Quadrasynth Plus Piano headphone hiss expectation?

[exmachina]

Hi all,

Picked up a QSPP dirt cheap with a SKB case and am enjoying it. Noticed that in the headphones output (but NOT the main outs) there's a fair amount of steady-state hiss even with the volume turned down -- is this normal?

Additionally my synth outputs a bit of hum and noise even when the unit is turned off. I've addressed this by lifting the ground with an adapter and now the stereo main outs are as clean as a whistle. Not at all sure what this indicates, but at least I can record with it.

Lastly, my value decrement switch is nonresponsive. I've been working around it but figure at some point on taking it part and cleaning the area -- has anyone done this before and have any tips to share?

Thanks!

[Jokeyman123]

Can't help with disassembly, I'm sure there are google hits showing somebody disassembling and repairing this Quadrasynth. If its just a "clicky" contact switch-the najor work might be getting the board out, since the contril IC boards are sometimes buries behind other boards. as far as hiss with headphones-have you tried a few different headsets? Might be an impedance mismatch, some synths/digital pianos/workstations are picky about which headphones will work/sound OK. I've had good matchups with the Superlux series, and I also use AKG's. ground hum-if you lifte the ground and it disappeared, check other AC outlets-your outlet might be wired incorrectly, or not grounded. some duplex outlets may have 3 prongs, but the electricians don't always connect the grounds in the box!

[parametric]

If the QS has been stored in an electronics-unfriendly environment (Loft or Garage) for any length of time, then socketry

can become tarnished.

Try plugging/unplugging the Phones rapidly a number of times and see if it improves?

More effective cleaning will require access to the pcb the socket is mounted on. Check the solder points and re-melt

if appropriate, and clean the contacts with IPA (IsoPropyl Alcohol) and cotton buds . . .

May be worth checking any earth straps from the PCB(s) to the Metal? Case while you're there.

If these are bolted to the Case - undo the bolts and re-tighten, to refresh the connection . . .

perhaps that helps?

parametric

[toofpate]

I had a QSPP and there is normally a lot of noise on the headphone jack - same on the S4+ I am trying to fix now.
In the manual it's said this is a digital signal path and to run the volume as high as possible to get best S/N, turning the vol down leaves a LOT of hiss on sensitive phones.

For the QSPP I got a cheap little inline volume control, run the vol sort of high and trim it down with the control, worked quite well.

[Jesse]

I had a QSPP and there is normally a lot of noise on the headphone jack - same on the S4+ I am trying to fix now.
In the manual it's said this is a digital signal path and to run the volume as high as possible to get best S/N, turning the vol down leaves a LOT of hiss on sensitive phones.

For the QSPP I got a cheap little inline volume control, run the vol sort of high and trim it down with the control, worked quite well.

Nice, thanks for sharing that information

[mariusvideo76]

Hi all!

I have two (wonderful) Quadrasynth, not the Plus, both from 1994, they are noisy for nature but one of the two is less noisy than the other.

In the quiter of the two I can ear only a white noise but on the second one I can ear the white noise and a sort of very light "huiiiiiiiuuuuuiiiiuuu" in the background on some of the sound when I play some notes, It's audible on the ending of the sound when the sound decreases...
the issue is not on all sounds, I think may be the audio FX section that produces this sound because the noise i present on the sounds with a lot of reverb...

I have tried to change all the capacitors around the audio outputs & Co, changed the 2 dacs, the opamp that supply the power to headphones etc... have changed the FX processor too (I have a mainboard to pick the components)...the last thing is to change 3 o 4 little transistor in the audio chain....but at this moment the result is that the noise is there...I think is native issue of the first model of quadrasynth...

[exmachina]

Thanks, all appreciate the input and your experiences. I've yet to take it apart to try to fix the button problem but when I do I'll also reseat all the connectors, any socketed chips and tighten down screws. It doesn't really bother me that the headphones output is hissy since I'm generally monitoring off my audio interface, anyway. Thanks again!