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Eagle SA 100 My first tube amp!!

Eastham

Eastham

More Class-A than ever!
My first tube amp, £40 sold as untested. I can't wait for it to get here. It's a Eagle SA 100 cute little unit, from what I can find it's a 10 - 15 watt unit. Perfect for my small room.

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So my plans for this is a complete rebuild. I'm super excited but at the same time really intimidated, I've never worked on anything tube related so I hope all of you can help my with my baby steps into the world of tube audio. Dunno if I'll ever put the top cover back on after removing it! :)
 
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crispycircuit said:
Nice find ! A great amp to learn/work on. I'm sure you'll be pleased with the unit. Find a schematic for it.....
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I've been scouring the web top to bottom and I'm afraid I'm going to have to reverse engineer it. It's a fairly simple looking not to hectic, I'd love to hot rod it if I could, maybe squeeze a bit more power out of it.

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What a rat's nest! these pics of the internals are from a thread I found on Vintage-Radio.net. I certainly hope mine looks as clean and unmolested inside as this one.
 
From what I can tell Eagle was a British brand. I think this little amp would probably pair up nicely with all my Wharfedale speakers, my 15ohm Dovedale W2's especially. We brits have small homes so most of our vintage gear is pretty low powered high efficiency. My Tritons are 89DB and my W2's I think are 92DB's though don't quote me on that.
 
That's a single ended el84 amp good for around 5 or 6 watts a channel which is plenty. I have a single ended el84 amp in my 20'X30' living room and it will get plenty loud playing through some jbl lx55 speaks. Nice little find you have there :D.
 
So I've been doing a little research on tube gear. What's the difference between a single ended and a push pull design?
 
Eastham said:
My first tube amp, £40 sold as untested. I can't wait for it to get here. It's a Eagle SA 100 cute little unit, from what I can find it's a 10 - 15 watt unit. Perfect for my small room.
So my plans for this is a complete rebuild. I'm super excited but at the same time really intimidated, I've never worked on anything tube related so I hope all of you can help my with my baby steps into the world of tube audio. Dunno if I'll ever put the top cover back on after removing it! :)
Click to expand...
That looks like a GREAT first tube amp project, and likely one that will sound excellent when you've got it up to speed. Definitely a single-ended stereo amplifier, and it actually looks pretty well constructed and (believe it or not) quite tidy. It should be pretty easy to work on.

You'll want to replace all the electrolytic capacitors in it, for safety. That looks simple enough. The resistors look like they might be wirewounds, which don't drift off spec over time quite as badly as carbon composition resistors. Most of them might be within tolerance still, saving you a bunch of work.

Eastham said:
From what I can tell Eagle was a British brand. I think this little amp would probably pair up nicely with all my Wharfedale speakers, my 15ohm Dovedale W2's especially. We brits have small homes so most of our vintage gear is pretty low powered high efficiency. My Tritons are 89DB and my W2's I think are 92DB's though don't quote me on that.
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If it is a British brand, I'm guessing they rebadged or outsourced the manufacturing - that amp looks Japanese to me! Not a bad thing.

If it's not an EL84 amp, those might be 6BM8 output tubes. The Japanese built a bunch of little amps with those outputs, which are quite nice sounding little valves. Either way, I think you've every right to be excited about this one!
 
It also looks Japanese to me, The only thing that makes me unsure, is the electrolytic caps, 99% of the Japanese have Elna or Suzuki, I have not seen that brand before.
 
Eagle rebadged Japanese units, I believe. As this has a phono input, I wonder if it is for MM carts, or just ceramics? I guess the latter. I would also be that the power tubes are 6BM8, known as ECL82 tubes in the UK. Very nice sounding too.

Replace those grey caps underneath (one has already been replaced with a yellow poly one), on the controls and the large one for the power supply mounted above. Just ask if you're not sure what to use.
 
I'm pretty excited about it! No stranger to recapping, just used to solid state stuff with PCB's lol. If this little amp's phono pre amp is for ceramic cart's would I need to modify it/ use a separate RIAA preamp for MM carts?
 
Hmm, guess that'll be one of the things to add while I'm in there restoring it. Or maybe one of those little DIY RIAA pre amps would work.
 
Eastham said:
Hmm, guess that'll be one of the things to add while I'm in there restoring it. Or maybe one of those little DIY RIAA pre amps would work.
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If you're integrating an IC-based magnetic phono preamp, you could make positive and negative 16~17 VDC power supplies by building a couple of half-wave doublers off the 6.3VAC heater line, assuming one side of it is grounded. Another possibility is to make a high-voltage transistor RIAA preamp that steals a few mA off the existing B+ rail. I spent some time developing one of those, with the intention of replacing the tube preamp section of a Dynaco SCA-35, but that project has been stalled for a few years now. Let me know if you want the schematic.
 
BinaryMike said:
If you're integrating an IC-based magnetic phono preamp, you could make positive and negative 16~17 VDC power supplies by building a couple of half-wave doublers off the 6.3VAC heater line, assuming one side of it is grounded. Another possibility is to make a high-voltage transistor RIAA preamp that steals a few mA off the existing B+ rail. I spent some time developing one of those, with the intention of replacing the tube preamp section of a Dynaco SCA-35, but that project has been stalled for a few years now. Let me know if you want the schematic.
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Thanks, I was thinking of going with something along the lines of a tube RIAA pre amp. I wanna try and build a all tube system.
 
Guy's! At long last it's here!

Gave it a quick brush and took a pic

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I sprayed all the pot's with Servisol 10 and worked them back and forth for a bit and plugged it into my DBT. No DC offset, but when I use a pair of cans on the speaker outputs I get audio, clear audio at low volume but it gets distorted and crackly when I adjust the volume and then it goes back to being fine, I'm guessing that theirs a load of bad caps that need to be replaced and probably some resistors too.
 
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