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

Posted on by hoppesbrain

UPDATE 2022.12.19 This is how I was doing GFA-555’s 5 years ago, and I have a new article describing how I do them now…
https://hoppesbrain.com/2022/09/26/another-tour-of-a-hoppes-brain-adcom-gfa-555-restoration-5-years-later-with-better-technology/

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

Posted on by hoppesbrain

Update! This product has been superseded by a new power supply!
BFA-555 Smart 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.
  • 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

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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

Earth loop-breaker boards

Posted on by hoppesbrain

UPDATE: a newer version of this product is available in my store here:
https://hoppesbrain.com/product/earth-loop-breaker-board/

Earth-Loop Breaker

OK, this tiny circuit board is just too cute!

It’s an “Earth loop breaker”; A common method of providing some isolation between star ground and chassis, lowering noise in an amplifier. I designed it for the GFA-555, but it will also work in many amps.

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Improving turn-around time: Narrowing focus, new lab

Posted on by hoppesbrain

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!

Posted on by hoppesbrain

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

Posted on by hoppesbrain

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

Posted on by hoppesbrain

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