Mockingboard Sound Quality [message #388690] |
Tue, 12 November 2019 11:02 |
Vince Weaver
Messages: 136 Registered: April 2013
Karma: 0
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Senior Member |
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Hello
so I was at Demosplash showing off a new Apple II demo (I'll post it
eventually, there are a few bugs I need to sort out first).
Anyway though, I was once again disappointed by the sound quality of
the Mockingboard compared to other AY-3-8910 based hardware. Especially
the bass notes.
I think this is a hardware issue, as things sound fine in emulators.
And it's not on the actual AY chip as my Raspberry Pi AY player (with
actual AY chips) sounds fine too.
So the output amplifier on the Mockingboard, does anyone know how
high quality it is? I know 386 amplifiers are pretty low-end. Is there
a high-pass filter on the output that might be cutting out the bass notes?
I'm just wondering if I can pop out the 386 chips and hook up some
circuitry to get either a line out, or else maybe pass in to a better
amplifier (my pi based player uses some cheap class-D amps which seem to
work OK).
Vince
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Re: Mockingboard Sound Quality [message #388733 is a reply to message #388690] |
Tue, 12 November 2019 19:53 |
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Originally posted by: Frank M.
Probably not the LM386. They are common in guitar amps and pedals as a preamp and have a flat frequency response.
There are some 10 or 15uf capacitors in series after the AY, before the amps, that are (probably?) acting as a filter. I'm no expert though. Michael Mahon?
You can also take audio directly from pins 3 and 4 of the AY and feed your own EQ and amp.
f
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Re: Mockingboard Sound Quality [message #388761 is a reply to message #388733] |
Wed, 13 November 2019 18:20 |
Michael J. Mahon
Messages: 1767 Registered: October 2012
Karma: 0
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Senior Member |
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Frank M. <frank_o_rama@hotmail.com> wrote:
> Probably not the LM386. They are common in guitar amps and pedals as a
> preamp and have a flat frequency response.
>
> There are some 10 or 15uf capacitors in series after the AY, before the
> amps, that are (probably?) acting as a filter. I'm no expert though. Michael Mahon?
>
> You can also take audio directly from pins 3 and 4 of the AY and feed your own EQ and amp.
>
> f
>
I agree with you, Frank—it’s not the 386, it’s the coupling capacitors.
Get it generating a, say, 60Hz squarewave and take a look at the output
with an oscilloscope. For good low frequency response, you shouldn’t see
much “sag” in the squarewave. This test should be done with the output
loaded (as you’re using it) and unloaded, to see what effect the load is
having.
Poor low frequency response can result from using the card to drive a low
impedance load, like a speaker or even headphones. Try using the card to
drive a line-level input to an external amplifier (line input impedances
are typically 10k Ohms or greater).
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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