Help Identifying

[collirol]

i am trying to find out more about these monoblock tube amps. i picked them up used with no information. They each have 4 el84 output tubes, can't remember what type of input tubes. They really sound great to my untrained ear. Any help identifying what these are would be greatly appreciated. Are these from a kit or a custom build?

Thanks,
Robby

 

[rayma]

Appears to be home brew.

Post some better, clearer photos of the bottom interior.

 

[planet10]

We need more info.

Is there anything under the can on then right side?

If it is a commercial product a good chance it uses ECC81/ECC83, (12AT7/12AX7), if it is diy it could be anything. El Cheap uses ECC81.

dave

 

[collirol]

i will check on that when i get home later today.

Also, i do not see any makers mark on the amp anywhere, so it makes sense that it is a home brew.

 

[grovergardner]

My guess? Homebrew push-pull parallel EL84, with a simple 12AX7 gain stage and cathodyne phase splitter. Some good pictures of the underside should tell the story. Also look for any numbers or indentifying marks on the output transformers (square cans). Might be an adaptation of very common Magnovox or similar console amplifier. I imagine they do sound nice!

 

[collirol]

Here are some pictures from underneath. i could not figure out how to remove the black cover on the output transformer and i didn't want to damage it. i'm sure you guys know some tricks.

 

[planet10]

6EU7

Ity is gonna be difficut to trace the circuit without some tidying nof the rat’s nest under the bonnet.

dave

 

[grovergardner]

I'm pretty sure it's just a voltage gain stage and cathodyne phase splitter with a 6EU7 instead of a 12AX7. They look competently, if not tidily, built. I would just enjoy them.

 

[planet10]

Yep… EL84 is easy to drive it could b e a LT Pair as well.

dave

 

[OldHector]

What is the big flattened wirewound resistor needed for, attached to the back panel? I think the absence of grommets where wires pass through the top plate is not so good.

 

[mctavish]

I cringe every time I see flying resistor leads just soldered to wires hanging off in oblivion.

What do people have against tag strips? To me looks like a fire hazard.⚠️🫣

But they look like they have good parts, maybe some tidying up and some proper attachments. And not having coupling capacitors glued to aluminum plates.😞

 

[benchbaron]

Who wired this up ? No constructional discipline..........wiring to electrolytics harbering with a short circuit.

 

[collirol]

So, from what i am understanding, this is most likely a home brew, not from a kit. The person that built it knew what they were doing, but just did a very sloppy job and took many shortcuts. It needs some tidying up, which i am not real comfortable approaching myself.

They sound really good and i would like to continue enjoying them.

Questions:
Is it a fire hazard to run as is?
How do i determine the number of output watts?
What is the purpose of the switch between the speaker output and the fuse holder?

 

[mctavish]

I would not consider those amplifiers safe. The way they’re constructed takes no regard to short circuits or long-term safety. A good bump, and one of those leads could touch the chassis. I would also assume from the skill level of the builder that he knew just enough to be dangerous….

Also fixing components with glue, especially in an amplifier with high voltage is simply not acceptable. I would either have a competent technician, go over them and wear things properly, but I certainly wouldn’t have them running in my house like they are now….

Just my two cents