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Old 16th April 2004, 02:14 AM   #1
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Location: Minnesota
Default mu / srpp / or CF?

I have been reading a lot lately and just wondering the best way sonically for a line amp?

A) mu stage
B) SRPP stage
C) CF

either of these can use a tube or SS. For the voltage gain of the circuit probably 6SN7, 6BX7, 6BL7 or similar.

Thanks!
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Old 20th April 2004, 03:09 PM   #2
Mike C is offline Mike C  United Kingdom
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Location: South east Essex, UK
Default Mu Stage

My previous preamp was:
First stage triode/triode mu follower
Second stage cathode follower.
Though designed for 12AU7's, it could run E80CCs instead and that made
it sound pretty good, with tweaks such as stepped attenuators and
PSU cap upgrades.

However, I then made a simple single mu stage preamp using the E80CC
again, loaded with E83F triodes. This was a very significant upgrade!
I built it with standard components, and didn't even use a stepped
attenuator, and it still beat the previous one in every way.
Far better dynamics, great tonality, better detail and resolution,
tighter better bass etc etc. And more 'persuasive' and real.

For me, no contest; triode/pentode mu stage.
Search for 'mu stage philosophy' in Yahoo to learn about mu stages.

Pentodes to consider are E180F, D3A and E83F among others.
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Old 20th April 2004, 08:19 PM   #3
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Default how about....

how about an EL84 in triode mode loaded with a EL84 pentode mode??

of course in a mu-follower setup.

I want to use current production tubes...
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Old 20th April 2004, 09:00 PM   #4
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Default Re: Mu Stage

Quote:
Originally posted by Mike C
However, I then made a simple single mu stage preamp using the E80CC
again, loaded with E83F triodes. This was a very significant upgrade!
Hey Mike,

Thanks for sharing your knowledge. Simple as it may be, could you post a schematic?

I looked up "mu stage philosophy", and found Alan Kimmel's
article:

http://home.zonnet.nl/horneman/ml/akimmel.htm

It is interesting and well written. Do folks agree
with what he says? Comments?

Mike, is your mu stage similar to any of the schematics
in Alan's article?

Thanks again!

Best,

George Ferguson
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Old 21st April 2004, 08:39 AM   #5
Mike C is offline Mike C  United Kingdom
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Location: South east Essex, UK
Default My preamp details

As you asked ...

Details of my E80CC/E83F mu stage preamp are already on this board.
To find it, search for Nina in this section to find the thread
with circuit details.

There is also a picture in the Photo thread, on page 6.

I think most things are well covered in the thread, but if you have
any questions please ask.
I can provide a chassis layout if anyone is interested ....
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Old 21st April 2004, 01:16 PM   #6
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: mu / srpp / or CF?

Konnichiwa,

Quote:
Originally posted by AudioGeek
I have been reading a lot lately and just wondering the best way sonically for a line amp?

A) mu stage
B) SRPP stage
C) CF
Non of the above. Use a simple common cathode stage with a valve having a suitable Gain and low anode impedance.

Sayonara
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Old 21st April 2004, 09:05 PM   #7
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KYW / T :

what do you have against Mu stages? too complex? too hard to get right?

would you consider a 56 or a 76 to be a suitable tube for a basic pre of the type you suggest (i'd like to use the 56 cause i have globe ones and i am fixated on using globe tubes)?

fwiw, I have a mapletree octal 6 pre that i built from a kit and i much prefer the srpp circuit to the cf circuit in my system, which consists of a music hall mmf-5 tt/denon-dl103/lehmann black cube or a tjoeb 4000 tubed cdp into the mapletree into a pair of bottlehead paramours into my diy single driver speaks (with bybee purifiers on the + speaker terminals).

kevin / ez_angus
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Old 22nd April 2004, 06:39 AM   #8
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Default Re: My preamp details

Quote:
Originally posted by Mike C
Details of my E80CC/E83F mu stage preamp are already on this board. To find it, search for Nina in this section to find the thread with circuit details.
Hey Mike,

Thanks--I found both your description and your photo, and enjoyed both. Very nice build.

I hope folks will continue to share their experiences with Mu Stage/CCS/etc. I am pondering tweaking a power amp with some sort of active loading (once I get the amp built, that is ), sort of a la Gary Pimm.

Gary (and Mike) certainly liked the results. Has anyone else tried such tweaks?

Thanks again, Mike.

Best,

George Ferguson

(In Tucson, where the honeysuckle is blooming outside my window, and smells wonderful.)
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Old 22nd April 2004, 10:33 AM   #9
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by EZ_Angus
what do you have against Mu stages?
Nothing.

Quote:
Originally posted by EZ_Angus
too complex? too hard to get right?
Neither. They just don't sound as good as plain CC stages.

The question asked was:

"(What is) the best way sonically for a line amp? A) mu stage B) SRPP stage C) CF"

The answer is what I gave, based on an extensive "all else being equal" comparison. Mu follower is second, tied with Allan Wrights SLFC, SRPP is third and Gainstage/CF is a distant fourth.

Quote:
Originally posted by EZ_Angus
would you consider a 56 or a 76 to be a suitable tube for a basic pre of the type you suggest
Depends, the anode impedance is a little on the high side.

You can use a (parallel feed) stepdown output transformer, maybe something like 40K:2k5 (4:1), which will cut gain by a factor 4 and reduce the output impedance by a factor 16, so the "bogey" 56 at RCA Databook Spec operating point would give a little over 10db gain with an output impedance of around 600 Ohm, just right for a linestage IMHO.

Sayonara
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Old 24th April 2004, 06:48 PM   #10
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Hi KWY / T

wow, cool idea. the closest stock tranny i've found looking on the web is by magnaquest:

Parallel Feed Linestage Transformers

B7 15K:500 ohms CT, parallel feed line stage transformer, permalloy core, brass channel frame, 5:1 step down ratio, 17VACrms maximum signal input. 56,76,6J5, 6SN7,5965,5670,12AV7, 6N1P - $198 pr.

which is 5:1 stepdown from a lower base.

in any event, do you think a transformer coupled pre like this based on the 56 would work well with the 80-124-245 loftin-white amp you so kindly laid out in an earlier thread?

thanks again for sharing your knowledge. IMHO, economics is a piece of cake compared to electronics.

Kevin
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