Replies to This Discussion

Permalink Reply by Tommy Tomcat Arnold on October 5, 2010 at 9:48am

700, which is around what it will cost me to build another one.

Michael Schaefer said:

Very nice. What are you asking for the amp?

Permalink Reply by Tommy Tomcat Arnold on October 5, 2010 at 10:49am

OK, here's a quazi techie rundown of the amp:
Inputs: Plastic cliff jacks. Isolated from the chassis ground. Input grounds go to the preamp ground buss. With nothing plugged in, this amp is almost dead silent and overall it's my quietest build to date.

V1/input preamp: NOS GE 5751 from kcanostubes.com. Great tube for the price $18+ship.
Normal ch mods: bias resistor =1.5k bypassed with 10uF/25v cap. 100K resistor added between the V1A plate and it's .022uF coupling cap. Pull the normal channel knob up to make it like the stock 5F4 bright channel. 100pF bright cap engaged when knob is up.

Bright channel mods: bias resistor = 2.2K bypassed with a .68uF cap. 150K plate resistor for a little more gain. .01uF coupling cap. This channel's mixer resistor, after the volume control, is bypassed with a 500pF cap. More of a Marshall style preamp. Pull up on the white knob for an even brighter tone. I set this channel up to be twangy with strats and tele's, while also able to be driven Marshall style with humbuckers and stay tight in the bass and mids at rock volumes. Mission accomplished.

I lowered the value of the phase inverter coupling caps from .1 to .044uF. A .022uF Russian PIO K40 and a .022uF polypropylene film in parallel. The intention again to keep the bass more tight and defined at higher volumes.

Tubes: V1/input preamp: NOS GE 5751, V2/cathode follower=JJ ECC801 (12AT7), V3/phase inverter=JJ ECC9=803S, power tubes: Tung Sol 6L6 STR new production. Rectifier: NOS lightly used RCA 5U4G.

All coupling caps are the Russian military surplus PIO/paper in oil capacitors. The model is K40Y-9. This is the first build I've been able to use these in all coupling positions. To my ears they're very vintage sweet sounding... well the amp is very vintage sweet sounding to my ears. I can hear a 3D bloom and a swirl in the notes played through this amp, even at low bedroom volumes, that you don't get with mass produced amps. I don't know how much these caps contribute to the tone and tactile feel of this amp..?? but I'm using them in any future builds I do!!

The amp was used at the Bulldogs/Cottage jam last Fri night... and I know I'm biased, but I think it sounds every bit as good as Jimmy's 5E7, but it's a little different.. a little brighter and tighter. I didn't get to play it, but Jimmy said it was a little more .. and in a good way .. touch sensitive than his. Which was my plan with the mods. Overall I thought the amp sounded great all night long.. and I observed people really getting off all night playing through it. So far, mission accomplished!

If anyone would like to see a copy of the schematic, shoot me an email or message and I'll get one too you. You can't read it posted in this forum.



Tommy Tomcat Arnold said:

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 Tommy Tomcat Arnold on October 5, 2010 at 11:11am

Tommy Tomcat Arnold said:

OK, here's a quazi techie rundown of the amp:
Inputs: Plastic cliff jacks. Isolated from the chassis ground. Input grounds go to the preamp ground buss. With nothing plugged in, this amp is almost dead silent and overall it's my quietest build to date.

V1/input preamp: NOS GE 5751 from kcanostubes.com. Great tube for the price $18+ship.
Normal ch mods: bias resistor =1.5k bypassed with 10uF/25v cap. 100K resistor added between the V1A plate and it's .022uF coupling cap. Pull the normal channel knob up to make it like the stock 5F4 bright channel. 100pF bright cap engaged when knob is up.

Bright channel mods: bias resistor = 2.2K bypassed with a .68uF cap. 150K plate resistor for a little more gain. .01uF coupling cap. This channel's mixer resistor, after the volume control, is bypassed with a 500pF cap. More of a Marshall style preamp. Pull up on the white knob for an even brighter tone. I set this channel up to be twangy with strats and tele's, while also able to be driven Marshall style with humbuckers and stay tight in the bass and mids at rock volumes. Mission accomplished.

I lowered the value of the phase inverter coupling caps from .1 to .044uF. A .022uF Russian PIO K40 and a .022uF polypropylene film in parallel. The intention again to keep the bass more tight and defined at higher volumes.

Tubes: V1/input preamp: NOS GE 5751, V2/cathode follower=JJ ECC801 (12AT7), V3/phase inverter=JJ ECC9=803S, power tubes: Tung Sol 6L6 STR new production. Rectifier: NOS lightly used RCA 5U4G.

Speakers: One Fender Blue Frame 10".. AlNiCo magnet speaker with a 1.25" voice coil rated at 25-35W and a Jensen RI C10Q. Ceramic magnet speaker with a 1.25" voice coil rated @ 35W. The blue frame came out of our moderator's Custom Vibrolux Reverb.. and the C10Q came out of a 5F6A Bassman I built for my friend Willie B. So they're broken in, but I know they haven't been abused at any time in their lives..

All coupling caps are the Russian military surplus PIO/paper in oil capacitors. The model is K40Y-9. This is the first build I've been able to use these in all coupling positions. To my ears they're very vintage sweet sounding... well the amp is very vintage sweet sounding to my ears. I can hear a 3D bloom and a swirl in the notes played through this amp, even at low bedroom volumes, that you don't get with mass produced amps. I don't know how much these caps contribute to the tone and tactile feel of this amp..?? but I'm using them in any future builds I do!!

The amp was used at the Bulldogs/Cottage jam last Fri night... and I know I'm biased, but I think it sounds every bit as good as Jimmy's 5E7, but it's a little different.. a little brighter and tighter. I didn't get to play it, but Jimmy said it was a little more .. and in a good way .. touch sensitive than his. Which was my plan with the mods. Overall I thought the amp sounded great all night long.. and I observed people really getting off all night playing through it. So far, mission accomplished!

If anyone would like to see a copy of the schematic, shoot me an email or message and I'll get one too you. You can't read it posted in this forum.



Tommy Tomcat Arnold said:

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.

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