• 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.

Amp suggestions needed

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I posted this question on another forum and didn't get much of a responce so I thought I'd try here......

I would like to build a 30-35 wpc amp. I’ve done a little research and came up with 3 that meet my abilities and budget.

One is a ST70 based on DIYTUBE’s ST70 power board. http://www.diytube.com/phpBB2/viewtopic.php?t=604

Two is the Dynaco improved Mullard circut.

The third is the 20-10 amp in the RCA tube manual.

If anyone has and comments about any of these or any other suggestions, I’d really appreciate hearing from you. Thanks in advance.

Hi Dick,

I have built several diytube amps including 3 eiclones, 1 ST-35 clone and 1 ST-70 clone. All of them sound great, are easy to build and are well supported. Shannon's PWB's are very well made. No arguments here on whether or not PWB's are the way to go. As I've said, mine sound great. All except the ST-70 clone have solid state rectification. The eiclones and the ST-35 clone are in a tube-type home theater I set up. I think it's like a drug addiction - I just can't stop building.

I have some pictures of the amps built so far including all mentioned above posted here:


I am building a couple more amps including an 832 transmitting tube stereo novelty amp and two Local Hero monoblock amps as shown on Mr. Koren's page (I'm ordering parts now). I also have an Eico ST-70 I will eventually fine tune. And last, and probably least, 3 Dynaco ST-120 solid state amps (got them in a weak moment - but I'll work on them too). That's not a slam on the ST-120's. I just haven't powered them up and listened yet.

Whatever your decision, it will be fun I'll bet. If you'd like comments on the diytube amps let me know. They have a pretty good forum too.

All the best and regards,

My speaker are all vintage , Advent, AR, KLH, etc. I know people will tell me I am missing out on not looking at the advances in speakers, but I grew up with these and really won't change. Anyhow I have been using a 18wpc PP amp, and it works ok with some not so well with others. When I bought these speakers in the 70's I used 30-45 wpc SS amps and that drove them all well. I'm thinking that something in the 30-35 wpc range and with my size room this will gives these old guys a little more punch.
Thanks Ed. I forgot to mention that my current amp is DIYTUBE ST-35. And yes I'm very happy with the sound. Shannon and the fourm have been very helpful. I can't comment on the merits of using a PCB or not but I did build a SE amp from scratch a few months ago and I felt that was a little more of a challange than the PCB. So I guess I was thinking scratch build again.

How do you like the DIYTUBE ST70? Getting Shannon's power board and building around that would be a little more than just plugging parts on a board.

I like Shannon's ST-70 clone PWB design very much. In fact, it's sitting behind me in my office right now where I listen to it every day. I think that design is very good. To build it I bought a "clone" chassis I found on eBay (chrome plated and very nice) along with Shannon's board and transformers from Uncle Ned. It works very well and I like the sound. The upper end is especially good. I'm using it with some two-way (8" woofer and a silk dome tweeter) speakers I built that sound much better than I thought they would. Pictures of that amp are on the URL I sent earlier.

All that being said, I really, really like the eiclones. They seem to be more "punchy" than the ST-70 clone. That might be the power supply. The ST-70 power supply is marginal and I've already arced over a GZ-35 rectifier tube. I'm not a true audiophile that has all that esoteric vocabulary but I do notice very good detail from the eiclones. I've noticed things in the DVD's I play through them that I don't hear with the solid state amps I have. I can't explain that. The other advantage to the eiclones is that you can build them any way you want and they're easy to tweak in comparison to the ST-70 chassis. For example, I wouldn't want to drill holes in that beautiful chrome chassis the ST-70 clone is built on. The disadvantage is that you have to drill all the chassis holes for the eiclones. But you've done that already with the ST-35 clone so you're familiar with that process.

The eiclones also have Uncle Ned's transformers. They sound very good in my humble opinion. I'm not associated with his company, just like the build quality and the sound. They really are nice.

The Local Hero amps I'm building will go into two Dynaco Mk III chassis clones I found on eBay. They are also chrome plated so they should look very nice when they're done. I'm going to design a PWB for them myself using Mr. Koren's circuit and see how that works out. I've done PWB design before so that should be fairly easy. I just gotta get some free time!

Hope this helps. Check out the amp pictures and you can see how the ST-70 clone came out. It looks better than I thought it would for a home-built amp. And it sure sounds great!

Best regards,
I would definitely go with a circuit-board based amp rather than point-to-point (P2P) wiring for your first tube amp.

I have built several P2P amps and they are annoying, messy and time consuming; plus the chance of expensive "smoky" errors is extremely high.

I would seriously suggest going for the eiclone; it is a solid design and you can spend your valuable time making a nice chrome chassis!
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