A tour of a Hoppe’s Brain GFA-555 restoration

Hi everyone! One of my customers sent me a particularly nice GFA-555 MKI to be refurbished. It’s never been tampered with, and has very few scratches on the case… just beautiful. So I thought I would take lots of pictures along the way as I refurbish it, and show you the latest iteration of my GFA-555 rebuild process. This is the full monty upgrade package including the Hoppe’s Brain soft-start power supply board, with all sound quality and reliability improvements. $1025 in total.

Adcom GFA-555 Amp, being all amp-ey.

Continue reading A tour of a Hoppe’s Brain GFA-555 restoration

Introducing the Hoppe’s Brain Adcom GFA-555 soft-start power supply

Exciting news! Hoppe’s Brain power supply boards for the GFA-555 are here!

20171102_210531

These boards feature a number of improvements over the stock arrangement with the old-style chassis-mount components:

  • Soft-start circuit reduces stress on components like switches and capacitors.
  • Reduced hum, buzz and noise from the amplifier’s speaker outputs.
  • Capacitance upgrade from 4×15,000uF to 4×27,000uF. Nearly double!
  • Earth-loop breaker with diode clamp safety shunt.
  • Amp is converted to a 3-wire, earth-grounded chassis appliance, for safety and better noise rejection.
  • Surge protection MOV
  • Snubber capacitors across AC side of bridge rectifiers
  • Compact layout. Overall wiring lengths reduced, fewer mechanical connections, and a much cleaner internal layout.

Continue reading Introducing the Hoppe’s Brain Adcom GFA-555 soft-start power supply

How I clean Adcom GFP-555 and GFP-565 record and playback selector switches

Hey folks, I hope this will be useful to anyone attempting to clean an ALPS sliding listen/record selector switch like those used in the Adcom GFP-555 and GFP-565. These are common in many brands of preamps and receivers.

Ribbon slider-switch inside GFP-555.

Continue reading How I clean Adcom GFP-555 and GFP-565 record and playback selector switches

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.

Continue reading Improving turn-around time: Narrowing focus, new lab

Killing the buzz in the Adcom GFA-535. New power supply boards!

Adcom GFA-535 owners; Has it always bugged you, how the right channel of your amp buzzes through your speakers more than the left channel? Yeah, me too. The buzz is a buzz-kill… so I killed the buzz! With this thing I made.

Now, the GFA-535 is a legendary little amplifier, deserving plenty of buzz, but it’s too bad so much of it comes out the speakers. Oddly, the GFA-535’s bigger sibling—the GFA-545—using the exact same amplifier boards as the 535, is nearly silent as a stone. What’s going on?

Continue reading Killing the buzz in the Adcom GFA-535. New power supply boards!

ADCOM GFP-750 upgrade

The Adcom GFP-750 preamp was designed as a companion piece to the GFA-5802, with matching aesthetics. It’s a MOSFET based, single-ended Class-A preamp designed by Nelson Pass. Conceptually, it’s similar to the Pass Aleph P and the ‘Bride of Son of Zen’ DIY project.

NOTE: For visual comparison only. DO NOT STACK anything on top of a hot-running amplifier like the GFA-5802.

Continue reading ADCOM GFP-750 upgrade