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Author Topic: Original A/DA Flanger - distortion in modulation signal chain  (Read 1195 times)

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JoeB

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Hi,

I am trying to determine why I have a signal distortion in the modulation side of my flanger. It's very scratchy - not unlike dust under a record needle.  The potentiometers are all fine, the threshold works correctly and the enhance pot range defines correctly how much modulated signal is combined with the dry signal. i.e. distortion increases with rotation of enhance pot.

The dry signal appears for all intents and purposes to be free of distortion.

I have tested this into three amps - a vox NT15 night train into vintage marshall 1960 cab ( G12 55hz greenback) 65 fender twin reverb and a 75 JC-120

The vox is delivering the most noticeable distortion - despit it being setup clean with low gain. yet swap the flanger out for my MXR m117 flanger (same 18v supply) and the signal is cleaner on both bypass and modulation.

So I need to look into the gain stages of the flanger and the modulation side to understand how the signal is  getting so hot on the wet side.

the enhance pot sweep makes no difference on the twin or the JC, but again on the vox the mix obviously increases distortion levels.

Now, before you all run around saying 'it's the amp', believe me when I say it's not. I have a hotter signal going in from a hudson broadcast and a boss BD-2 and they do not break up until I really flog the strings.

the distortion on the flanger is breaking up with the least pick attack possible.

I do have a scope, can trace, but need some values to work with. I have no idea what signal level measurements I should be expecting.

Can anyone help?

Unit Serial # is 223128 has µa723cn v.reg and reticon SAD1024Y BBD.

I notice more than a few tantalum caps on the board as well as the electrolytics, but none are showing signs of failure or leakage.

To make my life simpler, I have swapped the power input jack to a 2.1mm centre negative for testing.

I am feeding it with 18v from a GigRig doubler (gigrig power supply for pedalboard) so I'm relatively comfortable that the PSU is capable of delivering the required voltage for the flanger - unless there is some serious kind of current requirement I am not aware of.
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MarshallJMP

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Send me an email I might have some stuff for you.

Also did you check the bias of the SAD1024?

Also if you can get rid of those tantalum caps, they are crap!!
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JoeB

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I'll email you in a minute. Yes, agree on the tanties, and the electrolytics all look OK, but I'm sure they could benefit from replacement, simply due to age.

Ever had issues with the film caps?

Thanks for the assistance.
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MarshallJMP

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Not with film caps, tantas more then I wish fore  ;D and electrolytics, it can never heard to replace them.

BTW didn't got an email from you?
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JoeB

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Not with film caps, tantas more then I wish fore  ;D and electrolytics, it can never heard to replace them.

BTW didn't got an email from you?

I will send you a PM instead. Perhaps my email went to your spam (via board email)

I have emailed ADA and no response from support.
« Last Edit: Time Format by JoeB »
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MarshallJMP

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Got you r PM and emailed you back.
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