Please help with 5E3 build !

[MHProd]

That's without the Variac.

[MWJB]

Looks good, you could even try more B+ with a 5V4.

I'm always in favour of determining plate current with bias probes, but even by using the cathode resistor method, you appear to be well on the safe side with regards to current.

20.3v/270 = 75.2mA
75.2mA/2 tubes = 37.6mA
37.6mA * 302vdc (remember to deduct cathode voltage from plate voltage) = 11.4W ..then deduct about a W for screen current = 10.4W.

But as TX Strat points out, I wouldn't really be worrying about the tubes running over dissipation, with a 250/270ohm cathode resistor, until your plate voltage was well in excess of 380vdc.

[MHProd]

The 435VDC I had was with no tubes plugged into the wall.

The amp sounds much better now, huge deep solid low end. However, I still don't have that much gain... The amp starts to break up at 12oclock with my 335 !!! Around 3oclock with a strat or tele.

I put a 12AX7 in V1 but it still could get a bit more... I put a 5U4 rectifier in there that gave me a 345VDC B+ (instead of the 322VDC with the 5Y3).

The amp is kinda bright (even though there is no bright cap !!) and when I push the volume, I still get some buzzy, cringy sound in the high end when I play a full chord (some sort of buzzy noise that dies quickly).

Any clue why it'd do this ?

[MWJB]

Do you have an updated layout? Your layout shows bright caps galore, though you say you have none? You said early on that volumes were wire like a 6G3, then later you said that they were wired like a 5E3. Volume II on your layout would appear to be wired wrongly in any case.

Some photos of the actual build would be good, so that we can see what you have actually done.

5U4 is not a good choice for a rectifier in a typical 5E3 style amp, unless that you know for sure that you have a 3A 5VAC rectifier winding (most 5E3 style PTs only have a 2A winding).

[MHProd]

I added an extra tone pot.

Ch1: Volume pot is wired like a 6G3 (220K from leg 2 and leg 3 goes to bypass cap).
Ch2: Volume pot is wired like a 5E3 (leg 2 goes to bypass cap and leg 3 to 220K)

Both 220K Rs go to V2.

I noticed I put a NOS 12AT7 in V2 and I changed it to a JJ 12AX7 and I get more distortion. All the time, I've had a 12AX7 in V1. However it still doesn't distort like my original 5E3... and the amp is much brighter for some reason... I guess it's probably due to the Merc Magn OT.

Right now, the tone/volume pots have a 250pF cap accross them.

Do you guys have any tricks to try out... ?

[MWJB]

"Right now, the tone/volume pots have a 250pF cap accross them." Where exactly accross them? Are these 250pf caps in addition to the 500pf bright caps in the stock 5E3 & 6G3 circuits?

[MHProd]

No, each tone control has a .0047uF to ground cap on leg 1 and there's a 250pF cap between leg 3 of the tone pot and leg 2 of the volume pot.

Very bright overall and on the 5E3 channel, the tone pot doesn't add gain like an original 5E3... I'm pretty sure my wiring is good...

[MWJB]

Why 250pf, not 500pf.

Your 5E3 does not have a choke, hence the difference in voltage between plates and screens afffects tone.

Do you have a pic of the pot wiring?

[MHProd]

250pF because 500pF would make it even brighter ??

And yes, the amp has a choke.

Sorry no pics right now, but I explained how I wired it...

[MWJB]

250pf only allows certain higher frequencies through, compared to 500pf.

"but I explained how I wired it..." not that I doubt your wiring skills, but it's always nice to what people have ACTUALLY done, as compared to what they THINK they have done.

If you wanted your latest amp to sound just like a 5E3 then you wouldn't have used the choke, your screens probably run about the same as the plates (like a tolex amp), not 30-40v odd below the plates (like a 5E3).

[MHProd]

Oh you can doubt my wiring skills !! I doubt them myself...

I just don't have a camera handy right now.

I tried without the choke too but had the same result... (bright, not much distortion).

[tubeswell]

Can you draw a layout of your wiring and post that maybe?

[CharlieP]

I can't understand why someone starts a thread for help and then just drops it and never gets back to let those know if they ever solved it or to thank those who had input and tried to help. This thread may be several years old but useful yet if it had been completed.

[eschertron]

I can't understand why someone starts a thread for help and then just drops it and never gets back to let those know if they ever solved it or to thank those who had input and tried to help. This thread may be several years old but useful yet if it had been completed.

Whenever I think about that, I get a spine-tingling sensation and wonder if the MIA poster is now also dearly departed from poking into the amp at the wrong place, wrong time. Yes, I know, a bit macabre... and it's not even Hallowe'en!

But more on-topic: There are plenty of threads about gain and breakup in these amps. This particular thread seems a bit out-of-focus, there are other threads that actually go somewhere!