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Author Topic: What makes for a good clean channel?  (Read 618 times)

edvard

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What makes for a good clean channel?
« on: February 15, 2021, 05:10:37 AM »
Back in 2018, I was pondering creating a basic SS amplifier that had all my best ideas in one box.  Now it's 3 years later and I still haven't built it, but I've been breadboarding!  I've re-thought my opinions on 2-channel amps, and eventually came around to a new question... Is the clean channel nothing more than the default when you turn off the dirt?  Like the wire that goes straight from input to output when you switch a pedal off?  That sounds so boring, but can there be more to it? 

I worked up an idea of making the clean channel run through a tone control and then through a single gain stage, which is how tube amps of yore were laid out.  I'm not trying to purposefully emulate tube anything, it just struck me as a novel design decision that will alter the response of the gain stage and maybe introduce some pleasing audio anomalies.  Or at least, that's what I'm hoping...

What do you folks think are essential elements of a good default clean channel?  Squeaky-clean crystal clarity?  Just a little grit on the top for flavor?  Tone shaping ideas?
  Some simple compression/limiting maybe? (Yes, Phatt, I remember your suggestion of the simple compressor.)   

Enzo

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Re: What makes for a good clean channel?
« Reply #1 on: February 15, 2021, 06:57:13 AM »
Crystal clean clarity?  Foo, that would simply be a PA system, and we know that does not make a good guitar amp.   What you think of as clean in a guitar amp is not really very clean.  It just doesn't have the shrill raspy edges of dirt channels.

Go to DUncan amps and download the tone stack calculator and explore the tone stacks, you will see their response curves are not flat.  Putting all the tone controls at center on your old Fender is NOT the flattest setting.

phatt

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Re: What makes for a good clean channel?
« Reply #2 on: February 15, 2021, 08:15:47 AM »
Hi Ed,,Try to keep in mind that there is no one section of a complete system that will reap magic,,
You build the sound/Tone you want out of what is mostly basic circuits most of which have been around for years.
If you want Clean then I take it you are talking about electric guitar?

In that case the clean will benefit from a little edge. (As Enzo just mentioned)
(My Cab sim, compressor, Phabbtone does that for me)

Regards OD and multi channels on amps,,, Been there done that and failed?
Pedals are far easier to get to where you want. It will depend on what styles you want to emulate.
For me it's just older rock and blues which is built from the little rattle of *Mictesters* Comp which is always on.
Then I add a home designed germanium clipper (that is my clean boost with a little more edge and OD) sweet. :tu:

For MORE heavy rock stuff (think ZZtop) I add a Boss OS2.
For all out scream I add a Boss SD1 (not totally happy with that but it does the job)

OK by now the bass and drums are playing louder so I press my Level Shift which just lifts the volume enough to lift it over the top.
Except for the Level Shifter all the added dirt pedals are set at much lower gain than most players I've known.
This helps a lot as with 3 Drive pedals it's way to easy to end up sounding like Mud or buzzing fizz with to much gain on any of those pedals.  The Compressor is AFTER those 3 pedals and that keeps it all within a SET SPL of my overall volume,, without that it's a nightmare trying to keep them all within a certain SPL range.

If heavy metal is your taste then you might only need to add the pedal of your desire. 8|

Of course there are many ways to do similar things but this has worked well for me over the last ~10 ish years.

All that is running thru my crappy old Laney which I think I mentioned to you once before is not even a guitar amplifier,   :lmao:

To do all that in one amp chassis is a tall order. :-X :-X Once you realise that all that would need many relays and a pedal board with many switches.
AND you are still stuck with a friggin pedal on the floor,,,, Naah xP
As much as I hate pedal boards it's just a lot easier to use pedals.
And if you don't like one you just swap it out,,, you can't swap out things in a complicated amp chassis in a few minutes??  xP

I just read your other posting and it seems I promised you some of my circuits  :-[
I'll try and get some up soon,,, life is very busy at the mo but I WILL get something for you. :tu:

Phil.

edvard

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Re: What makes for a good clean channel?
« Reply #3 on: February 15, 2021, 04:36:41 PM »
Crystal clean clarity?  Foo, that would simply be a PA system, and we know that does not make a good guitar amp.   What you think of as clean in a guitar amp is not really very clean.  It just doesn't have the shrill raspy edges of dirt channels.

Agreed.  The problem is, that tube amps have an inherent non-linearity that everybody knows is the bees knees whether clean or dirty, while us SS guys are pretty much stuck with basically a PA powering a Celestion, and I want to do something about that without involving hot glass...  ::)  Hopefully without going down the tube emulation rabbit hole that many before me have plumbed to its depths already.

Quote
Go to DUncan amps and download the tone stack calculator and explore the tone stacks, you will see their response curves are not flat.  Putting all the tone controls at center on your old Fender is NOT the flattest setting.

Yep, done that, and looked up and tried at least 10 or 15 various tone controls trying to find the one that hits my ears just right.  Right now, the Brownface Bass/Treble control has my attention for the longest, so I'm sticking with that, but still researching an active Mid EQ to mitigate the -15dB mid scoop.  FWIW, it doesn't sound all that scoopy to me, so maybe I'll leave it.

Enzo

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Re: What makes for a good clean channel?
« Reply #4 on: February 15, 2021, 05:30:02 PM »
Oh, and look at the response curves of popular guitar speakers.

edvard

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Re: What makes for a good clean channel?
« Reply #5 on: February 15, 2021, 05:54:11 PM »
Hi Ed,,Try to keep in mind that there is no one section of a complete system that will reap magic,,
You build the sound/Tone you want out of what is mostly basic circuits most of which have been around for years.
If you want Clean then I take it you are talking about electric guitar?

In that case the clean will benefit from a little edge. (As Enzo just mentioned)
(My Cab sim, compressor, Phabbtone does that for me)

Regards OD and multi channels on amps,,, Been there done that and failed?
Pedals are far easier to get to where you want. It will depend on what styles you want to emulate.
For me it's just older rock and blues which is built from the little rattle of *Mictesters* Comp which is always on.
Then I add a home designed germanium clipper (that is my clean boost with a little more edge and OD) sweet. :tu:

For MORE heavy rock stuff (think ZZtop) I add a Boss OS2.
For all out scream I add a Boss SD1 (not totally happy with that but it does the job)

OK by now the bass and drums are playing louder so I press my Level Shift which just lifts the volume enough to lift it over the top.
Except for the Level Shifter all the added dirt pedals are set at much lower gain than most players I've known.
This helps a lot as with 3 Drive pedals it's way to easy to end up sounding like Mud or buzzing fizz with to much gain on any of those pedals.  The Compressor is AFTER those 3 pedals and that keeps it all within a SET SPL of my overall volume,, without that it's a nightmare trying to keep them all within a certain SPL range.

If heavy metal is your taste then you might only need to add the pedal of your desire. 8|

Of course there are many ways to do similar things but this has worked well for me over the last ~10 ish years.

All that is running thru my crappy old Laney which I think I mentioned to you once before is not even a guitar amplifier,   :lmao:

To do all that in one amp chassis is a tall order. :-X :-X Once you realise that all that would need many relays and a pedal board with many switches.
AND you are still stuck with a friggin pedal on the floor,,,, Naah xP
As much as I hate pedal boards it's just a lot easier to use pedals.
And if you don't like one you just swap it out,,, you can't swap out things in a complicated amp chassis in a few minutes??  xP

Let me clarify: I've tried a lot of dirt pedals and amps (too many to mention) that never left the music shop in my hands, the few that have I don't have any more, and I am not financially flush enough to do any further experimentation with that, and frankly, I'm not all that interested.  If I were to name my dream rig, it would be a Mesa Boogie Mark IIc+ or the Bedrock twin combo I tried out in 1992 or so, but didn't have the cash to swing at the time.  I still don't, so that's that, but the point is I'm a "set it and forget it" sort, which means once I find something that makes me happy, I'll likely be happy with it for a while.  Right now, I'm on a chase of a good clean tone that's not boring, but not over-complicated either.

What I DO have is a few buckets of spare parts, a little time, and a certain tone I'm chasing. I have designed a solid state dirt circuit that I'm about 99.9% happy with, and further tweaking is getting diminishing returns so I know I'm about done.  My ultimate plan is to make everything modular (separate boards with connectors between them), so If I get REALLY unhappy with a preamp or tone control, or if the power amp dies and I can't find a replacement, I can simply swap it out.  It might take a couple of days, but I'm not gigging, so I don't mind.

Quote
I just read your other posting and it seems I promised you some of my circuits  :-[
I'll try and get some up soon,,, life is very busy at the mo but I WILL get something for you. :tu:

Phil.

No problem, this endeavor has gone on for more years than I'd like to confess, so I'm OK.  ;)

So, the concensus so far is a bit of compression and judiciously chosen tone control to add some tone shaping and non-linearity to what would otherwise be no different from a monophonic Hi-Fi or PA.
Anything else?

edvard

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Re: What makes for a good clean channel?
« Reply #6 on: February 15, 2021, 07:02:29 PM »
Oh, and look at the response curves of popular guitar speakers.

Ya know, I was looking at speaker response charts, and they told me a lot less than what my ears could tell me.  I can look at the steepness of the low- and high-end rolloff and judge how bassy or trebly they might be, but beyond that they don't tell me anything about any give speaker's fundamental character that I can't pick up immediately with a brief listen.  I have a few ideas for what I'd like in a speaker, but that'll require more money than I have at the moment, and even then it'll probably be a Harley Benton twin cab.  Cheapest in their class and they are genuine V30s, you know...

Loudthud

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Re: What makes for a good clean channel?
« Reply #7 on: February 15, 2021, 07:55:47 PM »

Enzo

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Re: What makes for a good clean channel?
« Reply #8 on: February 15, 2021, 10:37:40 PM »
I brought up speaker curves, not so much for learning about individual speakers, but rather to demonstrate how "unflat" they ALL were, and how that is the major contributor to guitar amp tone.   For example it doesn't much matter what the amp does at 8k-10kHz when none of the speakers gets much over 5kHz.

joecool85

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Re: What makes for a good clean channel?
« Reply #9 on: February 16, 2021, 08:53:42 AM »
For me the short of it is yes, sparkly clean but with tone shaping.  Normally a -10db dip in mids, centered around 600hz.  After that it is up to preference if you drop lows or highs.
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phatt

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Re: What makes for a good clean channel?
« Reply #10 on: February 17, 2021, 01:00:58 AM »
For me the short of it is yes, sparkly clean but with tone shaping.  Normally a -10db dip in mids, centered around 600hz.  After that it is up to preference if you drop lows or highs.
Hi Joe, Your observation is correct but sadly it is only one piece of a much larger jigsaw puzzle.
If you insert that tone curve into a generic SS amp it won't sound like it's valve equivalent.

I'll try to ezzplain the why/what/how in general terms.

At nearly every stage in valve circuits there is a HPF created by the inter-stage decoupling caps ( this includes the power stages) and miller effect tends to roll off excess top end. If you are using Duncans Tone stack Cal it only shows that tone response as a separate entity which is nothing like what actually happens by the time that shape has been reshaped (or Mangled) by all the other sections of the WHOLE circuit that add or subtract from that curve.

Power stage in most SS power amps circuits is ALL DC (Direct coupled,, no caps) so a SS DC power stage = FLAT response,, while Valve power stage = big response curves adding even more hi pass as well as low pass.
The OT used in most guitar amps is also NOT 20/20 bandwidth Flat. Also as the power in an OT goes up the bandwidth tends to narrow,,Adding even more to that, most OT's can't pass really hi Freq so a lot of unwanted fizz is removed by design.
Sadly not so with SS DC power stages. :grr
A simple sim shows hi freq hash on the Primary side of OT but via the magical limitations of transformers the output side shows a nice square wave with smooth round edges waveform and the harder you push them the sweeter the sound. clever 8|

My guess is that SS passes all the crud,, You may remember that Mr Fahey uses output transformers with his big wattage SS Amps.
I have a SS 120Watt Factory PA here which runs a huge OT and the louder I run it, it never sounds harsh and my PhAbbtone is always bright. ;)

It pays dividends to limit your bandwidth for great guitar tone. Take away the excess crap that just gets in the way,, then UP the treble and it will bite without being brittle,,, That is TONE FOCUS Subtraction Not addition is the key. 


So even after you have spent weeks in front of Duncans tone stack Cal trying to find the magic it still sounds crap when you put it together. The tone control is only fine adjustment of the whole SYSTEM TONE. The system tone is defined by all the stages and how each part removes or adds to that basic shape.

Something not often noted;
PSU in SS is rigid.
PSU in Valves is NOT it moves up and down a lot.
In Valve supply just changing voltage nodes can dramatically change how the amp responds as the power rises. AFAIK that does not happen in SS amps.

Regards to speaker tone;
Unless you are in the situation where you have many different speakers in the same room at the same time it's likely beyound the ability of a novice to make any meaning full judgement of any difference.
I'm sure there are others here with vastly more knowledge that might be able to explain it better but this is what I've come to understand after ~40 years of messing with 100's of different bits of gear.
Phil.

phatt

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Re: What makes for a good clean channel?
« Reply #11 on: February 17, 2021, 01:49:49 AM »
Hi Ed,
As promised just some schematics of my gear.
This is my OD pedal which only adds a little sand/grit/edge to the tone which helps the Compressor deliver a little more triode type rattle. the components before U2B are just a bit of extra tone shaping. No reason you can't build this into an amp circuit but you need switching which then makes it much more complicated. :-X

I'll add more soon as I find them all ,, been through a few hard drives in the last few years so I have been trying to retrieve a whole lot of files.
As well as trying to make sure they are up to date cause I've altered a lot of my builds.
As you have plenty of Breadboards you can try some of these out and see if it suits. Again don't judge a circuit on it own use them to build you whole system tone/sound.
Phil.

Enzo

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Re: What makes for a good clean channel?
« Reply #12 on: February 17, 2021, 04:25:07 AM »
Duncan's calculator doesn't pretend to cover anything except the tone stack itself.  Not the whole amp or any other parts, just the stack itself.

phatt

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Re: What makes for a good clean channel?
« Reply #13 on: February 17, 2021, 06:30:48 AM »
Duncan's calculator doesn't pretend to cover anything except the tone stack itself.  Not the whole amp or any other parts, just the stack itself.
Yes I agree, that was my point. Sorry if I did not make that clear. :tu:
Having read many postings on forums and like I get the impression that quite a few punters get the impression those curves are what they actually hear.
Phil.


joecool85

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Re: What makes for a good clean channel?
« Reply #14 on: February 17, 2021, 11:17:29 AM »
For me the short of it is yes, sparkly clean but with tone shaping.  Normally a -10db dip in mids, centered around 600hz.  After that it is up to preference if you drop lows or highs.
Hi Joe, Your observation is correct but sadly it is only one piece of a much larger jigsaw puzzle.
If you insert that tone curve into a generic SS amp it won't sound like it's valve equivalent.

He asked for a clean channel, I figured he meant just preamp.  If that is the case, I stand by my argument.  Of course, taste/preference is relative.

I do agree about what you said though.  I've not tried using a transformer for speaker output, but I've thought about it because I constantly hear about it's magical properties.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com