Spuddo more powerfull

[Jaime]

When I read about THE SOUND OF AN ONLY TRIODE in the Thorsten Leach article (Some thoughts about singleended Valve Amplifiers) I was astonish
smile. The Gordon Rankin Wavelength flea powers also are in the line...

Then I see the BrianClarck's Spuddo and I think this little SET will be my amp !!!
But only 1.5w output is very bad for my 95dB loudspeakers.
You know another Spuddo, with other tube more powerfull?
And please not very expensive (RS-241….), that I can’t afford!!!

Best regards Jaime

 

[arnoldc]

But the Wavelength is not a "spud" amp. I think the description of a spud amp, is single stage, single tube.

I have a spud amp, a WE417A (5842), but it won't have juice for your speakers.

 

[Sheldon]

Here's a 7W design: http://home.att.net/~abraxasaudio/projects/6197info/kit.html, but it uses a pentode. You can get about the same wattage with a triode in PP, like this one: http://www.pmillett.com/el802_spud.htm


Sheldon

 

[Sherman]

While it isn't strictly a 'spud' amp (single tube for both the input stage and output stage IIRC) Mikael's SE KT88 will give you 6 or 7 watts and is very simple to build. KT88 tubes can be pricey but Valve Art can be had for $25 US or less.

You can also get about 4.5 watts from a SE EL84 in pentode mode. Again it isn't a true spud amp but simple to build and can be quite small. In fact I'm currently building a PP EL84 stereo amp on a Hammond 12"x10" chassis. (That one should be good for may 12 watts.)

 

[Jaime]

The one triode sound, the Grial.

Thanks boys

Arnold, I agree the spud is is a single stage amp. The one triode sound, the Grial.

The Wavelegth Mercury Series are (or was?) one only triode amps. But the RS241 and VVT20SL tubes are very expensive and difficult to obtain. And the WE437A very small power.

http://www.wavelengthaudio.com/Mercury.pdf

In the web are many 6C45pi (1.5w) similar power amps.

Sheldon. There are a nice 5w EL84 posted in the Magnequest Forum, but it’s pentode and I like a SET.

http://www.audioasylum.com/forums/magnequest/messages/426.html

Best regards Jaime

 

[dsavitsk]

You might look into the Emission Labs 20a, 20b, and 30a.

http://www.emissionlabs.com/datasheets/EML20B.htm

Another solution is to use a step up transformer to drive your output tube. Here's a 300B "spud" http://electra-fidelity.com/silversignatue.aspx

 

[arnoldc]

Hi Jaime, thanks for the Mercury link.

That would be a really nice project right? How about that 300B spud amp that dsavitsk posted.

 

[wrenchone]

The 6HV5A is a specialized beam triode for pulsed HV regulation in color TVs. It has a gain of 300, so would qualify for spud service. It also has a 35W plate dissipation rating. Minuses are a plate characteristic that will require high plate voltage or forward biased grid to extract the goodies. Do a search, as I think some other folks have tried it as a spud.

 

[Jaime]

Hi boys:

Arnoldc, I think the EL84 post by Gordon Rankin in the forum is the Mercury’s brother. Both are Gordon Rankin design and in the single stage philosophy. Looking at the EL84 schema we can imagine the unknown Mercury schema, input multiplier choke, twin chokes power supply, etc.
Different the paraffed output.

Dsavitsk, Interesting the Electra-Fidelity 300B but I believe it have an input OP preamplifier. Do you think?
http://electra-fidelity.com/sea26a3.aspx

Wrenchone, the 6HV5A have a lot of possibilities. You was working in this?

Best regards Jaime

 

[wrenchone]

I plan to use some 6HV5As in an amp someday, but not as a spud. If you search the tube forum for "6HV5", you'll see a sample schematic of a spud application of this tube.

 

[arnoldc]

Thanks Jaime, I've seen that amp of GR, very interesting and is a nice other project.

 

[Jaime]

Arnoldc.
GR in the forum break some myths: the EL84 SE amp is pentode, NFB (small) and stereo (one only very good PS).
In W he has triodes, brand tubes , no NFB, DHT, monobloques…. All marketing?
Best regards Jaime