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StuBrew
Copper Member
United Kingdom
4 Posts |
 Posted - 03/21/2010 : 18:30:46
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Hi everyone, having a few problems with my DM-2.
Firstly the repeats are distorted and there is a high pitched noise on longer repeats. On shorter repeats its fine.
Im pretty sure it could be fixed using the 3 trim pots inside but haven't got a clue where to start!
Any ideas would be much appreciated!
Cheers,
Stu |
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Dirk_Hendrik
Copper Member
Netherlands
28 Posts |
Posted - 03/21/2010 : 18:38:29
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| Start off with a medium delay time (without the whine, no feedback, and adjust the bias trimmer for clean repeats. Then adjsut the delay time control trimmer with delay time knob on max for longest delaytime without whine. |
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StuBrew
Copper Member
United Kingdom
4 Posts |
Posted - 03/21/2010 : 22:19:25
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| Thanks, I'll give it a go! |
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StuBrew
Copper Member
United Kingdom
4 Posts |
Posted - 03/21/2010 : 23:01:08
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| Ok, I THINK that worked. Ive had to sacrifice some of delay time to get rid of the high pitched whine and the repeats re still ever so slightly distorted but its much improved, thanks! |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/22/2010 : 00:26:49
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quote:
Originally posted by StuBrew
Ive had to sacrifice some of delay time to get rid of the high pitched whine and the repeats re still ever so slightly distorted
That's completely standard. The delay on those pedals is meant to be short (300 ms). Plus the slight distortion is part of the analogue charm... 
PS: welcome! Stick around and tell us about yourself and you rig! |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 03/22/2010 : 02:09:19
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Could it be that the distortion comes from overdriving the pedal input ?
I've noticed that just before the BBD chip there is an op-amp with back-to-back diodes in the feedback path, similar to the ones used in overdrives.
This is probably used as a protection but if the input signal is too hot it will produce distortion for sure. |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 03/22/2010 : 12:42:49
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quote:
Originally posted by cctsim
Could it be that the distortion comes from overdriving the pedal input ?
I've noticed that just before the BBD chip there is an op-amp with back-to-back diodes in the feedback path, similar to the ones used in overdrives.
This is probably used as a protection but if the input signal is too hot it will produce distortion for sure.
Which diodes are you seeing? Counted all five and none are in any feedback. Same with the DM3.
Tho I do know what diodes your referring to, they're found in the old chorus and flangers. Used as a crude limiter for recycling the mixed signal so it doesn't overload the next op amp. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 03/22/2010 : 14:20:39
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quote:
Originally posted by ChristoMephisto
quote:
Originally posted by cctsim
Could it be that the distortion comes from overdriving the pedal input ?
I've noticed that just before the BBD chip there is an op-amp with back-to-back diodes in the feedback path, similar to the ones used in overdrives.
This is probably used as a protection but if the input signal is too hot it will produce distortion for sure.
Which diodes are you seeing? Counted all five and none are in any feedback. Same with the DM3.
Tho I do know what diodes your referring to, they're found in the old chorus and flangers. Used as a crude limiter for recycling the mixed signal so it doesn't overload the next op amp.
You are right, I was looking at the wrong schematic (BF-2), apologies.
The DM-2 uses a compander chip (IC2, NE570) for limiting the input.
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chris101
Copper Member
United Kingdom
3 Posts |
Posted - 03/23/2010 : 21:49:50
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| All DM-2s seem to have a slight distortion to the repeats, its a kind of metallic chime as the note fades, most noticable when the delay time is set to maximum. |
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Roger
Bronze Member
USA
81 Posts |
Posted - 03/28/2010 : 08:30:23
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quote:
Originally posted by chris101
All DM-2s seem to have a slight distortion to the repeats, its a kind of metallic chime as the note fades, most noticable when the delay time is set to maximum.
I have to say...that describes mine exactly. I've thought about adjusting the T-Pots but haven't had the courage to mess with them yet. Does it really work? Can you really/ totally get rid of the metallic chime at max delay time? |
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Topic |
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DM-2 Distorted repeats and high pitched whine
