Hi I'm looking at buying this kit from eBay (Douk Audio HiFi 6P3P kit) but would like to see the circuit diagram before I buy just wondered if anyone on the forum may have one and could email to me?
Also if anyone has built the kit and how it performs?
Many thanks
Richard
Also if anyone has built the kit and how it performs?
Many thanks
Richard
Many thanks for the link, good to see it also can use EL34's. Shame I threw my box of old valves away 20 years ish back never thought I'd be building using valves again.
Cheers
Richard
Cheers
Richard
Bias question
I'm considering purchasing an EL34 version already built, here is the link:
Douk Audio EL34 Vacuum Tube Amplifier HiFi Stereo Single-ended Power Amp Black | eBay
Thing is, I'd like to use my own valves and bugs me that these amps seldom have reliable instructions for setting the bias... any thoughts on that?
I'm considering purchasing an EL34 version already built, here is the link:
Douk Audio EL34 Vacuum Tube Amplifier HiFi Stereo Single-ended Power Amp Black | eBay
Thing is, I'd like to use my own valves and bugs me that these amps seldom have reliable instructions for setting the bias... any thoughts on that?
I'm considering purchasing an EL34 version already built, here is the link:
Douk Audio EL34 Vacuum Tube Amplifier HiFi Stereo Single-ended Power Amp Black | eBay
Thing is, I'd like to use my own valves and bugs me that these amps seldom have reliable instructions for setting the bias... any thoughts on that?
It's not the bias you need to worry about , it's the under sized mains transformer . A 160VA transformer on a stereo SE EL34 amp is asking for trouble
316a
I have bought the exact same amplifier (Oldchen BL-02): the "deluxe" version, with stainless steel chassis, better caps and PSvane tubes. The warning about the transformer is spot on. I've replaced the EL34 with two NOS metal 6F6 tubes (1613, actually) because the power transformer was overheating. Real undistorted output power was less than advertised anyway; more like 6V6 than EL34: B+ at 300V only and output transformers about the same size as my (expensive) SE EL84 amp. On the plus side it looks nice and it sounds great (for the price) at moderate listening levels, I'm using it right now connected to a iPhone. I've also replaced the output tubes cathode resistors to accomodate the 6f6, and most of the internal wiring. The original assembly was poor, with untwisted and misplaced heater wires tucked under the turret board and red/black speaker wire to the mains switch. With proper wiring the hum disappeared and the electrical safety improved hugely. The worst manufacturer mistake was a too big first filter capacitor. This was a rectifier tube killer; I've decreased it to 33uF.
The issue I'm facing now, after the output tube replacement, is the insufficient gain because 6f6 have less gain than EL34-B, and it was not enough for a phone jack input already. On my amplifier, the two 6N9P sections of each channel are connected in parallel and they feed directly the output tube. I've increased the gain of the preamp stage at maximum by increasing the 6N9P anode and cathode resistors and the output tube grid resistor (I followed the RCA specs for 6sl7); and I decreased a little the global feedback, but the gain it is still not enough, I need to turn the volume knob near or at the max. On a similar amplifier I've got good results by using two stages of 6sn7, but I don't have good vintage 6sn7's anymore. I have a few NOS RCA metal 6SH7 instead, and maybe a pentode stage will have a higher gain while sounding as good as the Shuguang 6N9P / 6SL7. Does anyone tried this tube connected as pentode? Any further suggestion to fix this issue? I tried to disconnect the global feedback alltogheter, but this amp NEEDS a bit of feedback to sound good (well, maybe the output transformers aren't the best on the market...).
The issue I'm facing now, after the output tube replacement, is the insufficient gain because 6f6 have less gain than EL34-B, and it was not enough for a phone jack input already. On my amplifier, the two 6N9P sections of each channel are connected in parallel and they feed directly the output tube. I've increased the gain of the preamp stage at maximum by increasing the 6N9P anode and cathode resistors and the output tube grid resistor (I followed the RCA specs for 6sl7); and I decreased a little the global feedback, but the gain it is still not enough, I need to turn the volume knob near or at the max. On a similar amplifier I've got good results by using two stages of 6sn7, but I don't have good vintage 6sn7's anymore. I have a few NOS RCA metal 6SH7 instead, and maybe a pentode stage will have a higher gain while sounding as good as the Shuguang 6N9P / 6SL7. Does anyone tried this tube connected as pentode? Any further suggestion to fix this issue? I tried to disconnect the global feedback alltogheter, but this amp NEEDS a bit of feedback to sound good (well, maybe the output transformers aren't the best on the market...).
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