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Old 3rd April 2010, 10:38 PM   #31
SY is offline SY  United States
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Quote:
Originally Posted by ray bronk View Post
Why do you think it is a misprint?

Ray
Because the source impedance of a cathode follower is roughly 1/gm. What's the gm of the 6SN7 at that current?
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Old 3rd April 2010, 10:45 PM   #32
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Listening with headphones is currently awesome. But I've been working on improving my speaker setup. My current project is a high end version of the Tubelab SE using 300B's and all film caps. Followed by a mod to my JBL L150A's.
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Old 3rd April 2010, 11:55 PM   #33
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Hi,

Well, at this point, I am just looking for a good preamp to either buy or build. Frank's preamp is ok, certainly, but I don't need the phono part of things. So just the linestage will do nicely. I wonder if I could just use a single supply, or just one transformer. anyway, thanks for the info.

Ray Bronk
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Old 4th April 2010, 12:43 AM   #34
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I really don't know how much benefit there is from the dual xfmrs...but I think you would probably be fine with one. I swapped to the 6N1P's in my Bijou...it's been a while and I'm kind of curious as to the difference. I don't think it's fair to rate it until it breaks in for a while... but it was initially a noticable step down in quality. I kind of look at it as the "WOW" factor. Right now it's not quite there. I'll break it in with a little Rush...and see how it does...

I think if you stick with the linestage version (no phono) and go with the one transformer...you would be pleased. It appears to me that 12AU7 and 12BH7A are interchangable directly...but possibly could be tweeked by a resistor change?

Last edited by huskydawg9; 4th April 2010 at 12:49 AM.
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Old 4th April 2010, 01:02 AM   #35
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Hi, Well, I'll probably look in to building that line stage. The 12BH7 uses more current than the 12AU7 for the heater. Did you look at the other schematic by Carlos?

Ray
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Old 4th April 2010, 01:04 AM   #36
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I'm not sure which one you speak of...post a copy of the schematic.

I just switched back to the 6H30's (maybe a bit prematurely). I love these tubes. Geddy Lee is sounding pretty awesome right now...(the "WOW" is definitely there...)

Last edited by huskydawg9; 4th April 2010 at 01:11 AM.
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Old 4th April 2010, 07:29 AM   #37
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Hi, if you read the whole thread, Carlos has this favorite schematic that uses a 12AU7 that he likes versus the 6SN7 or the 6CG7 tube.

Now, gotta ask you because I can't see your pics because I am blind. So in some respects building this preamp won't be as hard to do as it would if it were a PCB. Anyhow, what did you end up doing as far as the supply and transformer. There's just the 12BH7/12AU7 tube and that's it. I saw the parts list, and some of it didn't understand what the stuff was. I'll go back and look at the parts list again. What did you do concerning the volume control? If memmory serves me right, he is using an Attenuator of 1 Meg. Don't think I can get a volume pot that big.

So if I don't hear from you tomorrow, I hope your Easter day is a nice one.

Ray Bronk
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Old 4th April 2010, 07:53 PM   #38
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I used left over 3/4 inch cherry hardwood flooring for the case. The top is two pieces of aluminum separated by a piece of cherry wood. I used several pieces of terminal strips with posts to do the p2p wiring. Transformers and big caps are mounted on top, except for the 14v filament transformers are mounted underneath. I tried to place the components such that the other parts would reach. The star ground is a sheet of copper that I mounted to a board located under the transformers. The pictures in the thread show the guts well. Maybe you could get someone to describe them to you. I am using a Goldpoint 500k attenuator. I thought it was a "make before break" type...but it must not be, because I have to mute the circuit to avoid the annoying pops when adjusting it.

Last edited by huskydawg9; 4th April 2010 at 07:56 PM.
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Old 5th April 2010, 10:10 PM   #39
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Hi Carlos,

Ok, reading your info you gave me, I am real new at this stuff, so bear with me. Your description of the power supply, that first cap 150 Uf probably at 400V? now are this configuration is that all in series off one leg of the diode bridge, having trouble visualizing the circuit.

We can take this offline and email me directly:

raybronk@gmail.com

Then you can give me more details about the circuit. Don't wish to hijax this thread. Thanks.

Ray Bronk
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Old 17th July 2010, 07:34 PM   #40
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hi guys,
I want to try this preamp (6sn7 version).
Can anyone suggest a schem for the PSU section?
I would go with a SS rectifier

V.
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