Bass boost

[Menryk]

I need bass boost in my amp.

Sometimes I feel like I'd like to have more bass tone.
Maybe it depends on not good speaker.
I have treble boost - SW1

But is it possible to add any simple bass boost to tone control or
in the last 1/2 ECC83 circuit?


See at the schematic, please.

[sluckey]

Bass boost is something that is more commonly found in a bass amp. Here's one that is very effective...

     http://el34world.com/charts/Schematics/files/sunn/Sunn_200s_only_schematic.pdf

You can also look at some of the Fender blackface bassman amps.

[Menryk]

Thanks,

you know I thought about bass amp a little bit.

I found interesting circuit Bass_boost_1 and what do you think to add this after tone control Bass_boost_2?

M

[jjasilli]

I do not agree that your "Average Tone Control" is average.   It would probable be simpler to cleanly SW between 2 different value "treble" caps at the top of the tonestack.


Another alternative is RAW:  install a fixed resistor under the Mid Pot which could be SW'd IN or shorted OUT of the circuit.


Also the .047uF coupling cap preceding the tonestack is a rather small vale which might be blocking bass to the TS.  (Though it's not clear to me how a higher value would interact with the feedback loop / filter.) IOW that circuit is also complex.  Maybe it's filtering away mids & bass. 

[Menryk]

Maybe you are right.
I took "average" tone control  from Peavey Classic 30.

I'm not sure that I understand your instructions.

So, FIRST I should change caps 270p and 0.022, yes?
Biger or smaller?

SECOND I should put extra resistor down between MID and ground with SW, yes?
Then will 20K + extra resistor, yes?

THIRD says that I need put bigger cap preceding the tonestack than 0.047, yes.

Do you have another completly tonestack, you use with good bass tone?


You know I don't want to much change original circuits but
I'll try to check all your ideas.

thanks
M

[jjasilli]

Member Tubenit has posted tonestack mods on the Forum which may be of help. 

[92Volts]

Thanks,

you know I thought about bass amp a little bit.

I found interesting circuit Bass_boost_1 and what do you think to add this after tone control Bass_boost_2?

M

That circuit should work but the description is misleading, at the bass "boost" setting, treble is cut. As you turn the knob towards "flat response", bass is also cut to match.

Like a volume control, you may perceive boost as you turn the knob up, but you're losing signal compared to not using the circuit at all. The flat setting has 10:1 attenuation of signal. The bass "boost" setting has at least 2:1 loss of bass from resistors alone, while loss at higher frequencies is still as much as 10:1 (depending on the frequency and size of the cap).

You changed the cap to 0.1uf when you redrew the circuit. Other than that I think it will work, but I haven't simulated it. Tone stacks aren't always happy driving loads that vary by frequency but as drawn the load is at least 470k at any frequency. Whether you can deal with 10:1 signal loss depends on what follows after.

[PRR]

.

[Menryk]

Thanks Guys,

I need to think about your ideas a little and apply to my amp, consecutively.

Menryk

PS. Where is the Tubenit' tonestack?

[jjasilli]

Good question! I can't find it either.  I just PM's tubenit.

[jjasilli]

Tubenit can't find the info either!  Guess it's gone.


Note that when people say they want more bass, the reality is usually they want more mids.  This is because the FMV TS, of which yours is a variation, causes the (in)famous mid-cut.  So, a solution is to reduce or eliminate the mid-cut.



The simplest thing is the RAW approach:  put a fixed resistor under the mid pot:  anywhere from around 30K - 500K.  To experiment: you can temporarily (alligator clip leads) place a 500K pot between the mid pot and ground, and dial in the "mid-boost" you like; measure the pot value at that rotation; then replace it with a SW-able fixed resistor.  This is simple and it "has to work"; if it doesn't then mids are already being lost beforehand, and other changes can be made.

[Menryk]

Thanks jjasilli,

you know, my whole preamp and TS I took from Peavey Classic 30 with my modifications (like digital reverb).

I did something similar - I added 1M resistor (by SW) between BASS POT and MID POT but ... without changes.

So, I will try to check your idea.

[MFowler]

Do not know what amp your starting with but if you have presence you can add resonance pot to get great low end.


Mark

[Leevi]

Filter?


http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php


/Leevi

[Menryk]

Mark (MFlower),

my amplifier is simply
preamp with TC is from Peavey Classic 30 and
I'd like to add digital reverb instead Peavey reverb and
power amp is SE EL84.

I'm not sure what you ask me (presence) so if you may, you could show me what do you mean?

Leevi,
thanks for link.
You know I am a fan of tube amp and have some experiences and I know some important things but theory doesn't help me.
If you would have some idea to my schematic it would help me, I suppose.

Menryk

[Leevi]

This is also pure theory and needs to be tested.



My  idea was to add a low pass filter to the signal way.
In this example it is placed before the tone stack (see the picture)


You can calculate the values for the components (R or C) by utilizing the Low-pass filter calculator.


http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php#answer1


Select first the cut off frequency eg. 400Hz and then either the resistor or capacitor value you want to use.
Let's select a resistor value 220K so you'll get from the calculator the capacitor value 1.8n.


/Leevi

[Menryk]

Thanks.

Now I need to think and apply all your ideas.
and
I think I need to check what is my problem - maybe middle tones.

[Leevi]

You can also utilize high pass/band pass filter calculators


http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php
http://www.learningaboutelectronics.com/Articles/Bandpass-filter-calculator.php


/Leevi