Dr. Z Galaxie

[jon]

I've been looking at some gut shot of a Galaxie lately and I find the amp intriguing. As stated in other treads the amp is basically a 5F4 Tweed Super with the channels cascaded. I am having trouble determining how the switching is routed and the values of cathode resistors and the bypass caps across the plates. If anyone has any information I would surely appreciate it. I have attached the gut shot I have.

[da Geezer]

This amp interests me, too.

Several observations from glancing at the gut shot....

1) the extra "drive" gain stage seems to be added/inserted after the clean/normal input stage

Clean = V1A > V2 > V3
Drive = V1A > V1B > V2 > V3

2) the picture is of an early model with the presence control. The later models replace the presence with a master for the drive "channel"

Reviews state that something was done to reduce/tighten up the bottom end flabbiness of the 5f4.... Maybe improvements to the cathodyne PI (??)

I wonder if we should inquire of Dr Z for guidance on component values, since this model is now out of production??

Geezer

[jon]

This amp interests me, too.

Several observations from glancing at the gut shot....

1) the extra "drive" gain stage seems to be added/inserted after the clean/normal input stage

Clean = V1A > V2 > V3
Drive = V1A > V1B > V2 > V3

2) the picture is of an early model with the presence control. The later models replace the presence with a master for the drive "channel"

Reviews state that something was done to reduce/tighten up the bottom end flabbiness of the 5f4.... Maybe improvements to the cathodyne PI (??)

I wonder if we should inquire of Dr Z for guidance on component values, since this model is now out of production??

Geezer

Well he is a member, and it is a discontinued amp. Send him a PM see what happens he's "DR.Z"

[NickC]

It sure is a good looking build. Quality!

[M Fowler]

The switching is for Pentode/Triode. Uses 3 12AX7's and P/P 6L6GC's and 5U4 recto.

I thought the idea was basically what I did with my Swamper amp a 5f6a with single input jack but use two volume pots to mix high and low gains. I lost the presence and added master volume.

Mark

[da Geezer]

The switching is for Pentode/Triode.

Mark

While there is a pentode/triode switch on the back, there is also relay switched channel selection.

http://drzamps.com/amps/galaxie/

[M Fowler]

I wonder if the Remedy didn't replace the Galaxie?

I'll ask Mike if he has time to tell us the history.

[randalp3000]

here's the history from the z website

Galaxie

The Galaxie is a channel switching (via footswitch) amp that combines classic tweed clean tones and smooth modern drive sounds. The clean channel nails the sweet swirling sound of classic tweed amps that have become the foundation of electric guitar tone. The drive channel is the result of Dr Z’s 20 plus years of design experience. You’ll find it has excellent sustain and a rich open sound with plenty of gain on tap for today’s needs.

The output transformer is made by the venerable Triad company and is to the original spec found in classic tweed amps like the Super, Pro, and low powered Twin. Great care was taken to accurately reproduce this transformer. Dr Z is very excited to use the Triad transformer in this design.

The preamp consists of three 12AX7s coupled to a dual 6L6 output section and rectified by a 5U4. The Galaxie features a pentode/triode switch on the rear of the amp. This will enable 40 watts in pentode setting and 30 watts in triode.

New for 2010 we have eliminated the Presence control and added a Master Volume for the drive channel. This gives the ability to match up the output of the clean and drive channels with ease.

The sweet big bottled sounds of the Galaxie are at your command. The Galaxie is set to explore!

Power Outpu:t 40/30 Watts (pentode/triode)
Output Tubes: 2 - 6L6
Preamp Tubes: 3 - 12AX7
Rectifie: 1 - 5U4
Controls: Volume, Volume (ch 2), Treble, Bass, Master, Triode/Pentode Switch (back panel), Channel Foot Switch
Configurations: Head, 2x10 and 1x12 Combos
Colors: Black, Blonde, Red
Dimensions & Weight: Head: 19" W, 9 3/4" H, 9 1/2" D 1-12 and 2-10 combo: 23" W, 20 1/8" H, 10" D

[randalp3000]

I have both versions of this amp and I tried to trace it about a year ago. I used a 5f4 schematic and made some notes. Sorry but I couldn't wrap by brain around the switching. I do believe the hot channel adds a series gain stage to the normal channel.

filtering upped to 47uf, 47,22. and 8uf starting at PT (tighter bottom)
negative feed back 100k instead of 56k
no 4.7M negative feedback in preamp
820R added between tonestack and V3A
ch 1 first gain stage cathode 1.5k,25uF 25v
ch 2 cathode 520R, 10uF. 220k plate w/ parallel 500pf. .0068 bright cap on pot.

sorry but I have no idea how the preamp is stacked.

these amps sound killer but I need a bit more clean before it starts to poop out. I would love to try one with a big ass output transformer some time. I don't know how but these make my Victoria Tween twin sound like a whiny little bitch, total waste of money.

If anyone wants to come and trace it let me know.

[jon]

I have both versions of this amp and I tried to trace it about a year ago. I used a 5f4 schematic and made some notes. Sorry but I couldn't wrap by brain around the switching. I do believe the hot channel adds a series gain stage to the normal channel.

filtering upped to 47uf, 47,22. and 8uf starting at PT (tighter bottom)
negative feed back 100k instead of 56k
no 4.7M negative feedback in preamp
820R added between tonestack and V3A
ch 1 first gain stage cathode 1.5k,25uF 25v
ch 2 cathode 520R, 100uF. 220k plate w/ parallel 500pf. .0068 bright cap on pot.

sorry but I have no idea how the preamp is stacked.

these amps sound killer but I need a bit more clean before it starts to poop out. I would love to try one with a big ass output transformer some time. I don't know how but these make my Victoria Tween twin sound like a whiny little bitch, total waste of money.

If anyone wants to come and trace it let me know.

Wow!! Thanks that clears up a lot of things. Any chance on getting a couple of gut shots or the value of the cap bypassing the 56K plate load resistor in the PI

[randalp3000]

If I can find some time to dig one up from the basement and get my bench cleared I'll try and get some good pics.

I have nothing in my notes about a cap but I could have missed it.

[jon]

If I can find some time to dig one up from the basement and get my bench cleared I'll try and get some good pics.

I have nothing in my notes about a cap but I could have missed it.

For Reference

[randalp3000]

Well I was wrong about a few things but the amp my earlier notes were based off was a master volume model and I just went through my non master version #43.

V1a and V1b are in parallel, 1a as described earlier.
1b is 22k grid, cathode 820r 1uF or 100uF(can't read cap), plate 220k parallel 500pf, .022 coupling cap, 1m vol. .0068 bright cap. 1000pf between plate and cathode.

these both feed the relay (spdt) to parallel 270K's

this amp does have the 47m feedback resistor in the cathode follower, not sure if it's in my other amp.

v3b 56k plate has a parellel .001 cap.

2.7k grid resistors on 6l6's and 470r's on the screens.

[M Fowler]

Good info Randal.

[da Geezer]

Yes, thank you!

I had suspected that to be a .001 paralleling the 56k, judging by the size

G