SRPP ANZAÏ tube preamplifier...
Bought for cheap, in working condition but in need of TLC and "crude-awkward Idiophile improvements" removals, it's a restoration / modification job coming :
Schematic :
The SRPP ANZAÏ preamplifier was highly regarded in the 80s-90s - at least here in France.
Designed in Japan by Mr. Katsutaro Anzaï and popularized by Mr. Jean Hiraga, our well-known Audio Expert, the circuit uses a passive RIAA corrector, without FB, offering reputedly a wide dynamic range and a high output / input level capacities, a performance barely found on more classic Phono preamp circuits...
Work is on progress : cleaning, dismantling, complete rewiring, power transformer replacement, shielding, new face plates...
Wait and See...
T
Bought for cheap, in working condition but in need of TLC and "crude-awkward Idiophile improvements" removals, it's a restoration / modification job coming :
Schematic :
The SRPP ANZAÏ preamplifier was highly regarded in the 80s-90s - at least here in France.
Designed in Japan by Mr. Katsutaro Anzaï and popularized by Mr. Jean Hiraga, our well-known Audio Expert, the circuit uses a passive RIAA corrector, without FB, offering reputedly a wide dynamic range and a high output / input level capacities, a performance barely found on more classic Phono preamp circuits...
Work is on progress : cleaning, dismantling, complete rewiring, power transformer replacement, shielding, new face plates...
Wait and See...
T
Nice work, but the two separate volume controls are no longer reasonable,
if you use it a lot.
if you use it a lot.
Except that with two separate volume controls, you don’t need a balance control.
Yes, I could change for a Volume and a Balance pots, but the unit was originally designed with two independent volumes, so I stayed with that solution.
The end of the work approaches :
Before :
After :
The back faceplate is missing - it will wait for September the reopening of my engraving workshop supplier :
T
The end of the work approaches :
Before :
After :
The back faceplate is missing - it will wait for September the reopening of my engraving workshop supplier :
T
Output should be at a low impedance, not at a high impedance.
Such a high impedance must be buffered.
Such a high impedance must be buffered.
The McIntosh MX110 uses an unusual 40K pot at the output. Yes, nuts. But it did sound good to the ear in euphonic way. Matches very well with their more neutral power amps.
The SRPP ANZAÏ circuit is a low impedance output, hence the A50K output volume pot.
This is the value that was used by the original designer - and I don't think that nor Mr Anzaï, nor Mr Hiraga are nuts.
T
This is the value that was used by the original designer - and I don't think that nor Mr Anzaï, nor Mr Hiraga are nuts.
T
Low impedance output is only when the pot is at maximum so there is no series resistance with the output
Anyway normaly the power amplifier has volume pot so those can stay always at maximum
Anyway normaly the power amplifier has volume pot so those can stay always at maximum
End of the story : the preamp is installed... Sorry, but none of my power amps have a volume control : it is the role of the preamp here.
T
T
End of the End : last modifications today...
1 - Correction of the output level in TONE OFF mode :
There was a significant drop in output level between TONE ON and OFF. By only switching the tone corrector RLC circuit vs. a fixed/compensated attenuator, while leaving the 12AU7 output stage always engaged as a permanent output buffer, I could increase the level output of the TONE OFF setting to match exactly the TONE ON level with controls set at noon. Sorry, my notes are in French here...
No more volume drop, and correct 20kHz square waves.
2 - increase of the coupling capacitors :
Interstage caps : 0.22µF ---> 2.2µF
Output caps : 0.22µF ---> 4.7µF
The bass square waves immediately went from steep to flat top.
Now that modified SRPP ANZAÏ has reach a step ahead, and is ready to play in the High Court - or rather in the Big Leagues :
Last step : engraving back faceplate - on September.
T
1 - Correction of the output level in TONE OFF mode :
There was a significant drop in output level between TONE ON and OFF. By only switching the tone corrector RLC circuit vs. a fixed/compensated attenuator, while leaving the 12AU7 output stage always engaged as a permanent output buffer, I could increase the level output of the TONE OFF setting to match exactly the TONE ON level with controls set at noon. Sorry, my notes are in French here...
No more volume drop, and correct 20kHz square waves.
2 - increase of the coupling capacitors :
Interstage caps : 0.22µF ---> 2.2µF
Output caps : 0.22µF ---> 4.7µF
The bass square waves immediately went from steep to flat top.
Now that modified SRPP ANZAÏ has reach a step ahead, and is ready to play in the High Court - or rather in the Big Leagues :
Last step : engraving back faceplate - on September.
T
To end the End of the End : some quick measurements checks made today...
PHONO performances :
CD/AUX performances :
Balance between Tone ON and Tone OFF - all tone controls set at noon (neutral) ;
Final schematic :
T
PHONO performances :
CD/AUX performances :
Balance between Tone ON and Tone OFF - all tone controls set at noon (neutral) ;
Final schematic :
T
Hello T.,
nice report with valuable information/documentation and all these pictures of this unit 👍 - Thank you!
It was known to me by it´s designation only - never seen one in real life.
What i would like to ask: did you measure the amplification factor resp. Gain [dB] of the line stage as well?
Regards Eberhard
nice report with valuable information/documentation and all these pictures of this unit 👍 - Thank you!
It was known to me by it´s designation only - never seen one in real life.
What i would like to ask: did you measure the amplification factor resp. Gain [dB] of the line stage as well?
Regards Eberhard
Thanks @Zitronenfalter ! 🙂
Aw no ! I forgot to do it separately... My bad ! No worry : let me return to my bench and I'll tell you all that ASAP... 😉
T
OK, I got it... 🙂
The gain of the whole 12AU7 line stage - tone-corrector or attenuator included - is :
The measurement is taken with a 1VRMS signal applied to the CD input, and measured to the OUTPUT output.
T
The gain of the whole 12AU7 line stage - tone-corrector or attenuator included - is :
- Tone OFF mode : G=1.912, or +5.62dB
- Tone ON mode : G=1.984, or +5.54dB, with tone controls set in neutral position.
The measurement is taken with a 1VRMS signal applied to the CD input, and measured to the OUTPUT output.
T
Please what is the value of the first series resistor in RIAA network ( after coupling capacitor ) ?
82K - sorry for the omission. This is the original ANZAÏ circuit value, by the way.
If you intend to test that circuit, I'd suggest first to stay with the roiginal value 0.22µ instead of 2µ2 that I installed for the 1st coupling capacitor - this to check if the RIAA is followed more closely at low frequencies.
I suspect the 2µ2 value to give an enhancement of the RIAA curve below 100Hz, reaching +2.45dB at 20Hz.
Incidentally not bad for deep bass, indeed 😎, but this may be an issue with warped records ? 🤔
T
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Thanks !
Never had an issue with warped records, even with heavy warped ones.
Never had an issue with warped records, even with heavy warped ones.