carlmart, thanks for the suggestion, changing the capacitors is easy, I can do that from top of the board, and see if I can measure any improvement, but as I explained I use limited setup, just a laptop with RightMark software, no fancy stuff
as for adding the zener and other diode for drivers, that would likely require removing the boards from the heatsink...so I will see about that
as for adding the zener and other diode for drivers, that would likely require removing the boards from the heatsink...so I will see about that
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Removing C24 will not change the poor THD in LTSpice simulation.
First try changing C20, C22 and C23 onto 3.3p. That would bring THD down from 0.026% to 0.0055% @ 1KHz. Those values are close to those on the original GM, which were 4.7p.
You should look at a scope when you do these changes, because some factors, like the pcb design, might demand adjusting those values up slightly. But the secret of this amp AFAIK is the small value of these caps.
Changing C21 would bring additional improvement.
First try changing C20, C22 and C23 onto 3.3p. That would bring THD down from 0.026% to 0.0055% @ 1KHz. Those values are close to those on the original GM, which were 4.7p.
You should look at a scope when you do these changes, because some factors, like the pcb design, might demand adjusting those values up slightly. But the secret of this amp AFAIK is the small value of these caps.
Changing C21 would bring additional improvement.
What is the protection schematic Goldmund builders here are using or plan to use?
The original protected watched DC offset and oscillations, which a fast amplifier like the Goldmund might be sensible to.
I think it's no coincidence that Goldmund added oscillation protection to their design.
Are there more modern or recent or more effective alternatives to that protection?
The original protected watched DC offset and oscillations, which a fast amplifier like the Goldmund might be sensible to.
I think it's no coincidence that Goldmund added oscillation protection to their design.
Are there more modern or recent or more effective alternatives to that protection?
Hi,
I got them. Thank you very much, it helps. But I don't know whether it could be posted?
Yes, surely it's my board.
ZFT? I guess you mean FZT857/957?
You can get them on mouser, RS, etc.
I would like to build this clone. How do I purchase the PCB ? Does any one have a link ?
Thanks
I will publish officially once I get them all set.
Regards,
Eric
Erikovsky,
One of the good things in the original Goldmund DC protection is that it also protects from oscillations.
So I wonder if in the protection you designed, based on the UPC1237 chip, we can also add the filter Goldmund puts on theirs.
Here's a drawing of both.
One of the good things in the original Goldmund DC protection is that it also protects from oscillations.
So I wonder if in the protection you designed, based on the UPC1237 chip, we can also add the filter Goldmund puts on theirs.
Here's a drawing of both.
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Hi all,
Finally, the two series of my 8th generation GM have already arrived.
I call them GM8-Classic and Deluxe.
The GM8-Classic:
The GM8-Deluxe:
Finally, the two series of my 8th generation GM have already arrived.
I call them GM8-Classic and Deluxe.
The GM8-Classic:
- 1 pair TO-3 MOSFET
- mini size
- gold-plated
- no exchangeable module
- no PSU
The GM8-Deluxe:
- 2 pairs of TO-247 MOSFET.
- Gold-plated with double thick copper.
- Equipped with interchangeable module sockets.
- integrated with rectifier/filtering.
- Voltage doubler for front-end supply.
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Hi,
Yes, I have tried uPC1237 on my 7th generation design, so I didn't do it again on my 8th design.
uPC1237 is a great IC that integrates many essential function. I think I will try to make a very tiny 1237-based protection board, and soldered on the speaker terminal. This way, the size of main board could be decreased.
The filter (10R+~30nF
is already on the board. I plan to connet L//R directly on the terminal.About the price, since it's well-processed (Gold+2Oz copper), I'd say, ~19USD/pcb. Each PCB contains 1 chaneel, so at least you need 2 boards.
Regards,
Eric
The filter (10R+~30nF
Would that work as an oscillation filter?
Where's that protection schematic with that filter? It's not on the one I uploaded.
Isn't it better to use separate protections for each channel?
A very fair price for what seems like very good quality pcbs. How much would it cost to ship two boards by air-mail to Rio de Janeiro, Brazil?