Hi Protos,
I will try some reference zeners (6,2V) wich can be bought with very low temperature coefficients. Like LM329 or1N825A @ 0,002%/°C. A normal zener has 0,04 to 0,08 %/°C
Resistors (1%) generally have a quite low temperature coefficient. I bought some 390 Ohms 0,1% with TK25 ppm so these won´t be the problem.
William
I will try some reference zeners (6,2V) wich can be bought with very low temperature coefficients. Like LM329 or1N825A @ 0,002%/°C. A normal zener has 0,04 to 0,08 %/°C
Resistors (1%) generally have a quite low temperature coefficient. I bought some 390 Ohms 0,1% with TK25 ppm so these won´t be the problem.
William
I tried running the amps with single ended input.However with the neg input tied to ground the feedback network from the output starts messing up the relative offset values which start to track the absolute offset values.This means that at start up you can get quite a few volts of rel dc on the output plus it is drifting all over the place.
I can´t think how you can run them single ended without a rel offset problem.
I can´t think how you can run them single ended without a rel offset problem.
Well I did that but it did not seem to work.But I realize now that I did it wrongly.Because I have only balanced chassis connectors I was using se-bal adaptors which short the neg to ground at the input on the case..I put the cap between the connectors neg input at the case to the neg input on the board which I realize now is useless.I should have put it on the ground connector.Just goes to show what silly things one can come up with early in the morning without putting the brain into gear.
Shhh - don´t mention this to anybody - my credibility will be shot to pieces
Shhh - don´t mention this to anybody - my credibility will be shot to pieces
Hi
I know there has been a group buy some time back and I am wondering if there are any people who have dropped out of the project and would be willing to consider selling their boards ?
I am am looking for 4 boards, preferably of the the latest version that was made.
Please e-mail me via the group or privately at hugot@icon.co.za
Thanks
Jozua
Cape Town
South Africa
I know there has been a group buy some time back and I am wondering if there are any people who have dropped out of the project and would be willing to consider selling their boards ?
I am am looking for 4 boards, preferably of the the latest version that was made.
Please e-mail me via the group or privately at hugot@icon.co.za
Thanks
Jozua
Cape Town
South Africa
Folks, I have a question please..
I am building a 'universal power supply' with a very large transformer to run a couple of Aleph X mono blocks as well as some more small Pass type amps. These amp chassis' are separate from the psu and will use an umbilical cord. My intention is to use a 3 wire cord containing +, gnd, and -.
My question: Does anyone have a problem with the seperate amp chassis' not being at earth, but at audio ground? There will ne no mains in or near them...
Would it be better to avoid earth in the amps also to reduce possible gnd loops?
Thanks,
Marc
I am building a 'universal power supply' with a very large transformer to run a couple of Aleph X mono blocks as well as some more small Pass type amps. These amp chassis' are separate from the psu and will use an umbilical cord. My intention is to use a 3 wire cord containing +, gnd, and -.
My question: Does anyone have a problem with the seperate amp chassis' not being at earth, but at audio ground? There will ne no mains in or near them...
Would it be better to avoid earth in the amps also to reduce possible gnd loops?
Thanks,
Marc
mpmarino said:
Well having the chassis at earth ground is better for isolating noise for the Audio circuits. Keep the "Audio" ground off the chassis or on is a matter of ground loops. If it was an all in one chassis it would take extroadinary measures to keep them seperate in most applications. I find it difficult just to implement the Thermistor or bridge between the chassis and ground as the IEC Power filters I use ground as soon as you screw them to the chassis.
If one of your HV DC leads comes loose and touches the chassis it might be just as dangerous as an AC lead. If the Chassis is grounded at least it would trip a breaker.
Regards
Anthony
hello everyone,
It's been awhile since I posted, hope all is well with the gang.
I have a situation which leads to a question: The original AX schematic asks for 15 volts +-. Is this 15 volt requirement the voltage necessary before the amp is switched on? I've been under the impression (probably incorrect at that) that the measured input voltage while the amp is on is the voltage that my ps is capable of delivering, when in fact the ps voltage is much higher when it's unloaded. I lowered the value of several resistors on my prototype amp as a result of this assumption. If I remember correctly, the power transformer is 500 V/A-16volts x 2. I'm running an LC filter (choke is iron core-10mH 10amp). 14.4v is probably what I sent to the pcb. In my amateurish innocence, I remember measuring the input to the board when running. Seems to me the voltage was quite a bit lower than 14.4v (11.5v perhaps). To compound matters, I ran two channels from this source. This means the amp must have been sucking the ps dry. Yikes! Oh well, I didn't die, and the amp is affordable. I'll mend it and my ways. I have two trannies with a 17 volt output x 2 @ 500V/A each. I'll give the two board their own power supply.
Any input will be appreciated.
John Inlow
It's been awhile since I posted, hope all is well with the gang.
I have a situation which leads to a question: The original AX schematic asks for 15 volts +-. Is this 15 volt requirement the voltage necessary before the amp is switched on? I've been under the impression (probably incorrect at that) that the measured input voltage while the amp is on is the voltage that my ps is capable of delivering, when in fact the ps voltage is much higher when it's unloaded. I lowered the value of several resistors on my prototype amp as a result of this assumption. If I remember correctly, the power transformer is 500 V/A-16volts x 2. I'm running an LC filter (choke is iron core-10mH 10amp). 14.4v is probably what I sent to the pcb. In my amateurish innocence, I remember measuring the input to the board when running. Seems to me the voltage was quite a bit lower than 14.4v (11.5v perhaps). To compound matters, I ran two channels from this source. This means the amp must have been sucking the ps dry. Yikes! Oh well, I didn't die, and the amp is affordable. I'll mend it and my ways. I have two trannies with a 17 volt output x 2 @ 500V/A each. I'll give the two board their own power supply.
Any input will be appreciated.
John Inlow
The amp will run on less than +-15V. If you want to run it that way all the time, you might consider adjusting the resistor that biases the Zener for the front end current source. Distortion will be somewhat higher due to the way MOSFETs behave at lower voltages, but nothing you can't live with.
Grey
Grey