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Smokehouse Bob 10th August 2007 03:31 PM

Building a headphone amp from parts
I'd like to build a small tube amplifier using the power and output transformers left over from an Akai 1710 reel to reel. Is this "too ambitious" a project for a beginner? If not, what is a good site/source for the logical steps in designing such an amP/


EC8010 10th August 2007 03:54 PM


dsavitsk 10th August 2007 05:31 PM

There isn't any real difference between designing a headphone amp and anything else. You can think of it as a very powerful preamp, or a very weak power amp, but the circuits are the same. Whether you can do it from parts from an Akai 1710 depends on what parts it has. Post some specs and someone can probably tell you whether they will work or not.

Smokehouse Bob 10th August 2007 06:21 PM

Specs, that's where I am headed next. I'll see what I can mak eout and track down on the transformer model numbers. Thanks!

engels 11th August 2007 09:05 PM

If we're talking about this machine

Akai 1710

Then this is pretty good base for a small stereo amp. I think you will probably find a power transformer with 250V secondary (without center tap) which should be rated at least 90-100mA and 6.3V heater secondary @2.5A

The output transformers will probably handle 5W (or less).

If you planning a mono amp you may use EL84 output for some 4.5W, but for stereo I'm not sure the power tranny will have enough muscle for two 84's, you may want to use two "weaker" tubes like the ECL82 originally used in the circuit - or other triode-pentodes - ECL86, whatever.

The other idea for stereo is to use, say, two 6V6's and two 12AX7's (not 12AT7's) to save some current. Even if 6V6's + 12AX7's will require a bit more from the 250V secondary, you wil load the 6.3V heater secondary less so the tranny may handle this.

engels 11th August 2007 09:11 PM

sorry, I forgot it's a headphone amp... my previous post relates to an audio power amp.
If it's a headphone amp the power transformer should be enough for almost anything I can think of... only if it's not some overkill with triode-connected transmitter tubes.

Smokehouse Bob 11th August 2007 10:10 PM

Thanks! That is the reel to reel I had. The power transformer has labeled taps (that's a first for me) and the outs should still be good.

sorenj07 11th August 2007 10:46 PM

if I were you, I'd build a mu stage incorporating a pentode CCS. They seem to have promise and don't look too amazingly complicated, and have very very good linearity and PSRR. if you read through this article you might be convinced.

minhaj 12th August 2007 05:36 AM

dear Bob,

I have parts from such AKAI Reel to Reel. Pls be assured that the parts are high quality, the power transformer is mil spec Orion you can use it with solid state rectifier or can use Tube doing ganz bridge, out put transformer is sure high quality.

One thing reg speaker amplifier or headphone amplifier pls try simple/basic circuits with good quality parts-this is all about tube circuit simple is the best. For further experiences you can try complicated circuits lateron.


Smokehouse Bob 12th August 2007 01:38 PM

The (2) output transformers are each labeled:

RO-203 with a red wire and brown from one side, black wire and white wire from the other side

The power transformer is labeled Orion P-107C:

Left side - 240v/220/200/120/110/100/0

Right side - 6.3-1.5A - 6.3-1.5A - 210V-0.1A-E-210v

Any existing schematics that these would work with using the original (2) 6BM8 tubes and (2) 12AT7's?

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