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Old 8th April 2012, 03:10 AM   #1
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Question Re: Tube Line gain stage with pcc88 or ecc82

Hi all!
I need a schematic that I create the preamplifier (gain stage) in the stereo version, with one tube PCC88, or with ECC82 (12UX7). I have a regulated power supplies, which gives B=+240V/60mA.
This preamplifier to the output should have a maximum resistance to 2k7.
thank you
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Old 8th April 2012, 03:51 AM   #2
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Both types mentioned are not especially well suited to the job of a line stage, with gain.

Types with a lower μ rate to be more satisfactory. The B+ rail you have will work with the 12AU7/ECC82. However, that type is not at all linear. Maybe CCS loaded, MOSFET buffered, and step down O/P trafo coupled will work. Trafos in the signal path always mean expense.
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Old 8th April 2012, 01:35 PM   #3
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Quote:
Originally Posted by Eli Duttman View Post
Both types mentioned are not especially well suited to the job of a line stage, with gain.

Types with a lower μ rate to be more satisfactory. The B+ rail you have will work with the 12AU7/ECC82. However, that type is not at all linear. Maybe CCS loaded, MOSFET buffered, and step down O/P trafo coupled will work. Trafos in the signal path always mean expense.
Hi
This a valve premplifier with PCC88 or with 12AU7 (ECC82) means that gain up to 10x and the output resistance to 2.7 kOhm
thank you

Last edited by formula 22; 8th April 2012 at 01:39 PM.
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Old 8th April 2012, 02:08 PM   #4
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The μ (amplification factor) of the 12AU7 is 20. That of the 6DJ8/ECC88 and its relatives is 33. Both types yield excessive gain, for this application. Neither tube, wired common cathode, will have the O/P impedance required.

The stated goals do not mate with the items already on hand.
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Old 8th April 2012, 02:50 PM   #5
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One of the range of advantages of the shunt-cascode stage is that we can decrease the 'gearing' of an amplifier: ie reduce gain AND output impedance, without sacrificing other useful parameters.

This line circuit has a gain of 10 and output impedance of 1K. it will work with any of the 1940s/50s tuner triodes that like 90-100V, including cheap PCC88 and even PCC89, if the input swing is small.

The circuit looks patched together, because I just hacked a phono stage drawing, which works and sounds superb - far better than the usual CCS loaded stages or 6SN7s etc.

Only thing to watch is that the cascode voltage of 90 -95V must be low noise and low impedance. A voltage divider with darlington buffer will suffice, but a shunt regulator is not overdoing things.
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Old 8th April 2012, 03:24 PM   #6
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Quote:
Originally Posted by Rod Coleman View Post
One of the range of advantages of the shunt-cascode stage is that we can decrease the 'gearing' of an amplifier: ie reduce gain AND output impedance, without sacrificing other useful parameters.

This line circuit has a gain of 10 and output impedance of 1K. it will work with any of the 1940s/50s tuner triodes that like 90-100V, including cheap PCC88 and even PCC89, if the input swing is small.


The circuit looks patched together, because I just hacked a phono stage drawing, which works and sounds superb - far better than the usual CCS loaded stages or 6SN7s etc.Only thing to watch is that the cascode voltage of 90 -95V must be low noise and low impedance. A voltage divider with darlington buffer will suffice, but a shunt regulator is not overdoing things.
Hi Rod!
I just want to I create the pre-amp with valve / tube or PCC88 or with12UX7 (ECC82), which delivers the pleasant valve/tube sound.! Where anode voltage preamplifier range from + B=150...250V.
With the gain up to <10x and output to <2,7 kOhm!
thank you and cheers!

Last edited by formula 22; 8th April 2012 at 03:28 PM.
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Old 8th April 2012, 10:33 PM   #7
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Quote:
the pleasant valve/tube sound
An FX box?

You have been given good advice. You need to realise that you are, in effect, asking people to tell you how to make 3=4. The tiny snag is that 3 does not equal 4, so no amount of wishing on your part can make it so.
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Old 8th April 2012, 11:17 PM   #8
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The PCC88 will get you close on output impedance if you run it hot(high current) but you'll have 20+ gain.
If you can accept one tube per channel you could have a common cathode stage dirct coupled to a CF. Then you could tailor it to "any" gain and output impedance with some feedback.

/Olof
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Old 8th April 2012, 11:24 PM   #9
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Quote:
Originally Posted by formula 22 View Post
With the gain up to <10x and output to <2,7 kOhm!
thank you and cheers!
When you say 'output <2.7K ohm' do you mean the load it is driving is 2.7K ohm or you want the output impedance to be < 2.7K ohms?

Cheers

Ian
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Old 8th April 2012, 11:47 PM   #10
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Have a google for a jadis DPL schematic (or maybe the dpl2). It uses 12au7 and is simple enough. I know the 12au7 is frowned upon here, but I have heard one of these preamps and it sounded very good indeed. Its on my list to build one someday.

There were no special parts inside, using a 7812 for heaters.

Fran
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