2x6V6 push-pull power amp - Fender Deluxe reverb copy

[Steve A.]

They do it with a high-pass filter, so it's probably fixed as they don't mention it being adjustable. I guess the feasibility of it would come down to the economics of making an adjustable unit.

I was thinking of someone designing their own crossover to cut out or attenuate the low bass frequencies that cause problems with some speakers. Being able to select different frequencies would be an extra. Any volunteers? I didn't think so.

Steve

[wizard333]

If how the bass affects the speakers is the issue, there has been a solution for decades: EVM12L. I dare you to try to bottom those out with guitar frequencies.

[Steve A.]

If how the bass affects the speakers is the issue, there has been a solution for decades: EVM12L. I dare you to try to bottom those out with guitar frequencies.

The Eminence Red, White and Blues speaker has been compared to the EVM12L- Glaswerks has used them in the less expensive cab for their top notch Dumble clones (which actually out-Dumble HAD!)- and is rated for 125 watts. I think that they are a lot like a nice vintage Jensen C12 but try as I may I can't fit them in a 10" cabinet.

I just thought that a high-pass crossover would be a cool project to build... (BTW would a load be required for the low frequencies that were blocked?)

Steve Ahola

[ReadyTeddy]

There is no such thing as "linear mixing". If the circuit is linear, mixing just won't happen.

All forms of non-linearity produce both harmonic distortion and IMD. It just depends on how you look at it. If you test with a single frequency, you'll see harmonics. Test with multiple frequencies and you'll see IM products too.

The only "gotcha" is that a perfectly symmetrical circuit doesn't produce even-order distortion harmonics, and doesn't produce difference frequencies or other even-order IM products. It doesn't really matter in practice, as even push-pull tube output stages happily unbalance themselves when overdriven.

Removing LF at the beginning of the gain structure and adding it back at the end is a classic high-gain trick.

I hope I'm not being pedantic, but linear mixing is used all the time--it is simply the addition or subtraction of two or more inputs. For example, for inputs A and B, the sum A + B has no nonlinearity.

[ReadyTeddy]

There is no such thing as "linear mixing". If the circuit is linear, mixing just won't happen.

All forms of non-linearity produce both harmonic distortion and IMD. It just depends on how you look at it. If you test with a single frequency, you'll see harmonics. Test with multiple frequencies and you'll see IM products too.

The only "gotcha" is that a perfectly symmetrical circuit doesn't produce even-order distortion harmonics, and doesn't produce difference frequencies or other even-order IM products. It doesn't really matter in practice, as even push-pull tube output stages happily unbalance themselves when overdriven.

Removing LF at the beginning of the gain structure and adding it back at the end is a classic high-gain trick.

Double post

[ReadyTeddy]

In the last year I was messing with a JFET preamp that used an opamp servo to set the JFET bias. The problem was a peak in the very low bass, usually between 5Hz to 10Hz of 3 to 6dB. The source of the circuit I was trying to work with came from the Sunn Stinger 60. The schematic is posted on Ampix, but I can't access it just now. Anyway, the circuit just didn't sound right with that low frequency bump. The most practical fix is to roll off the bass at the input to the stage, and I didn't want to do that so I abandoned that circuit.

The key to good sounding bass seems to be a slow dropoff in response staggered between stages, not all the poles right on top of eachother causing too fast a rolloff. A shelf type response works in many cases.

The hump was almost certainly caused by underdamping the bias-control feedback loop--been there.