Chipomatic balanced input RIAA

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By the way, 1VRMS FFT at 62dB gain when fed from a Jensen step up transformer, input config is BAL.
 

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diyAudio Chief Moderator
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Here's 1/F from post 21's config. 12 averages to see deeper. Nice 1/F result no uphill. The mild subsonic curve designed in the DC servo should have helped in this too. Hey, where is my raw input 0.00067% THD at same output level from post 9? Why the SUT interfacing changes that down to 0.00032%? The balanced impedance divider has 43 Ohm Zo. The SUT 4kiloOhm Zo. Scott, can this be cancellation between the SUT THD and the AD8429 or internal better result to it or a better result between the INA and the OPA now that the INA works at 100x source impedance level?
 

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diyAudio Chief Moderator
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The EMU TRACKER is my audio interface box that I run ARTA measurement screens with. 1/F is the noise region below a frequency that noise starts picking up from a pass band average level. All things in nature do that, not only electronics, they go noisier the lower the frequency after a corner point. Other earlier and faster, other later and milder. If you listen to the waves breaking at a seashore although you can hear various pitch swirls the bass noises tend to bunch up and dominate.
 
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1/F noise can end up too much in a phono given the internal gain goes way up in LF & VLF due to the RIAA curve. So we ought to keep it in check. Else we will hear a boiling rumble especially on big sensitive loudspeakers and closed back headphones.
 
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Test with SMPS (a Philips hair trimmer's switching wall adapter, a CM choke from a broken satellite receiver's PSU for bit of EMI anti-pollution, a CUI DC/DC dual output converter of 80mVpp ripple spec to turn the adapter's 15V loaded output to 24V symmetric, basic RC filter and a resistor divider to +/-14V for 20mVpp 235kHz switching ripple on each rail and as much a dirty return point, no linear post regs, 1VRMS signal output, 62dB total gain with a Jensen 10X step up transformer)
 

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Hi Salas,

I followed with interest your builds.

They are all interesting if admitely somewhat complex for me who doesn't need really anything right now, but very nice to follow and very nice of you to share all this.

Having said that, just to warm up the soldring iron after 15y of incativity, I was considering a very high quality passive RIAA with op amps, just to see how far one could go nowadays with these. Something SE (for a Goldring 1042 MM) similar to CNC or Muffsy or what can be found on some datasheet with some revisions, hadn't made my mind yet...

Is my understanding correct that you are likely to end up with a nice solution that could match my quest?

Tanks again for all this

Claude
 
NEW 'Chipomatic' rejects swirling MiniMoog(TM) like noise spectrum !

" If you listen to the waves breaking at a seashore although you can hear various pitch swirls the bass noises tend to bunch up and dominate "

" Else we will hear a boiling rumble especially on big sensitive loudspeakers and closed back headphones "



Hi Salas. :D



I almost would have thought you were describing ^^ working on my old MiniMoog(TM). :eek:

Built WAY before they had any decent chips like Scotts ones for the Naval Research Labs !



I guess the Navys 'chipped' forest of sub sniffing :blackcat: sonar arrays was somehow ...

...able to overcome the waves breaking at the seashore, pitch swirls, bass noises & boiling rumble !

Damn lucky for The Free World too ! :cool:


:wiz:


" Hey, where is my raw input 0.00067% THD at same output level ... "

" ... broken satellite receiver's PSU for bit of EMI anti-pollution "



Anyway, looks like an impressive ^^ noise performance. :)

Fortunately I don't live that close to any nuclear sub bases ! ;)

But I am surrounded by switch-mode noise, cellphone interference ...

... the neighbours noisy arcing power-tools & my '67 LEC refridgerator full of cold beer !

( really do need to make an EMI anti-pollution device for THAT muther ) :rolleyes:



Keep up your great work on the 'Chipomatic' ... THE RUSSIANS ARE COMING ! :eek:



Si. :)

t.S.E.c

.
 
diyAudio Chief Moderator
Joined 2002
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Hi Salas,

I followed with interest your builds.

They are all interesting if admitely somewhat complex for me who doesn't need really anything right now, but very nice to follow and very nice of you to share all this.

Having said that, just to warm up the soldring iron after 15y of incativity, I was considering a very high quality passive RIAA with op amps, just to see how far one could go nowadays with these. Something SE (for a Goldring 1042 MM) similar to CNC or Muffsy or what can be found on some datasheet with some revisions, hadn't made my mind yet...

Is my understanding correct that you are likely to end up with a nice solution that could match my quest?

Tanks again for all this

Claude

I am doing those experiments out of the same curiosity as yours. Right now I am giving input for a dual mono layout to be finished by local friend Dimdim (DACs & firmware aficionado) on easy to handle 1206 sized passives SMD board so to can evaluate it with no doubt. The RIAA capacitors value combination will remain through hole to be MKP. Can also accept MELF resistors. Will have SE/BAL input switch and onboard LT3045/3094 regulators to be small sized, tightly looped, and self contained. Will let you guys know.
 
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The part is the THAT 1583, I did a similar application with FET's for the Naval Research Labs using the AD625 (in-amp breakout) designed for PGA's. The navy was building a forest of sub sniffing sonar arrays.


You did say you were doing to redraw the scribble for that a while back...


I'm still en route for maximum heresy in a phono front end :)
 
You did say you were doing to redraw the scribble for that a while back...

At your service. This is a sketch all caveats apply. The basic idea is to replace the input devices with ultra-low noise ones and use the existing ones as cascodes. I'm not sure how far down you can push the noise with this but 0.5nV should be within reach without extreme values.

The 5V below V+ cascode voltage sets the collector/drain current of the input devices, the loop forces the outputs to a negative common mode voltage like in the original Demrow version of this circuit. Typically one would use something like a simple 4 resistor/op-amp differential to single ended converter for the eventual output. The gain equation is the standard one.

An extreme case might be running the input devices at 5mA (R = 1k), and Rf = 250 Ohms, and Rg = 5 Ohms for G = 100. I have no idea if this is stable or has other misbehaviors.
 

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