• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

going to build a 12au7 pre what do you think?

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J

James D.

Member
Joined 2002
...Sakuma inspires...

Brett,

This is the RIAA - Sakuma of course. And he cheats by using a 5691 first:) 845/845 RIAA


Build one. I'd like to see that. LCR RIAA of course.
Click to expand...

It would be a challenge!

But I am working on the design of an all DHT (& DHP) RIAA preamp with LCR eq. It's a fairly low priority at present so don't expect news soon. I might through in an 845 just for kicks!

ciao

James
 
Circlotron

Circlotron

Member
Joined 2002
A power tube might not have had low microphonics as part of the design criteria.

When I was 14 I made a radio that had a 6M5 power tube as an RF amplifier. It worked but I'm sure a purpose built tube would have been better. But with diy you can do whatever you like, so do it and see how you go! :cool:
 
pedroskova

pedroskova

RIP
Joined 2002
Are certain tubes better than others? Sure... but I do find it a bit ironic that people seriously talk about running massed produced CDP's into their glorious tube monuments to de Forrest without being nailed by the breatheren for listening to digits.:scratch:

I guess as you go into areas of finer and finer interest, the more you lose sight of the bigger picture, and thus, place so much importance on things such as "this tube vs that tube".
 
C

clivetjm

Member
Joined 2003
Rozenblit's GG preamp, which uses 12AU7's, is one of the best, non-exotic preamp's around. It also sounds better than most active preamp's I've heard. Maybe it would sound better with other tubes.

A good way to make a serious improvement is to use a transformer based preamp with no active components so in this respect no tube is the best tube! That's the bigger picture.

I have a problem with so much hatred about this tube. Bruce get's it work well, he's just a good engineer, not a magician.
 
Brett

Brett

Member
Joined 2002
pedroskova said:
Are certain tubes better than others? Sure...
Click to expand...

If you're going to go to all the effort to make something with higher performance or a better cost/benefit than a commercial item, start with something good. A number of much better performing tubes are available for similar money and run about the same circuit parameters (bias, B+ etc), so why cripple yourself. The benefits are not hard to measure or hear.

but I do find it a bit ironic that people seriously talk about running massed produced CDP's into their glorious tube monuments to de Forrest without being nailed by the breatheren for listening to digits.
Click to expand...

Personally, I'd rather listen to vinyl, and I do more than CD. But if CD is the only place I can get a certain peice of music so be it. SACD os OK, but not enough discs I want and too expensive.

I guess as you go into areas of finer and finer interest, the more you lose sight of the bigger picture, and thus, place so much importance on things such as "this tube vs that tube".
Click to expand...

Bollocks. We're not discussing the merits of different laminations in PS chokes, but the fundamental component in the circuit.
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
HERE WE GO ONCE AGAIN...

Hi,

What about a 12AU7 solely used as a cathode follower for a line out? Would that benefit from using a 6SN7?
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No offense, but there at least half dozen different kinds of CFs...

To me the humble 12AU7A isn't even worthy of that kind of service..maybe just about O.K. in a White CF...and I'd still have reservation depending on what exactly it will have to do.

Would that benefit from using a 6SN7?
Click to expand...

I wouldn't sacrifice a perfectly good sounding 6SN7 for that kind of duty...you may be shocked but penthodes do make for better CFs...it looks a bit of a contradiction but it isn't.

Intuition seems to suggest that the type of tube used in a cathode follower won't affect the sound much???
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Fair enough, but you'd still hear every single component surrounding it ...providing the rest of the kit is up to par.

Cheers,;)
 
SHiFTY

SHiFTY

Member
Joined 2002
How about just a very simple one like this?! This is a line output stage from a preamp.

(Borrowed off Patrick Turner's site)

Would this be better off using a 6SN7?

Thanks

:edit: there is a 47uF cap connected from the plate to ground that I inadvertantly edited out! Duh...
 

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Sch3mat1c

Sch3mat1c

Member
Joined 2003
seventransistorlabs.com/
It shows a triode with a 4.7k plate resistor (Shift mentioned he missed the bypass, so the plate is actually effectively solid), a 3.3k and 33k (in series) cathode load, with output coupled via .47uF from the cathode, and a 220k grid leak going from grid to the 3.3k/33k junction. Signal is coupled in via .1uF to grid.

Pat T. knows his shite (as he might spell it), it's bound to be a good circuit.

Tim
 
7N7

7N7

Member
Joined 2003
Re: HERE WE GO ONCE AGAIN...

fdegrove said:


I wouldn't sacrifice a perfectly good sounding 6SN7 for that kind of duty...you may be shocked but penthodes do make for better CFs...it looks a bit of a contradiction but it isn't.

Click to expand...


I agree with this; since a cathode follower operates under 100% feedback, then all the very high gain of the pentode will serve to reduce distortion. And there are plenty of pentodes with high gm to ensure a low output resistance.

I am currently using D3As DC coupled to a 6528; the next amp will be using E810Fs

7N7
 
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