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!

Hoppe’s Brain GFA-555 power supply installed in GFA-555 MK1. Compact layout allows the toroidal power transformer to be moved to the right side of the chassis, where it induces less hum, buzz and noise into the amp’s circuitry.

These boards feature a number of improvements over the stock arrangement:

  • 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 4×22,000uF.
  • Earth-loop breaker with diode clamp safety shunt.
  • Surge protection MOV
  • Snubber capacitors across AC side of bridge rectifiers
  • Compact layout. Overall wiring and clutter reduced.

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.

GFA-535 I PS Board

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

Quick update, November 2016

Hi Everyone, it’s been a long time since my last blog entry. I’ve been so busy refurbishing amps and preamps! My wait times are getting a little long, but that’s a good problem to have. Customer emails were getting hard to track, so I’ve implemented Freshdesk, a cloud-based helpdesk ticketing system. (No affiliation.) Highly recommended! I can set due dates and track status, how long since I last contacted someone, etc… It’s reduced my own stress and improved my customer service. My queue may be long, but my customers are kept well informed.

Continue reading Quick update, November 2016

Adcom GFA-565 replacement boards Revision 2!

Even better! I made a few revisions to the original boards, and I can now say that these are better quality boards than the originals! These have plated through-holes for a more solid solder connection, and greater pad strength. They are also less affected by heat cycling. Even with poor soldering, a plated through-hole is extremely reliable.

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Continue reading Adcom GFA-565 replacement boards Revision 2!