• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

EL34 Integrated

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Was looking at this as a possible project, unless someone has a better choice with same or more power, and integrated. Looking for inputs, thanks.



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I hate that sort of phase splitter, but the circuit will probably work OK. If you up the B+ to 420-450V, use a 6600 ohm p-p output transformer, and adjust the cathode resistor values on the output tube, you should be able to get 40 watts easily.

You can make ANY power amp circuit into an integrated by putting in source switching and a volume control.
DIY amps

Some audiophiles like to build amps for the fun of building with many different designs. Some know the design will not be the best performer or outperform their present DIY amp in a few areas.

Others want the best DIY quality amp they can find as time & funds are limited. These types of DIYers want cost savings & hopefully building one great sounding amp or perhaps two amps.

If you are the second type, then I would guess the proposed amp is not going to be in the top few percent of performers & you may end up building another amp in the future.

The way I view it is I want a $3 to $5K quality amp for under $1K if I perform DIY.

Tubes I like are Sylvania 6SN7 'T' plate design, any 6P5GT (76), 45, triode connected Sylvania 6V6GT, 845, etc. I am finishing up on a 6550 amp just to find out if I can get a tetrode to sound great. I may never build another power pentode or tetrode amp. I also have experimented with vintage EL84 based amps & moved on to better tubes for audio.

Another bit of advice is the amp must match up well to the speakers with regard to amplifier power output.

My 2 cents.
I have an old Scott 272 " Dynaural laboratory amplifier". It's schematic looks the same as yours. This was the amplifier that got me back into building tube amps. I wanted to experiment, but did not want to mess up this rare amp, so I cloned it. The clone sounded almost as good as the original (cheaper transformers). The first thing that I changed was the phase splitter because the one shown is very hard to balance over the entire audio range.

I would also recommend cloning a Dyna ST-70 if this is your first amp. Or buy a used one and replace the caps. I used to own an ST-70 and it sounded better than my Scott clone. I have since sold both amps. I have purchased tubes and transformers from Triode electronics with no complaints.
I just purchased this integrated .It is using a marantz 8b circuit and fisher 400 transformers.The guy that built it did a very fine job.

The rca's on top are for biasing.The amp has 4 inputs on the back with iec.

Wired for 20 wts triode and sounds great!


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SY said:
Roger, nice score!


I also purchased some Siemens EL 34 tubes that will be in today.The Svetlana's that came with the amp already sound good.The amp also came with some nice tung-sol 6sn7 gtb tubes.

I have been listening to digital amps for awhile--it is a nice change to come back to tubes.

By the way dstockwell --i do have the schematic for this amp---i would have to make a copy and e-mail to you if you want it .
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