33174 based echo unit - help me tweak input impedance

[Piamp]

Hi!
I'm building a echomatic (a small unit to turn a tape deck into an delay)
Here's the schematics :
http://experimentalistsanonymous.com/diy/Schematics/Delay%20Echo%20and%20Samplers/Echo-matic%20cassette%20delay%20page%202.gif

It works but i have a problem with input impedance. I think it's too low, i loose a lot of treble when i plug a guitar straight into it, whereas sound is ok if i use a buffered pedal between the guitar and the echomatic.
I'm a tube amp guy, don't know a lot about IC ! Is there a simple way to get a higher input impedance ? Or should i use a jfet follower?
Thanks !

[gasboss775]

Looks like R1 sets the input impedance at 10K, definitely a bit low for guitar use. You could try increasing R1 to 100K but you also need to increase R2 to 1M, to keep the opamp gain at X10.

[PRR]

Try this. It has less impact on hiss than raising R1. The added inversion *may* not matter?

[Piamp]

Thanks !
I cannot invert the signal as it is recombined... It would cause phase cancelation ?

[gasboss775]

PRR is right that increasing R1 & R2 will increase the hiss, also I don't think the recombined signal will cancel due to the fact the delayed signal via the tape wouldn't be in phase with the outgoing signal to the tape anyway, so using the +Ve input of the opamp is probably the better choice.

If you do decide to go with my suggestion C2 should also be decreased to 10pF.