Sam Ash Fuzzz Boxx

[Davelectro]

I didn't try your feedback arrangement yet.

But I did increase Q1's feedback resistor in multisim to set the collector at 4.5V-5V and it made no significant difference in the circuit's response (other than gain decreasing a few dbs).

So I don't know...at least the Astrotone sounds really good with Q1's collector sitting lower than 1/2 supply. What benefits should I expect from 4.5V?

[Gus]

I didn't try your feedback arrangement yet.

But I did increase Q1's feedback resistor in multisim to set the collector at 4.5V-5V and it made no significant difference in the circuit's response (other than gain decreasing a few dbs).

So I don't know...at least the Astrotone sounds really good with Q1's collector sitting lower than 1/2 supply. What benefits should I expect from 4.5V?

What are you using as the input to the multisim?  Are you using a guitar and cable sim before the circuit? 

The collector voltage above and below 1/2 the power supply voltage is another thing to read about.  I set the sim at about 5VDC as shown in the first post.

[Davelectro]

No, I wasn't considering pickup influence.

I've included a humbucker simulation now and gain seems to go up a little with collector at half supply.

I will try rebiasing the actual circuit as soon as I can.

[Last]

Hello,

I'm very new to all of this, but, have a lot of soldering experience & have done other projects.

I'm thinking of replacing the pair of MPS8099s transistors with a pair of 2N3565 NPN Transistors 'Fairchild'.

Would this be worth the change or should I leave it as is?  I like the way it sounds now okay but I do think it could be infinitely better, especially after listening to some of the direct comparison demos of the original to this re-issue.

Also, if I do swap out the transistors would there be anything else I should change or do while I have it out of it's enclosure?

Thanks everyone for your help & expertise.

[LucifersTrip]

As with many silicon fuzzes, the hfe is much more important that the model #, so if the 3565's don't have a much different gain than the ones you have in there now, it's probably not worth it.

http://pdf1.alldatasheet.com/datasheet-pdf/view/172653/ONSEMI/MPS8099.html

Many vintage fuzzes sound better (at leas to me) with low to medium gain transistors (100 - 300 hfe) and this is no exception. After I built this, I found other comments from builders who also found 200-300 hfe the best.

Make note of the transistor voltages before and after if you decide to swapping transistors.

Don't get too caught up on what it sounds like in any video. What's the chance you're using the same guitar, amp, mic & settings...and don't expect too much out of this one.
Even though it's a fun build because it's actually not a direct copy of another and has a unique sound, it's kind of average, somewhere between a distortion & fuzz.

[Last]

Very helpful thank you LucifersTrip.

Makes a great deal of sense.  Really appreciate your insight & help.