Driving capacity of BOSOZ

[PRBS]

Recently, I finished Aleph 2 amp. (see attached pictures) The sound of A2 is very musical, natural and realistic. I love its sound. I also finished BOSOZ few months ago. The sound impressed me at the first running. I am very happy with those. 🙂Thank you Pass shares such good stuffs to DIYer.

Now I have a plan to set up a bi-amp system without active crossover. That is Aleph 2 for bass, and build another Aleph 5 for tweeter. Those Alephs driven by BOSOZ. I use 10k volume pot at the input, and without volume pot at the output. Can BOSOZ drive two Alephs amps with unbalanced input?

 

[fcel]

Wow, that's a pair of nice looking amp!

Could you also show a picture from the rear - I would like to see where you install the input and output jacks.

I presume you have the fins trim off from the bottom half of the heatsink or you don't have heatsink at all on the bottom half.

Please also describe the placement of the 12 output transistors. I'm guessing 4 transistors on each of the 3 heatsink and the 4th heatsink is for the cosmetic looks only (or use as power supply rectifiers heatsink)?

By the way, you couldn't find any feet for the amp?

Thanks.

 

[PRBS]

Here is the backside. It's as like as orginal Aleph 2.

 

[PRBS]

I use 4 heatsinks for total 12 transitors. Each heatsink contains 3 transistors.

 

[PRBS]

With main circuit board.

 

[Jean]

Great job! One question though, whats the size of the heatsinks and any details on the power supply ?

 

[fcel]

Did you have that 2 fins at the rear trimmed off by yourself or you have it custom made? Very nicely done!

 

[PRBS]

The heatsink size is 310x180x40 cm with 4mm base plate.

I use a 1.5kV transformer and four 22000uF/63V ROE capacitors per channel. The artwork of PCB is come from Brian. Thanks Brian.

 

[PRBS]

I just design how to assemble. Make a drawing and sent it to machine shop to build the case. (heatsinks)
I have no machine can do that.

 

[Jean]

Nice! I can see you are using two bridge rectifiers and the caps are wired in parallel (two per rail). I assume you are running the rectifiers in parallel then ?

 

[PRBS]

Yes I am. I made another simple delay circuit to bypass thermistor with relay after few seconds turn on power. To prevent voltage drop cross themistor under such high power consumption.

Does anyone reply me? Can BOSOZ drive two Aleph amps well with unbalanced input?

 

[fcel]

That delay circuit looks very much like the one shown on ZEN version 1 or 2 write up but operate at a lower voltage. I've been wondering, the article says any generic transistor will do but could you provide a part number - sorry I don't know enough to know what generic number means. You have shown TIP41C - is that a generic part # that I can use to order from Digikey or Mouser?

What kind of rating (again may be a part # too?) do you use for the relay across the thermister?

Thanks.

 

[Peter Daniel]

I made another simple delay circuit to bypass thermistor with relay after few seconds turn on power. To prevent voltage drop cross themistor under such high power consumption.

Since you have a relay with a delay circuit, you would be much better off using a resistor instead of thermistor. Maybe 20-30 ohm, 20-50 watts. I was never too happy with thermistors after I blew few bridges. You also have to wait few minutes after switching amps off to turn them on again, otherwise thermistor is too hot to provide supression. The whole advantage of thermistor is simplicity of using just one part, but since you have the whole circuit to back it up, use a resistor.

BOZ should be able to drive two Alephs, but it also might depend on your interconnects.

 

[PRBS]

Digi-key part# for TIP41C...TIP41CTU-ND. I think most TO220 package NPN transitor can do well at that position.

For the relay, it contains a two-pole switch and wiring the two poles in parallel. Each pole has 15A/110V capacity. Made by OMRON. You may search Digi-key catalogy to find a replacer.

Thanks Peter's advise. So far thermistors work well in my circuit. For me, it is hard to find high power resistors. My Aleph also no extra space to carry a couple of parallel resistors. That's why I use thermistor.

One more thing, the thermistor always cold during normal operation of Aleph 2 but turn switch on then turn it off immediately.