I was using two Y-splitters. Right now I have a dedicated mono cartridge with the pins bridged and that works better.
What voltages do you get on the bottom of Q6-9? If it is 70mV or more, they are draining Q3. Change R21-R24 to 20R. I had about 6V on the collector of Q3 at first (but the amp worked fine...). I changed R21-24 to 20R and R10 to 8k2, now I have 8.8V on the collector of Q3 (9.3 on the base and 8.6 at the emitter).
If absolutely no music comes out of your board I suspect another fault. Check for things like a jumper for R15 and no jumper if you decide to leave out C15.
If absolutely no music comes out of your board I suspect another fault. Check for things like a jumper for R15 and no jumper if you decide to leave out C15.
Pearl One vs. Pearl Two?
I built the original Pearl a few years back. Pearl One I guess you could call it.
Just curious - has anyone done a listening comparison of Pearl One vs Pearl Two?
I know the Pearl Two can work with lower-output cartridges; but I'm curious to know if there are audible differences.
You might be interested in these tests I ran on the Pearl One PASS DIY PEARL MK 1 Audio Test
I built the original Pearl a few years back. Pearl One I guess you could call it.
Just curious - has anyone done a listening comparison of Pearl One vs Pearl Two?
I know the Pearl Two can work with lower-output cartridges; but I'm curious to know if there are audible differences.
You might be interested in these tests I ran on the Pearl One PASS DIY PEARL MK 1 Audio Test
Hi fabriciom,
as Wellerman already said, make sure Q3 is forward biased, meaning VCollector > VBase > VEmitter. If that is not the case, change (reduce) R10 to 8kOhm or even lower. This might be necessary, if too much current flows through the JFETs, which can also be reduced by increasing R21-R24 to 20 Ohms.
All the best
poli
as Wellerman already said, make sure Q3 is forward biased, meaning VCollector > VBase > VEmitter. If that is not the case, change (reduce) R10 to 8kOhm or even lower. This might be necessary, if too much current flows through the JFETs, which can also be reduced by increasing R21-R24 to 20 Ohms.
All the best
poli
Jfet Idss question
More than 4 years ago I bought the boards and Jfets from Pass Diy and the other parts from Mouser and Digikey. Due to circumstances everything was boxed up and put on the shelf. Now I am finally able to get back to it
The resistors, small caps, ztx450's and zvp3310 were already installed on the boards, so while I wait for my new solder to arrive I started re-reading the thread (I just read that C7 will have to be removed).
Some time ago I bought the last 7 unmatched Toshiba 2SK170BL Jfets a local supplier had left in stock (for less than $1 each) and tested them using this procedure http://www.diyaudio.com/forums/pass-labs/141162-2sk170-matching.html#post1784617 to see if I could pair them up. I also measured the Jfets that came with the Pearl 2 boards and noted their values (mV; I used a 10V bench PSU):
4 x 2SK370GR bag 1
352
331
352
366
4 x 2SK370GR bag 2
427
412
423
417
5 x 2SK370GR bag 3 (one more than expected)
428
432
430
454
459
After re-reading part of the thread I am wondering if these values are optimal for the circuit. Should I use these Jfets or should I get some with higher Idss? What Idss would be ideal? How close should they be mactched?
Thanks,
Albert
More than 4 years ago I bought the boards and Jfets from Pass Diy and the other parts from Mouser and Digikey. Due to circumstances everything was boxed up and put on the shelf. Now I am finally able to get back to it
The resistors, small caps, ztx450's and zvp3310 were already installed on the boards, so while I wait for my new solder to arrive I started re-reading the thread (I just read that C7 will have to be removed
).Some time ago I bought the last 7 unmatched Toshiba 2SK170BL Jfets a local supplier had left in stock (for less than $1 each
) and tested them using this procedure http://www.diyaudio.com/forums/pass-labs/141162-2sk170-matching.html#post1784617 to see if I could pair them up. I also measured the Jfets that came with the Pearl 2 boards and noted their values (mV; I used a 10V bench PSU):4 x 2SK370GR bag 1
352
331
352
366
4 x 2SK370GR bag 2
427
412
423
417
5 x 2SK370GR bag 3 (one more than expected
)428
432
430
454
459
After re-reading part of the thread I am wondering if these values are optimal for the circuit. Should I use these Jfets or should I get some with higher Idss? What Idss would be ideal? How close should they be mactched?
Thanks,
Albert
Last edited:
Yes.
In #617 Nelson says between 6 and 10mA.
In #620 nar says high GR (5-6mA) will also work.
Wrong question. What Idss is best for this circuit (without changing any resistor or cap values). How closely matched?
Pass DIY Addict
Joined 2000
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I've been enjoying my Pearl 2 for a while now (built stock and used with an AT-150MLX MM cartridge that has a 5.0mV output level). It feeds a BA-3 preamp (with LDR-based volume control) that drives an F4 amp. I buy all of my albums at the flea market and then wash them with a Spin Clean record washer.
Many of albums sound GREAT, but there are an increasing number of albums that sound distorted to me. I've played around with reducing the output of the Pearl 2 by putting a resistor in the C15 position. While it does reduce the output level from the Pearl, the albums that sounded distorted beforehand still sound distorted to me. One of them was a sealed Frank Sinatra album, so it can't really be record wear that I am hearing.
I presume that some albums are just cut better than others, but I have a handful now that sound terrible. Has anyone else noticed anything like this?
Many of albums sound GREAT, but there are an increasing number of albums that sound distorted to me. I've played around with reducing the output of the Pearl 2 by putting a resistor in the C15 position. While it does reduce the output level from the Pearl, the albums that sounded distorted beforehand still sound distorted to me. One of them was a sealed Frank Sinatra album, so it can't really be record wear that I am hearing.
I presume that some albums are just cut better than others, but I have a handful now that sound terrible. Has anyone else noticed anything like this?
Pass DIY Addict
Joined 2000
Paid Member
Hello Eric,
You mean R15 not C15 I guess
With that particular cart you throw too much level into Pearl II to get undistorted at the output at stock gain setting, this is why on high level records you get saturation.
You should keep the looped gain down- it's unlikely the 1st stage that overloads -
With 5mV cart you may try to lower the looped gain by 40 dB total, it still gives a x100 voltage so about 0,5V at line outputs, comfortable to use everyday.
To do this just use the maths. R15 is a piece of wire unless you want more gain, so adding a resistor here will increase your 'problem' instead of curing it.
(This feature is reserved to MC low output cart owners to get their sound level back).
If you add more R to R15 print (series with R16) you push up closed loop gain (and get closer to open loop in fact, so higher noise, distortion and such).
Basically, gain of the 2nd stage is ratio of R16/R14 so 100/1 means x100 stock so 40 dB. Plus gain on the first stage with is about 15 dB if I can recall.
Maybe 5mV with 40 dB gain on the 2nd stage (and about 55 total) will be too much for your ears for a real 'clean' sound.
So, you can lower R16 to about 66k to get about 36 dB gain on that stage, sufficient with your cart. To do so, either change R16 with desired value, or just parallel a 200k to R16.
After doing this, recheck DC points and 0V after warm-up as a different gain setting can affect points.
Keep us informed about the sound
Best,
nAr