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Old 23rd March 2013, 12:54 PM   #3901
AndrewT is offline AndrewT  Scotland
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It would be better to ask the output impedance and how it varies over the audio band.

Would it matter if the 1kHz Zout were 50mr or 70mr or 87mr?
Would it matter that the 100Hz Zout were 3 times the 1kHz value?

What are you going to use these Zout values for?
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Old 23rd March 2013, 12:56 PM   #3902
highand is offline highand  Hungary
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bittner damping.jpg
Quote:
Originally Posted by mikelm View Post
Damping factor is dependent upon load impedance.

If you don't specify this your question cannot be answered accurately.
The calculation is calculated on a 1 ohm. The picture shows the output impedance. The correct damping factor calculation was divided into 4 ohms, 4, 8 ohms divided by 8, ect, ect. and calculate the inverse.

Last edited by highand; 23rd March 2013 at 01:03 PM.
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Old 23rd March 2013, 02:05 PM   #3903
Ryssen is offline Ryssen  Sweden
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Quote:
What are you going to use these Zout values for?
Just thought Id compare it with the F6 amp (That has 16 in damping factor)
quite a difference from the symasym.
I use the symsym to drive the bas/mid in a biamped 2 vay,Is that going to affect the sounf much?
I guess I could have waited until I built the F6 and try...
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Old 20th July 2013, 05:46 AM   #3904
triast is offline triast  Indonesia
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Is there any recomended PSU for this amp? The simple one please...
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Old 20th July 2013, 06:06 PM   #3905
jaycee is online now jaycee  United Kingdom
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It only requires a basic unregulated power supply as most solid state power amplifier circuits use.

In this case use a 2x25VAC or 25-0-25VAC transformer of at least 200VA for a stereo pair, a bridge rectifier and say 2x4700uF 50V per rail to produce a +/-35v supply. Use more capacitance if you like but I find the above gives good performance.
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Old 22nd September 2013, 05:47 PM   #3906
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Hello,what modification's i need to make to the amp if i want to put another pair of mjl and my power suply is +- 56vd dc(2x56v dc),i made some schematics to see if they are good or not,thank you !
http://http://tinypic.com/view.php?p...5#.Uj8sZYa9WWc

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Old 23rd September 2013, 11:09 PM   #3907
00940 is offline 00940  Belgium
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I built a symasym some years back and I'm considering building another.

I thought I'd change some little things on the original PCB before starting (change the trimmer, remove the fuses, thicken some traces to make it easier to self-etch, etc.) and, one thing leading to another, I ended up in Eagle with a quite different PCB.

So, here it is. Does it seem ok or should I go back to the original one ?
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Old 24th September 2013, 06:53 AM   #3908
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It is not the best. e.g. R29 should be connected at the jumper so also R7.
The jumper was replaced with a thick wire which improved the performance. It is in the thead somewhere. BOL

Gajanan Phadte
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Old 24th September 2013, 07:39 AM   #3909
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The ground pins of C10 and C11 should be as close to the ground connector as possible. You've put them as far from it as you can.

Why not put the reservoir caps along the space behind the power transistors? This would take the small-signal circuitry out of the magnetic loop and decrease radiated distortion. Power ground wouldn't be at the other side of the board so you wouldn't need to run the power output trace through the small-signal section.
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Old 24th September 2013, 09:16 AM   #3910
00940 is offline 00940  Belgium
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Thank you for the comments... there's much work on my plate after that.

Some questions in order to clarify things in my mind.

Quote:
Originally Posted by gmphadte View Post
It is not the best. e.g. R29 should be connected at the jumper so also R7.
The jumper was replaced with a thick wire which improved the performance.
- What's the problem about R7and R29 ? This part is coming straight from the original layout.
- I had some trouble understanding what you pointed to, as I deleted that jumper by running ground tracks left and right... and then I remembered that the evolution in between 5.2 and 5.3 was precisely the opposite

Quote:
Originally Posted by keantoken View Post
The ground pins of C10 and C11 should be as close to the ground connector as possible. You've put them as far from it as you can.

Why not put the reservoir caps along the space behind the power transistors? This would take the small-signal circuitry out of the magnetic loop and decrease radiated distortion. Power ground wouldn't be at the other side of the board so you wouldn't need to run the power output trace through the small-signal section.
- Well, it was kinda on purpose. C10 and C11 are the reservoir for the small signal circuitry. If I put them close to the ground connector, they'll be connected before the power reservoir caps and see all the charging currents. In a ground bus, isn't it better to have the sensitive circuitry after the big stuff ? Or am I missing a step ?
- I like the idea a lot, especially wrt the magnetic loop.
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