st-70 as good as it gets?

[bigjppop]

Now I know that the Dynaco ST-70 is not the end all be all in tube amplifiers and I'm sure its possible to build/buy a lot of products that do a lot of things better than the ST-70, but for what it is/does is the this guy about as good as it gets?

I've been reading here (and other places) for quite some time and am trying to nail down a nice sounding, 30ish WPC tube amp to try out on some 87-90 dB full range speakers I want to build. I'm not married to any one design/tube/topology, I'd just like something that can handle some lower efficiency speakers.

I just finished the Tubelab Simple SE which was a lot of fun and I'm really liking it, and it is going really well with my higher efficiency speakers but I've been bitten by the DIY bug and now that I'm finished with that project I want to try my hand at something else. I'm far from an expert so I'd need something that's not too terribly difficult. I've read lots of people really love the ST-70, especially with one of the many upgraded driver boards out there and I just want to know if I'm missing another option.

Now, I've never heard the Dynaco, but I do know that I'm not in love with the look so if I go that route it would be a clone built into another chassis but other than that, I'm open to anything.

Thanks in advance!

[Triode Kingdom]

What's your budget? That power level could include quite a few PP amp designs from the 60s. Even some 211/845 SETs do that.

[taj]

Hey bigjppop,

I asked a similar question last week, as my interests seem quite similar to yours. A couple project names kept surfacing (besides the myriad ST-70 options) for your consideration.

SY's Red Light District

TubeLab's soon to be offered Simple PP

Gingertube's Baby Huey

All look well respected and well documented from my limited reading.

I agree the ST-70 isn't much to look at, and I was thinking of piecing together my own from all the vendors on the internet, using a chassis of my own creation. If you go this route, I think it would be wise to select a driver board first, so you could optimize your parts purchases ( especially tubes) for that particular board, based on advice by the creator and that given here.

That's my take. I'm looking forward to reading others' advice here.

..Todd

[Wardsweb]

My latest project is using a stock Dynaco ST-70 as the basis for a modern version. You can follow the build here: Wardsweb ST-70 Project

[boywonder]

Originally Posted by taj

Hey bigjppop,

I asked a similar question last week, as my interests seem quite similar to yours. A couple project names kept surfacing (besides the myriad ST-70 options) for your consideration.

SY's Red Light District

TubeLab's soon to be offered Simple PP

Gingertube's Baby Huey

All look well respected and well documented from my limited reading.



..Todd

The above amps are a fair bit less than 25-30W.........

For 30W or so, I would consider PP Ultralinear EL34 or PP triode KT88.

My first project was Gingertube's Baby Huey. I built the original version (cap coupled, no mosfets) and it sounds great. It's in my office where I build amps, and I listen to it frequently with 86db speakers. Fine for the office, but it won't get very loud with 86db sens. I am planning on re-building it with the later mosfet/fixed bias mod, just have not got around to it yet. It sounds very nice in my main system with 90db sens speakers. When dialing in this amp, I put a pot and a fixed R in series to vary the feedback a little bit; a great quick experiment to listen to the effect feedback makes.

IIRC, the Baby Huey is UL (around 10-11 watts) and the Red Light District is Pentode (around 15W?), so RLD will put out a few more watts.

I've also breadboarded and built a couple of iterations of Poindexter's EL34/6GK5 music machine, and it also sounds very nice, although I have not had one put together long enough to really compare it to anything else. It's a fixed bias triode EL34 with a CCS for the 6GK5 and puts out around 12-14 watts. I really like this design because it is a simple, two stage triode with fixed bias and a CCS and no feedback.

I am contemplating using trioded 6550's/KT88's in Poindexter's EL34 MM as a next step, as I am a semi-newbie as well and it should be good for some additional hands-on training. I imagine that this would yield around 25-30 watts of PP triode, without feedback in a 2 stage design.

There is also Triode Dick's Bill and Mono Bill that should have the watts in a triode KT88 design, although I have not seen much discussion about this amp.

If anyone has a good schematic for any other KT88 PP triode please point me to it.....

[bigjppop]

Thanks for all the responses so far. As far as budget, 500-700 is roughly where I'd like to be. I'm not hard and fast here, but I can't afford a 2000 project but I don't need to go dumpster diving either.

The EL84 based amps all look very interesting and I've explored them pretty thoroughly before but they are somewhat limited in the power department. I've seen Tubelab talking about making his Simple PP into monoblocks which should give me the power I want but then I'd need to build two.

The SET 845/211 sounds great in theory but I have yet to see a design that is newbie friendly and I'm also fairly confident that that type of project would get expensive in a hurry. Please advise if I am mistaken on either of these points.

As Boywonder mentioned, I think either a UL PP EL34 design or a PP 6550/KT88 in triode mode would probably be the most bang for the buck and the easiest thing to handle at my skill level.

So, that brings my back home again... UL PP EL34 sounds strangely like the ST70 and again, like Boywonder, I haven't seen much discussion on a 6550 based triode project (but I'd love to!).

[tinitus]

Well, you would get like 10watt more, but probably at the cost of quality, AND it still cost more money

I remember someone stated that ST35 sounded better than ST70
Its a subjective statement, and amps are different, but it wouldnt surprice me

Not sure, but was there talk about making Simple PP into 4-tube monos

[bigjppop]

Originally Posted by tinitus

Well, you would get like 10watt more, but probably at the cost of quality, AND it still cost more money



Not sure, but was there talk about making Simple PP into 4-tube monos

I think I missed what you're referencing here in the first sentence.

I had also heard about the mono Simple PP which could be very interesting as well.

[SY]

The above amps are a fair bit less than 25-30W.........

The difference between 15W and 25W is only 2dB. Barely noticeable.

[tinitus]

Originally Posted by bigjppop

I think I missed what you're referencing here in the first sentence.

I referred to EL34 PP or KT88 PP vs EL84 PP

At first I too was a bit surpriced that Simple SE wasnt turned into Simple PP monos
But now Im quite happy that George decided in favour of EL84 PP