SY35 Low headphone output

Covering the SY22 to SY55 and TG Modules.

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SY35 Low headphone output

Unread post by bobbyphonic » Tue Sep 20, 2016 5:34 pm

Hello everyone,

I just picked up an SY35 the other week and I love it. But more than that, my girlfriend loves it. The one issue with it, however, is that I have the volume 100% cranked and it still doesn't seem especially loud to me.

I've read up a little bit about other output issues, and I'm guessing it might be related to a faulty capacitor. I did the "relay check" and it does sound like the relay is clicking on properly. I'm interested in opening it up and replacing any faulty parts, but my girlfriend has already expressed that she will kill me if I screw anything up. (I have a gigantic dead Casio CZ1 with a fried board in the corner of the room that she reminds me of occasionally). So if I am going to go through with this, I was hoping anyone on the board might have some advice.

To summarize: Low volume output through the headphone jack even when turned up 100%. Low output through the L and R outputs as well.

Thank you,
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Joined: Wed Dec 07, 2011 6:00 pm
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Re: SY35 Low headphone output

Unread post by SiriusHardware » Thu Oct 27, 2016 8:02 pm

Before we get started can I ask by what means you have decided that the line level outputs, as well as the headphone outputs, are low? Measuring with a scope, or...?

The inputs to the headphone amplifier AND to the line level outputs comes from two voltage-controlled amplifier ICs. The volume control takes a DC reference voltage generated by one of these two ICs and feeds a portion of that voltage back to both of the voltage-controlled amplifers to tell them 'how loud to be'.

This is why I'm asking if - and how - you are sure that the line level outputs are low as well. If they are you can rule out any fault in the headphone amplifier, but if it's only the headphone output which is low then you'd be looking for a fault with or around the headphone amplifier circuit only.

If the line level outputs are really low then maybe you need to look at the reference voltage on the 'top' end of the volume control to see what that is.
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