tomchaoda said:
[referring to installing all of the little jumper wires]
I had exactly the same problem with my Aleph-X when I put it together three weeks ago (boards from HifiZen). It turns out I had forgotten to attach the jumper wire that connects the zener voltage reference to the negative rail (or ground, your choice). This may turn out not to be the problem, but, more than likely, the problem is somewhere in your front-end current source.
I am not sure what you mean by the relative offset. However, whether you mean the DC on the speaker outputs, or the offset of both of the speaker outs from the circuit ground, the difficulty trimming may be in your choice of resistors for the front-end current source (R24 and R26). Your power supply voltage is substantially higher than in the +/-15V version.
Jeremy
Problem solved!
I found out my problem! The VR2, I was turning all the way down to 0 ohm, so that I can start adjustment. However, this one I use is somehow end up at the highest 200 ohms. After I found this out and turn it all the way down, I got my Q7 up to 4+V and the heat sink starts working now....
Great!
Thomas
I found out my problem! The VR2, I was turning all the way down to 0 ohm, so that I can start adjustment. However, this one I use is somehow end up at the highest 200 ohms. After I found this out and turn it all the way down, I got my Q7 up to 4+V and the heat sink starts working now....
Great!
Thomas
Yes, but be careful and use only a tiny bit. Don't spray the stuff all over the current source or diff pair. One semiconductor at the time, starting with the CS and zener diode. Wait long enough between shots. You could of course replace the semi's. The whole front-end is only four of them.Taco said:
I suggested an old speaker because the result is immediately audible. Measuring the outputs with a scope requires the knowledge the see what is hum and what not.GRollins said:
/Hugo
Netlist said:
Yes, but be careful and use only a tiny bit. Don't spray the stuff all over the current source or diff pair. One semiconductor at the time, starting with the CS and zener diode. Wait long enough between shots. You could of course replace the semi's. The whole front-end is only four of them.
I suggested an old speaker because the result is immediately audible. Measuring the outputs with a scope requires the knowledge the see what is hum and what not.
/Hugo
That's clear, first thing I'll try is to check the abs. off-set. But I've first to find some time
.Taco said:
That's clear, first thing I'll try is to check the abs. off-set. But I've first to find some time
Today I have done the measurements, abs off-set is after warm-up around zero 100 mV or so. The relative off-set (speakerterminals) is 20mV. So I think the problem lies in my powersupply caps.
I had the same problem with my AX. I found that it was because of capacitors in the PSU. There were snap in type and started vibrating with time. Try to touch pushing capacitors by finger and listen to if the hum is changing. If so than you need new capacitors (better with srew terminals ).
Maybe it helps.
Regards
jarek said:
I have computer grade BC screw terminal caps. These are bought surplus so they have been on the shelf for a long time. Those caps are glued to the bottom of my amp.
An externally hosted image should be here but it was not working when we last tested it.
Taco
If the caps are new and BC computer grade, you took among the best there are IMO.
Of course one of them could have problems, one never knows.
For some reason I don't like the resistors you use between the caps. The wires look too fragile to conduct that amount of power cleanly.
The cheapest way to test if they are the culprit, is to bypass them with solid wire, firmly attached.
You will have more ripple (and a slightly higher supply voltage) when cold but it should stay the same when the amp warms up.
I included a picture to show you how I did it. Big, solid resistors, mounted on the alu base where the caps rest, strong solderings and tick wire.
Let us know what you found.
/Hugo
If the caps are new and BC computer grade, you took among the best there are IMO.
Of course one of them could have problems, one never knows.
For some reason I don't like the resistors you use between the caps. The wires look too fragile to conduct that amount of power cleanly.
The cheapest way to test if they are the culprit, is to bypass them with solid wire, firmly attached.
You will have more ripple (and a slightly higher supply voltage) when cold but it should stay the same when the amp warms up.
I included a picture to show you how I did it. Big, solid resistors, mounted on the alu base where the caps rest, strong solderings and tick wire.
Let us know what you found.
/Hugo
Attachments
jarek said:
The whole circuit is at the moment not grounded to the case
(first thing I tried).Netlist said:Taco
If the caps are new and BC computer grade, you took among the best there are IMO.
Of course one of them could have problems, one never knows.
For some reason I don't like the resistors you use between the caps. The wires look too fragile to conduct that amount of power cleanly.
The cheapest way to test if they are the culprit, is to bypass them with solid wire, firmly attached.
You will have more ripple (and a slightly higher supply voltage) when cold but it should stay the same when the amp warms up.
I included a picture to show you how I did it. Big, solid resistors, mounted on the alu base where the caps rest, strong solderings and tick wire.
Let us know what you found.
/Hugo
Those BC caps aren't new, yes the are unused when I bought them, but the production date is mid nineties I think. I'm sceptic in bypassing the resistors, I am not sure my heatsinks can take the extra heat (they most likely will). Also, everything worked fine with those resistors and still do in the other channel
. How can these resistor create a ripple on the voltage rails?
Resistor with thin wires
> For some reason I don't like the resistors you use between the caps. The wires look too fragile to conduct that amount of power cleanly.
Well I thought you actually want some resistance at that location in the CRCRC, so I can't see any problems with thin wires at the R, scientifically speaking.
Furthermore, both your resistors and those from Taco are wire-wound resistors (yes, even those in nice aluminium housings) -- guess how thin and long those wires are within the resistors themselves (Break one up to find out for yourself, the ceramic ones cost less than 10 cent each). And that also means that they have inductance -- which is also not unwelcome in a CR(L)CR(L)C.
If you really want them 'clean', try some Vishay RCH50 resistors (available from RS at around 4 Euros, still affordable for 50W). They have less than 50nH inductance. Then you can claim pure CRCRC. I wonder if you would hear any difference.
Patrick
> For some reason I don't like the resistors you use between the caps. The wires look too fragile to conduct that amount of power cleanly.
Well I thought you actually want some resistance at that location in the CRCRC, so I can't see any problems with thin wires at the R, scientifically speaking.
Furthermore, both your resistors and those from Taco are wire-wound resistors (yes, even those in nice aluminium housings) -- guess how thin and long those wires are within the resistors themselves (Break one up to find out for yourself, the ceramic ones cost less than 10 cent each). And that also means that they have inductance -- which is also not unwelcome in a CR(L)CR(L)C.
If you really want them 'clean', try some Vishay RCH50 resistors (available from RS at around 4 Euros, still affordable for 50W). They have less than 50nH inductance. Then you can claim pure CRCRC. I wonder if you would hear any difference.
Patrick