(http://3.bp.blogspot.com/-bEMBMvJwA5Y/TwrbbnpmzoI/AAAAAAAAAbw/EQ70PKQOFes/s1600/seaUrchin_Schematic.gif)
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.
Could'nt you make up the values by using series or paralell resistors ?
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.).
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... :icon_redface:
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.
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?
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 .. ) :icon_wink:
Original values: 41Hz to 9.4kHz (180k & 360k)
Modified values: 48Hz to 11.3kHz (150k & 300k)
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.
Quote from: samhay on May 08, 2015, 11:17:11 AM
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?
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.