@jackinnj,
I am thinking in terms of overhead margin that many of these P3's are operating with too much gain.
Too much gain that is attenuated in a volume control Pot with added voltage divider noise.
Too much gain eats up overhead margin and amplifies Equivalent Input Noise.
Thanks DT
Increasing the value of the source resistor for MM. Keep the original feedback resistor schema the same.
The P3 seems optimized for MC.
I can play around with this once I get back into the workshop.
The P3 seems optimized for MC.
I can play around with this once I get back into the workshop.
This is entirely dependent on how much system gain you have… and will be system dependent.. For example, if a user has an active preamp and a power amplifier with consumer gain, say 1V to full output, then yes, there is likely too much gain overall and your statements make sense.
But if the user has a ‘passive preamp’ and a Firstwatt amp that needs 2-3v for full output, there may not be enough system gain, and your point wouldn’t apply.
In my system, to illustrate, my preamp only has 6db gain and typically I use Firstwatt-style amps, so I’m up near the top of the volume knob nearly all the time.
So it’s system dependent. In some it’s going to be ‘too much gain’, in others, will be fine.
It is relatively easy to test a different gain by just plugging in a resist on the J2 jumper.
Resistors on jumper j2 is a good idea! The circuit is stable over a broad range and that would make experimentation easy.
"Resistors on jumper j2 is a good idea! The circuit is stable over a broad range and that would make experimentation easy."
Thank you Wayne! I was wondering what I would do to parallel another 2.2k or so. I can use the dip adapter pin/socket and solder the R to the pins and push the socket over the J2 pins. 🙂
Added: May have to short across R22.
Thank you Wayne! I was wondering what I would do to parallel another 2.2k or so. I can use the dip adapter pin/socket and solder the R to the pins and push the socket over the J2 pins. 🙂
Added: May have to short across R22.
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Chassis Bottom Plate Mods
Finished modifying my preamp chassis bottom plate yesterday evening...
Added access holes for DIP switches (soldered to the bottom side of the PCB, will need slightly taller standoffs), and MC/MM gain selection slide switches. Credit to @GKTAUDIO who suggested bottom side DIP access openings earlier in this thread, it's a nice idea - very convenient if you change phono carts regularly:
I'm currently thinking I'll 3D print some cover plugs lined with copper tape to provide shielding across the access openings (should connect to the exposed steel around the perimeter of the opening), since those DIP switches are connected directly to the signal from the cartridge. So, it's a pretty sensitive node.
The gain select switches are located as close as possible to the J2 location on the PCB so those wires can be kept short. Lined 'em up with the vent slots for aesthetics. I selected E-Switch EG1201 for this - it just fits the gap between the two PCBs. Mounting holes are 4-40 tapped, and I'll probably print some spacers to stand off the switches and reduce the protruding actuator length.
You may notice some extra holes lower left - those are for another custom feature I'll post about soon. 🙂
Finished modifying my preamp chassis bottom plate yesterday evening...
Added access holes for DIP switches (soldered to the bottom side of the PCB, will need slightly taller standoffs), and MC/MM gain selection slide switches. Credit to @GKTAUDIO who suggested bottom side DIP access openings earlier in this thread, it's a nice idea - very convenient if you change phono carts regularly:
I'm currently thinking I'll 3D print some cover plugs lined with copper tape to provide shielding across the access openings (should connect to the exposed steel around the perimeter of the opening), since those DIP switches are connected directly to the signal from the cartridge. So, it's a pretty sensitive node.
The gain select switches are located as close as possible to the J2 location on the PCB so those wires can be kept short. Lined 'em up with the vent slots for aesthetics. I selected E-Switch EG1201 for this - it just fits the gap between the two PCBs. Mounting holes are 4-40 tapped, and I'll probably print some spacers to stand off the switches and reduce the protruding actuator length.
You may notice some extra holes lower left - those are for another custom feature I'll post about soon. 🙂
Attachments
Douglas Self's book "Small Signal Audio Design" discusses an active volume control circuit which is optimized and highly polished for very low voltage noise. The circuit design allows him to use a dual 1K linear taper potentiometer, whose noise is 3.1x lower than a 10K pot's noise (and 10x lower than a 100K pot's noise). In the 2nd Edition, it's Figure 13.24.
Now I don't have the book. What is the idea behind the active vol. control?
Something like this?
https://www.ti.com/lit/ug/tidu034/tidu034.pdf
Something like this?
https://www.ti.com/lit/ug/tidu034/tidu034.pdf
Look here:
https://resources.altium.com/p/baxandall-volume-control-audio
And look here in the:
book sample, scroll until you get to active volume control.
https://www.amazon.com/dp/1032366273?psc=1&ref=ppx_yo2ov_dt_b_product_details
Thanks DT
So, does this iteration really trounce the Pearl 2? Because it would take a leap to do that in my assessment.
Trounce? That seems a strong word... particularly as Pearl 2 IS a fantastic phonostage...
but probably yes.
😎
but probably yes.
😎
I don't have a P2 so won't offer a comment on that, but what I've found over the years is that incremental improvements in any part of the chain reap large rewards when combined with others. Also, it's easy to feel satisfied with what you have, but listening to another component may really open new doors to sonic quality. If you have the time and a little money, this could be a great improvement.
I concur with 6L6, it is a fantastic phono stage, but you could point out some basic perceived improvements!….
You’ve been a member here a LONG time, and you haven’t noticed that I do not, essentially ever, comment on perceived sound?
🙂
My speakers are not yours, my taste in music is not yours, what is sonically important to me may not be to you, you certainly do not have my listening room, my associated equipment is likely completely different… etc… etc… ad nauseam. So those comments are not really of value.
I have built a LOT of phonostages over the years. 10 or so, it’s a big list. And have had a number of commercial products as well.
Pearl 3 is my favorite, and I don't think it’s just ‘newest project syndrome’ anymore. It’s a fantastic phonostage, I’m sure you’ll love it.
🙂
My speakers are not yours, my taste in music is not yours, what is sonically important to me may not be to you, you certainly do not have my listening room, my associated equipment is likely completely different… etc… etc… ad nauseam. So those comments are not really of value.
I have built a LOT of phonostages over the years. 10 or so, it’s a big list. And have had a number of commercial products as well.
Pearl 3 is my favorite, and I don't think it’s just ‘newest project syndrome’ anymore. It’s a fantastic phonostage, I’m sure you’ll love it.
@6L6
A question.
Fully understand your comment above. That´s why I wanted to ask you.......
Have you ever listened to the X-Ono/or clone in your setup??
I´m building P-3 just for the fun of it, but curious on what to expect. I´ve had the X-Ono clone (Dragan layout) for a number of
years now, and it has been the absolute best riaa stage I´ve ever had in my setup so far 😉
Any comment??
A question.
Fully understand your comment above. That´s why I wanted to ask you.......
Have you ever listened to the X-Ono/or clone in your setup??
I´m building P-3 just for the fun of it, but curious on what to expect. I´ve had the X-Ono clone (Dragan layout) for a number of
years now, and it has been the absolute best riaa stage I´ve ever had in my setup so far 😉
Any comment??
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Jim got to hear the F6 balanced monoblocks I built, in his system, with his speakers. While I know he enjoyed them in the brief listen he got, all I got out of him was "I've never heard the F6 circuit sound like this. Very nice build." He is the best type of audiophile, encouraging others to try for themselves.