Improving turn-around time: Narrowing focus, new lab

Hello everyone,

My sincerest apologies; My communications have been terribly slow, and my turn-around time for refurbished equipment is getting out of hand. I have customers waiting up to four months for their equipment, and that’s no good. I wouldn’t want to wait that long!

I never anticipated such a level of interest! Many thanks to all of my customers; it’s a pleasure to help you build your music systems, and I love hearing people’s comments after they get their gear back.

I like to say “YES!” to everyone’s projects, but I have taken on more work than I can possibly keep up with. I am buried in emails, and it’s getting hard to find time to work at the bench. Things are snow-balling on me.

It’s a good problem to have. It means I’m succeeding, but I won’t be for long if I don’t limit the scope of what I do.

I want to give better service to a smaller number of customers, and I need time to pursue other projects for Hoppe’s Brain. So, I’ve made the difficult decision to stop working on the later-model Adcom MOSFET amplifiers and multi-channel home-theater amplifiers, and only service the older Adcom bi-polar transistor amplifiers and related preamplifiers. (Models listed below.) I will continue to streamline my process for these models; improving quality and performance, as well as turn-around time. I can invest more time in things like designing new circuit boards that improve the performance of these particular models.

I’m sorry, MOSFET Adcom owners. It’s not that they’re bad amps, but something had to give, and so I’ve chosen to only work on the classic bi-polar models.

From now on, these are the only models I service.


  • GFA-535 MKI and MKII
  • GFA-2535
  • GFA-545 MKI and MKII
  • GFA-555 MKI and MKII
  • GFA-565
  • GFA-585


  • GFP-1 and GFP-1A
  • GFP-555 MKI and MKII
  • GFP-565
  • GFP-710
  • GFP-750

So, why choose the Bipolar models over the MOSFETs? The MOSFET Adcom amps are a really elegant circuit design, and they sound great, but I have found them a lot more troublesome to work on. I’ve spent a lot of time tracking down problems that turned out to be quality-control issues. For example…

Metal debris stuck underneath transistor insulator, causing intermittent short. Unfortunately common with the GFA-5802.

I’ve seen this issue three times now on the GFA-5802. It means extra work and expense for me, as I have to inspect and replace every single insulator for every GFA-5802 that I work on. These insulators are not really meant to be re-usable, though people often do. I replace them.

Also, the output devices in the GFA-5802 are the no-longer-made TO-3 “top-hat” style International Rectifier IRF244’s. These are excellent devices, but when they go bad, they must be replaced in sets of 8. There is no reliable source for such things and counterfeits are everywhere. Cannibalizing another amp is about the only option.

I see similar quality-control issues with other MOSFET models, and the home theater amps.

In contrast, the quality control of the classic bi-polar transistor amps like the GFA-5×5 is excellent! I rarely see factory errors like the above. They are consistently well made. Contrary to rumor, I have not noticed any quality control differences in the Adcoms that were made in Japan in the early 80’s, versus those labeled “Made in Taiwan” or “Made in China”. I would rate Adcom’s quality control as excellent during the 1980s and 1990s.

* Incidentally, none of this reflects upon the current holder of the Adcom brand name. I simply have no opinion on the currently manufactured Adcom products, having never seen any in person. I have heard that the new Adcom is friendly to inquiries on past products.

To my customers who are still waiting, I greatly appreciate your patience as I work through my backlog. I’m sorry that it’s taking longer than I may have told you. But everyone’s gear gets my full attention, and I take the time to do every piece right, just as I would want for myself. This is my only occupation, and I will get to everyone.

And I have a new lab to help speed things along! Wow, what a difference. Check out the new cockpit.

  • HP 8903B Audio Analyzer
  • Rigol DS-1054Z Oscilloscope
  • Rigol DG-1022Z Function generator
  • Hakko FM-205 shop-air powered de-soldering station
  • Hakko FX-951 Soldering Station
  • Fluke 287 Multimeter
  • B&W 602 Speakers driven by Adcom GFCA-535

Things really go faster with all the new gear. I’ll blog more about the new lab soon.

Thanks everyone,


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