Installing an Internal Protection Relay in an Adcom GFA 555 IMPORTANT: READ DESCRIPTION!

This video outlines the steps needed to install an internal speaker protection relay in an Adcom GFA-555 stereo power amplifier. This process is not amp specific, in that the basic steps apply to any amplifier.
ERRORS WERE MADE IN THIS VIDEO!
First, and most important: a ground wire must be run to the protect board for voltage testing.
Second: this module is not suitable for balanced/floating outputs.
An edited video will be uploaded during the weekend.

[@victormihai3929]

Wow, like you read my mind. I have a GFA 555 and I'm always on slight edge because it has no protection but never knew it was an 'easy' fix. Thanks for clear and concise instructions.

[@raygianelli3612]

Thanks Victor! The 555 is a good candidate due to the amount of room inside to mount the module. And the peace of mind is priceless!

[@vegaslimoguy2376]

I am a collector of Adcom gear, and I own over a dozen power amplifiers, several different models. I have used all of them for over 30 years and have never had a problem with any of them frying any speakers or anything. They have all performed flawless over the years and I drive them pretty hard. Never had a problem with any of the bad caps that they had either, guess I have just been lucky.

[@RanTausi]

@@vegaslimoguy2376 Nice to know that you are ADCOM collector, I wish I could too.❤

[@RanTausi]

@@vegaslimoguy2376 Yes you are lucky Limo guy 🙂

[@f430ferrari5]

@@vegaslimoguy2376I only have my one GFA-5500 amp and never blew any speakers either and it still works great. I am even running the 2 channels in parallel. Paradigm bookshelf and some small JBL mini speakers which has a cap on them.

[@paulfx]

Just installed one in a GFA-535II with bad startup noise. The only place it fits is upright between the right-front panel and the heatsink. Of course I ran a circuit ground as described in the correction. It works famously!

[@raygianelli3612]

Glad to hear it, Paul! Has the amp always made this startup noise?

[@paulfx]

@@raygianelli3612 Yes, so I relegated it to the woofers. But it got worse in the last year. Ran fine after a loud *BURP*

[@mdzacharias]

I'm pretty sure those little white things that clip onto the amp modules are thermal switches. S602, and S603.

[@raygianelli3612]

Mark, you're usually right about things like this. I do see something marked T1 on the schematic I've got, which looks like a thermal cut-out. I found another schematic on the net which shows S602/603 in the same place, a UP-62, a search which shows it as a thermal protector. Thanks for the clarification!

[@najzain]

I found this over the internet whilst researching on Protection Circuit: With an amp like the Adcom, relay protection systems have some serious drawbacks. The DC supply Voltage is around 70 Volts. If a fault condition occurs, then it is likely the full 70 Volts DC will be supplied to the speaker connections. Unless you spend a great deal of money (more than the cost of the amplifier) on a specialised relay, the relay you purchase to do the job will have a breakdown Voltage of approximately 30 Volts DC. This, despite the AC Voltage rating of the relay (which may exceed 250 Volts AC). For all intents and purposes, all relays may be assumed to possess a DC breakdown rating of 30 Volts. You MAY be able to mitigate damage by employing a (sound damaging) fuse in series with the output. When the relay activates, the output will be shorted to earth. The resulting current should blow the fuse. It is a bit hit and miss and speaker damage is still possible. Can you please share your insights on this and does a protection circuit really help? Do we really need it?

[@raygianelli3612]

Relay contacts can weld together during a failure, but frankly I've never seen it. And one of the other things the module does is to prevent startup/shutdown pops or thumps, which unlike catastrophic failure happen every time you turn your amp on or off. For $15-20 US it's cheap insurance.

[@najzain]

@@raygianelli3612 thanks for the reply! Do you think the circuit can affect the sound quality? I have heard circuits can reduce sound quality. Also, I am looking for a restoration kit. I am not based in USA but looking for a link where I can buy and have it delivered in my hometown. Can you pl share a link of recapping kit.

[@raygianelli3612]

@@najzain Zain, I don't think that the relay would degrade the signal audibly, at least nothing that mere mortals can hear. I was able to find the relay on UK eBay, but I can't recommend any sellers as I've no experience with them.

[@najzain]

@@raygianelli3612 thank you

[@joeymarcos6133]

Hi Ray I’m a new subscriber. I got interested when you mention “the module prevents start-up/shutdown pops or thumps”. This is exactly happening to my GF555 mk2. I was under the impression that it could be a failing capacitor.

[@RanTausi]

Thanks so much for this video , I have bought this board 3 years ago and it is just seat in my drawer , I have the GFA 555 MK2 which I have bought new never used , I t was in storage more then 25 years new never opened factory box so I was lucky to buy these beast amp. I have bought the soft start board as well so It would be perfect If you can do video for soft stat implementation. Thanks a lot

[@raygianelli3612]

Ran, I'd not heard about the soft start board. Thanks for enlightening me! I'll have to look into that. So yeah, there may be a video in the future!

[@RanTausi]

@@raygianelli3612 Appreciate! Thanks and have a great day

[@robmata474]

20 years never had a isssue with Adcom…

[@g.fortin3228]

Wow Ray ! this is Great ! ! I have an Adcom GFA-545ii ( 100 wpc ) and my brother has two GFA-555ii ( 200wpc like yours ) My Question can this same model protection module be used on all 3 amps ? I found them online and want to put in an order. Thanks so much for this video, I had not known it was a thing to add the protection but certainly is a super idea. Your instruction is great, and appreciated.

[@raygianelli3612]

Electrically the modules will work. I can't say if the 545ii will have the necessary real estate inside to place it though.

[@g.fortin3228]

@@raygianelli3612 yup plenty of space, caps are smaller in the 545 it frees up some space. I had to make a bracket and mount it vertical though so not crammed and same module you have there too.

[@raygianelli3612]

@@g.fortin3228 Good to know. Thanks for the update!

[@scrappy7571]

I have a Hafler 220, that does not have any speaker protection. Pretty scary to think what might have happened to my Acoustat 3's back in the day. I plan to bring it out of retirement soon and adding protection is on the to do list.

[@raygianelli3612]

Yeah, it's a crapshoot. I had a Crown DC300A set fire to a 15" woofer when I was playing in a bar band. Never forgot that! I've toyed with the idea of making a box with speaker in/speaker out jacks with one of those modules inside.

[@andymouse]

@@raygianelli3612 That's a great Idea !...cheers.

[@raygianelli3612]

@@andymouse Thanks Andy! Those relay boards are still available for around $18. Like I said in a previous reply, I've thought about putting one in a box to provide and external protection solution.

[@andymouse]

@@raygianelli3612 The external box is the idea i'm gonna nick ! :)

[@lesgarten]

@Ray Gianelli Did you do an updated Video on this?

[@raygianelli3612]

Just the one posted

[@lesgarten]

@@raygianelli3612 Thanks, just found it.

[@roroseppel2077]

Nice job Ray ! I wonder if the DC protection module works correctly in the bridging mode...

[@roroseppel2077]

Hello Ray, I also wonder if the DC detection can work properly without any ground reference connected ! The soft start works properly, but the rest...Is the amp protected ?

[@raygianelli3612]

Roro, you're absolutely right. I am going to edit the video this weekend, and I put a notice in the description stating errors were made. Thanks so much for making this comment and pointing out my screwup!!!

[@roroseppel2077]

​@@raygianelli3612 It's nice to land you a hand ! You can even test the DC protection by taking the module appart and injecting some DC voltage and you can then measure at which voltage the relay clicks off

[@RanTausi]

@@raygianelli3612 Hey Ray, when you rout the positive L and R wires from the speaker binding posts to the protection board IN don't you need to do the same for the Black ground wire the same ?

[@roroseppel2077]

Don't forget to discharge teh large filter capacitors before you put your hands inside the chassis !

[@raygianelli3612]

Roro, the Adcom has bleeder resistors across the caps, so they discharge pretty rapidly.

[@carlespy7470]

Could you please add a link to the protection module you installed? I plan to install it in my GFA 555 II.

[@raygianelli3612]

Here' you go, Carl. Don't forget to ground it! www.ebay.com/itm/125254850460?hash=item1d29c5579c:g:VbYAAOSwmfhcQyzR&amdata=enc%3AAQAIAAAA4PbuHPXop2pFzOmzHYYGnoF0wKJdZONhKTG53fcXYg38b040cX%2BmwojJvt%2FM3UEiN9Y3kWt9oF85esEAnBhX7ja5irjBpsHHMsakyt6sBkmJ0vKhfdzQfthgwqr5w6KsIFYk1bQyaJpV8vXmRLscay1R8yIR6lpcTNp1wytlzw3%2FQq1hDbVq8dzRCyFkq3MbCQJ1ZcFQyzNpqWfO0HrJQ59i9VnU9ywomPniNsfM7kR1QR7J6iwLCQoOINICqBuC0uzMqx2K9z1uIIdQAeWRKO%2FaWxozfeCKS9A0IQYBXdg8%7Ctkp%3ABFBM2p3Wrrti

[@najzain]

Great video! Is there any link you can share where I can purchase the protection circuit? I am based in the UK and can buy online. Also, I am looking for recapping kit for GFA555.

[@raygianelli3612]

There's not many capacitors in the 555, maybe 6-8. Just look at them and order them from a reputable vendor, I think RS Electronics is UK based. Here's a link to the module I used: www.ebay.co.uk/itm/264680770570?hash=item3da0340c0a:g:WL4AAOSwSgRglTpj&amdata=enc%3AAQAIAAAAwLRkXDYrLgxK2sVUNVK9b7MtBJEaksOr%2BtZi98FBf2mEghjmX3AfREry6wItlYnN9sB517aQCTL7XwVxBQSc9sp%2BN6PwsPKCER%2FJ0wYZNsfnAp2gUIwf5axPGlg6YfAJUNdoDnmN0zMmEiqTpzlmq%2B6tjCHayoU8IH%2FjEvR7M6BXSR1om19XYsXZLPz5cMYjMNAkkUzO3%2BNZD0CK3e1iPSZsG%2BVs1XuJTDKz0mDzTu1roFY7BSykF0vqOMFBorQZVA%3D%3D%7Ctkp%3ABk9SR4Lx-cXDYg

[@captainwho1]

​@@raygianelli3612 Thanks for that. I checked and they ship everywhere except United States so I will have to find a different one. Thanks for the great video.

[@raygianelli3612]

@@captainwho1 Mouser or Digikey in the US.

[@captainwho1]

@@raygianelli3612 I found it on ebay (not uk) by copying and pasting the title description. I believe it is the same one you used.

[@ericschulze5641]

Im have the opportunity to get an adcom gfa6000 for free, I'm guessing this will work on that also ? I'm a novice but have gotten good at recapping solid state recievers, & have a decent understanding of circuitry, this was my biggest concern if I get it .your input would be greatly appreciated

[@raygianelli3612]

No, because the 6000 is a 5 channel amp, and these modules are 2 channel. Judging by pics I looked at on the net, there's no room to add one, let alone three.

[@ericschulze5641]

@raygianelli3612 it's for personal use & it's probably the only way I can afford to have anything substantial, what if I use an external housing, being careful not to block air flow ? New longer wires ect ,I worked in an industrial fabrication shop doing just that day in day out , all day ,for 4 years, mounting boxes, wireing,wireing,wireing, if you think that will work, should I twist the wires to help prevent interference ? Hey! ! ! what if I put the protection relay only on 1 set of outputs and only used that? Would that work ? although I'd prefer to do them all

[@raygianelli3612]

@@ericschulze5641 An external box would work, and no need to twist wires since it's not a low level signal scenario. You could do any amount of channel you wish. Just limited by how much trouble you're willing to go through.