Has any of the pearl itterations ever been reviewed by a hifi magazine? I've did a search and found zero
Reverse PSRR -- One PSU per circuit board may be better as any signal impinging on the supply line gets fed back by the error amplifier!
Less an issue today with high PSRR operational amplifiers, better understanding of current sources, low impedance power sources etc.
I have been enjoying the Peal3 with just a single PSU but noted some have had nice results and Wayne suggested give it a try with a Duel Mono setup. I was using 30,000uF 63v CLCRC but this is to much uF IMO and to high V, Im back to 4700uF 25v caps CRCRC config. As you can see I just threw this together just to see (hear) the benefit/s.
Yes there is clear sonic benefit to Duel Mono, more drive, dynamic and perceved clarity and or a deeper 3d sound stage being able to pin point vocals and instruments in the presentation without loss of musicality. Its quite a lift.
As a side note..I have used the Avondale Audio FWB3 module (bridge rectifies) these have the ability to null transformer ringing so no need for the snubbers with these PSUs.
There's lots of info here for the no believers https://pinkfishmedia.net/forum/thr...full-wave-bridge-module-bargain.287704/page-6
For those who think rectifiers just rectify, they all do it but some seem to do it better sonic job than others. Just sayin.
Yes there is clear sonic benefit to Duel Mono, more drive, dynamic and perceved clarity and or a deeper 3d sound stage being able to pin point vocals and instruments in the presentation without loss of musicality. Its quite a lift.
As a side note..I have used the Avondale Audio FWB3 module (bridge rectifies) these have the ability to null transformer ringing so no need for the snubbers with these PSUs.
There's lots of info here for the no believers https://pinkfishmedia.net/forum/thr...full-wave-bridge-module-bargain.287704/page-6
For those who think rectifiers just rectify, they all do it but some seem to do it better sonic job than others. Just sayin.
My Pearl is working well except for the front panel LEDs, which I managed to reverse my wiring at the LED legs, 
. Before I replace them, I am concerned with the voltage that I read, 20v on both sides?
. Before I replace them, I am concerned with the voltage that I read, 20v on both sides?
Also, been studying the schematic in regards to adjusting gain. My cartridge is .4mv and it seems to me that 70 dB is more than needed. First and foremost is there an improvement in noise with lower gain, I assume that lowering the value of R9 would do this? How do I determine what value would give me 60 dB?
What does the build doc say about changing resistor values for gain?
aside from the off board transformers he appears to have a pair of chassis-mounted bridge rectifiers...
"If you're interested in adjusting the gain settings for your build, please refer to the build document for the calculations." D'Oh! I was looking in the "Build Guide" No wonder I couldn't find it!
The question for me, if I replace the 2K2 w/ a 1K, will there be an appreciable improvement in noise floor/performance?
The issue is that the audio ground is connected to the 2 chassis ground connection points (corner hole & wiring point) through D6. Empty D6 - no connection. So the bridge on the chassis floor appears to have no connection to the circuit.
One way to find out! Resistors a cheap, too. And easily removed with a Hakko.
@rhthatcher
agreed. those diodes should be wired to the D6 "+" point.
on the other hand I still think this ground lift bridge might easily be wired past via the grounding in the signal chassis and the umbilical.
agreed. those diodes should be wired to the D6 "+" point.
on the other hand I still think this ground lift bridge might easily be wired past via the grounding in the signal chassis and the umbilical.
There in lies the conundrum of the subjectivist, in order to do that I would need 2 Pearls that sounded virtually the same before replacing the resistor in 1 😉. An experiment with no meaningful results bears no fruit. If there is a meaningful improvement in measured performance I would take it on faith.
Colburn mentioned lowering r9 if less gain is acceptable, less gain less noise, what levels he did not mention, I've been thinking about a rotary attenuator in r9.
Feedback changes the overall sound, at least to some extent. Changing overall gain results in less noise, so if you really
want to tweak and tune, set R9 for the minimum value you need in your particular system.
The cap multiplier capacitor (C7) can be bigger if you like.
If you have a bipolar cap for C8, you may use it there. Also worth mentioning that C8 has very little voltage across it, so even a
16V cap will be more than enough.
PSU caps near the regulators can be bigger, use whatever you have that can fit., One sometimes overlooked advantage of the
7800/7900 series regulators is how much capacitance you can hang downstream of them with the regulators not caring one bit.
Before spending lots of money on frilly boutique capacitors, buy a MEGA328 tester (Amazon has them for about $15-20) and a
bag full of 0.1uF caps that fit the PCB, then measure and match the RIAA critical ones (C3, C4) as close you can per position per
channel. Same thing with the RIAA caps, channel to channel matching Left to Right will be of great benefit, almost as good as
getting everything exactly on value. Do the same thing with the resistors.
If you have very tightly matched JFETs, or want to get a bunch and match them yourselves, you can lower the input stage source
resistors (R4 R5 R6 R7) to around 4.7ohms or even less. It might make some small difference with noise.
The loading R and C on the DIP switch can be whatever you want, the included values are just suggestions. They will, however,
get you a lot of different options. If you know your cartridge performs wonderfully with a particular loading resistor, absolutely
change one to your perfect value.
want to tweak and tune, set R9 for the minimum value you need in your particular system.
The cap multiplier capacitor (C7) can be bigger if you like.
If you have a bipolar cap for C8, you may use it there. Also worth mentioning that C8 has very little voltage across it, so even a
16V cap will be more than enough.
PSU caps near the regulators can be bigger, use whatever you have that can fit., One sometimes overlooked advantage of the
7800/7900 series regulators is how much capacitance you can hang downstream of them with the regulators not caring one bit.
Before spending lots of money on frilly boutique capacitors, buy a MEGA328 tester (Amazon has them for about $15-20) and a
bag full of 0.1uF caps that fit the PCB, then measure and match the RIAA critical ones (C3, C4) as close you can per position per
channel. Same thing with the RIAA caps, channel to channel matching Left to Right will be of great benefit, almost as good as
getting everything exactly on value. Do the same thing with the resistors.
If you have very tightly matched JFETs, or want to get a bunch and match them yourselves, you can lower the input stage source
resistors (R4 R5 R6 R7) to around 4.7ohms or even less. It might make some small difference with noise.
The loading R and C on the DIP switch can be whatever you want, the included values are just suggestions. They will, however,
get you a lot of different options. If you know your cartridge performs wonderfully with a particular loading resistor, absolutely
change one to your perfect value.
Thank you, that's a bit for me to digest, but quite clear and helpful, I suspect others may benefit from your insights!
Left to my own devices my eyes would have glazed over long before I found that. Thanks Wayne, very clear and concise and thanks @amplidude for taking the time to help!
We diy addicts must stick together, when look through threads and find interesting info I always save it as pdf.