I have tried my 4 ohm speakers with a LL1627 OPT. It has only a connection for 8 ohm speakers and 2K3 primary. This lacks bass on my 4 ohm speakers. I also have a transformer with 3K primary and a 4 ohm secondary. Can I use this on my KT88se or does this rather high primary impedance result in bad effects on soundquality ?
thanks,
Jaap
thanks,
Jaap
Whilst generally in agreement wrt relected impedance (the KT88 will have an rp of around 1k), the quality of the alternate 3k trans will be a bigger determinant on SQ than the turns ratio. The Lundahl has 60H of primary L and low capacitances. What does the other one have? A manufacturer and model number (or better yet a datasheet) would be a help in making a more decisive comment.
Re: se KT 88 triode mode with 3K5 transformer
Can you post the circuit, or details of it, as well as what speakers you're driving? Perhaps someone can then suggest what might be the peoblem and a possible solution.
Jaap said:It was triode mode.
I tried the Amplimo = Plitron 3K5 toroid transofrmer and i must say that I am still not satisfied with the bass. I suppose the mismatch is still too big (?).Jaap
Can you post the circuit, or details of it, as well as what speakers you're driving? Perhaps someone can then suggest what might be the peoblem and a possible solution.
circuit kt88 se
12hg7 (triode mode) with 20 mA is driver, into LL1660/10 mA (1:2) primaries parallel, into KT88 with 400 volt and I suppose about 50 mA (I forgot).
I tried a lot of drivers: 6SL7 (parallel), 2c51 (parallel), 6n1p, el84 triode. I believe I have a good circuit and combination of tubes.
I will try a different OPT (2K3 primary) and report in the future.
regards,
Jaap
12hg7 (triode mode) with 20 mA is driver, into LL1660/10 mA (1:2) primaries parallel, into KT88 with 400 volt and I suppose about 50 mA (I forgot).
I tried a lot of drivers: 6SL7 (parallel), 2c51 (parallel), 6n1p, el84 triode. I believe I have a good circuit and combination of tubes.
I will try a different OPT (2K3 primary) and report in the future.
regards,
Jaap
speakers are poly natalia
These are outstanding speakers.
see http://www.blackdahlia.com/do_poly.htm
recommended
Jaap
These are outstanding speakers.
see http://www.blackdahlia.com/do_poly.htm
recommended
Jaap
I have no schematic
but I use a tube-rectified 400 volt B+. It is CLCRC, with 47 UF cerafines, an extra oil-cap of 30 UF for the driver.
For the driver I use a 10K/25 watt resistor on top of the LL1660. With a cathode resistor (not bypassed) of 120 Ohm under the 12gn7 it draws about 20 mA. The KT88 has a 500 ohm cathode-resistor, bypassed with a cerafine.
I use gridstoppers: 1K on KT88, 120 Ohm on 12gn7.
That is about all I suppose.
I was inspired bij some designs on www.diyaudio.com.
That's Benny from Antwerp.
doei,
Jaap
but I use a tube-rectified 400 volt B+. It is CLCRC, with 47 UF cerafines, an extra oil-cap of 30 UF for the driver.
For the driver I use a 10K/25 watt resistor on top of the LL1660. With a cathode resistor (not bypassed) of 120 Ohm under the 12gn7 it draws about 20 mA. The KT88 has a 500 ohm cathode-resistor, bypassed with a cerafine.
I use gridstoppers: 1K on KT88, 120 Ohm on 12gn7.
That is about all I suppose.
I was inspired bij some designs on www.diyaudio.com.
That's Benny from Antwerp.
doei,
Jaap
hey,
are you saying you went from a 3K5 toroid to a 2K5 toroid (same brand)on a triode KT88 (Rp 1K) and the sound got much better???
very interesting.... are you at or near clipping (using all the power it has) or is the amp coasting???
you also mentioned weak bass with the 3K5, its interesting to note that going to 2K5 improved this...
dave
are you saying you went from a 3K5 toroid to a 2K5 toroid (same brand)on a triode KT88 (Rp 1K) and the sound got much better???
very interesting.... are you at or near clipping (using all the power it has) or is the amp coasting???
you also mentioned weak bass with the 3K5, its interesting to note that going to 2K5 improved this...
dave
That is correct
The only thing I changed was the OPT, same brand.
I have a lot of reserve power, I use a 100K dact stepper at the front, it only needs 4 to 6 clicks from the startpoint to give sufficient "noise" with mij poly natalia's, which are about 90 dB I believe. I think this amp could be a winner. It sounds better than the different cascaded 6sn7=>cap=> 300b variants I tried. Also the cap coupled C3m/300B was not better.
I use Svetlana KT88's and sylvania 12HG7. Philips pro resistors, silver wire.
I tested some other drivers before with the LL1660 on a testamp with 6B4g. Next drivers to test are 6c45 and 7788 if I can find some.
Jaap
The only thing I changed was the OPT, same brand.
I have a lot of reserve power, I use a 100K dact stepper at the front, it only needs 4 to 6 clicks from the startpoint to give sufficient "noise" with mij poly natalia's, which are about 90 dB I believe. I think this amp could be a winner. It sounds better than the different cascaded 6sn7=>cap=> 300b variants I tried. Also the cap coupled C3m/300B was not better.
I use Svetlana KT88's and sylvania 12HG7. Philips pro resistors, silver wire.
I tested some other drivers before with the LL1660 on a testamp with 6B4g. Next drivers to test are 6c45 and 7788 if I can find some.
Jaap
Re: That is correct
i am suprised there is such a difference between two similar valued OT's from the same company, were they the same physical size???
i would fully expect the 3K5 units to sound better, as long as the power out was sufficient.
it is also important to note that volume setting has no fixed bearing on power output, if your source puts out a high voltage or your amp has a lot of gain, you could be using full power on the amp at the volume settings you mention... just because there is more room to rotate doesn't mean the amp has more power to give.
if indeed you are well away from clipping, this one is a real headscratcher for me.
dave
Jaap said:
i am suprised there is such a difference between two similar valued OT's from the same company, were they the same physical size???
i would fully expect the 3K5 units to sound better, as long as the power out was sufficient.
it is also important to note that volume setting has no fixed bearing on power output, if your source puts out a high voltage or your amp has a lot of gain, you could be using full power on the amp at the volume settings you mention... just because there is more room to rotate doesn't mean the amp has more power to give.
if indeed you are well away from clipping, this one is a real headscratcher for me.
dave
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