Fuzzrite from a Mosrite amp...

[LucifersTrip]

I finally got around to building the rare version of the Fuzzrite from a Mosrite amp.  There's more detail here:
http://apocalypseaudio.blogspot.com/2010/05/mosrite-amplifier-onboard-fuzzrite.html

Here's the original:


I cleaned it up and simplified it for an easy build:


First note...the schematic shows 35v supply thru 47K resistor. 9v works fine without the resistor.

I built it with silicon transistors in the 100-150 hfe range and it was excellent right off...but I've always liked the germanium versions of Fuzzrites & variants better, so I decided to go with that.

Like the Orpheum, it's sounds killer with a a Q1 in the 80-120 hfe range and a Q2 in the 50-70 hfe range. The big difference here compared to a normal Fuzzrite is that it's fatter, most likely due to the larger output caps (.0047uF/.01uF instead of .002uF/.002uF), which is closer to the germanium Orpheum (.005uF/.005uF).

The silicon versions are harsher and can get really trashy with fuzz at full. The germanium versions can get much buzzier.  To give the option of having the germanium version harsher, I added a simple mod, which works like a perfect tone control here.   I used a 200K pot in place of the 100K R so the stock tone is centered....full counterclockwise is bassy-er and full clockwise you get some beautiful trebley harshness....but with germanium, never too harsh.

I ran into one odd problem here that I never have before with a Fuzzrite variant. There was wild oscillation with fuzz at the lowest setting. A simple 2K cutoff solved that problem.

Here's my final version of this killer:


btw, if anyone knows the model of the amp this came from, please let me know. I can't finish this box without etching the correct model number into the bottom of the box...

[teemuk]

The model would have been BG-1000 or BG-500.


Demonstrated here in a youtube video:
http://www.youtube.com/watch?v=dDhbgn9E6Rs

Technically, those amps were not 100% true Mosrite products (the whole project idea, development and manufacturing was done by outsiders and the Mosrite trademark was merely licensed). True Mosrite amps, built by Mosrite, were only built from the leftover parts stock a few years later the company that devised the BG-1000 and BG-500 amps had bankrupted (due to those very same amps they tried to sell), but that's another story.

[LucifersTrip]

The model would have been BG-1000 or BG-500.

Demonstrated here in a youtube video:
http://www.youtube.com/watch?v=dDhbgn9E6Rs

Thanx alot!  that's a great demo. He even confirms what I noted, that the amp fuzz has more low end. (3:49+)

Both the BG-1000 and BG-500 had the same Fuzzrite circuit?

[teemuk]

The preamps were the same boards so, yes.

Naturally circuit revisions might have occured during manufacturing, Waters-Connelly (the company that manufactured them) is notorious for botching up the original design to a point where the failure rate skyhighed and  amplifiers were returned faster than sold... which was pretty much the demise of Mosrite Distribution Co. whose ideas was to market these.

Here's some more related stuff...
http://www.planktones.com/PageAwardSchematic.html

[LucifersTrip]

The preamps were the same boards so, yes.

Here's some more related stuff...
http://www.planktones.com/PageAwardSchematic.html

that's funny...I just got done looking thru that. the schematic there:
http://www.planktones.com/Mosrite%20BG-500%20Schematic/11.jpg

...is exactly the one I used...cool (I added BG-500 to the schematic).  In my searches I came across another Mosrite Amp, the 400
http://mosriteforum.net/forum/viewtopic.php?p=38257&sid=ce40d618b698e8dde1c0f7c523d3f991

does that have the same board, also?  I'll keep looking...

thanx again for all the info

[teemuk]

They might have but I'm not familiar with the details of those amps.

They are not same amps and they came from entirely different sources and manufacturers. If you compare the amps closely you can see a lot of dissimilarity in design, although cosmetic design-wise there evidently was some copying going on on Mosrite's part. So, not same amps, perhaps not the same Fuzzrite either.

Anyway, I don't know about the Fuzzrite in those. For all I care, that circuit has appeared in many variations so having slightly different circuitry in amps isn't surprising either. Yeah, few component values may or may not have changed but it's not like it's an entirely different circuit or something because of that. Even the difference in tone isn't all too staggering.

By the way, the former Mosrite "numbered" amps were also - similarly to guitars - sold under "Gosbel" brand once Semi Moseley had lost his company in bankruptcy.