9V Electric Mistress retrofit with MN3007

[oldschoolanalog]

OK, got mine built.  We have flange!!

1. The alignment procedure info talks about a gain trim and a balance adjust trim.  This build doesn't appear to have these.  I take it you just skip these steps...?

Since you can't adjust what's not there; "adjust what ya' got."

I'm just using a free signal generator app for the iPhone which is far from ideal and still trying to work out how to drive the o-scope I have borrowed which isn't making things any easier.

There are several simple signal generators you can put together real quick. Use The Search Function (UTSF).

2. I've notice an obvious volume drop when the effect is engaged.  I was under the impression from the notes on the schematic that some changes had been made to the original circuit to address this issue.

Yes, very obvious. This issue arose when the original circuit was changed to TBP. The easiest solution is to put something at the output to give a bit of boost. A simple op amp based circuit will do just fine. The notes on the schem referred to the original non TBP unit, IIRC.

Just wondering if others had this issue...

You are not alone.

...or it is just a side effect of not having the trimmers correctly calibrated yet.

No, although the trimmers do have to be correctly adjusted.

All the Best!

[Just1More]

Dave, thanks for your responses.

I'm in business.  At this stage I've calibrated by ear, but it's sounding good.  I'll try and fine tune a bit more when I have some more time to sit down and work out how to drive the o-scope better.

Re: the volume drop, the simplest thing might be to try the buffered bypass (assuming that actually fixes the problem).  As long as it's got a decent buffer I don't really care.  I also found a schematic for a boost stage in the TZF conversion thread so that's Plan B.

The only other issue I've got is that you can hear the sweep in the background when not playing.  That was with a (switch mode) power supply connected.  Running off a battery it's virtually silent.  I will play around with the PS filtering and see if I can tame the background noise some more.

The next challenge is to try and find a 1790NS sized box somewhere here in Australia otherwise shipping is going to cost me about 3 times the price of the box.

Thanks everyone for all the work on this - great project!

[Just1More]

Just in case it's useful, here's what I did to calibrate by ear:

Bias: With the bias trimmer at the centre position I had a distorted flanged signal.  Backed the bias off just enough to remove the distortion.  Rotated Range pot through full range to double check.

Clock: Set switch to filter matrix mode.  Set trimmer to get 70kHz at pins 1 and 5 of the 4013 when measuring with my DMM.  Tweaked a bit in either direction to try and make it a bit quieter.  Finished up at about 75kHz from memory.

Feedback:  Max the feedback pot.  Increase the feedback trimmer until it starts oscillating and then backed it off to clean the signal up.  Double-checked by working through the full range and rate.

[shadowmaster]

Turned the Range knob and there was no more ticking. I was surprised. Fiddled with the Speed knob and the clock trim and still no ticking while listening to a beautiful flanged sound at the output. Popped the 2N5087 back in there and the ticking was back.

I stand corrected on what I've said here. I was still able to hear a clock dropout/tick with the 2N3906 on slower Rate with the clock trim set high but backing the clock trim a bit totally eliminated it.

Just in case it's useful, here's what I did to calibrate by ear:

Bias: With the bias trimmer at the centre position I had a distorted flanged signal.  Backed the bias off just enough to remove the distortion.  Rotated Range pot through full range to double check.

Clock: Set switch to filter matrix mode.  Set trimmer to get 70kHz at pins 1 and 5 of the 4013 when measuring with my DMM.  Tweaked a bit in either direction to try and make it a bit quieter.  Finished up at about 75kHz from memory.

Feedback:  Max the feedback pot.  Increase the feedback trimmer until it starts oscillating and then backed it off to clean the signal up.  Double-checked by working through the full range and rate.

Nice. No plans to attempt MN3007 TZF version? Someone among you here should do it.

[jorge r]

Looks like there might be enough room on the PCB at the output to squeeze in a FET for a bit of volume boost.
Just a thought...

I think there is enough room too. But I'm not smart enough to do the booster. If you or anybody else  make the schematic, I'll put it on the layout to solve the volume drop problem.

[Scruffie]

Nice. No plans to attempt MN3007 TZF version? Someone among you here should do it.

I've been offered a spare bit of space (about a 1590BB size) on a 4 layer Express PCB Board order... if I could get some help I could have a TZF board made up and prototyped professionaly... could be the next A/DA Group buy if it works...

But when I posted the idea and the seperate thread... there wasn't too much interest.

[Just1More]

Here's an update to my redraw of the layout.  I've built it an it sounds good so I'm prepared to declare it verified. (Click image for hi-res version.)





I tried the buffered output and it is not to my liking.  The effect/bypass levels are very similar, but there is definitely some colouration to the bypassed tone and it doesn't sound as full as the direct signal.  It really needs a boost if you go with true bypass though.  I've tried out the recovery stage in the TZF conversion and it does the job nicely.  I still want to play around with the LPB/BMP style transistor boost stage too because I can probably make this a little more compact.

I have done some experimentation with the power filtering but I'm not there yet. It's still not acceptable when powered with a 1-Spot but silent when running from a battery.  This is the first time I've had any issues with this power supply.  I'm open to suggestions...

[oldschoolanalog]

>I have done some experimentation with the power filtering but I'm not there yet. It's still not acceptable when powered with a 1-Spot but silent when running from a battery.  This is the first time I've had any issues with this power supply.  I'm open to suggestions...<
Have you tried it with an "old style" 9VDC regulated PS or wall wart?

[Just1More]

>I have done some experimentation with the power filtering but I'm not there yet. It's still not acceptable when powered with a 1-Spot but silent when running from a battery.  This is the first time I've had any issues with this power supply.  I'm open to suggestions...<
Have you tried it with an "old style" 9VDC regulated PS or wall wart?

No.  The only other power supply I've got is an old unregulated wall wart.  It's marked as 9V, but puts out just shy of 15V with nothing connected.  I'll give it a try. Better double check some datasheets first.  Is the MN3007 OK at that kind of voltage?

[Scruffie]

Nice. No plans to attempt MN3007 TZF version? Someone among you here should do it.

I've been offered a spare bit of space (about a 1590BB size) on a 4 layer Express PCB Board order... if I could get some help I could have a TZF board made up and prototyped professionaly... could be the next A/DA Group buy if it works...

No Love at all for this? It's just board space going to waste otherwise but I need a bit of guidance to get it off the ground... by a bit I mean alot.

[Just1More]

A question for those who have completed this build. How quiet (or otherwise) should it be?

Mine is either still not callibrated correctly or has some other problems. I can the LFO sweep way too clearly when not playing so last night I experimented further with the trimmers.  I adjusted the bias a bit and found I could eleminate the noise, but then the flanged sound was distorted so backed it off again.

Next I played with the clock trim. This affects the pitch of the noise so I tried dialing it up till I could no longer hear it. That was fine, but instead there was a loud "tick tick" as the sweep changes direction.

Admittedly it's not boxed up yet, but I don't expect that will do much for this kind of noise. Just trying to find out whether I need to lower my expectations or keep working on it.

On an unrelated note, I've dealt with the volume drop issue by adding a LPB-1 boost stage to the end of the circuit which works nicely.  I'll build this on another daughterboard if I get the noise issue sorted.

[Thomeeque]

..Just trying to find out whether I need to lower my expectations or keep working on it..

Maybe record some samples for us, it's hard to tell from what you have written.. T.

[shadowmaster]

Just recently boxed-up mine. Here are some pics. 

Still naked but with the rest of the offboard components installed.


Now mounted to the enclosures.


Here with the PCB shot.


Mission accomplished.

A question for those who have completed this build. How quiet (or otherwise) should it be?

The clock noise in mine can be heard around the same level as the hum in my amp. I'm lovin' mine. Should post some soundclips soon so as to inspire others to build this and also share their own experiences where others can also learn from.

[Just1More]

Mission accomplished.

Nice work shadowmaster!!  Great looking build.  Where did you get the enclosure? - that looks great.

[Just1More]

Maybe record some samples for us, it's hard to tell from what you have written.. T.

Tomas

I've played with the trimmers some more.  This is about as good a balance as I can strike at the moment - certainly better than it was.  I think there is still some distortion on the flanged signal but backing the bias off further will introduce more noise.  I'll hook it up to the scope later in the week just to verify.

This is very crappy but will do the job - just recorded on my iPhone because I don't have any other recording gear available.  The level is pretty low - you'll probably want headphones.

Noise sample

Signal path is is guitar -> test rig (Electric Mistress powered by a fresh battery) -> Noisy Cricket amp -> speaker.  I put the iPhone right up against the speaker to get a reasonable recording level.

First there is clean guitar, then with the effect.  I cranked the amp output at the end so you can hear the noise more clearly.  There are some grounding buzzes in there - don't worry about them it was just my clumsy fingers touching things they shouldn't.  I varied the Rate pot so you hear the effect but Feedback and Range are maxed out the whole time.  The noise is much less noticeable at more moderate feedback and/or range settings.

I also used an el cheapo (free) SPL meter iPhone app just to compare levels a bit.  Loudest parts are about 80dB with iPhone 6 inches from the speaker in this test.  The background noise sits around 30dB but jumps to 40dB as the sweep changes direction.  For a reference point I checked this against my Rat clone.  Background noise never gets anywhere near 30dB from that pedal which is one of the noisier ones in my collection.

I tried adding the 47R resistor and 22uF cap near R29 as suggested but this made no noticeable difference.

I've started out with the audio probe.  The signal is clean at pin 1 of the 4558.  At pin 5 the sweep noise is very evident and also at the wiper of the feedback trimmer.  You can hear it at pin 6 but it's not nearly as obvious.  That's as far as I've got at this stage....

Here's some images in case it's helpful:





BTW here's the clock readings I got in filter matrix mode as previously promised:
Range pot fully CW: 76.1kHz
Range pot fully CCW: 1.11MHz

[shadowmaster]

Nice work shadowmaster!!  Great looking build.  Where did you get the enclosure? - that looks great.

Bought it during one of my business trips in Japan. The name of the manufacturer is Takachi. Try to google and maybe find their local distributor in your place.

Here's the link to their site.

http://www.takachi-el.co.jp/data/h_english/english00.html

[azrael]

Am I missing something? shadowmaster, Play1More, the offboard wiring for your daughter board looks a little different, in regards to C2. 

[shadowmaster]

Am I missing something? shadowmaster, Play1More, the offboard wiring for your daughter board looks a little different, in regards to C2.  

I believe you are talking about the power and ground connections of the daughterboard going to the mainboard. Below is the answer sir. If you want a bulletproof build, follow how the experts do it.

http://www.diystompboxes.com/smfforum/index.php?topic=78270.msg699802#msg699802

Hi John!

Impressive work! However I cannot check it properly (I did not build it ), I have just one small note - as I advice in the first post, I would not feed it from SAD socket - even Dave proved that it is nothing crucial actually, I would still advice to feed it this way as it should minimize risk of unwanted interferences between retrofit and rest of the circuit via feeding tracks.

Good luck, T.

[Just1More]

Here's some further info to my previous post.  I've got the voltages now on all the active components.



Any ideas or suggestions would be greatly appreciated.  This one is really starting to frustrate me.  Everything seems to work as expected but I'm sure there shouldn't be so much noise.  The only thing I've really got to compare against is a Boss CE2 and it's pretty much silent.

[Just1More]

OK, I'm a goose 

Obviously my build really hates power supplies like the 1-Spot.  Although the EM was running off a battery, my LM386 test amp was using the 1-Spot for its power supply.  Today I switched back to my normal amp with the EM running off a battery and it's nearly silent except for the most extreme settings.

At least I've got a workaround now.  I'll see if one of my mates has a transformer based power supply and whether that's any quieter.  I might have to finally invest in a proper isolated power supply.