Royber, OPC/Owen has a whole new set of boards coming out soon, see this thread post #685
http://www.diyaudio.com/forums/vend...ts-available-here-bal-bal-se-se-lpuhp-69.html
http://www.diyaudio.com/forums/vend...ts-available-here-bal-bal-se-se-lpuhp-69.html
I had time this evening to finish testing the amps on the bench.
One thing I didn't notice until I had it all hooked up in the lounge to the speakers. When I connect my AVR to the signal input directly adjacent the DPS600 that is circled in the attached pic I get a lot of mains hum through all channels. When I disconnect that channel only then everything is nice and quiet. I think it's safe to assume that this is radiated noise from the mains routed on the back of the DPS600 board that is very close to this signal input. Now I've got to have a bit of a think about what's the easiest way to solve that issue. Taking it apart to drill another hole and relocate that connector will be a bit of a pain at this stage (in the short amount of time I've had tonight it sounds pretty good even with the annoying humm and I am keen to sit back and listen for a while!) but might be the best answer. Any thoughts/suggestions?
Chris
One thing I didn't notice until I had it all hooked up in the lounge to the speakers. When I connect my AVR to the signal input directly adjacent the DPS600 that is circled in the attached pic I get a lot of mains hum through all channels. When I disconnect that channel only then everything is nice and quiet. I think it's safe to assume that this is radiated noise from the mains routed on the back of the DPS600 board that is very close to this signal input. Now I've got to have a bit of a think about what's the easiest way to solve that issue. Taking it apart to drill another hole and relocate that connector will be a bit of a pain at this stage (in the short amount of time I've had tonight it sounds pretty good even with the annoying humm and I am keen to sit back and listen for a while!) but might be the best answer. Any thoughts/suggestions?
Chris
Attachments
I can't be sure what I am seeing in the pic.
What colours of the twisted pairs do what function?
Is PE mechanically connected to Chassis?
Can you get some green/yellow for the PE to Chassis connection, or sleeve the green with a green/yellow sleeve. Any electrician will have rolls of the sleeving and rolls of various size of PE wiring.
What colours of the twisted pairs do what function?
Is PE mechanically connected to Chassis?
Can you get some green/yellow for the PE to Chassis connection, or sleeve the green with a green/yellow sleeve. Any electrician will have rolls of the sleeving and rolls of various size of PE wiring.
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Like Andrew, I find it a bit tough to really see what's going on there.
Your problem though sounds a lot more like a ground loop problem than a coupled noise problem. If you were picking up the magnetic field from the mains, it would only appear on that one channel. If plugging and unplugging that one channel causes noise on all channels, then there's a grounding problem.
Check your connections and connectors carefully. Is that one connector different from the others somehow? Is the shield or one of the two wires connected to the chassis on that connector and not the others?
If it's not anything in the amp itself, the next place to look is in the AVR. Does that output have a different arrangement than the others? Is part of the output connector shorted to the chassis when it shouldn't be?
If just one of the connections is making everything go bonkers, I would start with looking for differences there.
Cheers,
Owen
No.
Do not break the Safety Ground/Earth. It is a "PERMANENT" mechanical connection for a reason. To protect the user/operator.
Instead break the Signal Return to Power Ground connection and insert the standard resistor (in parallel with the inverse parallel diode) that is fitted to many amp PCB as standard.
Andrew,
I agree that the safety ground is required permanently, however, with an inexpensive adaptor plug, Chris could diagnose the cause of the hum and plan a proper, permanent solution, such as you ssuggest. Perhaps suitable AC adaptor plugs aren't available in Australia.
Regardless, your admonition of caution is appropriate.
Regards,
Neel
I agree that the safety ground is required permanently, however, with an inexpensive adaptor plug, Chris could diagnose the cause of the hum and plan a proper, permanent solution, such as you ssuggest. Perhaps suitable AC adaptor plugs aren't available in Australia.
Regardless, your admonition of caution is appropriate.
Regards,
Neel
Yeah it is hard to get a good photo that gets everything in focus in that amp.
Inputs:
Blue/white pair is SE signal to LME49830 amps
white-gray/white-brown is SE signal to LPUHP
The input connectors are all isolated Neutrik BNC (NBB75DSIB).
Outputs:
red/white is speaker signal from LME49830 amps
purple/orange speaker signal from LPUHP
Output connectors are 4pole Neutrik Speakon.
There is an orange/white pair just floating there. I haven't connected it up. It will be connected to LME49830 amps output to disconnect power if the amp goes DC.
The orange/green/brown small twisted triplet to each LME49830 is the LME amp 65V supply. The red/green/black is the 55V supply.
Most of the mains wiring is obscured by the Schaffner mains filter. I know I should be putting green/yellow sleeve on the PE wiring, but didn't have any handy. The safety earth bolt is also in there and secured with double nut then safety earth labeled connection on each of the SMPS is connected to the same bolt after that. PE connection isn't getting lifted.
The AVR is a Denon 3808. All RCA output gnd are connected to mains earth.
I'm using a nanoAVR as crossover and allocating channels to use the AVR as a pre-amp for 3-way active speakers plus subwoofer until I build up a miniSHARC + 8ch DAC to use for the speaker DSP.
One curious thing though.
If I connect the right-high freq preout to the left input (the one that is giving me dramas) I get total silence on the left output. A quiet(er) hum on either LPUHP ouptut when the LPUHP input is left disconnected. This DC coupled directly to a 108dB/2.83V compression driver (DE250) remember.
I'm thinking that means something is up with the AVR output? I have a RCA-BNC converter for the cables that are BNC both end (BJC LC-1 cable). Later I will try checking that something isn't up with the RCA-BNC converter.
It is a bit of a mission to get to the back of the AVR. Anyway I'll try that once I can reclaim the TV room without complaints from my wife "I'm watching that you know" even though she's clearly looking at ipad and just listening to the TV .... I could be watching recording I made of F1 practice earlier and playing with my amp
.
If that RCA-BNC converter isn't to blame then I'm thinking I might just leave the AVR alone and avoid using that output. I'm using 7ch of the 8 outputs, I might try the spare one and see if that gives a better outcome. Hopefully I'll be back to say I've spent some time listening to music later tomorrow!! (tomorrow is only 1hr away here).
Thanks,
Chris
Inputs:
Blue/white pair is SE signal to LME49830 amps
white-gray/white-brown is SE signal to LPUHP
The input connectors are all isolated Neutrik BNC (NBB75DSIB).
Outputs:
red/white is speaker signal from LME49830 amps
purple/orange speaker signal from LPUHP
Output connectors are 4pole Neutrik Speakon.
There is an orange/white pair just floating there. I haven't connected it up. It will be connected to LME49830 amps output to disconnect power if the amp goes DC.
The orange/green/brown small twisted triplet to each LME49830 is the LME amp 65V supply. The red/green/black is the 55V supply.
Most of the mains wiring is obscured by the Schaffner mains filter. I know I should be putting green/yellow sleeve on the PE wiring, but didn't have any handy. The safety earth bolt is also in there and secured with double nut then safety earth labeled connection on each of the SMPS is connected to the same bolt after that. PE connection isn't getting lifted.
The AVR is a Denon 3808. All RCA output gnd are connected to mains earth.
I'm using a nanoAVR as crossover and allocating channels to use the AVR as a pre-amp for 3-way active speakers plus subwoofer until I build up a miniSHARC + 8ch DAC to use for the speaker DSP.
One curious thing though.
If I connect the right-high freq preout to the left input (the one that is giving me dramas) I get total silence on the left output. A quiet(er) hum on either LPUHP ouptut when the LPUHP input is left disconnected. This DC coupled directly to a 108dB/2.83V compression driver (DE250) remember.
I'm thinking that means something is up with the AVR output? I have a RCA-BNC converter for the cables that are BNC both end (BJC LC-1 cable). Later I will try checking that something isn't up with the RCA-BNC converter.
It is a bit of a mission to get to the back of the AVR. Anyway I'll try that once I can reclaim the TV room without complaints from my wife "I'm watching that you know" even though she's clearly looking at ipad and just listening to the TV .... I could be watching recording I made of F1 practice earlier and playing with my amp
.If that RCA-BNC converter isn't to blame then I'm thinking I might just leave the AVR alone and avoid using that output. I'm using 7ch of the 8 outputs, I might try the spare one and see if that gives a better outcome. Hopefully I'll be back to say I've spent some time listening to music later tomorrow!! (tomorrow is only 1hr away here).
Thanks,
Chris
WHY ?
the RCA is a two pole connector. It carries signal to/from source/receiver.
The signal NEEDS a two wire connection. Those two wires are Signal Flow and Signal Return.
Those two wires of the two wire signal connection should be a twisted pair from Source through the connector to the Receiver.
NEITHER of the signal wires go to Mains earth !!!!!!!!!!!
I know that, thats how I have wired my amp, the sentence that you quoted is the behavior I have observed of the Denon 3808 AVR by checking for continuity between signal gnd at the AVR output and mains earth. I measured 1.x ohms resistance from memory.
Chris
The ground loop went away when I swapped the interconnect for that channel.
Is a bit odd though because with a multimeter everything looks the same between these two cables. But I'll worry about that more later ... I've found that I've got an oscillation somewhere. I'm not sure which channel yet as the woosh-woosh sounds only started after 20mins or so and came through on both speakers. Back to the bench for the amp to work out what parts need replacing/resoldering. I've probably got 'spares' for everything except the LPUHP v1 PCBs. I'll try to diagnose where the oscillation is and if I've got any questions / observations I'll be back here or the LPUHP thread.
EDIT: I did hook the amp up to a scope before I took it out to hook up to the speakers and didnt notice anything going on when I ran some sine waves into an ~8R load. Was only a short duration test so I'll look closer now.
Chris
Is a bit odd though because with a multimeter everything looks the same between these two cables. But I'll worry about that more later ... I've found that I've got an oscillation somewhere. I'm not sure which channel yet as the woosh-woosh sounds only started after 20mins or so and came through on both speakers. Back to the bench for the amp to work out what parts need replacing/resoldering. I've probably got 'spares' for everything except the LPUHP v1 PCBs. I'll try to diagnose where the oscillation is and if I've got any questions / observations I'll be back here or the LPUHP thread.
EDIT: I did hook the amp up to a scope before I took it out to hook up to the speakers and didnt notice anything going on when I ran some sine waves into an ~8R load. Was only a short duration test so I'll look closer now.
Chris
Hi,
Need some advise here. I'm running the LME with separate psu and the grounding is connected by the zero ohm resistor beneath the heatsink. (I'm still having a little noise when a source is connected. Tried a lot of differend groundings etc. Looks like small 100 Hz spikes on scope on output coming from the PSU) Should I remove the resistor (and isolate the heatsink with some tape) and connect the ground wire on the LME side on the PCB? Somebody experienced differences in setup?
During powering off, there appears to be an oscillation with no speakers connected. Connected it's not there. There is a zobel.
I rewired the amp so the PSU wires are all twisted.
Need some advise here. I'm running the LME with separate psu and the grounding is connected by the zero ohm resistor beneath the heatsink. (I'm still having a little noise when a source is connected. Tried a lot of differend groundings etc. Looks like small 100 Hz spikes on scope on output coming from the PSU) Should I remove the resistor (and isolate the heatsink with some tape) and connect the ground wire on the LME side on the PCB? Somebody experienced differences in setup?
During powering off, there appears to be an oscillation with no speakers connected. Connected it's not there. There is a zobel.
I rewired the amp so the PSU wires are all twisted.
Attachments
FYI, LME49830 has been discontinued by TI along with many others. I suggest to get some spares for the long haul.
LME49830TB/NOPB Texas Instruments | Mouser
I finally put mine together. I used a old Pioneer SX-1050 transformer, power supply in a old Sansui G-7500 receiver. I get power meters finally!! The Pioneer Sx-1050 was a 120W/ch rated receiver. I have to kick the woman out of the house to blast this amp to its clipping. Still need to hook up to the 15" woofers and compare to the old Pioneer SX-950.
Made a hand wired speaker protection ckt using the old Hitachi HA12002 chip.
So I have +/-62V unregulated to the MOSFETs and +/- 60V regulated
I did a fair bit of testing and listening. The setup is dead quiet, with inputs shorted to ground. I am having a bit of hum issues when I hook up the G-7500 pre-amp section. I have to place my ear to the speakers to hear it, but it is their. The g-7500 pre-amp is stock so it might be old ecaps, bjts, need to investigate. Even the old Pioneer PS is stock so lots of thing to try out.
If I use an external tuner/pre-amp it is almost as quiet as the inputs shorted. I am running 150mA of MOSFET bias as the distortion numbers did not improve with more bias. It is still is fair bit of heat.
I could not get the THD measurement numbers as to what OPC got, still trying to figure out why.
When I ran a CD source through the amp, it sounds nice and is really powerful. I still am using the original filter caps from the G-7500, being 10mF. I plan on upgrading to 22mF when I re-cap everything else.
I did one mod to the wire-amp pcb, I added a 330pf cap across the input pull down resistor, IIRC that it is 5.49K which is unusually low. So that is the 220 input R with a 330pF to ground. You can calc the -3dB point I guess OPC used a low value input R, to get the noise floor down as low as possible. For all I know it is overloading the G-7500 pre-amp and it has a 1.2K output R, which is a setup that needs to be changed as it is an attenuator where you do not want one.
Since the G-7500 chassis had the speaker ground returns already going to the common point at the big ecaps, I left it that way. I ran two separate grounds from the wire-amp pcb to the common point ground for each channel. I installed the 0 ohm resistor as instructed. I did not try to remove it and see what happens.
I put a zobel on the speakers using 47nF and a 10 ohm R.
I bought a used HP 3325A so I can test the rise/fall times, I got around 600ns rise/fall times which is pretty decent and freq response I got out to around 560KHz -3dB. No ringing or overshoot on the 10KHz square wave that I used to measure rise/fall times.
isolate the LME49830 from ground. It has to because the heatsink is at ground potential.
Run two ground wires from the wire-amp to the common point ground.
What Sony transformer is that, from what model so I can look it up. What is the MOSFET rail voltages and the LME volatge, are they the same or do you have a boosted supply to the LME, which is the better way to do it.
Rick
LME49830TB/NOPB Texas Instruments | Mouser
I finally put mine together. I used a old Pioneer SX-1050 transformer, power supply in a old Sansui G-7500 receiver. I get power meters finally!! The Pioneer Sx-1050 was a 120W/ch rated receiver. I have to kick the woman out of the house to blast this amp to its clipping. Still need to hook up to the 15" woofers and compare to the old Pioneer SX-950.
Made a hand wired speaker protection ckt using the old Hitachi HA12002 chip.
So I have +/-62V unregulated to the MOSFETs and +/- 60V regulated
I did a fair bit of testing and listening. The setup is dead quiet, with inputs shorted to ground. I am having a bit of hum issues when I hook up the G-7500 pre-amp section. I have to place my ear to the speakers to hear it, but it is their. The g-7500 pre-amp is stock so it might be old ecaps, bjts, need to investigate. Even the old Pioneer PS is stock so lots of thing to try out.
If I use an external tuner/pre-amp it is almost as quiet as the inputs shorted. I am running 150mA of MOSFET bias as the distortion numbers did not improve with more bias. It is still is fair bit of heat.
I could not get the THD measurement numbers as to what OPC got, still trying to figure out why.
When I ran a CD source through the amp, it sounds nice and is really powerful. I still am using the original filter caps from the G-7500, being 10mF. I plan on upgrading to 22mF when I re-cap everything else.
I did one mod to the wire-amp pcb, I added a 330pf cap across the input pull down resistor, IIRC that it is 5.49K which is unusually low. So that is the 220 input R with a 330pF to ground. You can calc the -3dB point
I guess OPC used a low value input R, to get the noise floor down as low as possible. For all I know it is overloading the G-7500 pre-amp and it has a 1.2K output R, which is a setup that needs to be changed as it is an attenuator where you do not want one.Since the G-7500 chassis had the speaker ground returns already going to the common point at the big ecaps, I left it that way. I ran two separate grounds from the wire-amp pcb to the common point ground for each channel. I installed the 0 ohm resistor as instructed. I did not try to remove it and see what happens.
I put a zobel on the speakers using 47nF and a 10 ohm R.
I bought a used HP 3325A so I can test the rise/fall times, I got around 600ns rise/fall times which is pretty decent and freq response I got out to around 560KHz -3dB. No ringing or overshoot on the 10KHz square wave that I used to measure rise/fall times.
Leave the 0 ohm R in place but
isolate the LME49830 from ground. It has to because the heatsink is at ground potential.
Run two ground wires from the wire-amp to the common point ground.
What Sony transformer is that, from what model so I can look it up. What is the MOSFET rail voltages and the LME volatge, are they the same or do you have a boosted supply to the LME, which is the better way to do it.
Rick
Attachments
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Wimshurst :
I just noticed that you twisted the ground return in with the MOSFET +/- supply. I did not do it that way, I twisted the +/- together only and ran the 2 ground returns back separately to the common point. I did not use the speaker ground on the wire-amp either as OPC recommended in his notes.
I just noticed that you twisted the ground return in with the MOSFET +/- supply. I did not do it that way, I twisted the +/- together only and ran the 2 ground returns back separately to the common point. I did not use the speaker ground on the wire-amp either as OPC recommended in his notes.
Ok, I will order some extra spare LME49830 from Conrad soon. Weird TI stopped making these. The transformer is from a old 'blown' Sony 3200f amp. This amp used already two extra 5 Volt AC windings for higher DC on the front end. So I made a voltagedoubler and then used the same ripple filter as Sony did in their amp. (Google the Sony schematic) Very clean DC on the scope, always 10 Volt above mosfet voltage. Bias is 360 mA.
I put 180 pF on top of the input resistor on the amp PCB. Softstart, Zobel, Vellemans kit speaker protection with the relay rewired according to Elliott Sound.
I have no problem with the tiny hum when a source is connected (ear in speaker)
I'm very satisfied as it is now. Great amp!
I put 180 pF on top of the input resistor on the amp PCB. Softstart, Zobel, Vellemans kit speaker protection with the relay rewired according to Elliott Sound.
I have no problem with the tiny hum when a source is connected (ear in speaker)
I'm very satisfied as it is now. Great amp!