Why is the 6DJ8 / 6922 tube a good choice for a tube buffer?
http://en.wikipedia.org/wiki/6922
http://www.pacificvalve.us/YaqinTB.html
http://en.wikipedia.org/wiki/6922
http://www.pacificvalve.us/YaqinTB.html
6DJ8 / 6922 tube?
- Thread starter nordhaven
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Hi
I was going to ask that question.
Well, this is what I have gathered.
Used as a cascode - with bypassed cathode or diode/LED bias - the gain can be quite high. Used as cascode in a differential pair with constant current source in the commoned cathode is quite a good driver for a push-pull amp. A simple simulation with LTSpice gave a gain of 100.
Hope this helps.
Some reckon that this tube has a nice sound.
Serge
I was going to ask that question.
Well, this is what I have gathered.
Used as a cascode - with bypassed cathode or diode/LED bias - the gain can be quite high. Used as cascode in a differential pair with constant current source in the commoned cathode is quite a good driver for a push-pull amp. A simple simulation with LTSpice gave a gain of 100.
Hope this helps.
Some reckon that this tube has a nice sound.
Serge
Serge66 said:Hi
I was going to ask that question.
Well, this is what I have gathered.
Used as a cascode - with bypassed cathode or diode/LED bias - the gain can be quite high. Used as cascode in a differential pair with constant current source in the commoned cathode is quite a good driver for a push-pull amp. A simple simulation with LTSpice gave a gain of 100.
Hope this helps.
Some reckon that this tube has a nice sound.
Serge
Funny!! Your Avatar looks like the one I use on other forums also. I'll put on DIY also.
Yes, the 6DJ8 seems to be the ticket. They can be had for a cheap price as well! I like that there are a lot of tubes in that family to play with.
nordhaven
In my experiance the very common Phillips 6922 has a neutral, precise sound that lends itself to headphone amp drivers, in a long tailed cascode circuit. The 6DJ8 nos tubes I have tried in the headphone amp are all more colored and microphonic than the Phillips 6922. This doesn't mean they sound bad.
AudioPrism produced a very highly thought of tube preamp, using the 6922, called the Mantissa, if that matters to you. Again, a very precise and neutral device.
Bud
In my experiance the very common Phillips 6922 has a neutral, precise sound that lends itself to headphone amp drivers, in a long tailed cascode circuit. The 6DJ8 nos tubes I have tried in the headphone amp are all more colored and microphonic than the Phillips 6922. This doesn't mean they sound bad.
AudioPrism produced a very highly thought of tube preamp, using the 6922, called the Mantissa, if that matters to you. Again, a very precise and neutral device.
Bud
Hi,
Here's a nice line buffer circuit for you:
http://geek.scorpiorising.ca/GeeK_ZonE/index.php?topic=2476.msg30521#msg30521
Only mod I'd suggest is join the power to earth ground through a 100 ohm, 2 watt metal oxide resistor, instead of what's shown.
Cheers!
Here's a nice line buffer circuit for you:
http://geek.scorpiorising.ca/GeeK_ZonE/index.php?topic=2476.msg30521#msg30521
Only mod I'd suggest is join the power to earth ground through a 100 ohm, 2 watt metal oxide resistor, instead of what's shown.
Cheers!
Hi,
Can be, yes. Avoid el cheapo brands and those Amperex dealies that go for a lot of bucks on fleabay - phoolery. Plain old Philips or on the other end, Brimar or Siemens sound great and no pings.
"If you don't feed them RF, they will make their own" - Allen Wright.
Stopper is a must.
They have drive, no doubt about that. But not meant to drive a 300B, 6080 or some other rediculously low-mu tube. That's where a 6922/E88CC comes in handy though
There's some duds for sure, but I've never heard one that fit that. Oscillation was probably the cause.
To take a tangent, 6N1P as *the* most transparent sounding of the family if you can spare the heater current, IMO.
Cheers!
ray_moth said:
Can be, yes. Avoid el cheapo brands and those Amperex dealies that go for a lot of bucks on fleabay - phoolery. Plain old Philips or on the other end, Brimar or Siemens sound great and no pings.
"If you don't feed them RF, they will make their own" - Allen Wright.
Stopper is a must.
They have drive, no doubt about that. But not meant to drive a 300B, 6080 or some other rediculously low-mu tube. That's where a 6922/E88CC comes in handy though
There's some duds for sure, but I've never heard one that fit that. Oscillation was probably the cause.
To take a tangent, 6N1P as *the* most transparent sounding of the family if you can spare the heater current, IMO.
Cheers!
Here is an interesting article on The Suitability of the 6DJ8 for Audio:
http://store.electron-valve.com/suof6dforau.html
http://store.electron-valve.com/suof6dforau.html
oshifis said:
Pretty good article except for this:
Given the distinct lack of any information on audio cascodes -- the only exception being a few articles concerning guitar amps -- I figured t'hellwiddit and simply gave it a try. The cascoded LTP with active tail load worked just great. The AC balance, and sonics, both excellent. Despite losing half the Av, there was still more than enough gain margin for gNFB and a reasonable input sensitivity. The only problem with this topology is the limited output swing, as compared to Vpp. So far as how a single cascode will sound, no tellin', but I'm certainly not going to dismiss it without giving it a try.
I used a 6BQ7 for this. Like the 6DJ8, the 6BQ7 is another one of those VHF cascodes without any pretense that this could be an audio type, and the possibility isn't mentioned at all in the spec sheet. As with all these RF types, you have to watch out for microphonics (why care about ringing at 1500Hz when it's operating at 100+MHz) and parasitic oscillations. So that means use good RF construction practice, and don't forget the grid stoppers. Either shock mount them and/or keep the speeks far enough away so they don't vibrate and you won't have microphonic troubles.
ray_moth said:
I've used the 6N1P in a couple of amps (SE KT88 and PP EL84) and really like it. In my SE KT88 a JAN 6922 doesn't sound nearly as good, the bass is gone. The mids and highs are fine though.
No idea if it is as linear as the 6922 but at least in some cases it sounds as good if not better. (And that Svetlana data sheet is the only one I have for it as well.)
I have used the JAN 6922 as a preamp and also as a phase splitter for my PP amp.
In my experience the JAN 6922 need "LOTS" of current for a good sound - I have experimented with different current values.
I have done serious listening experiments in my acoustically treated room (+-2 dB flat room, with well controlled decay times):
The 6922 will do a very good thing for solo instruments like flute/guitar/voice. The solo instruments will come into front - just to the listener face.
Indeed It might "sound" that the 6922 will deliver less bass.
I have never used the 6DJ8.
trif.
In my experience the JAN 6922 need "LOTS" of current for a good sound - I have experimented with different current values.
I have done serious listening experiments in my acoustically treated room (+-2 dB flat room, with well controlled decay times):
The 6922 will do a very good thing for solo instruments like flute/guitar/voice. The solo instruments will come into front - just to the listener face.
Indeed It might "sound" that the 6922 will deliver less bass.
I have never used the 6DJ8.
trif.
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