Electronics guys... Circuit layout help please!

rikus · 2011-12-29T18:39:18+00:00

I need some advice with a problem that I'm having and which I suspect is due to the layout. I built a buffer pedal a while back based on this circuit. I...

Electronics guys... Circuit layout help please!

Nicholas-L

:goodtimes: :dance:

rikus

And here it is. Working perfectly thanks to you guys.

This is the old one... veeeery big:

New one:

Side by side... :dance:

This morning I changed the little ceramic cap on the input side with a beefier film cap... I don't know if I can hear a difference, but it looks nicer!

Nicholas-L

NIce 8) looking good there

Gearhead

Change the electrolytic as well, then you'll hear. This is your achilles heel at the moment, I reckon.

rikus

Thanks Nicholas.

@Gearhead... thanks for the tip, but I don't know enough to tell a good electrolytic from a bad one... any suggestions? Would Yebo for example stock better quality ones or would I need to shop online?

Nicholas-L

If you want seriously better you might start with Rs Components or if you wanted to do branded names like sprague you'd have to source it on ebay, but maybe someone on the forum has an extra one for you. Yebo typically stock your all day everyday components, not really aimed at the tone/sound fanatic who likes the "magic" of certain caps.

Nicholas-L

uhm GH did you mean change the cap from say 10uF 16V to say 10uF 100V (physically bigger cap, same value) or change the cap value?

Gearhead

Same value cap same spec, only metallised polyester or some other high end construction. Price is a dead giveaway for quality on these things, and the most you are going to pay is about R40. Join in on a group buy from TubeDepot or something and you can open up the sound of your pedal audibly.

AlanRatcliffe

Gearhead wrote: Same value cap same spec, only metallised polyester or some other high end construction.

What about tantalum electrolytic caps? Small, polarized and fine at the low voltages used in most pedals.

Gearhead

I don't know if I would hear the difference or which one is better. My point was actually if you're going to go through the trouble of sourcing, paying for, collecting and soldering in your cap you might as well do yourself the favour of getting the best you can. Same like you don't build your own guitar using second hand Samick/Ritmuller/SantaFe parts. The location of this cap is in the signal path, probably right at the beginning of the signal chain.

rikus

I gotcha! Thanks for the info. I might just do that. Then I can get some nice switchcraft jacks too!

Nicholas-L

Cool man

Nicholas-L

oh wait cap constructions.... I see now yes indeed I do.

ezietsman

Alan Ratcliffe wrote:
Gearhead wrote: Same value cap same spec, only metallised polyester or some other high end construction.
What about tantalum electrolytic caps? Small, polarized and fine at the low voltages used in most pedals.

They also tend to explode and set fire to the rest of it when things go wrong ? Prob not at the low voltages. I was told to stay away from them unless I REALLY have to use one.

makepeace

Gearhead wrote: Change the electrolytic as well, then you'll hear. This is your achilles heel at the moment, I reckon.

Hmmm. Are you sure about this GH?

It is to my knowledge that in this case, the only non-electrolytics available for choice are tantalum and ceramic. Metalized polyester and other film caps of this value will be physically too large for the enclosure being used (for eg, i have a 400V 10uF Solen cap that is about the size of 50uF 600V sprague, which you would have to put in a blender to fit one into these tiny enclosures.

Out of the remaining candidates, electrolytics are more linear than tantalum and ceramic, their only disadvantage is that their values drift over time. Tantalum capacitors are also reported to sound 'bad' in audio applincations, as with ceramic. However, I doubt that with either of these choices anybody will notice much difference. It has been proven that capacitors of different construction do have their merits in audio applications, however they are never going to effect miracles.

My advice would be to get a high quality electrolytic with a higher voltage rating.

Gearhead

No of course I'm not sure, are you? There's more to that value than meets the eye. The original schematic comes from here. In this one, Jack Orman tries to get as much signal out of the four opamps as possible through two 10uF caps. If and only if you use up all of this current by feeding into multiple low impedance effects, you need 20uF. Chances are you won't, as OP has realised when he used only one opamp. I don't even think he needs 20% of that, but we can only know that if he would be so kind as to post what in his effects chain after this buffer.
So assuming he does not need all that current, he can go for a smaller cap. The mod to the original circuit would require 5uF, but I reckon 2uF would more than suffice. That is four Orange Drops of .47uF and you're done.
My advice would be to even try less than 2uF. If the cap is too small for buffer plus following stage, you will hear it as decreased bass response - then you'll know you need to add more.

rikus

Gearhead wrote: No of course I'm not sure, are you? There's more to that value than meets the eye. The original schematic comes from here. In this one, Jack Orman tries to get as much signal out of the four opamps as possible through two 10uF caps. If and only if you use up all of this current by feeding into multiple low impedance effects, you need 20uF. Chances are you won't, as OP has realised when he used only one opamp. I don't even think he needs 20% of that, but we can only know that if he would be so kind as to post what in his effects chain after this buffer.
So assuming he does not need all that current, he can go for a smaller cap. The mod to the original circuit would require 5uF, but I reckon 2uF would more than suffice. That is four Orange Drops of .47uF and you're done.
My advice would be to even try less than 2uF. If the cap is too small for buffer plus following stage, you will hear it as decreased bass response - then you'll know you need to add more.

Wow, that's a lot of info to try and digest! ?

I'm using the buffer in my signal path after a bunch of true bypass pedals and in front of my low impedance volume pedal. The idea is to avoid tone suck from the volume pedal due to impedance mismatches when the all the TB pedals are off. The only pedals after the buffer are my EB Jnr volume pedal and my Nova Delay.

The buffer at the moment is virtually transparent to my ears (comparing straight into the amp vs guitar -> buffer -> amp). Using the buffer in the signal chain makes a very audible difference avoiding tonesuck from the volume pedal; gives me the sparkle back to the highs.

In my mind it's mission accomplished, but I've jumped aboard the tubedepot order to replace the current electrolytic with a better quality one (a sprague atom) just to make sure that all my components are good quality.

Gearhead

Do yourself a favour: also order two orange drop .47uF caps while you're at it. Does not break the bank.

The other good thing would be to take an ohm meter and measure the resistance to ground of your volume pedal. Alternatively, you can look up the manufacturer's spec on it. It is not hard to calculate the low rolloff of the combination of cap and impedance. Lemme quickly find a link for you to explain....

rikus

The orange drops would then be used in stead of the electrolytic? And we're interested in the resistance to ground in order to determine the required capacitance?

Gearhead

Look here and focus on the schematic on the right. The C is your output cap and the R is the resistance to ground of your volume pedal. Now fill in 10K (which would be a typical low impedance for our purposes) and 0.47uF (which would be your cap). You get a frequency that is way low enough for guitar. Way.
The calculation is slighty oversimplified, but the results are close enough to show the point.