SH-101 Mains Hum

[gowans]

thanks for the replies. the adapter looks a bit like the image in the link, it has a voltage selector on the front of it; a little red dial you twist round. http://www.maplin.co.uk/ac-dc-multi-vol ... supply-226

i'm gonna get some batteries today and see if that eliminates the problem, all my faders are down and the lfo isnt routed to anything its just a constant lfo high pitch whining noise. i'll get back to you guys asap, failing that if nothing else works it looks like im gonna have to send this off to some kind of servicing company. i'm based in the north east, sunderland area, if anyone knows anyone round here that would be great, thanks for the offer lem but cornwall is like another country away!

[oblioblioblio]

I think the easiest way to tell the difference between old style linear PSUs and switch mode is by weight, but it's good info to be able to know by the markings.

I think you can get linear PSUs, I've got a feeling I got one built in europe with a soundcard that I bought recently, it's way too heavy to be switching. I also got one that was built about 10 years ago but it has since been discontinued.

Switch mode PSUs have come on a long way and they seem to be getting mentioned quite a lot on the muffwiggler forum, but I'm personally sceptical. They're good for microwaves and laptops but I'm not sure about them in audio devices. They just cut up the power and put loads of square wave random harmonics everywhere. The new TipTop audio power supplies are switch mode using heavy filtering. The Metasonix R series modules have little switching components built into the module themselves to get the right voltage to drive the tubes.

[Geeky as fck OT.]

[oblioblioblio]

i'm gonna get some batteries today and see if that eliminates the problem, all my faders are down and the lfo isnt routed to anything its just a constant lfo high pitch whining noise. i'll get back to you guys asap, failing that if nothing else works it looks like im gonna have to send this off to some kind of servicing company. i'm based in the north east, sunderland area, if anyone knows anyone round here that would be great, thanks for the offer lem but cornwall is like another country away!

If you route the LFO to control something does it work like an LFO?

It could be that the LFO is somehow running at audio rate, and it's possible that the voltage from the LFO bleeds onto the audio output a tiny amount, but normally you don't notice it becuase it's running below audio frequencies?

[steevio]

thanks for the replies. the adapter looks a bit like the image in the link, it has a voltage selector on the front of it; a little red dial you twist round. http://www.maplin.co.uk/ac-dc-multi-vol ... supply-226

i'm gonna get some batteries today and see if that eliminates the problem, all my faders are down and the lfo isnt routed to anything its just a constant lfo high pitch whining noise. i'll get back to you guys asap, failing that if nothing else works it looks like im gonna have to send this off to some kind of servicing company. i'm based in the north east, sunderland area, if anyone knows anyone round here that would be great, thanks for the offer lem but cornwall is like another country away!

no way, i'm from Sunderland, are you are Mackem ?

that PSU link you sent looks like it might not be big enough.

the ones i use are 13W, but i'm not sure what power rating the SH101 is, you should be able to Google that.

it looks like a cheap and nasty jobby to me.

if it turns out that its the machine itself, i have a mate who fixes synths, he's really good and cheap, fixed loads of stuff for me, but i'm based in Wales now. if you're not in a hurry i could pick it up next time i'm up to visit my folks which will be quite soon.

what i definitely wouldnt do is send it to a servicing company by post or courier, SH101s dont travel well thrown in the back of transit vans, and it will probaly cost you alot of money.

[lem]

Lots of audio chips work fine at different voltages. You can run lots of modules designed for +/-15v at +/-12v and not damage anything, but it can fck with the calibration and other stuff.

But yeah, I think poor PSUs can easily introduce noise and instabilities.

I was getting at the instabilities, its more relevant to the issue i think. but also I was trying to sway people from reading this and trying it. Fiddling is a great way to learn but power supplies shouldn't be messed with like that.

Audio chips may be fine, but cpu's and logic stuff can be really sensitive. I am just pointing out best practice.

[oblioblioblio]

I was getting at the instabilities, its more relevant to the issue i think. but also I was trying to sway people from reading this and trying it. Fiddling is a great way to learn but power supplies shouldn't be messed with like that.

Audio chips may be fine, but cpu's and logic stuff can be really sensitive. I am just pointing out best practice.

yeah i'd agree with that, especilly on old synths no longer in production with hard to find components.

speaking of which steevio did you ever get those replacement parts for your sh101 from Technology Transplant?

[gowans]

i'm from seaham mate! i'd class myself as a mackem. i'd be up for doing that if it turns out to be a bigger problem, im gonna pop out now and see if i can get a better PSU, and some batteries. thanks for the help!!

[gowans]

okay i just went out and bought 6 x C size duracell batteries. tried them and it wont power up from the batteries, works fine from the adapter though