Low rider problems

[sidebernie]

I just finished my Low Rider and am experiencing some problems. I think these are probably some common problems that others may have had.

1) Project is Low Rider
2) The UOCT is a fuzztone. I have no upper octave at all. I have tried the trim pot but it does not help in any position. It just changes the tone of the fuzz. The DOCT1 seems to work ok but bounces in and out so it seems to not be tracking great. The DOCT2 tracks worse than DOCT1 and does not work for high notes. The biggest problem is no UOCT1
3) When I built it I was very careful and measured every resistor and double checked the location of all components. I have looked at the soldering with an eye loupe and can see no shorts or cold joints. I tried the trim pot as directed with the other pots off with no cchange except in tone. No upper octave at all.
4) I used the 2N5457 tranny's for Q2 and Q3 and J201 for Q1. I did the C10,  C12 mod, just removing   C12. I am using 4013BCN parts. I have not measured any voltages but there are no power issues or signal loss. Clean sounds good and just like bypass when set to unity. 


I have seen that others have had similar issues so I'm hoping someone has an idea of what may be going on.

[madbean]

As far as the lower octaves, you should not expect perfect tracking. Such a thing is not possible with this kind of analog design. It should track really well with a strong attack over short durations, and then it may "jump" around a bit as the note dies out. Putting an overdrive, or perhaps a compressor in front of it might improve it a bit.

You should have more or less the same result as the demo here:
https://www.youtube.com/watch?v=6EvgnMvfs_I

It's mostly staccato playing, which is perfect for this kind of effect, but you will hear a few notes ring out and the tracking keeps up pretty well.

For the upper octave, it will be most noticeable on the higher frets, particularly the 12th fret area, similar to an Octavia type pedal. Here's one possibility for making it more prominent: replace D1 and D2 with either BAT41 or 1n34a, and increase the value of R13 to 20k-47k. This should increase the sensitivity of the rectifier portion and also boost it at the same time.

[sidebernie]

Hi Brian,
Your suggestion worked great. I used some 1n34's and the fuzz is almost completely gone. I think I went a little over board on R13 and used a 47K which was way to much gain. I might go back to 10K and see how that works. Your boards are really well made. I think it would be a good idea to change to the germaniums on the parts list. It made a huge difference.

Thanks for your help,
Bernie

[madbean]

Bernie, that's great! I'll add this in the MODS section. It was mostly a lucky guess.

[m-Kresol]

I've got exactly the same problems as sidebernie. The upper octave is just a fuzz/distortion like sound without any octaving and the lower octaves seem to be hopping up and down in tone and are really sensitive (I just have to slightly touch my strings to make it go mad).
I used the upper octave mod (leaving C12 and 10n for C10) and used 4013BP ICs. Is there any other way of fixing the problem than switching D1&D2 to 1N34a? I don't have any left and it's a pain to get those.

[madbean]

Do you have any BAT41 or BAT46? Those will work in place of the germaniums.

[m-Kresol]

Unfortunately, I have no diodes left over, since I just ordered the parts I needed. The only germanium diode I could get fast is a 1N60 (4mA, 20V), which doesn't work right? But fortunately I can get both of the shottky diodes you suggested.
Besides that, can you explain why the fuzz occurs? I don't really understand why it shouldn't work with the standard parts. Obviously, many of us applied the capacitor mod for stronger upper octaves without having these problems.
Would changing it back to the non-modded configuration solve the problem? then I wouldn't have to get the diodes.
Thanks

[m-Kresol]

I just put the thing together and there is improvement, but it still kinda sucks. The fuzz of the upper octave is mostly gone with 2 BAT41 diodes for D1&D2 and a 33k resistor R13, but the signal is no octave signal, it's still like a fuzzy version of my clean signal. Any ideas, what could be wrong? I switched back from the capacitor mod to stock version btw.

[m-Kresol]

update:
I socketed the R13 position and tried values from 5k6 to 56k. The lower the value, the louder the octave up (which is obvious) and I think the fuzziness is also a little decreased, but the clean signal is also starting to sound fuzzy, at least when i play my humbuckers (which i always do). Increasing the resistor value leads to increased fuzziness and smaller volume. Anyhow, I can still hear no octaving up. I thought I heard some overtones with 33k and 22k, but it was hard to hear with the increased fuzz.
I also just double checked all the other resistor and cap values, directions of diodes, etc. everything seems to be as it should be... I'm really running out of ideas and would appreciate any help!

[m-Kresol]

Hey guys,
I finally managed to upload some photos. Please give me any hint to where my problem might be.
Front:
Front2:
Solder side:

I also wanted to measure the voltages on my ICs, but unfortunately I just found out a couple of days ago that my voltage supply seems to be non regulated, so I have no 9V supply. (setting of 5V gives 8.3V, 7.5V gives 10.2V, 9V gives 12.15V). Therefore, measuring voltages doesn't make sense for comparison.

Here's a list of the ICs i used (with links to the datasheets):
IC1: TL072IP
IC2: LM324AN
IC3&IC4: HEF 4013BP
IC5&IC6: ST TL074CN

If anyone could point me in the right direction, that would be awesome, I'm getting frustrated.

[midwayfair]

The upper octave is not really an octave up but it's SUPPOSED to be more of a fuzzy version of the dry signal. There's some octaving but not a ton. I can only get octaving by playing a certain way in a certain part of the neck with the tone control rolled off.

As far as your other questions: 1N60 is fine for the diodes. In fact, I just built one last night with 1N60 or 1N5817 in every diode position except R7. The diodes rectify the audio; you just need a low forward voltage. The composition of the diodes (germanium or silicon) doesn't matter especially for D1, D2, D8, and D9.

I'm not going to pretend to know all the ins and outs of this circuit (i.e., see my thread from last night), but I can at least tell you that clean +8va is impossible in an analog circuit. You can get it "somewhat clean" or you can get a more prominent octave -- the octave generated will sound dirty, because it's merely filtered harmonics, which is what distortion is to begin with. Cleaning it up involves actually filtering out the harmonics.

Also, per the build doc, omit C12 and reduce C10 to 1nF (or omit it). These are low-pass filters in the upper octave path, and they cut a LOT of treble after the "octave" has been generated. It would almost be like cutting bass after the octave downs have been generated.

[m-Kresol]

Thanks a lot! So most likely, the pedal works already without me realising it. In the beginning i built the mod with the capacitors but after switching to schottky diodes i went back to the original values, since I read that using schottky diodes and apply the capacitor mod is too much. I'll try to go back to the mod again, maybe then I'll be content with my sound.
Thanks again, you made my weekend!