Orpheum Fuzz (GE) schematic: confirmation?

[LucifersTrip]

I'm just writing since: 1) loads of the old links in this forum are dead and: 2) The schematic  I was going to use [above from tonebender] has a couple 47K's oddly in series (shouldn't the 1M split the two 47k's? *)....and the transistors are unknown.

*same problem with silicon version:
http://tonebender.webs.com/orpheum-SILICON.GIF

It looks like Analogguru has the correct version on his site?  The transistors are also unlisted.

http://analogguru.an.ohost.de/193/schematics/Orpheum_Fuzz-Ge.gif

Is there another Orpheum schematic with any differences?

[jrod]

The only difference I see is that the schematic you posted is missing is missing the 100n cap to ground between the two 47k resistors. It is C3 on AG's schematic.

The 1M resistors is set up the same in both schematics and should be correct that way.

I have a few different Orpheum Fuzz schematics saved at home. I will check when I get there.

[Mark Hammer]

The splitting of the collector resistance to Q2 in half, with a cap to ground, is correct.  The cap helps to remove fizz.

Everything else seems fine, though.  Two cascaded stages with a control to pan/mix between them.

[LucifersTrip]

Thanks jrod, Mark for confirming/correcting

I looked too quickly at the silicon schematic and didn't pay attention to the .1u there

It's a pretty flexible circuit. I tried it with the 1M resistor between the two 47k's and it worked.
Amazingly, I got a decent fuzz with Q2 with an hfe as low as 17 and and high as 180.
I haven't tried anything outside that range or change Q1's hfe from my initial start of 100.

[jrod]

Cool! Glad you got it working!

[LucifersTrip]

Cool! Glad you got it working!

Yep, it is a pretty cool one.

It never didn't work...just wanted to actually start with the original schematic before I screw with it!
I still can't believe it sounded good with a Q2 w/ 17 hfe. I have to re-check that.

thanx again

[jrod]

Ok, I found the thread I remembered seeing a schematic of a traced unit: HERE

And HERE is the schematic. Tone pot in 1M and Volume pot is 100K.

It is interesting that you were able to get a good sound out transistor with 17 hfe!

[LucifersTrip]

Ok, I found the thread I remembered seeing a schematic of a traced unit: HERE

And HERE is the schematic. Tone pot in 1M and Volume pot is 100K.

It is interesting that you were able to get a good sound out transistor with 17 hfe!

That's funny...I actually skimmed that thread before breadboarding mine. I saw the schematic there also, but ignored it since the pot values
were also missing. Though, I missed the part where they determined the pot values as 1M & 100K. I'll definitely try those.

I just spent an hour or so swapping transistors. I definitely needed something with a higher hfe [75+] for Q1. Anything lower doesn't fire...dull, muddy. I decided on a NTE102A with an hfe of ~ 120.  Q2, on the other hand, works with a whole range as I stated before. The most fuzzy sound was actually with that low hfe 2N1499. I remeasured it at 16 hfe, amazingly (maybe there's leakage at work...which I didn't measure for anything). The other one that sounded just as good in Q2 was a 2N217 with hfe ~ 80.  The 2n1499 has a fatter sound with a little more bass response. I tried a couple more Q2's > 100 hfe up to around 120. They sounded a little hotter with more treble, but there was no increase in sound quality.  I think I'l finalize with Q1 = 120 and  Q2 on a switch = 16 & 80.

thanx again

[LucifersTrip]

Ok, I found the thread I remembered seeing a schematic of a traced unit: HERE

And HERE is the schematic. Tone pot in 1M and Volume pot is 100K.

Just realized that this schematic you linked to above seems to be the SI version...obviously some caps & resistor are different than the GE ver. I don't know if the tone/vol pot are different, also.

I did try the 1M/100K combo and it had more treble & less fuzz. I stuck with the 200K/250K.