thanks Carl. that sounds like a plan. in fact i bent the pins on 1 of the opamps when installing it, and maybe broke something. I assume it makes no difference whether i am measuring current draw on the v+ or v- ?
Shouldn't make a difference. Current draw should be roughly equal from each rail.
Hi, all. I'm assembling my power supply and wanted to clarify how to mount the voltage regulators on the heat sinks. Assuming that the screw head is toward the exterior of the PCB with the nut facing to the interior, is the order:
Screw head, voltage regulator, thermal pad, heat sink, shoulder washer, nut
OR
Screw head, shoulder washer, voltage regulator, thermal pad, heat sink, nut?
Screw head, voltage regulator, thermal pad, heat sink, shoulder washer, nut
OR
Screw head, shoulder washer, voltage regulator, thermal pad, heat sink, nut?
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i removed and replaced all the opamps measuring current draw each time. with all the opamps in, the amp was drawing 158.9ma.
i took the input and output right from the preamp board bypassing the IO board. still there.
the hum/buzz is still there. it is only audible at full volume, and changes when i touch the ground wire with my finger, the hum goes 90% away. it seems like a loose ground somewhere?
i took the input and output right from the preamp board bypassing the IO board. still there.
the hum/buzz is still there. it is only audible at full volume, and changes when i touch the ground wire with my finger, the hum goes 90% away. it seems like a loose ground somewhere?
Team, has someone got some spare capacitors. I ordered as per BOM, but the BOM lists 4 100pF Polyprop WIMA's whilst listing 5 positions. As you've guest, I ordered 8 instead of 10 and am 2 short. Mouser seems to be the only one that has them and is out for another 10 weeks....
Let me know if you can help? I'm in the USA. Thanks, Rene
Let me know if you can help? I'm in the USA. Thanks, Rene
Sorry to hear you are having problems. Long-distance fault-finding is a notoriously diifficult business, but I will try.
Problems (including hum) that change when you prod them with a finger are usually due to HF instability. This seems very unlikely in the preamp if the right components are in the right place, so I would look at the PSU and check for oscillating regulators. It may be hard to see on a scope- can you change the powering over to a bench PSU?
thanks Doug. i dont have a dual bench supply, but am going to try to borrow one. i am also thinking the problem may be there. will keep you posted
Doesn't seem like a promising route to go.
Are you sure there are no ground loops? Reinforce the ground connections with thick wire (32/02) and if the hum drops ground currents are the issue.
DS preamp
Well I finally finished the case work, the preamp has been completed for several weeks. I hate drilling holes and matching everything to fit, not my cup of tea. Same goes with the lettering.
Any rate, I used one of the DIY store supplied cases, a single 1U Slimline. Works well. Next time I believe I would have someone like FrontPanel Express handle the holes and lettering.
My current setup for the past 18 months has been a Pass BA-3 into a Pass F4 amp. The amplification duty is sometimes shared with a Pass F6. As I write this I am listening to the DS pre into the F4. No noise, extremely quiet. The low end is outstanding. Since the BA-3 has no tone controls I am using the DS pre without the EQ at the moment. Sound stage is excellent along with the detail. Definitely a keeper. To my ear the Pass BA-3 has a fuller somewhat fatter sound, but either pre would do the amplifier well.
Thanks to Doug and Carl for making all of this possible.
David
Well I finally finished the case work, the preamp has been completed for several weeks. I hate drilling holes and matching everything to fit, not my cup of tea. Same goes with the lettering.
Any rate, I used one of the DIY store supplied cases, a single 1U Slimline. Works well. Next time I believe I would have someone like FrontPanel Express handle the holes and lettering.
My current setup for the past 18 months has been a Pass BA-3 into a Pass F4 amp. The amplification duty is sometimes shared with a Pass F6. As I write this I am listening to the DS pre into the F4. No noise, extremely quiet. The low end is outstanding. Since the BA-3 has no tone controls I am using the DS pre without the EQ at the moment. Sound stage is excellent along with the detail. Definitely a keeper. To my ear the Pass BA-3 has a fuller somewhat fatter sound, but either pre would do the amplifier well.
Thanks to Doug and Carl for making all of this possible.
David
Attachments
Thank you very much. I think I spent as much time on the case work and lettering as I did on building the preamp!!.
The lettering is dry transfer. The company is in the Netherlands, but Amazon is your friend. White Gothic letters by Woodland Scenic. About $9 a sheet. Buy two because you will run out of some letters or like me damage them while they are in place. There are other vendors. Just search for "dry transfer letters", plenty of choices.
The lettering is dry transfer. The company is in the Netherlands, but Amazon is your friend. White Gothic letters by Woodland Scenic. About $9 a sheet. Buy two because you will run out of some letters or like me damage them while they are in place. There are other vendors. Just search for "dry transfer letters", plenty of choices.
Just another update on the DS preamp. Loving it, the detail is incredible. Still using it with the Pass F4 amp. I feel like what the engineer recorded is being reproduced in much the same fashion.
Still like the Pass BA-3 preamp. Every bit as detailed with just a slightly fuller sound. Both preamps are keepers. The next preamp build will be the Bruno Putzey's balanced preamp.
Still like the Pass BA-3 preamp. Every bit as detailed with just a slightly fuller sound. Both preamps are keepers. The next preamp build will be the Bruno Putzey's balanced preamp.