Tilt preamp

samhay · April 20, 2016, 07:23:23 AM

1590B stuffed to the gills.
The LEDs and associated resistors are on a daughter board under the main one and the extra caps and pull-down resistors for the bass cut and crossover frequency switching are on another (vertical) daughter board connected to the 3 pots.

I have decided to keep the next few projects simpler.

bluebunny · April 20, 2016, 09:22:44 AM

Quote from: samhay on April 20, 2016, 03:28:33 AM
Marc - this works quite nicely with my fretless bass....

Useful to know - thanks Sam. Perhaps another one for the backlog!

Cozybuilder · April 20, 2016, 09:39:49 AM

Nice tight build Sam! Happy to see the jacks on the back of the box, the anti-turn holes for the pots & switches, and those LED holes aren't bad looking. Is that etched or a waterslide or some fancy calligraphy? It looks good

samhay · April 20, 2016, 10:22:16 AM

Thanks Russ.
If it's worth building, it's worth building something that will last.
The labelling is a toner transfer.

deadastronaut · May 08, 2016, 10:11:02 AM

looks great sam...very nice

ive been using toner transfers a bit lately....being lazy and not etching

but when its just for me toner transfer/clearcoat is more than adequate..

nice quick way of labelling..

samhay · May 08, 2016, 03:51:02 PM

Thanks Rob.

samhay · April 25, 2018, 07:42:21 AM

Necropost to re-post pictures that disappeared thanks to Dropbox's purge.
Apologies as some of these are quite large files (~1M). You should be able to see larger versions by clicking on them/'viewing' image in a new page/tab.

Rob Strand · April 25, 2018, 08:19:47 AM

QuoteNecropost to re-post pictures that disappeared thanks to Dropbox's purge.
Apologies as some of these are quite large files (~1M). You should be able to see larger versions by clicking on them/'viewing' image in a new page/tab.

It's funny how thing like this get lost and found.
Good thing we have got lots for heads on the forum to fill in the cracks.

samhay · April 25, 2018, 12:18:18 PM

These pictures were never lost, just hiding.
Where I've put the pedal is another matter - it might be hiding too. Nice to be reminded to pull it out and have a play.

Xavier · November 11, 2018, 07:57:41 AM

Another necropost here.

I am about to build this circuit , has anyone built it ? So far I have spotted a mistake in the layout (apparently). According to the schematic it's input to R1 (10M).

As per the layout, Input goes to R2 (1K) and then into R1, so I stopped there....

samhay · November 11, 2018, 04:43:43 PM

Yes, I've built several using the posted layouts.
While placing the input resistor before or after the pulldown resistor is not entirely equivalent, it makes very little difference, so I moved to to make the layout cleaner.

As with any filter, I suggest you breadboard it to tweak frequencies to taste. I also wouldn't suggest you build the fully featured version as this is overkill.
I would stick with a single tilt centre frequency, keep the switchable bass cut, and set Zin to max (i.e. you don't need the pot). This way it's 2 pots and a switch. Without a few tweaks to the layout you could fit it in a 1590A if you were so disposed.

Xavier · November 12, 2018, 08:58:24 AM

Hi Samhay, thanks a lot for the answer, and for posting this circuit !

I will build the simple version. I will use it in front of a Marshall JVM410HJS to clean some of the bass frequiencies before the distortion, to make it palm-mute friendly. It will be my "tight" pedal.

samhay · November 12, 2018, 04:48:38 PM

No problem.
Good luck, and let us know how you get on.

Xavier · November 13, 2018, 04:44:38 PM

I think I found a couple more issues, since I've been trying to debug for a while.

According to the schematic, center lug of the Tilt pot goes to pin 6 of the opamp. In the layout it goes to pin 2 of the opamp

Also, Level 1 and 3 should go to opamp pins 2 and 1 respectively. In the layout, Level 1 and 3 go to opamp pins 6 and 7 respectively.

Tilt 1 should also be connected to R7, but it isn't in the schematic....

I will try to redo the layout since I am very interested to finalize it..........

samhay · November 13, 2018, 06:05:36 PM

I guess I switched IC1A and 1B in the layout as pins 2 and 6 are both inverting inputs and pins 1 and 7 are outputs. As long as pins 3 and 5 are also switched (or in this case connected to the same point) then it's not a problem as the 2 op-amps are equivalent.

Tilt 1 goes to Cx + R8 (1k) and C9 + R7. I've switched the order of C9 and R7 in the layout* - R7 is the 10k top right in the layout (I assume you can see R7 in the schematic above "TILT CROSSING"?).

*the order of components in series can be switched as long as nothing is connected between them.

Ben N · November 27, 2018, 06:24:08 PM

Similar to a DOD FX-10.

samhay · November 28, 2018, 07:24:38 AM

Broadly, but the filter topology is different, which is the centre piece of this design.

amz-fx · November 28, 2018, 03:01:58 PM

Sam, I like that input stage with the impedance control. I may steal that from you to use in some future project!

regards, Jack

iefes · November 28, 2018, 03:08:18 PM

The variable Input Z is really cool. Would somebody of you more experienced folks here mind explaining to me how it works? I don't really get it yet. It would be great to have a simple multi-purpose preamp with adjustable input Z for use with guitars, mics etc.

Thanks heaps!

samhay · November 28, 2018, 03:33:46 PM

Jack, I'm sure I've borrowed a few ideas from you over the years, so please be my guest.

Iefes. The input impedance is 'bootstrapped'. I'm sure Rod Elliot can explain it better than I can:
http://sound.whsites.net/articles/high-z.html

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Tilt preamp