Lovetone BrownSource. Is the Schem legit? I built it and it doesnt work.

[ulysses]

hi guys,

i have built plenty of pedals in the past so i do know what i am doing to an extent

i took the latest and greatest schem for the brown source and made a pcb layout for it and then built it.
http://i7.photobucket.com/albums/y278/veroboard/Lovetone%20Brown%20Sauce/Lovetone_BrownSource_SCHEM_V5.gif

volume works, tone works, but drive only gives a slight volume boost. very strange.

i read many posts about this pedal on the board and it seems no-one can get it to work, with several people saying it produces a slight volume boost at best.

can anyone confirm that they have built a brown source and it sounds like the one on lovetone.com?

i tried increasing the 47n cap to 4.7uf which was suggested by a board member, and does make the circuit distort, but it doesnt sound anything like the pedal on lovetone.com

is this schem a red herring?

any help greatly appreciated.

thanks
ulyssus

[ulysses]

by the way im using a texas instruments RC4558P dual opamp. the schem says "dual-opamp, maybe 4558"

if i used a tl072 do you think it would make any difference?

cheers
ulysses

[ulysses]

im also using an 18K resistor in position R13 and NOT 22K as a suggested substitution.

do people purposly post the wrong schem for copyright fear but leave hints about the correct parts to use??

thanks
ulysses

[cd]

Just looking at the schematic, there's no reason it shouldn't work.  The signal goes: emitter follower > inverting gain stage > tone controls > non-inverting gain stage > output

Audio probe the output of the 1st gain stage, what do you get?

[ulysses]

hey cd

when i do that i still get the same output level as before. with the drive pot working, but the tone and vol pots + tone switch dont work.

i dont get any distortion at all, just a slight volume boost.

thanks
ulysses

[alteredsounds]

hey! I built it a few weeks back and it works fine.  Not really anything to great though I didnt think.  Cheers.

[ulysses]

hey alteredsounds,

would you mind posting the pcb design you used please?

also, can you tell me what types of caps you used for the different values? maybe a photo of your board?

cheers
ulysses

[stm]

Looking at the schematic I can say the values indicated there make no sense:

1) R6: this 220 ohm resistor is too much of a load for the previous emitter follower stage.

2) C3-R6:  Starts rolling bass frequencies below 15 kHz !  I would believe this better if the rolloff frequency were between 200 and 700 Hz, meaning C3 should be at least 1 uF.

3) The C5 cap in parallel with the gain pot and 1k resistor produce a high frequency rolloff that starts at 185 Hz.  This should rather be near 5 kHz or higher, thus C5 should be better at 1 nF.

4) The output filter cap C13 combined with R14 produce a high frequency rolloff near 22 kHz, which is basically unnoticeable.

Points 1, 2 and 3 explain why you are having such a little gain.
All of the above indicate the component values are not making sense, or that I am missing completely the real operation of the circuit!

Remember: NET = not entirely true.

[alteredsounds]

Thats the one with the rotary switch right? I did it from Torchy's layout and some info from some threads in here, not overally impressed though tbh

[ulysses]

hey stm,

thanks for looking at it for me.

i increased c3 to 1uf and it does distort, unfortunatly the distortion sounded nothing like the demos on lovetone.com

i then replaced c5 with a 1n5 cap (i didnt have a 1n in my box of tricks) and it started to sound like a fuzz pedal instead of an overdrive pedal will try with a 1n later today.

what would you suggest i use in the place of R6?

thanks again for your help bro.

cheers
ulysses

[George Giblet]

> do people purposly post the wrong schem for copyright fear but leave hints about the correct parts to use??

In general I'd say no.  When you trace a circuit from a photo it's sometimes hard to read the values because shadowing, jpeg artefacts, or other crud distorts the image or the colours.  You see one thing but your engineering judgment tells you another - ussually you try to merge what you see and what makes sense to make a judgement.  Often that is more accurate than what you see!

Another factor is that many boutique effects are poorly designed.   Engineers would see a lot of these designs as "amature hacks".   When you look at such circuits you thing "that's crap"  but often it turns out to be what the actual circuit is.   One example:  stm is criticizing the 220R R6 value, from an engineering perspective this is rightly so (!!!), but I would not be surprised if it is that value.


Some History:

I know for a fact in this instance that "analogguru" did make an effort to get this schematic right.  BTW analoguru's traces are more trustworthy than most - but I'm sure he will admit it's easy to make mistakes.    Many people had input on this and the result wasn't convincing to analogguru (or myself).   Mikeb had some PCB photos and analogguru forged the current schematic from those and the existing schematics.  Mikeb pulled the pcb pic offer quite quickly and I never got to see them.   At the time I wasn't entirely conviced the final schematic was correct (because some things don't look right, as stm has pointed out).

From memory here' what I thought:
- I have a suspicion there may be an issue with 33n caps vs 3n3 caps.
- R14 may well be 2.2k.
- R6 ?
- At one point I susected the switch contacts were out of whack ie. the contacts were interpreted wrongly during the trace.

[ulysses]

hey george,

thanks for your reply.

i suspect that c5 needs to be 3n3 not 1n. when i use a 1n5 cap in its place, it sounds like a fuzz box. when i use a 12n (the next lowest cap in my box of spares) is sounds better than the 33n but still too muddy. becasue it was a public holiday today i couldnt go any buy the parts i needed.

i think the wiring diagram in the schem i used is incorrect. i can only get two noticable different sounds out of it. when the tone switch is set to off it passes what seems like the full tone (tone pot does not work when tone switch is set to off). when the tone switch is set to any of the three other settings i have control over the tone pot but all three tone switch settings sound the same.

i now have a copy of those pcb pics. c3 and c9 are different types of caps to the rest of them. which makes me think that c3 is definatly wrong.

will try and work out the switch wiring.

cheers
ulysses

[Gus]

The web is a funny place

Years ago(1999) a friend brought over a cheese source to be fixed (broken switches).  He needed it back in a few hours. I traced the circuits in about a hour, I like to have more time to check.
When I posted about them I noted the schematic could have a problem.   I never built a BS.
  R.G. traced a difference in a big cheese.  IIRC I asked if the diffferece might be real because the cheese and CS might have a small difference at the gain setting a work somewhat the same.

Then like the web does what it does well things get twisted with time.

[Doug_H]

The web is a funny place.

IMO the crime is that there is not an archive of what happened in the mid-late 90's. New people come in and have no place to look to find out "who did what when" kind of info. Unless you were around & involved with this stuff then, you have no way of knowing. So things can get attributed to the wrong sources and etc. And as for me I regularly shoot myself in the foot taking stuff off my site, only to see it resurface later somewhere else or ideas from it come up with no attribution. It's a learning process, I guess...

Re. the schematic: I would isolate the follower and gain stage and get that working first. As drawn I don't see any big issues with it. I don't agree with STM that R6 is a problem at 220 ohm. It's not a shunt, it's a series resistor that determines the gain (along with R7/VR1) of the non-inv op amp stg. 33n may be excessive for C5 but with fuzz boxes there could be a method to the madness. Be careful with the rotary switch wiring though. That could be a source of confusion.

Doug

[Jay Doyle]

IMO the crime is that there is not an archive of what happened in the mid-late 90's.

Good God. Has it really been that long? 

Great point.

[ulysses]

after looking at the switch wiring i think it is actually correct, i now think that c8 c10 and c11 are wrong, or maybe just c10 and c11

from the schematic i linked to in my original post you can see that the switch switches between caps creating a low pass filter.

from what i can see it uses two caps and one resistor to create the low pass filter.

tone switch position 1 = 33n to 3k9 to ground
tone switch position 2 = 33n + 33n to 3k9 to ground
tone switch position 3 = 33n + 22n to 3k9 to ground
tone switch position 4 = 33n to 3k9 to ground (same as position 1 but enables tone pot)

position 1 does sound like position 4 when you play.
position 2 does sound like a low pass filter when you play and the tone pot works.
position 3 sounds the same as position3 when you play and the tone pot works.

could someone with a low pass calc figure out the freq's that are being passed so i can figure out the correct caps to use for c8 c10 and c11.

thanks
ulysses

[ulysses]

i just had a thought. when c10 and c11 are in use via the tone switch (switch positions 2 & 3) , c13 also gets used when the tone switch is in positions 2 and 3.

any thoughts on a correct value for c13?

thanks for your help guys.

cheers
ulysses

[George Giblet]

Your comments agree with how I see the circuit working as it is drawn.

Position 1 and Position 4 should sound about the but there will be a level drop in position 4 (actually 3 on the schem numbers).

I bashed out some numbers for C7, C8, C10, C11 and to be honest they don't look "bad" as such.  Unfortunately that doesn't mean they are correct, just that they are in a useable ball-park.   The C10 and C11 values will only give a subtle change to the voicing, at a guess the subtle change is intentional.  Given that the output LPF is also being switched the LPF should be contributing to a change in sound also, making the sound more different than just the change of C8, 10, 11 alone imply.  The tone circuit is a mid-notch with a variable tilt between low and high (the amz site has some stuff on this if you want to look, don't know where abouts though).  Looking closer at the circuit there is not mid-notch behaviour, only high/low tilt; in fact in position 2 there is a mid hump instead of a notch.

It's not possible to speculate the correct values through calculations.  All I can say is:
- if you make any of the treble caps (C8, C10, C11) smaller you will get more of a mid notch
- if you make C7 larger you will get more of a mid-notch.
- if you space the treble cap combinations wider you will hear more difference.
- if R14 or C13 were correct perhaps you don't need to change C7, C8, C10, C11.

C13 is hard to judge.  It could be anything from it's current value upto 330nF or so.   Have you confirmed R14's value from the photo's?  that would be a better part to vary.

[ulysses]

thanks again for your reply george.

i increased c13 to 100n which changed the high pass from 22khz to around 7khz which took out the opamp 'sting' (square distortion) but didnt make it sound much better

unfortunatly noone knows the correct input gain/distortion part of the circuit. the way its written up in various schems it only gives a volume boost. increasing c3 makes it distort, but even with the tone section bypassed it sounds like any other shitty opamp distortion.

i think im going to give up on this one untill someone comes up with a schem that sounds like the demos on lovetone.com

untill then ill just have to crank up my jtm45 despite my wife and kid.

thanks again to everyone who chipped in.
ulysses.

[glava@bredband.net]

anyone found any correct values of components yet?