At the end of my many page reading around an EL34 SE schematic I am still very confused as to which schematic I should use to have a very good non ultralinear amplifier with about 5 or 6 watts. I already have 2 ISO (ISO Tango) FC-12S output transformers and would like to use these. I would have liked to have bought a pcb from Tubelab, but George doesn't ship to Italy.
My loudspeakers are Troels Gravesen's PMS (... but my room is small and I don't listen at high volume). The source is Cocktail audio X14).
Any advice would be greatly appreciated
Domenico
My loudspeakers are Troels Gravesen's PMS (... but my room is small and I don't listen at high volume). The source is Cocktail audio X14).
Any advice would be greatly appreciated
Domenico
Just curious why non-ultralinear? It looks like this transformer has screen taps, and I feel ultralinear amps are a good balance between triode strapped and pentode modes of operation.
Anyway, here is a SE amp I came up with using 6SQ7 tubes for the drivers and it works great with a 5K OT. It's simple, with a low parts count and nothing really radical about the design. I suppose you could just triode strap the EL34 if you really are opposed to ultralinear operation? Several other people have built one, and everyone who has seems to agree it sounds nice. I love mine 🙂
https://www.skunkiedesigns.com/6sq7
Anyway, here is a SE amp I came up with using 6SQ7 tubes for the drivers and it works great with a 5K OT. It's simple, with a low parts count and nothing really radical about the design. I suppose you could just triode strap the EL34 if you really are opposed to ultralinear operation? Several other people have built one, and everyone who has seems to agree it sounds nice. I love mine 🙂
https://www.skunkiedesigns.com/6sq7
On the paper of this trafo there is the connction for the UL tap.
The max current permissible is 80 mA max.
An EL34 cunfigured as UL can do the job with a better efficency than triode mode
The only thing is to set the proper impedance as listed on paper. Try to 3,5 kohm or 5kohm
One solution can be a SRPP of ECC81 that can drive the EL34 with a fixed bias at 320 Vdc ( p.e.) and 60-65 mA as bias
The max current permissible is 80 mA max.
An EL34 cunfigured as UL can do the job with a better efficency than triode mode
The only thing is to set the proper impedance as listed on paper. Try to 3,5 kohm or 5kohm
One solution can be a SRPP of ECC81 that can drive the EL34 with a fixed bias at 320 Vdc ( p.e.) and 60-65 mA as bias
On this, yeah you can use 3.5K or 5K with a UL EL34. This trafo varies the primary impedance via the secondary taps chosen. It might make sense to bring out both of the taps that will change between 3.5K and 5K with your speaker load onto the external speaker terminals so you can see which sounds better with your speakers. The 3.5K will make a little more power, the 5K will have a little less distortion.
Why not make a Tubelab SSE on turret boards or point to point? All the information is on George's site? It's a pretty simple circuit.
http://tubelab.com/designs/tubelab-sse/
http://tubelab.com/designs/tubelab-sse/
@novanta00
please, this is an English speaking forum and you have to stick on English for communications, also because otherwise other people do not understand you.
please, this is an English speaking forum and you have to stick on English for communications, also because otherwise other people do not understand you.
I have lately been tweaking with this schematic. Seems to work well with many 6L6-family tubes and also with EL34.
Output power is some 8 W with 6P3S-E and 10 W with EL34.
GNFB = 10 dB and "Schade" = 3 dB, total 11 dB.
Interesting feature with 6P3S-E is that adding 3 dB Schade NFB, reduces THD 6 dB.
Output power is some 8 W with 6P3S-E and 10 W with EL34.
GNFB = 10 dB and "Schade" = 3 dB, total 11 dB.
Interesting feature with 6P3S-E is that adding 3 dB Schade NFB, reduces THD 6 dB.