Deep Blue Delay Resistor Replacment.

[nguitar12]

I am building Deep Blue Delay as shown in the above diagram.
However I don't have 180k and 360k (R2 & R3) in hand.
Can someone please suggest a possible replacement value for those resistor?
Is there any side effect if those resistor is replaced?

Thanks in advanced.

[Kipper4]

Could'nt you make up the values by using series or paralell resistors ?

[anchovie]

It's an inverting amplifier, set up to give a gain of 2 (360K/180K). C1 forms a high-pass filter with R2 and C16 forms a low-pass filter with R3, so you don't want the values to be wildly different without adjusting those capacitor values. You could probably get by with R2 = 150K/R3 = 330K or R2 = 220K/R3 = 470K. Alternatively, make the 180K and 360K by using smaller resistors in series (150K + 33K, 100K + 82K, 330K + 33K, etc.).

[antonis]

You can replace them by others with the same ratio (1/2) but you'll have to also alter C1 & C16 caps if you want to sustain the R2*C1 and R3*C16 products...
(for not altering the High and Low cut-off frequencies..)


edit: Beaten by anchovie's type and connection speed...

[nguitar12]

Thanks all. I have a very tight 1590a layout so I don't want to make them two resistor.
I will order some 180k/360k resistor then.

[nguitar12]

Just noticed that I have a 150k/300k and 220k/470k couple. Which pair will work better and how they affect the FP/LP filter?

[antonis]

150k/300k pair should work better (less deviation from original values) and will affect both filters cut-off frequency by an amount of aproximately 20% (150/180 = 300/360 = 0.83)..

Meaning that you will shift the pass band by 20% at BOTH f_low and f_high frequencies with almost the same (log graph) bandwidth...
( in absolute values you will widen the bandwidth but I think it requires another analysis level - and I'm not the most appropriate person .. )

Original values: 41Hz to 9.4kHz (180k & 360k)
Modified values: 48Hz to 11.3kHz (150k & 300k)

[samhay]

R2 (180k) also sets the input impedance. The difference of 150k vs 300k may mater if the effect is driven directly by a guitar with passive pickups.

[nguitar12]

R2 (180k) also sets the input impedance. The difference of 150k vs 300k may mater if the effect is driven directly by a guitar with passive pickups.

So do you mean that the overall volume will increase when the pedal is turned on?

[samhay]

You may get some 'tone sucking'* when the effect is on, if it is the first thing your guitar sees in the chain. 150k input impedance is a little low by contemporary standards - roughly / arguably 1M. If you have any buffered / always on pedals before the delay then it is unlikely to be an issue.

* loss of high frequency response rather than volume drop.