Works starts TONIGHT on the...

Super Tomcat, a variant of a Fender 5F4 Super that was produced between 1956 and 1960. I've been collecting the parts that will go in this amp for around a year and a half.

http://www.ampwares.com/schematics/super_5f4.pdf

I'll post more later.. Tonight, I unstuff the eyelet board I'm going to use.

Replies to This Discussion

Permalink Reply by Michael Schaefer on April 5, 2010 at 8:15am

Fantastic. Can't wait to see the build pics and hear this thing when you're done.

Permalink Reply by Gordon Malone on April 5, 2010 at 9:59am

Cool. Put a 5AR4/GZ34 rectifer in there if you want a little cleaner sound (a little higher voltage output than a 5U4GB and less voltage sag under load). The 5AR4 has a controlled warm up filament so the standby switch being on when the power is turned on is less of an issue. It also draws less filament current (1.9 amps) vs the 5U4 (3 amps) so a little less strain on the power transformer. Pinouts are the same except 5AR4 has an internal connection on pin1 so don't connect anything to pin1 (according the the RCA Receiving Tube manual).

Permalink Reply by Michael Schaefer on April 5, 2010 at 10:18am

Could you please speak in English? This is America after all. :)

Gordon Malone said:

Cool. Put a 5AR4/GZ34 rectifer in there if you want a little cleaner sound (a little higher voltage output than a 5U4GB and less voltage sag under load). The 5AR4 has a controlled warm up filament so the standby switch being on when the power is turned on is less of an issue. It also draws less filament current (1.9 amps) vs the 5U4 (3 amps) so a little less strain on the power transformer. Pinouts are the same except 5AR4 has an internal connection on pin1 so don't connect anything to pin1 (according the the RCA Receiving Tube manual).

Permalink Reply by Tommy Tomcat Arnold on April 5, 2010 at 11:23am

I'm not going to use a tube rectifier tube on this one. I'm going to wire up diodes, a 100-200ohm/10-15w sag resistor and a thermistor (this simulates the slow warm up of a tube rectifier so the first filter cap doesn't get slammed with all 430-450+ V at once) on the recto socket. I'll be shooting for 410 to 430 (maybe a little more) on the plates of the 5881's. This way I or the owner won't ever have to worry about the extra expense or failure of a rectifier tube.

Other deviations:
*The normal channel will bypass the cathode follower and tone stack like a Vox AC30 normal channel. It will be mixed in prior to the Cathodyne PI tube, making the normal ch very similar to a 5E3 (Tweed Deluxe) minus the tone control.
*A 250pF/82k slope resistor/.022uF/.047 brighter sounding CF driven tone stack.
*Pull bright switches on both volume controls.
*I'm considering a pull deep switch on the bass control..??
*Foot switchable NFB in/out switch using the unused speaker jack hole. This could be used as a lead boost switch.

Also.. I'm going to order a clean fiber board and not use the one I was going to use. It would have been too much of a hassle to get the solder out of all the eyelets.

Permalink Reply by Gordon Malone on April 5, 2010 at 12:15pm

Cool again! While you are doing all that, add a switch to allow use of EL34's in the output :-) Plus a bias control to fine tune bias. What if you had the Fender tone stack on one channel then have a Baxandall stack on the other? That would give a lot of flexibility. Here's some info: http://www.duncanamps.com/technical/tonestack.html

Michael - That is English! You're a techie guy. You can learn this! Did you look at that stuff I emailed you the other week?

Permalink Reply by Tommy Tomcat Arnold on April 5, 2010 at 12:22pm

I was going to do that too. I need to look into the biasing of EL34's vs 5881/6L6's, but that's pretty simple. Just tie V3 & V4's pins 1 & 8 to ground.. instead of just pin 8 w/ 6L6's.

Permalink Reply by Michael Schaefer on April 5, 2010 at 12:33pm

No. :)

My brain does not have room for this information at this time. Please try again later. LOL.

Gordon Malone said:

Cool again! While you are doing all that, add a switch to allow use of EL34's in the output :-) Plus a bias control to fine tune bias. What if you had the Fender tone stack on one channel then have a Baxandall stack on the other? That would give a lot of flexibility. Here's some info: http://www.duncanamps.com/technical/tonestack.html

Michael - That is English! You're a techie guy. You can learn this! Did you look at that stuff I emailed you the other week?

Permalink Reply by Tommy Tomcat Arnold on April 7, 2010 at 2:37pm

Oops, I didn't address all of Gordon's comments. I was planning on a bias control and have put them in the 4 tweed style amps I've put together. And.. I'm putting this in a 4 input 5F4/5E7/5E5 chassis (vol, brite vol, treb, bass, presence knobs).. I want to keep the control pannel stock looking, so no room for another set of tone knobs. The stock 5F4/5E7/5E5 circuit is pretty gainy. I'm trying to reduce some of the gain in the bright channel by using a tone stack that has more loss.. The normal channel, will be FAT and tweedy. I'll email you guys the schematic I fixed up the other day.

Permalink Reply by Tommy Tomcat Arnold on April 27, 2010 at 11:27pm

I really really got started on the Tweed Super this past w/e April 25. Pics will be posted below, but.. so far I have the board stuffed, extra holes have been drilled in the chassis and the transformers and choke have been mounted on the chassis.

Board notes: We'll get to hear how the Russian K40 PIO's sound. K40's in all coupling positions. I've changed my mind since my initial posts. Normal channel will be stock 5F4 with pull bright switch on the volume control. Bright channel: 220k v1 plate resistor, bias 2.7K w/ .68uF bypass, 470pF bypass on channel mixer resistor and 120pF treble bypass on the volume control, pull deep on the volume control. Marshall voiced. E series tone controls w/CF. 68K grid resistor on the PI. Beefed up power supply. N1=30uF/500v, N2 40uF/450v, N3=22uF/500, N4=16uF/450v. In an attempt to make the Presence control to work better: 47K NFB resistor going to a 25K pot, .1uF to ground.

Next up: install AC cord, mount tube sockets and jacks, trim the back of the board and mount in chassis and start tube socket to board hookups.

Permalink Reply by Michael Schaefer on April 28, 2010 at 9:02am

Lookin' good Tommy. Can't wait to hear this thing.

Permalink Reply by Tommy Tomcat Arnold on October 5, 2010 at 7:57am

This amp has been finished for several weeks short of final tweeking. I finally did that last week after ordering some tubes and took the amp to the Bulldogs/Cottage jam last Friday night. I know I'm biased, but I thought it sounded pretty dang near perfect. I'm selling it as a used amp if anyone is interested and I'll use that $$ to build another.