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Old 25th May 2019, 06:37 PM   #811
force of 1/2 is offline force of 1/2  United States
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What guides the choice of capacitance rating of C9/C10? Is it possible to go with a lower uF cap here?
Would there be a potential attenuation of low frequency if the capacitance is too low? Instability issues?
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Old 25th May 2019, 08:46 PM   #812
delange is offline delange  Belgium
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Hi Shaan,

Today I started populating the first channel of the V4H Rev 1.
When I finished populating the parts I got confused. There where a bunch of components I hadn't used and I thought I forgot to order some 220 and 330 ohms resisters.

The reason why I got confused is due to the fact the the setup guide hasn't been updated to reflect the revision 1 changes. I just mention this so that new builders don't make the same mistakes.

Maybe it is a good idea to update the setup guide?
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Old 26th May 2019, 04:56 AM   #813
asuslover is online now asuslover  Romania
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PeeCeeBee V4H GB
Anyone in US has a pair of V4H rev 1 boards for sale?
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Old 26th May 2019, 11:39 AM   #814
delange is offline delange  Belgium
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I have a question in regards to mounting the mosfets:

From what I understood, the documentation suggests to mount the mosfets against the PCB (bottom side) and fix them to the heatsink by means of the screws from the top side of the PCB. The mosfets are sandwiched between the PCB and the heatsink.

I'm a little bit concerned about this mounting method since the mosfets will also be heating the PCB even though they are mounted against a headsink.
What about long term reliability?

Has anyone measured the temperature on the top side of the PCB while putting the amp under moderate load?

I'm toying with the idea of mounting the mosfets 5mm away from the bottom side of the PCB. I could do that in two ways:

1. use 5 mm spacers to fix the mosfets to the headsink. Downside of this method is servicability; I would need to desolder all mosfets in case of a mosfet failure.

2. Drill two additional 3mm holes on the top sides of the PCB (where the text is). Use those and the holes at the bottom to fix the PCB to the headsink by means of four 10mm standoffs. I would also enlarge the four holes for the mosfets in the PCB so that I can reach the screws to fix the mosfets with a screwdriver "through" the PCB (hope this makes sense).

I'm interested in any thoughts and experiences you guys have.
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Old 26th May 2019, 04:24 PM   #815
shaan is offline shaan  India
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Quote:
Originally Posted by force of 1/2 View Post
What guides the choice of capacitance rating of C9/C10? Is it possible to go with a lower uF cap here?
Would there be a potential attenuation of low frequency if the capacitance is too low? Instability issues?
The low frequency response is inversely proportional to the value of these two capacitors. You can use 1000uF with slightly less gain close to 20Hz. No instability issue with a smaller or larger value but during power-on a large value will make the amp take more time to zero its output offset as it takes longer to charge it.

Quote:
Originally Posted by delange View Post
Hi Shaan,

Today I started populating the first channel of the V4H Rev 1.
When I finished populating the parts I got confused. There where a bunch of components I hadn't used and I thought I forgot to order some 220 and 330 ohms resisters.

The reason why I got confused is due to the fact the the setup guide hasn't been updated to reflect the revision 1 changes. I just mention this so that new builders don't make the same mistakes.

Maybe it is a good idea to update the setup guide?
You are right. R27,28,29,30 are replaced by 100R in Rev1. Also the new 47pF caps are not indicated. I will update it shortly. Thanks for pointing it out.

Quote:
Originally Posted by delange View Post
I have a question in regards to mounting the mosfets:

From what I understood, the documentation suggests to mount the mosfets against the PCB (bottom side) and fix them to the heatsink by means of the screws from the top side of the PCB. The mosfets are sandwiched between the PCB and the heatsink.

I'm a little bit concerned about this mounting method since the mosfets will also be heating the PCB even though they are mounted against a headsink.
What about long term reliability?
You don't need to mount the MOSFETs far from the boards for long term reliability.

A couple V4 boards which are made of the same board material, copper thickness and board thickness as the V4H, are running in my room since mid 2017 and have been under temperature cycling between 55-65C and room temp, almost everyday. No issues.
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Last edited by shaan; 26th May 2019 at 04:38 PM.
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Old 26th May 2019, 04:53 PM   #816
shaan is offline shaan  India
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Update:

Link to corrected setup guide for V4H Rev1 has been shared in Post#1.
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Old 26th May 2019, 06:02 PM   #817
delange is offline delange  Belgium
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First channel finished. I now need some patience and wait for my power supplies to arrive. I'll be using two SMPS600RXE's; I'll be building two monoblocks.

I finally went for the second mounting option (post #814). I drilled two additional mounting holes on top of the PCB. And I enlarged the holes of the mosfet mounting to 8mm. I used 4 metal standoffs to mount the PCB to the heatsink. This provides 5mm of free space between the mosfets and the PCB.
This setup gives me better easy of mind :-)

I also added a ground wire to ground the heatsink.

Pictures attached.
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Old 26th May 2019, 08:44 PM   #818
bambadoo is offline bambadoo  Norway
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Quote:
Originally Posted by shaan View Post
Hi Kamal.

The B class ones have HFE between 250-350. Matching within 50 units is good enough, e.g. NPN 280 and PNP 330.

Matching matters only for Q1,2 and Q9,10 to some extent. All my measurements and listenings are with only Q1,2 matched. No need to buy 100s. Get double of what's needed and sort out the closest matched ones and we're good.
Hi again and thanks for great product.

What is the purpose of Q3, Q4 ? Looks to me as they are direct in the signal path? How is it that matching is of no use for those?
Dont they affect SQ at all?

Just curious
Sincerely

Magnus

Last edited by bambadoo; 26th May 2019 at 08:53 PM.
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Old 26th May 2019, 09:22 PM   #819
shaan is offline shaan  India
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Quote:
Originally Posted by bambadoo View Post
Hi again and thanks for great product.

What is the purpose of Q3, Q4 ? Looks to me as they are direct in the signal path? How is it that matching is of no use for those?
Dont they affect SQ at all?

Just curious
Sincerely

Magnus
Hi Magnus.

I'm glad you asked. Q3/4 are simply the most important components in the whole amp. They act as buffers between input and VAS stage, solving a lot of problems regarding overall amplifier linearity. In simple terms they give the amp a potent weapon to deal with distortion, Gain. The THD level being so low in V4/V4H is a big thanks to them.

A mismatch of hFE in these two transistors have much less effect on the linearity than say Q1/2 pair or Q9/10 pair. Specs other than hFE, like voltage rating etc. have to be matched obviously.
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Last edited by shaan; 26th May 2019 at 09:24 PM.
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Old 27th May 2019, 02:01 PM   #820
asuslover is online now asuslover  Romania
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PeeCeeBee V4H GB
2 bare boards shipping to US anyone?
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