Hi,
I was just wondering if anyone has built the Pearl 2 with a 4 conductor
umbilical cord, with the 4th connecting the power supply chassis to the
preamp chassis? Does that make any sense?
In other news, I ended up ordering the Hammond cases and cardas
post from Partsconnexion so I should be able to pick them up next week.
I found out that I forgot to order the zvp3310 from Digkey last week.
Must remember to add that to Mouser order...
Dennis
Yes i did it same way.
See my experience here
http://www.hifivision.com/showthread.php?p=492968
Post#19
PS chassis and transformer shield is earth grounded. DC zero volt is connected to earth ground using bridge isolator. Thus both chassis are earth grounded through shield of 3 core wire. Same time DC 0 volt line and rca ground are isolated from chassis.
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I started collecting parts some time ago. I was looking for a ground post and wanted something nice. I foung this one. It is very nice (and cheap, so I bought another for a possible future project):
1877 PHONO Ground pole 4mm Gold plated 24k - Audiophonics
Interestingly, the guys at Partsconnexion sell the same post at a much higher price:
GNDPOST Grounding Post Gold Plated
I have not yet started on the preamp itself but I have completed the external powersupply (2 x 22V 50VA toroid followed by CRC 10000uF, 10R, 10000uF). For the umbilical I used a 4 pin XLR (that way I can never confuse it with 3 pin XLR used for audio signals). They are relatively cheap and the current requirements for preamps are not high.
Pins 1-3 for +, - and SGND, shield connected to chassis.
1877 PHONO Ground pole 4mm Gold plated 24k - Audiophonics
Interestingly, the guys at Partsconnexion sell the same post at a much higher price:
GNDPOST Grounding Post Gold Plated
I have not yet started on the preamp itself but I have completed the external powersupply (2 x 22V 50VA toroid followed by CRC 10000uF, 10R, 10000uF). For the umbilical I used a 4 pin XLR (that way I can never confuse it with 3 pin XLR used for audio signals). They are relatively cheap and the current requirements for preamps are not high.
Pins 1-3 for +, - and SGND, shield connected to chassis.
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Pearl 2 design for MM cartridges: I've been observing high THD on the 2 which I have built on the PassDIY boards. Went back to the simulation and ran an FFT on the AP with 3mV (cyan) and 100uV (green) signals. Baseline is red.
Chart to the left is simulation in Multisim. Red is the output node, green is the output at the collector of Q3.
Chart to the left is simulation in Multisim. Red is the output node, green is the output at the collector of Q3.
Attachments
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Out of curiosity, how does your Pearl 2 sound? Does something sound bad/wrong with it? Mine sounds glorious, but as I have previously noted here, I am not set up for these measurements as many are.
Russellc
It's sitting on the bench at the moment! I have about a dozen RIAA amplifiers and at present have the "His Majesty's Voice"/Technics/Denon 103 running in the Family Room and a Linn LP12 and Linn K18 in the Little Room.
Perhaps you can glean some info on the overload margin of the Pearl 2 second stage from the chart below. The X-axis is input to the second stage with the compensation network removed:
Attachments
Is that a different version of SY's "His Master's Noise"? What are the differences?
Slightly OT: Are you ever going to have PCB for it again?
Did you compare it side by side with another RIAA preamplifier?
In any listening test, you have to control for the output level, and even 0.5dB difference will make a very significant impression upon the listener. The Pearl 2 is rated for +55dB, most MM preamplifiers are +35 to +40dB.
Overload margin is a significant issue -- from the HMN article:
4. Freedom from overload and blocking. This is another point where "classic" circuits fall flat. Let the cartridge mistrack or rattle slightly, whack the rock and lever that we laughingly call a "stylus and cantilever," and that 50kHz ding-dong resonance kicks the input stage in the groin- remember, magnetic cartridges are velocity sensitive, and though the mistrack is only momentary, that tip resonance is a lot of velocity. A minor disturbance (a swift kick) can turn into hundreds of milliseconds of overbias (rolling on the ground, gasping for breath).
Yes, I just told about comparing to what I've had previously, third time: Have you actually listened to it? I assume you have, what did you note awry with the sound? Maybe I dont know what to listen for, which very well may be the case.
To my untrained ear it has sounded wonderful, most all other builders agree. While I can fault my ears, I wont assume all other builders dont know what they are listening to?
What did your ears tell you? I will be happy to see if I can hear it as well. I've had Ortofon Super OM-30, Shure V15VXmr, and about to attach Zobel to allow SAE 1000Lt, HOMC. So far I dont hear any compression, or other weirdness...what is it you hear (not measure) that is problematic? You are giving me "Tin ear complex" as I obviously dont know what sounds good, but darn it all I thought this did! LOL Please do tell what problems you have heard with it in actual play back, seriously I am dieing to know!
Russellc
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Hi there,
Your values fit with the calculator, but only when Ro from first stage is zero. I expect it to be 500R (wrong?), and this total value of R1 of 7310R gives the following:
R2=1063R
C1=299nF
C2=103nF
Considering the original Pearl values, with R1=6250R, this gives:
R2=909R
C1=350nF
C2=120nF
close to actual BOM values....the first stage Ro was perhaps mistakenly substracted instead of added to the R1 6800R value?
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Pass DIY Addict
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Just listening to my pearl II for the first time right now. I have to say that I'm really impressed! My memories of vinyl are 30 years old, but are filled with crackles and pops and sound that didn't impress for quality. It was such a "relief" to make the move to CDs...
I've been scavanging albums from the flea markets for weeks at $1-2 each. I ran a handfull of them through a cheapie record cleaner this afternoon and I can't believe how nice Chris Rea sounds as he goes round and round on my turntable! Not a single click or pop thus far, just beautiful music! Wow! David Bowie sounds awsome, too! (Just switched albums...)
Right now, the Pearl is connected to an old Marantz receiver that powers my upstairs system while I finish my BA-3 pre.
I've been scavanging albums from the flea markets for weeks at $1-2 each. I ran a handfull of them through a cheapie record cleaner this afternoon and I can't believe how nice Chris Rea sounds as he goes round and round on my turntable! Not a single click or pop thus far, just beautiful music! Wow! David Bowie sounds awsome, too! (Just switched albums...)
Right now, the Pearl is connected to an old Marantz receiver that powers my upstairs system while I finish my BA-3 pre.
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Pass DIY Addict
Joined 2000
Paid Member
Quick question: how have others arranged ground in their Pearl? Is it "normal" for the 0v pad for the power input to be connected to the unmarked gound pad in the center of the PCB? I only realized this after construction was completed so I am unsure if this is the way the board is designed or an artifact of my wiring scheme. I have a small amount of hum that I presume is the result of proximity to other equipment right now...