DirtBag mods for v3205 - Final Solution

[madbean]

Based on 7 or 8 hours of tweaking and experimentation with the DirtBag, plus partially tracing out the Memory Boy here are the suggested alternative values I've selected. These seem to be the best values possible for minimizing distortion while keeping the delay line levels high enough and not too grainy. It's not perfect, but I feel confident now that it's as good as it's going to get without some radical alteration in design. Which would not be a bad thing, but it also would not be a Memory Man either!

Anyway, here is what you need to change:

R62 - 15k from 7k5
R42 - 20k from 11k (value is not critical--22k is fine)
R17 - omit/remove
R16 - jumper instead of 33k
C9 - 10uF from 4u7
R11/R12 - 47k --- 24k resulted in more distortion with the other changes listed so use 47k for both. This results in an output voltage of just over 6v, which is the case with the Memory Boy.
R10 - a combination of 1uF and 6k8 in series instead of a single 68k resistor. I suggest using either multi-layer ceramic or electrolytic here. If using electrolytic then make the positive end go toward C7 and the negative end toward the 6k8. The addition of the cap makes a big difference in keeping the repeats more even and longer lasting.

A possible mod: you can lower the value of that 1uF from above to filter the repeats, if you like. Anything from 15n to 33n will give you a noticeable "telephone" type filter, which I think sounds really cool (similar to the Deep Blue Delay). For experimenting, I used a socket for R10 and then ran wires from the two ends to the breadboard, then just swapped out different caps to see what worked. 1uF has the least amount of coloring, and 33n is very effected.

All other values are stock. These mods would be done INSTEAD of the earlier mod I suggested (replacing R21 and C14 with 100k resistors).

Overall, this improves the delay significantly, but it's not perfect. The threshold and release of the compressor is just not great and I have not found any way around that. But, with very careful (and minute) tweaking of GAIN1 and GAIN2 you can get very acceptable results. There will still be some hiss with very soft notes and long delay times. As I stated in the other thread this is exactly the case in the Memory Boy.

So, I hope this is somewhat more satisfactory of an end result for everyone. I wish it were perfect, but I feel like it's as good as it can be with these changes. One positive note: the delay from the DirtBag seems to be about 100-200ms longer than the Memory Boy!

[RonaldB]

Thanks Madbean for putting so much time in this.
Much appriciated.

RonaldB

[andersom]

Thanks Bean!

[LaceSensor]

Thanks for this.

Feel almost like I'd be better starting another one though. I'll ply mine some more and have a think.
There's a large number of parts to desolder.

[mjcyates]

I just finished doing all of the mods listed here (the ones in gold). I also removed all of the circuitry related to the overload led. I think it is pretty close to where it needs to be. I may send it off to my brother-in-law so he can bias it with a scope. Removing the overload led circuitry seemed to help reduce the distortion. Anyway I am ready to box this up and just tweak the trimmers.

[cjkbug]

I just finished doing all of the mods listed here (the ones in gold). I also removed all of the circuitry related to the overload led.

would that be everything located above c12 on the schematic? or are any of those parts critical?

[madbean]

R18, 19 and 20, C13, Q1 and D1. You can omit those if you don't want the overload LED. They have nothing to do with the delay---just a visual indicator of the line level into the BBDs.

[MadeByMike]

To be honest, this is a lot of changes, and the build PDF still seems to not have been updated.

I'm getting quite concnered that with the amount of desoldering I'm going to have to attempt on a very tight board that I'm going to end up with a non working delay, which will be very annoying considering the initial outlay and the time spent building it this far. I really would have expected that both the v3205 and 3005 versions would have been built and tested on the production boards before this was made public - that's surely the bare minimum level of testing for a multi use board?

I certainly didn't start building this project (or purchase the board) thinking it hadn't been verified as working, and the build document didn't suggest this either, indicating that only two component subs and some jumper changes were needed to convert for use with the Cool Audio chips.

At this point I really wish I had a fresh board to work on, but as it is all my caps and most of my resistors (including all but one of the above changes) have been soldered in place. It's going to be a lot of work to attempt to make these modifications and I'm pretty disappointed I have to do so.

Having said that I appreciate that Brian has investigated the issues and tried to put it right, but I do feel let down this was not tested before the boards went on sale. I have outlayed significant monies on the board mounted pots, and chips from Small Bear along with the board itself. I just hope I can get something workable out of it.

[mjcyates]

I understand your concern, however it is not as daunting as it may seem. If you go slow, make sure you mark the components your are replacing with a sharpie, and have a little patience you will be successful. I did all of the changes yesterday in about 45 minutes using desoldering braid from Radio Shack.

[MadeByMike]

I understand your concern, however it is not as daunting as it may seem. If you go slow, make sure you mark the components your are replacing with a sharpie, and have a little patience you will be successful. I did all of the changes yesterday in about 45 minutes using desoldering braid from Radio Shack.

I used desoldering braid on the previous components I have already socketed (R21 and C14, which now are to be reverted to their stock values.. ) and didn't manage to get the 2 sided via completely free of solder for any of the joints, it involved inserting the socket whilst reheating what remained - which is not a simple process.

[jkokura]

Mike, I'm sorry to hear you're disappointed, but I understand it.

If I can help you understand at all, Brian did build several prototypes of this and other boards, but he has admitted that perhaps the proofing was a little rushed. His builds went together well and quickly, so there was no expected problems to be had. Once several builds experienced issues he looked into it further and found the issues.

Is there a way I can help? I have trouble desoldering the double sided boards as well, but I recently got a desoldering bulb to use for desoldering and that seems to work much better than the braid I've typically used. Perhaps finding a better tool to use would be worth looking into? I bought that desoldering bulb for 5 bucks I think.

Jacob

[MadeByMike]

Brian did build several prototypes of this and other boards, but he has admitted that perhaps the proofing was a little rushed. His builds went together well and quickly, so there was no expected problems to be had.

I don't understand.

If the testing builds were made on the production boards with v3205s and the original bill of materials and experienced none of these distortion issues, then why are we being told to make these changes?

I might have to look into buying some more desoldering apparatus if I run into difficulty getting these components out, and I'll cross that bridge when I come to it.

[saxoftenest]

Thanks, Brian!! I'll be populating my DirtBag sometime this week, and your thorough efforts are greatly appreciated.

[madbean]

Mike, I am empathetic to your concerns, and I understand that it is frustrating to re-do work. But, to suggest that I somehow did not test or fully commit to making this project work is simply not true. The two different solutions I proposed here are in response to problems that SOME have encountered, but not everyone. You do not have to make all these mods. These are what I came up with after tracing and experimenting and what I feel like will give the best result for the most people. And, these are improvements compared to the results I had in prototyping the project. While I do accept responsibility for that, I'm also am realistic in the sense that different people will get different results some of the time and that is unpredictable and that people also have different expectations of what the end results will be.

Just to give you some insight into what went on to develop the project...

Approximately 40 hours of PCB design. There were seven full and completely unique layouts done of the DirtBag before the final production design was finalized.
Approximately 25 hours of building six prototypes, on three different PCB designs.
At least another dozen hours of picking apart many different schematic drawings of the DMM and researching topics about the DMM.
Several hundreds of dollars in prototyping PCBs and parts.
Several hundred dollars in getting the boards fabricated.

All this was done before selling the first board and took place over three to four months. To what extent I can make this process more full-proof, I don't know.

Obviously, I'm most concerned about making customers happy and not necessarily being vindicated. And, I am truly sorry for your disappointment. On the other hand, there is an underlying assumption on my part that a person who is willing to take on something as deep and complicated as the DirtBag is not going to be put off by having to do some tweaking and has the appropriate tools to do so. Maybe that is too presumptuous on my part and maybe not. Honestly, the only way to find out that sort of thing is by "breaking a few eggs" first! I do feel that I have made a pretty tremendous effort over the past week to rectify the situation, though.

In any case, I won't make excuses for myself in regards to putting something out that wasn't exactly perfect. It's actually something I strive to do every time I release a project. But, I'm realistic that projects like this don't always work out to 'paint by numbers', sometimes I make mistakes, and I cannot always be sure that everyone will be happy. I wish these things were not so, of course.

If you truly feel that you would prefer to start over rather than going through the trouble of making the changes, I will send you a new board. I'll have to do a count and see what I have left (I think I'm down to one as of yesterday--but I'll check).

[jkokura]

Brian did build several prototypes of this and other boards, but he has admitted that perhaps the proofing was a little rushed. His builds went together well and quickly, so there was no expected problems to be had.

I don't understand.

If the testing builds were made on the production boards with v3205s and the original bill of materials and experienced none of these distortion issues, then why are we being told to make these changes?

I might have to look into buying some more desoldering apparatus if I run into difficulty getting these components out, and I'll cross that bridge when I come to it.

Mike, it did work within the specs Brian originally thought were ok, but when other builders had issues he looked into it further and it seemed like there were issues and he just hadn't noticed or thought they were issues. He talks a little bit about it here: http://www.madbeanpedals.com/forum/index.php?topic=3336.0

Jacob

*edit: Brian beat me to it I think