View Full Version : DIY Pass XA160??

12-04-2007, 12:31 AM
To realize my future plan to drive every JBL in my house with Pass Amps another pair of monos was neccessary.

This time I build something in between the XA100 and XA160.

Optimized to 4 Ohm load and providing 160 watts then.

Massive heatsinking was neccessary.

The sound is incredible. A bit more open and wide than the Aleph 2 but still soft and smooth.

12-04-2007, 12:35 AM
Due to the high bias current I even need to cool the rectifiers and need to use masive chockes in the PS.

I also included a DC filter for the mains. We have DC here and it causes the transformer to hum if not treated.

12-04-2007, 12:39 AM
I forgot to say that these amps CAN control the woofers of the 4435. Really ;)

12-04-2007, 01:20 AM
WoW! Great job. Looks very nice. I have no doubt that the XA have better control than the Aleph ;)

Is it possible to ask for the schematics?


12-04-2007, 01:55 AM
Excellent Guido. Enjoy, and keep us updated.

Tim: http://www.diyaudio.com/wiki/index.php?page=Aleph-X

Earl K
12-04-2007, 02:54 AM
Fantastic Guido ! Great Work ! :)

12-04-2007, 04:55 AM

You need more blue L.E.Ds.

Gorgeous :applaud: They should be driving proper JBL's -not those little toy woofers you use....


P.S. they will match my new WADIA very nicely thanks.

12-05-2007, 04:47 AM
Is it possible to ask for the schematics?

It is based on one of Kristijans schematics.

I use 12 FETs per amp and I had to change some of the resistor values to meet the impedance of my 4435.
I have 25V rail voltage and 7 amps of bias.

12-05-2007, 04:51 AM
This looks like an interesting amp :D

12-08-2007, 12:42 PM

Ian Mackenzie
12-08-2007, 01:50 PM
Good idea having the perforated chassic.

Guido, let me know how you go with the transformers.

The idea is to use the next size core up from the VA rating, ie 500VA use a 625 VA core.


12-09-2007, 05:46 AM
I still have problems with humming transformers. Tried several producers.

One is silent, the other hums. Only a bit but too loud.
Ian, those are 1000VA transformers.

Where do I get transformers that doesn't hum? I'm desperate.. :banghead:

12-09-2007, 06:31 AM
Have you seen this one?

In post #4 Magura recommends Talema, which is available from RS under the name Nuvotem. I have only tried up to 500VA in a class AB, but in that setup it there's only a slight hum at startup.

12-09-2007, 08:31 AM
Hi Guido, If you are really keen you could remove the plastic wrap on your transformers and take them to a motor rewind service and have them dipped in transformer varnish. This will lock the windings together and should stop the hum.

Ian Mackenzie
12-09-2007, 11:53 AM
Good idea.

What does the noise sound like?

Is it a constant buzz like windings rattling or is it a hum that comes and goes?

The former is like Allan said. The later is a design issue...I am not an expoert its has to do with saturation of the core due to the very high efficiency of the toroidal. To lower the parameters they use a some what larger core than they would otherwise. Power factor correction can also be a problem if you have a lot of air-conditioners in your area.

I hope to have some answers in a few days when I have Mark's X 100's fully assembled.

Piltron is specialist..send them an email and explain your application.

They wind transformers for all the Hi end manufacturers.


12-10-2007, 01:36 PM
remove the plastic wrap on your transformers

Can I do this? doesn't the wrap fix the winding? Especially where the connecting leads come out?
I plan to cast the transformers in resin. Should I remove the wrap before? If I understand right than yes.

Ian Mackenzie
12-10-2007, 03:56 PM

I dont think you have anything to loose.

Removing the thin plastic will allow the epoxy to cure into the windngs.


12-11-2007, 02:45 PM
Waiting for the resin.

Large enough cups are waiting. Flood them :bouncy:

12-11-2007, 03:09 PM

remember how much heat is generated when resin cures in large volumes !;)


12-11-2007, 03:33 PM
I'm not afraid of heat ;)

Nice avatar BTW

12-11-2007, 09:18 PM
Hi Guido,

You dont need to use resin. In fact I would not recomend that you use it because as it hardens in can shrink and cause failure of the windings. Also the heat from the core is more difficult to dissipate through the resin. All you need to do is to use transformer varnish. It is very similar to normal varnish for wood but it can withstand a higher temperature. All you need to do is to remove the plastic wrap from the transformer and drop the whole thing into a pot of varnish and let it soak for an hour or so. Lift it out and let it drain. I normally use and oven to bake it in for a few hours at about 80-100 degrees. You may get in trouble with that idea though. Just sit the transformer out in the sun or under a heat lamp until it has dried. Re-wrap the transformer and it should cure your problem. :)