Maestro Filter Sample and Hold

[wui223]

I want to try ur layout also but i just cant get the Dual OTA chip

[Fp-www.Tonepad.com]

wui, No offense, but I don't think you're qualified for this level of project. If you were building on a pcb I would think you'd have a chance, on perfboard, I just think you have too little chance of success.

Why don't you start another thread for troubleshooting your build and leave this one for those who are building the new circuit.

Fp

[Fp-www.Tonepad.com]

Soggy, Ry, Updates?

Fp

[Fp-www.Tonepad.com]

Duplicate post.

[soggybag]

Still working Fathers day and work have taken some time away from work in the "lab". Maybe I'll have a chance to finish up up later this week...

[Ry]

I haven't gotten the board drilled or populated yet.  I had a busy weekend and only got the board done on Friday because I had the day off and there was no one around to distract me.  I have a very active outdoor life and my wife and I have about two months to safely do canyoneering trips here in Arizona before the summer rains start, and believe me, you don't want to be in a technical (involving climbing, swimming and rappeling) canyon when it starts raining!

I will hopefully get the board drilled tonight and start populating it.

Ry

[soggybag]

I have my board populated and all of the jacks and pots wired up. I tried to fire it up this morning. I only put in the MAX 1044 to test the voltages. But ran into a problem when the MAX 1044 started to get really hot.

I will have to find some time after work to take a closer look...

[Ry]

I've got my board populated except for the pots, jacks and switches.  I will hopefully get the rest of it wired up tonight and see what happens when I apply power.

I did notice that there appears to be a connection missing on the Range pot lug 3.  It should be connected to the junction of the 100k and .15uf cap, but there are two pads interrupting the trace...I think.

I will make sure to check over the 1044 section prior to powering it on, though.  I used my last 1044 on this project.

Ry

[soggybag]

I noticed there were two pads in themiddle on the left side of the board that seemed to need a jumper, why I'm not sure, but it looked they should be connect according to the schematic.

[Fp-www.Tonepad.com]

Soggy,

You're right. I left those there for experimentation.

Fp

[Ry]

FP,

I think that the 1044 layout/schematic is incorrect.  Wui made the point that the 10uf cap is going between pin 2 and ground on your layout/schematic might be incorrect, and I think he's right.  It looks like the cap should be going between pins 2 and 4 (thus creating the charge pump action) and not to ground.

The diagram on GEO can be easily interpreted how you did, but check out the data sheet: http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf

I think that the negative side of the 10uf cap should not be grounded, but rather just connected to pin 4 of the 1044.  This would account for soggy's warm chip.

Ry

[wui223]

Anyway i made the PCB for FSH and decide to substitue the dual OTA with two single OTA, coz i cant get the dual version. In fact everything is just the same. so i will this weekend hopefully overhead Ry and be the first to success in Tonepad layout.  

[soggybag]

You're all right, the negative lead of10u cap needs to connect to pin 4 on the Max1044. I did this and everything seemed power up correctly.

After I tested the voltage coming out to the charge pump I put the rest of the chips and transistors in. I used some BF2457 (I think thats the number) for FETs. I didn't check the pinouts, I just followed the layout (always a recipe for disaster).

I didn't hear anything, so I plugged the guitar into the input and the amp into the output...

But I still didn't hear anything. Then I got hungry, and the the saga will have to wait to be continued...

[Fp-www.Tonepad.com]

I have corrected the pdf.

For those who made the pcb, the correction is easy. Just cut the trace from pin4 to ground and the trace from the negative lead of the capacitor to ground. Then connect the cap's negative lead to pin4.

I hope this error didn't fry any MAX1044s.

Fp

[soggybag]

I didn't have much time this weekend to work. But I applied the audio probe and I seem to be getting the signal through pin 9 of IC1 but the signal diappears after the 22K resister between pin 9 and pin 6 of IC1.

It seems the audio signal gets sucked off into the envelope generator and is gone.

[Fp-www.Tonepad.com]

Soggy,

pin6 of IC1 is -8vDC there shouldn't be any audio in pin6.

Did you add the jumper between the two orange square pads on the left of the pcb? it was missing from the first revision of the pdf I posted. The envelope generator converts the signal to a control voltage, so the guitar signal is also lost there, the audio probe won't be of help here, an analog DMM is a better tool to see if the envelope generator is working.

Fp

[soggybag]

My mistake I meant pin 4. I didn't have much time this morning I will have to spend more time testing later this week.

[Fp-www.Tonepad.com]

Soggy,

From pin9 follow the 0.15uF capacitor, then there's the 100k/3.3k voltage divider going to pin4, that voltage divider lowers the amplitude of the signal a lot.

If you have all the parts in, you should be getting some audio at the output regardless of the control settings, check that you have the FET pinout correct.

Fp

[Ry]

We have liftoff!  I got my board all populated and fixed the 1044 traces and it worked immediately.

That said, there is a tremendous high pitch bleed through in both the filter and sample/hold settings that I cannot get rid of.  I played with the trimmers for about an hour with no luck.  If I trim out the noise, I also trim out the filtering.

It's very hard to compare it to the GGG old-style version with this issue, but I noticed that this circuit has a much slower highest setting for the sample/hold.  It's also much, much brighter than the older version.  Any other comparisons are not fair at this point.

Ry

[Fp-www.Tonepad.com]

Great!

At least we have something going on, I fear that including all the mods in such small board can have that result (noise), please keep debugging it. I don't know how much is the circuit affected by changing the OTAs...

Let's wait for soggy's results.



Fp