Some 5E3 questions (too loud/hot?!)

[Meshugana]

Hi there,

My name is Diederik van de Bunt and I am a guitarist from the Netherlands and like to build my own effect pedals and amps. I found a lot of interesting stuff here on this site so I decided to sign up.

Last weekend I built my first 5E3 kit which I ordered from Tonefactory, For all your tubes and guitar parts and more! (very nice guys)

Everything is working fine. But I have some questions:

- This amp has got no master volume, but this amp is very loud. When I turn the Volume pot a bit open to 1-2 it is so loud that my neighbors can hear me. Is this correct? Is there a possibility to get the volume down?

- The tubes become very hot. Hotter than my EL34’s from my 50 Watt Koch.

- The sound of the amp is nice, but I miss some mid's en high's. Is there een possibility to decrease the bass or to boost some mid's and high's frequencies?

- Is it possible to adjust/lower the bias? The power tubes are around 40 mA at plate current of 390 V. Or is 40 mA fine?



Best regards,

Diederik

[MWJB]

1) The volume controls on the 5E3 a re wired "backwards" compared to most amps, which have their volume pots wired as traditional voltage dividers. One byproduct of this is that the volume "ramps up" very quickly. Bruce Collins does a "Vol/Tone" mod kit that addresses this issue. However, a 5E3 can make around 18W so perhaps you need a quieter amp if you are to avoid disturbing the neighbours?

2) 5E3 is cathode biased, cathode biased amps run their tubes at very high idle currents (like the 40mA you read), compared to maybe 20-25mA for a fixed bias 6V6 amp. Higher idle currents create more heat...it comes with the territory. I suspect that your Koch amp is fixed bias too...I am aware of fixed bias amps that run tubes that are still cool enough to touch after a few minutes playing (no, don't try it, just take my word for it!). Cathode biased EL34/6L6 amps normally run 50-60mA per tube and undoubtedly get hotter that your 5E3.

3) Smaller preamp coupling caps at V1 pins 1 & 6 are a common mod, try 0.022uf. Also some folks find smaller cathode bypass caps help, perhaps 5uf at V1 & V2, or try 25uf at v1, 0.68uf at V2? If you use humbuckers, you might want to search "5E3 Humbucker mods"?

4) 40mA per tube @390v is the higher end of "normal", try a 300, or 330ohm cathode resistor & see what you prefer the sound of. I like a 330ohm cathode resistor as this will often allow the use of a 5V4 rectifier (slow warm up, tighter response). You don't want the plate current to drop below 30mA per tube.

[pdf64]

What tube type have you got in V1?
The amp was designed for a 12AY7, which has about half the gain of a 12AX7.
See
http://www.schematicheaven.com/fende..._5e3_schem.pdf

Your tone control, when set to max, should give a significant treble boost on one channel, the upper one in the link above (on the other it works as a treble cut only control). If that's not happening, you might have wired it up wrong.

[Meshugana]

Thx for you answer. I just ordered my Tone/Volume and Humbucker Mod at Missionamps.com . I hope it will arrive soon.


About your answer on the third question:

- coupling caps at V1 pins 1 & 6, which are these? (are these the most 2 right 0,1 uF caps? ( see: https://taweber.powweb.com/store/5e3_layout.jpg )

- cathode bypass caps, which are these? (referred to the lay out)


Regards,

Diederik

[Meshugana]

What tube type have you got in V1?
The amp was designed for a 12AY7, which has about half the gain of a 12AX7.
See
http://www.schematicheaven.com/fende..._5e3_schem.pdf

Your tone control, when set to max, should give a significant treble boost on one channel, the upper one in the link above (on the other it works as a treble cut only control). If that's not happening, you might have wired it up wrong.

I have a 12AY7 as first pre-amp tube. So that's fine.

I will check out how it sounds with max tone on all channels.

Thx!

Regards,

Diederik

[Meshugana]

Oh, and another question:

- When I put my speaker cable in de extention cab output from my 5E3 the volume is 20% of the original. Is this normal?

[MWJB]

You mean, when you add an extension cab? No, that's not normal.

If you mean that when you plug the in-board speaker into the ext jack, again, no this is not normal and you shouldn't be doing it anyway. The speaker jacks should be set up so that the appropriate load (8ohms for a 5E3) is always plugged into the main speaker jack. Unplugging from this jack should cause the switched terminal on the socket to ground the signal out completely (thus there should be no signal at the ext jack either), but you should NEVER power up an amp without a speaker connected to the main speaker jack...it's the fast track to blown tubes & OTs!

Please post pics of speaker & ext jack wiring.

[Meshugana]

I will post some pics when I have them.

I just took the speaker jack from the primairy speaker output in to the extention output. So there was no jack in the primairy speaker output. I could still hear some guitar, but the volume was way down.

You say that I should not hear anything when I plug in to the extention output only?

[MWJB]

"You say that I should not hear anything when I plug in to the extention output only?" - most importantly, what I am saying is that you should not be doing this, I doubt most people would know if that is normal or not, because they would not do it...unless they were trying to damage their amp/tubes. Do not turn on your amp unless you have the speaker connected to the main speaker jack.

[Meshugana]

"You say that I should not hear anything when I plug in to the extention output only?" - most importantly, what I am saying is that you should not be doing this, I doubt most people would know if that is normal or not, because they would not do it...unless they were trying to damage their amp/tubes. Do not turn on your amp unless you have the speaker connected to the main speaker jack.

For me that is not most important. Off course I always connect a speaker of power soak to my main input. But I was wondering what if I just put a speaker to the extention output. I just tried it for 3 sec. It won't harm my amp too much I hope.

So again, "You say that I should not hear anything when I plug in to the extention output only?"

[MWJB]

"So again, "You say that I should not hear anything when I plug in to the extention output only?" - Like I said, the speaker jack, if wired correctly, should short the OT secondaries with nothing plugged in, so I would assume no sound...but I wouldn't try it for fear of damaging things.

[Meshugana]

"So again, "You say that I should not hear anything when I plug in to the extention output only?" - Like I said, the speaker jack, if wired correctly, should short the OT secondaries with nothing plugged in, so I would assume no sound...but I wouldn't try it for fear of damaging things.

Okay thanks. I will post some pics of the wiring a.s.a.p.


I'm thinking about to make the ext. output a 4 ohm output. How can I do this? Just put an 4 Ohm resistor in series? (so the sum of speaker en resistor is 8 Ohm)

[MWJB]

"I'm thinking about to make the ext. output a 4 ohm output. How can I do this?" You buy a new output transformer with 4ohm & 8ohm output taps & wire both speaker sockets as non-shorting jacks (just 2 terminals).

[Meshugana]

"I'm thinking about to make the ext. output a 4 ohm output. How can I do this?" You buy a new output transformer with 4ohm & 8ohm output taps & wire both speaker sockets as non-shorting jacks (just 2 terminals).

Hm, ok. Which OT do you recommend? Any suggestions?

Last question:

Is it possible to connect a 4 Ohm speaker to the 8 Ohm output with a 4 Ohm resistor in serie with the speaker lead? (4 Ohm + 4 Ohm = 8 Ohm), or will I lose tone/volume or something?

[MWJB]

It would have to be a very high value resistor (25-30W minimum) ...you'd have to tell us what the effect on sound would be...I would imagine a drop in efficiency. Why do you want to do this?