# Tube function/location, other Qs (Garnet Session Man)



## ga20t (Jul 22, 2010)

I'm trying confirm 1) the tubes in my amp are in the right positions 2) which does what so I can try some fresh tubes as my reverb's a bit... extremely subtle. I'm also uncertain as to what load this amp wants to see at the speaker out (8Ω ?), and what load with an extension cab (8Ω + 8Ω = 4Ω ?). Reading schematics is not a talent I possess, but I do see _"some models have 4Ω and 8Ω taps"_ on this schematic—wondering which is the most likely given mine has speaker out & extension out jacks.

Schematic here: http://www.thetubestore.com/lib/thetubestore/schematics/Garnet/Garnet-G250FTR-Sessionman.pdf

Here's a drawing I made of the actual chassis, looking from above and behind (sorry if that's confusing). 1st input's at the top right of the drawing, all other controls follow leftward. I've labelled the preamp/driver/recovery tubes in an attempt to make responding easier.

Thanks for any help.


----------



## ga20t (Jul 22, 2010)

My (limited) intuition tells me that "A" is the first tube/V1, and "E" would be V5—the phase inverter—right before the power tubes, everything moving along in a counter-clockwise fashion from the top right of my chassis drawing.

But a 12AU7 (D) would most likely be the reverb _driver_ valve, wouldn't it? That would mean signal's hitting the 12Au7 and recovering at valve ____. If I had to guess, "D" (12AU7) would be the reverb driver, and then back to "C" for recovery? I'm getting a lid splash when I tap the tank, so I'm assuming the recovery's strong at least.


----------



## Granny Gremlin (Jun 3, 2016)

My old Sessionman (vocal not guit version) had the out Z clearly marked (separate out jacks). Assuming it uses the same OT (a reasonable assumption) you should have 4 and 8 ohm outs available; from the images I see online there should be a selector wire to the right of the out jacks on the back. This output Z is for both jacks (parallel) - so if 2 8 ohm cabs you choose 4, 1 8 ohm cab choose 8, etc.

IIRC he reverb tube is the *U*7... [breaking out the Garnet book]... Yep. Recovery is one of the X7s (can't tell you which - if you pop the chassis should be obvious). The weird thing is that, if your amp has fuzz (G250FTR or G250D?) then there should be a 6JW8 in there (pentode half is the fuzz and triode half is the trem).


----------



## ga20t (Jul 22, 2010)

Granny Gremlin said:


> My old Sessionman (vocal not guit version) had the out Z clearly marked (separate out jacks). Assuming it uses the same OT (a reasonable assumption) you should have 4 and 8 ohm outs available; from the images I see online there should be a selector wire to the right of the out jacks on the back. This output Z is for both jacks (parallel) - so if 2 8 ohm cabs you choose 4, 1 8 ohm cab choose 8, etc.
> 
> IIRC he reverb tube is the *U*7... [breaking out the Garnet book]... Yep. Recovery is one of the X7s (can't tell you which - if you pop the chassis should be obvious). The weird thing is that, if your amp has fuzz (G250FTR or G250D?) then there should be a 6JW8 in there (pentode half is the fuzz and triode half is the trem).


My Revolution has the 4Ω/8Ω selector tap & screw on the back, but not my Session Man—just "speaker" & "extension" jacks.

Schematics/model is a bit confusing because the 250D schematic (thought the D was the head version?) makes no mention of fuzz/has 12AX7s throughout, and I'm not seeing the 12AU7 in that one... The FTR accounts of course for the Fuzz/Tremolo/Reverb, which mine has. But I saw those 6JW8s on the schematic in my OP... which mine doesn't have either.

Hmm. Thought I'd order & try some fresh tubes for driver/recovery before I take the amp in. My reverb seems a good bit more subtle than the one in the only YouTube vid I can find. I suppose I could get an AU7 anyways, and replace some 12ax7s working my way back and try that. I should probably take it in and get those big filter cans replaced anyhow.


----------



## jb welder (Sep 14, 2010)

The schematic that mentions the taps shows a 4 ohm output. So my reading on that is that it is 4 ohm out unless it has the multi-taps.


----------

