Transformer coupled 6AS7/6080

[p_ete2003]

check this site:
http://www.audiokit.it/ITAENG/KitEle...t/Lilliput.htm

I've made this amp. It's a cheap but good sounding amp for high efficiency speakers.

The PS I used:

[Yvesm]

Somewhat similar, almost fixed bias



Yves.

[Shoog]

If your still interested in a 6080 amp, I could share my experiences of building a PP one with toroidal mains transformers as interstagers. Mains toroidals for outputs. Driven by a partial feedback ECL82. Hard to drive tubes in this configuration.
Definately consider CCS for the output cathodes - makes life simpler, but they need bypassing.
Been running reliably now for about 7 months. Sounds really good. Beats my RH807 by a long margin (though that tempting to listen to).

Let me know.

Shoog

[jarthel]

Originally posted by Shoog


Let me know.

Shoog

interested.

also could you show the mods needed to use CCS and what is the CCS output?

thank you very much

[Shoog]

The CCS I have used are based on LM317's. More than adequate for the appllication (sound quality is all down to the bypassing). A very good write up can be found over at tubecad. I used one LM317 for each cathode, this eliminates the need for bias adjustment. Its a technique that is used in the Vacume State high end amps.

Shoog

[jarthel]

Originally posted by Shoog
The CCS I have used are based on LM317's. More than adequate for the appllication (sound quality is all down to the bypassing). A very good write up can be found over at tubecad. I used one LM317 for each cathode, this eliminates the need for bias adjustment. Its a technique that is used in the Vacume State high end amps.

Shoog

could you share the schematic of the amp and the related tubecad CCS circuit?

can you also point where/what parts are replaced by the CCS?

also what's the required current output of the amp?

thanks again

[jayme]

Do all of these schematics require the 6080 to be internally matched?

I have a pair of 6080s here that I'd like to turn into a nice, small monoblocks. But I am pretty sure they don't have internally matched sections...

[Shoog]

The beauty of placing seperate CCS 's in each cathode is that it allows you to tightly control the static current going through the two triodes in the PP pair. Hence no need to match the triodes, and no need to adjust the bias because it finds its own bias point to pass the current which the CCS is forcing through it.
Things are obviously not perfect because the triodes are not matched and they will therefore have slightly different responses and hence the two sides of the PP waveform will be slightly different. This will lead to a smudging of the combined waveform.
My personal experience is that this is a very small issue - far outweighed by the benefit of current balance in the output transformer. The sound is clean and clear to a quite unexpected degree. I would use this technique in any future project, PP or SE.

I have my 6080 tubes set to pass 100mA at about 100V plate to cathode. Bias settles to about 28V. This Allows you to use easily availble mains toroidals as output transformers. I have had no failures since the initial testing phase, and can see these tubes running for years at a time.

Here is a link to the Tubecad article and I will attempt to post a schematic.

http://www.tubecad.com/february2000/page6.html

Unfortunately all the schematics i drew up are from the work in progress stage and won't be totally accurate.

Shoog

[Shoog]

Here it is.

By the way - no hum.

Shoog

[jarthel]

Originally posted by Shoog
Here it is.

By the way - no hum.

Shoog

any alternative to ecl82 in octal mounting?

thank you.