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 .
Thanks @huggygood !I used to be Project / R&D engineer, notably for years at ALSTOM. Designing prototypes of all kinds was my speciality.
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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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.
T
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...
T
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.
Attachments
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...
T