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Old 1st May 2014, 04:45 PM   #11
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Quote:
Originally Posted by juma View Post
So, it's a single rail 24V power supply, clean 5W cl. A amp that you want - Laterals at the output, different sounding than ACA, right ?
Exactly

Thanks a lot, much appreciated.
Eric
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Old 1st May 2014, 04:50 PM   #12
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Quote:
Originally Posted by fab View Post
This description fits more the one Nelson shown in post 3.

The last one from Juma should also be a good alternative although I would use double polarity supply to get rid of the big output cap...

Fab
Good idea but I have many single rail +24V supply that I want to put to use so I'll stick with single supply, plus I like the added protection of the output cap with my sensitive full range.

Thanks,
Eric
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Old 1st May 2014, 08:57 PM   #13
mos57 is offline mos57  Italy
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Quote:
Originally Posted by juma View Post
So, it's a single rail 24V power supply, clean 5W cl. A amp that you want - Laterals at the output, different sounding than ACA, right ?

This is what I like (sch. in attachment) - one more F5 modification.


And yes, C2 polarity should be reversed (drawing error).

Seem to me that C2 polarity is right since your circuit is a single supply type.

Indeed, to me it looks like a native dual power supply circuit and arranged pretty bad to work with a single power supply.

It seems that your circuit is not balanced at all in the actual operation, being that Q1 working as a CE amplifier while Q2 works as a CC amplifier. For which the two drive signals of the power mosfet are quite different.

Then, what is the purpose of using the network formed by R12, R13, C4, D1?
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Old 1st May 2014, 10:16 PM   #14
juma is offline juma  Germany
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Quote:
Originally Posted by mos57 View Post
Seem to me that C2 polarity is right since your circuit is a single supply type.
Yes, you are right on that one, my mistake - I posted in a hurry...

Quote:
Originally Posted by mos57 View Post
Indeed, to me it looks like a native dual power supply circuit and arranged pretty bad to work with a single power supply.
If you put your mind into it, it can look like an ice cream, or whatever you want it to look like...

Quote:
Originally Posted by mos57 View Post
It seems that your circuit is not balanced at all in the actual operation, being that Q1 working as a CE amplifier while Q2 works as a CC amplifier. For which the two drive signals of the power mosfet are quite different.
Look a little harder - both Q1 & Q2 are correctly polarized and are driving the appropriate LatFET from the collector and receive the feedback to emitter, so both work in Common Emitter mode.


Quote:
Originally Posted by mos57 View Post
Then, what is the purpose of using the network formed by R12, R13, C4, D1?
I'm afraid that not understanding that one disqualifies you as a critic, but here it is:
R12/R13 create a voltage divider which central point is held stiff at 12V (half PS voltage) with C4 which filters the residual ripple from the rail and that is the voltage set through R14 to the bases of Q1/Q2 and through the feedback network to the drains of LatFETs. R14 predominantly determines the Zin of the amp (since the base currents of Q1/Q2 are very low) and D1 takes care of C4's discharge.

Build a quick prototype and be amazed how nice it works...

Last edited by juma; 1st May 2014 at 10:18 PM.
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Old 2nd May 2014, 02:22 AM   #15
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John Linsley Hood designed a nice 10 watt amp. I have heard a diy version - sounded very nice indeed.
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Old 2nd May 2014, 02:49 AM   #16
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Quote:
Originally Posted by hazard500 View Post
John Linsley Hood designed a nice 10 watt amp. I have heard a diy version - sounded very nice indeed.
I'm already presently working on a JLH, the one from Silicon Ray with dual rail voltage.

For fun, so far it looks like this.

Eric
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Old 2nd May 2014, 10:12 PM   #17
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Quote:
Originally Posted by juma View Post
So, it's a single rail 24V power supply, clean 5W cl. A amp that you want - Laterals at the output, different sounding than ACA, right ?
Hi Juma,

Since this is your design, how did you built it..via perforated board, PCB or p2p. Just wondering if a PCB already exist for your design.

Is there an existing PCB for another project that has similar amplifier topology.

Thanks,
Eric
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Old 2nd May 2014, 11:21 PM   #18
juma is offline juma  Germany
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Here is the PCB I made for this amp - 46 x 57mm, copper side view.
It has provisions for bandwidth limiting caps in the feedback network and input LP filter cap (both in case of oscillations which didn't happen).
Output cap (10mF) is made out of 2 x 4700uF caps connected in parallel.
Input cap discharge resistor (220k) is placed on the input RCA connectors and the output cap discharge resistor (1k) is soldered on speaker terminals.
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Old 2nd May 2014, 11:54 PM   #19
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Thanks a lot !

The last PCB I built from scratch (small amp) was back 25 years ago, time to get to work ;-) this will be fun.
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Old 3rd May 2014, 01:51 AM   #20
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Hi Juma,

On your schematic (post no.8), R14 (47k) is connected on the left side of R18 (junction of C5).

On your PCB layout, I believe R14 is connected on the right side of R18.

Should R14 be connected to the left or right side of R18, does it make a difference ?

Thank you for your help.

Eric
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