mods for Adcom GFP-750

Does anyone know of any DIY mods for this preamp? I'm also interested in possible mods for the GFA-5802 amp. Any suggestions? Thanks
I have The 750 preamp and loe it. Can't say I've wanted to mod it at all.... For the amp you might get some really top notch binding posts and replace the standard ones, ditto the RCA jacks. The RCA jacks in the preamp are direct to the circuit board (I think, don't know but guess) and would be harder for a do it yourselfer to swap. But if they are NOT straight in to the board Id get cardas female RCAs and put them in the back.
Better cords: Try some aftermarket AC cords.
Contact Stan Warren at (541)344-3696. He does mods the the Adcom 5802 which make it a giant killer. I have had Stan mod a Pioneer 525 DVD player and have bought his Single DACT passive pre-amp. Both units are incredible. Stan is also great to deal with.
I'd like to offer another point of view, and suggest that
your plan to modify the Adcom GTP-750, and maybe the 5802, is not well considered. I've been an audiophile for 40 some years, and have built my own gear from kits, and also done mod's (such as the DIY version of Musical Concepts mods for the Hafler 110 preamp and the 220 amp). I have yet to find a mod that is an improvement over the original product. Think about this: if a different circuit, power supply, etc., provided better sound and was cost effective, why didn't the manufacturer simply design it that way from the beginning? Mods are rarely cost effective -- a lot of money for minimal difference. Infact, I would almost suggest that mods are rarely better, simply different. If what you want is a different sound, then I recommend selling the preamp, amp, etc., that you have and buy something else. Finally, once you modify a unit you have effectively reduced its value to other potential buyers, and voided the manufacturer's warranty. My best intentioned advice here is to rethink mods to your Adcom gear. Both units have gotten very favorable reviews/ratings from several high-end audio mags, so I doubt you will improve on the sound by "modding" them.
As someone that makes their living by "modding" electronic components, i would COMPLETELY disagree with Sd's comments. Manufacturers build their products to meet specific specifications and price points. Keep in mind that adding one dollar to production costs equates to AT LEAST a 4 dollar increase in retail price and sometimes as much as 8 dollars. This means that they tend to use cheaper parts that will get the job done in order to keep the cost down as much as possible. As long as the unit will meet spec, survive the warranty period with minimal problems and draw in customers, that is pretty much all that they are worried about. Since most companies, especially those that produce "reasonably priced gear", think that wire is wire, resistors are resistors, caps are caps, etc... they use what they can get at the best prices with good reliability. On top of this, they tend to be conservative when it comes to really "fine tuning" the circuitry for best performance. Keeping the bias down reduces heat, power consumption, reduces production costs due to the need for less heat-sinking material, increases lifespan and reliability and helps them to easily surpass the warranty period. On top of that, they will tend to make use of larger amounts of negative feedback than what is really needed to get the job done. This is done because it makes the amp look better under test conditions and reduces distortion in terms of "paper specs". Since most of the people that are buying "affordable" gear are still quite "spec oriented", being able to print "pretty figures" is still quite important to manufacturers in terms of a marketing tool. They do this even though most all designers agree that negative feedback iin quantity is a BAD thing in terms of sonics. I could go on and on, but i think you get the point. Mods CAN be QUITE succesful if carefully thought out and well executed. If the basic circuitry was "as good as it gets", manufacturers would not be able to "upgrade" them and produce new models that DO perform better. "Tweaking" not only "fine tunes" the unit, it helps to advance the state of the art when done correctly. "Mass production" simply means "making as many units for the highest profit margin". It does not mean "quality" in most instances. Sean
If you really love the units and want to soup them up: mod.
If you want something better, buy something better!!!!
If you mod an item, not many buyers would pay anything extra for the mods in a sell off, and some would not consider buying a modded unit.
However to avoid the rush for some others to smash me into small tiny bits, I WOULD say that SOME mods are universally recognized as GREAT mods and are worth doing (Just none of those are for the Adcoms) AAeee fire raining down!!!!!
(I agree with sdcampbell, skip any major mods)
Sean: your points are fair, although I still believe, based on my own experience over a lengthy period, that major mods do not make good sense. The only mods I have ever heard that seemed worth the cost were the units from Audio by van Alstine. His "mods", however, are actually complete rebuilds using the chassis, power supplies, and maybe some of the internal circuitry. I personally think that any mod that costs more than 20% of the original purchase price is not cost effective, particularly if the owner plans to sell the unit at some future time.
Don't get me wrong, many mods are FOOLISH at best. Some are not cost effective and in many cases, actually degrade the performance of the unit. There there are the "cosmetic" upgrades, such as swapping one brand of gold plated copper binding posts for another brand of similar design but shaped differently, etc.. While "old golden ear" might be able to hear the difference between well designed components like these, i sure can't. Internal wiring and its routing is another story though. Things like this can make not only an audible difference, but also sometimes quite measurable differences. Sean
Sean and SDcampell, thanks for your inputs. Its good to get constructive opposing views on the same subject. I'm considering modifying my cd player, Sony SCD-777ES SACD. What is the prefered way to route internal wire and which internal wire works best (Cardas, Wonder, Harmonic, Silver)? Was wondering in order of bag for the buck which components are usually better to replace in the power supply and analogue output stage circuit? Capacitors (Black Gates), Resistors (Caddock or Vishay), or diodes (Harris Fast Soft Recovery)? Does it pay to attach the deflex sheets to the top plate of the chassis? Since my power transformers are not shileded like the SCD-1, does it pay to buy the TI shielding and "apply it" to the transformers? Thanks in advance for your inputs. Mike
I do not like to bunch wires together ( especially power supply and signal wires ). Spread them out as much as possible. In terms of "re-wiring" something internally, keep in mind that this WILL alter it's tonal balance to a noticeable degree in most cases. This can be taken advantage of to some degree if you know what your doing and working with. As to specific recommendations of brand names, i won't / can't do that. There are just too many variables involved, especially the one called "personal preference". As to the various solders that i've worked with, Wonder is by far the easiest to work with. As to which one "sounds best", i don't know. I've read that Jenna labs did a test and they came away with the opinion that the Cardas sounded the best. As you might guess, that is what they use on all of their cables. I have used it many times before and found it slower to melt, slower to form and easier to make a bad connection with. I also like to take detailed notes when doing mods, as this way you can always "back-track" should you need to. There are some things that just don't work out the way that you think that they should. Being prepared for that will never hurt you. Sean
Sean, thanks for your input. I'll remove the product names and just ask the questions in a generalized way. In terms of "bang for the buck" which components are usually better to replace in the power supply and analogue output stage circuit? Capacitors, Resistors, or diodes? Please give order of biggest improvement to least improvement. Does it pay to attach the noise damping and RFI/EMI blocking sheets to the top plate of the chassis? Thanks, Mike
I work with radio communications gear and most of my audio based "experimentation" has been on some specific power amps and mostly speakers and DIY cables. I'm currently "gutting" some preamps and will consider this to be a "learning experience" in this area. As such, i will say that there is no ONE thing in ANY design that is a cure all unless the product is really just underdesigned to begin with. From what i've found, "modding" or "tweaking" gear is kind of an accumulation of a bunch of small steps forward that add up to a long and pleasurable walk down music lane. Most of it is trial and error based and that's why it is important to be able to reverse your "mods". Even the experts run into "why doesn't this work right" type of situations. As to shielding, i would try that in your sources, especially digital. I have found that my DAC's are quite susceptible to RF based interference. Other than that, let US know what YOU find out.... : ) Sean
Obviously the individuals against mods here take a flat earth view on the issue. as a close personal friend of
Stan Warrens i have heard 100s of his mods many have been done on adcom gear and all i can say is you don`t know what your missing if you haven`t listened to one of his pieces.
If an individual knows what he`s doing and what to do it to
the result`s can be wonderful.
most of his mods are less than $300.00 and more often are around $160.00
Remember, the GFP-750 is Adcom's cost-cutting iteration of a Nelson Pass design they licensed. If you want to improve it you'd be far better off selling it for $800 and buying the real thing: a used Aleph P (with remote) for well under $2k!
Think about it. I even queried Nelson about the GFP unit, and he said he had no idea how well they pulled it off.
OTOH if you use the GFP passively, it's probably worth keeping. If you use it actively, I'd try the Aleph P. It's build quality, transparency, ultra-quietness, and 3D staging are quite remarkable...and that heavy remote oozes ergonomic
luxury! Good luck. Ern