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6L6s and new OT

12/3/2003 9:52 PM
Scott Wolfe	6L6s and new OT I’ve seen a lot of discussion lately re: beefing up the 5e3. Here’s what I did and the results are fantastic – at this point I can’t see going back to stock. The amp flat-out rips. The mods are simple - and reversible: 1. Cathode resistor: Change 270-ohm 5W to 270-ohm 10W. 2. Replace OT with Bruce’s tweed Super OT that has 4- and 8-ohm taps. 3. Replace the 6V6’s with a matched pair of small-bottle 6L6WGB’s. Regular-size 6L6’s don’t fit given the size of the Weber P12B bell cover. 4. Replace the 5Y3 tube with a Weber GZ34 Copper Cap. Since the 6L6’s will draw more filament current than the 6V6’s and since the Copper Cap draws no filament current, the removal of the rectifier filament-current draw results in the PT not running so hot. 5. I had earlier done the PI bias mod. It tightened up the amp (for me a good thing in a band setting). 6. Replace main speaker jack with a mono jack and wire it to the 8-ohm tap. Use this jack when using just the single 8-ohm speaker in the cab. 7. Wire the extension speaker jack to the 4-ohm tap. Add a mono jack in parallel (run it off the speaker terminals and mount the added jack to the cab somewhere). So, I plug the on-board speaker into the 4-ohm jack and a 1x12 8-ohm extension cab into the parallel 4-ohm jack. The sound field is huge. I got all the parts from Bruce who was unbelievably helpful. We played around with coupling caps but always came back to stock 5e3 values. Note that I’m playing an LP with humbuckers. If you’re using single-coils, ymmv. Here’s what I have: - The amp is noticeably louder - volume level is now good for gigging in small/medium clubs (the stock 5e3 was iffy for gigging). - Tonewise: the lead tone is actually thicker than the stock 5e3 (that's good); attack is punchier (stiffer rectifier); and still there’s plenty of crunch. It’s punchy and crunchy. This amp puts a smile on my face. With the 1x12 extension cab, it’s fabulous. There’s nothing wrong with the stock 5e3 sound – I love that, too. Early ZZ Top, can't beat that. I prefer the stock 5e3 when I’m playing alone in the basement. It’s more lush, more organic. Terrific for self-accompaniment. What I have now is just different – for me, the amp is now much more versatile for classic rock and it still sounds great on Billy Gibbons stuff. For gigging in a band situation, the modded amp is better for me. It’s loud enough, it cuts through, and has drop-dead gorgeous tone.

12/3/2003 9:52 PM

Scott Wolfe

6L6s and new OT

I’ve seen a lot of discussion lately re: beefing up the 5e3. Here’s what I did and the results are fantastic – at this point I can’t see going back to stock. The amp flat-out rips. The mods are simple - and reversible:

1. Cathode resistor: Change 270-ohm 5W to 270-ohm 10W.
2. Replace OT with Bruce’s tweed Super OT that has 4- and 8-ohm taps.
3. Replace the 6V6’s with a matched pair of small-bottle 6L6WGB’s. Regular-size 6L6’s don’t fit given the size of the Weber P12B bell cover.
4. Replace the 5Y3 tube with a Weber GZ34 Copper Cap. Since the 6L6’s will draw more filament current than the 6V6’s and since the Copper Cap draws no filament current, the removal of the rectifier filament-current draw results in the PT not running so hot.
5. I had earlier done the PI bias mod. It tightened up the amp (for me a good thing in a band setting).
6. Replace main speaker jack with a mono jack and wire it to the 8-ohm tap. Use this jack when using just the single 8-ohm speaker in the cab.
7. Wire the extension speaker jack to the 4-ohm tap. Add a mono jack in parallel (run it off the speaker terminals and mount the added jack to the cab somewhere). So, I plug the on-board speaker into the 4-ohm jack and a 1x12 8-ohm extension cab into the parallel 4-ohm jack. The sound field is huge.

I got all the parts from Bruce who was unbelievably helpful. We played around with coupling caps but always came back to stock 5e3 values. Note that I’m playing an LP with humbuckers. If you’re using single-coils, ymmv.

Here’s what I have:

- The amp is noticeably louder - volume level is now good for gigging in small/medium clubs (the stock 5e3 was iffy for gigging).

- Tonewise: the lead tone is actually thicker than the stock 5e3 (that's good); attack is punchier (stiffer rectifier); and still there’s plenty of crunch. It’s punchy and crunchy. This amp puts a smile on my face. With the 1x12 extension cab, it’s fabulous.

There’s nothing wrong with the stock 5e3 sound – I love that, too. Early ZZ Top, can't beat that. I prefer the stock 5e3 when I’m playing alone in the basement. It’s more lush, more organic. Terrific for self-accompaniment.

What I have now is just different – for me, the amp is now much more versatile for classic rock and it still sounds great on Billy Gibbons stuff. For gigging in a band situation, the modded amp is better for me. It’s loud enough, it cuts through, and has drop-dead gorgeous tone.

12/3/2003 11:23 PM
bnwitt	Scott, so you didn't redo the power tube screen resistor set up?

12/4/2003 12:00 AM
Scott Wolfe	Nope. No change in screen or grid resistors. I did go ahead and measure the amp and drew up a voltage chart, seeing that now I have 6L6's and a new OT. If you want, I'll dig it out and post the voltages I'm getting.

12/4/2003 2:33 AM
Bob Arbogast	Scott, Please do post your voltage survey. (Make sure you include your AC line voltage!) I'm sure that will be useful for many of us. Thanks. Bob Arbogast

12/4/2003 5:22 AM
anonymous	OK, here are my voltages – first with AC clamped at 117VAC. Then with voltage at 122VAC. Remember, I have the PI bias mod installed – that affects the pre-amp measurements quite a bit. I also have a zener diode installed. My cathode resistor measures 272.2 ohms. 117VAC: V1: P=123; G=0; K=2; P=125; G=0; K=2 V2: P=158; G=0; K=1.2; P=166; G=72; K=76 V3 6L6WGB: P=379; G2=342; K=28.6 V4 6L6WGB: SAME AS V3 V5 GZ34 Copper Cap: B+ = 383 122VAC: V1: P=127; G=0; K=2; P=129; G=0; K=2 V2: P=163; G=0; K=1.3; P=173; G=75; K=79 V3 6L6WGB: P=396; G2=358; K=30.2 V4 6L6WGB: SAME AS V3 V5 GZ34 Copper Cap: B+ = 402 The tubes aren’t running hot. Plate dissipation is 18W @117VAC; and 20W @122VAC. Hope this helps!

12/4/2003 5:22 AM

anonymous

OK, here are my voltages – first with AC clamped at 117VAC. Then with voltage at 122VAC. Remember, I have the PI bias mod installed – that affects the pre-amp measurements quite a bit. I also have a zener diode installed. My cathode resistor measures 272.2 ohms.

117VAC:
V1: P=123; G=0; K=2; P=125; G=0; K=2
V2: P=158; G=0; K=1.2; P=166; G=72; K=76
V3 6L6WGB: P=379; G2=342; K=28.6
V4 6L6WGB: SAME AS V3
V5 GZ34 Copper Cap: B+ = 383

122VAC:
V1: P=127; G=0; K=2; P=129; G=0; K=2
V2: P=163; G=0; K=1.3; P=173; G=75; K=79
V3 6L6WGB: P=396; G2=358; K=30.2
V4 6L6WGB: SAME AS V3
V5 GZ34 Copper Cap: B+ = 402

The tubes aren’t running hot. Plate dissipation is 18W @117VAC; and 20W @122VAC.

Hope this helps!

12/4/2003 5:25 AM
Scott Wolfe	Oops - didn't mean to be 'anonymous.'

12/4/2003 3:22 PM
Scott Wolfe	Forgot to mention - I still pop in the 6V6s and the 5Y3 when I want to - 'cuz it sounds great. I've got some 6V6 pairs of Mazdas and JAN Phillips, both very nice, and I use them sometimes at home and in our band's small rehearsal space. Being able to switch between 6V6s and 6L6s whenever I want to is a real plus for me.

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