Frustrating, but part of having pets. I once had a Cat that caused me to find a different place to store records. Dear thing, but she loved to use the tops of album sleeves for a scratching surface.
Oh well. You know, as dear as all those albums are, I would take them all to the driveway and light the whole pile on fire to have her back. Such are pets.
Russellc
I'm currently building a board with dipswitches for different loading and gain. On this board I will also place a series capacitor for R14 to stabilize dc offset. Will 100uF do? This is the largest Silmic II I have, alternative would be 220uF Panasonic FC or FM. Should I bypass this with a film cap? Which value? I have 0.1, 0.33 and 1 uF on hand.
Putting a capacitor in series with R14 will allow the gate of Q5 to float.
Wayne gave guidance of values between 47 and 470uF, and suggested a small film bypass. I used a 220uF Silmic II bypassed with a 0.1uF film cap and I get my output offset stable to less than 1mV.
If I wanted to build a Pearl 2 in an narrow width enclosure (or one for the PSU and one for the Phono) to match the ACA 1.6 would there be any harm in stacking the two boards with suitable standoffs? Big caps could be re-located off board?
Looks like Galaxy 3U/ or 4U might have space for two stacked PCB
Looks like Galaxy 3U/ or 4U might have space for two stacked PCB
My bad -- the bias on the gate with R14 grounded will be approximately 1/101 (R14/(R14+R15+R16)) of the DC voltage the junction of R16 and R17.
With a cap in series with R14, the bias on Q5 should be the DC voltage at the junction of R16 and R17.
Hi,
I am slowly progressing with building the Pearl 2. I have completed the boards and the voltages all check out fine.
I have also successfully built a power supply using the DIY audio power supply board. I am using a 2x24V tranformer which produces 2x27V AC, and then the PS makes that +/- 37V DC. Is this too much voltage for the Pearl 2 regulators to handle? I am using the regulators as specified in the BOM. Any input would be helpful.
I am slowly progressing with building the Pearl 2. I have completed the boards and the voltages all check out fine.
I have also successfully built a power supply using the DIY audio power supply board. I am using a 2x24V tranformer which produces 2x27V AC, and then the PS makes that +/- 37V DC. Is this too much voltage for the Pearl 2 regulators to handle? I am using the regulators as specified in the BOM. Any input would be helpful.
I think you should be fine. I am using 2x24V transformer as well. Power supply voltage will decrease when loaded due to transformer regulation and resistance in CRC filter. Also, there is 5Ohms before regulators on Pearl 2 board.
Thanks for the response. Have you ever measured the voltage at entry to the Pearl 2 boards? The +/- 37V I’m getting is past the CRC filter.
Is your +/-37V without a load? If so, then it is entirely reasonable and it will drop
with a load attached. For one thing, without current draw there is no voltage drop
across the 'R' in your CRC.
Also, assuming a small-ish transformer (say 50VA or so), the unloaded voltage can
be a good 10-20% higher than its nominal figure.
Cheers,
Dennis
with a load attached. For one thing, without current draw there is no voltage drop
across the 'R' in your CRC.
Also, assuming a small-ish transformer (say 50VA or so), the unloaded voltage can
be a good 10-20% higher than its nominal figure.
Cheers,
Dennis
Probably, but I haven't made any notes. I think it is about 32VDC under load. Note that I am using CRCRC filter, where R = 10 Ohms. See here: diyaudio | Power Supply
Thanks Dennis and qwertyl.
Yes, 37V is without load, I suppose I’ll hook it to the Pearl 2 boards and see what goes.
The powersupply I am using is CRC on the diyaudio board. It is waaaay overbuilt for a phono stage, mostly because I used parts I had from other projects that never materialized, and, anyway, what’s diy for if not overbuilding thing?
The transformer is 100VA, the capacitors are 8x15000μF, the resistors are 4x1Ω on each side.
I’ll hook it up and report back. Many thanks for your help!
Yes, 37V is without load, I suppose I’ll hook it to the Pearl 2 boards and see what goes.
The powersupply I am using is CRC on the diyaudio board. It is waaaay overbuilt for a phono stage, mostly because I used parts I had from other projects that never materialized, and, anyway, what’s diy for if not overbuilding thing?
The transformer is 100VA, the capacitors are 8x15000μF, the resistors are 4x1Ω on each side.
I’ll hook it up and report back. Many thanks for your help!
Good stuff!
One thing you might consider later on is to increase the resistance on
your PS board to burn more voltage (and lower the ripple further) before
hitting the Pearl 2 PCB and regulators.
Cheers,
Dennis
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You can play around a bit with various resistors and measure the voltages before and after the on-board regulators. I did this with mine and found that the voltage after the regulators stopped increasing as I raised the voltage into the regulators above 26v. Having a few more volts going into the regulators certainly won't hurt anything.
Thanks Dennis - would those be the pair R1/R2 and R30/R32? Should I worry also about R3/R4 and R31/R33? What would be an appropriate value? 2x20Ω?
Eric - thanks for the comment. I had the same observation when I used a bench power supply, which shows the regulators are doing what they are supposed to do. I am trying to not overstress them, leading to too much heat dissipation and damage.
Eric - thanks for the comment. I had the same observation when I used a bench power supply, which shows the regulators are doing what they are supposed to do. I am trying to not overstress them, leading to too much heat dissipation and damage.