Hi all
Now, both channels of my zen 4 is working and stable - but the amp still gets hot - this is most likely caused by to small heatsinks - my fault.
But - even though the play and sound good (cant hear the full potential yet, as im using a poor cd player, and partly faulty speakers)
Still - compared to the old Crown DC150, theres much, much more detail in the higher registers, akkustic guitars sound incredible, and theres more bass detail - transparent sound, very nice.
But - the snake in paradice - theres also noise, sounds like 50 hz buzz with higher pulses that varies in volume - about 2 pulses a sceond - they are easy heard between the songs on a CD.
Can this be because the amp is build up on a piece of MDF ? - lack of screening ?
Or, has it to do with me using 34 volt trafo instead of 36 ? - my regulated supply is close to 40 volts, 39,6 or so - this should be 42 according to Nelsons article. Drain of Q1 to ground is stable at 22 volts.
Any other suggestions to this noice ?
Also, when drived direct from a CD vith variable output with 2 volts maximum output, theres no sign of distortion, and I also feel that 30 watts should sound louder on my speakers - is this normal, or is there a problem with the amplifier gain somewhere ?
I measure 3,3 volts before C2 and ground, where the article shows 4 volts ?
Thank you very much !
Cheers !
Hans
Now, both channels of my zen 4 is working and stable - but the amp still gets hot - this is most likely caused by to small heatsinks - my fault.
But - even though the play and sound good (cant hear the full potential yet, as im using a poor cd player, and partly faulty speakers)
Still - compared to the old Crown DC150, theres much, much more detail in the higher registers, akkustic guitars sound incredible, and theres more bass detail - transparent sound, very nice.
But - the snake in paradice - theres also noise, sounds like 50 hz buzz with higher pulses that varies in volume - about 2 pulses a sceond - they are easy heard between the songs on a CD.
Can this be because the amp is build up on a piece of MDF ? - lack of screening ?
Or, has it to do with me using 34 volt trafo instead of 36 ? - my regulated supply is close to 40 volts, 39,6 or so - this should be 42 according to Nelsons article. Drain of Q1 to ground is stable at 22 volts.
Any other suggestions to this noice ?
Also, when drived direct from a CD vith variable output with 2 volts maximum output, theres no sign of distortion, and I also feel that 30 watts should sound louder on my speakers - is this normal, or is there a problem with the amplifier gain somewhere ?
I measure 3,3 volts before C2 and ground, where the article shows 4 volts ?
Thank you very much !
Cheers !
Hans
picture of the amp?
what about the noise with no source connected tor it? may the noise come from a preamp or so? power supply not far enough away from input connector, cable from PCB to input connectore long and unshielded? ground loop? you have to play around to detect from were the noise comes. I can´t see a problem with the voltages you measured. Also I can´t see a problem with the MDF, i use a wooden case.
what about the noise with no source connected tor it? may the noise come from a preamp or so? power supply not far enough away from input connector, cable from PCB to input connectore long and unshielded? ground loop? you have to play around to detect from were the noise comes. I can´t see a problem with the voltages you measured. Also I can´t see a problem with the MDF, i use a wooden case.
till said:
Im sorry, but I dont have a digital camera, so I can not poste a picture of the amp - but I can try to describe it: a MDF-board, about 40x40 centimeters (about 17") - heatsinks along two of the sides - amp boards in one side with input and output connecters gooing out there, and inn the other end two caps and a toroid. Diode bridges are mounted on same heatsink as the two non-audio FETS of the amp. Distance from input connecters to PSU is about 30 centimeters.
Without input cables connected, the pulsing "snerring" is gone, but it then sounds like listening to someones heart through a stetoscope - a "thump" sound about two times a sceond. sometimes spiced with something that resembles the squirl of a mouse - this squirl is also pulsing, but from silence to loud to silence and so forth.
The "snerring" is likely to be ground loop ?
What can the "heart-sound" be caused from ?
Hope that some of you can give me some advice - they are much needed !!!
Cheers !
Hans
Thumping
If you built the voltage regulator as it is listed the output should be 42v. The is the five 9.1 volt zeners minus the 4 volts across the transistor that is regulating.
You may not be feeding enough input voltage to make the regualtor work. Try disconnecting the string of zeners. This may solve this. The output will track the input voltage, just 4 volts or so down.
But from your description, it sounds like a low frequency occilation. Check the feedback loop. If something is wrong it could make the amp thump.
The fact that this only occurs when the input is connected also indicates something in the feedback.
Good luck!
George
If you built the voltage regulator as it is listed the output should be 42v. The is the five 9.1 volt zeners minus the 4 volts across the transistor that is regulating.
You may not be feeding enough input voltage to make the regualtor work. Try disconnecting the string of zeners. This may solve this. The output will track the input voltage, just 4 volts or so down.
But from your description, it sounds like a low frequency occilation. Check the feedback loop. If something is wrong it could make the amp thump.
The fact that this only occurs when the input is connected also indicates something in the feedback.
Good luck!
George
crown300 said:
Funny you should ask that - I have just been to a friends house and borrowed (actually bought) a pair of small two way dynamic speakers - instead of my Quad ESL 63, and now the low thumping is gone, some snerring is still there though.
I will try disconnecting the string of zeners (shorting start and end of the string ???) and se if that helps further. Should I get 42 volts, when I only have 48 volts unregulated ? the 2 volts less here is not the 2 volts missing on the regulated supply ?
The possible feedback problem - how can I solve this, other than check component value again, and resolder all joints ?
Thanx !!!
/Hans
till said:
This sounds troublesome.....perhaps I should talk to my parts supplyer ?? ;-)
Anyway, when I lift one of the zeners, I measure 47,5 volts (Same as unregulated DC voltage) across Gate and Drain of Q5, and 42,5 volts across the source. If I follow the drawing, this seems to be rigth ?
Buth now what - should I get some proper zeners, or can I leave them out now the voltage is correct anyway ?
And the "humming / buzzing" - with no signal cable connected to the amp, it is silent as the grave - even with my beat-up-musician ear regth in the tweeter can I hear anything, but when I connect the cables from a DAC or CD player, its there - what can my problem be ??
Thanx for helping me.
/Cheers !
Hans
in case the amp is quiet with no cable connected and makes noise with the cable connected it should be a problem with your ground. How did you connect the ground / shield of the cable? Read the article at passlabs about ground loops.
IMO it doesn´t matter if you have some volts more or less at the regulator. Just try to distribute the zehner in a way the voltage at right and left channel is about the same.
IMO it doesn´t matter if you have some volts more or less at the regulator. Just try to distribute the zehner in a way the voltage at right and left channel is about the same.
till said:
The amp is wired as it should ( I suppose) - I use two bridges (200V, 25 A), one pr. channal, and then a 47,000 uF pr. channal. Unregulated ground is connected to ground on the amp board, to where the RCA-phone's ground/sheild also is connected.
I have tried to make a cable from the balanced XLR from my DAC, where I use pin 2 and 3 (positive and negative) ending up as live and shield in a RCA phone jack - then there is much, much less noise - this is bad though, as my dac does not have a volume potmeter
I use the same powerstrip for the amp and CD player, as stated in the article - earth is virtually non exixting in older houses in denmark - we have a HPFI-relais that deals with power trouble - so earthing is also out of the question.
Is there really noting to do, but to live with the noise ?
I have removed the zener-string on both channals now, and read 42-43 volts on regulated supply (47 volts unregulated - 4 volts) - I suppose thats OK ?
Cheers !
Hans
I should not tell, i build some amps without real grounding, and there is not that much noise.
Without the zehners you have no a capacintance multiplyer, its also ok. But with the zehers and and a little less voltage than in Nelsons articles there is also no problem.
I´m afraid for help we need more information. Without some detailed pictures of the amp nobody else than you will find the source of hum.
Without the zehners you have no a capacintance multiplyer, its also ok. But with the zehers and and a little less voltage than in Nelsons articles there is also no problem.
I´m afraid for help we need more information. Without some detailed pictures of the amp nobody else than you will find the source of hum.
Problem solved !!!!
I feel so embaressed - but it was so simple after all...
Last nigth (0430) I was out having a few beers ( still to many
), and was discussing DIY with a engineering student from my university - "should I try to run both channels of one unregulated supply ??" - "That migth help..." he answerd - so home at around 0500 in the morning I got to work, and bugger me if it didnt work !!!
Im so happy ! - Thanx to everyone who has stuck up with my silly questions......especially Till - Vielen Dank !
Now I have to finish that BLS....so I guess Ill be back
/Cheers !
Hans
I feel so embaressed - but it was so simple after all...
Last nigth (0430) I was out having a few beers ( still to many
), and was discussing DIY with a engineering student from my university - "should I try to run both channels of one unregulated supply ??" - "That migth help..." he answerd - so home at around 0500 in the morning I got to work, and bugger me if it didnt work !!!Im so happy ! - Thanx to everyone who has stuck up with my silly questions......especially Till - Vielen Dank !
Now I have to finish that BLS....so I guess Ill be back
/Cheers !
Hans
I just observed that you have a perfectly silent amp with no input plugged in. I had the same on my Zen2. It has nothing to do with your grounding. I had the venerable Nelson Pass point out to me that with nothing on the input, the amp pulls the output low, so producing nearly no output (hence no noise). In this case the lack of noise is a red herring and should not be used when troubleshooting.
I had shielding problems with my torroidal transformer. Encasing it in copper with a tag to earth sorted that one out.
Regulation of the power supply is a nice touch, but you will probably notice no difference with just the cap multiplier, and the amp will run cooler.
Shoog
I had shielding problems with my torroidal transformer. Encasing it in copper with a tag to earth sorted that one out.
Regulation of the power supply is a nice touch, but you will probably notice no difference with just the cap multiplier, and the amp will run cooler.
Shoog
Balanced Zen4
Hi Brendon
No, I'm still searching for aluminium to cope with the double amount of heat for balanced operation. But, I belive that the cabeling it self should not be to difficult.
This is how I think it should be done:
1. tie both input gound together, and connect it to the shield in the xlr-connector.
2. Connect one of the channels positive RCA to negative in the XLR-connector(the "cold" one), and the other RCA-positive(signal) to the "hot" XLR-pin.
3. connect the two ground output connectors to each other with heavy duty cable, to avoid current flowing through the input cables(according to Nelsons article).
4. Drain the balanced output acros the two remaining output terminals (remember that this amp inverts the input signal).
I belive this is whats needed to run balanced, but I wont put my head on the block, if you know what I mean, cause ive not tried it yet......
BTW - your site about the SoZ got me into DIY in the first place!!
Happy building & keep DIY !!
Cheers !
Hans
Super_BQ said:
Hi Brendon
No, I'm still searching for aluminium to cope with the double amount of heat for balanced operation. But, I belive that the cabeling it self should not be to difficult.
This is how I think it should be done:
1. tie both input gound together, and connect it to the shield in the xlr-connector.
2. Connect one of the channels positive RCA to negative in the XLR-connector(the "cold" one), and the other RCA-positive(signal) to the "hot" XLR-pin.
3. connect the two ground output connectors to each other with heavy duty cable, to avoid current flowing through the input cables(according to Nelsons article).
4. Drain the balanced output acros the two remaining output terminals (remember that this amp inverts the input signal).
I belive this is whats needed to run balanced, but I wont put my head on the block, if you know what I mean, cause ive not tried it yet......
BTW - your site about the SoZ got me into DIY in the first place!!
Happy building & keep DIY !!
Cheers !
Hans
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