Another Super High End Phono Stage! No expense spared...

Pio1980,
Thank you, those are good numbers.

Omishra,
So what is the advantage for more supply voltage?
Better response by preventing voltage decline(s) vs. battery V loss. (kinda like tubes within their preferred voltage curve) (I'm going by what I have read, not personal experience)
Greater available current? (i'm guessing)

Ron
 
Higher output level potential, possibly more headroom with a "loud" cart. Modern IC's appear to operate within their parameters with good consistency, tchoobs are something else.
 
I am going to try this well filtered regulated powersupply for CNC.We have planned it for CNC,B1,and Lightspeed attenuator.
[URL=http://imageshack.us/photo/my-images/266/preamppsbrd.png/] Uploaded with ImageShack.us[/URL]

Regards,
Sachin

I think that 15vdc is more than ample, I used to think 18vdc was better but it's too close to the max for most op amps. I run most of mine on 12v battery circuits and they sound fine.

Is the top section of that PCB to power a discreet front end, I guess it could be used for a muting relay?
 
Last edited:
Renron, pio1980, HT: Thanks for answering.
Most phono stages povide 145mV as max support. What kind of headroom we are talking? Naturally this gain setting will clip to 9V beyond 12mV. How much loud we can go with any cart? I am arguing that requirement of headroom in PS.

Is the top section of that PCB to power a discreet front end, I guess it could be used for a muting relay?

@ HTThat is for +18,0 to be used for PASS B1 in our case. I omitted that auto mute function as not required for our use case of LDR Volume Control, PASS B1 and CNC MM Phono stage.
 
I'm wondering about the supply voltage versus the need for a phono stage. The input is in mV and the output is typically mV, on a crescendo maybe 2VPP. The data sheet on the AD823 says it can take a +/-3V to a +/-36V rails.

Looking at it logically the CNC should run as well on the 3V power supplies as 36V power supplies. The quiescent current doesn't change with the supply voltage, it is constant. Only the maximum output voltage is changed with the supply voltage.

Just how much voltage should a phono stage produce peak to peak?
 
If the gain is 50 to 1 and the cart puts out, say 10mv on peak crescendos at the highest part of the response curve, the output will be ca 5V P/P. I'd want my rail voltage to leave the chip a comfortable P/P margin, theoretically 18V (9V X2) under these cdx should be more than sufficient if I have it right.
Anyone?
 
I just ordered the digikey parts to make a CNC. I didn't want to bother with getting my hands on a PCB (sorry) and I think that the craftsmanship that goes into making something like this without a PCB is part of the fun. I like the idea of using a separate op-amp chip for each channel, and I may do it that way. Can't wait to hear how this sounds.
 
If the gain is 50 to 1 and the cart puts out, say 10mv on peak crescendos at the highest part of the response curve, the output will be ca 5V P/P. I'd want my rail voltage to leave the chip a comfortable P/P margin, theoretically 18V (9V X2) under these cdx should be more than sufficient if I have it right.
Anyone?

CD standard is 2V output. Many phono stages, maybe not the CNC, have a lower output than a standard CD.

I have been burning in a CNC for a week. Periodically I check the output (feeding a 10k load) and it typically is ~40mV per channel. Of course I'm playing music not steady tones. Maybe I should try some tones from a test CD and see what is coming out?

Knowing how OAs work I don't see the need for a P/P margin. What am I missing?
 
Last edited:
Overload on dynamic peaks. Most power amps are rated at full output @ 2V P/P in, but some are less sensitive. That's like 1.25V each rail on the line stage's chip in theory. So a pair of basic Lithium cells should do if 3V X2 is OK with the chip maker.
The point is that if the chip maker doesn't specify "the higher the better", a moderate rail voltage span should be sufficient for proper operation of our DIY phono and line stages.
 
Last edited:
I'm still sticking to the 9V batteries for now but wondered if that much was necessary. There was little mention in the AD specsheet I read yesterday about it other than the output could run from rail to rail.
 
If it truly runs "rail-to-rail", 2x 3V Lith cells can produce 6V P/P max output with no headroom over that. If you never expect to need more than ca 3V P/P drive, I'd think that should do it if the chip is OK with this rail voltages.
 
I agree. I can only imagine there are a few mV loss through the O/A but that should suffice. I'll give it a try soon and see if I hear any loss.
 
Hi,
Can someone direct me of SSP BOM?

Regards,
Sachin

Qty Value ------ Device------------- Parts
2 X 0.1uF/50V -- Ceramic-025X050---- C9, C10
2 X 2.2uF/100V - Poly-062X184 ------ C19, C20
2 X 8K2 -------- .25W, 1% MFR ------ R28, R30
2 X 10K -------- .25W, 1% MFR ------ R27, R29
2 X 10uF/35V ---- Electrolyte Cap -- C11, C12
2 X 100 -------- .25W, 1% MFR ------ R31, R32
2 X 100K ------- .25W, 1% MFR ------ R33, R34
1 X AD823 ------ AD823OP AMP ------- IC3
 
Qty Value ------ Device------------- Parts
2 X 0.1uF/50V -- Ceramic-025X050---- C9, C10
2 X 2.2uF/100V - Poly-062X184 ------ C19, C20
2 X 8K2 -------- .25W, 1% MFR ------ R28, R30
2 X 10K -------- .25W, 1% MFR ------ R27, R29
2 X 10uF/35V ---- Electrolyte Cap -- C11, C12
2 X 100 -------- .25W, 1% MFR ------ R31, R32
2 X 100K ------- .25W, 1% MFR ------ R33, R34
1 X AD823 ------ AD823OP AMP ------- IC3

For the 2.2uf caps I used Panasonic ECW-F2225JA Polypropylene's I wouldn't use Polyester's in this case.
 
For the 2.2uf caps I used Panasonic ECW-F2225JA Polypropylene's I wouldn't use Polyester's in this case.

Would you be willing to list out a BOM, with parts that you'd order (from Mouser or wherever?) like you did for the CNC? I found that quite helpful when ordering as Mouser and Digikey are scary places for someone like me (who has no idea what is a good or bad cap, resistor, etc.).
 
Back
Top Bottom