In May 2020, I originally opened that thread, but that project lagged sooo much that it is now closed :
https://www.diyaudio.com/community/threads/the-ultimate-kt120.354842/
So I reopen it, my apologies... 🙄
The project is now under construction - I hope to end it before the end of 2023 :
The lateral chassis plate already gives some clue :
More detailed pictures to come, au fur et à mesure... 😉
https://www.diyaudio.com/community/threads/the-ultimate-kt120.354842/
So I reopen it, my apologies... 🙄
The project is now under construction - I hope to end it before the end of 2023 :
The lateral chassis plate already gives some clue :
More detailed pictures to come, au fur et à mesure... 😉
If it's not indiscreet, what is your job in real life?
I am always impressed by your sense of method . 😳
I am always impressed by your sense of method . 😳
😆 😆 😆 Thanks @huggygood !
I used to be Project / R&D engineer, notably for years at ALSTOM. Designing prototypes of all kinds was my speciality.
T
Wiring is finished - now I have to install RC components on the board :
T
T
End of the work - finally !
Measurements and final setup :
The power output reaches 10.00VRMS on 8R output / 8R load, that is to say 12.5WRMS, the onset of clipping being between 13 and 14WRMS.
The bandwidth at 10.00V / 12.5W is :
@-1dB 16Hz - 23kHz
@-3dB 10Hz - 40kHz
The bandwidth at 2.83V / 1W is :
@-1dB 7Hz - 23kHz
@-3dB 4Hz - 42kHz
The Ri measured on the 8R output is 2.36R, giving a damping factor of 8/2.36 = 3.39
The FB line is circa 6dB (5.5 to 6dB depending on the input sensivity calibration adjustment, done via the FB at 800mV in ---> 10.00V out)
I have no means to measure distorsion for the moment, but by my experience, I estimate it to be circa 2-3% at maximum output power.
Pictures...
T
Measurements and final setup :
The power output reaches 10.00VRMS on 8R output / 8R load, that is to say 12.5WRMS, the onset of clipping being between 13 and 14WRMS.
The bandwidth at 10.00V / 12.5W is :
@-1dB 16Hz - 23kHz
@-3dB 10Hz - 40kHz
The bandwidth at 2.83V / 1W is :
@-1dB 7Hz - 23kHz
@-3dB 4Hz - 42kHz
The Ri measured on the 8R output is 2.36R, giving a damping factor of 8/2.36 = 3.39
The FB line is circa 6dB (5.5 to 6dB depending on the input sensivity calibration adjustment, done via the FB at 800mV in ---> 10.00V out)
I have no means to measure distorsion for the moment, but by my experience, I estimate it to be circa 2-3% at maximum output power.
Pictures...
T
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Nice amps! Are the grey hammer coated transformers from Tube Town, Germany?
Thanks @Fuling ! 🙂
Yes, they are - ref N° tt-maj-50-pw.
The output transformers are from China, unknown manufacturer, coming from a BOYUU-REISONG A-20 KT88 amplifier.
Listening tests this evening...
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Looking good!
I have a PT and an OPT from Tube Town in a yet to be finished 807 monoblock. The quality seems reasonable for the price so Im about to order some more iron from the same series for some future projects.
I have a PT and an OPT from Tube Town in a yet to be finished 807 monoblock. The quality seems reasonable for the price so Im about to order some more iron from the same series for some future projects.
Yes, these transformers are made in Eastern Europe - possibly by ISKRA or NUVOTEM ? - and the quality is perfect - at least for the power transformers, since I have not tested their output transformers for the moment.
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Does not exist anymore - they were something like local Siemens and a lot of things they made were maked under licence from Siemense & Altec.
They had their own products like fim capacitors, telephone repetear coils ( 1:1 transformers ) and so many other things i could not possibly made a list.
Of importance, if You ever see their amps - they were made for theaters ( EL34 PPs, one channel per chasis ) and are considered good enough to be restored or their transformers used for some new power amp project.
They also made loudspeakers - Altec VOT's, under licence, but the midbass driver was 14" unit licenced from Siemens ( From Klangfilm basically ), with some changes possibly.
The amps :
https://www.diyaudio.rs/choky/Iskra_cinema_gear.html
The PT I bought from Tube Town makes a bit of mechanical noise but it was easily cured by putting it on rubber dampers. Now I'm about to buy a pair of their 2,5k-5k/4-8-16R SE OPTs to see if they're good enough for hifi. At just over 60 Euros a piece it's worth a shot and they have the right look for an upcoming project.
Interesting @Fuling 😎
Would you let me know the reference of these OPT transformers, or a link to them ?
Thanks ! 😉
T
Sure ISKRA was a major electric/electronic company in the East countries - I thought they were still in activity.
One of my first MM was an ISKRA Unimer III :
I would probably still have it if it was not stolen with my toolbox long ago... 😡
I found this here in France on a local Craiglist :
I think that my undestructible OPEL Corsa from the late 80s had an ISKRA starter... 🙂
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Here: https://www.tube-town.net/ttstore/outputtransformer-se-2k5-5k-4-8-16.html
I'm about to build an amp with RCA 808 as output tubes, and these transformers should be a decent match.
I'm about to build an amp with RCA 808 as output tubes, and these transformers should be a decent match.
The midbass is locally used as a wide-band driver, Zen Mod has done speakers with them.
The prices has gone up recently.
Using their 1:1 600R transformers at the output of the Pavouk DAC ( AD1865 NOS ), little rough comapred to some locally wound transformers but for the price of 20 Eu per piece they are alright.
🙂
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Ah yes, I see : it's the Project G5 transformer. It's not Hi-Fi, it's for guitar, but it may be convenient, nonetheless.
Anyway : good idea ! Let us know if they work fine...
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True, they are guitar amp transformers. If they're not good enough for hifi, I'll have an excuse to build two more guitar amps 😀