Hello everyone!
A few days ago i was lucky enough to get an Ibanez AD 80 for a pretty good price. It just seems to have a little problem: When i turn up the delaytime beyond three o'clock, i hear a strange whistling that comes with the delay repeats. It's very high pitched and gets even louder when i turn it all the way up. It's subtle but it's there, and i have to keep the delay time before three to avoid it.
I turned the internal clock-trimpot all the way back and it improved things a bit, but the noise is still there. i assume it's clock noise.
My idea is that one of the caps in the filter circuit, that is supposed to filter the frequency out must be broken. Looking at the schematic it must be one of the following:
C111, C112, C113, C118, C119, C120, C121, C122, C123.
here's the schematic:
http://www.sonicurbs.com/ibanezAD-80/ibanezad80.pdf
These caps are located right before and after the MN3005 BBD. From what i've found out there is a mechanism that boosts the frequencies where the noise is before the signal enters the BBD and attenuates the frequencies again afterwards, to improve the signal to noise ratio and to cut off some high end. I am not an expert on reading schematics but the caps i listed above seem to be part of that mechanism, right? Can someone confirm that replacing these one by one might solve the problem?
Still i am wondering if this noise is normal and i am just listening too critically. Is here anyone who owns one of these and also hears this whistling on high delay times?
Thanks for advice!
Ibanez - AD-80 Analog Delay - clock noise [schematic]
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Dirk_Hendrik
- Old Solderhand
Information
I know the complaint but yes, I consider it normal. The AD80, as well as many other pedals, are not hifi designs.
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mictester
- Old Solderhand
Information
[quote="ralf"] Can someone confirm that replacing these one by one might solve the problem?
quote]
You're very unlikely to affect the problem by "poke and hope" methods like that!
You are being too critical - there's clock noise on every one of these I've seen. Some are worse than others - the board layout was pretty poor for a product from that company. Make sure that C117 is OK - I've found it poorly soldered - and that can introduce some strange noises.
If the noise really annoys you, sell the thing on Ebay!
quote]
You're very unlikely to affect the problem by "poke and hope" methods like that!
You are being too critical - there's clock noise on every one of these I've seen. Some are worse than others - the board layout was pretty poor for a product from that company. Make sure that C117 is OK - I've found it poorly soldered - and that can introduce some strange noises.
If the noise really annoys you, sell the thing on Ebay!
"Why is it humming?" "Because it doesn't know the words!"
Thanks for the replies. I think i figured the problem out.
Trying around with the trimpots i noticed that the balance trimpot has an effect on this high pitched frequency that came along with the repeats. By carefully adjusting it while listening to the repeats i could find a point where the noise was pretty much eliminated.
Looking at the schematic and the mn3005 datasheet it seems like the balance trimpot adjusts the balance between the two output signals of the mn3005. Maybe the signals are out of phase and meant to cancel this noise out. I don't know, but it worked.
By the way: trying around with the other trimpots i found out that a distorted signal can be caused by the bias trimpot being set wrong. It kind of adjusts the signal range and clips peaks.
I'm happy i tried these pots before i ripped the guts out of this great pedal.
Trying around with the trimpots i noticed that the balance trimpot has an effect on this high pitched frequency that came along with the repeats. By carefully adjusting it while listening to the repeats i could find a point where the noise was pretty much eliminated.
Looking at the schematic and the mn3005 datasheet it seems like the balance trimpot adjusts the balance between the two output signals of the mn3005. Maybe the signals are out of phase and meant to cancel this noise out. I don't know, but it worked.
By the way: trying around with the other trimpots i found out that a distorted signal can be caused by the bias trimpot being set wrong. It kind of adjusts the signal range and clips peaks.
I'm happy i tried these pots before i ripped the guts out of this great pedal.