https://www.diyaudio.com/community/threads/chipomatic-balanced-input-riaa.331009/ Salas noticed that too).
Hi, yes he spotted the device, I went through his thread (I have great respect for Salas).
Nevertheless I did not see he connected it with Robert Demrow design from 60's and later actualized-upgraded by Wayne Kirkwood with help of Hans Polak......
After looking at many 1nV/sqrHz mic preamp data sheets, I will try THAT1580 as soon as time allows, difference from all others is that it allows gain adjustment even in trans-impedance mode (which is noise wise game changer) and very conveniently provides balanced output.
Small take on filter capacitors, particularly film and foil, and particularly on polystyrene, tab terminated vs extended foil and ESL
This is about film capacitors for filters,, like RIAA filter in this thread. As I'm finishing TT and coming back to preamp, choosing caps is back as an question.
First , couple of statements about my experience and learning:
- Filter caps are different story than coupling and decoupling caps, so only about filters.
- I have great preference for PS capacitors as it has been proven many times that they are closest to ideal. I disregard all snake oil audiophile capacitors.
In recent looking about others implementation of RIAA filters, I have seen many classic PS "cylinder bugs" installed, so I wonder how they perform comparing to my preferred RIFA PFE extended foil 1% caps...
Here is short take:
About measurements:
My input card ADC is 192/24 capable, which is still limiting frequency at 96 something kHz , I have no means to measure above so I can just catch corner of capacitor knee.
Simple 1st order filter is created, Input signal of 970 mV feed through 9k6 resistor in series with DUT capacitor. Scope input is across capacitor.
I run 20kHz to 100kHz sweep and recorded trace, 1/24 smoothed to remove digital artifacts...
DUT's are, in close but not exact nF values:
top : preffered RIFA extended foil PFE, 4n57 1% , green trace
next: classic "bug" tab terminated 5n6 10% yellow trace
next: PP ERO 33n +-5%, MKP 1845 , red trace
Bottom: PP ERO 3n3 MKP1846, orange trace
Now order of above picture is mixed up due capacitors values:
What I read is, polystyrene capacitors show perfect linear behavior ( green and yellow).
I cannot say that deviation of the curve close to 96kHz is because of impedance or my ADC limitations, anyway it is far above audio frequency.
In any case , both PS types seems to be perfect for filter.
On the other hand, by many tests next to perfect polypropilene , MKP (red and orange trace) , shows quite bit of deviant characteristic vs PS
This is about film capacitors for filters,, like RIAA filter in this thread. As I'm finishing TT and coming back to preamp, choosing caps is back as an question.
First , couple of statements about my experience and learning:
- Filter caps are different story than coupling and decoupling caps, so only about filters.
- I have great preference for PS capacitors as it has been proven many times that they are closest to ideal. I disregard all snake oil audiophile capacitors.
- I also have preference to extended foil capacitors vs tab terminated, since later should theoretically show inductance and extended foil shouldn't
- still I did not consider MLCC as NGO for filters, probably some ancient prejudice, in any case, this is only about film - foil
In recent looking about others implementation of RIAA filters, I have seen many classic PS "cylinder bugs" installed, so I wonder how they perform comparing to my preferred RIFA PFE extended foil 1% caps...
Here is short take:
About measurements:
My input card ADC is 192/24 capable, which is still limiting frequency at 96 something kHz , I have no means to measure above so I can just catch corner of capacitor knee.
Simple 1st order filter is created, Input signal of 970 mV feed through 9k6 resistor in series with DUT capacitor. Scope input is across capacitor.
I run 20kHz to 100kHz sweep and recorded trace, 1/24 smoothed to remove digital artifacts...
DUT's are, in close but not exact nF values:
top : preffered RIFA extended foil PFE, 4n57 1% , green trace
next: classic "bug" tab terminated 5n6 10% yellow trace
next: PP ERO 33n +-5%, MKP 1845 , red trace
Bottom: PP ERO 3n3 MKP1846, orange trace
Now order of above picture is mixed up due capacitors values:
What I read is, polystyrene capacitors show perfect linear behavior ( green and yellow).
I cannot say that deviation of the curve close to 96kHz is because of impedance or my ADC limitations, anyway it is far above audio frequency.
In any case , both PS types seems to be perfect for filter.
On the other hand, by many tests next to perfect polypropilene , MKP (red and orange trace) , shows quite bit of deviant characteristic vs PS
Hi Mark, correct, something was wrong with orange (MKP), here again, 5 sweeps to ensure all computer garbage is removed, tightened contacts. The step down at 56k is gone, but still not very linear cap. 2 flat Polystyrene cap traces I got from first and only go.
Mark, I admit you are right!
To increase resolution and kind of avoid my computer slowness, I increased sweep time to maximum 60sec. Than took 2 of each measurements of PS and MKP capacitors.
Here on graph overlapping traces are from same capacitor, with irregularities coming just from too slow computer. Now both show straight lines, except from measurement computer issues... green and orange are PS, blue and brick are PP.
Still over 90khz it is ADC limitations so don't bother to look...
It seems it is science on its own how to measure audio things with ADC, supposedly cheap and cheerful.... Yeah, right
Cheers!
To increase resolution and kind of avoid my computer slowness, I increased sweep time to maximum 60sec. Than took 2 of each measurements of PS and MKP capacitors.
Here on graph overlapping traces are from same capacitor, with irregularities coming just from too slow computer. Now both show straight lines, except from measurement computer issues... green and orange are PS, blue and brick are PP.
Still over 90khz it is ADC limitations so don't bother to look...
It seems it is science on its own how to measure audio things with ADC, supposedly cheap and cheerful.... Yeah, right
Cheers!
Been a while and I revisited capacitors briefly, at least figured how to measure FR without computer interrupting with it 🙂. In REW, measurement window (not RTA) and longest possible sweep time. Now results make sense, and all behave similar up to 80kHz measurement limit.
What I discovered, well , almost nothing. All usually good capacitors behave the same !
What I discovered, well , almost nothing. All usually good capacitors behave the same !
- all capacitors except top trace are 3n3 or 3n9, PS and PP.
- Top trace is different animal for comparison, ceramic disc for RF suppression, and here we can see it is visibly more hairy trace than recommended caps.
- Bottom trace is actually 2 traces, but so precisely overlapping that its impossible to separate them. One is 3n9 10% usual PS little barrel of rolled foil, other is 3n92 1% RIFA extended foil cap (my preferred for filters, until now).