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In Reply to: RE: In the right circuit I have used the . . posted by John PA on June 11, 2012 at 09:45:46
Swap a few wires. Unless, of course, the filament transformer hasn't the reserve to cope.
Rolling 12AU7s is a waste of money and time.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Follow Ups:
Timbo,
Are you saying the tube can not impact on the sonics due to its archetecture, or that they all sound bad, so what's the point?? I have seen many amps that employ them, why are they used so often?
I have rolled many 12AU7s and found definite changes in the sound of my amp. I ended up using 7136s in place of the 12AU7s in my Jadis DA-60 integrated. I am no EE and not tech savvy, so I don't know what they do in the circuit. The DA-60 requires 3 X 12AU7 and 2 X 12AX7 in the "preamp" section.
Steve
12AU7s - good ones - make great zero-gain buffers, e.g. cathode-follower with maximum NFB and a gain of .95. That is what I use mine for. I would never use any of the 12AU7 varieties in a critical role like splitter/driver.You'll also notice that I'm not alone in my considered view of the 12AU7.
I'm into good sounding audio to listen to simply recorded acoustic music, IE mostly classical, and choral music. I'm an ex cathedral chorister, and still sing in my current parish.
I listen to such music at least once a week, live. And once I had a system that did a very good job at that, and letting me hear how different each recording is. Well, my need to worry fell. Issues like the room, better amplifiers, wider FR range took primacy. Playing around with small tonal changes strikes me as a waste of time, and money.
The rebuilt classic valve PP NFB power amps I've used since the mid 1990s contain role-appropriate valves. They have very large storage in their PSUs and have very good bass, they are quiet, sweet, and crisp, valvey, yet neutral.
For me audio is about knowing where I am going, learning, and sticking to it. Likely return on investment in improving believability and involvement is my main criterion.
I would never use a multi-miked, phased Eq'd, Aphexed, mix-down pop recording as a guide.
While simpler recordings have a good deal of variation* in the sound-field they create, I am reasonably across that and can understand what I hear. EG ORTF, 2 spaced omnis, or 3!, Decca's mix. Crossed pairs, sound-field mikes, Kimber Iso-Mike. etc.
In the late 1970s I was lucky to find a speaker design that beat the QUAD 57s, almost new black mesh ones that I nearly bought, and did a bettr job on the inevitable baby boomer pop/rock collection as well. They are 2-way 8 inch spheres and since the 90s bi-amped: actively in the bass since there IS no low-pass, and passively in the treble.
The side of the audio hobby with changing cables, valves, or regular changes in equipment seems a pretty pointless tail chase to me. I feel it is driven by trying to get a hi-fi system to sound good on recordings for which the term high-fidelity to an ensemble in a space in real time just does not apply.
E.g. One visitor (who because he has a dipl.eng in EE thinks he's 'a scientist') turned up with a carry bag of nothing but pop CDs and put on a Linda Ronstadt album - famously discussed in Rolling Stone for its use of the Aphex Aural Exciter, and which I have on LP and still enjoy.
He proceeded to tell me that there was a lot of MR distortion. Well, hell yes!
Dig it.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Edits: 06/15/12 06/15/12
Tim, I know what you are saying!
But the supply of 12FQ7 is very limited and will be gone in the not too distant future. I recommend that the tubes be set up to use the 6CG7 since the EH is available and a nice sounding tube. Or the 12BH7 EH.
I don't remember 12fq7s being available in big numbers even in peak tube years.Do they really sound that much better with a 12v filament?
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Mike, I think Jim is saying that the 12FQ7 sounds better than the 12AU7 and can be used without mods where the 12AU7 is being heated with 12.6V, of course assuming the filament supply can provide the extra current the FQ draws. There should be little sonic difference between the 12FQ7 and 6CG7/6FQ7. True, Jim?
True - but a BIG difference in availability. That was my point. 12FQ7s are old stock only, and that supply never was all that large.
I didn't think the supply was all that large.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Has been my experience that lower voltage on filament translates to lower potential for hum.
All things considered.
The Mind has No Firewall~ U.S. Army War College.
Thats been my experience also.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
a quieter tube.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
John
Do you mean with an above ground DC source tied to the filaments? That is the best way I have seen to reduce troublesome hum.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
you are good to go.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
On some phono stages I have gone up to 90vdc tied thru a pair of 100k resistors.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
the problem. On my dac I built, I set the tubes to around 60 volts above ground. Worked very well and the analog stage is very quiet. You gotta love tubes.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
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