Problem fixed. I changed the original EL34B with a couple of JJ EL34. The original biasing was at 520mV, now I setted the JJ at 550mV. I am listening my Sweet Peach EL34 with a couple of PROSON EVENT 6 speakers and I have to say that the music is very good. Can anyone tell me which tubes are compatible with EL34? I would like to make some tries with other valves. Thanks a lot!
Was there any improvement with the JJs? You need to let the Chinese EL34B settle in - please give them a chance!
I note your bias measurement so you are running at 55mA which is fine. I make that about 5W maximum theoretical output in triode mode. I just can't believe how dynamic and loud this amp sounds for this kind of power level.
Regarding other valves, you could try KT88 or 6550 with bias re-adjustment of course.
Re the question from Dave about bypassing electrolytic caps with smaller non-elec ones this tends to help with the limitations of the electrolytic's non-ideal performance at higher frequencies. They compliment each other.
Paul.
I note your bias measurement so you are running at 55mA which is fine. I make that about 5W maximum theoretical output in triode mode. I just can't believe how dynamic and loud this amp sounds for this kind of power level.
Regarding other valves, you could try KT88 or 6550 with bias re-adjustment of course.
Re the question from Dave about bypassing electrolytic caps with smaller non-elec ones this tends to help with the limitations of the electrolytic's non-ideal performance at higher frequencies. They compliment each other.
Paul.
For the KT88 or 6550 these are rated for higher power so the bias should be set to what you are using for the EL34. These valves will take more but the amplifier may not. However, I assume that the Peach can handle the heater currents as it is available fitted with these valves.
In theory running larger valves with a relatively cool bias may reduce distortion. The KT88 could be the best valve to use here with the best being GEC but a reasonable financial approach means they are not practical any more! Having said that, the Chinese EL34B never fails to impress me in triode mode.
Before changing valves, it is more important to upgrade the coupling capacitors, remove the input ones and definitely extract the unwanted series and parallel resistors around the inputs.
Paul.
In theory running larger valves with a relatively cool bias may reduce distortion. The KT88 could be the best valve to use here with the best being GEC but a reasonable financial approach means they are not practical any more! Having said that, the Chinese EL34B never fails to impress me in triode mode.
Before changing valves, it is more important to upgrade the coupling capacitors, remove the input ones and definitely extract the unwanted series and parallel resistors around the inputs.
Paul.
The KT66 should be OK and just re-set the bias to the same as you have for the EL34B. Note that a KT66 may be closer to its power limit than the EL34B, which is a higher rated valve when compared to the standard EL34 which is more like the rating of the KT66. However, the datasheets show an example of biasing similar to how the Peach will have it set. Avoid using the GEC KT66 as they are way too valuable.
If you want to determine the bias voltage, just check the datasheet via google for single tube class A triode mode.
Cheers, Paul.
If you want to determine the bias voltage, just check the datasheet via google for single tube class A triode mode.
Cheers, Paul.
I really just meant to answer your question about bias voltage which is shown under Vg or Vg1 for typical single ended configuration. You don't need to worry about this bias voltage, just check the bias current - or did you mean the voltage across the cathode resistor? This should be maintained so that the maximum ratings for the valve are not exceeded. So for a KT88 for example, in theory you could increase the current but I do not know the maximum safe limit for the Peach I'm afraid. I will ask the manufacturer about this. Mine is set to around 50mA and the mains transformer runs only slightly warm.
Paul.
Paul.
Actually the EL34B as fitted at the factory as supposed to be higher rated at 30W. The manufacturer just came back to me and confirmed that the bias should be 50 to 60mA.
I would be careful about using a standard EL34 for this reason, the supplied EL34Bs actually sound very good and they are cheap. The sound in triode mode is very detailed and dynamic.
Also, although the power input is a bit high, the valve is getting an easy life in the Peach compared to guitar amp use for example.
Paul.
I would be careful about using a standard EL34 for this reason, the supplied EL34Bs actually sound very good and they are cheap. The sound in triode mode is very detailed and dynamic.
Also, although the power input is a bit high, the valve is getting an easy life in the Peach compared to guitar amp use for example.
Paul.
My fault. I should have specified my comment was directed at running the JJ EL34 at 55mA.
My own EL34 Sweet Peach is running at 42mA (plate voltage raised to 395V after stabilizing) with Tesla EL34L, russian 6N3P-EV and russian 6N1P-EV. Until now, the only modification so far, is to wire the MM input as an AUX input instead.
My own EL34 Sweet Peach is running at 42mA (plate voltage raised to 395V after stabilizing) with Tesla EL34L, russian 6N3P-EV and russian 6N1P-EV. Until now, the only modification so far, is to wire the MM input as an AUX input instead.
I wonder if the idle current relates to max theoretical power?
I.e. the HT is about 430V, so with a 50mA idle the max non-clipped power is at cutoff - giving 430 x 0.05 = 21.5W, so a sine wave would be half that at 10.75W, minus transformer losses and load impedance mismatch.
I usually run my GU50s at 50mA BTW.
I.e. the HT is about 430V, so with a 50mA idle the max non-clipped power is at cutoff - giving 430 x 0.05 = 21.5W, so a sine wave would be half that at 10.75W, minus transformer losses and load impedance mismatch.
I usually run my GU50s at 50mA BTW.
Exactly - the bias affects the maximum power as it's class A but we do need to place it on the correct part of the load line for best efficiency and performance. Also, you mentioned impedances and the losses there will be caused by the internal anode resistance in relation to the load impedance. So, we probably end up with 6 or 7 watts RMS by the time it goes through the output transformer.
I must bench test it one of these days to check the freq response and max power I actually get but I keep wanting to listen to it.
Something else we should look at is removing stuff from the speaker circuit. We have the headphone socket switch and impedance selector switch which are not easy to replace. We could replace the headphone switch with a good quality toggle on the back panel and the impedance selector with some sort of terminal block and jumper. I see the pro model has extra 4mm sockets as per most Chinese amplifiers but doing this would look wrong unless you have the screen print to match. These switches are not good enough to be kept in the path. Any ideas?
Paul.
I must bench test it one of these days to check the freq response and max power I actually get but I keep wanting to listen to it.
Something else we should look at is removing stuff from the speaker circuit. We have the headphone socket switch and impedance selector switch which are not easy to replace. We could replace the headphone switch with a good quality toggle on the back panel and the impedance selector with some sort of terminal block and jumper. I see the pro model has extra 4mm sockets as per most Chinese amplifiers but doing this would look wrong unless you have the screen print to match. These switches are not good enough to be kept in the path. Any ideas?
Paul.
Enjoying this thread. Now I want to buy a Sweet Peach FU50. I can do soldering pretty well. Would a KISS mod be: 6n6p for 6n1, replace the 2 .01 mike caps?
I plan on driving the Peach with an LOD cable from my pmp into the "mp3" input. My budget needs this to work. Opinions?
BTW output to a pair of modded Altec 808's with Altec 12" in DIY ported boxes tuned around 40hz.
I plan on driving the Peach with an LOD cable from my pmp into the "mp3" input. My budget needs this to work. Opinions?
BTW output to a pair of modded Altec 808's with Altec 12" in DIY ported boxes tuned around 40hz.
My sweet peach has just arrived also intact to regional Australia. Ha i bet i'm the only dude in Armidale NSW to have a sweet peach. Some things of note are.
1. Man it is freaking heavy !
2. Build quality is much better than anticipated
3. Sound is very clear and smooth
Being a total noob and without any idea about valve amps as this is my first.... i wish it had an subwoofer input as this would fit more easily into my current audio set up. but you can't have everything.
I love this amp though !
1. Man it is freaking heavy !
2. Build quality is much better than anticipated
3. Sound is very clear and smooth
Being a total noob and without any idea about valve amps as this is my first.... i wish it had an subwoofer input as this would fit more easily into my current audio set up. but you can't have everything.
I love this amp though !
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