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5E3 New Build with Mods Questions

lckyjcky
October 21st, 2011, 01:20 PM
I'm thinking about either a kit 5E3 or sourcing the parts myself. I'd like following mods:

1. Penthode/Triode Switch (to go from full-power to half-power): Yes, I know many people here do NOT like this. But I do.

2. Mid knob: I believe there's a fixed resistor (6.5 k?) that I just replace with a 25k(?) pot.

3. Effects Loop?

4. NFB switch? (to either turn it on/off or to change values)

5. ???

I'd really like a schematic/wiring for mods #1 and #2 above, if anyone's done it. I have seen a small diagram for the Penthode/Triode switch but not in context of 5E3. Would anyone be able to get the 5E3 schematic modified with a penthode/triode switch?

big-daddy-59
October 21st, 2011, 01:56 PM
2. Mid knob: I believe there's a fixed resistor (6.5 k?) that I just replace with a 25k(?) pot

You're thinking about a Blackface tone circuit here, I believe. The 5e3 is a different-much simpler-circuit.

lckyjcky
October 21st, 2011, 02:11 PM
Oh, my bad. 5E3 is just a volume and tone, isn't it? I was thinking Treble/Mid/Bass in addition to Volume. Great, we can strike out the mod #2 from the list!

celeste
October 21st, 2011, 04:43 PM
1. Penthode/Triode Switch (to go from full-power to half-power): Yes, I know many people here do NOT like this. But I do.

Easy enough to do. You need a DPDT switch, the center contacts go to each screen, one outer contact on each side goes to the plate of each respective tube, the other outer contacts go to the screen PS node

2. Mid knob: I believe there's a fixed resistor (6.5 k?) that I just replace with a 25k(?) pot.

Very different animal

3. Effects Loop?

Got to know what you want from it to suggest a topology. this just might be heresy.

4. NFB switch? (to either turn it on/off or to change values)

There is no NFB in a 5E3, that is part of its charm, but if you really want to go that way you are going to have to copy someone else that has done it successfully because NFB is a pain to get right.

5. ???

Low/high voltage? use the tube for the low voltage, and parallel it with SS diodes and a switch to turn them on and off. It would get you more power and more headroom

muchxs
October 21st, 2011, 04:51 PM
Be scientific. Build it stock first. Then you have a baseline to work from.

You're building the wrong amp, anyway. It sounds like you want a Brown Note D' Lite. It has all the features you want in it already.

lckyjcky
October 21st, 2011, 05:19 PM
Thanks, guys!

@celeste,

What spec DPDT switch, voltage/current?

@muchxs,

I never even heard of the Brown Note D'Lite until you mentioned it.

You learn something new everyday. I love this community.

lckyjcky
October 21st, 2011, 05:23 PM
Brown Note D'Lite $2185
http://store.bnamp.com/dlite22.html

I don't know about you but I'd rather pass. It's too expensive. I'm going to be scientific about it and build a simple 5E3 circuit amp with my own mods.

celeste
October 21st, 2011, 07:09 PM
Thanks, guys!

@celeste,

What spec DPDT switch, voltage/current?

@muchxs,

I never even heard of the Brown Note D'Lite until you mentioned it.

You learn something new everyday. I love this community.

See now you have the usual issue here as with standby switches. It is real hard to find a switch that is rated for the voltage, and when you do, they are expensive. If you feel safe with a 250v rated switch like a standby switch usually is, then there is your voltage rating. Current is less then 1/4 amp

muchxs
October 21st, 2011, 08:31 PM
Brown Note D'Lite $2185
http://store.bnamp.com/dlite22.html

I don't know about you but I'd rather pass. It's too expensive. I'm going to be scientific about it and build a simple 5E3 circuit amp with my own mods.

Click Brown Note's "kits" tab. The D' Lite 22 is affordable as a kit. $380 for the "bare bones" kit. It's especially affordable for a Dumble clone. It has all the bells and whistles. Passive FX loop, "PAB" lifts the tone stack. It has all the fun features of a real Dumble without the $50k price tag.

Know what Dumble is doin' these days? He's building 5E3s! :grin:

If you feel safe with a 250v rated switch like a standby switch usually is, then there is your voltage rating. Current is less then 1/4 amp

Look at a Carling some time. It's something like 125V 3A, 250V 1.5A. Extrapolate: That's 750mA @ 500V. Your total current draw is down around 100mA @ < 400V. Let's say you go hog wild and build up a Deluxe with EL34s. Your switch is still 5x over-rated. It's conceivable the thing will arc if you grossly exceed its rated voltage. In practice they don't.

I've got some gnarly 6A @ 250V bat switches if you're feelin'a little insecure. :grin:

celeste
October 21st, 2011, 08:46 PM
Look at a Carling some time. It's something like 125V 3A, 250V 1.5A. Extrapolate: That's 750mA @ 500V. Your total current draw is down around 100mA @ < 400V. Let's say you go hog wild and build up a Deluxe with EL34s. Your switch is still 5x over-rated.

I've got some gnarly 6A @ 250V bat switches if you're feelin'a little insecure. :grin:

I do not believe that that extrapolation is correct, because there has to be distance to insure that if an arc starts the contacts get far enough apart to brake it, other wise it is no longer a switch. The arcing is going to happen, and that will splatter the inside with tiny particles of the contact material further lowering the contact break distance. The higher the voltage the more the arcing. Pushing the voltage lowers the MTBF

muchxs
October 21st, 2011, 09:00 PM
I do not believe that that extrapolation is correct, because there has to be distance to insure that if an arc starts the contacts get far enough apart to brake it, other wise it is no longer a switch. The arcing is going to happen, and that will splatter the inside with tiny particles of the contact material further lowering the contact break distance. The higher the voltage the more the arcing. Pushing the voltage lowers the MTBF

It's another of those "close enough" deals. The Carlings are hell for stout. If the B+ is down in the appropriate range it won't be a whole lot over 250V. The current is a small fraction of what the switch will handle. It's good for 100k + operations in that application.

Start flippin'... :lol:

celeste
October 21st, 2011, 09:09 PM
It's another of those "close enough" deals. The Carlings are hell for stout. If the B+ is down in the appropriate range it won't be a whole lot over 250V. The current is a small fraction of what the switch will handle. It's good for 100k + operations in that application.

Start flippin'... :lol:

Yeah, I know. I just don't feel secure telling people I don't know to over rate something, without telling them they running the risk of a shortened life. I do it without a second thought now, but what I do and what I suggest others do are not always the same Insurance company investigators love to find stuff like this so they can deny the claim.

printer2
October 21st, 2011, 09:24 PM
Negative feedback, see the 5F10 Harvard. Use a SPDT switch with the center terminal at the tube cathode, one position then goes to the bypass capacitor used in the 5E3, the other position disconnects the capacitor and connects to the feedback resistor as in the Harvard. Use a pot to experiment how much resistance and level of NFB works well.

FenderLover
October 23rd, 2011, 08:26 PM
You could use the 5E3 as a starter kit: the Ground switch could be the Pentode/Triode switch; if you don't need 4 inputs, two of them, its triode and volume could be the FX loop. With those mods, the silk screen on the chassis wouldn't make sense, so drill a custom chassis and roll your own. The Brown Note route sure sounds appealing if you're not into design work.