5E3 Power Mod

[Mikeb]

My 5e3 currently has a 022772 PT, Hammond 40W OT, 5AR4 rect, and 6L6's. I am considering changing the PT to a 125P23B/025130 with bias tap. My thoughts are that more source current and grid bias'd may help me with a tad more volume to cut through playing live.

Am I on the right track?

[stokes]

Some mods I did to achieve the same end were the PaulC mod to the PI,100uf filter caps on the main and screen supply a couple of more volts to the preamp tubes via a reduction in the power supply resistor after the screen,a 5751 in place of the 12AY7,5R4 rectifier (your 5AR4 would be better) and an EVM 12L speaker.I am using NOS Marconi 5871 (6V6 sub) power tubes.The amp now cuts thru fine now,the biggest improvement was the speaker,the headroom and percieved volume was incredible with the EV.

[Mikeb]

Thanks for the input... The Paul C mod on the PI seems to be very popular. I will experiment with the other suggestions you made. I am using a pair of P12R's that sound pretty good but I suspect they may be a limiting factor in my live sound as the sound compressed at higher volumes... I have a few other options.

Thanks... Mike

[sportster4eva]

Originally Posted by stokes

Some mods I did to achieve the same end were the PaulC mod to the PI,100uf filter caps on the main and screen supply a couple of more volts to the preamp tubes via a reduction in the power supply resistor after the screen,a 5751 in place of the 12AY7,5R4 rectifier (your 5AR4 would be better) and an EVM 12L speaker.I am using NOS Marconi 5871 (6V6 sub) power tubes.The amp now cuts thru fine now,the biggest improvement was the speaker,the headroom and percieved volume was incredible with the EV.

Ya gotta love them EV's!
FWIW, I looked at the 5e3 PS using Duncan's PSU Designer, with a 5y3 recto. Gawd, like 20v of ripple at the first cap. More C at the first stage is a definite improvement.

[bob p]

I agree with stokes' recommendation of the EVM12L making a world of difference. Its an outstanding speaker. In some respects the 12L is a bit of overkill in a 20-watt amp, but I've always loved the 12L in that sort of application.

One cheaper alternative that still puts you in the same ballpark is the lower powered 100-watt EV Force 12. Its essentially the EVM 12L cone and basket with a "smaller" magnet and a 100-watt voice coil instead of the EVM's 200-watt or larger voice coil. Even though the Force magnet is "smaller," its still huge by speaker standards, and on a 5E3 the Force 12 will sound like the EVM 12L at a lower cost.

IMO either an EVM 12L or an EV Force 12 would be equivalent in a 5e3 circuit. You only need to step up to the 12L for a higher powered amp.

hth

[Bruce / Mission Amps]

Originally Posted by sportster4eva

Ya gotta love them EV's!
FWIW, I looked at the 5e3 PS using Duncan's PSU Designer, with a 5y3 recto. Gawd, like 20v of ripple at the first cap. More C at the first stage is a definite improvement.

The only problem with that statement is that it is not true.
More capacitance at the first node can be an improvement but I've run these fullbore output into all kinds of dummy loads and speaker loads while monitoring the AC ripple at the OT center tap.
20vac ripple is something I have never seen with a good 5Y3GT and a known good 16uF to 22uF first filter cap.

[sportster4eva]

Originally Posted by Bruce / Mission Amps

The only problem with that statement is that it is not true.
More capacitance at the first node can be an improvement but I've run these fullbore output into all kinds of dummy loads and speaker loads while monitoring the AC ripple at the OT center tap.
20vac ripple is something I have never seen with a good 5Y3GT and a known good 16uF to 22uF first filter cap.

I agree Bruce, that's why I was surprised by the simulation results
Listening tests prove the same thing. It's possible that the sim. I ran was flawed somehow. I don't put more than 20uf at the first cap, sometimes 40, and it's not been a problem. Big values at the first cap aren't really too good for rectifier tubes anyway..