Take a metal square/rectangle - 2 or 3mm thickness - and place it below the AMP board.
Through all 4 holes, with metal screws make a good contact between the board and the metal plane.
Then, make a good contact between the ground - from the main AC plug - and the metal plane, with a metal screw.
Through all 4 holes, with metal screws make a good contact between the board and the metal plane.
Then, make a good contact between the ground - from the main AC plug - and the metal plane, with a metal screw.
Thanks.
Unfortunately it didn't solve the problem.
If RCA input shorted, there is no buzz anymore
With preamp connected it buzz immediately, even if the preamp is powered off.
If ONE channel input is shorted and the other connected to the preamp, no buzz.
Maybe a ground loop issue
The preamp has no connection to earth.
My suggestion. Leave the amp connected like you had in post#322. Just connect the MW power supply +/-ve to the sure amp, do not connect the AC safety gnd to the amp. I use 2 Sure amps and connect them like this and there is no buzz. I also have them line sourced from a non-grounded floating source like you describe.
If you had an EMI/RFI problem then maybe a ground plane under the amp might help. It's very unlikely you have this issue. Your amp seems to be quiet when you short the inputs.
It does appear you have a leakage current between the signal and power paths.
- test#1 : connect your preamp line outs, and unplug the power to the preamp, to see if you have buzz
- test#2 : plug the preamp plug (2-prong) in the "other" position ( rotate 180deg) to swap the line-neutral to the preamp to see if you still get buzz. The 3 prong ac safety gnd is "closest" to neutral, sometimes line and neutral get reversed in 2 prong systems. It does not effect functionality at all, but sometimes the internal power supply return is inadvertently capacitively coupled to one of those ac lines.
- test#3 : try disconnecting the MW AC safety ground (make sure it doesn't touch anything). Both unit's output power supplies will "float" and will reference their inputs to the common signal ground.
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Third suggestion is the first one i would try - I forget it in my previous post.
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Thanks a lot guys 
Buzz almost gone with power supply AC earth disconnected.
Now buzz is low but still there, it may be because of the layout and lack of shielding. Hope it will be totally gone in a proper enclosure.
105dB horn and 99dB 15" driver doesn't help I suppose.
There is a slight hiss even input shorted but low enough to not be a concern.
This small board seems to be very powerful and sound quite "natural" from low to high.
I don't have much experience with class D amps, are they generally reliable? ie. if they don't fail during the first hours, they last long?
Before lifting ac safety ground, I've tried with input transformers between preamp and sure board, it didn't cure the noise (but buzz became like a hum) but powering from another wall plug lowered the buzz significantly.
Buzz almost gone with power supply AC earth disconnected.
Now buzz is low but still there, it may be because of the layout and lack of shielding. Hope it will be totally gone in a proper enclosure.
105dB horn and 99dB 15" driver doesn't help I suppose.
There is a slight hiss even input shorted but low enough to not be a concern.
This small board seems to be very powerful
and sound quite "natural" from low to high.I don't have much experience with class D amps, are they generally reliable? ie. if they don't fail during the first hours, they last long?
Before lifting ac safety ground, I've tried with input transformers between preamp and sure board, it didn't cure the noise (but buzz became like a hum) but powering from another wall plug lowered the buzz significantly.
I've tried a pair of Sowter 8920 without success, it upsets the board
Pink & white connected to Vout1
Violet & yellow connected to GND
As soon as the board is powered on, the red led stays on and the external speaker protection module (DC and time delay) trigger.
For testing purpose, if I disconnect the ground (violet & yellow), the board starts.
Sowter Type 8920
Hi,
I bought AA-AB32313 few months ago, when i read many positive opinion. Before i was using TPA3116 Nobsound amp and I was really impressed sound quality. I made some modification (OSCON, input caps, set lower gain of TPA3116, stubs) and sound is verrry good. Connected to my Dynaudio Foccus or even Audience 42, sound is clean , with good fast bass, treble are clean, no harsh. Giving a lot fun.
I wanted more power so I bought this module Sure. First, I connected to same power supply 19V what was used before with TPA. Sound is very bright, no lowest bass, high midrange screaming. I put Black Gate N 4.7uF caps on input - the same. With batteries 12,24 or 36 Volts -the same. As source im using Maverick DAC (tube out giving more fluently sound then solid out) also w/o KSL M7 preamp. Still TPA is much better. I dont think that new module is broken. Sound even in high level is without distortion, but far away from TPA.
Any idea?
I bought AA-AB32313 few months ago, when i read many positive opinion. Before i was using TPA3116 Nobsound amp and I was really impressed sound quality. I made some modification (OSCON, input caps, set lower gain of TPA3116, stubs) and sound is verrry good. Connected to my Dynaudio Foccus or even Audience 42, sound is clean , with good fast bass, treble are clean, no harsh. Giving a lot fun.
I wanted more power so I bought this module Sure. First, I connected to same power supply 19V what was used before with TPA. Sound is very bright, no lowest bass, high midrange screaming. I put Black Gate N 4.7uF caps on input - the same. With batteries 12,24 or 36 Volts -the same. As source im using Maverick DAC (tube out giving more fluently sound then solid out) also w/o KSL M7 preamp. Still TPA is much better. I dont think that new module is broken. Sound even in high level is without distortion, but far away from TPA.
Any idea?
I've tried a pair of Sowter 8920 without success, it upsets the board
Pink & white connected to Vout1
Violet & yellow connected to GND
As soon as the board is powered on, the red led stays on and the external speaker protection module (DC and time delay) trigger.
Did you switch the DIP-switches? SW1 has to be off.
If you've got very high efficient speakers, no amp will be absolutely silent (unless it got a noise gate). The hum and maybe also noise might come from your power supply. What kind of PS are you using? A SMPS by chance?
Thank you for reply,
Loudspeakers are rather low efficient. Dynaudio Foccus have 86dB, Audience maybe 85dB.
With TPA3116 amp is almost silent, after reduction gain amplifier (two resistors set gain of TPA3116) You need put ear very close tweeter to hear something... With Sure module, I hear noise from 1meter...
As supply, I used batteries 12V, 24V, 36V and 19V laptop brick. I have also linear transformer supply 15V/30A . (Nota bene- last one working excellent with TPA). All of them giving the same noise level, hum and character of sound (bright, without bottom end, screaming high midrange. Tube sound? Absolutely not). I bought also SMPS600RS 48V 600W but i can test this one in 2 months, not earlier...
I'm using this board without enclosure, like was take off from box. Just installed to caps for input signal.
Best regards
Loudspeakers are rather low efficient. Dynaudio Foccus have 86dB, Audience maybe 85dB.
With TPA3116 amp is almost silent, after reduction gain amplifier (two resistors set gain of TPA3116) You need put ear very close tweeter to hear something... With Sure module, I hear noise from 1meter...
As supply, I used batteries 12V, 24V, 36V and 19V laptop brick. I have also linear transformer supply 15V/30A . (Nota bene- last one working excellent with TPA). All of them giving the same noise level, hum and character of sound (bright, without bottom end, screaming high midrange. Tube sound? Absolutely not). I bought also SMPS600RS 48V 600W but i can test this one in 2 months, not earlier...
I'm using this board without enclosure, like was take off from box. Just installed to caps for input signal.
Best regards
Did you a) replace the input caps on the board or b) add caps to the inputs external to the board. If you added external caps, then you have lowered the input capacitance (2 caps in series now) and have increased the HP filter XO point which may be why you have no bass.
Your board noise issue is a problem from what you've described. I don't see this on other model Sure amps that I use.
I installed caps (electrolytic 4,7uF/50V) directly to Vin and Vout socket, instead optional potentiometer board. In AB32313 module, ceramic capacitors are not in series, for sure. Signal passing by new caps only, or (if dip switch is ON position) by ceramic and additional new caps(parallel connection).
I reviewed THD+N vs FREQ charts on Sure website, for different amplifiers, and very often is visible peak on 1,0145kHz. Sometimes level of peak is very high, depend from model of amp. What is the reason this peak? For 1kHz our ears are very sensitive. I cant hear 1kHz hum in my model, I have rather around 400Hz. If somebody hear any hum (not noise) in yours amp?
I see datasheet for TC2001, that gain can be changed by Rf and Ri resistor, connected to internal opamp. I'll try recognize what resistors are on AB32313.
I reviewed THD+N vs FREQ charts on Sure website, for different amplifiers, and very often is visible peak on 1,0145kHz. Sometimes level of peak is very high, depend from model of amp. What is the reason this peak? For 1kHz our ears are very sensitive. I cant hear 1kHz hum in my model, I have rather around 400Hz. If somebody hear any hum (not noise) in yours amp?
Do You mean, problem exist because I'm running without enclosure?
I see datasheet for TC2001, that gain can be changed by Rf and Ri resistor, connected to internal opamp. I'll try recognize what resistors are on AB32313.
For the purpose of debugging, can you remove these additional caps and put both (2) switches in the "on" position. It's easier to isolation the problem with no modifications.
That test is only used to show how low the noise floor is because the inputs are shorted. The amps I use (1x200w, 2x200w) are quiet. Have you measured the speaker output?
The amp should be quiet without an enclosure. I use a wood enclosure that holds an +36VDC SMPS and 2 Sure amps and their volume controls. My amp volume controls are always at max.
Before modifying the board. You said earlier that you have output noise even with the inputs shorted to gnd. Did you try this without your additional caps (ie. stock form).? There is always the possibility the amp actually has a problem.
Attachments
One picture is worth more than 1000 words
I marked gray line signal path from RCA connector up to TC2001 chip. Signal feed across resistor R8 (33k), RV2 (???) and diode D2 (smd code 5A6, look like Zener diode 5V6)- all connected parallel. Later in series by capacitor C2 and by DIP Switch (if ON) , to resistor 10k (in blue rectangular). From resistor, on input internal opamp. Resistor15k(in green rectangular) is feedback resistor for opamp.
If dip switch is OFF and we have installed caps between Vin and Vout sockets, then signal passing only by additional caps.
Resistor marked in red, 8,2k is reference resistor. According to datasheet, should be 8,25k 1%. I don't know, how critical is this element.
I bought my board directly from PartsExpress. Full symbol is: AA-AB32313V100. Maybe these good sounding boards have different revision
I marked gray line signal path from RCA connector up to TC2001 chip. Signal feed across resistor R8 (33k), RV2 (???) and diode D2 (smd code 5A6, look like Zener diode 5V6)- all connected parallel. Later in series by capacitor C2 and by DIP Switch (if ON) , to resistor 10k (in blue rectangular). From resistor, on input internal opamp. Resistor15k(in green rectangular) is feedback resistor for opamp.
If dip switch is OFF and we have installed caps between Vin and Vout sockets, then signal passing only by additional caps.
Resistor marked in red, 8,2k is reference resistor. According to datasheet, should be 8,25k 1%. I don't know, how critical is this element.
I bought my board directly from PartsExpress. Full symbol is: AA-AB32313V100. Maybe these good sounding boards have different revision
Attachments
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Hello All,
Just received my ab32313. I figured i was going to put the power switch at the AC mains, but now i noticed the "shutdown control connector". What is this for exactly and how does this work? Can i put a switch between these two connector pins instead of at the AC mains?
thanks in advance for your comments/help!
Just received my ab32313. I figured i was going to put the power switch at the AC mains, but now i noticed the "shutdown control connector". What is this for exactly and how does this work? Can i put a switch between these two connector pins instead of at the AC mains?
thanks in advance for your comments/help!
I ordered the AB32313 but received AB23251V120 Are they the same thing?
I note that on the original German "Gremlin" thread that people ordered AB32512 but received AB32313 instead.
I ordered my board from Sure on the evening of 17th May and recieved it on the morning of the 21st may pretty good all the way from China.
Like MirC I was running a TPA3116 from a 19v laptop supply, I connected up the Sure board using the same power supply. Unlike MirC I was amazed at the improvement in sound quality.
The sure board is not ideal for my speakers which are 8ohm Proac response 2.5 but it controlled them better than any other amp I have tried!
An interesting thing I discovered...I connected the pre out from my AV amp into the Sure board and ran the auto calibration routine, the set up halted and indicated that my main speakers were out of phase?
I checked all connections on the Sure board but all were correct, I reversed the speaker wires and ran the auto cal again, this time all was well...has anyone else come across this out of phase speaker issue or are the amps supposed to be out of phase at the outputs?
I note that on the original German "Gremlin" thread that people ordered AB32512 but received AB32313 instead.
I ordered my board from Sure on the evening of 17th May and recieved it on the morning of the 21st may pretty good all the way from China.
Like MirC I was running a TPA3116 from a 19v laptop supply, I connected up the Sure board using the same power supply. Unlike MirC I was amazed at the improvement in sound quality.
The sure board is not ideal for my speakers which are 8ohm Proac response 2.5 but it controlled them better than any other amp I have tried!
An interesting thing I discovered...I connected the pre out from my AV amp into the Sure board and ran the auto calibration routine, the set up halted and indicated that my main speakers were out of phase?
I checked all connections on the Sure board but all were correct, I reversed the speaker wires and ran the auto cal again, this time all was well...has anyone else come across this out of phase speaker issue or are the amps supposed to be out of phase at the outputs?