gates? What exactly happens to the top-end when going to the Black Gates? Does it stay the same, open up more, gain detail, or does it sort of darken and become more laid-back? Your detailed input would be greatly appreciated.
So I have this pre. Can anyone tell me the cap numbers (on the board)? Because I see my C23 - C25 -C27 are looking bad. But this is just the power supply. Not the audio stream. I can replace them, but not sure if this is the mod or not...
Musical Concepts still does an extensive mod on the 750. Check their website for info,they have been modifying Adcoms going on 30 years.