6B4G and ECC83

[klauss00]

hello everyone!
I am wondering if I can substitute one ECC83 with two 75 tube in the next schema
kind regards!
claudiu

 

[DF96]

Probably, yes. But why?

 

[316a]

I don't understand people using ECC83 with directly heated triodes . I have built a few such as the Shishido 2A3 and was never happy with the sound . Better off with an ECC81 , ECC85 or 5965 for high mu drivers . These have much lower Ra and should be able to drive the 6B4G grid nearer to 0V so more output power available . Expect around 2 watts with an ECC83 and 6B4G and nearly double that with a <10k Ra driver . Then there is also the ECC83's ability to drive the miller capacitance , which will limit the HF and may lose a few dB at 20kHz (which is audiable) , hence the reason why SRPP has been chosen in the design

316a

 

[famousmockingbird]

Yes I agree, the ECC83 can provide the voltage swing but the current isn't there. The more current the better the slew rate.

 

[klauss00]

I want to build a amplifier with 6s4s and 75, a friend told me that 75 it is equivalent with ecc83. Can anyone recommend me a schema? Thank you!

 

[azazello]

ECC83 is, IMO, not good choice for driver for 6S4S for good sounding. Better use E180F, 6J9P /6Ж9П/, 6J11P /6Ж11П/ Russia.

 

[Parafeed813]

To me it looks like a schematic for an EL34 amp that (for commercial reasons) accepts an octal base DHT as well.
You can try this design and if the driver isn't powerful enough change to a stronger valve (likely less gain) or insert a mosfet source follower.

 

[klauss00]

Probably, yes. But why?

I want to be a retro style amplifier, I like how it look 75. Other variant it is with 76 ant 6SN7 driver. Any comment?

 

[hooman]

JAN-PHILIPS 6AW8 CAN DRIVE 2A3 BETTER THAN EXPENSIVE ECC83. 6AW8 IS TRIODE AND PENTODE IN ON GLASS .SO TRIODE CAN MAKE CIRCUIT FOR VOLTAGE AMP AND PENTODE CAN DRIVE 2A3 BY CATHODE FOLLOWER .

 

[klauss00]

Nobody can say anything to me about this schema?

 

[soulmerchant]

I don't understand people using ECC83 with directly heated triodes . I have built a few such as the Shishido 2A3 and was never happy with the sound . Better off with an ECC81 , ECC85 or 5965 for high mu drivers . These have much lower Ra and should be able to drive the 6B4G grid nearer to 0V so more output power available . Expect around 2 watts with an ECC83 and 6B4G and nearly double that with a <10k Ra driver . Then there is also the ECC83's ability to drive the miller capacitance , which will limit the HF and may lose a few dB at 20kHz (which is audiable) , hence the reason why SRPP has been chosen in the design

316a

Fully agree. Most "loftin-white" amplifiers are actually not "loftin-white". But there are ways to make ECC83 work FAR better. I am getting well over 2 watts and am using 6SL7 - Directly coupled with no coupling capacitor or cathode bypass. I will post my schematic in the next post...

 

[soulmerchant]

Nobody can say anything to me about this schema?

It never sounded that special to me when I tried it.... and I tried many kinds of designs like it. If you take a look at the plate curves and do some maths then you will probably figure out why.

I directly coupled 6SL7 to 2a3 and it sounds truly superb. No cathode bypass either!

But I did it in a special way. see below and google Darius Loftin-White to learn more on how it can be done. Even ecc83 can drive 300b if you do it like Darius did. It won't have that old radio tube glow though...

 

[soulmerchant]

BTW if you want to use 6B4G for single ended, you will need to use DC on the heater. AC will hum

I much prefer to do that using filament chokes. Lundahl makes some nice ones for this. Or just use chinese 2a3's instead.

 

[soulmerchant]

btw - you could also use AC on the 6B4G and use a heater hum cancelling circuit like Darius did:

http://rl12t15.blogspot.fr/2008/03/ecc83-300b-darius-loftin-white.html

I haven't tried it yet, but will if I have some time. I have some 6B4's here and a hum cancellation circuit is cheaper than a good AC circuit.