Best and quietest layout for a Fender 5E3 amp.

[Mark]

I have been fixing a 5E3 which has been a good experience as I would like to build one.

Along the journey I have found that the stock layout isn’t that wonderful. Given that adjusting the volume controls is a means of changing the timbre of the amp, removing hiss and hum is advantageous to the amp.

I’m only aware of the Rob Robinette optimised layout and layouts such as the Ceriatone seem similar to the original layout.

While I really like the Rob Robinette amp page, I didn’t particularly like the master volume that he recommended. So I’m a little sceptical now about the layout.

I would appreciate recommendations for a superior layout for the 5E3 amp.

Thanks for your help.

[Stevem]

Where is the wiring layout for the power supply filters in that amp.

There's a way to wire them for the least level of 120 hz hum and without that layout I can't judge if it's been done right or not.

That wiring layout shows no output stage cathode resistor or bypass cap on pins 8 so even if you build it, the amp would not work.

One way to have lower AC filament hum out of the amp is to connect the power transformers heater center tap to pin 8 of either output tube.

I don't see why a5E3 model needs a master volume control, the tone soul of this amp that folks love is its collective sound ( preamp and output section ) when driven hard.

A master volume implemented will change that wonderful ratio of preamp distortion and output stage distortion, so at that point I need to ask why the hell even build a 5E3?

If you need less volume then build a smaller wattage amp!

[pdf64]

Rob's optimised 5E3 layout looks good to me, it seems to follow Merlin's guidelines.
Whereas I agree that the simple master volume he suggests for the 5E3 is bad, and there’s a few threads in various forums where myself and other have suggested an easy way to improve it. The users then seem happy with it, though I agree 'in a 5E3, what's the point?'.
However, other users seem quite happy with Rob's simple master volume 'as is'

The Ceriatone layout has room for improvement, though in reality, with a low gain amp like a 5E3, it may not cause a problem per se.

[sluckey]

Where is the wiring layout for the power supply filters in that amp.

There's a way to wire them for the least level of 120 hz hum and without that layout I can't judge if it's been done right or not.

That wiring layout shows no output stage cathode resistor or bypass cap on pins 8 so even if you build it, the amp would not work.

One way to have lower AC filament hum out of the amp is to connect the power transformers heater center tap to pin 8 of either output tube.

The Ceriatone layout shows the cathode R/C and the filter caps on the left end of the board and the filament CT is connected to power ground. Rob's layout does elevate the filament CT.

[Mark]

I will reply tomorrow as it’s now late, thanks for the replies.

IMG_3867.png

[martin manning]

I imagine this 5E3 layout quite some time ago. Never built with it, but after giving it a quick look I don't think I would change anything.

[Mark]

Hi Martin, thanks for your reply. The earthing looks good in the diagram, but the location of the 0.022uF is problematic as far as I can tell. It forms a feedback loop with the input jacks in the bright channel. The issue isn’t noticeable unless the contacts of the jack are apart and the resistance of the input is high. I suppose that I could ignore it, but I’d rather not.

IMG_3869.jpeg

[Mark]

Where is the wiring layout for the power supply filters in that amp.

There's a way to wire them for the least level of 120 hz hum and without that layout I can't judge if it's been done right or not.

That wiring layout shows no output stage cathode resistor or bypass cap on pins 8 so even if you build it, the amp would not work.

One way to have lower AC filament hum out of the amp is to connect the power transformers heater center tap to pin 8 of either output tube.

I don't see why a 5E3 model needs a master volume control, the tone soul of this amp that folks love is its collective sound ( preamp and output section ) when driven hard.

A master volume implemented will change that wonderful ratio of preamp distortion and output stage distortion, so at that point I need to ask why the hell even build a 5E3?

If you need less volume then build a smaller wattage amp!

I have found that to be the case too, but the owner wants to be able to use it at home without the excessive volume. I tried a 50 watt Weber Mass with the amp and result was much the same as using a master volume. I found the Mass works well with Marshall’s but not so good with Fender style amps.

So far the PPIMV looks like being the best option.

The grounding is very similar, if not the same as the as Martin's picture.

[Mark]

Rob's optimised 5E3 layout looks good to me, it seems to follow Merlin's guidelines.
Whereas I agree that the simple master volume he suggests for the 5E3 is bad, and there’s a few threads in various forums where myself and other have suggested an easy way to improve it. The users then seem happy with it, though I agree 'in a 5E3, what's the point?'.
However, other users seem quite happy with Rob's simple master volume 'as is'

The Ceriatone layout has room for improvement, though in reality, with a low gain amp like a 5E3, it may not cause a problem per se.

Thanks for the reply, it does look similar to something Merlin would suggest. It seems part of the joy with a 5E3 is hitting the phase splitter hard, which is why I will go with PPIMV.
The problem with Rob’s MV circuit is leakage. At zero volume the 1M pot forms a voltage divider with the 56K resistor.
This isn’t a big problem when the amp is “clean” but when the amp is driven hard the volume is louder than desired.

[Mark]

Where is the wiring layout for the power supply filters in that amp.

There's a way to wire them for the least level of 120 hz hum and without that layout I can't judge if it's been done right or not.

That wiring layout shows no output stage cathode resistor or bypass cap on pins 8 so even if you build it, the amp would not work.

One way to have lower AC filament hum out of the amp is to connect the power transformers heater center tap to pin 8 of either output tube.

The Ceriatone layout shows the cathode R/C and the filter caps on the left end of the board and the filament CT is connected to power ground. Rob's layout does elevate the filament CT.

Thanks for your input Sluckey, I noticed the elevated heaters too but wasn’t sure it would make a lot of difference.

[pdf64]

... I noticed the elevated heaters too but wasn’t sure it would make a lot of difference.

In a 5E3, elevating the heater circuit has the benefit of pretty much eliminating heater buzz being an issue, as its cause is almost always imperfect h-k insulation in early stage valves, eg the 12AY7 here.
As I see it, there seems no reason not to do it

Unless you're going old school and using 1 wire and the chassis to conduct heater current.

[Mark]

... I noticed the elevated heaters too but wasn’t sure it would make a lot of difference.

In a 5E3, elevating the heater circuit has the benefit of pretty much eliminating heater buzz being an issue, as its cause is almost always imperfect h-k insulation in early stage valves, eg the 12AY7 here.
As I see it, there seems no reason not to do it

Unless you're going old school and using 1 wire and the chassis to conduct heater current.

I hear what you are saying, it’s a good idea so why not.

[martin manning]

...but the location of the 0.022uF is problematic as far as I can tell. It forms a feedback loop with the input jacks in the bright channel. The issue isn’t noticeable unless the contacts of the jack are apart and the resistance of the input is high. I suppose that I could ignore it, but I’d rather not.

Aren't you creating a situation that will not occur in normal use?

[jabguit]

My $0.02....

It may not be an option but I've built my 5E3 derivatives in BF Vibrochamp aluminum chassis AND every design that utilizes a cathode follower (cathodyne PI) should have heater elevation, IMHO. Noise and hum levels are noticeably less than in my 5E3 in the original type chassis - I think it may be due the proximity of the PT to other components whereas in the original every thing is much closer - even thought the dimensions of the VC chassis are not much different - just that tubes and PT are on the same plane. My theory may be wrong but I think this has something to do with it.

Layout:

Sprint.png

amp:

Sprint 07.jpg

chassis:

tt-ch041.pdf

[pdf64]

Aren't you creating a situation that will not occur in normal use?

Some guitars, even some freestanding valve preamps etc, use a 1M volume control, so resistance at the amp input could be up to 250k when that's set electrically halfway.
Plus it's common to swap in a 12AX7 into V1 of a 5E3, which could exacerbate the low margin of stability issue.