If zobels and conj. filters aren't a bandaid.......

[daz]

....then why is it 99% of guitar amps don't use them? I've built 2 amps now and using a CF on the output (across the plates) tames a excessive high end that happens more as you turn up. I've always felt thats a flaw in the amp because if it weren't then why is it i have tried everything imaginable and even stumped hoards of internet gurus who've looked at my schematics?

what i'm trying to say is that many have told me that CF's and zobels are not a bandaid. But if thats the case why is it only a handfull of amps out of thousands use them? I would have absolutely no reason to use one if my amp's frequency response wasn't so out of balance as i turn it up. 99% of amps don't have them because they don't need them. So how can anyone NOT admit they are a bandaid for another problem?

[mooreamps]

....then why is it 99% of guitar amps don't use them? I've built 2 amps now and using a CF on the output (across the plates) tames a excessive high end that happens more as you turn up. I've always felt thats a flaw in the amp because if it weren't then why is it i have tried everything imaginable and even stumped hoards of internet gurus who've looked at my schematics?

what i'm trying to say is that many have told me that CF's and zobels are not a bandaid. But if thats the case why is it only a handfull of amps out of thousands use them? I would have absolutely no reason to use one if my amp's frequency response wasn't so out of balance as i turn it up. 99% of amps don't have them because they don't need them. So how can anyone NOT admit they are a bandaid for another problem?

The reason is probably a very simple one. It takes a lot a hard work and expensive parts to build an amplifier. Also, since guitar amps is such a competive market, most commercial designs are based on only just enough parts to make an amplifier work, and that's it.

Other features that will enhance the tone and/or reliablity of the unit, in most cases, is just not cost effective enough to market. Even in my own equipment, as I try to address some of these concerns, the component part count and the increased labor involved can easliy get out of hand, if you're not careful.

-g

[Alex/Tubewonder]

Another reason you don't see Zobel network in too many amps is that probably very few of todays self appointed "gurus" really understand what its inherent function is.
Simple RC across OT primary or secondary is just the simplest version.
Google is your friend: "Zobel network", 2nd on the list.....but whether it will make the amp sound better is a matter of taste.

[Shea]

I don't know much about them myself, so maybe this is a dumb comment, but perhaps the reason why they aren't more common is that guitar players are used to what guitar amps do without them. Despite all the differences between guitar amps, two things that nearly all tube guitar amps have in common is (1) they're usually connected to speakers that have a spikey impedance curve, and (2) they don't have a conjunctive filter or zoebel network. So the tone of all these amps is shaped by the speakers in a roughly consistent manner -- which I guess would equate to peaky bass and treble response, or a midrange cut -- and to a guitar player's ears, that's an essential part of what a guitar amp ought to sound like. Guitar players are also used to the fact that you can radically change an amp's tone just by swapping the speaker out for a different model. If I understand correctly, that would be less true if you put a conjunctive filter or zoebel network an amp. Try to sell a guitar player an amp that doesn't make a greenback sound like a greenback, and he'll probably think there's something wrong with the amp.

So, maybe it's not just ignorance or cost-cutting on the part of amp builders, and instead it's another example that guitar players are a fairly conservative bunch.

Shea

[daz]

perhaps the reason why they aren't more common is that guitar players are used to what guitar amps do without them

But the thing is, no matter what guitar players have come to be used to, there are some things that no matter what came before would never catch on. Nasty harsh treble/hi-mids is one of them. It's also something that seems to NOT be inherent in guitar amps most of the time, at least not to the extent that they need something like this to tame it because no amount of tweaking gets rid of it. I understand exactly what you are saying, but it doesn't apply in this case. I've often thought about how much (a LOT) of the original sounds from the beginning of the electric guitar era are still what many are after today, not just because they were good but because we grew up with them and come to hear them as a normal guitar sound. But this isn't something that would have fit into that category even if the original fenders and marshalls sounded like that. They would have been "fixed" and todays players would be looking for that fixed sound. This is not just a taste variation, it's flawed tone. And a zobel or CF just isn't necessary or even desirable if that isn't happening because how many people do you know that want dull tone? And thats what a zobel or CF will do to an amp without this problem.

[Shea]

If you're saying that nasty treble and upper midrandge is an inherently flawed tone, and that it's a very common problem with guitar amps, and therefore Zobel networks ought to be more common, then my response is that the average guitarist does not dislike treble & upper mid harshness the way you do. In fact, a lot of them really like it. If guitarists universally hated harsh treble and upper mids, then we wouldn't have even heard of Marshall amps or Vintage 30 speakers. But Marshalls aren't going away -- in fact, they seem to be having a bit of a resurgence after Mesa gave them a good trouncing. And today's Marshalls sound as crackley as ever. Also, You'll find professional players all over the internet who swear by Vintage 30s and SM57 mics, which, IME, is just a recipe for tone that sounds like tearing paper.

A big factor here is hearing loss. Guys who spend years of their life chasing that perfect tube-amp crunch blast the hell out of their ears - I know I have. That causes midrange hearing loss, so over time they favor more and more upper mids to compensate for it. I've read reports of the current Van Halen tour saying that Ed's hearing must be completely gone because his tone is so harsh. And when a guy is rehearsing or playing a gig with a loud amp, especially a Marshall, then after 15 or 20 minutes his ears will be fatigued, he'll wonder why everything is so mushy sounding all of a sudden, and he may be tempted to go over to the amp and goose the treble and presence. That's happened to me too. I try to be aware of this trap and not fall into it, but sometimes I do. Be proud that you don't.

So, if I correcly understood what you meant, I think the reality is that this actually IS a subjective tonal choice, and that harsh treble and upper mids are more popular with guitarists than you think. Maybe not so popular with the people in the audience, but they aren't the ones buying the amps.

But if what you meant is that most amps don't have a flaw that would be fixed by a zoebel network, then that answers your question why zoebel neworks aren't used.

Shea

[daz]

then my response is that the average guitarist does not dislike treble & upper mid harshness the way you do.

Well, to be blunt i find that wrong because i have owned and played a lot of amps in my almost 40 years of playing. A LOT. And i have never ever heard one that has a sound that i'm talking about. Literally not one. (well, with the possible exception of a few 70's SS amps that were commonly acknowledged as garbage)

So if this is something a lot of players like, why havbe i never heard an amp like this? I think you are underestimating the tone i'm talking about. I'm talking no more than 10:00 on the treble knob or it's a thinner treblier tone than i ever hear any players using with rare exception. And this is where a zobel or CF is needed unless you have a player who's idea of good tone is a huge departure from the norm. And i know a ton of players. Trust me on that because i work in the industry. And why is it they too have tastes that are all varied but well within the limits of treble like i'm talking about?

See, this is what i'm trying to tell you here.....i've heard a trillion records, a 1000 truckloads of players and heard the tone they like, played endless gear, and of all of that i never hear the kind of tone that would require a zobel to my ears.

[Rob Mercure]

With absolutely no comment on any clashing views: "historically" something that's an "add on," i.e., "stuck at the end of the signal chain" has been considered a "quick fix" measure for what's been viewed as an engineering problem. But this assumes, for all practical purposes, that the goal is a HiFi amp or as close to HiFi as possible. All of the circuit examples in tube manuals, and RDH4 and such assume that one wants to "reproduce" music as "accurately" as possible - but what we're about friends is music "production" so many of the more or less "definitions" historically used don't apply.

Does this make sense to you all? I hope so cuz it's a little hard to define (and if my " key broke I'd "S... out of luck").

So no one is "band aiding a HiFi amp" but instead "tailoring the response of a guitar amp."

Rob

[Shea]

Well, to be blunt i find that wrong because i have owned and played a lot of amps in my almost 40 years of playing. A LOT. And i have never ever heard one that has a sound that i'm talking about. Literally not one.
...

So if this is something a lot of players like, why havbe i never heard an amp like this? ...
See, this is what i'm trying to tell you here.....i've heard a trillion records, a 1000 truckloads of players and heard the tone they like, played endless gear, and of all of that i never hear the kind of tone that would require a zobel to my ears.

Then most of my last post was based on a misunderstanding of what you were saying. So skip right down to my last sentence: "But if what you meant is that most amps don't have a flaw that would be fixed by a zoebel network, then that answers your question why zoebel neworks aren't used."

Looking at your first post again, I think I misunderstood the whole tenor of this thread. I thought you had decided that conjunctive filters were awesome and couldn't understand why more amps don't have them. After reading it again, it looks more like you're stumped as to why these particular amps that you built need conjunctive filters to sound good when most amps don't. Sorry, I can't help you there. I've built amps that have had problems that completely mystified me too.

Shea

[daz]

Ahh, i see. Yeah, i'm not at all thrilled with them. They help, but they don't do all good things to the tone. Kinda like trying to fix a overly bright amp with the guitar's tone control. It kinda works, but not really. not the kind of thing you want when you build your own amp because we obviously do that in the first place to acquire better tone than we can get from production amps.

[mooreamps]

Another reason you don't see Zobel network in too many amps is that probably very few of todays self appointed "gurus" really understand what its inherent function is.
.

It's "inherent" function is to null the self-resonant spike of the loud speaker. If you look at a loud speaker responce curve, they tend to self resonate at frequencies anywhere from 80 hz through 130 hz. Two points to consider.
1. You would have to "tune" the Zobel for the type of loud speaker you're using.
2. Even at 130 hz, that frequency is just a little bit out of band for a guitar amp.

-g

[Chuck H]

You mentioned that you have built a couple of amps that use a CF to tame the "harshness". Is your question then:

"Why do I have to use these things to make my builds sound right when most amps don't need them?"

And / or:

"If we build "better" amps to be ahead of the tone game, then why do we often need to use a CF to correct the tone of our builds when "common" amps don't usually need them?"

I was confused by your intent on the first post, and it seems a little like others were too. I'm trying to help clarify the situation so we can all try to answer the right Q.

Chuck

[Shea]

Ahh, i see. Yeah, i'm not at all thrilled with them. They help, but they don't do all good things to the tone. Kinda like trying to fix a overly bright amp with the guitar's tone control. It kinda works, but not really. not the kind of thing you want when you build your own amp because we obviously do that in the first place to acquire better tone than we can get from production amps.

It sounds like you've probably tried everything and asked for all kinds of advice before you resorted to the conjunctive filter. But, just taking a stab in the dark, did you ever try using a lower primary impedance in the output transformer? That would generally require replacing the output transformer with a different one, but a quick way to find out whether that might help is to hook up a speaker load of half the impedance the amp is set for -- i.e., set it to 16 and plug in an 8 ohm load, or set it to 8 and plug in a 4-ohm load. Of course, you'd have to disconnect the conjunctive filter first, so you can tell whether the change in impedance improves the tone at all.

Shea

[daz]

It sounds like you've probably tried everything and asked for all kinds of advice before you resorted to the conjunctive filter. But, just taking a stab in the dark, did you ever try using a lower primary impedance in the output transformer? That would generally require replacing the output transformer with a different one, but a quick way to find out whether that might help is to hook up a speaker load of half the impedance the amp is set for -- i.e., set it to 16 and plug in an 8 ohm load, or set it to 8 and plug in a 4-ohm load. Of course, you'd have to disconnect the conjunctive filter first, so you can tell whether the change in impedance improves the tone at all.

Shea

No, i never tried that. But i just did now that you mentioned it. (set it to 4 ohms with my 8 ohm speaker) No difference i can tell, or at least nothing worth noting. I was curious about this tho because the OT wasn't purchased with EL34's in mind, but it's in the ballpark...4k primary/50 watt .

Chuck....yeah, i think we covered that in the posts preceding yours. I guess i should have been clearer, but what i meant was i had TRIED them in the 2 amps, but i only tried them then removed them because i didn't like thier effect . They do calm the harshness, but they also make the amp sound rather dull.

[Shea]

No, i never tried that. But i just did now that you mentioned it. (set it to 4 ohms with my 8 ohm speaker)

No, I meant the other way. Set the amp's impedance switch to 16 ohms and plug in your 8-ohm speaker.

Also, see if the screen voltage is higher or lower than the plate voltage. I've gotten ugly, blatty distortion when the screen voltage was higher than the plate voltage. The fix for that is larger screen resistors.

Shea