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[IslandPink]

If it's any consolation it took me three goes to get all the bits for the tweeter amp.
Those STC's do look very fine.

[Cressy Snr]

If it's any consolation it took me three goes to get all the bits for the tweeter amp.
Those STC's do look very fine.

Yes, the STC 13E1 sure is a great looking valve, especially when lit up. Now that I know a bit more about building amps, I'm sure they'll work beautifully configured as SEOTL power valves. I'm off to a good start with this as Wolfgang already has a working 6C33C amp. The 13E1, when triode strapped, isn't that different from the Russian valve, so I'm quietly confident, that with the help I've had so far, from Wolfgang and Ray, there is no reason for the amp not to be a success.

[Mike H]

If it's any consolation it took me three goes to get all the bits for the tweeter amp.
Those STC's do look very fine.

And then there was the time I made up a RS order, then waited a week for it to arrive.

My shopping basket web page was still waiting for me to click the Submit button.

[IslandPink]

That's like Harry Hill, where he sat in front of the telly and it turned out he done a 'double push' on the switch.

[Ray P]

Those STC's do look very fine.

They do look nice don't they, much more 'elegant' than 6C33Cs.

[Ali Tait]

Hi Wolfgang, sent you a PM, have you seen it?

[Cressy Snr]

The rest of the components have now arrived, so this weekend might produce some music. Either that or a big bang!

[Mike H]

So, either ear trumpets or steel helmets!

Have both near at hand...

[Ray P]

The rest of the components have now arrived, so this weekend might produce some music. Either that or a big bang!

Looking forward to seeing how his progresses Steve.

[RhythMick]

Interesting that Jac van de Wald has something to say about this tube, he normally knows what he's talking about.

http://www.jacmusic.com/techcorner/ARTI ... -Index.htm

[Wolfgang]

My main concern would be the amp. factor of 4,5. I don’t think you can operate the 13E1 exactly like the 6C33 without getting distortion at the dynamic peaks of moderate input levels already. It’s not100% clear to me if B+ 150V is after voltage drop or if it’s simply the B+ from the psu without load. In case of distortion at moderate levels I would increase Ip or B+ (if you can) but definitely not NFB to more than what you have already calculated in order to get down to the output impedance which you need for driving your speakers. Ideally you would check the output with a scope and adjust Ip/B+ for lowest distortion and highest possible gain at the output while keeping the input of the amp at the ideal level for the source (DAC etc) you plan to use..
To use a tetrode as triode gives you some extra headroom for the power load line. This tube has so much headroom compared to the 6C33 that I see no problem in this respect.

[Cressy Snr]

My main concern would be the amp. factor of 4,5. I don’t think you can operate the 13E1 exactly like the 6C33 without getting distortion at the dynamic peaks of moderate input levels already. It’s not100% clear to me if B+ 150V is after voltage drop or if it’s simply the B+ from the psu without load. In case of distortion at moderate levels I would increase Ip or B+ (if you can) but definitely not NFB to more than what you have already calculated in order to get down to the output impedance which you need for driving your speakers. Ideally you would check the output with a scope and adjust Ip/B+ for lowest distortion and highest possible gain at the output while keeping the input of the amp at the ideal level for the source (DAC etc) you plan to use..
To use a tetrode as triode gives you some extra headroom for the power load line. This tube has so much headroom compared to the 6C33 that I see no problem in this respect.

Hi Wolfgang,
The 150V of HT at one amp draw is a conservative estimate of the voltage under full load. The main toroid is capable of 500W per winding. I would obviously have liked around 170V (85W diss per tube at 500mA each) but this is not possible with the transformers I have, so 150-155V it has to be I'm afraid.

[Cressy Snr]

Latest bit of progress:

Makeshift heatsinks made of rectangular section aluminium can be seen, with the TL783s attached, with the Electrolube heat conducting, two part, epoxy adhesive I used on my NVA clone solid state amp. I have another four TL783s in case of problems. These will be used when the proper heatsinks arrive and if the breadboard is worth converting to a proper amp.

[Nick]

Would have thought they would have been better spaced apart so the heat sources were not in the same place.

[Cressy Snr]

Would have thought they would have been better spaced apart so the heat sources were not in the same place.

I knew that was coming.
The lengths of ali section can be spaced apart, as each reg is on its own piece of metal.
That's a job for tomorrow now.

Trouble with this thing, is that people who know more about OTLs than me seem to be having doubts whether it'll be much good. Typical Cressy Senior not enough gain/drive, wimpy output scenario is being postulated by those in the know if I'm not mistaken and maddeningly there's bugger all I can do to rectify that; not with with the hardware I'm lumbered with anyway.