Danger Mouse you didn't say what your source is. I had a similar problem using a computer soundcard as source with Penasa's Rev C amps. Every other source worked fine no problem. So it seems like your common grounded source is the problem. If you can't fix the cause you can remedy the symptoms with an audio isolation transformer £3-ish on ebay. Inelegant but it works.
Problem is fixed. Was a ground Problem like assumed.
But wasnt really easy to get rid of it.
Test Setup:
No source->Cheap chinchcabel->Symasym->Speaker
no sourece because the ground Connection between the 2 cinch-inputs
via the cinchcable caused the Problem.
Driven only 1 side of the amp no HUMMM occures
I had tryed multiple different ways to ground the amp and 2 different PSUs.
Only 1 way works.
Amp was only dead silent when i used the PSU schematic from post 3939
and delete the 10OHM CL60 NTC`s and replace them with wire.
-Strange? at first i had a Center tapped Transformer PSU with one Bridge Rectifier (done this way to get lowest losses at the rectification) and star ground between caps,
both channels on this star Ground hardwired to earth-->HUMMMM
-with NTC to earth---->HUMMM
-no Connection to earth----HUMMM
-with PSU like in post 3939, Star Ground for each channel + NTC to same earth ---->HUMMM
-with Groundloop breaker instead of NTC --->HUMMM
-no conection to earth at all ---> massive HUMMM
-without NTC/groundloopbraker --->silence
dont know why it is like it is but iam happy now.
Silent the symasym is a really good amp.
Thanks for your help guys.
Problems with amps never die out so --->i will be back
But wasnt really easy to get rid of it.
Test Setup:
No source->Cheap chinchcabel->Symasym->Speaker
no sourece because the ground Connection between the 2 cinch-inputs
via the cinchcable caused the Problem.
Driven only 1 side of the amp no HUMMM occures
I had tryed multiple different ways to ground the amp and 2 different PSUs.
Only 1 way works.
Amp was only dead silent when i used the PSU schematic from post 3939
and delete the 10OHM CL60 NTC`s and replace them with wire.
-Strange? at first i had a Center tapped Transformer PSU with one Bridge Rectifier (done this way to get lowest losses at the rectification) and star ground between caps,
both channels on this star Ground hardwired to earth-->HUMMMM
-with NTC to earth---->HUMMM
-no Connection to earth----HUMMM
-with PSU like in post 3939, Star Ground for each channel + NTC to same earth ---->HUMMM
-with Groundloop breaker instead of NTC --->HUMMM
-no conection to earth at all ---> massive HUMMM
-without NTC/groundloopbraker --->silence
dont know why it is like it is but iam happy now.
Silent the symasym is a really good amp.
Thanks for your help guys.
Problems with amps never die out so --->i will be back
Attachments
Hi "gefährliche Maus",
I got similar problems with my Stereo SymAsm...Maybe it was already mentioned. But I don't understand what you finally modified on the org. schematic to get rid of the Humm.
I used the SymAsym PCB layout from Symasym - diy-audio-shop.de
The Recitifer PCB is from this shop too (+DC Blocking circuit at the mains). I have some Humming when I use one or both RCA Sockets.
The Topology of the System - (discrete branch after the dc-filter - 1x torodialtransformer, 1x recetifierPCB each channel):
Mains (ground connected to the case) ->DC-Filter (no ground)->TorodialTransformer(shieldwinding connected to case via starpoint with the second transfomer)->Recetiferboard(refernce groundpoint for ampstage - not connected to the second channel pcb)->SymAsym (ground connected to recetiferboard - not connected to the second channel)
This is the base configuration - Humm whatever I do with it. (Strange phenomena: If I switch off the system the Humm still remains as long the PSU Caps are full and it becomes louder) ...This effect reverses when I switch the polarity of the mainscable - Loud if it is on - lower if I turn it off and it runs on caps.
If I touch the shield conductor of both the RCA Plugs at once the Humm becomes lower - so I connected each RCAPlug to the case via 100k resistors -> better but still humming.
There is no change in Loudness (CDP on mute) of the Humm if I turn the amppoti - but on a certain point near full volume it vanishes nearly completely....
So I don't know where is the rub :S ...
Cabels are braided or twisted (remains since they have been not braided - no change due braiding). The torodials are audiotransformers with magentic shielding, shieldwinding etc..... and far away from the signalpath of the input RCA's..
It would be really glad if someone has an idea...(Impedance related?! 100K )
regards
Alex
I got similar problems with my Stereo SymAsm...Maybe it was already mentioned. But I don't understand what you finally modified on the org. schematic to get rid of the Humm.
I used the SymAsym PCB layout from Symasym - diy-audio-shop.de
The Recitifer PCB is from this shop too (+DC Blocking circuit at the mains). I have some Humming when I use one or both RCA Sockets.
The Topology of the System - (discrete branch after the dc-filter - 1x torodialtransformer, 1x recetifierPCB each channel):
Mains (ground connected to the case) ->DC-Filter (no ground)->TorodialTransformer(shieldwinding connected to case via starpoint with the second transfomer)->Recetiferboard(refernce groundpoint for ampstage - not connected to the second channel pcb)->SymAsym (ground connected to recetiferboard - not connected to the second channel)
This is the base configuration - Humm whatever I do with it. (Strange phenomena: If I switch off the system the Humm still remains as long the PSU Caps are full and it becomes louder
) ...This effect reverses when I switch the polarity of the mainscable - Loud if it is on - lower if I turn it off and it runs on caps. If I touch the shield conductor of both the RCA Plugs at once the Humm becomes lower - so I connected each RCAPlug to the case via 100k resistors -> better but still humming.
There is no change in Loudness (CDP on mute) of the Humm if I turn the amppoti - but on a certain point near full volume it vanishes nearly completely....
So I don't know where is the rub :S ...
Cabels are braided or twisted (remains since they have been not braided - no change due braiding). The torodials are audiotransformers with magentic shielding, shieldwinding etc..... and far away from the signalpath of the input RCA's..
It would be really glad if someone has an idea
...(Impedance related?! 100K ) regards
Alex
Thx for your suggestion's. Finally I got rid of the hum. After Andrew's advice I double checked both channels and tested every channel in full discrete "mono" mode. The hum equals in both channels. So errors on the pcb would have been in both devices. ...the solution was easier than I thought. I grounded the refground of both ampstages to the starground of the case. So now no hum anymore. Despite of the nice music you wont even recognize that it is switched on.
Hi, yes the hum was only slightly audible, but enough to get annoyed. Lets say there is no big preamp - I'm using an old 100k log Alps Stereo Poti as passive preamp. But I will try a newer Alps 10k log as shunt pot Volume Control so the impedance should be arround 20k ... maybe I will hear no big difference but the adjustement of the volume should be easier in the more quite range.
Hi all,
...just thought I could share my SYMASYM pcb lay-out, SYMASYM was an old project I was wishing to build. The design was N0T TESTED yet (need to buy more time for my audio hobby) Anyone interested to get their hands on it, pdf files attached. Schematic used was M. Bittner's original but I suggest to follow Pavel Macuras mod if using 2SC5200/SA1943 for the outputs.
Regards!
...just thought I could share my SYMASYM pcb lay-out, SYMASYM was an old project I was wishing to build. The design was N0T TESTED yet (need to buy more time for my audio hobby
) Anyone interested to get their hands on it, pdf files attached. Schematic used was M. Bittner's original but I suggest to follow Pavel Macuras mod if using 2SC5200/SA1943 for the outputs.Regards!
Attachments
I had very good results with a Pass B1 Clone.
Could be imagination but i think it makes the Sound more round/ complete.
Only with Pot i found the sound a little bit to sharp/ harsh.
Maybe this is also a Option for you
Hi all,
...just thought I could share my SYMASYM pcb lay-out, SYMASYM was an old project I was wishing to build. The design was N0T TESTED yet (need to buy more time for my audio hobby
Regards!
Very neat but quite a radical departure from Michael's layout. I note that Michael said at the outset that layout was critical so interested to know if you've built and measured performance yet?
A couple of observations in the meantime: as you're paying attention to Pavel's suggestions did you not want to put parallel reversed diodes around R2?
Are your MJE15030/1's too far away from their pads? Their legs aren't very long. So if you're mounting, for instance, on 3mm angle aluminium you need to allow for this, plus the board thickness plus half the thickness of the transistor itself in order to have enough of the leg poking thru to solder.
R1 and R3 don't need to be more than 0.5w according to post 3142. I've sourced Welwyn 1 watt MPF1's for these which at 6.3mm long are much smaller than you have. You could lose several mm on each side of your board. Even the 2w MPF2's are only 10mm.
Is there a compelling reason for making a bipolar cap out of 2 electrolytics at C1? I know the WIMAs are impossible to get at 4.7uF outside of Germany but why not use a single reversed electrolytic as Micheal suggests at post 2279 and 2438. Or are we doing this just because that's what Carlos did with Blame?
Did you not want to use 2SK170 at Q1/2?
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hello there i have seen a diy circuit of 150watt using TIP142AND TIP147 AND A DRIVER OF TIP41,.is that circuit is realy stable and have good performance if yes than please reply, or any other circuit that diy team suggest me to construct which is of good sound quality with good punch low frequency and treble,any good and stable circuit wattage upto 150 watts RMS,thanks if yes than please reply me on email: usualfellow@yahoo.co.in ,thanks
In the past we used to hunt down personal data like emails and addresses openly posted although it was not based on some forum rule. Just to remind and rectify carelessness. Still such things continually pop up. We will not be hunting them anymore in this vast forum unless reported by the original poster as mishaps using the red triangle button. Grown-ups own risk. Regards, moderation. 
Hi, i have finished build Symasym 5.3, output DC-offset is 0.0~0.1mv, tested running 2 hours Vbe is steady +/- 0.002V. running in high volume heatsink still cool (i'm using a thin heatsink with cooling fan.) no pop sound when switch on and off, no humming or noise. this circuit is realy stable (Great!!! is a good Design).
ok, sound output is clean and good ...... but i'm expect overtone and more liveliness or dynamic.
Don't know my amp is oscillating or not (any idea how to check it?) highly appreciate any help.
my sym ... bd139 as Vbe multiplier, mje15030/15031 as driver, NJW0281-0302 as output, 3.3pf feedback cap (too samll ?), and winma mk4 Type capacitor as input cap.
ok, sound output is clean and good ...... but i'm expect overtone and more liveliness or dynamic.
Don't know my amp is oscillating or not (any idea how to check it?) highly appreciate any help.
my sym ... bd139 as Vbe multiplier, mje15030/15031 as driver, NJW0281-0302 as output, 3.3pf feedback cap (too samll ?), and winma mk4 Type capacitor as input cap.