This is not just another gainclone

Status
Not open for further replies.
Jump to Latest
#2,062
Cable

Thanks a lot for answers.
To be honest that's the very first amp it behaves that way with that cable (Alephs for example work great) and I like that cable a lot,couse it sounds wonderful,and that is why it bothered me (Instead of my favorite one I had to use some ordinary Cordial speaker cable).
 
#2,064
I was just playing with my new toy (a Tektronix 2232 scope 🙂) and my gainclone.

I looked at the supply voltages:
in DC mode, I saw a nice flat line, 25V DC
In AC mode, with a little more sensitivity, I saw something like a sawtooth

100Hz (normal) 0.4V p-p

I found this very high, but after easy maths:

(F*V)*S=A

with 1000uF, 0.4V and 0.01s, I got 0.04A (40mA)

This is at idle, quite normal.



Have other people looked with theyr scope on the supply rails?
 
#2,065
Bricolo said:

Have other people looked with their scope on the supply rails?
Click to expand...


yes, I was given a scope a while back - really helpful

did you look at the ac on the secondary ? according to the theory, and on a simulator, there is HF ringing just after the diodes switch off.

In real life I have yet to see this. I would be interested to hear what you see if you feel like having a look.

wether you see anything or not I think you will probably notice a big improvement in the sound if you put a 4.7uF cap directly across the secondary. which suggests that there is something going wether it can be seen as a voltage or not. perhaps trying to have a look at the current would be more revealing.

cheers

mike
 
#2,067
Stupid question:

how did you look directly at the secondaries with your scope?

My scope is connected to earth, and I think that it's the same earth that is on my probes. So how can I connect my scope to the secondaries, as none of the 2 wires of the secondaries is connected to earth?
 
#2,068
Bricolo said:
Stupid question:

how did you look directly at the secondaries with your scope?

My scope is connected to earth, and I think that it's the same earth that is on my probes. So how can I connect my scope to the secondaries, as none of the 2 wires of the secondaries is connected to earth?
Click to expand...

well, the secondary windings should be completely isolated as long as nothing is connected to earth in your gainclone.

If this is the case, and you can check this with your multimeter ohm range with the cct TURNED OFF, then you can ground one end of the secondary with the probe earth and measure the other.

my mate at work says measure twice cut once...in this case it's good to check twice measure once !

mike
 
#2,070
Bricolo said:
Sorry, but you're wrong.

The "middle point" between the 2 diodes briges is my star ground, and is earthed.
Click to expand...

OK, that's fine, there are two ways around this. You could either temporarily disconnect this earth so the the amp is floating with respect to earth and proceed as discussed before or if you have two i/p on the scope connect both the i/p earths to the star ground of the amp and connect the probes to either side of the secondary. if you 'sum' the two channels. You should be able to see what is going on. Without setting it up my here I can't recall if you need to to pase invert one channel or not, but it only takes the flick of a switch to find out.

alternatively you could just try the cap across the secondary and see if you like the effect

at present my clone is supplied by batteries so I can't do a meaningful comparison

cheers

mike
 
#2,073
Bricolo said:
I've looked at the secondaries: a nice sinusoid 🙂

No HF garbage (except a mV or so, don't even know if it's really on the secondaries, or if it comes from my probes)
Click to expand...

That sounds more or less what I have measured, I think that most of the theoreticl ringing must be inhibited by winding capacitance.

I hope that your observation of a clean waveform does not put you off the idea of trying the cap...😉

mike
 
#2,075
Bricolo said:
I'll try the cap 😉

Have you looked at your secondaries?
How does the AC look?


If I find the manual for my tektronix 2232, I'll try to get data with the comouter and post some graphs
Click to expand...

only on my class A amps. on those the sinewave has a flattened top because of the high current, just after this they may be a hint a wiggle, not much.

I will try to measure current on the scope sometime

cheers

mike
 
#2,077
Bricolo said:
I did a mistake

I wrote secondaries instead of supply rails.

Did you look at your gainclone's supply rails with the scope?

just tell me if (in AC mode) you also have a kind of sawtooth, and what is it's amplitude peak to peak
Click to expand...

I'm sorry I can't do that at present. my current chipamp runs off batteries. I'm in the process of building the very best chipamp thay I can manage. On this I will try batteries & mains.

However the sawtooth that you've measured sounds completely typical & normal for the kind of current that you are drawing

mike
 
#2,078
Peter Daniel said:
Few people asked me about it already. I bought them locally at Active Surplus. They've been there for months and I didn't really know how to use them. It's after building my first gainclone I figured they might be perfect size for that amp. So I went there and bought all of them (about 12 pcs.). There are still few left, but they are slightly damaged on the fins.
Click to expand...


MPJA.com has the same heat pipes. Be aware that the way these are mounted inthe picture SEVERELY limit the effectiveness of heat pipes. Because they use fluid convection, they must be mounted vertically to do any real good as heatpipes. They may still work as conventional heatsinks, though.
 
Status
Not open for further replies.
Top Bottom