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Old 21st January 2011, 12:06 PM   #1281
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In post #1193 I suggested to layout a PCB that comprises both the MONGREL AX frontend and the PB250 backend.

I did the layout myself.

Here it is:

Click the image to open in full size.

The dimension of the PCB is 235 x 125 mm.

I wonder if Pete likes / approves it.

Best regards - Rudi_Ratlos
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Old 21st January 2011, 12:48 PM   #1282
Macleod is offline Macleod  France
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Hello Pete,

Nice work you do.

Did you investigate the clipping behavior of the AX1.3? i just simulated it (as a background task at office) and see some nasty clip for 1.9V input. Seems that Q10 is saturated.

Hope this helps.

Impressive THD anyway!

regards

Laurent
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Old 21st January 2011, 01:01 PM   #1283
Macleod is offline Macleod  France
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Just found a quick and dirty work around : connect a diode between Q10 collector and Q9 base. Now it's ok. You can also have a smooth clip by adding a small serie resistors... that in fact only push away the hard clipping...
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Old 21st January 2011, 02:40 PM   #1284
Krisfr is offline Krisfr  United States
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Quote:
Originally Posted by Rudi_Ratlos View Post
In post #1193 I suggested to layout a PCB that comprises both the MONGREL AX frontend and the PB250 backend.

I did the layout myself.

Here it is:

Click the image to open in full size.

The dimension of the PCB is 235 x 125 mm.

I wonder if Pete likes / approves it.

Best regards - Rudi_Ratlos

Three Questions
1 Have you had a chance to listen to your build?
2 Are you willing to share it to Laser Printer Transfer Builders?
3 What PCB layout program did you use.

Excellent work by the way, keep it up, Looks Great...
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Old 21st January 2011, 04:57 PM   #1285
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Quote:
Originally Posted by Macleod View Post
Hello Pete,

Nice work you do.

Did you investigate the clipping behavior of the AX1.3? i just simulated it (as a background task at office) and see some nasty clip for 1.9V input. Seems that Q10 is saturated.

Hope this helps.

Impressive THD anyway!

regards

Laurent
Working on just that ! Cordell's VAS "active shunt" solves that problem (below 1). Also, the AX1.4 will be TMC / TPC /CMC ** universal. I did saturate Q10 on my 45v setup , It did not get warm or let magic smoke out , BUT ... replacing the Q9- 220R collector resistor with Cordell's transistor (A/Q3 - pix 1) is foolproof. If more than 13ma is passed by R19 , Q3 will shunt the base of Q9.

Also , the AX made a "tick" (small thump) ... this was because the VAS CCS stabilized before the input stage one did. Solved this by tying the 2 current sources together (B- pix 1). (Below 2 ) is the universal layout for the compensations , note "LC" and the 2 "TPC" pad groups.

I was told to make this circuit 110% , so be it.

"Impressive THD" , Yes at 40V p-p ..... at 80V still good. By using a 3Q wilson mirror at the input stage , I could achieve .4PPM @ 1k - 100V p-p. I am debating whether to do this for 2 reason's, #1 - the increased impedance of the wilson and #2 - how much more perfect does this have to be ?
Another decision is to whether to leave the cascode , a pair of 2sc1845's are plenty quiet by themselves.

** TMC= transitional miller compensation
TPC= two pole compensation
CMC= conventional miller compensation

Nice work, Rudi ... you might want to incorporate both "improvements" before you build.

OS
Attached Images
File Type: gif AX-V1.4.gif (101.9 KB, 338 views)
File Type: gif AX-V1.4pcb.gif (47.3 KB, 327 views)
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Last edited by ostripper; 21st January 2011 at 05:00 PM.
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Old 21st January 2011, 05:19 PM   #1286
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Quote:
Originally Posted by Krisfr View Post
Three Questions
1 Have you had a chance to listen to your build?
2 Are you willing to share it to Laser Printer Transfer Builders?
3 What PCB layout program did you use.

Excellent work by the way, keep it up, Looks Great...

1 - Yes - see below
2 - Yes
3 - I used EAGLE to layout OStripper's MONGREL

Comments:

1 - I need OStripper's "O.K." to offer my layout to the DIY community
2 - I want to incorporate the latest changes (see post of McLeod) in my layout
3 - I need a "guinea pig" to prototype my layout

I will not offer my layout until it has been proven by somebody.
I have already somebody in mind to do the prototyping.

I can't do this by myself, since I do not possess an oscillospe, a function generator, ...

For example, KRISFR:

The pinout of the KSA 2992, that OStripper uses, is different from the pinout of the 2SA992 my German distributor offers.
I want to be sure that my MONGREL layout works with the components that are currently distributed.

Have some patience, please.

Best regards - Rudi_Ratlos
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Old 22nd January 2011, 03:08 PM   #1287
nikko is offline nikko  Bosnia and Herzegovina
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Greetings from Bosnia,great amp,still waiting for the right box.
Psu is Apex,with protection.
Here are the pictures, sorry about bad english
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 22nd January 2011, 03:14 PM   #1288
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Hi Nikko, Great looking build!!! Thanks for sharing the pictures. How are you tinning the PCB? Thanks, Mark
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Old 22nd January 2011, 03:28 PM   #1289
nikko is offline nikko  Bosnia and Herzegovina
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Thank you for the compliments.Without some problems, of course manually.
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Old 22nd January 2011, 03:38 PM   #1290
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Quote:
Originally Posted by nikko View Post
Greetings from Bosnia,great amp,still waiting for the right box.
Psu is Apex,with protection.
Those ARE nice. This helps me alot.. Most builders like the 120 watt version , this is good , SO ... the "all in one version" will be a 4 device one (The one I will sell) GOOD job !!

Did you run them ??

OS
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