Power amps for tri amp system

[kheper]

I know this has been beaten to death in every audio forum out there, but since all I'm driving is mid and high, is a SET amp suitable for an old rock and roll guy? I can understand where people prefer SET for vocalists, stringed orchestrial music, and other mid- forward music. The SET would be easier and cheaper to build, but if it isn't right for me, I prefer to stick with PP.

SET amps are frowned on (by some people) for rock because of their limited ability to pump out bass frequencies. Since you are using an SS amp for the bass, this concern is moot.

SET amps made with big triodes such as the 845, 211, etc. - however, do not suffer from a lack of bass, because they produce in excess of 20W audio output per channel, and the outputs they use are huge, well-designed and expensive.

[kheper]

So my cost savings from building a quad amp comes from one chassis and one power transformer instead of two? Every dollar helps.

You could move up to 25W tubes to save money, tubes and real estate on the chassis.

EL34s in SE UL mode will do ~8W output. EL34s in triode mode will do around 5W. 8W for the mid-ranges and 5W for the tweeters. 4 output tubes in total.

You'll only need one drive tube per channel in SE, unlike in PP where at least 2 (one for the volt amp and one for the phase splitter) are needed.

[coolhandjjl]

So I'm looking at building a SET amp wired in ultra-linear mode? I guess I don't know what that means.

Anyway, how do I go about getting a plan with tube and parts so I can price this out?

[kheper]

So I'm looking at building a SET amp wired in ultra-linear mode? I guess I don't know what that means.

Well, only the tweeter channels will be SET (Single Ended Triode). The mid-range channels will be Single Ended Pentode in UL mode. (Actually, the tweeter channels will have pentodes strapped as triodes.)

http://tubes.nekhbet.com/class.shtml

UL mode explained:
http://tubes.nekhbet.com/trans.shtml

[kheper]

Anyway, how do I go about getting a plan with tube and parts so I can price this out?

Here is a schematic for an SE UL EL34 amp with a triode mode switch:
http://diyaudioprojects.com/Tubes/KT88

An Antek power transformer. 300V-0V-300V @.33A for $38:
http://www.antekinc.com/details.php?p=730

The Antek configured as a FW choke input (with diodes) will yield ~415Vdc. You'll need to series the HV windings of this transformer and ground the center tap.

http://tubes.nekhbet.com/power.shtml#fulw
http://tubes.nekhbet.com/power.shtml#dio

c-153 choke for $13.50.
http://www.dynakitparts.com/store/product.aspx?id=248

[coolhandjjl]

If I make one quad amp, it may be difficult to sell in the future when I get too old for anybodies good. Maybe I should reconsider and go back to 2 separate amps.

So I’ll wind up with a SET and a SEPUL, each with 3 trannies and 4 tubes on the chassis. This will be my first build, so simpler and cheaper than a PP is helpful.

[kheper]

If I make one quad amp, it may be difficult to sell in the future when I get too old for anybodies good. Maybe I should reconsider and go back to 2 separate amps.

So I’ll wind up with a SET and a SEPUL, each with 3 trannies and 4 tubes on the chassis. This will be my first build, so simpler and cheaper than a PP is helpful.

Well, 1 power transformer + 4 output transformers + 1 choke = 6 transformers.

4 output tubes + 4 driver tubes = 8 tubes.

[coolhandjjl]

Well, 1 power transformer + 4 output transformers + 1 choke = 6 transformers.

That's if I go with the quad amp. I think it may be better to make two stereo amps.

The Get-SET-Go one uses tube that are too pricey for my budget. Clementine perhaps?

[kheper]

The Get-SET-Go one uses tube that are too pricey for my budget. I looked at the Budgie here, and Shannon uses 1 driver tube and the then the 2 main tubes, which in that case are EL84's. It's a 3wpc SE amp. I'm guessing it's wired as a standard pentode. Parts come to $363. The other kits linked, similar prices or less?

You can't go wrong with any of Shannon's designs. In the Budgie, the EL84s are wired for UL mode. EL84 tubes are 12W tubes, not 25W tubes, so you get about 1/2 the audio output wattage in UL mode relative to EL34s.

[coolhandjjl]

Okay- back to EL34's. What do you think I will end up spending to build two stereo EL34 SE amps, a SET and a SEPUL as mentioned earlier?

[kheper]

Okay- back to EL34's. What do you think I will end up spending to build two stereo EL34 SE amps, a SET and a SEPUL as mentioned earlier?

With 2 stereo amps, you'll need 2 power transformers, 2 chokes, 2 chassis, etc.

No idea what the final price will be. It depends on the prices of the outputs, coupling and filter caps, chassis, etc.

[coolhandjjl]

Looks like I may be leaning towards the Clementine for my midrange horn. It's 6L6, I believe it can be configured in strapped triode mode. I think it will have enough power as is. If it's adequate enough for full range systems, it should more than enough for a mid horn 400~6kHz whose driver is rated at 108dB/m. If I'm careful selecting parts, it would be affordable.

I saw a kit from Decaware, the Zen Kit #1 Triode SET that could work for my high frequency horn/driver. Less power than the above for less cost as well.

[EWBrown]

I saw a kit from Decware, the Zen Kit #1 Triode SET that could work for my high frequency horn/driver.
Less power than the above for less cost as well.

I built up a clone of the Zen, SET and it is, well, "OK" at best. The OPTs are the cheapest of the cheap small Edcors, which have wire leads,
rather than the solder / push-on tabs.

The GXSE10-8-5Ks as used in the SE Budgie are a definite step up from the cheapie OPTs.
The ZEN also runs the EL84s / SV83s very hard, while the Budgie respectfully treats the tubes a lot more gently.

The Budgie SE would be a better bet for you, I built mine without the headphone output jack and resistors, which would also be unnecessary
for use as a tweeter amp.

HTH

/ed B

[coolhandjjl]

Every suggestion helps!

I was considering two Clems, one as the 6L6 strapped triode version for the mids (not sure about UL), and the Darling version for the tweets. That way, I also get a feel for the 1626 SE sound. But if a the EL84 Budgie would be better for the tweets than a Darling, I'm all ears.

[EWBrown]

Depending on our tweeters' PL ratings, either the Clementine SET (750 mA per channel) or the Budgie SE (2.5WPC) would be suitable.
The Zen would score distant third place here....

I cloned a zen several years ago, I got two of the chassis and small parts kits for a zen, without the iron, for a silly cheap price.
I looked it up and found the decware website, ordered a pair of the OPTs and used a Hammond 272FX for power. I had to change some parts, the 1/2 watt 47K plate resistors for the 6N1P were definitely stressed in the circuit, and would have died prematurely. I used 2W metal film resistors, they were OK. The original coupling caps were el-cheapo mylars, I upgraded them to Auricaps, for what it was worth.

It sounded "OK", but not really great, as compared to Doc Bottlehead "sex" amps, varuous 6EM7 and 13EM7 SETs, etc. The Decware OPTs were the very
cheapest Edcor open frame 5W OPTs, 9600 ohms primary, 6 ohms secondary. They cost me about 2X what Edcor should have charged for them directly.

/ed B