Hi X,
Made a start this evening, as follows, reference your points to check:
1. Disconnected buffer board ground connector - hum got even louder! So, connector reinserted and hum reduced to as before again. Note connection is to RME ADI-2 fs DAC ...
2. I measure ~ 0.2 ohms from SMPS pcb securing screws (secured to plate) to star ground point, also same reading from plate securing screws (secured to my 10mm steel stand-offs, which are in turn secured to chassis base), which suggests good grounding in place. However, point taken about anodizing so will add separate ground wire once SMPS has fully discharged as I don't want to work on it whilst it still contains some 'juice' - I note that after switching mains power off it takes around 30 minutes for the cap charge to fully dissipate!! So probably in morning for this one now.
3. TPA3255 ground is already connected to star ground point, and measures ~ 0.0 ohms
4. Also will await full discharge of SMPS before removing TPA3255 board to check regards heatsink. In the meantime, I measure 5.5 ohms from heatsink fixing screws to star ground point. Is that normal?
5. Confused by your statement "Where is analog signal ground located? The best place to get it ......" Am I supposed to have picked that up from these locations and connected somewhere else?? In the meantime, I think I've made the connections between buffer and amp boards correctly, as shown in the attached sketch. Should I have done something else as well? Without any connection or wiring drawing to go by, I've simply copied what I've seen others do!
I'll carry on tomorrow and report back again after attending to points 2 & 4 .......
Made a start this evening, as follows, reference your points to check:
1. Disconnected buffer board ground connector - hum got even louder! So, connector reinserted and hum reduced to as before again. Note connection is to RME ADI-2 fs DAC ...
2. I measure ~ 0.2 ohms from SMPS pcb securing screws (secured to plate) to star ground point, also same reading from plate securing screws (secured to my 10mm steel stand-offs, which are in turn secured to chassis base), which suggests good grounding in place. However, point taken about anodizing so will add separate ground wire once SMPS has fully discharged as I don't want to work on it whilst it still contains some 'juice' - I note that after switching mains power off it takes around 30 minutes for the cap charge to fully dissipate!! So probably in morning for this one now.
3. TPA3255 ground is already connected to star ground point, and measures ~ 0.0 ohms
4. Also will await full discharge of SMPS before removing TPA3255 board to check regards heatsink. In the meantime, I measure 5.5 ohms from heatsink fixing screws to star ground point. Is that normal?
5. Confused by your statement "Where is analog signal ground located? The best place to get it ......" Am I supposed to have picked that up from these locations and connected somewhere else?? In the meantime, I think I've made the connections between buffer and amp boards correctly, as shown in the attached sketch. Should I have done something else as well? Without any connection or wiring drawing to go by, I've simply copied what I've seen others do!
I'll carry on tomorrow and report back again after attending to points 2 & 4 .......
Attachments
Well, I'm stumped!! It's not often I'm forced to admit defeat, but for the moment at least this seems to be the case. I'm happy to live with the amp using XLR because it sounds fantastic, but it's so frustrating that I can't get to the bottom of what's causing my excessive RCA hum!
Just to clarify - I've been retired a few years so I might be a little rusty, but my career of close to 50 years was predominantly as a telecomms/electronics engineer, so I have a reasonable understanding of circuits, etc. (although not so much audio apart from my several amp builds). Even so, I can't figure this one out.
I've now followed through all of your recommended checks and suggestions, X, and then some ..... nothing makes any difference at all. Again thinking it must surely be a ground loop issue somewhere, I even hard-wired directly from DAC RCA output ground (-) to TPA3255 star ground - again, no difference whatsoever, not a jot!
The only thing I'm slightly concerned about is my consistent reading of about 5.5 ohms from TPA3255 heatsink to ground (it's definitely not shorting - I checked again). Is that normal? Without circuit diagram I'm unable to check, so if you could kindly confirm?
Only other thing I can think of to try now is maybe to introduce a ground loop isolator into the RCA circuit, something like the Art Pro Audio DTi for example, or maybe build one, and see if that works,?
Unless you, or anyone else, has any other ideas!
Meanwhile, I've closed everything up and 'shoe-horned' the amp back into its cupboard shelf resting place so the room looks neat and tidy again, and I'll continue to enjoy the great sounds using XLR ....
Thanks so much for your help,
Richard
Just to clarify - I've been retired a few years so I might be a little rusty, but my career of close to 50 years was predominantly as a telecomms/electronics engineer, so I have a reasonable understanding of circuits, etc. (although not so much audio apart from my several amp builds). Even so, I can't figure this one out.
I've now followed through all of your recommended checks and suggestions, X, and then some ..... nothing makes any difference at all. Again thinking it must surely be a ground loop issue somewhere, I even hard-wired directly from DAC RCA output ground (-) to TPA3255 star ground - again, no difference whatsoever, not a jot!
The only thing I'm slightly concerned about is my consistent reading of about 5.5 ohms from TPA3255 heatsink to ground (it's definitely not shorting - I checked again). Is that normal? Without circuit diagram I'm unable to check, so if you could kindly confirm?
Only other thing I can think of to try now is maybe to introduce a ground loop isolator into the RCA circuit, something like the Art Pro Audio DTi for example, or maybe build one, and see if that works,?
Unless you, or anyone else, has any other ideas!
Meanwhile, I've closed everything up and 'shoe-horned' the amp back into its cupboard shelf resting place so the room looks neat and tidy again, and I'll continue to enjoy the great sounds using XLR ....
Thanks so much for your help,
Richard
Hi X,
just a short question again, because I want to finish the amp (LEDs...).
My smps is the normal version and you told, that you use the custom version with connector for an smps-error LED (and Richard's version has this connector too...). Can you confirm based on the following picture, that your connector is soldered into the two marked holes? If so, what voltage is there with what polarity in case of an error (or what kind of LED is required there voltage-wise with what resistor). Many thanks. With this info I could solder two wires into the holes and that's it.
(I wrote to Samy too, earlier, but his answer wasn't too exact and I didn't want to torture him any further)
just a short question again, because I want to finish the amp (LEDs...).
My smps is the normal version and you told, that you use the custom version with connector for an smps-error LED (and Richard's version has this connector too...). Can you confirm based on the following picture, that your connector is soldered into the two marked holes? If so, what voltage is there with what polarity in case of an error (or what kind of LED is required there voltage-wise with what resistor). Many thanks. With this info I could solder two wires into the holes and that's it.
(I wrote to Samy too, earlier, but his answer wasn't too exact and I didn't want to torture him any further)
Hi Plott,
Yes, that's the connector location - here's a photo of mine, for reference.
Regards LED I used a bog standard LED, rated at 2v forward voltage, 20mA current, which I connected straight onto connector terminals, no resistor, sketch below. This is as I'd seen others connecting theirs, so I simply did the same thing (no resistor) ... In your photo, + is marked on the left as shown, and it's the green wire in my photo.
Yes, that's the connector location - here's a photo of mine, for reference.
Regards LED I used a bog standard LED, rated at 2v forward voltage, 20mA current, which I connected straight onto connector terminals, no resistor, sketch below. This is as I'd seen others connecting theirs, so I simply did the same thing (no resistor) ... In your photo, + is marked on the left as shown, and it's the green wire in my photo.
As per my post - 2 volts nominal forward voltage, 20mA nominal forward current. I actually used this one from RS Components:
https://uk.rs-online.com/web/p/leds/2292425
I have no circuit details for the SMPS, so not sure what the actual voltage would be generated on the connector if an 'error' was to be present. Other builds I'd seen (including X's Warp 1 build, see page 1 of this thread) seem to have the LED installed with no resistor, so I presumed that voltage must be around 2 volts or so. I used the same LED's for the TPA board error outputs and they work just fine, but won't be able to check the operation of the one for the SMPS until an actual power supply 'error' occurs! So my LED choice for this was a bit of a calculated/educated guess I suppose!
https://uk.rs-online.com/web/p/leds/2292425
I have no circuit details for the SMPS, so not sure what the actual voltage would be generated on the connector if an 'error' was to be present. Other builds I'd seen (including X's Warp 1 build, see page 1 of this thread) seem to have the LED installed with no resistor, so I presumed that voltage must be around 2 volts or so. I used the same LED's for the TPA board error outputs and they work just fine, but won't be able to check the operation of the one for the SMPS until an actual power supply 'error' occurs! So my LED choice for this was a bit of a calculated/educated guess I suppose!
Hi Plott,
The connector is +ve to anode and add 1k5 resistor in series to limit current flow to LED. Any 3mm LED will work as it is an indicator. I think the signal is 5V nominally.
Here is how I wired it for Warp-1 and the schematics for the LED panel. Note that the two LEDs for the amp warnings do not need a resistor.
The connector is +ve to anode and add 1k5 resistor in series to limit current flow to LED. Any 3mm LED will work as it is an indicator. I think the signal is 5V nominally.
Here is how I wired it for Warp-1 and the schematics for the LED panel. Note that the two LEDs for the amp warnings do not need a resistor.
Hi Plott,
Bravo! Wow that sounds amazing!
Nice track - I’ll have to check it out myself.
Your OB is very well dialed in. Is the big woofer active and the mid and tweeter passive? The GRS planar is doing a great job and the Tang Band mid sounds so musical.
Love it. Way to go with the TPA3255.
Cheers,
X
Bravo! Wow that sounds amazing!
Nice track - I’ll have to check it out myself.
Your OB is very well dialed in. Is the big woofer active and the mid and tweeter passive? The GRS planar is doing a great job and the Tang Band mid sounds so musical.
Love it. Way to go with the TPA3255.
Cheers,
X
That time spent was worth it because you have yourself one of the best sounding speakers now. I know that if you go to a high end audio shop with a listening room. It will be very tough for them to have speaker or system that will outperform what you have built here. That’s a good feeling because it says spending $ isn’t everything in great sound.
Tell me more about your TT and all the amps and gear you have. It’s a beautiful sounding and good looking system.
Tell me more about your TT and all the amps and gear you have. It’s a beautiful sounding and good looking system.
Oh, many thanks X!
Yes, I have learned so much in this one year, of course through trial and error, but also through reading what feels like countless sources, dozens of simulations, prototypes, measurements. The feedback and help in my thread and in the whole forum were of course extremely valuable. I'm extremely satisfied, really. In November I attended the Vienna High End show eirh a friend and was extremely satisfied, even though the speakers weren't quite ready yet. Martin Logan was out of reach, and another magnetostat with a price tag of 80,000 really appealed to me (and my friend, he has Magnepans).
My system:
...I've never looked at my system like that before...
Yes, I have learned so much in this one year, of course through trial and error, but also through reading what feels like countless sources, dozens of simulations, prototypes, measurements. The feedback and help in my thread and in the whole forum were of course extremely valuable. I'm extremely satisfied, really. In November I attended the Vienna High End show eirh a friend and was extremely satisfied, even though the speakers weren't quite ready yet. Martin Logan was out of reach, and another magnetostat with a price tag of 80,000 really appealed to me (and my friend, he has Magnepans).
My system:
- Project RPM 9 Carbon TT
- Project Ground It Deluxe 2 base
- Project Evolution 9 Carbon arm
- Nagaoka MP-500 moving iron cartridge
- Benz ACE L moving coil cartridge
- Lehmann Black Cube RIAA preamp (currently not in setup anymore, I'm building the Pearl 3)
- Marantz SA-KI Ruby SACD player
- Project StreamBox RS streamer
- Iron Pumpkin preamp
- HyperSET preamp under construction
- XW-1 Class D power amp
- The Open Baffle speakers
- Furutech FT-SWS (R) NCF wall socket
- inakustik AC-3500P reference power station
- Acoustic Revive RR-777 Schumann generator
- Synergistic Research FEQ X4 field generator
- Synergistic Research ATM green
- Synergistic Research passive grounding block
- Synergistic Research Atmosphere Level 1 interconnects
- Audioquest Coffee digital interconnect
- Audioquest Blizzard main AC power cable
- Audioquest Thunder power cables
- Synergistic Research SR-30 power cable with purple tuning disc
- Synergistic Research Atmosphere Level 2 speaker cable
- Synergistic Research ECT
- Synergistic Research XOT
- Synergistic Research Orange Quantum fuses
- Audioquest Fog Lifters
- selfmade racks
- bamboo chopping board bases
...I've never looked at my system like that before...
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