Winbond ISD2560 - playback quality?

[ethrbunny]

Has anyone experimented with the various phrase recorders from this board? I built the Gurutzeta model and have it down to one bug. The record / playback is great but there is a background noise present. Its not static but something more regular. It varies with the playback volume level and is not present when the circuit is in 'record' mode or 'bypass'.

Im wondering if its a 60hz. Lacking a 'scope I can only guess.

In discussions about these chips its always been said that playback quality is less than perfect... so... how far from perfect is it? How much background noise should I expect? Where is the quality loss and what level?

[ethrbunny]

(cont'd)

I used an audioprobe to work on this. Both pin 14 and 15 (differential speaker) output have this problem 'hum'. I checked the 'in' and its ok. The chip appears to be well and truly grounded.

Id love to hear suggestions on how to track down this problem.

datasheet

[Sic]

i remember reading about the power supply being very important due to the digital and analog grounds, the loopy by dean hazelwanter is based off of the same chip but uses different caps coming from the 7805 to ground... maybe changing those to a different value might help?

i don't really know what im talking about, so bear with me if i don't make sense... i'm just giving my input from things that i have read

[ethrbunny]

Hmm.. my 5v line is grounded the same way as the "loopy". My electrolytics are properly oriented. I don't have a 1n4005 from gnd to +9V though. Guess its worth a try.