Aleph-X builder's thread.

[Taco]

Originally posted by jarek
Taco, try to compare the ripple on the scope on power lines between to channels (before and after last capacitors). If both channels draw same currents than ripple on lines should be also the same. If not there is problem with psu (likely with capacitors).

Good idea, but I have no scoop . But I can try measure the AC component on my rails with my DVM (or is this nog a good idea). But this exercise has to wait, until I find some time .

[Duck-Twacy]

Taco,

I have a second hand scoop you can borrow for a while (only I still have to buy some proper probes).

Its a rather old Hitachi.

Just send me a mail or something if you'r interrested (probably I'll will be in your place in the Netherlands this week to buy some Ikea stuff ...)

[protos]

I have recently experimented with my Aleph-x on a battery supply!
The results are much better than expected.It is very very close to the huge soundstage and liquidity of my 300bxls set amp but with very punchy and tight bass - better than the AC PS.
At the moment I can only get about 2-3hrs operation on the existing battery supply - but oh what glorious hours.My listening sessions don't last much longer anyway.I am tempted though to go get a pair of 75ah SLA's plus build a 2x8amp charger which could power up everything indefinitely for non-critical listening.At the moment it is 8x7ah sla's.

[EUVL]

Does it not depend on what AC PS you have, how big the battery is, and how much bias current ?

Judging from the fact that you only have 3 hours, probably not a very large battery.

Do you use any electrolytic caps close to the MOSFETS in additional to the batteries ?


Patrick

[protos]

As I mentioned I have 8 SLA's of 7ah each in the battery supply +-12v.Each amp is biased about 4amps into 4 ohm 90db speakers.
I am experimenting with some caps near the mosfets.At the moment I am using 4caps of 680uf Black Gate N non-polar.I will try and go lower with some film caps.In my view you do need a little bit of capacitance even with batteries.Otherwise there might be a tendency to sound slightly bright .Of course just leaving all the original huge electro caps in negates some of the advantages of the battery sound.You can play around with various caps inthis case to suit your particular tastes/system .

[yoke]

Hi...

After some time, I will try to put my AX back in play...
So does any one have some idea what could be wrong when I measure 5V on output ( around 14 to 0 on one side and 9 to 0 on other )...

Whell as some of you mide remember, I have working AX ( or at least that what I think ) but could not set 50% AC current gain...I have replace R12 with 10K pot and I belive I over kill it with triming...I got white smoke come out of amp ( don't know from where...it look like from one output mosfet but when I check it, it was o.k. )...so I belive all output mosfets are fine...
Now I have replace 2x0.22 with 4x0.5 to easier get those 50%...

Now, when I turn amp I get 5V on output and 14-0 & 9-0 V, and I think it oscillates by the sound from speakers ?

any hint what could be wrong ?



Thanks

[Taco]

have you shorted the negative input to ground, when measuring the amplifier? Leave both inputs open or ground also the positive input.

[yoke]

Hi, I don't have amplifier in front of me at the moment, will have tomorow...so I really don't remember how I connect input ( maybe I place capacitor betwin 0 and - ... I think that's it )...
But previously it worked, I used to have cca 0.05V on output and betwin 0 and -/+...

[Taco]

Originally posted by Taco



Good idea, but I have no scoop . But I can try measure the AC component on my rails with my DVM (or is this nog a good idea). But this exercise has to wait, until I find some time .

Thanks to Duck-Twacy for using his scope, here are my findings:

Defective Channel:
=============
on both + and - rails I measure a ripple voltage of 2 V on the first cap (directly connected to the rectifiers). On the - rail it drops after the resistor to ~1 V. On the + rail it's still 2V !!!

Better working channel (Good is misplaced here )
==========================================
directly after the rectifiers, I measured on the positive rail, 1V and after the resistor it is about 100 mV or so. The negative rail also had 2 V and this was after the resistor 500 mV.

Conclusion my powersupply caps are crap and it is a miracle that things still work and that one channel is silent. Very good job Nelson!

[kilowattski]

Any caveats in using the ZTX450 instead of the BC550C on the aleph x?