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#376 Re: Remember These?
Posted: Mon Jan 14, 2019 12:48 pm
by Cressy Snr
Well the OTL has now left the room and is awaiting it's turn to go in a box, so it's Ray's project that's now the focus of attention.
I'll stick a schematic up as soon as I can be arsed to work it out for 6H30pi
#377 Re: Remember These?
Posted: Mon Jan 14, 2019 1:12 pm
by Mike H
Watching.
#378 Re: Remember These?
Posted: Mon Jan 14, 2019 5:19 pm
by Irene Idler
Steve's amp really does sound amazing! It did very nice things for some of our favourite records. Those valves *seriously* need the full steampunk treatment though!
#379 Re: Remember These?
Posted: Mon Jan 14, 2019 5:39 pm
by Cressy Snr
Irene Idler wrote: ↑Mon Jan 14, 2019 5:19 pm
Steve's amp really does sound amazing! It did very nice things for some of our favourite records. Those valves *seriously* need the full steampunk treatment though!
Oh yes they are definite candidates for the full steampunk look. I have plans afoot for
two steampunk amps actually.
My 1950s 13E1s do
not like OTL operation, so they're no good as spares. I need the 1960s and later, four-cooling-fin ones for OTL amp backups. So the '50s ones will be built into a 'normal' valve amp at some point. Plan is for same front end but one OTL and one with OT. Should be an interesting way to compare both modes. Steve S suggested this idea when he sold me the valves. If I've managed to build both in the next six months (OTL the priority) It'll be interesting to compare them at Owston.
#380 Re: Remember These?
Posted: Mon Jan 14, 2019 6:49 pm
by Ray P
Cressy Snr wrote: ↑Sat Jan 05, 2019 4:59 pm
One more time!
Steve, apart from changing to the 6H30pi and using the same power supply for driver and output stages (with the commensurate component value updates) is this your final schematic? Cheers
#381 Re: Remember These?
Posted: Mon Jan 14, 2019 6:56 pm
by Cressy Snr
Ray P wrote: ↑Mon Jan 14, 2019 6:49 pm
Cressy Snr wrote: ↑Sat Jan 05, 2019 4:59 pm
One more time!
Steve, apart from changing to the 6H30pi and using the same power supply for driver and output stages (with the commensurate component value updates) is this your final schematic? Cheers
Yes for dual power supply. If you are using the 6SN7 Aikido front end, you'd need the 300 odd Volt HT anyway wouldn't you?
The schematic for the 6H30pi front end will be along before the end of the week.
#382 Re: Remember These?
Posted: Mon Jan 14, 2019 10:22 pm
by Ray P
Yes, based on my limited grasp of the electronic theory pertaining I think that retaining the 6SN7 front end will entail the higher voltage supply for it. My thinking therefore is to reserve the 6SN7 stuff I already have for a 6C33C project usinng Wolfgang's schematic and to follow your lead for the 13E1 amp.
#383 Re: Remember These?
Posted: Tue Jan 15, 2019 10:07 am
by steve s
Cressy Snr wrote: ↑Mon Jan 14, 2019 5:39 pm
Plan is for same front end but one OTL and one with OT. Should be an interesting way to compare both modes. Steve S suggested this idea when he sold me the valves. If I've managed to build both in the next six months (OTL the priority) It'll be interesting to compare them at Owston.
That sounds a good project Steve, one which would really interest me... the capability of different valves and the damage paralleling them can do to the resulting sound is in my view much worse than a good output transformer inflicts. The draw back is the cost of a good transformer for the 13e1, those Hammonds thicken the bass and the sound compared to my transformers ... (Subtle differences) so would show the otl sound in better light in direct comparisons I would like to think the ultimate sound quality is not that far apart... from what I've heard so far But I have an open mind.. and may well find myself looking for a pair of those big valves.
#384 Re: Remember These?
Posted: Tue Jan 15, 2019 2:37 pm
by Cressy Snr
Can't let a good breadboard go to waste, so have lashed an amp up using the 50s 13E1s, with output transformers:
Not as good as the OTL, but the same overall 13E1 kind of presentation.
The valves are only running 100V and 113mA as the 1627SE OPTs will only take 150mA max. There is room for increasing the current a bit, but it's doubtful it would change anything soundwise.
Trouble is, once you've heard a single tube OTL, your reaction to anything else is often, "well it's very good....but..."
Still a good amp though.
This one can be the comparison with the boxed up OTL at Owston.
#385 Re: Remember These?
Posted: Tue Jan 15, 2019 3:07 pm
by pre65
Cressy Snr wrote: ↑Tue Jan 15, 2019 2:37 pm
This one can be the comparison with the boxed up OTL at Owston.
Have you got enough transformers to do both ?
#386 Re: Remember These?
Posted: Tue Jan 15, 2019 3:07 pm
by jack
Really hoping to make Owston to hear this! Been (passively) following since the start - great project.
#387 Re: Remember These?
Posted: Tue Jan 15, 2019 3:09 pm
by Wolfgang
I am really tempted in the meantime to try something with this 13E1 (NOS from the 1960 or later ?) myself. Just starting with one tube for experimenting. The biggest limitation with the 6C33 was the 60W max which was easily reached with 470mA/130V and the necessary min peak output power even for 15R speakers. With the 13E1 there is an open field for experiments with completely different driver stages (different tubes, simplified single triode per channel, different circuits than plate follower) and at higher voltages. I couldn't find any grid characteristics for triode mode operation for the 13E1 but I think with CCS it's not that important and I am planning anyway to use a variac with DC output up to 450V to find out about the sound if there is any difference at all at different voltages or if there is a true "sweet spot" for this tube in combination with different driver stages/tubes.
When I fine tuned the 6C33 OTL for best sound/highest possible voltage/current I watched the signal at the grid of the 6C33 together with the signal at the loaded output and adjusted NFB for least distortion of the output for max input signal which I planned to use. When I listened to these ideal adjustments I had to change the NFB again in order to get best sound in my listening room. It was a compromise between output power and best sound but the final output power was still more than enough. I can play the C-horns louder than I could/would ever want to listen. No distortions, no clipping like with the 300B SE OTLs with certain recordings at peak dynamics, although they run even at a little more than 500mA with my adjustments. Interesting how numbers don't tell anything about amp/speaker realities. Will be an interesting year.
#388 Re: Remember These?
Posted: Tue Jan 15, 2019 3:22 pm
by Cressy Snr
pre65 wrote: ↑Tue Jan 15, 2019 3:07 pm
Cressy Snr wrote: ↑Tue Jan 15, 2019 2:37 pm
This one can be the comparison with the boxed up OTL at Owston.
Have you got enough transformers to do both ?
I think I've another 2x115V somewhere, so hopefully yes.
#389 Re: Remember These?
Posted: Tue Jan 15, 2019 3:24 pm
by Cressy Snr
jack wrote: ↑Tue Jan 15, 2019 3:07 pm
Really hoping to make Owston to hear this! Been (passively) following since the start - great project.
There'll be a veritable gaggle of OTLs there, so you'll have plenty to choose from if Ray and Dave (Thermionic Idler) get their projects done in time.
#390 Re: Remember These?
Posted: Tue Jan 15, 2019 3:27 pm
by Cressy Snr
Wolfgang wrote: ↑Tue Jan 15, 2019 3:09 pm
I am really tempted in the meantime to try something with this 13E1 (NOS from the 1960 or later ?) myself. Just starting with one tube for experimenting. The biggest limitation with the 6C33 was the 60W max which was easily reached with 470mA/130V and the necessary min peak output power even for 15R speakers. With the 13E1 there is an open field for experiments with completely different driver stages (different tubes, simplified single triode per channel, different circuits than plate follower) and at higher voltages. I couldn't find any grid characteristics for triode mode operation for the 13E1 but I think with CCS it's not that important and I am planning anyway to use a variac with DC output up to 450V to find out about the sound if there is any difference at all at different voltages or if there is a true "sweet spot" for this tube in combination with different driver stages/tubes.
When I fine tuned the 6C33 OTL for best sound/highest possible voltage/current I watched the signal at the grid of the 6C33 together with the signal at the loaded output and adjusted NFB for least distortion of the output for max input signal which I planned to use. When I listened to these ideal adjustments I had to change the NFB again in order to get best sound in my listening room. It was a compromise between output power and best sound but the final output power was still more than enough. I can play the C-horns louder than I could/would ever want to listen. No distortions, no clipping like with the 300B SE OTLs with certain recordings at peak dynamics, although they run even at a little more than 500mA with my adjustments. Interesting how numbers don't tell anything about amp/speaker realities. Will be an interesting year.
Hi Wolfgang. I advise the 60s/70s tubes with the multiple cooling fins on the plates. These laugh in the face of half an amp at 160V. The older ones get glowy plates at that power, so avoid those. Guess how I know.