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Pearl Two
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Old 2nd April 2019, 08:09 PM   #2921
exojam is offline exojam  United States
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Well after very very long 6 year break I am back to get this finished.

Years ago I pretty much finished populating the Pearl boards. I already have a B1 buffer up and running for years.

I have the transformer and the LM3886 power supply that is somewhat built.

I just need to try and find all the changes that have been made in regards to components used on the Pearl and power supply boards. Plus go back and see how everything is supposed to connect with each other, man does that sound bad.

My plan is to get a box for the transformer and power supply to keep them a few feet away from everyone else.

I plan on putting the B1, Pearl 2 along with a motor controller system I picked up from Bill Thompson into the chassis I had picked up from 6L6 years ago.

So it is back to having fun.

Last edited by exojam; 2nd April 2019 at 08:28 PM.
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Old 15th June 2019, 01:54 AM   #2922
Eric is offline Eric  United States
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Pearl Two
I've been planning to do this for a while and have finally found the time to rebuild my Pearl 2 with an internal power supply. I used an Antek AN-0225 25v 25VA transformer followed by a Salas BiB v1.3 regulator. I used 3R bias resistors for a 200mA supply for each rail. The mosfets make the floor of the chassis a few degrees above body temp and the transformer warms up a little too, but not as much as the chassis floor.

I was a bit nervous about having a transformer inside the chassis, but it turned out well. I rearranged the PCBs to keep the input signals as far away from the AC wiring as possible. This worked well with no increase in noise at all. Now I can ditch a separate power supply box, so I get a space back in my audio rack.

My ongoing thanks to Wayne for such a great phono stage! Running my SL-1200 into the Pearl 2, then to a B1 Korg, into a MoFo amp and my FHXL speakers really makes a GREAT combination - lots of synergy with this setup!
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Last edited by Eric; 15th June 2019 at 02:05 AM.
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Old 15th June 2019, 07:06 AM   #2923
canute is offline canute  Denmark
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Eric:

Please explain the setup for the resistors r21 thru r24 (I can't see it clearly at the photo). What is the the attached component ?
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Old 15th June 2019, 11:43 AM   #2924
McQuaide is offline McQuaide  United States
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Very nice!
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Old 15th June 2019, 02:10 PM   #2925
Eric is offline Eric  United States
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Quote:
Originally Posted by canute View Post
Eric:

Please explain the setup for the resistors r21 thru r24 (I can't see it clearly at the photo). What is the the attached component ?
I added an additional 10R to the existing source resistors for a total of 20R. I was having a problem with my 5mV MM cardridge overloading and causing distortion. A few people here have commented that this was the wrong approach, so my next step is to return these to 10R and use the approach that Mark did with a switch on R14. One step at a time...
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Old 15th June 2019, 04:48 PM   #2926
Eric is offline Eric  United States
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Mark: when you added you gain switch to R14, had you already added the electrolytic cap to the ground side of R14 to control output offset drift? Or do you just switch the resistor load to ground for R14 as per the original schematic?

I'm wondering if the addition of the cap will interfere with swiching gain by R14.
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Old 16th June 2019, 01:09 AM   #2927
jackinnj is offline jackinnj  United States
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Eric -- you might want to consider using a "ground-loop-breaker" rather than directly connecting the ground planes of the P-II pcb's to the "green".

I think one design is shown on the F4 power supply schematic.
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Old 16th June 2019, 02:36 AM   #2928
Eric is offline Eric  United States
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Thanks, Jack - I'll give it a try and see what difference it makes. For the first iteration, I just directly connected everything to see if it caused any problems...
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Old 16th June 2019, 01:12 PM   #2929
McQuaide is offline McQuaide  United States
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Quote:
Originally Posted by Eric View Post
Mark: when you added you gain switch to R14, had you already added the electrolytic cap to the ground side of R14 to control output offset drift? Or do you just switch the resistor load to ground for R14 as per the original schematic?

I'm wondering if the addition of the cap will interfere with swiching gain by R14.

Hi Eric, I'm not familiar with the electrolytic on R14. I just replaced R14 with a switch. Works well, no noise.
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Old 1st July 2019, 10:49 PM   #2930
Alypius is offline Alypius
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Hi! Likewise, coming back to DIY after a long hiatus. I'm interested in building the Pearl 2 but Bottlehead's Eros 2 (and, to a lesser extent, their Reduction) is also attractive. Which do you guys prefer?
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