The high octane phono preamp

[atupi]

I used 2 resistor values to obtain 720k. Seems a hard to find value

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[h_a]

Strange - I actually don't remember that part.

As R12 belongs to the RIAA it's value is critical. Using two precision resistors to form 720k is certainly the best option.

 

[Marra]

Thanks guys I will do that.

 

[noviygera]

for the RIAA:
I can't get LCR 1200pf in USA. Can I use Mica or film caps, 1%

CD15FA122FO3F Cornell Dubilier - CDE | Mouser

or

BFC241911202 Vishay / BC Components | Mouser

 

[atupi]

I used wima fkp2 so imthink that vishay 1% is good


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[noviygera]

Two part number requests for Mouser or Farnell:
1. heatsink for QP (power supply FET)
2."thingy" that lets you easily swap in/out the Q1, Q2, Q3 transistors. Basically a female plug with three contacts.

thanks!

 

[atupi]

1: 588-WA-T220-101E or 567-262-75AB-01E is not critical if your keep input between 48-50v
2. For transistors i used this kind of thing but in the end i will solder transistors. 575-80143036

PS. Mouser codes

 

[noviygera]

atupi, thank you.
any idea what that three contact plug is called?

 

[atupi]

No idea. I'm using only this type for temp needs

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[jan.didden]

atupi, thank you.
any idea what that three contact plug is called?

Use your imagination. Google 'TO92 socket'. See attached.

Jan

 

[noviygera]

Thanks! Didn't know that was a TO92 socket.

 

[sysco55]

Ic pin socket mouser part: 855-D01-9972042

Cut and solder.

sysco

 

[atupi]

Yesterday i was playing with High Octane preamp and with another diy preamp but OPAMP based (Rod Elliot P06). After listening some songs with opamp preamp i moved to High Octane and observed the trebles are faded out and started playing with loading resistors. In P06 i use standard 47k loading resistors the same in high octane but it seems high octane have a different behaviour regarding loading. Can someone explain to me why is that ?
I use a MM Nagaoka MP110.

 

[curryman]

Input loading resistor R1 is specified as 100k for the High Octane since the bjt input impedance is effectively in parallel (AC coupled). See post #96.
Therefore with R1 = 47k effective input resistance is somewhere arround 47k||(~100k) = ~ 32k.
kind regards, Daniel

 

[atupi]

I did not installed the 100k input resistors.

From post #96 i should understand that with 100k installed i have a 47k input impedance ?

 

[curryman]

From post #96 i should understand that with 100k installed i have a 47k input impedance ?

Yes

 

[atupi]

Thanks for claryfing this for me! Sometimes i should read more carrefully

 

[DIYBras]

Yesterday i was playing with High Octane preamp and with another diy preamp but OPAMP based (Rod Elliot P06). After listening some songs with opamp preamp i moved to High Octane and observed the trebles are faded out and started playing with loading resistors. In P06 i use standard 47k loading resistors the same in high octane but it seems high octane have a different behaviour regarding loading. Can someone explain to me why is that ?
I use a MM Nagaoka MP110.

If sound difference persists you can consider first some difference in RIAA actual curves (eg. tolerances) between projects.

 

[atupi]

Meantime i have installed the 100k input resistor and sound is more balanced. I would really love to have the fullbodied bass from the P06 opamp phono preamp on high octane, as details and openess is nice on high octane but bass a bit shy and dry

 

[curryman]

My take on the High Octane

Finally found some time to take some Snaps (had to listen before ).

I used KSA1845, tried also BC550 but measured slightly higher noise (though still very low) and so the 1845 went in again. RIAA caps and resistors have been selected out of a dozen and final deviation is <0.5dB with channel mismatch smaller than 0.1dB.

PSU is a small DIY plug housing unregulated linear supply ~50V DC.

I like the sound, its very detailed and punchy Very nice Project, thanks a lot to Hannes

kind regards, Daniel