Pass DIY Addict
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I just changed the source resistors on Q6-Q9 from 10R to 20R. This reduces the bias point from 6.5mA to about 5.3mA (about 20% reduction). This seems to have made a larger impact than fiddling with the cartridge alignment. My jFets are all matched at about 8.9mA, so they are clearly not operating beyond their sweet spot. I need to spin a few more albums now...
Just build the ONO would be my recommendation as well. There are a lot of moving parts when using active RIAA compensation including R14 which loads the network and should be AC coupled to ground...
This lowers the gain of the first stage a bit, probably reduces distortion.
In any event, the active would require a voltage amplification stage because the gain isn't sufficient.
Gain question again.
My setup:
Benz Ace SL (0.4 mV) – Pearl II phono (R14 @ 450R, so must be >60dB) – DCB1 buffer – TSSA 50W amp – 89.5 dB sensitive speakers. The listening room is rather small – 18 squares in the attic.
When the listening level is set, I can hear a slight hiss noise near the speakers, that I can't tame. I suspect it's because I force the phono to run on a rather high gain. Or can it be because I raised source resistors to 20R?
The noise is confirmed with TT unconnected and different interconnect cables. I'm sure the hiss is coming from Pearl II.
Another problem is that dynamics can't equal my digital setup.
Possible solutions:
1. Lowering phono gain, and adding a SUT ($$$)
2. Lowering phono gain, changing the cart to 0.8 mV ($$$)
3. Lowering phono gain, changing the buffer into preamp with some gain (Salas is preparing a new one!)
4. More efforts to kill the noise, upping the gain to 65 db (R14 @ 300R) (cheapest, but the least likely solution )
5. Changing the phono
What would you do in my place?
My setup:
Benz Ace SL (0.4 mV) – Pearl II phono (R14 @ 450R, so must be >60dB) – DCB1 buffer – TSSA 50W amp – 89.5 dB sensitive speakers. The listening room is rather small – 18 squares in the attic.
When the listening level is set, I can hear a slight hiss noise near the speakers, that I can't tame. I suspect it's because I force the phono to run on a rather high gain. Or can it be because I raised source resistors to 20R?
The noise is confirmed with TT unconnected and different interconnect cables. I'm sure the hiss is coming from Pearl II.
Another problem is that dynamics can't equal my digital setup.
Possible solutions:
1. Lowering phono gain, and adding a SUT ($$$)
2. Lowering phono gain, changing the cart to 0.8 mV ($$$)
3. Lowering phono gain, changing the buffer into preamp with some gain (Salas is preparing a new one!)
4. More efforts to kill the noise, upping the gain to 65 db (R14 @ 300R) (cheapest, but the least likely solution )
5. Changing the phono
What would you do in my place?
Hi Siberia,
hmm, if I remember my Pearl 2 setup correctly than voltages at NPN transistor Q3 are crucial. It should be: V collector > V base > V emitter, but it is slightly upside down in your case, so it might not be correctly forward biased. Maybe you should try to adjust the voltages by lowering R10 (another resistor in parallel). Why did you increase R21-R24 from 10 to 20 Ohms? Because of that? Maybe stick with the 10 Ohms original and have R10 decreased to say 5k? Just an idea.
Cheers
Michael
hmm, if I remember my Pearl 2 setup correctly than voltages at NPN transistor Q3 are crucial. It should be: V collector > V base > V emitter, but it is slightly upside down in your case, so it might not be correctly forward biased. Maybe you should try to adjust the voltages by lowering R10 (another resistor in parallel). Why did you increase R21-R24 from 10 to 20 Ohms? Because of that? Maybe stick with the 10 Ohms original and have R10 decreased to say 5k? Just an idea.
Cheers
Michael
Michael, thanks again.
I had the lowered value R10 previously (10K // 6.8K). Which gave me these voltages
It looked OK. Sounded OK. Then I've changed the cart, upped the gain.
Had some DC problems on the output. Fixed it with radial cap.
And later while looking at Wayne's presented voltages (see attachment) of his Pearl II version,
as per some suggestions, I've raised R21-R24 to be more in the ballpark with voltages
in the input stage (previously ±65 mV; now ±110 mV) and the voltages on Q3 looks closer to Wayne's too.
I had the lowered value R10 previously (10K // 6.8K). Which gave me these voltages
It looked OK. Sounded OK. Then I've changed the cart, upped the gain.
Had some DC problems on the output. Fixed it with radial cap.
And later while looking at Wayne's presented voltages (see attachment) of his Pearl II version,
as per some suggestions, I've raised R21-R24 to be more in the ballpark with voltages
in the input stage (previously ±65 mV; now ±110 mV) and the voltages on Q3 looks closer to Wayne's too.
I run a DL-103R and Klipschorns. With my Aleph J, it was barely up to par. I since switched to a TSE 45 and the Pearl 2 does not have enough gain. I put a DL-110 on my SL-1200 and it is night and day! The dynamics are much better but unfortunately so is the detail I had in my DL-103R. I have it potted and loaded in a Paradox aluminum body. I'd highly suggest an SUT with the DL-103 and the Pearl 2.
I fed one into pearl2, then into BA3 pre and on to power amp with no problems. Fairly healthy twist on the volume knob, but plenty left.
Russellc
I don't think this is plausible, unless the cartridge is somehow defective. The Pearl has substantial enough gain for a 300uV cartridge, but put a step-up-trafo in front and it likely will overload the Pearl on high frequency peak material.
Thanks all, your replies highlight the dilemma with the Pearl 2 for me, not quite enough gain for LOMC carts but too much to allow use of step ups, not to mention the fun and games involved with matching carts to SUTs.
I may the no again and go for a Dynavector 10x5 which will play nicer with the Pearl 2.
I may the no again and go for a Dynavector 10x5 which will play nicer with the Pearl 2.
Pass DIY Addict
Joined 2000
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Nothing wrong with the cart ... I don't see how 55dB is anywhere near enough for a 0.3mV cartridge. That only puts output around 170mV.
FWIW, I'm running a Mezmerize buffer, 45 SET amp at 1.5Wpc and don't have enough gain on a pair of 105dB Khorns.
Of course you would need to match the SUT to the Pearl, so maybe a 10dB with a parallel resistor to correct cartridge loading would be ideal.
Lundahl makes great MC SUT's. Take a look here: K&K Audio | Moving Coil Step Up Guide
With the DL-103R at 0.3mV and a Step-Up Gain of 5, you are about perfect at 1.5mV into the Pearl 2. A lot of people recommend loading the DL-103R to 100 ohms but I prefer mine at 150 ohms.