I was hoping I could use the only spare base panel for mounting as they will be out of sight and not seen also hoped given the 500's are quiet and lots placed closely together I could get away with it. A fair challenge they are jammed together
Later today I'll temporarily relocate the speaker out, remove the pot, (I was hoping to mount a small pre-amp unit as well, without adding another box but that's for another day, I want it to be quiet first)
I'll remeasure and re listen with the relocated connections
Later today I'll temporarily relocate the speaker out, remove the pot, (I was hoping to mount a small pre-amp unit as well, without adding another box but that's for another day, I want it to be quiet first)
I'll remeasure and re listen with the relocated connections
So it is a subwoofer amp. A subwoofer amp with 3-prong plug is just asking for hum. And you got 2 of them, also your main amp might be also grounded.
Is 3-prong plug the original configuration? If not, I would suggest reversing back to 2 prong plug.
Yes a 1KW sub amp, 2 of them for two 18" subs
In the UK you have an earth pin for safety GND on the majority of items, Ideally this just attaches to the case but if I do this it hums. It's only certain items that don't need a safety earth (double insulated)
The major hum is when the case only is earthed
In the UK you have an earth pin for safety GND on the majority of items, Ideally this just attaches to the case but if I do this it hums. It's only certain items that don't need a safety earth (double insulated)
The major hum is when the case only is earthed
Today I removed all connections to the pot (there was only GND connected) and re route the speaker out, alas it made no difference. The only minor difference I could measure after placing copper shielding in various place as the fact that a lid on top (folded alloy, just resting and not actually making contact as edged have sticky backed felt to avoid resonance and not screwed in place) was consistently better. I'll make up some transformer cables to see if moving the transformer further away helps at all
This is measuring noise with the amp just on and all connected but nothing playing
Green lid on, red lid off, magenta is the BNPSP500 which is quiet
you need to establish a baseline noise level with no inputs
wire up as per post 62, all metalwork/chassis must be grounded to mains earth, and also psu 0V to chassis
ensure the mains input is away from the amp circuitry
just connect a speaker to monitor noise, but no inputs
wire up as per post 62, all metalwork/chassis must be grounded to mains earth, and also psu 0V to chassis
ensure the mains input is away from the amp circuitry
just connect a speaker to monitor noise, but no inputs
Ctrix, hi
I do have a number off base lines and have listened to all as well as measured. Last night with some guidance from Bonsai I went back to basics and removed all connections so now have :
Chassis to GND at one point, the small point that connects the earth cable to the chassis (top connection) and just a 0.01uf connecting signal GND to chassis with a new drilled hole and sanded chassis crimp etc so this is next to the signal GND input (small blue ceramic cap)
Alas very noisy when connected to the DSP, the plots are taken from the amp speaker output
Measuring with inputs from the DSP all on the REW graph shows the latest configuration green, yesterday Blue and the BPSP500 amplifier that is silent
Removing the inputs I have listened to to and measured with no input, shorting plus etc, the results are the same - the BK1K is still not silent
The only diiference to the page 62 directions are that I am not connecting the the steel chassis at the centre
I do have a number off base lines and have listened to all as well as measured. Last night with some guidance from Bonsai I went back to basics and removed all connections so now have :
Chassis to GND at one point, the small point that connects the earth cable to the chassis (top connection) and just a 0.01uf connecting signal GND to chassis with a new drilled hole and sanded chassis crimp etc so this is next to the signal GND input (small blue ceramic cap)
Alas very noisy when connected to the DSP, the plots are taken from the amp speaker output
Measuring with inputs from the DSP all on the REW graph shows the latest configuration green, yesterday Blue and the BPSP500 amplifier that is silent
Removing the inputs I have listened to to and measured with no input, shorting plus etc, the results are the same - the BK1K is still not silent
The only diiference to the page 62 directions are that I am not connecting the the steel chassis at the centre
If I Short the input with a shorting plug and take measurements I have the following base
1. Green todays configuration
2. Blue yesterdays configuration
3. Purple the BPSP 500 connected to the DSP
3. Buff the A>D with no input so clearly some issues with the cheap device
Audibly 1 and 2 sound similar (I cant A-B without 20 minutes soldering) and measure similar, noise - buzz and low pitch hiss at the seating position not loud but not acceptable, like a cheap PA system with sensitive speakers might sound. 3. Totally silent unless you are 6" away and even then you need to be still.
Looks like it's between 200-1.5KHz as the speaker has good output here but falls away over 1KHz, it is an 18" FS 25Hz driver !
1. Green todays configuration
2. Blue yesterdays configuration
3. Purple the BPSP 500 connected to the DSP
3. Buff the A>D with no input so clearly some issues with the cheap device
Audibly 1 and 2 sound similar (I cant A-B without 20 minutes soldering) and measure similar, noise - buzz and low pitch hiss at the seating position not loud but not acceptable, like a cheap PA system with sensitive speakers might sound. 3. Totally silent unless you are 6" away and even then you need to be still.
Looks like it's between 200-1.5KHz as the speaker has good output here but falls away over 1KHz, it is an 18" FS 25Hz driver !
The difference is the no GND lift and an additional RCA RFI cap. I have tried relocating a number of of items like the speaker out, the pot is no longer connected to anything, I will try moving the transformer a distance away but more soldering and leads to make up.
I was thinking earlier about the transformer. As you say, move it away or try a DC bench power supply bypassing the the transformer.
Like I said in previous post I've had a several amps of the same make- model (C Audio RA series) that buzzed and I put that down to a layout design fault. I reduced the buzzing slightly by rotating the transformer and the buzz also reduced when I took the top lid off. I even reduced the mains voltage via a Variac and that also reduced the buzzing.
Like I said in previous post I've had a several amps of the same make- model (C Audio RA series) that buzzed and I put that down to a layout design fault. I reduced the buzzing slightly by rotating the transformer and the buzz also reduced when I took the top lid off. I even reduced the mains voltage via a Variac and that also reduced the buzzing.
I've made up some lead extensions the transformer will be 12" away tomorrow for testing, Ive not given up yet !
Okay the transformer a distance away moved around it makes no difference, measurements identical or very, very close (not sure if that's good or bad news)
I fitted the lower sensitivity resistors to take the input down from 5000mv to 775mv (A spec option) I also added a different band capacitor, my other amp the 500 BPSP is specced at 3Hz to 1KHz unfiltered so I added a 22nf to the band pass, so somewhere around 1.5K
The results show some improvement on the output before. Pink the BPSP 500 benchmark, silent. The latest revision blue and the previous amp at 775 mv sensitivity. This is quieter but still too noisy for me to be comfortable using the amplifier. I will also try the amp panel on a wood board to see what the chassis might be doing.
I am also going to try some pre amplifiers in series as I don't want to drive this from the DSP in any case. All these are with the safety Earth connected to the chassis. The 0.01uf Ceramic cap to the chassis and no pot
Regarding connections the chassis is not connected to the signal BUT ofcourse it will be when the signal from the DSP is connected. I am exploring some anomalies with noise when other amps are turned on.
The results show some improvement on the output before. Pink the BPSP 500 benchmark, silent. The latest revision blue and the previous amp at 775 mv sensitivity. This is quieter but still too noisy for me to be comfortable using the amplifier. I will also try the amp panel on a wood board to see what the chassis might be doing.
I am also going to try some pre amplifiers in series as I don't want to drive this from the DSP in any case. All these are with the safety Earth connected to the chassis. The 0.01uf Ceramic cap to the chassis and no pot
Regarding connections the chassis is not connected to the signal BUT ofcourse it will be when the signal from the DSP is connected. I am exploring some anomalies with noise when other amps are turned on.
The big peak at 50 Hz is radiated noise most likely due to your measurement set up. Everything above 100 Hz is most likely to be common impedance coupling and or earth loops.
Since you removed the wire from the input connector to the chassis, any internal ground loop is now gone (good). You moved the transformer away from the chassis and it did not change the noise substantially. So for the time being, it’s clear you don’t have problems in these areas.
The next thing to check is how the amplifier 0V and by implication the signal 0 V are connected to the 0V junction of the two reservoir capacitors - let’s call this the ‘power 0 V’.
There must no multiple direct connections to the power 0 V. The system 0V must ‘T’ off the power 0 V and all other 0 V connections made to this ‘T’ in this order from the power 0 V: chassis earth, then speaker, then any ancillary circuit 0 V, then the amplifier 0 V.
Since you removed the wire from the input connector to the chassis, any internal ground loop is now gone (good). You moved the transformer away from the chassis and it did not change the noise substantially. So for the time being, it’s clear you don’t have problems in these areas.
The next thing to check is how the amplifier 0V and by implication the signal 0 V are connected to the 0V junction of the two reservoir capacitors - let’s call this the ‘power 0 V’.
There must no multiple direct connections to the power 0 V. The system 0V must ‘T’ off the power 0 V and all other 0 V connections made to this ‘T’ in this order from the power 0 V: chassis earth, then speaker, then any ancillary circuit 0 V, then the amplifier 0 V.
The first slide depicts how a common impedance problem arises. I've shown this as a PSU + amplifier module, but the same rules apply for a design that has everything on the same PCB i.e. amplifier and PSU. The second slide shows how the signal and power grounds should be 'Teed' off the power 0V and all connections then made to upright of the T (shown upside down here). By way of an example, a 100uV common impedance problem arising across C-D from a 10A capacitor charging current pulse flowing through 10 microohms will limit the mains hum peaks to no better than -80 dBV, and 10 micro-ohms is conservative - the trace and wiring resistances involved are usually much higher.
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Here's the original board ( I replaced a damaged cap hence the missing cap) and the current modified version
Pink 0v from transformer
Light blue speaker out
Yellow spare 0v cable
Orange signal in (I will be using a pre-amps to connect here so DSP>Pre> this connection)
Do I need to move any as they I dont think necessarily matching (the 0v from then transformer toward the top ?) and perhaps a hum bucking restore on the signal in?
Pink 0v from transformer
Light blue speaker out
Yellow spare 0v cable
Orange signal in (I will be using a pre-amps to connect here so DSP>Pre> this connection)
Do I need to move any as they I dont think necessarily matching (the 0v from then transformer toward the top ?) and perhaps a hum bucking restore on the signal in?
Ctrix, hi
Well I did, yes, I am learning here and taking advice. Are you suggesting that the unattached 'yellow' lead above should go to the centre of the metal chassis as opposed to directly to the bonding point by the incoming earth chassis connection ? The criptic post 77 ?
Well I did, yes, I am learning here and taking advice. Are you suggesting that the unattached 'yellow' lead above should go to the centre of the metal chassis as opposed to directly to the bonding point by the incoming earth chassis connection ? The criptic post 77 ?