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catman

Catman's Analog Musings

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Phono stages of unusual design.

 

G'day all, of the phono stages that I have at least two of them might be considered of 'unusual design', my ANT Kora 3T SE all FET design using FET's made for 'industrial applications' and my Lounge Audio LCR MK III phono stage. 

 

I would venture to guess that many phono stages these days, at least of the less expensive variety anyway, are very likely to be op amp designs based around RIAA feedback eq, and I have a few of those too, and one or two of them sound excellent! 

 

Yet I'll concede that no particular design approach is sonically superior (to my ears), which is actually slightly disappointing to me in all honesty!  I really wish that I could define what makes a really fine sounding phono stage, but so far, I can't!  Regards, Felix.      

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On 17/09/2018 at 8:27 PM, catman said:

Phono stages of unusual design.

 

G'day all, of the phono stages that I have at least two of them might be considered of 'unusual design', my ANT Kora 3T SE all FET design using FET's made for 'industrial applications' and my Lounge Audio LCR MK III phono stage. 

 

I would venture to guess that many phono stages these days, at least of the less expensive variety anyway, are very likely to be op amp designs based around RIAA feedback eq, and I have a few of those too, and one or two of them sound excellent! 

 

Yet I'll concede that no particular design approach is sonically superior (to my ears), which is actually slightly disappointing to me in all honesty!  I really wish that I could define what makes a really fine sounding phono stage, but so far, I can't!  Regards, Felix.      

Excluding cartridge loading, if you EQ'd every phono amp to the same response, they would sound the same, with minor variations in noise levels.

 

On 17/09/2018 at 8:27 PM, catman said:

I really wish that I could define what makes a really fine sounding phono stage

  • good impedance match to the cartridge
  • high SNR and low distortion
  • good compliance to the RIAA gain curve

cheers

Mike

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8 hours ago, almikel said:
  • good impedance match to the cartridge
  • high SNR and low distortion
  • good compliance to the RIAA gain curve

cheers

Mike

 

And good headroom (to minimise the effect of SCPs)!  :)

 

Andy

 

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Is one (dual) op amp stage enough for a typical phono stage? 

 

G'day all, for an hour or so this morning I tried to do a wiring repair on my DIY ESP P06 which has lost a channel and whilst doing it I fired up my DIY Bruce Heran single op amp phono stage and listened to Dave Brubeck's greatest hits.  Whilst I listened I realised (again), what a good sounding and performing that little phono stage is, and how it uses only one OPA2134 dual op amp, where my DIY ESP P06 uses two in separate stages and I wondered if two were really necessary given that the Heran design works so well with only one! :unsure: 

 

I have seen it written that any phono stage using op amps using two op amps in separate stages will always be better than one using only one, and I used to agree with that but now I'm not so sure given the general performance of the Heran design.

 

Yes it is true that high quality phono preamp applications require a high quality op amp, but that isn't an issue things days.  So then why make circuitry more complex than it really needs to be? :unsure:  I do wonder.  Regards, Felix.   

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generally op-amp filters benefit from being driven from a low output impedance source to improve linearity (in this case compliance to the RIAA curve), so you put an op-amp buffer at the input.

 

Mike

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G'day mate, yes you are correct however my system is optimised in terms of buffering etc, so no additional circuitry is needed.  Regards, Felix. 

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