Using Subtractive EQ On Gigs - Anyone Else Trying This?

[ofajen]

Ask Fender I'm clueless on that, but that's how the Fender tone stack works.

Not quite true, but relatively speaking, it works that way. The passive tone stack on a Bassman, YBA-1, and similar amps comes after the second preamp stage (the one with the volume control) and is followed by another gain stage to make up for the loss before going to the power amp stage. You can see an analysis of this circuit at:

Fender Bassman 5F6A Tone Stack Frequency Response

Bottom line is that if you turn bass, mid and treble all the way up (the lowest graph on that page), the system response is nearly flat in the highs and lows and about -10 dB in the mids. So, relatively, the bass and treble seem boosted, but they are boosted by the overall circuit, while merely less attenuated by the tone stack itself.

Otto

 

[Stealth Fighter]

Boost? Cut? Compared to what? After all, it is all relative, isn't?

 

[ofajen]

Boost? Cut? Compared to what? After all, it is all relative, isn't?

Typically it would be output compared to input. In this case, the confusion is that the passive tone stack only attenuates, but there are gain stages before and after and a lot of overall system gain in going from the instrument signal to the power amp stage, so the relatively less attenuation of low and high in the tone stack ends up creating the effect of possible boost in those regions relative to the mids.

Otto

 

[Stealth Fighter]

Typically it would be output compared to input. In this case, the confusion is that the passive tone stack only attenuates, but there are gain stages before and after and a lot of overall system gain in going from the instrument signal to the power amp stage, so the relatively less attenuation of low and high in the tone stack ends up creating the effect of possible boost in those regions relative to the mids.

Otto

As I said, it's all relative. Therefore, using the Fender tone stack as an example, the bass control cuts the signal relative to the mid and treble, but since the overall signal is boosted form stage to stage, the bass signal is still boosted relative to the input, just not as much as the other frequencies. I think we are making to much out of proper eq technique. I just set the controls somewhere near flat for the particular amp I'm using and tweak to taste. YMMV.

 

[ofajen]

As I said, it's all relative. Therefore, using the Fender tone stack as an example, the bass control cuts the signal relative to the mid and treble, but since the overall signal is boosted form stage to stage, the bass signal is still boosted relative to the input, just not as much as the other frequencies. I think we are making to much out of proper eq technique. I just set the controls somewhere near flat for the particular amp I'm using and tweak to taste. YMMV.

Sure. I was just clearing up the confusion, because a passive tone stack doesn't boost, but the amp can effectively boost lows and highs, because the tone stack attenuates mids more. "Flat" on the YBA-1 is not everything set in the middle of range, but that is a very good sound! Flat is probably about bass at half, mids at max and treble at minimum, which is also a good sound. Whatever works!

Otto

 

[tonemachine]

This was something I decided to start using on gigs about eight months ago. The basic idea is that, if you want more bass, rather than boosting the low end you actually cut back on the high end (and vice versa etc) so that you're still left with what you want. I've found that the signal I'm getting is way more manageable, I can get more volume out of my amp because the signal isn't as hot, I'm never really in danger of clipping or peaking and I think it sounds nicer. There's still plenty of strong, solid low end but it doesn't sound as wooly and undefined as just cranking the low end. Also, if I have to play at louder volumes I find that the low end isn't as overwhelming when I use this EQ technique.

I got the idea from a producer friend of mine who uses this technique when he works on mixes in his studio and I just wondered if anyone else had tried it? I've been using it for a while now and the results have been great for me!

Try it and let me know what you think!

Yes, my Bongo 5, cut the bass but it might be expected on that bass more than most others. Haven't gigged any other basses lately but...

I noticed an interesting thing the other night watching a great local Soul/R&B/Disco/Funk cover band that I go see frequently. (They are one of the premier bands here- literaly world class level guys- they do weddings and corporate in addition to bars). Indoors, outdoors, big open rooms, packed small rooms- the bass is crucial and always sounds good, and I've never seen him go through PA . His EQ is an inverted smiley- cut bass and treble with mids boosted. This is for bass heavy music, mind you, so take note kids.

By the way kids, lest you succumb to "more spending is more better" and some of the rigid thinking in the world- he uses an old 350 watt hartke combo amp with a 15 speaker and a 210 extension (yes, mixed drivers!). He uses the same 1991 Fender Jazz 5 String every gig for years and years. This guy jams and always sounds great. So, work on EVERYTHING else before you start working on acquiring boutique-y stuff. No offense to that stuff but it's the last thing to worry about. Hands, ear, brain EQ.

 

[TheBass]

Not quite true, but relatively speaking, it works that way. The passive tone stack on a Bassman, YBA-1, and similar amps comes after the second preamp stage (the one with the volume control) and is followed by another gain stage to make up for the loss before going to the power amp stage. You can see an analysis of this circuit at:

Fender Bassman 5F6A Tone Stack Frequency Response

Bottom line is that if you turn bass, mid and treble all the way up (the lowest graph on that page), the system response is nearly flat in the highs and lows and about -10 dB in the mids. So, relatively, the bass and treble seem boosted, but they are boosted by the overall circuit, while merely less attenuated by the tone stack itself.

Otto

Thanks for that link. That's how I understood the passive EQ on all-tube amps. If you just look at the tone stack there is only cut, no boost, even with all EQ maxed (follow the link and look at the last graphic). Of course there is a make-up gain stage following which normally adds 20dBu gain. With that concept in mind it's much easier for me to manage the passive tone stacks on all-tube amps. Start with everything maxed and then cut to taste. This does not work for presence !

 

[ofajen]

Start with everything maxed and then cut to taste. This does not work for presence !

True, I seem to keep presence in the low to mid range quite a bit. I also tend to keep treble in the low range. I'd rather use that shelving than a standard tone control to reduce the high end.

I was playing the P-bass tonight thru the YBA-1 and bass is at max, mids around 8 and treble down at 2. Presence at 3. Sounds great as usual. Hard to actually get a bad tone out that amp, just a matter of which good tone.

Otto

 

[agedhorse]

A passive eq or "tone stack" is easier to understand when you consider the filter network as having insertion loss. The loss depends on the position of the bass-mid-treble controls, with the least loss with all controls fully clockwise. The controls govern the amount of loss in each band. The losses are subtracted from the overall (flat) make-up gain to get relative boost and/or cut.

 

[monkeyfinger]

I think that one has to consider the quality of the EQ in the amp. Some amps have better EQ circuits than others. This may have something to do with the op-amp design, phase cohesion, whatever. Some amps have loads of eq options that sounds like doo-doo no matter how much knob twisting you do. Others sound fantastic with just a few knobs. (The B-15 comes to mind.) In the studio, some EQs are known to be magical. Yet they do the same basic things that poorly designed EQs do. So what makes these so fantastic? It has to be more than just setting the Q, gain, and frequencies right. Clearly there is more going on than that.

 

[JimmyM]

A passive eq or "tone stack" is easier to understand when you consider the filter network as having insertion loss. The loss depends on the position of the bass-mid-treble controls, with the least loss with all controls fully clockwise. The controls govern the amount of loss in each band. The losses are subtracted from the overall (flat) make-up gain to get relative boost and/or cut.

Cool, thanks for the explanation, Andy. I'd still maintain that the net result with the Fender stack is boosts only on treble and bass and cut only on mids, but that's a very easy to understand explanation.

 

[monkeyfinger]

There are a couple of more complexities to the Fender tone stack than just boost bass and treble, cut mids. The whole filter system is dependent on the gain settings before the EQ. Also the frequencies affected by the changes to one control will be affected by the other controls. So the center point of the mid frequency cut will vary with the bass and treble controls. it is a very interactive system. That is why it can be so confusing to some people. It's works best if you try not to think too hard about it and just twist knobs until you find something you like. If the sound works for you then you are good. Otherwise look elsewhere. Personally, I think it works better for guitar than bass.

 

[two fingers]

Well, it's proper technique for PA, but I ain't running a PA I used to be into that, but then Roger Baer said to me, "If you're getting the sound you want, what difference does it make where the knobs are?" He was right. So I don't sweat it anymore. Where the knobs end up is all good as long as I get my sound.

Well stated by both you and Roger.

 

[Lowbrow]

Funny to read the OP as I just got in from a gig - while doing a line check, my guitarist suggested I add lows and I instead cut treble. Made him happy without adding woof.

 

[tallboybass]

I read a great post here on TB one time that helped a lot. He said to set all eq knobs straight up except the bass knob, turn it all the way down. Then play and slowly add lows to get the right amount of body to the sound. It helped me tremendously! You can still tweak from there but i found i didn't need to, my GK amp sounded great. Try it!

 

[Hugh_R]

I read a great post here on TB one time that helped a lot. He said to set all eq knobs straight up except the bass knob, turn it all the way down. Then play and slowly add lows to get the right amount of body to the sound. It helped me tremendously! You can still tweak from there but i found i didn't need to, my GK amp sounded great. Try it!

Interesting idea man! I remember once being told to do something similar but setting all dials to 0 the brining in each individual band. You're way sounds a lot quicker though!!!

 

[Jim C]

In regards to amp EQ, the Q of the filter (how wide the bandwidth) will yield different results from amp to amp whether fixed EQ or quasi-parametric.
IMO you can get apples to apples comparing fully parametric EQ's.
Also, the "baked in EQ" of an amp can also change knob settings from amp to amp.

For an example, SWR SM400 amps are pretty bright with the treble turned down compared to others.