here you can find a phono stage made with the 6DJ8-ECC88, the 6922 have some better performance but is the same tube
http://web.tiscali.it/audiofanatic3/Schemi/Tipo/Valvole/Tipo_Valvolari.html
ciao
Filippo
www.audiofanatic.it
http://web.tiscali.it/audiofanatic3/Schemi/Tipo/Valvole/Tipo_Valvolari.html
ciao
Filippo
www.audiofanatic.it
fdegrove said:
Bollocks. It's a brilliant design that uses the best of both to get lots of gain, low distortion and low noise in one stage. Still haven't ever seen a tube design with noise anywhere near the cascode's or a transformer with it's resolution. It's cheap (the FET) too.
Don't tell Allen, but subbing in an ECC99 for the second tube makes it even better.
O Frank,
You are otherwise such a tolerant, friendly and clever beast, and here you go saying Alan has failed because he used a FET!!
I've been there....... with Mick Maloney's Supratek design (I had input on the power supply). I can tell you the FET pulls back noise by a huge margin - quite audible - even with selected tubes (Mick used 417A) the addition of the FET reduced noise by around 10dB. This is no small thing, particularly on a MC phono, and it was achieved with SS, one thing it's good at. And the tubes still add that indefinable something which makes the design instantly recognisable to the tubophile, I promise you.
My own GK-150 design is also a hybrid; SS front end, tube output stage. I even go so far as to use a quality IC for the phono stage. You won't believe how quiet and powerful sounding it is. There are a few things tubes can't do, at least not without huge complexity, completely overshadowing the object of the exercise!
Cheers,
Hugh
You are otherwise such a tolerant, friendly and clever beast, and here you go saying Alan has failed because he used a FET!!
I've been there....... with Mick Maloney's Supratek design (I had input on the power supply). I can tell you the FET pulls back noise by a huge margin - quite audible - even with selected tubes (Mick used 417A) the addition of the FET reduced noise by around 10dB. This is no small thing, particularly on a MC phono, and it was achieved with SS, one thing it's good at. And the tubes still add that indefinable something which makes the design instantly recognisable to the tubophile, I promise you.
My own GK-150 design is also a hybrid; SS front end, tube output stage. I even go so far as to use a quality IC for the phono stage. You won't believe how quiet and powerful sounding it is. There are a few things tubes can't do, at least not without huge complexity, completely overshadowing the object of the exercise!
Cheers,
Hugh
Allen's design is very nice, but if you want to try something different that has some good noise cancellation features, try this (schematic at bottom of page):
TubeCad Journal
I recommend that you read the entire article and also Part 1 (the previous month).
To get good PS noise cancellation C1=22n and C2=1u. If you change anything, these values will have to change. But, with these values you can get close to 60db noise reduction below the noise floor coming from the circuit and PS. If you build a good PS the total noise should be very much below the signal level.
TubeCad Journal
I recommend that you read the entire article and also Part 1 (the previous month).
To get good PS noise cancellation C1=22n and C2=1u. If you change anything, these values will have to change. But, with these values you can get close to 60db noise reduction below the noise floor coming from the circuit and PS. If you build a good PS the total noise should be very much below the signal level.
Yes, -90db is almost required. I did not say what I meant to say correctly.
Without the noise concellation circuit, the PS noise may already be considerably below the signal level, depending on the nature of the PS. Let's say it's 60db below for example.
The noise cancellation circuit in this design allows you to drop the noise floor more than 60db below that. So, hypothetically you'd get -120db. In practice this is hard to do, but the noise cancellation circuit will make whatever the raw design does a whole lot better.
Without the noise concellation circuit, the PS noise may already be considerably below the signal level, depending on the nature of the PS. Let's say it's 60db below for example.
The noise cancellation circuit in this design allows you to drop the noise floor more than 60db below that. So, hypothetically you'd get -120db. In practice this is hard to do, but the noise cancellation circuit will make whatever the raw design does a whole lot better.
Hi,
Wouldn't you say this is fascinating enough to merit a thread of its'own?
Mind you, I do have great interest in this, anything low signal level is a bit like RF, it does have a story to tell...and the smallest of small signals matters.
It also shows you what could go on at higher signal levels...totally capturing if you'd ask me...
Like mainframes in computors, there's a lot of info and tips to be found in the pro world.
Cheers,
Wouldn't you say this is fascinating enough to merit a thread of its'own?
Mind you, I do have great interest in this, anything low signal level is a bit like RF, it does have a story to tell...and the smallest of small signals matters.
It also shows you what could go on at higher signal levels...totally capturing if you'd ask me...
Like mainframes in computors, there's a lot of info and tips to be found in the pro world.
Cheers,
Would make a very interesting thread! If we could get Mr. Broskie to join the forum, he could run that thread with one hand tied behind his back.
As a poor to average tube circuit designer, unfortunately, the best I can do is to refer everyone to TCJ where John gives many examples of noise cancellation tricks.
In this particular phono preamp, the output stage is a common cathode diff amp. The second grid is normally grounded, but in this case Broskie feeds the PS noise into the second grid and this noise, in phase with the PS noise introduced normally into the rest of the circuit, cancels the normal PS noise (similar to the way NFB would be employed in this topology). This design is very clever (at least to me) and with the right values of capacitors should have an extremely low noise floor.
Or did you have something else in mind Frank?
As a poor to average tube circuit designer, unfortunately, the best I can do is to refer everyone to TCJ where John gives many examples of noise cancellation tricks.
In this particular phono preamp, the output stage is a common cathode diff amp. The second grid is normally grounded, but in this case Broskie feeds the PS noise into the second grid and this noise, in phase with the PS noise introduced normally into the rest of the circuit, cancels the normal PS noise (similar to the way NFB would be employed in this topology). This design is very clever (at least to me) and with the right values of capacitors should have an extremely low noise floor.
Or did you have something else in mind Frank?
Hi,
It would indeed.
Better still would be to apply the same technique of noise cancellation in the PS in the first place.
Which is excactly what you do by using series regs.
That, in a nutshell, is my major quibble with TCJ; if your not savvy or an engineer you're just left second guessing.
Now, combining both appropriately could yield very high noise reduction indeed and hopefully a very good sounding phono preamp.
BTW, it's worthwhile to go through the pages following the original article.
FWIW, noise cancellation techniques are not new at all and can be found in Pro equipment from the Fifties or maybe even prior to that period.
Thanks to J.B. we now have most of it in one convenient place on the web.
No, not really...I had my 2 cents added. TA.
Cheers,
P.S. You're much better than you give yourself credit for IMO.
It would indeed.
Better still would be to apply the same technique of noise cancellation in the PS in the first place.
Which is excactly what you do by using series regs.
That, in a nutshell, is my major quibble with TCJ; if your not savvy or an engineer you're just left second guessing.
Now, combining both appropriately could yield very high noise reduction indeed and hopefully a very good sounding phono preamp.
BTW, it's worthwhile to go through the pages following the original article.
FWIW, noise cancellation techniques are not new at all and can be found in Pro equipment from the Fifties or maybe even prior to that period.
Thanks to J.B. we now have most of it in one convenient place on the web.
No, not really...I had my 2 cents added. TA.
Cheers,
P.S. You're much better than you give yourself credit for IMO.
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