Bora is a nice guy from Serbia - Yugoslávia

[44250]

Originally Posted by Arif Budiyanto

Dear DR. Bora,
My Modus Amp is having 15mV bias setting, 40 Vdc supply. I use fan blower to help its cooling. The sound is very clear, tight and kicked low. I like to play fussion jazz, Rock and Heavy metal songs. Some traditional music songs also (Keroncong) playing by Modus Amp. I plan to raise the bias up to 25 if it possible.
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Some friends who like the sound of my Modus Amp and need to have it, are suggested to contact MR. Bora directly by me. But they have some problem with English.
Thank you so much Dear DR. Bora for giving me the very good design, and all personal emails, since I know that DR. Bora is very busy.
Best Regards,
Arif B

I am not sure,but i beleive that bias for MODUS-TECHNO is about 100mA. Not sure but not far away...

[viktor1986]

Nice work abeteer.

[AndrewT]

Naf,
post704.

the output devices are mounted on the inside of the L angle aluminium bracket.
It is extremely difficult to ensure a flat face here for the devices to contact for good Thermal Conductance (low Thermal Resistance).

If the PCB and output devices are turned upside down then the devices contact the outside face of the L. This face can be checked and altered to ensure it has a goof flat surface for good heat flow.

A further advantage of using the outside face it that the devices can be mounted much closer to the heatsink. Maybe as much as 8mm closer. That reduces the Thermal Resistance considerably. This helps the output stage to run less hot and more reliably.

[Tekko]

Or using a heatsink where the flange is part of the casting/extrusion and not a bolted on L bracket.

[AndrewT]

These can't be extruded. The result is the extra cost of low batch casting production.

[Tekko]

Conrad Heatsinks sell them and i think they are reasonably priced.

[AndrewT]

Yes, I know. I have four of them.

As far as I can tell they are sand cast. I doubt die casting would ever be economic, unless they took over the entire world production of these style of heatsinks.

Sand casting would also explain why the backs/flanges are machined. Another extra cost.

[Arif Budiyanto]

Originally Posted by 44250

I am not sure,but i beleive that bias for MODUS-TECHNO is about 100mA. Not sure but not far away...

Modus bias setting is about 100mA up to 120 mA, but my Heatsink is too small...When I set 100mA (22mV across R 0,22 Ohm) all final transistor were hot, so I think it is better to set bias at 15mV until I get the proper Heat Sink.
Best Regards,
Arif

[naf]

Originally Posted by AndrewT

Naf,
post704.

the output devices are mounted on the inside of the L angle aluminium bracket.
It is extremely difficult to ensure a flat face here for the devices to contact for good Thermal Conductance (low Thermal Resistance).

If the PCB and output devices are turned upside down then the devices contact the outside face of the L. This face can be checked and altered to ensure it has a goof flat surface for good heat flow.

A further advantage of using the outside face it that the devices can be mounted much closer to the heatsink. Maybe as much as 8mm closer. That reduces the Thermal Resistance considerably. This helps the output stage to run less hot and more reliably.

AndrewT thanks for your suggestion i will considering it when i've finished my second monoblock.

[44250]

Originally Posted by Arif Budiyanto

Modus bias setting is about 100mA up to 120 mA, but my Heatsink is too small...When I set 100mA (22mV across R 0,22 Ohm) all final transistor were hot, so I think it is better to set bias at 15mV until I get the proper Heat Sink.
Best Regards,
Arif

Sorry,didn´t considered that...