What about the 4P1L driver, any schematic suggestion?
I own a 26 preamp but I don't know if will be enough?
I own a 26 preamp but I don't know if will be enough?
If you can provide 12Vpp (4.24V RMS) on 4P1L power tube grid (Ug), the 100mW output achievable.
See second stage.
p.s.
Small output transformers (Edcor especially) not primary induction champions, so lower -3dB point will be not so low.
See second stage.
p.s.
Small output transformers (Edcor especially) not primary induction champions, so lower -3dB point will be not so low.
@euro21, my little PCL86 triode amp does better than that LOL. It's hitting 1% THD at just over 0.8W output. Max Pout at 5% THD is 2.2W. The triode-wired output tube works at 340V/22-24mA into 7K with fixed bias. The fixed bias is derived from the 14V supply for the heater.....
For me, this is one of the few applications where OTL can be a better choice in any regard. But hype will always prevail, that I know already.
For me, this is one of the few applications where OTL can be a better choice in any regard. But hype will always prevail, that I know already.
@45
In general OTL is better choice ... but I'm not sure that has enough low output impedance for 18R headphone.
6N6P output stage has about 60R, even -big beast- 6AS7/6080 (cascode) output has about 8R (without output capacitor), .... with 12-15W power dissipation per channel.
Is worth it?
p.s. russian medium power tubes are not famous for low distortion at larg/er/ tress .... but they can withstand nuclear flash. 🙂
In general OTL is better choice ... but I'm not sure that has enough low output impedance for 18R headphone.
6N6P output stage has about 60R, even -big beast- 6AS7/6080 (cascode) output has about 8R (without output capacitor), .... with 12-15W power dissipation per channel.
Is worth it?
p.s. russian medium power tubes are not famous for low distortion at larg/er/ tress .... but they can withstand nuclear flash. 🙂
"DHT OTL?"
You are very funny today. 🙂
Although, come to think of it, it's possible to design something layout. 😛
Output four 211, 1600V B+/70mA for each tube (224VA+65VA for filament/each pair tube), 1200V 30-100uF/1200V coupling capacitors, beefy driver, 30-40kg weight ... all this for 100mW output. 🙂
You are very funny today. 🙂
Although, come to think of it, it's possible to design something layout. 😛
Output four 211, 1600V B+/70mA for each tube (224VA+65VA for filament/each pair tube), 1200V 30-100uF/1200V coupling capacitors, beefy driver, 30-40kg weight ... all this for 100mW output. 🙂
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It's just for you Felipe! 😈
CAVEAT!
It's a joke! No one should build it!
CAVEAT!
It's a joke! No one should build it!
Bela could I am expected better specs using Ale's hybrid mu-follower as anode load for 26 & 16 ohm output transformer loading 4P1L?
I've built a 4P1S single stage amplifier earlier, with a 5K OPT.
4P1S with a 5K:18Ω OPT will have an overall gain of about 0.42
To get 1W@18Ω, we need 4.2Vrms output voltage. That means about 10Vrms single ended input. An input step up transformer is needed.
Regardless of high gain driver DHTs like EML 20/30 series, two stage seems to be necessary for your design.
4P1S with a 5K:18Ω OPT will have an overall gain of about 0.42
To get 1W@18Ω, we need 4.2Vrms output voltage. That means about 10Vrms single ended input. An input step up transformer is needed.
Regardless of high gain driver DHTs like EML 20/30 series, two stage seems to be necessary for your design.
I havn't drawn the full schematic.
Generally speaking.
4P1S(Chinese version of 4P1L) triode at about 225V 30mA, with 5K OPT.
Self bias with LM317 constant current sink.
Cathode capacitors from cathode to GND and B+ tap of the OPT at the same time.
Two stage MOSFET capacitor multipliers for ripple filter.
The OPTs are custom made from a Chinese craftsman. I chose this to reduce cost. It's performance is not so good.
Generally speaking.
4P1S(Chinese version of 4P1L) triode at about 225V 30mA, with 5K OPT.
Self bias with LM317 constant current sink.
Cathode capacitors from cathode to GND and B+ tap of the OPT at the same time.
Two stage MOSFET capacitor multipliers for ripple filter.
The OPTs are custom made from a Chinese craftsman. I chose this to reduce cost. It's performance is not so good.
Hey guys, very bad news: Edcor don't sell nothing to Europe without a VAT number so here in Spain only have VAT number entreprises not for personal use....
What specs needs to be a custom OPT:
-5K primary
-18R secundary
-Maximum current?
-Wattage?
-Primary inductance?
-Frequeny response?
-Insertion Loss?
-THD+Noise?
-Etc?
TIA
-5K primary
-18R secundary
-Maximum current?
-Wattage?
-Primary inductance?
-Frequeny response?
-Insertion Loss?
-THD+Noise?
-Etc?
TIA
5k trafo is suggested for attaching your 18 load to 8 Ohm tap secondary. (Tube see a 10k load)
After search I found Mr. Moglia has done extensive testing to 4P1L and end up with 3k2 for a Parallel SE, doing math for Single Ended, it doubles to almost 7k.
Going to custom, it would lead to.. around 7k-10k/ 18R. And I bet 7k5 could be a compromise in between. Just my 5 cents
After search I found Mr. Moglia has done extensive testing to 4P1L and end up with 3k2 for a Parallel SE, doing math for Single Ended, it doubles to almost 7k.
Going to custom, it would lead to.. around 7k-10k/ 18R. And I bet 7k5 could be a compromise in between. Just my 5 cents
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I think the LL2766 gapped for 30mA could be a good start. Secondary is quite flexible, so you could run other impedance headphones as well.