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Old 17th April 2003, 03:12 PM   #1
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Default 37 / 6080 pre-amp

I want to build a pre which is a 37 connected to a 6080 CF.

No holds barred pre. Cost not really an object.

Should I DC couple them, cap couple them? Seperate or same PS?

Run the 37 at 135v, 4ma, 9v bias (battery).
Run the 6080 at 140v, 40mA, unsure on bias (recommendations?).

Probably MV rectifiers (which ones?) and regulator tubes (?).

Power Supply ideas?

Thanks!!!!
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Old 17th April 2003, 03:21 PM   #2
Joel is offline Joel  United States
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Hi Richard,

What happened to the 71A p-p preamp??
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Old 17th April 2003, 03:24 PM   #3
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Default NOTHING...

Actually.... this idea has been floating in my head for like a year now... so maybe I should build this first as I have the 37's and 6080's.

Don't need any iron.... just build a PS.

Seems a little easier anyhow...

the 71a is on hold.
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Old 17th April 2003, 03:39 PM   #4
Joel is offline Joel  United States
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Ok.

Well, unless you need to drive a mile of cable, I think a lower current CF tube would be easier to implement - considering the current draw of the 6080.
Now, I myself am building a 6080 SE amp currently, and I have them biased down to 50mA, which is reasonable - but in order to do that, they need the grids at -125V! So, that's a monstrous amount of signal voltage needed.

These are the issues when using the regulator tubes.

Anyway, I would think for any normal preamp operation and cable length that you could use something a lot easier to work with - like a 12BH7, etc. This will still give you a good 10-15mA of current, and a reasonably low Zo.

Joel
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Old 17th April 2003, 03:44 PM   #5
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Default low vp?

unless I run them at 50v, 50mA, 20v bias.......

I'd like at least 30mA in the output stage. Hey maybe a 71a CF

hmmm... can DHT's be cathode followers???? how do you wire that together?

TXS!!!
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Old 17th April 2003, 04:01 PM   #6
Joel is offline Joel  United States
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Default Re: low vp?

Quote:
Originally posted by RichardJones
I'd like at least 30mA in the output stage.
Ok, well, how about a 6V6 triode-strapped? It actually makes a nice triode, and it has a transconductance of 5,000. Rp of 1900 ohms. 49.5mA current.

Just a thought.
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Old 17th April 2003, 04:12 PM   #7
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Just curious, why do you need a CF? They have a controversial reputation soundwise to say the least. With a single 6080 in common cathode you'll get plenty of drive and low output resistance. Do you really need two stages?
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Old 17th April 2003, 04:15 PM   #8
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Default gain

I need 2 stages for voltage gain. I want around 5-10 for voltage gain, but have a nice meaty output stage... specifically to potentially drive some nasty input capacitance on my MOSFET amp.

Thats why I was thinking of a 2 stage amp.

Unless I use a high mu tube WOT..... hmmm....

I always liked the sound of the 37 though.
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Old 17th April 2003, 05:28 PM   #9
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Quote:
Originally posted by analog_sa
Just curious, why do you need a CF? They have a controversial reputation soundwise to say the least. With a single 6080 in common cathode you'll get plenty of drive and low output resistance. Do you really need two stages?
I agree. Nothing wrong with CFs , but IMHO
it's easier to get good sound without them.

I you need a lot of gain,
an alternative would be 37- 6080 in cascade.
Separate power supply for the 37 and the 6080.

cheers
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Old 17th April 2003, 05:31 PM   #10
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Default cascade?

Cap couple them?

Say a 25K load on the 37 and a 800ohm load on the 6AS7.

Should give me the gain I want.

What voltage should I run the 6080 at?

Thanks!!!
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