5E3 schwitchable "less bass mod"?

[AndreasA]

I have a 5E3 clone with an eminence govnor speaker. The circuit is stock except for one component change the builder made to ensure that the 5V4 rectifier does not fry the 6V6 tubes.

I usually play unmiced blues gigs in small bars where I crank the amp. In some rooms the sound is perfect, in others the bass is too dominant. Cranking the tone compensates a bit however, I would like to be able to knock down the bass instead of just increasing treble.

Is it possible to make a "less bass mod" that I can schwitch on/off depending of the need at the particular gig? I imagine a switch somwhere on the chassis.

Andreas

[hasserl]

You could install two cathode bypass caps on V1, one would be the stock 25uf, the other would be something around 4.7uf. Put the 25uf on a toggle switch to engage/disengage it. You could also use a DPDT switch and do this with both V1 cathode and V2 also.

[tubeswell]

Another way is having the V1a 25uF cap(s) switchable altogether - i.e. just going down to a cathode resistor, like in the original champs. Put the switch on the ground side of the bypass cap. You will lose some gain this way, but the voicing should be more champ-like.

[Chris - CMW amps]

For less (boomy) bass:

- smaller cathode-bypass-caps like 4u7 or lower
- smaller coupling-caps like 0.047u or lower

Another way is having the V1a 25uF cap(s) switchable altogether - i.e. just going down to a cathode resistor, like in the original champs. Put the switch on the ground side of the bypass cap. You will lose some gain this way, but the voicing should be more champ-like.

The 5F1 schematics seen on the www and in books aren't correct.... the amps did have a 25u cap across the 1st cathode-resistor.

[tubeswell]

Ooops! Sorry I didn't know that, I was only going off the 5F1 schematic. Lifting the bypass cap will reduce bass (and gain) tho'.

[Gee]

In some rooms the sound is perfect, in others the bass is too dominant. Cranking the tone compensates a bit however, I would like to be able to knock down the bass instead of just increasing treble.

I find the same thing with my 5E3. Depending om the room, speaker and cab the 5E3 in standard form has too much imbalance in the bass for my ears. I ended up changing all the 0.1uF coupling caps for 0.047uF and then down to 0.022uF which is perfect for my ears and setup.

So you could try changing the first 2 coupling caps for say 0.022uF and then add a DPDT switch to add a 0.047uF in parallel with each of the 0.022uF coupling caps. That should give a fair amount of switchable bass control.

[Rick51]

I have been using an EQ pedal in front of the amp to cut down the bass. It works pretty well for me. Would changing the coupling cap values work better?

[black_labb]

i have a on-off-on switch to determine the cathode bypass cap on my 5e3 build. i put a 25uf cap on one side, and a 0.047uf cap on the other side of the switch, which seems to gives more of an emphasis on the upper mids in a 5e3 circuit. id suggest doing something like this to keep the sound from both cap combinations.

[cminor9]

which mod

Ok, so it looks like there are two possible ways to mod the 5E3 circuit to make it less bassy.

1) altering the bypass cap on V1
2) altering the coupling caps

Are they virtually interchangeable? Or are there differences tone-wise? I just am not sure which road to choose. I'll probably try both, but I'd like to hear some feedback on the differences between the two.

I definitely need to brighten up this amp for my Epi dot with Burstbuckers. I want to really brighten it up a lot, too, because it has bass to spare. I figure I can brighten it up a lot and then turn down the tone as needed if it gets too bright.

[d95err]

Ok, so it looks like there are two possible ways to mod the 5E3 circuit to make it less bassy.

1) altering the bypass cap on V1
2) altering the coupling caps

Are they virtually interchangeable? Or are there differences tone-wise? I just am not sure which road to choose. I'll probably try both, but I'd like to hear some feedback on the differences between the two.

The effect on frequency response is different with these methods. Changing the cathode bypass cap to a smaller value results in a shelving filter. This means the lower frequencies will be about 6dB lower than the higher frequencies (and merging from one level to the other in between).

The coupling cap (and following resistor to ground) acts as a highpass filter, where the bass frequencies will be lowered by 6dB per octave from the cutoff frequency and downwards. E.g. if the cutoff frequency is 300Hz, then 150Hz will be -6dB, 75Hz at -12dB and so on.

So, the cathode bypass method is more subtle, since the difference will never be more than about 6dB.

[cminor9]

d95err, thanks for the explanation. I would have never gotten that knowledge from staring at the schematic for ten years.

I replaced the .1 coupling caps on both channels with .022 caps. Much better to my ears than the Cathode bypass method, which just as you said, was more subtle. I really(!) dig the clean on my DeVille and didn't like this amp as much because it just didn't sound right with my favorite guitar (a dot), but now...my goodness, this amp is awesome. I'll never build another 5E3 with .1 coupling caps on the first stage. It made all the difference in the world.

If you need to shed some bass, I'd recommend doing it at the coupling cap.

[AndreasA]

Thanks a lot for all your suggestions. I will definitely have my tech do a mod like this.

Will a bass reduction like the ones you mention make the guitar sound more balanced across the strings - in the sense that the thicker strings will be less dominant than now? I find all of my other amps (66 super reverb, 69 marshall 1987 etc.) to sound more even across the strings regarding level. On the deluxe it is a bit harder to get these licks on the high strings to stand out. Opposite, I have to be carefull not to get notes on the low strings to stand out.

Edit: I will make another thread regarding the balancing across strings, as I assume this can not be reduced to a question of more or less bass.

Andreas

[Gee]

Will a bass reduction like the ones you mention make the guitar sound more balanced across the strings - in the sense that the thicker strings will be less dominant than now?

Yes, exactly. 0.022uF caps throughout did exactly this for my 5E3. The analogy I would make is that this is a bit like balancing the height of your pickups so that the each string has the same volume. With the 0.1uF coupling caps it sounded as if the bass side of each pickup was too high.

[AndreasA]

Gee, that sounds just like the answer I was hoping to get. Thanks a lot. I really appreciate your help as I love the amp but feels it can be at bit difficult to play due to this.

[Bruce / Mission Amps]

This is why I also provide the 5E3 tone-volume and HB mod kits.
The TV mod is a little more complicated but the HB mods are easy.
The HB kits come with all the diagrams plus, some different value coupling caps, a couple RC filters for gain and bass reduction, smaller cathode bypass E-caps for the 12AY7, biasing resistors and the SPST switches....my chassis are already punched for two small mini switches so you can bypass some of the mods for the stock sound and the parts for the Paul C fixed bias phase inverter mod.

http://www.missionamps.com/kits.shtml