New SE With Triode Mode KT120/150

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Cressy Snr
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#121 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Spent time today dismantling the Super Rocky. Where once I had a working amp, I now have a pile of chokes and transformers.
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IslandPink
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#122 Re: New SE With Triode Mode KT120/150

Post by IslandPink »

Awww... poor Super Rocky ! :(
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pre65
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#123 Re: New SE With Triode Mode KT120/150

Post by pre65 »

Cressy Snr wrote: Thu Jul 09, 2020 9:01 pm Spent time today dismantling the Super Rocky. Where once I had a working amp, I now have a pile of chokes and transformers.
Yeah, I had that when I dismantled two 50W mosfet amps. Even though MoFo is on the home straight there are still a lot of bits left over.

Looking forward to seeing the finished article Steve. :)
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Paul Barker
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#124 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

Well Barbaric nearly morphed into a Matrix. But it’s not home and dry. If the GK71 Matrix is as hoped, I’ll have to adapt Barbaric. To which end I’ll rig up a socket in each amp to land the Lundahl output transformers on the amp I’m playing.
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Cressy Snr
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#125 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Today, I am mostly: scraping meticulously, the paint from the large mains transformer end-bells. Got one done. It’s an hour’s work to do each one. Could have gone out and bought chemical stripper of course, but I’m from Yorkshire. :mrgreen:
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pre65
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#126 Re: New SE With Triode Mode KT120/150

Post by pre65 »

Cressy Snr wrote: Fri Jul 10, 2020 11:11 am Today, I am mostly: scraping meticulously, the paint from the large mains transformer end-bells. Got one done. It’s an hour’s work to do each one. Could have gone out and bought chemical stripper of course, but I’m from Yorkshire. :mrgreen:
There's a joke there Steve, but I'm far too polite. :lol:

The devil is in the detail, which is why your builds are so good. :)
The only thing necessary for the triumph of evil is for good men to do nothing.

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Cressy Snr
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#127 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

pre65 wrote: Fri Jul 10, 2020 11:15 am There's a joke there Steve, but I'm far too polite. :lol: .....
Yes you have to be very careful how you describe transformer covers, :lol: :lol:
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Cressy Snr
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#128 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Iron is all mounted, both inside and out. So it’s definitely time for the traditional photo, giving an idea of of what it will look like when it’s finished:
74A97A33-0089-4E42-93F0-31FD272C9432.jpeg
I’m pleased with the aesthetics. And it doesn’t sag. :)
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#129 Re: New SE With Triode Mode KT120/150

Post by steve s »

Looks great steve..
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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#130 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Yesterday and today’s progress:
E7A44F64-93A5-4828-B7BC-1CE9F763C946.jpeg
Mains is all done, all tag strips terminated and the DC heater module has been pre set for 4V.
Heater wiring, busbars and power supplies next, but I have a washing machine to fit tomorrow, so how much will get done on the amp I don’t know.
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Ray P
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#131 Re: New SE With Triode Mode KT120/150

Post by Ray P »

Cressy Snr wrote: Fri Jul 10, 2020 8:19 pm And it doesn’t sag. :)
Gravity always wins - look in the mirror!

Anyway, good progress Steve and a neat job.

Have you given up on the 13E1?
Sorry, I couldn't resist!
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#132 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Yes, I’m afraid the 13E1 SEOTL is history.

The thing sounds wonderful, but really needs 16 Ohm speakers to be of much practical use. Nick measured it at 600mW into an 8 Ohm load before the distortion shot up; that’s less power than one of those ‘Darling’ amps. Should have thought on while we were at it, to have measured it at 16 Ohms. I suspect the power would have easily tripled.

Wolfgang and yourself have much more suitable speakers than I have, both in terms of efficiency and impedance, so the SEOTL concept has a far better chance, with your systems.
I started the build to try to prove to myself that I could design and build an OTL and not have it catch fire or explode. I succeeded with that and I’ve had a real taste of what an OTL is capable of. I wouldn’t have missed that experience for the world. OTLs are a unique sound.
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#133 Re: New SE With Triode Mode KT120/150

Post by Wolfgang »

Nick measured it at 600mW into an 8 Ohm load before the distortion shot up
Did you try to reduce the NFB? There is a sweet spot with max. power and ideal NFB with these OTLs. You don't need to adjust for lowest DF but for ideal DF that works best with your speaker /amp combo. Sounds also so much better.
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Ray P
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#134 Re: New SE With Triode Mode KT120/150

Post by Ray P »

Sorry to continue the off-topic diversion Steve...

I understand where you're coming from with the 13E1. The 13E1 with my 150hm Lowther horns continues to delight me and gives me a better balanced sound than the 300B SE-OTLs, not quite as sweet at the top but a much more full-bodied sound, however, I'm conscious that I have very little power to play with and, as I've mentioned before, that has given me something of a quandry regarding the Lii Audio speakers - to use the Lii units I think some more power will be required. With the results I now have I'm seriously thinking of sticking with the Lowthers, or do I build a MoFo or Mellow OTL to drive the Lii units? I've almost finished the 6C33C SE-OTL too, just to add more variables into the mix.

It might be interesting for you to try a MoFo (or, less likely, something like a Mellow or Transcendent Pinnacle) with your speakers to give a flavour of what more OTL Watts might do with them?

Anway, back to your project at hand...
Sorry, I couldn't resist!
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#135 Re: New SE With Triode Mode KT120/150

Post by steve s »

I've a single nos philips 9710a driver (800 ohm) been looking for a second for years, if I was building an otl i would be based on that driver, most of the philips full range drivers have a good sound.
I did wonder about winding speaker coils.. I have all the stuff I need to do it, but I've so many other things on.

Good progress Steve... I'm sure
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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