Does a DI box affect vintage fuzz/wah pedals?

[DaxLiniere]

Hey gang,
We all know that using a buffered pedal before certain vintage fuzz and wah pedals can (usually) negatively affect the sound of the fuzz or wah, but is that also true when an active DI box with a passive thru is being used?

In other words, if a guitar is connected to a vintage fuzz/wah pedal which is in parallel* with an active DI box, will the signal be affected? (impedance match, etc.)
*the 'link out' socket of most DI boxes is literally a parallel connect to the 'guitar input' socket.
If so, is there any particular DI topology which could avoid or minimise this?

I'm building a switcher device which is intended to not affect the signal in any meaningful way. The idea being that the output of the device (1 in, 5 out (but only one at a time)) is essentially identical to the input (from the guitar), to enable it to be able to be used with abovementioned vintage fuzz and wah pedals.

(Same goes for a buffered tuner output which I'd also like to include.)


Thanks for reading this far, I look forward to reading the forum's sage advice.

All the best!
Dax.

 

[DFischer]

The higher the input impedance of the DI, the less it will effect the interaction with the guitar and fuzz pedal. But note that even quality DI's have a great range of input Z. The Countryman 85 has an input Z of 10Meg, while Radial's J48 has an input Z of 220K. Is 220K enough? That's probably a function of your ears and the fuzz/wah that you are using. 10Meg probably won't have any effect under any normal circumstances.

Also be sure that the guitar output is truly parallel to the input. The Bo Hansen DI is an awesome DI, but the guitar out is buffered and probably wouldn't play nice with a fuzz.

 

[totoxraymond]

The Bo Hansen DI is an awesome DI, but the guitar out is buffered and probably wouldn't play nice with a fuzz.

That's why i disregarded the amp output from my own Bo Hansen DIs but instead added a linked jack.

 

[DaxLiniere]

Thanks for the responses.

I've done some research into those devices you mentioned and see that both Countryman and Hansen are transformer-coupled at the output.
For the switcher unit, I'd like to find a transformerless design, if possible. I guess this can be done with TL072. I can't find the exact input impedance of a TL072, but I did find this useful information, including a comparison table which says JRC4558 is "around 5M ohm" and that TL072 is higher, so I guess that IC would be a great start.
https://www.avaq.com/technology/jrc...ferences-and-how-to-choose#simple-list-item-2

The other restriction I have is that only single-rail (+12v DC) is available, but I suppose there are ways around that, too.

 

[NOON]

Yes, any FET based opamp used as a buffer will have a very high input impedance and be unlikely to affect your effect. Make sure you include ground lift switching, as ground loops can be an issue.

 

[JohnRoberts]

"DI boxes" cover a pretty diverse spectrum of SKUs.

These range from relatively low impedance passive transformer DI boxes that step up the input impedance by the transformer turns ratio squared, all the way up to several megOhm high input impedance active DIs that present very light loads.

JR

 

[DaxLiniere]

Thanks, guys.

I found this post from Jakob (Gyraf) which has me enthusiastic about using the TL07x variant:

https://groupdiy.com/threads/very-high-impedance-direct-box.30607/

 

[Newmarket]

Thanks, guys.

I found this post from Jakob (Gyraf) which has me enthusiastic about using the TL07x variant:

https://groupdiy.com/threads/very-high-impedance-direct-box.30607/

No need to make this opamp specific tbh - any opamp based DI/buffer will have a high input Z - set by the impedance to 0V typically set by a resistor/ resistors to 0V rather than the opamp itself. But, of course, the TL07x is a "GoTo" device. But if interested in lower noise and distortion then there are better alternatives now.

 

[DaxLiniere]

But if interested in lower noise and distortion then there are better alternatives now.

Thanks Newmarket. Yes, DEFINITELY interested. OPA2134?? OPA1642??

The bonus would be that there are 2 outputs in one chip, that way I could do both DI and buffered output for tuner in one package. Everything will be SMD, so no limits on my end.