My Take on X-BOSOZ

[jleaman]

Originally posted by Assesears
Need some help/advice here, I've developed a fault on the left channel of my BosoZ which is large amounts of hiss out of the speaker, changed over channels of source and amp, swapped over power supply and pots, changed out diodes, checked for cold solder joints and still no joy, hope its not the fets. Any help/idea's appreciated.
Cheers Bruce

Humm yes mine to has some hiss. I can't do any thing about it at the moment as im moving but when i move i can listen to it more closly and see what i can come up of it.

[cjd]

I'll be able to let you know how mine sounds shortly.

Just have to connect the source to the pre and the pre to the amp and it's ready to go!

Munching some home made something or other dessert that's delicious though, so gotta finish that first.

C

[cjd]

Well...

After one stupid mistake (power supply backwards, somehow, after checking it 3 times) it all works. Blew the 22uF cap pretty quickly, so hopefully no harm done beyond that. Seems to be none. Only one channel, so I'll just add another part to the order I need to place.

It's still very quiet. Changing to a source that puts out more and it picks up distortion still. So I must have something amiss in my amp circuit. I'll get the schematic to you guys soon, I've been updating it with everything.

The Joshua Tree works fine, but there is one spot that has a very distinct "pop" when one relay switches on. I haven't tried to isolate which "side" it's on, and I haven't tried the other board yet.

Otherwise, it's quiet, and very clean, when it's playing within the range where it works well. No hiss that I noticed. And a definite improvement over running the X-GC with single ended input straight in.

C

[Vigo]

Can you destroy the fets if you try and mersure the resistens betwen the legs without the power connected?

[Russ White]

Hi Vigo,

FETs typically are extremely sensitive to ESD. It is always wise to be very cautious about grounding yourself very well while working with them. Wearing a grounding strap while handling FETs is a good idea. I usually just make it a habbit to put mine on when I start to work on my electronics.

I have killed a dozen or so FETs just by walking across a room getting something and touch a trace connect to the gate of a FET before grounding myself.

Cheers!
Russ

[cjd]

Russ, do you have a thread or place where you're supporting the JT? I'm having definite issues... no solder problems that I've found going over it with the magnifying eye glasses.

C

[Russ White]

Hi C

That thread is here:

http://www.diyaudio.com/forums/showt...119#post848119

And the last few posts , may help you out.

Also note that the attenuator will give you a pop in a couple spots if there is any DC in the signal. The more DC offset the more the pop. This is actually common for switched attenuators (not just relays). The best way to eliminate it is to eliminate the DC.

It is common to forget about DC offset on the inputs of a power amp.

Cheers!
Russ

[dytln_02]

how many gain gain for this pre-amps ?

Can it use as headamps ?

[cfbuck]

Russ,

I'm a raw novice at electronics and I have just soldered up my Power Supplies for the XBOSOZ kit. I have the Avel transformers. I will wire them as follows:

Positive
- outputs - red/orange shorted together,
- Yellow to AC+1,
- Black to AC+2
- 120 VAC inputs - Violet + Blue to Neutral
- Brown + Grey to Hot

Negative
- outputs - red/orange shorted together
- Yellow to AC-1
- Black to AC-2

I noticed in the post listed below in which you were illustrating how to measure the voltage on both +ve and -ve outputs, that you had two components mounted on the bottom of your ps board.

http://www.diyaudio.com/forums/showt...885#post856885

What were the components, where are they mounted and what do they do?

After powering up the board, and measuring the DC voltage, do I have to short each capacitor with a resistor to unload it for safety? If so, what is the recommended resistor size?

TIA, Fred

[Russ White]

Hi Fred,

The components you see on the bottom are 10K 3W resistors between the capacitor leads. I used them to drain the capacitors during unloaded tests of the power supply for safety. When you have the power supply connected to the preamp it will always be loaded since the circuit is class A. So for normal use they are not really required, but they certainly don't hurt either.

Your transformer wiring appears correct as described.

Cheers!
Russ