[ericj]

I'm working on silly projects like pulling the transformers from a Koss E./9 energizer and building an SRD-7 MkII-like circuit around them.

but, I would like to say, because nobody else has said it yet:

If there's going to be a redesign of Dr. Gilmore's excellent solid state amp, I, for one, hope that there's enough DIY 'stat interest to support a group purchase of professionally made boards.

I'd love to build a KGSS, but I'm somewhat daunted by the mixture of high voltages and P2P wiring that I'd currently have to do. Not that i can get the fets anyway.

 

[pabbi1]

There are several KGSS currents underfoot as we speak. I know the psu has been completely overengineered, and is ready for the challenge, and know the amp boards, with the LinearCircuits lsk389 is close to complete... I think. Now, whether the players will surface that or not remains to be seen. I threw out a REALLY crappy single board file that others were going to consider redoing (with the evil 2sk389) and there was some discussion back when over 'there' - where they lament thin skin.

That said, I am in. Marc, ready yet? Yes, the BH needs a redo, but the HEV70 is NOT an acceptable backup...

well, or

Or, dangit, if a Bijou can be built with cheap (excellent) Russian tubes, can something cheaper than el34 be used in a hybrid?

ORR, given the surfacing of the ES-1, as, apparently a STAX DIY circuit, might that be a cheap tube path with a different tube set?

Awaiting my tanning from KG, Birgir, and Marc, but, perhaps not in that order... weasel, rip my flesh. <sigh>

PS- then, for once, maybe we as DIY might also consider some custom machining to keep such a build from looking like azz? This from 'Mr substance over form'. Group buy for boards, transformers, case... couldn't hurt. And, this is NOT to scavenge sales from Justin - we are most likely NOT his clients for finished goods anyway.

 

[ericj]

A Stax SRX (aka ES-1) redesigned to use cheap and ubiquitous russian tubes would be very nice for DIYers.

 

[spritzer]

A SRX with 7n7's in the first stage and GU50's on the output would be an interesting take on the design. I'm going to build one around 7n7's and EL34's (which I have a lot of) using the Blue Hawaii PSU for all three voltages needed. It will require a custom made transformer and the PSU boards could be made so it is a viable diy project. The transformer won't be cheap but the amp should come in well under 1k$ with some very nice coupling caps and good parts all around.

 

[ericj]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif A SRX with 7n7's in the first stage and GU50's on the output would be an interesting take on the design. I'm going to build one around 7n7's and EL34's (which I have a lot of) using the Blue Hawaii PSU for all three voltages needed. It will require a custom made transformer and the PSU boards could be made so it is a viable diy project. The transformer won't be cheap but the amp should come in well under 1k$ with some very nice coupling caps and good parts all around.

Yeah, that could be very interesting.

I have to admit that i haven't studied the SRX schematic so i don't understand the requirements and limitations.

I'm basically dreaming of a tubed 'stat amp built out of russian tubes i can buy from latvian and ukranian ebay vendors for just a couple bucks each.

Even though i realize that the power supply is going to be a very significant expenditure no matter how cheap the amp stages are.

Anybody know what design Fitz was using when he built a few amps? There's a marked shortage of entry-level diy 'stat designs.

Even those designs from germany, which use about $20 worth of parts in the amp stages, turn out to have $250 power supplies.

 

[nikongod]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif I have to admit that i haven't studied the SRX schematic so i don't understand the requirements and limitations.

here are the MINIMUM PSU requirements.

1: high positive voltage supply
1: high negative voltage supply
2: heater supplies: 1 for both gain tubes, 1 for output tubes.

you could go further as spritzer says and build separate HV supplies for the gain and power stages. OR regulate a higher voltage than "stock" down to the voltage for the gain stage.
Quote:

Even though i realize that the power supply is going to be a very significant expenditure no matter how cheap the amp stages are. Even those designs from germany, which use about $20 worth of parts in the amp stages, turn out to have $250 power supplies.

I think the SRX is close to that design type.

With about 10 power resistors, 4 caps, 2 pots, and some other little junk per channel it is almost impossible to build the PSU less expensively than the actual audio section.

Maybe if you counted the cost of the tubes

 

[spritzer]

You certainly could substitute the 7n7's for some other similar dual triode and use some obscure pentode on the output. I chose those since I'm using them in other amps so have the sockets and tubes at hand. I going to use 3 different voltages plus the two separate filament windings (4A and 8A) since the BH PSU isn't that expensive and you can find some very nice caps for less then 5-6$ (Nichicon for example). The transformers are never cheap but for chassis you can use what ever you like. That Galaxy crap that Rudistor uses is very cheap and the amp and PSU could be in separate chassis.

 

[pabbi1]

For Team Cheap(est) Bastards, it is impossible (short of some broken ion implanter, or the like) to beat the Nabu for the amp, and possibly a Sun 911 for the PSU. Just add a group buy from FPE, and it will look as professional as most, and could even have a bling cover made by Pars Metal, etc.

So, are the usual 6nxp type tubes not stout enough? I remember taolk of some other smaller (pent)(tri)ode of some type a while back that would do very large current (something wit an 's' and a '6' iirc), but I'd also vote smaller tubes, IFF physics simply doesn't dictate otherwise. That is IFF we tube.

And, I also saw Marc's post about the 'brown dog' 2sk389 adapters for the lsk389, so one problem licked... or so it seems.

 

[luvdunhill]

I'm sure as hell not posting any schematics... must buy moar parts first and corner the market.

A few people know what output tubes I'm targeting (and 1 person knows what output devices I'd use for a solid state design, as he/she/it got confused on the part numbers enough times, I had to reiterate every time I mentioned the new part), and anything I concoct will have a solid state front end.

 

[spritzer]

The cheapest option is always to gut some old gear but you need quite a bit of space for the PSU unless you have some special PCB's made or use a simpler design. Unless you have a transformer made with all 5 windings you will need at least 3 transformers and 6 large caps in there as well. The amp can be much smaller but be aware that those plate resistors run hot, especially with something like a EL34.

You certainly can use a 6SN7 as an output tube or any of the other small triodes but they can't handle the same power as a EL34. Needless to say, more power is better. 6S4A can be used as well and are dirt cheap. A 6BX7 might be an interesting tube to try but some old pentodes and tetrodes not loved by the hi-fi industry would also work well.

 

[pabbi1]

6S4A was what I was trying to remember.

 

[mypasswordis]

I was wondering if there is any update to the KGSS using something other than 2SK389. Kevin Gilmore mentioned developing a new amp, the KGST, but I don't think any schematics were posted.

 

[cetoole]

Just use the LSK389, its a functional drop in replacement (not pinout though). Easy to get, and very good parts. Heck, easy enough that I have a baggie with 23 left in it here, and I believe Luvdunhill has personally had over 1000 at one time. Pretty sure no KGST schematics have been posted.

 

[pabbi1]

Well, there may be a new design available for DIY in about a month, the Stax Gods willing. Colin, ygpm.

 

[mypasswordis]

Oh good, there is a replacement. I'll wait for the new design to possibly surface on headwize since I won't get to building whatever it is I'm building until the summer, so I thought I'd just get parts here and there until then.

Has anyone tried any of the designs not by KG on the first page? That German hybrid amp in particular.

Edit: Er, I don't know why I automatically thought the new design would show up on headwize. Weird.