5e3 deluxe issues (vol 2)

[Anthon]

I made a thread about my 5e3 build earlier... and it seemed like I solved all the issues, but after taking some distance for a week and listening to it once more,I guess it doesn't sound right after all.

When over driven, it has raspy kind of distortion artifacts. Sounds almost like something is vibrating in the cab, but this not the case (I checked with an external cab, it makes the same sound).
This is quite noticeable and doesn't sound right at all.

Other than that is sounds good.

Any clue to what might cause such an artifact would be appreciated.

 

[Anthon]

One more thing - it seems the problem is more noticeable with half power switch turned on...

This is how I implemented the half power switch.


https://robrobinette.com/images/Guitar/5E3P_Build/5e3_Half_Power_Switch.png

 

[johnheath]

Hi...

The 5E3 (Tweed Deluxe) is a wild beast in the sense that it was an early model of guitar amps... look at later models and you will see that they (Fender in this case) tweaked and changed a lot of stuff. That said I also must say that the 5E3 is a nice amp if you look for a bluesy sound at moderate volumes.

The circuit it self can be improved in many ways and still get that raw and gritty sound.

I have built four of them over the years and I have my share of trouble with them. If you would like to run your 5E3 with a lot of overdrive (fully cranked) it could be advisable to replace the two coupling caps after the phase inverter with a couple of capacitors with lower value to prevent the amp from "farting". Try caps with a value of 47nF or even 22nF perhaps.

Also the phase inverter in the 5E3 can produce blocking distortion when cranked... to prevent this you could add a resistor from the first plate of the phase inverter tube (not the inverter yet) to the grid of the second half of the same tube (the actual phase inverter). This would create a voltage divider before the signal enters the phase inverter lowering the gain in the phase inverter and at the same time reducing the risk of blocking distortion in the phase inverter.

And finally you could try to add some NFB by adding a resistor (try 47k - 68k) from the secondary of the output transformer to the cathode of the phase inverter tube (First triode!!!)

And before you do anything of the above check all connections compared to the schematic and also fiddle around with the layout of the cables inside the chassi (use a plastic or wooden stick and poke around and move the cables around and listen if your problems disappear.

It is a quite simple circuit but its is a bit untamed and sometimes you get it right with its original design but sometimes it could be advisable to do some modifications based on reducing the overall gain.

Someone else here might have a different point of view and they might be absolutely correct about it. It is worth a try though.

Best regards

/John

 

[Anthon]

The thing is, this is not my first 5e3.
I had to sell the previous one, but it sounded great. I did everything in the same way, except this time I used a OT with multiple output windings and I installed a half power switch.

I've built quite a few of these early Fenders (Champ, Princeton, Deluxe, Bassman) and they worked fine.
I had some issues, but it was always some obvious mistake.
I believe a bare bones original tweed amp should sound good, without any mods. Yes, it is an early amp with a lot of quirks - but it is still a production model, so consistent results should be possible. So I don't think jumping to mods is the right way to go here.

Here is a sample of it.

https://vocaroo.com/i/s0SaA15a2PZ5

I've been playing around with it, and it seems 16 ohm output causes more problems (16 ohm speaker on the soundfile)

On 8 ohms it is hard to tell if it has any of these  artifacts... unless I play it with half power - then you can hear it, but not as much as in the soundfile. Sound more like cracking, than distortion being raspy.

 

[CJ]

output transformer.

 

[Anthon]

output transformer.

Yes, at this point I suspect the OT or the way I organized the output jacks.
I always assume me doing something wrong (not the part), so I'll start by changing output wiring tomorrow.

I have an extra OT to try out, if it doesn't solve the problem.

 

[Anthon]

Well, it's not the OT.
I changed the wiring of output jacks, changed grounding of the outputs, even connected a another brand new Hammond 1760E, but the issue remains.

It seems the amp has these artifacts on half power mode only.
Strange - I've successfully implemented the same half power mod on a Bassman, and it works very well.

I'm not sure if it is the half power switch implementation that is wrong, or something else in the amp (and using half power only makes it audible, not being the cause). 

Btw, I installed 0.022uF caps after PI, 500kOhm resistor before the PI and a NFB resistor, but no significant improvement.

 

[johnheath]

Well, it's not the OT.
I changed the wiring of output jacks, changed grounding of the outputs, even connected a another brand new Hammond 1760E, but the issue remains.

It seems the amp has these artifacts on half power mode only.
Strange - I've successfully implemented the same half power mod on a Bassman, and it works very well.

I'm not sure if it is the half power switch implementation that is wrong, or something else in the amp (and using half power only makes it audible, not being the cause). 

Btw, I installed 0.022uF caps after PI, 500kOhm resistor before the PI and a NFB resistor, but no significant improvement.

Ok.

What if you download the 5E# schematic somewhere and open it in... let say in Paint and measure all the voltages and add it to the file in paint and post it here maybe?

Bets regards

/John

 

[Anthon]

Ok.

What if you download the 5E# schematic somewhere and open it in... let say in Paint and measure all the voltages and add it to the file in paint and post it here maybe?

Bets regards

/John

I think I got it... just moved the wires a bit around the half power switch and the problem seems to be gone now. 

Thanks for the advice.

 

[johnheath]

I think I got it... just moved the wires a bit around the half power switch and the problem seems to be gone now. 

Thanks for the advice.

Nice! Poking those wires around can be very useful

Best regards

/John