What effect is used early in LA Woman ?

brett · July 17, 2006, 10:53:45 PM

Hi.
There's a very cool fuzz used early in the song. Slightly "crackly" and gated. Sounds like a milder version of the FZ-1 used in "Satisfaction". Any ideas?
Thanks.

Herr Masel · July 18, 2006, 02:03:16 AM

I think Robby Krieger used the fuzzrite, which is not mellow at all compared to the tonebender on satysfaction! The mellowness could come from the fact that he played with his fingers (no pick), and maybe rolled off volume/tone on the guitar. I really like the way he uses fuzz.

RedHouse · July 18, 2006, 09:35:35 AM

FYI, the Satisfaction fuzz was not a Tonebender, it was a Maestro FZ-1

jrc4558 · July 18, 2006, 02:45:16 PM

It seems to me that first off you would need an SG with P-90's

brett · July 19, 2006, 01:59:53 AM

Hi
The Fuzzrite looks very interesting. Will build one ASAP.

It also looks ripe for experimentation, as it was obviously designed for old, low hFE transistors. Hence those whopping 470k resistors on the collectors. I might knock them down to 220k or put a pot in there and see how low they need to go for a pair of modern 2N3904s.

thanks

Herr Masel · July 19, 2006, 12:32:07 PM

Quote from: brett on July 19, 2006, 01:59:53 AM
Hence those whopping 470k resistors on the collectors. I might knock them down to 220k or put a pot in there and see how low they need to go for a pair of modern 2N3904s.

Do you mind to explain please what you mean by this? What do the resistors do to the collector of a low hFE transistor?

EDIT: http://www.diystompboxes.com/smfforum/index.php?topic=47264.msg348591#msg348591 ok I saw the other thread!

brett · July 19, 2006, 09:02:13 PM

Hi.
The collector resistor is important in this circuit for at least two reasons.

1. Asuming that we're working at less than the transistor's maximum gain, the gain is approximately equal to the collector resistance divided by the emitter resistance. Ah! But you can clearly see that there's no emitter resistor. True, but the emitter has a small internal resistance (depends on the base to emitter current - usually a few ohms). So making the 470k collector resistor smaller would reduce the gain. Halve it, and the gain goes down by half.

2. Because of the biasing arrangement in this circuit, the collector resistor also affects the base (Ib) and collector (Ic) currents. That is because the transistor is turned "on" by a small amount of current flowing through those 2 x 470k resistors. If we assume the base is at 1V and the battery + is 9V, the base current will be about 8uA (8V/940k). From this we can also calculate Ic, because the transistor amplifies Ib by hFE (say 500 for some modern transistors). 8uA x 500 gives 4mA, which is a fairly large collector current. If we reduce the collector resistor from 470k to 10k, the base current goes up to 16uA, and the collector current up to 8mA. Because the original circuit had 2 x 470k resistors and low hFE transistors (150?), the original circuit probably had Ic about 1.2mA. Having Ic of 4 to 8 mA may affect gain and tone, and will affect battery life, so I'm now thinking that I'll use low gain transistors, like BD139s, and keep the 2 x 470k resistors on each transistor.

So, I've changed my mind and feel that keeping the collector resistor large (470k) and keeping transistor hFE low (150) is probably best. (It will also keep the tone authentic).

That may not be too clear. If not, ask again.

cheers

fixr1984 · July 19, 2006, 10:45:36 PM

Quote from: brett on July 19, 2006, 01:59:53 AM
Hi
The Fuzzrite looks very interesting. Will build one ASAP.

I would deffinatly recomend this to anyone.
Check out Dragonflys layout HERE
Or mine is found HERE
My layout has been verified. R1 and R2 are the resistors Brett was talking about, the layout calls for 10k, I used 100k.

Paul Marossy · July 20, 2006, 12:11:16 PM

Hmm.. that's an interesting circuit. What's up with those odd pot values? 350K & 33K?

markphaser · July 20, 2006, 02:37:28 PM

Looks like to me the Fuzz rite is a "Differential" fuzz amp

When it gets off balanced (not equal to zero) it creates fuzz or break up on the output

The 350K is the balanced (fuzz) pot
The 33K is just a output volume pot

What kind of "biasing" does the fuzz rite use for each stage? because its not BASE BIAS or COLLECTOR FEEDBACK BIAS

puretube · July 20, 2006, 03:31:52 PM

right...

RDV · July 20, 2006, 04:30:04 PM

Wasn't there a built-in fuzz in those Acoustic(?) amps Kreiger was using at that point? I had heard that was what was used on "Break on Through".

RDV

brett · July 20, 2006, 10:10:38 PM

Hi

QuoteLooks like to me the Fuzz rite is a "Differential" fuzz amp

Yeah, it seems to output a mix of an amplified inverse signal (collector of Q1), and its amplied inverse, amplified inverse (collector of Q2).

Because the signal out of Q2 is in-phase with the input (because it has been inverted twice), it probably encourages the oscillations and feedback reported for this circuit. An inverter at the output may be useful.

Concerning that weird 350k pot, I'm going to use a "47k resistor-250k pot-47k resistor" instead. And a 50k output pot.
cheers

Moonface · July 21, 2006, 03:05:07 AM

I have read that Krieger used the Maestro Fuzztone...

Paul Marossy · July 21, 2006, 10:17:13 AM

QuoteConcerning that weird 350k pot, I'm going to use a "47k resistor-250k pot-47k resistor" instead. And a 50k output pot.

Or, you could use a 1M pot with a 470K resistor + 56K resistor wired in parallel with it. That would get you about 347K or so, assuming that your pot measured exactly 1M.

markphaser · July 21, 2006, 12:08:35 PM

Thanks brent

What about the biasing what kind do u think this is?

The output is mixing the in-phase and inverse phase signals ? doesn't this cause cancellation?

brett · July 22, 2006, 07:42:50 AM

Hi

QuoteWhat about the biasing what kind do u think this is?

This biasing system is more common in older circuits. Instead of supply-to-base and base-to-ground resistors in a voltage-divider, it uses a collector-to-base resistor, and is known as collector feedback biasing.

Common biasing arrangements are described here:
http://203.208.166.84/kawsaralam/biasing.pdf

QuoteThe output is mixing the in-phase and inverse phase signals ? doesn't this cause cancellation?

It probably does a bit, but not so much you'd notice, for two reasons: Q2 outputs a MUCH larger signal than Q1, so cancellation would happen when a tiny amount of Q2 output is mixed with Q1 output. Also, the signal out of Q2 has steeper rise and fall and is hard clipped, unlike the fairly normal signal out of Q1. So they never cancel out very well.

cheers

Paul Marossy · July 22, 2006, 09:12:42 AM

Hey fixr1984, where's the second transistor on your vero layout?

fixr1984 · July 22, 2006, 10:07:44 AM

Quote from: Paul Marossy on July 22, 2006, 09:12:42 AM
Hey fixr1984, where's the second transistor on your vero layout?

Three holes to the right of Q1

Paul Marossy · July 22, 2006, 10:25:40 AM

Boy, that was a stoopid question! I thought those three pads in the middle of the board was for a transistor and didn't see Q1 and Q2! I was at work doing three things at once when I printed it out. Never mind.

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What effect is used early in LA Woman ?