SYMEF amplifier

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#1,002
#1,003
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#1,004
Hi Thimios,

In the history of SYMEF there was drowranger 🙂

http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-14.html#post2793180

http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-17.html#post2888180

http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-22.html#post2907482

http://www.diyaudio.com/forums/solid-state/198500-symef-amplifier-25.html#post2912452

kind regards,

Harrison.

thimios said:
Thanks for instant replay .
Is it possible to guide me for pcb ?
Which version can i use?
Where can i find it?
I want to etch my own if it's possible to give me the pdf.
If this impossible i can buy it but from where?
Best regards.
Thimios.
Click to expand...
 
#1,005
 
#1,013
Working on it. I had to order a selection of new resistors as some of the values you specify in the E24 series I somehow simply don't have on hand 😱

Also, is there a drill template and lead bending radius recommendation available? That would make life easier when prepping the heat sink. If there isn't then I'll just put some easy 'standard' radius bend on the leads and measure.
 
#1,014
jkuetemann said:
Working on it. I had to order a selection of new resistors as some of the values you specify in the E24 series I somehow simply don't have on hand 😱
Click to expand...
Thanks for the update Jason. 🙂
jkuetemann said:
If there isn't then I'll just put some easy 'standard' radius bend on the leads and measure.
Click to expand...
There are several ways to tackle the build. Am looking forward to how each member goes about it 😎

kind regards,

Harrison.
 
#1,015
Here is the first mostly stuffed board, just a few items I forgot to get from the local purveyor of electronica.

sunyre9a.jpg
 
#1,017
OK, got the first channel powered up, but not without some minor issue.

One issue I was concerned about directly from the schematic reared its head immediately - a low level (1.8V p-p) HF oscillation at about 7.2MHz. I thought the shunt compensation was a little dubious and ended up having to add miller capacitors to the VAS. Having said that, the issue could have been self induced since I chose (read as had on hand) substantially faster transistors for the drivers and pre-drivers than specified.

Offset was fairly low at about 12mV and noise levels seem to be quite low, we'll see how low when it makes it to my speakers to have a listen.

A few comments about the 'Type 2' design:

1) It is, let's say, interesting to assemble, I spent a fair bit of time measuring and laying out a template in a 2D CAD program to get the drilling accurately done. A bit of a pain if no template is provided.

2) The under board mounting of devices will make alterations / repairs a real pain in the @$$, likely to the point of trashing it if a failure occurs that cant be addressed from the component side.

3) Some holes are so close to one another that I inadvertently allowed solder to flow into holes not yet occupied when stuffing the board. Not a big issue, just something to be aware of.

I will be removing it from the limited supply and giving it a full warm-up shortly to finalize the bias setting, then on to some more serious loading. I will attempt to induce the undesired parasitic oscillation during testing before turning it loose on my system. I'll be curious to hear it against my PeeCeeBee VSSA and the official LC VSSA, amongst a few commercial offerings too.

Will post more as I learn more.
 
#1,020
Very nice Jason 😀. Looking good, the faster transistors may have caused it? Tekko may also have had such an experience. His solution was to terminate c3 and c9 across q1 q17 bases and collectors 😎

You did such a great job with the template am shipping your 2 free 1DIFFQC PCBs.

Looking forward to your review.

kind regards,

Harrison.
 
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