Tweak the Freq's

Billy Murdoch · Post by **Billy Murdoch** » 26 Apr 2011 8:55 am

The majority of amps and preamps have a frequency control knob which can be set to a given freqency and then another knob is used to boost or reduce the chosen freq.,
It is generally accepted that the mids in the 800hz range should be reduced.
This does not always give (Me) the best results and sometimes I think that a graphic or even Parametric device would be much better, in that several frequencies could be adjusted.
I would welcome any input on the use of eq devices.
best regards
Billy

Georg Sørtun · Post by **Georg Sørtun** » 26 Apr 2011 10:49 am

Response should target what you are trying to achieve, so can you describe your gear/rig and what sound you are after?

Multiband "graphic" equalizers often work well if you only need slight "sloping" along the entire frequency range. They rarely hit right if you need a lot in certain areas.

FWIW: I have long since stopped bothering with what is "generally accepted", and often bypass or leave out equalizers (and as much else I can). If it then doesn't sound right either I'm at fault (playing) or some stage in the gear/rig isn't working properly.

Billy Murdoch · Post by **Billy Murdoch** » 26 Apr 2011 11:58 am

Georg,
Thanks for Your reply.
I refrain from mentioning manufacturers by name since the fault or cause probably lies with Me.
I have at one end, a Zum SD10 and at the other a T.C.SPLIT 12".In between I use either a tube preamp or a "regular" (SS?) preamp.
With the tube preamp I get a good sound and with the other one I get a Sterile lifeless sound.
I guess My question is ...If I could manipulate more than one frequency at the same time would My overall sound benefit or would I be better using the tube preamp only.
Best regards
Billy

Georg Sørtun · Post by **Georg Sørtun** » 26 Apr 2011 1:20 pm

Billy Murdoch wrote: With the tube preamp I get a good sound and with the other one I get a Sterile lifeless sound.

Short on info, but...

I interpret it as if you want a "warm" sound, like many tube stages deliver. You can get a touch of warmth in an SS pre-amp by gradually lowering frequencies from 500-700 Hz 3 to 6 db upwards to around 2 KHz, and keep it at that lower level further up. Should lower frequencies below 100 Hz gradually too to prevent energy-waste.

No way the average SS stages can be made to emulate tubes by modifying the frequency curve only though.

Tubes produce the warmer sound because they amplify non-linearly and distort softly - they are "slow", and they are provided with very limited negative feedback.

Traditionally built SS stages OTOH amplify linearly and distort sharply - they are "fast", and they are provided with quite a bit of negative feedback.

What you call "clinical sound" is most likely the sharp "transient distortion" in traditionally built SS stages, caused by the slight delays between stages being messed up by too much and too late negative feedback across transistor stages, a phenomenon known as "Transient InterModulation" (TIM) distortion.

The cure for TIM distortion is even faster and more linear transistors coupled with better balanced negative feedback, which is what upgrades where ICs are replaced with better ones is all about. A good SS amp should actually sound better than any tube amp, but that good SS amps are not common - especially not on our market.

No equalizer-settings can cure TIM, but lowering higher frequencies after a "TIM-infected" pre-amp may make it sound slightly less "clinical". An equalizer is "a crutch" here though IMO, so if your tube pre-amp sounds good I suggest you use it, and leave the SS pre-amp and equalizers out of the sound-chain.

Billy Murdoch · Post by **Billy Murdoch** » 26 Apr 2011 10:53 pm

Georg,
Many thanks for Your valued information.
It is very much appreciated.
Billy

Georg Sørtun · Post by **Georg Sørtun** » 27 Apr 2011 12:56 am

Billy, you're welcome.

As an addendum: I use only SS stages in my sound chain, and the unit I always insert pre VP does warm up the sound throughout to something a bit more tube-like - not by altering the frequency curve but by altering the dynamics.

I use a BOSS LMB-3 as first stage, set very moderate for just the warmer sound and then a little more for the illusion of added sustain. Depends on the PSG how natural it sounds with what setting, but all my PSGs get that little extra warmth and sustain I am after.
Might be worth a try, and I have found that the LMB-3 certainly doesn't hurt the overall sound through tube stages either.

Jim Palenscar · Post by **Jim Palenscar** » 27 Apr 2011 6:41 am

What some folks do with those is to set the boost way up- scan the freq to find the most offending one- then cut it~~

Dan Tyack · Post by **Dan Tyack** » 27 Apr 2011 10:56 am

Parametric or fancy midrange equalization can be very useful for recording or sound reinforcement. IMHO if you need a para eq or some sort of midrange sweep control to make a steel or guitar amp sound good, then you should find a better sounding amp to start with, then you won't need to tweek it.

Lee Baucum · Post by **Lee Baucum** » 27 Apr 2011 7:31 pm

Dan, I don't follow your reasoning. Are you suggesting that there are amps out there that sound great with the knobs set to zero, or flat? If so, what is the point of having the tone controls?

Dan Tyack · Post by **Dan Tyack** » 27 Apr 2011 7:48 pm

Hi Lee,

That's pretty much what I am saying. My favorite amps don't have a lot of fancy EQ regarding midrange. My current favorite pedal steel amp is the Little Walter, which has just tone and volume. The tone is usefull for backing off the treble. In terms of midrange controls. most of the amps that I have used with the sweepable mids are basically trying to overcome the unpleasant harsh mids you get with most transistor amps. The Little Walter has a midrange that I love. I don't think you could get a similar tone by tweeking EQ, it's just the basic sound of the circuit.

It's humble, but it's my opinion.

Georg Sørtun · Post by **Georg Sørtun** » 27 Apr 2011 10:35 pm

I agree with Dan, and I see no reason to be humble about it.

Non-musical (non-harmonic) intermodulation in transistorized circuits is the problem, and no degree of frequency tweaking can solve it - at best only mask it slightly. The only solution is better circuits with less non-harmonic (and harmonic) intermodulation.

Even the most basic tube-based audio circuits have a lot less of this non-musical (non-harmonic) intermodulation to begin with, and if they're really well built even the harmonic distortion is low enough to be ignored by the best of ears.

I will add that all but the simplest equalizer circuits introduce non-harmonic and harmonic intermodulation distortion, so by not having complex eq-circuits there the problem is reduced in both transistorized and tube-based sound chains.

Bob Hoffnar · Post by **Bob Hoffnar** » 27 Apr 2011 11:40 pm

In my experience any EQ systems used in addition to the most basic tone controls actually create more problems than they solve. I'm not sure if its the right term for it but I hear what sounds like phase cancellation when an external eq devise is used.

Lynn Oliver · Post by **Lynn Oliver** » 28 Apr 2011 10:18 am

Bob, I think that's the correct term. Here's an article on Filters & Phase Relationships that might be of interest.

Scott Appleton · Post by **Scott Appleton** » 28 Apr 2011 10:44 am

One way to help a SS is to put a tube in front. A Black box or a electro harmonix black finger compressor will help .

Olie Eshleman · Post by **Olie Eshleman** » 28 Apr 2011 2:01 pm

I have to agree with Dan on the use of eq. The right amp, in my experience will sound pretty close with no drastic eqing at all. I make my living doing sound reinforcement work and one of the most important tools for this is an equalizer.
That being said, I look at the equalizer on the amp in the same way I do when I'm at work, it's there to compensate for the room or the band/situation, to reduce frequency buildup. I don't think it's always wise to have your 'settings' set in stone and thus cripple the one of the tools you have to adjust to the room or band.
That being said, the right amp should sound good with out any eq in most, if not all, situations.
I also prefer tube amps in general, and have a longheld prejudice against solid state circuitry, but there must be truth in what Georg says, because my Webb is the clearest, fullest amp I've ever played steel through, tube or otherwise.

David Mason · Post by **David Mason** » 29 Apr 2011 10:22 am

It seems to me that right or wrong, the majority of people who are opposed to advanced tonal shaping are well past the early-thirties age group, and are consequently losing the ability to hear high frequencies at an ever-increasing rate. Notwithstanding the fact that speaker choice, transformers, cabinet type and size, even the instrument cords you use are also EQ decisions. You will hear here on the (primarily electric) steel guitar forum that graphic EQ pedals are mfg. by Satan and only used by idiots and deafmen, and over on the (primarily acoustic) mandolin forum they are revered as gig-savers.(?)

Women can hear much better than men above the 6K range - have you ever noticed that the music they like often even sounds different? When I was growing up, driving around in the car listening to music was one of the main sources of activity, and savvy engineers would check their mastering jobs by playing the mixes through car speakers. Now it seems as though kids are all iPod'd up, so I would assume engineers are checking the "in-ear" sound. Though, those kids may be stone cold deaf by their early thirties.

Regarding musical amplification, there have been quite a few accidents that resulted in things that sounded "great", at least based on sale and popularity. However, I don't seem to remember them settling out where the simplest were "better" and the complex ones were "worse" - in fact most of the "classic" sounds involved treble boosters, cheap coily cords, chains of effects straining at the limits of their 9-volt batteries (when they weren't turned off and sucking out frequencies)... certain amps like the Mesa/Boogies and Fender Super Twins were noted and lauded for their inclusion of a graphic EQ, so I suspect the notion that if you can just unearth the exact right tube and the exact right speaker tonal bliss is guaranteed (only losers need tone knobs?) is just another fad, soon to be buried under another avalanche of incoming myth, opinion and marketing distortions.

Beginning way back in the Eighties, nascent tone-gods Steve Morse and Eric Johnson began toting a Marshall (for overdriven mids) and a Fender (for clean highs and lows). By now, a solid majority of "big rock stars" are at least recording with multi-amp setups.... it's common to record several amps simultaneously, then choose the tracks used in mixing. And some of the very same guitarists who will sing paeans to "tonal purity" (i.e. no trashy stompboxes or "extra" EQ), like Santana and Joe Bonamassa, are now touring with FOUR-amp setups.

K.I.S.S. and all that.

Dave Grafe · Post by **Dave Grafe** » 29 Apr 2011 2:30 pm

All of those Fender tube amps that we think sound so great do not have flat response at all but are designed with a significant midrange cut when all the knobs are set straight up. While the headroom and power output may vary the main tonal difference between these various Fender amp models is the degree and frequency of this built-in cut. I imagine if you did a sweep test of the Little Walter or any other "great sounding" guitar amp you would find the same phenomena.

There are several reasons why cuts between 400 and 800 Hz seem to sound good, one is that this part of the frequency spectrum is also occupied by most other instruments and vocals, another is that most guitar pickups and all full-range speakers are much hotter in this range than the upper and lower fringes and to hear the higher and lower frequencies in a well-balanced fashion they must be compensated for, or "Equalized."

There is still no free lunch, all EQ circuits introduce some phase distortion, thus cutting what we don't want to hear will degrade the original sound much less than boosting what we want to hear.

Olie Eshleman · Post by **Olie Eshleman** » 29 Apr 2011 3:00 pm

I should clarify, an amp that sounds way to dark or bright with its eq set straight up, probably won't be a whole lot better with the settings drastically changed and is probably the not the best choice. And clearly the use of a midrange attenuator can do wonders to help you 'sit' in the mix. After all, having the capability to shape your tone is part of your art as a musician.
I have noticed that amps that I was told had an "additive" eq, or one where the natural sound of the amp is with the tone controls at zero, did not sound as good to my ears a passive attenuator, where the natural state is with the tone controls at 10.

Someone who knows more than I do, correct me if I'm wrong, but a Fender Twin's tone control is off with the knobs set at 10?

Dave Grafe · Post by **Dave Grafe** » 29 Apr 2011 7:00 pm

It may or may not be "off" but with all controls set at "10" there is a roughly 20dB cut at around 200 Hz, definitely not flat!

Bob Hoffnar · Post by **Bob Hoffnar** » 29 Apr 2011 7:47 pm

David,

You will hear here on the (primarily electric) steel guitar forum that graphic EQ pedals are mfg. by Satan and only used by idiots and deafmen, and over on the (primarily acoustic) mandolin forum they are revered as gig-savers.(?)

The function of EQ is vastly different for acoustic amplification and electric amplification.

Acoustic instruments primarily go direct. The EQ in the pre amp is the only thing in the signal chain before the sound board. EQ is very important in many aspects of amplifing mandos, dobros and all that.

With steel guitars you already have an amp with some sort of tone control pre amp section. To add another manipulation of tone can create some messed up sounds if you are not really careful. Dropped frequencies, ghost resonances, and ugly distortion artifacts. I learned about this by bringing my rig into major recording studios. The best and most highly paid ears in the world where helping me to get a good sound. Putting an extra EQ into a signal chain can help to mimic a good tone(like painting a Honda to look like a BMW) but does not generally work. Tonal problems need to be addressed primarily with technique and then the basic instrument and amp. EQ when used as a band aid tends to do much more harm than good in my experience.

I'm in agreement with your guitar forum guys about graphic EQ pedals

Olie Eshleman · Post by **Olie Eshleman** » 29 Apr 2011 7:47 pm

David, with the tone circuit bypassed altogether, would the amp exhibit the same 20 db cut at 200 hz? I guess my question is also, do the tone controls act as an attenuator only or does it boost as well as cut? If the latter is true, at what part of the dial would be neither a boost or cut? I guess it doesn't really matter, but I'm curious? I am referring just to a blackface twin in this instance.

Thanks in advance for the edification!

Lee Baucum · Post by **Lee Baucum** » 29 Apr 2011 8:08 pm

I may be wrong, but it appears there are two different discussions going on. I think maybe the original poster was talking about using a separate equalizer, in conjunction with the normal tone controls on an amplifier. It looks like some of the replies discuss the tone controls found on the amplifier and other replies are addressing the use of outboard equalizers.

Dave Grafe · Post by **Dave Grafe** » 29 Apr 2011 11:39 pm

Yes, I believe you are right, Lee.
In regards to the first most of these questions can be answered by Duncan's Tone Stack Calculator http://www.duncanamps.com/tsc/.
In regards to the latter I can only say from my own experience that with the added noise and distortion of even the best EQ circuits, if you want to add an outboard EQ or skip the amp controls altogether go for a top quality device like a Furman PQ3 or and Audio Arts 4100, both of which also feature decent preamps. And yes, a good unit well dialed in can sound superb.

Georg Sørtun · Post by **Georg Sørtun** » 30 Apr 2011 4:38 am

Reverting to the OP's case, and the main point in my response, for a moment...

Georg Sørtun wrote:
Billy Murdoch wrote: With the tube preamp I get a good sound and with the other one I get a Sterile lifeless sound.
[...]
No way the average SS stages can be made to emulate tubes by modifying the frequency curve only though.
[...]

...and then onto all else discussed here.

If a player is on the hunt for "unique sounds", adding equalizers and whatnot into any sound chain may get him there ... although all too often by accident. The final sound chain that creates "unique sounds" tend to be "incalculable", "not easily reproducible" and quite often "not even sustainable", and open for discussions by experts, non-experts and "nut-cases" (sometimes difficult to make a distinction) forever.

I will state that the fewer and better designed, built, balanced and adjusted links in the sound chain one can get away with in ones hunt for a particular sound, the better it will sound for longer to everyone who cares to listen ... quality and linearity always wins in the end.
Others will have to make up their minds if that statement holds water or not, or if they even care.