Alternative Value Difficulties

Ok, you got your soldering iron and nothing is going to hold you back, but you have no clue where to start or what to build. There were others before you with the same questions... read them first.
Post Reply
User avatar
trad3mark
Resistor Ronker
Posts: 338
Joined: 08 Mar 2009, 16:55
my favorite amplifier: Vox Valvetronix Series
Completed builds

Super Hard On
Fuzz Factory
Aenima/Torn's Peaker (2 in 1 box with toggle switch)
Valvecaster Deluxe (Boost before VC)
Proco Rat (Mod to power jack, and input cap changed)
87% PillowStone
87% GlassJaw

Location

Ireland (Dublin/Waterford)

Been thanked: 1 time

Post by trad3mark »

Hey all,
Just a quick question on using alternative values for things. We've all had those builds where we need to use substitute values. I've done ones where the substitutes have been really close. Things like 12k resistors replaced with 15k resistors, or 20nF caps replaced with 22nF caps. As i'm sure a lot of you will agree, a lot of the time, if the values are close enough, it won't really make much of a difference a lot of the time.

My question is, what if almost the entire board were substitutes? Obviously, the sound will be noticibly different. This may be tone, volume, fuzz amount etc etc, the list is endless. But, will it always still work provided the values are pretty close?

I'm just about to debug a Green Russian BMP build, but there's a lot of alternative values. Most are REALLY close, as described above. But there's a few i'm not sure about. The furthest one out in terms of resistors is a 470k replaced with a 600k, or a 2.2m replaced with a 3m. It should work really, right?

I'm so confused.... :scratch:

User avatar
willc1968
Breadboard Brother
Posts: 50
Joined: 05 May 2009, 18:13
my favorite amplifier: Kustom K 200 A-4 in red
Completed builds

kay fuzz, clark fuzz, ea tremelo, green ringer, tremelus lune, a few big muffs, fuzz face and factory, sft, woolly mamoth, a bunch of tonebenders and many more that need to be boxed

Location: philly
Has thanked: 13 times

Post by willc1968 »

when i want or need to have resistor values dead nuts on i just get out the multimeter and try to find 2 resistors or sometimes 3 that will work in series. finding a parallel equivilent is also an option and is sometimes easier and neater because using 2 components where only 1 is allowed for can get ugly at times. hope this helps. will

earthtonesaudio
Transistor Tuner
Posts: 1256
Joined: 28 Jan 2008, 05:00
Completed builds

Metal Simplex, Fuzz Factory, two Fab Echos-modded, Noisy Cricket, Earth & Space Wah, TS-7-modded, passive xover/splitter box, opamp fuzz

Location: Bloomington, Indiana
Has thanked: 11 times
Been thanked: 72 times

Post by earthtonesaudio »

There are places where it matters more, like transistor biasing. If you don't have the proper values, it may be beneficial to scale the other values to match what you do have. For example if a transistor's base is biased by 10k and 100k resistors, you could substitute 47k and 470k, and end up reasonably close to the original bias point. Of course then the frequency response is changed, but cap tolerance is generally much worse than resistor tolerance so that part is a bit of a roll of the dice anyway.
rocklander wrote:hairsplitting and semantics aren't exactly the same thing though.. we may need two contests for that.

User avatar
JiM
Diode Debunker
Posts: 920
Joined: 11 Mar 2008, 23:56
Completed builds

Completed builds :
Proco Rat
MXR MicroAmp in a volume pedal
TubeDriver (w/ NoS russian tube and big muff tone contol) + Phase 45 (w/ univibe cap ratio)
Dallas Rangemaster (w/ noisy OC75, negative ground)
SubCaster tube booster (w/ NoS russian tube, PtP)
Hot Harmonics
Music From Outer Space SubCommander in progress
Crackle Not OK
Simple bass blender in a 1590A
Bazz Fuss with a photo-darlington

Location: France
Has thanked: 25 times
Been thanked: 30 times

Post by JiM »

In DIY fashion you can take some time to test parts for actual value within tolerance.
For example, a 10k 10% resistor will more efficiently replace a 12k if it's close to the max value (i.e. 11k) rather than the min.

[Slightly off topic : i remind an experienced engineer saying that back in the day, a 10% resistor was always more than 5% off the specified value, as these were factory-sorted ... nowdays i'll expect a nice gaussian curve.]

Anyway, for a Big Muff it doesn't matter much, as there were quite a lot of variation in the official schematic along the years ...
I only give negative feedback.

Post Reply