SAD1024A A/DA flanger - increasing headroom

[12Bass]

Hey Everyone!

I'm hoping for some ideas on how to increase the headroom on my A/DA flanger clone.  I've done some modifications to the design to open up the high frequency response, and it is sounding quite good, IMO.  However, the circuit seems to be clipping on the low notes of my 5-string bass.

So, there are a couple of paths I've been thinking of pursuing:  

One is to reduce the input gain slightly, and make the mixing resistors somewhat smaller to compensate.  This would raise the noise floor somewhat.  Another possibility is to put a simple high pass filter (a series capacitor, perhaps) inline with the input of the BBD, which would limit the low frequency content, hopefully reducing clipping to an acceptable level.  The latter approach shouldn't affect the noise floor, and would leave the low frequencies untouched by flanging, a change which might even be advantageous for bass applications.  Or maybe a bit of both approaches might work???

I've got some MN3007s around too, so that's another possibility.  However, my first test with an MN3007 daughterboard didn't sound near as good as the SAD1024A.  From what I recall, I heard flanging sounds, but it wasn't very clear.  Not sure if I got the implementation right with the Panasonic BBD, though....

Any thoughts or suggestions?

Thanks!

[StephenGiles]

Putting aside my view that a bass should be just that and not pretend to be lead guitar

You could try a few things:

1 - run the opamps off dual 15v power, leaving the BBD and clock stuff on +15v - probably requires other changes to the circuitry

2 - beef up the diode limiter on the input section

3 - build in a jolly old compander - sound will probably suffer

4 - try a "What" compressor style equaliser

But you need to establish the point at which clipping starts first and let us know.

[12Bass]

Thanks for the reply!

The majority of the clipping appears to be from the BBD path.  From what I can tell, the clean signal stays relatively clean unless the input is really pushed, so there seems to be enough headroom in the op amps when running at +15V.  A while ago I spent some time very carefully adjusting the BBD bias for minimum distortion.  Thus, my suspicion is that the output of my 5-string is simply a bit too much for the SAD1024A to handle without overloading.    

[StephenGiles]

Have you tried playing with the BBD bias trimmer in order to find the setting for least clipping? It would probably be easier to hear this with an ordinary guitar.

[Thomeeque]

Have you tried playing with the BBD bias trimmer in order to find the setting for least clipping?

..A while ago I spent some time very carefully adjusting the BBD bias for minimum distortion..

[StephenGiles]

Have you tried playing with the BBD bias trimmer in order to find the setting for least clipping?

..A while ago I spent some time very carefully adjusting the BBD bias for minimum distortion..

My goodness, I should have Czeched

[12Bass]

Actually, I fed a sine wave into the flanger and ended up at about 4.62V.  The optimal bias changed slightly depending on clock frequency, so it was adjusted to the point where there is minimum distortion across the entire delay range.  As far as I can tell, the BBD is doing the best it can.  My other basses aren't a problem unless I really dig in (Hamer 12-string and Rickenbacker 4001).  The Q-tuner in the Pedulla Rapture 5 must have a hotter output (by 6 dB or more).

BTW, what is a "What" compressor style equaliser?

[Thomeeque]

Another possibility is to put a simple high pass filter (a series capacitor, perhaps) inline with the input of the BBD, which would limit the low frequency content, hopefully reducing clipping to an acceptable level.  The latter approach shouldn't affect the noise floor, and would leave the low frequencies untouched by flanging, a change which might even be advantageous for bass applications.

I would say this is the way, but it won't be so simple, as adding the series capacitor inline with the input of the BBD would cut-off DC bias. However fix is relatively easy, you can restore the bias voltage at the BBD input by cca 100k resistor from the bias trimpot center (this resistor will form part of high pass RC filter as well - you should probably add cca 10-100uF capacitor between the bias trimpot center and ground yet, to make the bias trimpot center solid "ground" from AC point-of-view).

T.

[Thomeeque]

My goodness, I should have Czeched

You can still Czech your stash for those two documents I asked you for T.

[StephenGiles]

My goodness, I should have Czeched

You can still Czech your stash for those two documents I asked you for T.

http://www.film-tech.com/warehouse/manuals/SMARTSR330.pdf
http://www.film-tech.com/warehouse/manuals/KINTEKKT24.pdf

They work now!

[Thomeeque]

You can still Czech your stash for those two documents I asked you for T.

http://www.film-tech.com/warehouse/manuals/SMARTSR330.pdf
http://www.film-tech.com/warehouse/manuals/KINTEKKT24.pdf

They work now!

Wow, even now , thanks!! T.