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D.I.Y. amp

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Re: D.I.Y. amp

Postby Folderol » Mon Jun 22, 2020 4:13 pm

That's not a bad idea. Now why didn't I think of that? :clap:
I've got various bits of Linux audio analysing software, and I can use my trusty KA6 into my laptop to actually make the recording.
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Re: D.I.Y. amp

Postby Martin Walker » Mon Jun 22, 2020 10:33 pm

ef37a wrote:Will, have you tried recording the output, you only need a 5 sec burst, then putting the signal through Right Mark Analyser?

I used to use RMA a lot during my SOS audio interface reviews, and it invariably worked very well for distortion and frequency response tests.


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Re: D.I.Y. amp

Postby ef37a » Tue Jun 23, 2020 7:06 am

Martin Walker wrote:
ef37a wrote:Will, have you tried recording the output, you only need a 5 sec burst, then putting the signal through Right Mark Analyser?

I used to use RMA a lot during my SOS audio interface reviews, and it invariably worked very well for distortion and frequency response tests.


Martin

Have you fired it up recently Martin? I ask because I am sure there was a 'save' icon (floppy disc pic?) when you had the RTA graph up? Can no longer find it and have to do a prntscr.

Or am I just going daft in m OA?

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Re: D.I.Y. amp

Postby Martin Walker » Tue Jun 23, 2020 4:20 pm

ef37a wrote:Have you fired it up recently Martin? I ask because I am sure there was a 'save' icon (floppy disc pic?) when you had the RTA graph up? Can no longer find it and have to do a prntscr.

Or am I just going daft in m OA?

No, you're not going daft - I've just fired it up for you, and there is most definitely a save icon (I've got the cursor hovering over it in this screenshot):

RMAA.jpg



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Re: D.I.Y. amp

Postby Folderol » Sun Jun 28, 2020 7:58 pm

OK, done some more checks with a Linux equivalent :tongue: and the results are good. I mentioned that low level results are hidden in the hum and noise, but what I hadn't realised was that this is also lower - not due to the amp, but because of the work I did some time ago on the signal generator, combined with my home electrically supply being 'quieter' than my old employer's workshop! Anyway, at 1W there is about 6dB improvement. A short burst at 50W is giving pretty much identical results as before, so it suggest that it's the output transistor stage that is responsible for this.

When comparing the figures, I had a 'DOH' moment - I was using exactly the same software method of measuring as before apart from actually recording a short bit of high level output :roll:

So with that, I'll order the necessary bits to do all three then take the amp out of service to do the work. I'll still be able to use the kit on headphones, as the M-Track 8 has a phones socket.

I also must give serious consideration to getting that front panel sorted out!
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Re: D.I.Y. amp

Postby Martin Walker » Mon Jun 29, 2020 9:15 pm

Folderol wrote:I also must give serious consideration to getting that front panel sorted out!

I always put off finishing my front panels, because ironically they can take as long as designing the circuit, but are a lot less fun to make. The panels themselves are fine - it's getting the control labels neat and tidy that takes all the time ;)


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