Help with SRPP pre-

[ktigerb]

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]

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]

Please disregard my last question..

I found out that guy was Keith Farr...

Cheers,
Bas

 

[reinhard]

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

 

[fdegrove]

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]

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]

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]

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]

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]

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...

 

[reinhard]

srpp from zur Linde?

hello Frank,

the original amp is from K. Anzai (1969), think you kow his name.
What zur Linde has offered in Elektor is only a simplification of the Anzai. The Anzai is with tone controls.

Reinhard

 

[fdegrove]

Hi,

the original amp is from K. Anzai (1969), think you kow his name.

Sure, I'm well aware of the history of the SRPP.

Thanks to Anzai and Jean Hiraga it got known in Europe many years before it was discussed in U.S. magazines together with its derivatives.

Out it it were born the optimised SRPP circuits, the mu-followers and ultimately the CSS loaded stages.

I had friends building the SRPP preamp by Zur Linde and it was
pretty good at the time.
Much better than the classic circuit of that era anyway. Yet it didn't beat my simpler resistively loaded preamp as I've shown on the forum on dynamic range and imaging.

Since then I experienced several SRPP circuits and still find it a very useful topology but it does need a very stiff PS and often gives best results with high Ri triodes.

Technically that makes a lot of sense as high Ri of the top half isolates the bottom part better hence the transition to the penthode/triode mu-follower making for a good CCS.

Cheers,