Does Varitone cut or boost midrange?

[bongomania]

The echo is much quieter than the original so no boost is occurring. That's not a good analogy.of these.

Think a bit further. Each echo is additional to the original signal. It doesn't matter if the first echo is 15%, the second is 10%, and the third is 5% of the original signal--the total is 130%. In feedback, you get all 130% (so to speak) in just microseconds, with the "extra" fully overlapping with the original signal.

 

[walterw]

so the total energy is still less than it would be with the tone cap disengaged, but since it's resonating at a narrow band, that band actually gets louder than it did with no tone pot engaged?

 

[Rob22315]

Think a bit further. Each echo is additional to the original signal. It doesn't matter if the first echo is 15%, the second is 10%, and the third is 5% of the original signal--the total is 130%. In feedback, you get all 130% (so to speak) in just microseconds, with the "extra" fully overlapping with the original signal.

No, it doesn't overlap the original signal in the case of the echo, the original signal is gone because there is no storage in the system. But your point is applicable to this circuit. A laser is a better analogy but one less understood. I'd say the energy builds up in the system for two reasons one is that you hit a resonance causing the system to store energy at that frequency, and the other is that the losses due to internal resistance and extraction of the signal are less than the energy coming from the input so the energy builds over time but limited to the point where the losses equal the input.

 

[bongomania]

Actually I was saying the overlap occurred in feedback unlike the case of the echo.

The reason pointing your mic at your monitor speaker causes a loud howling noise is partly because the input does not close off--this is key to resonance.

 

[SGD Lutherie]

so the total energy is still less than it would be with the tone cap disengaged, but since it's resonating at a narrow band, that band actually gets louder than it did with no tone pot engaged?

I think that sums it up.

 

[Rob22315]

I believe . . .

 

[aborgman]

I think that sums it up.

Yep.

 

[jags]

I still have a few questions on this but one thing has got me really stumped. The descriptions I've seen of the varitone circuit describe it as a midrange notch cut. Every circuit diagram I've seen shows the selectable cap array wired in series with the inductor and then dumping to ground The varitione itself is wired in prallel with the pup output, like normal tone controls.

With the hi-pass caps iand the lo-pass inductor going in series to ground, wouldn't this result in a mid-range boost at the jack? To get a mid-range cut, wouldn't the varitone output have to go to the jack rather than to ground?

Can someone please enlighten me as to what I'm missing?

It's amazing with all this electronics physics talk no one managed to answer the original question!!

The question was:

Does a varitone boost or cut the midrange?

Now obviously in a passive circuit there will be no way to actually have a significant boost so the question should be rephrased to: Does a varitone cut (scoop) the midrange or does it cut highs and lows causing the midrange to sound boosted? This would be a varitone with caps and and an inductor in series.

I have the same question as dheylen as all of the descriptions about varitones describe it as cutting or scooping out the midrange. And this is what I hear when I hear samples of it's use. However when I look at the schematics I see a capacitor bleeding off highs to ground and the inductor bleeding off lows to ground which should leave us hearing a lot of midrange. This is the exact opposite of what a varitone is described to do.

So to quote dheylen: "Can someone please enlighten me as to what I'm missing?"

Hopefully all you electronics experts out there can answer the simple question "cut mids or cut highs and lows" and provide a relatively simple explanation of how it works.

Thanks!

 

[SGD Lutherie]

It's amazing with all this electronics physics talk no one managed to answer the original question!!
Does a varitone boost or cut the midrange?

It's a notch filter, so it cuts midrange.

People did answer this back on the first page. Its amazing you missed it!

In post number 6:

It is a variable mid scoop. The capacitors select different frequency ranges of scoop

I said this back in post #7.

A real Varitone is a midrange notch filter, and uses an inductor. A rotary switch with caps only is called a decade control. The Les Paul recording guitar had one of those.

Maybe I should have made it clear what a notch filter is, but if you think about cutting a notch in something, you are removing that part. So scooping and notching are cutting that region out.

A notch filter is the opposite of a bandpass filter, which is what a mid boost would be, assuming it had some gain.

You can wire up a Varitone to only pass mid frequencies, but it won't boost.

 

[jags]

It's a notch filter, so it cuts midrange.

Great!! Thank you! But then I'm still puzzled in how it works. If the cap passes highs and the inductor passes lows and both the highs and lows are bleeded to ground, wouldn't that leave the mids to go to the output? Isn't that the opposite of what you just described as notching, scooping or removing?

So how does this thing notch the mids? That's my question and also the original question that dheylen posted.

Please explain. Thank you!

 

[bongomania]

The confusion is this: with a Varitone, the cap is not rolling off highs! The cap is selecting the center frequency of the notch.

 

[jags]

The confusion is this: with a Varitone, the cap is not rolling off highs! The cap is selecting the center frequency of the notch.

Believe me I do understand all of that. I'm an audio engineer and have operated a recording studio for over 20 years. I know all about equalizers, notch filters, etc. as I use them everyday.

My question is not what it does but how it does it. The circuit diagram of a varitone would lead me to conclude that the mid frequencies should be passed on to the output and the high and low frequencies will be bleeded to ground. Without the inductor this is what would happen as with a decade control. So how does having the inductor in series with a capacitor going to ground work to "notch" the mids out?

Hopefully this will be a simple question to answer because I can't figure it out!

Thanks!

 

[Rob22315]

Believe me I do understand all of that. I'm an audio engineer and have operated a recording studio for over 20 years. I know all about equalizers, notch filters, etc. as I use them everyday.

My question is not what it does but how it does it. The circuit diagram of a varitone would lead me to conclude that the mid frequencies should be passed on to the output and the high and low frequencies will be bleeded to ground. Without the inductor this is what would happen as with a decade control. So how does having the inductor in series with a capacitor going to ground work to "notch" the mids out?

Hopefully this will be a simple question to answer because I can't figure it out!

Thanks!

If the cap and inductor are in series going to ground, then the cap will be open for low frequencies leaving them to pass through the rest of the circuit, not shunted to ground. The inductor will be open at high frequencies leaving them to pass as well. Only at midfrequencies will the cap and the inductor both be working to allow those frequencies to be shunted to ground. The actual frequencies will depend on the values of the cap, the inductor, and a resistor elsewhere in the circuit.

 

[jags]

If the cap and inductor are in series going to ground, then the cap will be open for low frequencies leaving them to pass through the rest of the circuit, not shunted to ground. The inductor will be open at high frequencies leaving them to pass as well. Only at midfrequencies will the cap and the inductor both be working to allow those frequencies to be shunted to ground. The actual frequencies will depend on the values of the cap, the inductor, and a resistor elsewhere in the circuit.

So the inductor's "cutoff" point is at a frequency HIGHER than the capacitor's. That makes sense to me now. So as an example. The inductor lets all frequencies below 10K go to ground and the capacitor lets all frequencies above 1K go to ground. We now have everything from 1K to 10K going to ground so these are bleeded away from the output thus notching the mids. Frequencies below 1K and above 10K pass on to the output and are heard. The cutoff points are determined by the capacitor and resistor values in combination with the inductor. This of course is a rough analogy of how this works, and there are probably other factors in play, but it now makes sense of how it could work.

The problem I had in my head was that I thought the inductor was working below the cutoff point of the capacitor letting lower frequencies pass to ground. If that was the case it would have the opposite effect.

Thanks again for the explanation. I can finally get some sleep now!!

 

[Rob22315]

So the inductor's "cutoff" point is at a frequency HIGHER than the capacitor's. That makes sense to me now. So as an example. The inductor lets all frequencies below 10K go to ground and the capacitor lets all frequencies above 1K go to ground. We now have everything from 1K to 10K going to ground so these are bleeded away from the output thus notching the mids. Frequencies below 1K and above 10K pass on to the output and are heard. The cutoff points are determined by the capacitor and resistor values in combination with the inductor. This of course is a rough analogy of how this works, and there are probably other factors in play, but it now makes sense of how it could work.

The problem I had in my head was that I thought the inductor was working below the cutoff point of the capacitor letting lower frequencies pass to ground. If that was the case it would have the opposite effect.

Thanks again for the explanation. I can finally get some sleep now!!

Glad I could help. If you still have insomnia, you could take the component values in the circuit and actually calculate the corner frequencies for the notch. That ought to get you back in the mood for sleep quickly.

 

[jags]

Glad I could help. If you still have insomnia, you could take the component values in the circuit and actually calculate the corner frequencies for the notch. That ought to get you back in the mood for sleep quickly.

I'll take two of those and call you in the morning!!

Thanks!

 

[Meddle]

Hello all.

I've been reading a bit into varitone switches and would like to add my own input having installed one in a bass.

I decided to fit a Torres vass varitone in my Dearmond Jet Star II (defretted). The kit arrived quite quickly but shipped with a cheap plastic 2-pole 6-way switch. Not only did this come with a really long shaft which needed cutting down, the shaft was smooth and the supplied chicken-head knob would slip on the shaft. I was unimpressed by this cheap part. I had to buy a replacement from E-bay which luckily does the task much better.

As for the varitone itself I've found it to be varying degrees of useful. The kit is a true varitone as it has an inductor coil which goes after the capacitors on the ground-side of the circuit. Whilst its role is to preserve high frequencies I feel the inductor chosen doesn't match the frequencies present in a bass, so whilst a bit of string noise and clicking is allowed to remain in the signal it isn't that helpful. I would suggest fitting a two-way switch to take the inductor in and out of the circuit.

As for the settings, the first setting is just a straight bypass. The second setting is more lo-fi (taking off a wee bit of treble), the second is darker sounding, the third and fourth seems almost identical in tone, the fifth darker still and the last one (which is advertised as sounding 'out of phase') is a really deep and dubby tone which makes the D and G strings all but inaudible.

Quite a cool effect, but calling it a 'notch filter' is a little ambitious as you are still getting a massive tone reduction with little high end preserved by the inductor coil. Perhaps variable low-pass filter is more accurate, but with a passive signal it is never going to be that pronounced. I'm sure with some reworking it could be made a little better, for example I would have liked a less abrupt loss of high end after the first setting.

 

[SGD Lutherie]

Note that you can change capacitor values to alter the frequencies that the Varitone cuts at.

Also, different inductors will give different results. Since he's using a transformer, you can use the center tap on the side that's being used (assuming the transformer has a center tap), so give less of a notch. You can also wire up a tone control to dial in the amount of cut.

 

[bassclef112]

Here's a clever little varitone device that I picked up recently. Addressing the OP's original question, it incrementally rolls off the treble without losing the mids.

http://www.talkbass.com/forum/newreply.php?do=newreply&noquote=1&p=12942035



The only error in the video is the unit actually has 15 EQ effects with #16 being true bypass.

I've tried it a few times and I have to say it is dead quiet, and can always give you couple of positions for any particular bass that work well.

 

[Meddle]

That sounds even better. I have the tone control on my bass acting as a blend for the varitone... perhaps having it as an inductor blend is a better idea. Ideally I would want an inductor letting even more treble through, not just hiss and fluff at about 10k hz. No centre tap on the inductor, just an in and out on the sides of it.

On the other hand I do own an EQ pedal...

As for the stellartone Tonestyler, it does seem that they ironed out some of my misgivings with my own varitone switch. However it costs $119, so I would like to see what voodoo they have going on because that is a lot for a bunch of capacitors and a 16-way switch.