Tight bass response question?

[Rod]

What components from a guitar amplifier circuitry should i change to have a more tight bass response?

It's possible to have a variable tight bass response in a amp circuitry?


Thanks.

[soundguruman]

What components from a guitar amplifier circuitry should i change to have a more tight bass response?

It's possible to have a variable tight bass response in a amp circuitry?


Thanks.

A lot of it has to do with the speaker and pickups but...
making the bias hotter in a tube amp will also help quite a bit.

[JoeM]

Make sure you have good filtering on the B+ and screen supply. Making the NFB variable would affect the low-end 'tightness' too.

[Chuck H]

"Tight bass" is designed into an entire amp. Since there are MANY things that can cause loose bass I don't know how to help you unless you know why your amps bass isn't tight enough. Can you tell us what kind of amp you have? How you set it up and what kind of guitar you're using. Don't skip any pedals or effects processors.

[R.G.]

As SGM mentions, the pickups and speakers have a lot to do with it. So do the speaker enclosures.

The issue of "tightness" turns on what the word means. Obviously, that's a little foggy. What most audio people think it means is "well damped", in the controls engineering sense of "most accurate response to a transient". Starting from the speaker and going back, the speaker cone itself is both electrically and mechanically damped. Electrically is what you're hoping to get a knob to dial in. Mechanically is controlled by the physical construction of the speaker itself - how stiff the surround and spider are on the speaker, the cone mass, etc., and the magnetic field intensity and distribution of the magnet compared to the coil.

Most speakers have big resonance where their low frequencies start to fall off. Or, more accurately, the frequencies start to fall of where the resonance is. That resonance can be damped to some degree by the acoustic properties of the physical construction of the speaker enclosure. In reading about speaker enclosure design, you'll only be about a paragraph into the writeup when you encounter "low frequency response" and "damping".

The amplifier can help damp the speaker motion to some degree, but not perfectly. Modern amplifiers have a high "damping factor". That means they will produce almost any amount of current to force the voltage to be correct on their outputs. This property amounts to how tightly they have a grip on the speaker coil electromagnetically. Solid state amps have a higher damping factor than tube amps. It is possible to dial this in a bit. But its effect on the mechanical and acoustic damping properties of the speaker are not perfect. Resistance in series from the amplifier to the speaker decreases this damping, so long, thin speaker wires can un-damp even a superbly damped amplifier.

It is possible to dial in a sloppier electronic response, but it is hard to make it counteract the physical setup at the speaker cabinet and speaker itself.

Further back, the pickups can feed in a "sloppier" sounding signal. The amplifier can then more accurately/tightly amplify the sloppier signal. How much control you have on this is only speculation.

[soundguruman]

Make sure you have good filtering on the B+ and screen supply. Making the NFB variable would affect the low-end 'tightness' too.

Yes Indeed
Having plenty of reserve in the power supply to avoid sag,
Having higher voltage in the preamp to get max headroom, is good practice.
Having good speakers, such as EVM...

[Chuck H]

We can get semantic or technical about it. But with a vague question like this there's no way to answer it. Is the OP a 5e3 player with a case of the farts or a metal player that just can't get enough "chug". Two different problems with different possible solutions.

[Rod]

Make sure you have good filtering on the B+ and screen supply. Making the NFB variable would affect the low-end 'tightness' too.

HI! I'm a noob with some knowledge in electronics, and knows the basic operation of guitar amplifiers, i'm not understanding what you mean by:

- "good filtering in the B+ and screen supply", can you explain me this? what is the B+?
- "NFB variable", what is the NFB?

thanks.

[JoeM]

Rod,

What amp (or amps) are you referring to? Do you have a schematic?

[Rod]

Rod,

What amp (or amps) are you referring to? Do you have a schematic?

i'm referring to the AX84.com - The Cooperative Tube Guitar Amp Project amps.

[Chuck H]

Are you considering building one and how to approach it? Or are you trying to improve an existing amp? There are a lot of different amps built there. Not all the same enough to be lumped together. Can you pick a specific model? What kind of music do you play?

[hasserl]

HI! I'm a noob with some knowledge in electronics, and knows the basic operation of guitar amplifiers, i'm not understanding what you mean by:

- "good filtering in the B+ and screen supply", can you explain me this? what is the B+?
- "NFB variable", what is the NFB?

thanks.

Good filtering means plenty of capacitance, B+ is the rectified and filtered DC power supply for the amp. High values of capacitance in the DC power supply will keep the power supply from sagging under conditions of high current demand. When the power supply sags under heavy loads it causes several things to occur, one of them being distorted bass frequencies. Increasing the capacitance (filtering) helps prevent this, but can also make an amp feel stiff. Some people like that, others don't. It is a subjective quality that really depends on the individual player and his/her likes/dislikes.

NFB stands for Negative Feedback, a small part of an electrical signal that is fed back upstream to a point where it cancels out similar frequencies. In this case he was referring to "global NFB", where part of the output signal being sent to the speaker is returned back to an earlier part of the signal chain, where it cancels similar frequencies in the signal, which helps to reduce distortion of the signal and also to increase damping of the speaker. Negative feedback amplifier - Wikipedia, the free encyclopedia

Hope that helps

[loudthud]

HI! I'm a noob with some knowledge in electronics, and knows the basic operation of guitar amplifiers, i'm not understanding what you mean by:

- "good filtering in the B+ and screen supply", can you explain me this? what is the B+?

B+ is the main high voltage fed to the tubes. With smallish filter caps like found in guitar amps, usually 50uF or lower, distortion increases at bass frequencies. You can actually see a rectified version of the output signal riding on the B+ in push pull amps. With larger filter caps, 100uF of higher, the distortion is reduced and clean power at bass frequencies is increased. Not all players like the sound of increased filter caps.

[Rod]

Are you considering building one and how to approach it? Or are you trying to improve an existing amp? There are a lot of different amps built there. Not all the same enough to be lumped together. Can you pick a specific model? What kind of music do you play?

well i'm thinking in build the AX84 Hi-Octane Tube Guitar Amplifier Project, after this i want to tweak some things to taste, and the tight bass response is one of them.

[Rod]

Can someone point me and show me in the AX84 Hi-Octane Tube Guitar Amplifier Project schematic, what i do have to change to have good filtering on the B+ and screen supply?
What caps do i have to change?

How can i had also a NFB circuitry to the schematic?

Thanks, everyone for your help.