Differential amplifier for LR-RIAA

the road not taken.
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docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Differential amplifier for LR-RIAA

Post by docali »

Hi all,

the next step to my prefrerenced LR-phono amplifier would be to use an differential stage for the RIAA equalization. The design looks promising in the simulation as it deals better with heavy loads compared to the CCA. Here the 4th time constant is not added but would be easy around the 750mH choke. Not to mention we are still in the NoC area :D

Any comments are welcome! I am not sure if the values for the inductance of the PP-transformer are relaistic for 1.75+1.75:1. Primary inductance is 210H following the data sheet of LL1692a

Best regards,
docali
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docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Post by docali »

Hi,

sadly this implementation of the LR-RIAA cannot be used as output of the amplifier as it is highly dependent of the input impedance of the next stage. So, it must be used between two amplification stages with fixed impedances.
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maymymay
Posts: 6
Joined: Mon Sep 08, 2008 2:07 pm

Post by maymymay »

Hello docali,

I like the "no c" in phono circuit design, sound the most "direct" and any news on this balanced phono? And how many current pass through the 10H choke in D3a common cathode? Can you post the complete circuit?

Thanks

Ngan
docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Post by docali »

Hi Ngan,

the current through L4 is about 42 mA with 36 Ohm resistance. What do you miss in the schematics - the power supply unit?

Best regards,
Bernd
maymymay
Posts: 6
Joined: Mon Sep 08, 2008 2:07 pm

Post by maymymay »

Hi Bernd,

Thanks for your reply and is it still need extra gain stage in the riaa out between the line stage? i was build the steve bench already and sound very good, i hope to builx a balanced lr phono and fojnd your circuit is good for, can you post the complete circuit with power supply in gif file in the forum? thank you in advanced.

Kind regards

Ngan
docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Post by docali »

Hi Ngan,

I am still in the theoretical phase of planning. The differential is one possibility but it needs further investigation for me especially with respect to distortion spactra (even and off harmonics).

The power supply can be taken from Stephies LR or others. I would prefer tube rectification and choke input.

Have you recognized my other thread with the cathod coupled amplifier (CCA)?

Best regards,
Bernd
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