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and now for something completely different part 3


kevin gilmore
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20 hours ago, Pars said:

Anyone have a CFP3 BOM? Excel spreadsheet preferred, but google or whatever is fine as well. Thanks!

Sure, here is the Mouser BOM for the CFP2/CFA2, order two times for the CFP3/CFA3. Here the BOM for the GRLV 30V for it as well. Some of the transistors are currently on back order, if you know of a viable replacement would be great. I've also made the latest CFP3/CFA3 version 2oz boards, so if you need some let me know. This would be the ready made transformer for the CFA2 as well. 

This above is for the non-stat version. For the static CFP3/CFA3 I have it as well together with the BH Mini PSU v1.4. 

@Pars

Edited by starcat
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I mentioned this in the dynahi thread, but after getting the input wiring fixed (cable jackets were putting too much pressure on the screw down terminals resulting in intermittent channel drop), I ran into another problem with the protect circuit tripping. It turns out that I had broken the ground connection at the pot of one of the wiper to amp cables.

This connection is the only connection between the L and R channel grounds in the amp. The amp uses dual GRLVs, one per channel.

Should I connect the DC grounds of the GRLVs to one another back at the PSUs? I'm thinking Yes.

In this instance, I was seeing a DC offset of what appeared to be 36V, but that was dependent upon which ground was being referenced (which I didn't realize at the time). I found that when I ohmed out the input grounds between boards and it wasn't 0.

Edited by Pars
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7 hours ago, Pars said:

Should I connect the DC grounds of the GRLVs to one another back at the PSUs? I'm thinking Yes.

I read somewhere a comment especially on this from Kevin saying both grounds must be connected. Can't remember which amp thread this was. 

Are you using a separated PSU chassis? 

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This is an amp built by Mirko, that tkam bought from someone on HF I presume. The right channel was flaky, and since the builder is in the EU, he asked me if I'd take a look at it. It is in a single 2U 400mm Modu Pesante case.

This isn't the exact amp, but similar.

11303526.jpg

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Like I said, this isn't the exact amp I'm working on. The board on the right is a Gilmore protect board (HIGHLY recommended on one of these). The one on the left in this amp I believe is doing the SS/ZF switching.

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Dukei (Mirko here) uses something similar to that. One of the reasons I ask is there is a difference in volume between modes (ZF is a bit louder), but more disturbingly, there is a slight image shift when switching between modes. I noticed this when using a 1khz test tone. The image shifts a bit to the left when moving to ZF.

Per my previous question, the ZF resistor is the 1.9K resistor in the schematic and PCB? I assume so, but just wanted clarification,

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1 hour ago, Pars said:

Per my previous question, the ZF resistor is the 1.9K resistor in the schematic and PCB? I assume so, but just wanted clarification,

That's correct. R50/R51 on cfa3productionss.pdf

1 hour ago, starcat said:

Guys, where can I get some more information on the implementation of the SS/ZF switching board? Appreciated all the great work you are putting in. 

There is none but you can do it like I did and use relays to short/open the positions.

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