Triple Wreck Volume Issue

[nickbungus]

Hi All

I have built the Wampler Triple Wreck and it does sound great, the only issue I'm having is that with the volume pot maxed, the overall volume is just below parity.

So I checked all my resistors and caps, thinking I'll have put the wrong value in somewhere.  All seems good.  Anyway any suggestions as to how I could get a bit more volume would be appreciated.

Here's the schematic, pcb layout and my voltages:





DC: 9.27v

TL072
1  3.76
2  3.77
3  3.61
4  0
5  0
6  4.37
7  4.40
8  8.73

TL074
1   4.38
2   9.1
3   4.18
4   8.72
5   4.13
6   4.42
7   4.36
8   4.37
9   4.37
10  4.36
11  0
12  4.37
13  4.37
14  5.23

[Kipper4]

Pin5 of tl072 should be around 4,5v
as shoud pin 2 of tl074
check for solder bridges? jumper soldering?

[nickbungus]

Sorry.  I thought I'd double check as I had my little lads running riot when I took the voltages.

Pin 5 of the tl072 is 4.36 and pin 2 of tl072 is 4.37v

[Kipper4]

Nick Why dont you probe it and see where you lose the volume. that might give you a clue as to where the problem might be. Once the lads stopped running riot that is and If you have any energy left.
Have fun.
Rich

[nickbungus]

Thanks Rich.  If it was a super massive volume drop then that would have been the first thing I would have tried.

Not knowing enough about electronics I also assumed that volume drops could occur genuinely at different stages in the circuit, and then boosted later on.  Does this happen?

Lastly,  after Googling I read that some people had the same problem with the real thing.

As recommended I'll take a probe to it and see if I have an issue or if I can just mod it to give me what I want.

Thanks.

[Kipper4]

Thanks Rich.  If it was a super massive volume drop then that would have been the first thing I would have tried.

Not knowing enough about electronics I also assumed that volume drops could occur genuinely at different stages in the circuit, and then boosted later on.  Does this happen?

Lastly,  after Googling I read that some people had the same problem with the real thing.

As recommended I'll take a probe to it and see if I have an issue or if I can just mod it to give me what I want.

Thanks.

This my friend is a wonderful opportunity for you to learn about op am gain.

Google non inverting and inverting op amp gain calculation.
Bare in mind the effect of the difference diodes to ground makes.
The lose due to the tones stacks?
The diodes in the feedback loop?

I see a voltage follower followed by a non inverting amp with a gain of around 100
Followed by an inverting amp with a gain of? Did you get it yet?
Just a quick calc will tell you where to expect loses.
Of course I guess if you wanted a bit more gain you could hack a 1M pot in the last op amp IC2b.
Feedback loop in the place of the 680k.
Or a series static value resistor with a 1M.
You get me?


I'm no electric genius I'm just a fish flapping around but finding enough water to survive.
I'm hope this helps you not only understand the gain stages and where to expect ac gains and loses. Heck it might help you with future design aspects and consideration.
If I'm speaking out of turn tell me to shut up.

[nickbungus]

This my friend is a wonderful opportunity for you to learn about op am gain.

If I'm speaking out of turn tell me to shut up.

Rich, of course you are not speaking out of turn.  I am so grateful for all the help and advice I get on this forum.  I think the best thing is you never feel dismissed as an idiot and told to step away from the soldering iron.

I am a total novice but I am trying to learn.  I have started to read about op-amps and like you say, this is the perfect opportunity.

Thanks

[Kipper4]

http://www.learningaboutelectronics.com/Articles/Op-amp-gain-calculator.php

do a quick sketch of the info on this page and include the calc
Boom handy quick referance of op amp gains structures for the bench.

[nickbungus]

Ok.  I've ran a probe around and the signal drops from expectable to next to nothing at R10 (47k).  I've checked the resistor -  Yellow Violet Black Red Brown.  I've checked for bridges on the bottom all seems fine.  I've measure the resistance on top and bottom side and I'm getting 47k. 

After TL074 Pin 14, the signal is about 50-60% of parity.

So that leads me to a few questions:

Does R10 affect the tone or does it just affect volume? 

Is it worth experimenting with lesser values at R10?

Would we expect that the volume drops so dramatically across R10?

If there is a mistake, my guessing would be that it lies between R10 and C11.  Does anyone have any pointers as to what I should be looking for?

Any help would be much appreciated?

[PRR]

> Would we expect that the volume drops so dramatically across R10?

Yes. That opamp is an inverter. Signal voltage at pin 13 should be essentially zero. But there's current sloshing through here, which induces voltage at pin 14.

Pin 14 should be twice as loud as the signal at D1 D2.

[Kipper4]

Ok.  I've ran a probe around and the signal drops from expectable to next to nothing at R10 (47k).  I've checked the resistor -  Yellow Violet Black Red Brown.  I've checked for bridges on the bottom all seems fine.  I've measure the resistance on top and bottom side and I'm getting 47k. 

After TL074 Pin 14, the signal is about 50-60% of parity.

So that leads me to a few questions:

Does R10 affect the tone or does it just affect volume? 

Yes the 47k affects the volume. You see that R9 and R10 are in series.
If you go back over to the page I linked to you will see that this clipping amp IC1d is set up as an inverting amp. The gain of the amp is set up with R9+R10 to ground  and R11 in the negative feedback loop.
Which is a gain of ?


Is it worth experimenting with lesser values at R10?


You will also note that there is a cap (C8) with a resistor (R9)>diode to ground.
That cap/resistor combination forms a high pass filter
Followed by another filter made up of resistor R10/cap C9
The diodes to ground will cause the signal lose.

As do any filters.
Google it. Try RC passive filter.

I hope I got this right and your getting it Nick.




Would we expect that the volume drops so dramatically across R10?

If there is a mistake, my guessing would be that it lies between R10 and C11.  Does anyone have any pointers as to what I should be looking for?

Any help would be much appreciated?

It might be worth experimenting with R16 . Try a lesser value 220k maybe ,unless it messes up the input impedance of the buffer IC2a.
It might get you where you need to be. Providing everything is as in the schematic. I don't know worth the cost of a few resistors.

[dschwartz]

Make r16 smaller and/or make r19 smaller and/or make r18 bigger..
That will make up some volume..

[nickbungus]

Thanks guys.  There's loads there for me to play with.  Which is what it's all about.

[nickbungus]

That opamp is an inverter. Signal voltage at pin 13 should be essentially zero. But there's current sloshing through here, which induces voltage at pin 14.

A lesson learned.  This guy explains it perfectly at around the 19 minute mark!

[nickbungus]

Just to conclude this thread.

1.  Thanks everyone for the advice and education.  Its massively appreciated.

2.  Results - I socketed R16 and tried a 220k.  Seemed much better - above parity but I experimented with a 100K.  Next time I can crank up my gig amp (Marshall MA100C) I'll try both the 220k and the 100k.  I reckon I'll end up with something inbetween but its been a good adventure.

[Kipper4]

250k on board trimmer in the place of R16 maybe if there's room.

[J0K3RX]

Shouldn't need to manipulate this circuit at all since it has been 100% verified 100,000 times over... I have built the TW quite a few times without any issues other than I don't like the boost section which I leave off anyways and I don't see it in this layout so no worries there. I haven't gone over this layout but, right away I see things that I try to avoid like the grounding completely encircling the board. Another thing is that the diagram shows all of the 1uf caps as being electrolytic capacitors which they should not be. The 1uf caps should be box film or mylar film type... If you are using electrolytics for the 1uf caps I would start replacing those with the correct type and while you're at it make a cut in the ground trace somewhere around the perimeter of the board so the circuit doesn't live inside a ground loop... 

Since you said that you probed the signal and noticed a significant drop at R10 I would start by replacing both C9 and C11 with 1uf box or mylar caps, even 470n should work alright if you don't have any of the 1uf on hand...

[nickbungus]

Thanks Jok3rX.

If you look at the etched PCB layout, the ground loop has already been broken.  This is what I used.

Ok, I've got plenty of mylar film caps so I'll give it a shot.

And yes, the boost section is awful.  The layout comes from here.  A layout for the boost section is also given.  The ground loop is also discussed.

[J0K3RX]

If you look at the etched PCB layout, the ground loop has already been broken.  This is what I used.

ok well duh...     That's my bad.. I didn't even see that because my browser was not displaying the entire picture, only the 2 boards on left side. That etch looks good.

[maiko]

I hope no body minds me doing this

Its just i built it recently and have the volume issue.      bypass is way louder that the effect even when the vol is maxed out.

Tried replacing the r16 still the same.   however i noticed that if the vol on my guitar is half way the effect does not change. and when i switch to bypass the clean is now lower that the effect.   When i turn the vol on the guitar up its back to the problem.

What does R1 1meg resistor do?  is it just a pull down resistor?