Hi XRK,
I'm responding to this last post by Plott, regards his 'beep'!
You may recall that I mentioned I experienced a considerable 'hum' when I first powered up my amp using (quality) RCA cables - see my post #283. At the time, I thought that may have been due to the somewhat haphazard way I'd connected these cables to the amp ..... Since then I've been using quality XLR cables and the amp is dead quiet.
However, upon seeing Plott's post I thought I'd try the RCA's again out of curiosity, this time being very careful to run the cables via my usual, tried and tested, route. And, would you believe it, I have exactly the same hum again - same volume and same frequency - as I had before when I first powered up! So it was nothing to do with the way I'd run the cables at the time.
Hence, it would indeed appear that there is something 'going on' here - I'm beginning to suspect the RCA input side of the BTSB board? As mentioned, using XLR cables it's dead silent .... interesting that Plott seems to have a problem with RCA as well, and with different preamps at that ....
Recap - Macbook Air, USB connection to RME ADI-2 FS dac, Audioquest RCA cables from DAC to TPA3255, Van Damme cables to speakers ..... This same setup has been used with several different amps (chipamps, Class AB, Class D ....) over the last 6 or 7 years and I've NEVER had this problem before! This amp is wired and connected correctly as far as I know (see my post #278).
So I've tried a few experiments:
I had hoped the last experiment might have produced a result, but no joy. To me (?) connecting the two chassis together should have removed any potential ground loop issue? In any event, all devices are plugged into the same mains conditioner block. The only thing I couldn't try is unplugging the DAC (needs power supply to work!) .....
I don't have an iPhone DAC available in order to try that, but on the basis that this RME DAC has successfully been in operation with other amps for ages, I fail to see how this could suddenly now be causing this problem?
Would appreciate your thoughts and any advice as to where to go from here. Any other spurious DIP switch settings, other than you've already pointed out, that may need to be adjusted? Do the same 3-way connectors from BTSB to amp board remain as they are for RCA and XLR alike (just checking!)?
I'm personally not so worried about this for my use because I'm using XLR anyway - but if I ever wish to 'pass on' my amp at some point in the future then that might be difficult if I can't guarantee it would work with both XLR and/or RCA!
Many thanks, look forward to your reply,
Richard
I'm responding to this last post by Plott, regards his 'beep'!
You may recall that I mentioned I experienced a considerable 'hum' when I first powered up my amp using (quality) RCA cables - see my post #283. At the time, I thought that may have been due to the somewhat haphazard way I'd connected these cables to the amp ..... Since then I've been using quality XLR cables and the amp is dead quiet.
However, upon seeing Plott's post I thought I'd try the RCA's again out of curiosity, this time being very careful to run the cables via my usual, tried and tested, route. And, would you believe it, I have exactly the same hum again - same volume and same frequency - as I had before when I first powered up! So it was nothing to do with the way I'd run the cables at the time.
Hence, it would indeed appear that there is something 'going on' here - I'm beginning to suspect the RCA input side of the BTSB board? As mentioned, using XLR cables it's dead silent .... interesting that Plott seems to have a problem with RCA as well, and with different preamps at that ....
Recap - Macbook Air, USB connection to RME ADI-2 FS dac, Audioquest RCA cables from DAC to TPA3255, Van Damme cables to speakers ..... This same setup has been used with several different amps (chipamps, Class AB, Class D ....) over the last 6 or 7 years and I've NEVER had this problem before! This amp is wired and connected correctly as far as I know (see my post #278).
So I've tried a few experiments:
- Turned DAC volume down to 0 - no change
- Unplugged PSU from laptop (so, running on battery only) - no change
- Unplugged USB from DAC - no change
- Unplugged RCA cables from DAC - MUCH worse hum (as fully expected, as then no input to TP3255)
- Ran a separate earth connection between RME DAC chassis and TP3255 chassis - no change
I had hoped the last experiment might have produced a result, but no joy. To me (?) connecting the two chassis together should have removed any potential ground loop issue? In any event, all devices are plugged into the same mains conditioner block. The only thing I couldn't try is unplugging the DAC (needs power supply to work!) .....
I don't have an iPhone DAC available in order to try that, but on the basis that this RME DAC has successfully been in operation with other amps for ages, I fail to see how this could suddenly now be causing this problem?
Would appreciate your thoughts and any advice as to where to go from here. Any other spurious DIP switch settings, other than you've already pointed out, that may need to be adjusted? Do the same 3-way connectors from BTSB to amp board remain as they are for RCA and XLR alike (just checking!)?
I'm personally not so worried about this for my use because I'm using XLR anyway - but if I ever wish to 'pass on' my amp at some point in the future then that might be difficult if I can't guarantee it would work with both XLR and/or RCA!
Many thanks, look forward to your reply,
Richard
Hi XRK,
Thanks for responding back so promptly!
I turned amp off in between different 'experiments' and then turned back on again to see/hear the result. So I guess I would have unplugged both RCA's ....
In the meantime I've reinstated back to my 'normal' XLR set up now, but could try the RCA's again if you think that bit of info might be useful to you? It's a bit fiddly (for me!) but no problem if it would help, as it would be good to get to the bottom of it?
When I had them disconnected (at the DAC end), I inadvertently momentarily touched the end of one plug and the resultant noise was REALLY loud! I suspect that's to be expected?
Thanks for responding back so promptly!
I turned amp off in between different 'experiments' and then turned back on again to see/hear the result. So I guess I would have unplugged both RCA's ....
In the meantime I've reinstated back to my 'normal' XLR set up now, but could try the RCA's again if you think that bit of info might be useful to you? It's a bit fiddly (for me!) but no problem if it would help, as it would be good to get to the bottom of it?
When I had them disconnected (at the DAC end), I inadvertently momentarily touched the end of one plug and the resultant noise was REALLY loud! I suspect that's to be expected?
OK - just checked:
FYI, my amp's on a shelf in a small cupboard (long story!) so I've pulled it around and to the front edge of the shelf so I could reach the BTSB inputs on the rear. DAC's on top of cupboard and I have the RCA cables straight from the DAC, dangling over the front of the cupboard and straight into the amp. In other words, absolutely nowhere near any 'interference' from mains or otherwise ...
- Both RCA cables connected - hum present
- One cable unplugged - hum increased, hard to tell but I'd say almost doubled in volume. No difference for which channel unplugged or which end (DAC or amp) unplugged, result the same
- Both cables unplugged - about same hum level as when just one unplugged (maybe a fraction louder, hard to tell). Again no difference for which channel unplugged or which end unplugged, result the same
FYI, my amp's on a shelf in a small cupboard (long story!) so I've pulled it around and to the front edge of the shelf so I could reach the BTSB inputs on the rear. DAC's on top of cupboard and I have the RCA cables straight from the DAC, dangling over the front of the cupboard and straight into the amp. In other words, absolutely nowhere near any 'interference' from mains or otherwise ...
Hi X,
I made the check with an Astell&Kern high-res player with 3,5 mm/RCA - and no beep.
RCA from my preamp - beep.
RCA from my streamer preamp (Project Stream Box RS) - beep.
XLR no matter from where - no beep.
RCA from preamp or streamer into every other power amp - no beep.
(Further: absolutely no hum or beep without cable on the input, altough the amp "should" make hum that way, as you wrote.)
I write beep, because it's not a classic hum. It's a higher frequency continous beep, it must be about 500-600 Hz.
Funny.
Weird
(Further 2: it sounds so gorgeous... really)
I made the check with an Astell&Kern high-res player with 3,5 mm/RCA - and no beep.
RCA from my preamp - beep.
RCA from my streamer preamp (Project Stream Box RS) - beep.
XLR no matter from where - no beep.
RCA from preamp or streamer into every other power amp - no beep.
(Further: absolutely no hum or beep without cable on the input, altough the amp "should" make hum that way, as you wrote.)
I write beep, because it's not a classic hum. It's a higher frequency continous beep, it must be about 500-600 Hz.
Funny.
Weird
(Further 2: it sounds so gorgeous... really)
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Hi Richbandit, I'm curious what it is.
Luckily, no problem with xlr - it's gorgeous!
A thought - could this earth connection be creating a ground loop problem somehow? I connected it because others seemed to have done so, but I note that not everybody has ... Can't easily try unplugging it and see what happens at the moment, without extricating the enclosure out of the cupboard space it's in in order to remove the top cover - a task I'd like to avoid for now, until I have to!!
In the meantime I checked further things.
I use a Synergistic Research passive grounding block, where all my equipment is grounded.
For the connection of the grounding I take an unused in- or output, therefore it's a signal ground.
In the XV-1 I wanted to have a dedicated groundig RCA - but for whatever reason I didn't used the signal ground, but a groundig point of the smps... so connecting the ground connector to the grounding block causes the beep - because it's a totally different "ground".
Disconnecting it from the amp eliminates the beep but a slight hum comes instead. Therefore I will make the now missing internal grounding of the buffer board to the chassis and hope it eliminates the hum. Remark: with XLR there is absolutely nothing.
Will report tomorrow.
Sorry for the confusion X!
And a question: where can I find a signal ground in the amp? F.e. a middle contact of the signal wiring from the buffer to the amp board? Because I want to have a grounding connector.
I use a Synergistic Research passive grounding block, where all my equipment is grounded.
For the connection of the grounding I take an unused in- or output, therefore it's a signal ground.
In the XV-1
I wanted to have a dedicated groundig RCA - but for whatever reason I didn't used the signal ground, but a groundig point of the smps... so connecting the ground connector to the grounding block causes the beep - because it's a totally different "ground".Disconnecting it from the amp eliminates the beep
but a slight hum comes instead. Therefore I will make the now missing internal grounding of the buffer board to the chassis and hope it eliminates the hum. Remark: with XLR there is absolutely nothing.Will report tomorrow.
Sorry for the confusion X!
And a question: where can I find a signal ground in the amp? F.e. a middle contact of the signal wiring from the buffer to the amp board? Because I want to have a grounding connector.
Interesting Plott ......
But, on the other hand I do have the buffer board ground connection fitted, which goes to a 'star' point on chassis, which in turn is connected to both ground on amp board and incoming mains earth. Amp mains cable is 3-wire (live, neutral, earth) connected to same power block as DAC PSU ....
Plott - I'm not sure I fully understand, could you please explain again - where on the amp had you connected your incoming 'ground' connection, that you've now disconnected? Thanks
But, on the other hand I do have the buffer board ground connection fitted, which goes to a 'star' point on chassis, which in turn is connected to both ground on amp board and incoming mains earth. Amp mains cable is 3-wire (live, neutral, earth) connected to same power block as DAC PSU ....
Plott - I'm not sure I fully understand, could you please explain again - where on the amp had you connected your incoming 'ground' connection, that you've now disconnected? Thanks
It's not an incoming ground. I have the AC connector with phase, null and safety earth. The psu "makes" a ground for the rails.
And there is a signal ground from the rca/xlr input. I wanted a dedicated signal ground in order to connect the amp to the SR grounding block. But unfortunately I took the ground from the psu and not from a signal ground point, so I mismatched the grounds. When I now disconnect the amp from the grounding block (from the now common signal ground of the other equipment), the beep is gone.
And there is a signal ground from the rca/xlr input. I wanted a dedicated signal ground in order to connect the amp to the SR grounding block. But unfortunately I took the ground from the psu and not from a signal ground point, so I mismatched the grounds. When I now disconnect the amp from the grounding block (from the now common signal ground of the other equipment), the beep is gone.
Really interesting stuff guys.
With the new amp board with external 15v from the SMPS 15v regulator and a new buffer board, I find that the amp does not make a horrendous buzz with no input connected and speakers connected. Very strange. Maybe this has something to do with the external 15v PSU for the ancillary voltages in the amp?
Regarding the RCA noise/buzz. With RCA inputs and my ear within 1in of speaker woofer zone, I can barely hear a buzz (60Hz) but almost inaudible. With XLR no sound at all.
Next, I disconnected the Buffer board ground (the dual pin JST between the XLRs) and the mild hum from RCA from iPhone dongle is now silent. It is still silent with XLRs as well. So it seems that there may have been a change to the grounding topology with the 15v coming from the external PSU in the SMPS. But using RCA from my DAC (which also has XLR) has the slight hum still. I suspect this is a ground loop from the RCA to the DAC. Connecting the buffer ground at this point does reduce the hum a tad (for DAC based RCA).
So my recommendation is this:
1. Do not connect the ground on the BTSB panel mount to the star ground point. Leave it disconnected if you have an isolated source like a DAP, phone, battery powered laptop etc. I can confirm that the buffer has no ground loops in this mode.
Note: the XLR shield is grounded to the chassis via a vampire connection on the XLR when it is screwed in. It bites into the chassis. Otherwise it needs no chassis ground.
2. Make sure you have a good ground wire from a screw holding the SMPS to the star ground. The plate for the SMPS is black anodized to not a good conductor.
3. Connect protective ground of TPA3255 amp to earth star ground.
4. Make sure the insulating silicone pad for the TPA3254 heat sink is good so there is no connection from chassis to the thermal pad of the chip.
5. Where is analog signal ground located? The best place to get it on the TPA3255 board is the middle pin of the two balanced input jacks at X101 and X111 (pin 2).
On Buffer board if you are not using the single ended outputs, pin 1 on J6 and J7 are the signal analog grounds. Also pin 2 of the balanced out of J4 and J5.
Of course, if you use XLR input none of this is an issue. I’ll continue to research this but I know the Warp-1 in the first batch had RCA’s that were silent.
Hope this helps for now.
Thanks for working. With me.
With the new amp board with external 15v from the SMPS 15v regulator and a new buffer board, I find that the amp does not make a horrendous buzz with no input connected and speakers connected. Very strange. Maybe this has something to do with the external 15v PSU for the ancillary voltages in the amp?
Regarding the RCA noise/buzz. With RCA inputs and my ear within 1in of speaker woofer zone, I can barely hear a buzz (60Hz) but almost inaudible. With XLR no sound at all.
Next, I disconnected the Buffer board ground (the dual pin JST between the XLRs) and the mild hum from RCA from iPhone dongle is now silent. It is still silent with XLRs as well. So it seems that there may have been a change to the grounding topology with the 15v coming from the external PSU in the SMPS. But using RCA from my DAC (which also has XLR) has the slight hum still. I suspect this is a ground loop from the RCA to the DAC. Connecting the buffer ground at this point does reduce the hum a tad (for DAC based RCA).
So my recommendation is this:
1. Do not connect the ground on the BTSB panel mount to the star ground point. Leave it disconnected if you have an isolated source like a DAP, phone, battery powered laptop etc. I can confirm that the buffer has no ground loops in this mode.
Note: the XLR shield is grounded to the chassis via a vampire connection on the XLR when it is screwed in. It bites into the chassis. Otherwise it needs no chassis ground.
2. Make sure you have a good ground wire from a screw holding the SMPS to the star ground. The plate for the SMPS is black anodized to not a good conductor.
3. Connect protective ground of TPA3255 amp to earth star ground.
4. Make sure the insulating silicone pad for the TPA3254 heat sink is good so there is no connection from chassis to the thermal pad of the chip.
5. Where is analog signal ground located? The best place to get it on the TPA3255 board is the middle pin of the two balanced input jacks at X101 and X111 (pin 2).
On Buffer board if you are not using the single ended outputs, pin 1 on J6 and J7 are the signal analog grounds. Also pin 2 of the balanced out of J4 and J5.
Of course, if you use XLR input none of this is an issue. I’ll continue to research this but I know the Warp-1 in the first batch had RCA’s that were silent.
Hope this helps for now.
Thanks for working. With me.