Please help a novice

[TimmyC]

Hi I am totally new to the world of making/modding effects so I was just wondering if I could have a bit of advice.

I have a guitar pedal that totally sucks the low end out of my tone (I play bass) and was wondering what could I do to solve this problem.  The pedal is a Signal Flex, Analog Echo Delay and I cant hardly find any information about it.  Basically I know nothing and would just like to be pointed in the right direction.  I think I am way out of my league here and don't understand most of the technical stuff on this forum but maybe I can give it a shot with the help of you guys.  I have heard stuff about changing the value of capacitors to alter the input and output frequencies and stuff like that but thats all I know.

Maybe this is the wrong thing to ask but is there anyone who could give me hand or I could even pay someone to do it if they are willing? (I am in the UK)  Or maybe I will give it a go, lets see how it goes.

Tim

[gez]

Chances are it's as simple as changing a capacitor.

Follow the lead from the input jack's tip to the point where it joins (possibly via a switch if it's true bypass) the circuit board.  The first thing you should see (or one of the first things) is a capacitor.  If you're unsure what they look like, take a photo of your board and we can tell you what to look for.

Making this larger in value might be all that's required.  If someone has a schematic (or can link to one) it'll make life easier.

Are you able to post a pic of the board?

[gez]

PS  If you're anywhere near SW London I can take a look...

[TimmyC]

This is as much I could get out before I started pulling wires out the board.

[TimmyC]

And I am in Dorset, prob 2 hours from where you are.

[gez]

And I am in Dorset, prob 2 hours from where you are.

I'm sure there'll be some forum members closer to you, but for the meantime can you try and get a shot of the board from directly above it?  Plus, can you follow the wire from input jack to the board and tell us what colour it is so that it can be identified in the photo?

This circuit is probably a copy/derivative of a popular pedal (Boss perhaps), so comparing chips/resistors with some schematics might get us somewhere, but we need to be able to read the codes on the chips and see resistor colour codes.

[Mark Hammer]

It is your plain vanilla 300ms MN3005 or MN3205 analog delay with a 571 compander chip.

There is a reasonable possibility that there may be several points where a capacitor value chosen so as not to interfere with guitar frequency response may need to be raised in value, at which point you need to consider whether it is worth your while to monkey around with it.  I'm not absolutely certain this is the case; just prepare yourself for its possibility.

The question I need to ask is whether the bass-sucking is restricted to only the very lowest notes, or across vast portions of the fretboard, restricted only to the delay path or common to both delay and clean/dry.

[gez]

There is a reasonable possibility that there may be several points where a capacitor value chosen so as not to interfere with guitar frequency response may need to be raised in value, at which point you need to consider whether it is worth your while to monkey around with it. 

I agree Mark, but I'm hoping they've cloned a Boss (or something similar) and used the same numbering for caps/resistors used in their schematics.  Long shot, but you never know...

[TimmyC]

Ok here's the input jack, I think the wire you are talking about is the slightly fatter red one, there are others that go off to the switch and then to the board but this one goes straight to my next pic.



Nearly all the wires then seem to be glued into the board, the fat red one you see on your right is the one from the input jack.





Following the lines on the back of the board, this red wire then goes to the orange blob directly below (I think a capacitor) and it reads 47n with 1100 below that.

The sucking of the low end is when the effect is on and off (as it is not true bypass but I will put in an effects loop) unless changing it to true bypass is another doable job?  You guys may think that this is a lot of work etc. but I really like the sounds coming out of thi pedal and think it will be a worth while investment of time.

Thanks for your help so far, any more input?

Tim

[gez]

Unfortunately, those images are too blurred to be of much use: we'd need higher definition images so as to be able to see colours and chip codes etc.  However, the fact that the input cap is 47n is encouraging as this is the value of the input cap used in a lot of Boss buffers. 

Do you know how to read resistor colour codes?  Immediately after the capacitor, does it connect to a resistor (it will be labelled R followed by a number) and one of the legs of a transistor (three legged, small, semicircular black plastic thing: might be called Q1)?  If so, does the resistor have the number R4 next to it on the board and what are the colours of its bands (yellow, purple, black, orange - followed by something else - by any chance)? 

I'm guessing they've copied a BOSS delay, possibly with some slight alterations.  If the values of the input buffer are the same as in a BOSS then there really shouldn't be any limiting of your bass, and if this is the case then it would be better to get someone to look at the pedal as the culprit(s) could be anywhere (and without a schematic, we're stabbing around in the dark really).  It's possible that the output cap isn't large enough, but that depends on what you're plugging into: is it an amp and if so does it have reasonably high input impedance?

Out of interest, could you write down the codes written on all the chips and post them.  They should be labelled on the PCB (IC something or other) so if you could list them by their allocated number?  It might help.

[TimmyC]

I took some more pics but the quality was not any batter. That capacitor was C2 and 47n, this then goes to R2 not R4 like you suggested it would, with the colours from left to right: Brown Blue Black Red Brown ( it's hard to tell but I pretty sure thats right).  Yes then goes to a transistor named but named Q1.  I am pretty sure its not the same as the Boss as I have played bass through Boss delays and there is considerably less bass suckage on them compared to this one.  If it helps on the manual it says:

Input Impedance 1M Ohm
Output Impedane 1m Ohm
Load Impedance 10K Ohm

Input Equivalent Noise -11dBM or less       
0dBm + 0.775V

Yes I am just playing it through a normal amp.

[gez]

That capacitor was C2 and 47n, this then goes to R2 not R4 like you suggested it would, with the colours from left to right: Brown Blue Black Red Brown

OK, that's only 16k, so it's probably a series resistor to protect the input (there's no resistor between the input wire and the input capacitor, right?). 

If input impedance is quoted as 1M, there must be another resistor connected to the transistor and the resistor you've just identifed...yes?  If so, could you read off its colours?

[gez]

If it helps on the manual it says:

Does the manual have a printed schematic in it?

[TimmyC]

Yeah the next resistor goes Brown Red Black Green Brown, its R4. No sorry there is no schematic in the manual sorry.

[gez]

Yeah the next resistor goes Brown Red Black Green Brown, its R4. No sorry there is no schematic in the manual sorry.

Bear with me.  In the above, does it go as follows:

Brown, Green, Black, Red then a gap then Brown (ie backwards order)

Or is it in the order you quoted but a gap between Green and brown?

It does make a difference.  Reading the values one way gives us 12M Ohms and the other just 15k Ohms.  I've never owned 12M resistors, so don't know what the protocol is for coding them, but it's possible the transistor is FET.  Could you read the code on the transistor and post it here please (we can check the data sheet to find out what it is)?

[TimmyC]

Pm'd you back after reply to first PM, just making sure u got it.

[gez]