Impendance vs. buffers - how to make the perfect solution.

[jakenold]

Dear fellow DIY'ers.

I am going to build a couple of pedals for some of my friends, in particular an overdrive that I've pieced together from various commercial effects. However, there seems to be a problem.

When I plug my guitar into the overdrive and from there into my SuperReverb, I get a smooth, big and warm tone. Like a very fat stratocaster sound that I like very much. When I put my KORG DT-10 tuner or one of my buffers in front of it, I get a very piercing tone - not in a bad way, it actually sounds pretty darn rad, but I'd like to be able to get the other sound as well.

The KORG has an output impedance of 100 Ohm. How should I modify my overdrive, so it can retain that fat, apparently "loaded" sound.

Kind regards, Jake

[Paul Marossy]

It kind of sounds like the Korg is not meant to be plugged into a guitar effect. It's seeing a high input impedance on the output, and it was probably designed to go into a mixer or something, not something with a Hi-Z input. That's my theory, anyhow.

[jakenold]

Hi Paul.

I don't think that's the case. The DT-10 is their stomp box tuner, which lots of guitarists use. It was just the first buffer I tried in front of the effect. It would practically be the same if one of my friends had a BOSS or T-REX effect infront of my overdrive.

I thought about installing a buffer infront of the effect and lowering the input impedance from 1M ohm (the first resistor to ground). However when I tried with a 400Ohm resistor to ground in parallel with the 1M ohm, it just lowered the volume of the effect.

Therefore I need some "how to" advice.

Kind regards, Jake

[Paul Marossy]

Oh, sorry, I didn't notice that is was a tuner. 

OK, then, I would probably take the shotgun approach and run it in parallel instead of in series. But, that's me. Maybe there is some other solution, but I'm not sure what it is... 

[jakenold]

I'm keeping it out of my regular chain.

But that still doesn't keep my effects from being placed in series with another effect that ALSO has a buffer!

[Paul Marossy]

But that still doesn't keep my effects from being placed in series with another effect that ALSO has a buffer!

Hmm... this is problematic, isn't it?! I hope someone else has some ideas, I'm not coming up with any at the moment... 

EDIT: An idea... you could maybe try to build Craig Anderton "Effects Order Switcher" from his book called "DIY Projects For Guitarists".

[db]

Is it perhaps the case that the tuner is doing the "right thing" and providing a high Z input (as you would expect) and that your home brew effect is actually slugging the guitar when it is first in the chain (even though it produces a nice fat sound)?

And perhaps also, the assumed low input Z of your effect is playing havoc with anything else trying to drive it?

[Ben N]

Continuing with db's thought, why not just put the OD ahead of the buffer, as you would wth a Fuzz Face? It is hard to really answer your questions without knowing something about the input stage of your overdrive.

Bn

[Meanderthal]

 Yeah, it sounds like the buffer is doing its job- restoring high end and clarity.  Like Ben said, think Fuzz Face- your overdrive might be happiest when connected directly to your guitar.

[Gus]

The following is a guess at the circuit input from the posts

The circuit reads like it might be a summing junction input type circuit like an inverting opamp but the input resistor is the guitar mess like a ff circuit.  It also reads like it does an EQ because of the feedback like a FF(the first stage interaction with the guitar".

If so if you add a buffer with a low output Z. The gain will be very high and you might get a lot of highs because of the highpass filter formed if you use a input cap.

  It reads like you might be able to add a "build out" resistor(try a 10K to start) in series with the output of the Korg for one part of the problem

BUT you will not get the EQ because you will not have the complex Z mess of the guitar working with the feedback causing an EQ.

Look for posts about wha buffers with higher output R to work into a FF.

[Ben N]

Based on Gus's assumptions, you might look into the inductor-based pickup simulator at AMZ as a possible solution.

[tommy.genes]

Based on Gus's assumptions, you might look into the inductor-based pickup simulator at AMZ as a possible solution.

http://www.muzique.com/lab/pickups.htm

-- T. G. --

[brett]

Is it perhaps the case that the tuner is doing the "right thing" and providing a high Z input (as you would expect) and that your home brew effect is actually slugging the guitar when it is first in the chain (even though it produces a nice fat sound)?

Can I suggest that the "right thing" is the WRONG thing?  Who wants skinny, bad tone?
There was a good reason that Jimi Hendrix played through a high capacitance, tone-dampening, "curly" cable?
The longer I play, the more I dislike high input Z buffers. IMO 220k is plenty for any guitar (max 470k).  It might be that old guys and girls who have trashed their ears are using buffers to get back some of what they have lost because of damage.

cheers

[Paul Marossy]

Can I suggest that the "right thing" is the WRONG thing?  Who wants skinny, bad tone?

I personally like a fat, smooth sound. I play my neck pickup 99% of the time. I can't stand too much treble, but some people seem to be obsessed about hearing every frequency up to 22kHz. That must be why people true bypass their CryBaby that already has a sufficient Hi-Z buffer in it? There are times when an old effect will suck tone real bad, even bad enough for me.

Uh, I guess that was a mini-rant... 

[db]

Is it perhaps the case that the tuner is doing the "right thing" and providing a high Z input (as you would expect) and that your home brew effect is actually slugging the guitar when it is first in the chain (even though it produces a nice fat sound)?

Can I suggest that the "right thing" is the WRONG thing?  Who wants skinny, bad tone?
There was a good reason that Jimi Hendrix played through a high capacitance, tone-dampening, "curly" cable?
The longer I play, the more I dislike high input Z buffers. IMO 220k is plenty for any guitar (max 470k).  It might be that old guys and girls who have trashed their ears are using buffers to get back some of what they have lost because of damage.

cheers

That was my point really.  That's why I put "right thing" in quotes.

[Gus]

Jake

  what is the first stage?

  A npn or pnp transistor with a feedback/bias resistor from C to B?

  A  fet with a feedback bias/resistor Drain to Gate?

A resistor from D to G or C to B is not just bias it also is feedback

[newbie builder]

I'll suggest the easy way out- build an A/B box in a tiny enclosure. That's what I plan on doing to keep my DT-10 out of the signal chain. It's an easy fix.

[jakenold]

Hi guys!

Thanks for the great response! I just came home from the Paul Gilbert show here in Copenhagen, Denmark, so excuse me if I sound a little BEST-NIGHT-OF-MY-LIFE-ish 

The effect I am making, has the same input stage as Doug Hammond's Highway 89, but I "pasted" the RAT-circuit in instead of the original. Very interesting tones.

I do believe that it loads down the signal in some way. The DT-10 is just doing what it is designed to do - what I to make an input buffer (or something like that), that has the same Z as my Strat (just an example), no matter of I plug in the guitar or the DT-10. I want it to sound equally awesome, no matter where you place it*

*An Utopian idea, but bare with me - if it sounds "the same" with or without the DT-10 in front of it, I'll be more than happy. Sadly I haven't got the sufficient knowledge to design such a circuit yet.

Kind regards, Jake

[mac]

The Hwy89 has Brian May treble booster first. Very low Z input at first glance. As said above it sounds like FF problem. Maybe replacing the 1k at the input with a pot may help. Just a guess.

mac

[Ben N]

There are plenty of people here who have made the Highway 89, or who presumably have a BMTB and a Rat. Has anyone replicated this issue?