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Old 31st October 2010, 05:56 AM   #1031
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I think that the TO-3 version of the board should be made. If people decide to use the TO-3P transistors, they will still fit. The 2 outer pins of the plastic version transistor just need to be bent 90 degrees to go through the PCB holes.
The source (case) will be connected with a single screw to the PCB.
Daniel
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Old 31st October 2010, 07:17 AM   #1032
BV is offline BV  Slovakia
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Quote:
They are not vital
They are vital for good current sharing. Other way precise selecting of Mosfets (Vgs treshold and Vgs vs Id) is a must.

Last edited by BV; 31st October 2010 at 07:19 AM.
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Old 31st October 2010, 07:53 AM   #1033
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Quote:
Originally Posted by BV View Post
They are vital for good current sharing. Other way precise selecting of Mosfets (Vgs treshold and Vgs vs Id) is a must.
Then you must buy 100+ , sort them into groups. Even WITH .22R emitter resistors and BJT's, crude matching is recommended. Had an amp with all devices dropping 13mV Re , one dropped 17mV ... guess which one blew ??


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Old 31st October 2010, 08:16 AM   #1034
alex mm is offline alex mm  Romania
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Default PCB REV 3.7

.... thanks for comments , I'v don latest changes so PCB pictures
I think it's completely nonsens to make another PCB , it's time to go a had to support another topic
Alex.
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File Type: jpg PCB REV 3.7.JPG (325.8 KB, 1134 views)
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Old 31st October 2010, 10:38 AM   #1035
sng001 is offline sng001  Australia
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Default PCB Rev 3.7

Hi Alex,

Thanks for the quick changes.

Can you please double-check the hole size for the 10000uF capacitor? If the picture represent the actual hole size, then they look like 1.5 to 1.6mm diameter and that will not fit the snap-in capacitors (which require 2mm mounting holes). The potential builder cannot drill that out either as the speaker ground is connected to one of the 10000uF cap.

Cheers, Stanley
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Old 31st October 2010, 10:53 AM   #1036
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They are not supposed to be 10000uf anyway they should be 4700uf. Is that right Nagys or have i mixed it up with something else?
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Old 31st October 2010, 12:02 PM   #1037
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Hi Alex,

I think that will be better if you rotate at 180 degree 100uF capacitor near 10000uF and heatsink. In that case ground pin between 100uF and 10000uF will be closer.

Best regards
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Old 31st October 2010, 12:15 PM   #1038
Liliya is offline Liliya  Norway
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Hopefully we are close to have our PCB for the Golmund clone. From time to time Nagys/Alex/Bigpanda receive questions that will result in changes on the PCB.

Mostly Nagys rejection is in respect to the orginal. Thatís ok, but why is it so diffucult to take into account solutions that give alternative options and still satisfy those who want to be faithful to the original.


Let me mention three issues from some of the latest posts:

C31/C34: 30 or 35 mm and holes for snap in.

Source resistors. Do we know if Golmund have matched them or not? Even if they have not:

For those who will feel more comfortable with an opportunity for source resitors, let us have it. We can cut the copper lane between the mounting holes for the source resistors. Or use a bare wire for those who want to bypass.

Eivind Stillingen
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Old 31st October 2010, 12:30 PM   #1039
sng001 is offline sng001  Australia
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Default Max diameter for C31/C34

Quote:
Originally Posted by Liliya View Post
C31/C34: 30 or 35 mm and holes for snap in.

Eivind Stillingen
Hi Eivind,

I have checked, 35mm diameters capacitors can be installed on the last two PCB version by alexmm.

I think that is up to builder to choose the capacitance - the board can fit anything from 4700uF to 10000uF.

Cheers, Stanley
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Old 31st October 2010, 03:47 PM   #1040
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If the schematic says 4700 why use a higher value? Is it because we know better? After all a higher value can only be better right?

Quote:
Originally Posted by ivodonchev View Post
2. Lowering the +/-80V at output stage down to +/-50V will NOT LOWER the power of the amplifier and will not increase THD. I think that Goldmund's reason to use 80V is probably sonic performance not measurable. At the some time with +/-80V at high power and 4 Ohm load the output mosfets will go out of power range easily. Probably that's why they use not oversized transformers and only 4700uF capacitors because this will give around 73V at high power and low load. This will be a little bit safer for output mosfets.
For those wanting to use 1000 watt torroids and big caps consider what ivodonchev points out. The use of the smaller size transformer and capacitor values could be a deliberate design choice.
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