Evens C-500 amplifier ....opinions? - Page 4 - diyAudio
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Old 19th March 2010, 06:03 PM   #31
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This is the latest pcb review. Looks great can I have it .
Looks like Evens changed the position of some components. Q1 or Q2 was replaced with diodes?
No one has a PSU design available? Maybe I need to post in the Power Supplies section

Is R8 (39K) the feedback resistor? What exactly does it do?

Last edited by butch_vlad; 19th March 2010 at 06:06 PM.
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Old 19th March 2010, 06:49 PM   #32
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Quote:
Originally Posted by butch_vlad View Post
This is the latest pcb review. Looks great can I have it .
Looks like Evens changed the position of some components. Q1 or Q2 was replaced with diodes?
No one has a PSU design available? Maybe I need to post in the Power Supplies section

Is R8 (39K) the feedback resistor? What exactly does it do?
Hi butch_vlad
Last C-500 I have changed from BF422/423 transistor is MPSA42/92 readily available.

Transistor Q1 is replaced by diodes to create a reference voltage to Q2 is fixed at 3mA constant current test, you must sound like that of a constant current circuit, both of which work well together and have instead.

R8 I use it with 39K values defines the rate of growth, you may reduce it down if they think the growth rate is too high gain, I think that part right.

Click the image to open in full size.

Simple power supply for C-500
Click the image to open in full size.

Last edited by evens; 19th March 2010 at 06:54 PM.
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Old 19th March 2010, 11:37 PM   #33
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Thank you for reply Evens.
The MPSA42/92 can be found easier than bf422/423 indeed.
After I finish testing the first prototype I will try the new design with MPSA42/92 and the new diodes.
Keep us posted with the modifications to the design, this amplifier is worth building and improving.
What do you think about changing Q10 and Q5 with mje340/350? How important are these transistors for the sound quality?....apparently the mje's are inferior to the bf422/423.
Good luck with your work!
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Old 20th March 2010, 02:07 AM   #34
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The way to reduce noise like the hiss you say is present is to reduce the negative feedback network impedance, thus reduce R8, in consequence R4 must also be reduced by the same factor to keep the gain the same. Also R7 must reduce to same value of R8to keep LTP input balance. Another bonus is that this will improve the DC offset by the same factor that you lowered R8, R4 and R7.
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Old 29th March 2010, 12:56 AM   #35
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Finished testing the amp using 2sc5200 and 2sa1943
Sound improved a bit
The amp is stable.....small thump on power up
Will test to extreme to see if I can burn something

Evens can you upload the pdf file with latest PCB please? I want to try the diodes schematic.
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Old 29th March 2010, 11:15 PM   #36
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What can I say.....it has a powerful bass
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Old 29th March 2010, 11:34 PM   #37
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Quote:
Originally Posted by butch_vlad View Post
This is the latest pcb review. Looks great can I have it .
Looks like Evens changed the position of some components. Q1 or Q2 was replaced with diodes?
No one has a PSU design available? Maybe I need to post in the Power Supplies section

Is R8 (39K) the feedback resistor? What exactly does it do?
On this schematics you can see PSU. If you can, use separate wire for VAS suply.
Regards
Attached Files
File Type: pdf crown1.pdf (66.9 KB, 474 views)
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Old 29th March 2010, 11:44 PM   #38
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Thx Apex
This is the original schematic after C-500 is made. The protection and limiters are removed...but the rest is almost identical .
I've managed to obtain some PSU designs so all is good now.
Gonna start building another amplifier now...Evens C-500 is a good project... it has my approval seal
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Old 17th June 2011, 05:57 PM   #39
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can you post the pcb layout of Latest pcb c-500III
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Old 2nd November 2011, 07:15 PM   #40
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Can anyone give me the schematic of C-500 Amplifier
Thanx in advance
my E-mail id : aliskamjad@gmail.com
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