Hi,
I follow with interest your discussion about this project and I am determined to build this amplifier! I have already issued several orders for parts as BOM and schematic but I still have some doubt about the resistance values!
Eg. In Goldmund amplifier schematic the value of R36(parallel with L1) is 0,22R/3W. In protection schematic, parallel with L1 is R25 1K!? which one is real value/ better option?
Also, for power supply, I ordered 500VA toroidal transformers for each channel, with secondary 60V-0-60V AC/1A on input stage and 60V-0-60V AC/3A on power stage.
I have the patience to wait for those with experience to complete this project, then I will finish to! Until then maybe someone will review the schematics and BOMs!
Thank you and good luck!
P.S. an equivalent for BC449 ?
I follow with interest your discussion about this project and I am determined to build this amplifier! I have already issued several orders for parts as BOM and schematic but I still have some doubt about the resistance values!
Eg. In Goldmund amplifier schematic the value of R36(parallel with L1) is 0,22R/3W. In protection schematic, parallel with L1 is R25 1K!? which one is real value/ better option?
Also, for power supply, I ordered 500VA toroidal transformers for each channel, with secondary 60V-0-60V AC/1A on input stage and 60V-0-60V AC/3A on power stage.
I have the patience to wait for those with experience to complete this project, then I will finish to! Until then maybe someone will review the schematics and BOMs!
Thank you and good luck!
P.S. an equivalent for BC449 ?
Hotzman
Correct value R 36 = 0,22 Ohm.
The transformer you have chosen fits very well. Since you have chosen separate windings for the front ends, I will recommend you strongly to look at what I have done. Find a suitable transformer and connect them to the 2x60 V AC 1 amp windings to get a higher voltage for the front ends and built MJLs power unit. I am sure he will help you to calculate the right values for R2,R3 og R4 for the voltage you desire to run for the front ends. Remember to use capacitors that can meet the high voltage. Most of the capacitors from the original voltage doubler in the Goldmund can be used in MJLs power unit.
The original voltage doubler should be avoided at any price!!!
Eivind Stillingen
Correct value R 36 = 0,22 Ohm.
The transformer you have chosen fits very well. Since you have chosen separate windings for the front ends, I will recommend you strongly to look at what I have done. Find a suitable transformer and connect them to the 2x60 V AC 1 amp windings to get a higher voltage for the front ends and built MJLs power unit. I am sure he will help you to calculate the right values for R2,R3 og R4 for the voltage you desire to run for the front ends. Remember to use capacitors that can meet the high voltage. Most of the capacitors from the original voltage doubler in the Goldmund can be used in MJLs power unit.
The original voltage doubler should be avoided at any price!!!
Eivind Stillingen
Yeah, Just a BIG picture of it ALL working together, not speakers or such just the amp and supplies and such...
Yes you have been more than wonderful to share your experiences with us, Thanks again for your willingness and your expertise in bring the beast to LIFE...
Enjoy the Fruits and seeds of your creation...
Yes you have been more than wonderful to share your experiences with us, Thanks again for your willingness and your expertise in bring the beast to LIFE...
Enjoy the Fruits and seeds of your creation...
Jacco you wrote:
Only (bypass) caps i've seen in the schematic/boards are 10nF between drain and (star) ground, not the source of the power MOSFETs.
Of course you are right. C (10nF) is connected between drain and ground.
And the purpose of this caps is??
Andrew you wrote: An SF (=BJT EF) output device has the drain attached to supply so an SF requires the drain to be capacitor coupled to the sink.
SF is an abbreviation for source follower I guess. Sorry I have to get this"into the teaspoon". And in my Goldmund drain is connected to the + and - supply.
Conclusion: A 1000pF cap from drain to the heatsink could be an alternative to cure a possible oscillation on the Goldmund. And the caps that I have mounted between drain and star ground should not be removed???
Eivind Stillingen
Only (bypass) caps i've seen in the schematic/boards are 10nF between drain and (star) ground, not the source of the power MOSFETs.
Of course you are right. C (10nF) is connected between drain and ground.
And the purpose of this caps is??
Andrew you wrote: An SF (=BJT EF) output device has the drain attached to supply so an SF requires the drain to be capacitor coupled to the sink.
SF is an abbreviation for source follower I guess. Sorry I have to get this"into the teaspoon". And in my Goldmund drain is connected to the + and - supply.
Conclusion: A 1000pF cap from drain to the heatsink could be an alternative to cure a possible oscillation on the Goldmund. And the caps that I have mounted between drain and star ground should not be removed???
Eivind Stillingen
Eeh, local bypass caps ?
(you require the use of them explained as well ?)
The higher the frequency range, the more susceptible an amp is to oscillation due to parasitics.
Lateral MOSFETs are highly sensitive to parasitics, more so than other power device types.
Vertical power MOSFETs can fairly easily be (hard)wired to a board, even at a rather long distance, see e.g. all the Pass Aleph works.
Doing the same with Lateral MOSFETs is pretty unsensible in Any case.
A power amp with a Lateral MOSFET output stage, that does a +1MHz bandwidth, will be extremely prone to oscillation, and may have trouble with the bypass cap traces to star ground as laid out by Alex.
So the suggestion was to connect the bypass caps to the heatsink INSTEAD of to the traces in the board that connect to star ground, NOT adding some more bypass caps.
The heatsink is the closest ground to the power devices, and the largest ground mass in the entire amp, as close an equivalent to soldering the bypass caps leads straight at star ground dead center.
The link to Mr Hansen's post was merely to illustrate that even a commercial expert of Lateral devices agrees that it's a viable option to cure (prevent) oscillation issues.
The link was Not meant to add more confusion, Not implying that you should exchange the 10nF for 1nF, or use both (pfff).
Contact OMRON or FINDER they have offices over yonder, look them up and look for the sales office.