Help with SRPP pre-

ktigerb · 9th October 2003, 09:31 AM

Hi Guys
Attached is a circuit published some 20 yrs ago which I built and had TX made but stalled the finish as the valves were too expensive at that time (for me any how).

I need to know what component values are necessary to change if I substitute V2 and V3 with 12AX7's as in V1 since I have just received a batch of NOS Ediswan 12AX7's.
Thanks
keith birss

Bas Horneman · 9th October 2003, 09:53 AM

You'll end up with a very different baby if you substitute those tubes all with 12ax7....

first 2 tubes are ofcourse the phono amp the last one the "normal" preamp.

Since it is a phono amp..I would look for a phono amp design that uses all 12ax7 AND THEN build a different preamp...using whatever you fancy or can afford.

Cheers,
Bas

PS..are you the Keith that did dj'ing and rented out sound equipment?

Bas Horneman · 9th October 2003, 10:42 AM

Please disregard my last question..

I found out that guy was Keith Farr...

Cheers,
Bas

reinhard · 9th October 2003, 02:56 PM

Hello,

you can use the amp with 12AX7 in all positions. Make all cathode resistors 1K. The gain will be to high with bypassed cathodes,
35 dB each stage.
Omit the cathode bypass caps, then each stage has a gain of 30dB, good for phono.
The line amp will be a little loud.

Reinhard

fdegrove · 9th October 2003, 06:31 PM

Hi,

That SRPP is a preamp designed by Rainer Zur Linde.

The ECC83 1 2 should be used here for correct gainscaling.
Mu of 100, 60 and 17 respectively.

If not a very noisy pre will result and if only ECC83/12AX7As are used to output impedance will be too high as well.
Not to mention the fact that you'd need to redesign half of the preamp as well.

Surely it must be possible to buy a pair of ECC81s/12AT7As and ECC82s/12AU7As in SA?

Cheers,

DrG · 9th October 2003, 08:55 PM

Do you require a phono stage? If not then I would buy 2 ECC82's (not too expensive from Mr Valve...) and build the line stage as designed. I did years ago and it sounded pretty damn good!

fdegrove · 10th October 2003, 01:31 AM

Hi,

In case only the line stage is considered an SRPP stage using a 12BH7A would be better still...

Actual results would depend on PS reguation which is tantamount to the SRPP topology.

There's a myriad of other choices for this service one can come up with with too.

Cheers,l

ktigerb · 10th October 2003, 08:10 AM

Thanks Frank Reinhard Dr G and Bass
you can stop twisting my arm now (there were no emoticons for tongue in cheek available).
I'll buy the damn things and wait some more for them to arrive ,like I said in an earlier thread with 4 professional students living at home my budget is thinner than the proverbial "....hair"

regards
keith

analog_sa · 10th October 2003, 08:22 AM

I also built this circuit (sometime in my youth) and it is largely responsible for my intense dislike of SRPP. Of course it might have been the tubes used

DrG · 10th October 2003, 04:10 PM

Quote:

I also built this circuit (sometime in my youth) and it is largely responsible for my intense dislike of SRPP.

Luckily such trauma doesn't seem to have created a permanent aversion to tubes...

9th October 2003, 09:53 AM	#2
Bas Horneman diyAudio Moderator Emeritus Join Date: Apr 2002 Location: The Netherlands Blog Entries: 18	You'll end up with a very different baby if you substitute those tubes all with 12ax7.... first 2 tubes are ofcourse the phono amp the last one the "normal" preamp. Since it is a phono amp..I would look for a phono amp design that uses all 12ax7 AND THEN build a different preamp...using whatever you fancy or can afford. Cheers, Bas PS..are you the Keith that did dj'ing and rented out sound equipment? __________________ Boatanchor amps forum My "adventures" in audio

9th October 2003, 10:42 AM	#3
Bas Horneman diyAudio Moderator Emeritus Join Date: Apr 2002 Location: The Netherlands Blog Entries: 18	Please disregard my last question.. I found out that guy was Keith Farr... Cheers, Bas __________________ Boatanchor amps forum My "adventures" in audio

9th October 2003, 02:56 PM	#4
reinhard diyAudio Member Join Date: Dec 2000 Location: Germany	srpp Hello, you can use the amp with 12AX7 in all positions. Make all cathode resistors 1K. The gain will be to high with bypassed cathodes, 35 dB each stage. Omit the cathode bypass caps, then each stage has a gain of 30dB, good for phono. The line amp will be a little loud. Reinhard

9th October 2003, 06:31 PM	#5
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	Hi, That SRPP is a preamp designed by Rainer Zur Linde. The ECC83 1 2 should be used here for correct gainscaling. Mu of 100, 60 and 17 respectively. If not a very noisy pre will result and if only ECC83/12AX7As are used to output impedance will be too high as well. Not to mention the fact that you'd need to redesign half of the preamp as well. Surely it must be possible to buy a pair of ECC81s/12AT7As and ECC82s/12AU7As in SA? Cheers, __________________ Frank

10th October 2003, 01:31 AM	#7
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	Hi, In case only the line stage is considered an SRPP stage using a 12BH7A would be better still... Actual results would depend on PS reguation which is tantamount to the SRPP topology. There's a myriad of other choices for this service one can come up with with too. Cheers,l __________________ Frank


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9th October 2003, 08:55 PM	#6
DrG diyAudio Member Join Date: Aug 2003 Location: South Africa	Do you require a phono stage? If not then I would buy 2 ECC82's (not too expensive from Mr Valve...) and build the line stage as designed. I did years ago and it sounded pretty damn good!

10th October 2003, 08:10 AM	#8
ktigerb diyAudio Member Join Date: May 2003 Location: Durban	Thanks Frank Reinhard Dr G and Bass you can stop twisting my arm now (there were no emoticons for tongue in cheek available). I'll buy the damn things and wait some more for them to arrive ,like I said in an earlier thread with 4 professional students living at home my budget is thinner than the proverbial "....hair" regards keith __________________ Keith Birss

10th October 2003, 08:22 AM	#9
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	I also built this circuit (sometime in my youth) and it is largely responsible for my intense dislike of SRPP. Of course it might have been the tubes used

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