Pre-amp versus power amp distortion?

CitiZenNoir

Sorry about that. Here is the correct link for the Neil Young video.

http://www.youtube.com/watch?v=1O6VxlMi69Q

I love all the noises Neil's amp makes. :twisted:

Here's another great video of Neil playing Cinnamon Girl

http://www.youtube.com/watch?v=fBS3B2cZcFM

You know, videos and recordings do not really show how great a cranked tube amp sounds. You have to be there to appreciate it. You can see the crowd is going wild. :D

Angus and Malcolm Young of AC/DC do not use pedals to get overdrive or distortion. Just guitar straight into a Marshall amp cranked up about half. Awesome overdrive crunch.

http://www.youtube.com/watch?v=tauEh_DFDPM

Get used to this kind of distortion and you will throw your pedals away. :wink:

Thankx alot for the links Wes.
I'm going to check them out now.

I hear that Bro.... I never used any pedals, and still don't!!!!
It's all between the amp, guitar, and my fingers.
That's real tone!!!! :D 8) :wink:

Do you like James Gang and Free????
Marshall/Orange w/Les Pauls & HBs

Ken

Ken

I have always been a huge fan of Paul Kossoff and Free. Paul had the best vibrato ever IMHO. When I listen to Angus Young, I can hear a lot of influence from Koss, especially the great vibrato.

Yeah, nothing beats the old Marshall and Orange tones.

And I have always been a big fan of Joe Walsh too. I wasn't really a fan of the Eagles until Joe joined. :wink:

Here's one of Joe's hits.

http://www.youtube.com/watch?v=24SOBX4PIx8

Have you seen the new Orange Tiny Terror 15w amp? This looks very interesting, would be perfect for gigs, you could crank it up a bit.

http://www.nitro-tone.com/index.asp?PageAction=VIEWPROD&ProdID=2539

Not too bad a price too. This has been on my wishlist for awhile, I may pick one up in the next few months.

Thankx again for the Neil!!!! :D
He's a nut!!!!
Jumpin' around like that - awsome

I love N.Y.!
I've seen him in concert 3 times - twice with Crazy Horse and once acoustic.
He is a huge influence on me.
When I started playing, most of my 'songs' consisted of very simplified strum versions of Neil Young songs.

He's got the ONE Fender tweed Deluxe amp.
He uses just that one.
I heard he has over a hundred tweed Deluxes - none sound like THE ONE.

And Old Black is actually an old 50's Goldtop that somebody painted black. ( I can't believe the finish has held up so well )
He has a P90 in the neck, and I believe a mini-Humbucker from an old Firebird in the bridge.
COOL. 8)

Yeah Koss was sure somethin'.
That's a shame about him. :(

I have ALWAYS wanted an Orange.
Yeah, I've seen that Tiny Terror. I really like low watt tube amps - I was really happy to see that.
If you get one let me know how it is, as we seem to be Tone Siblings :D

Ken

I've heard that true class A tube amps (even w/tube rectifiers) do not have any sag.
Sag is suppose to happen in class A/B amps only.
That sure doesn't explain the ultra sag that 50's Gibson class A tube amps are famous for.

Any thoughts on that out there????
"Sag" is mainly "preamp" distortion from voltage supply drop occurring as the power amp demands more current from the rectifier and the rectifier's internal resistance drops the voltage. By definition any amp operating under Class A conditions can't produce sag, because the average plate current is constant regardless of the amp's output in a Class A amp. The fly in that ointment is that though an amp may be designed as a Class A amp and intended by its designer to be run that way, it may have been built to be capable of being overdriven out of Class A operating conditions, and its user may like to use it that way quite a lot. And quite a few warmly-biased Class AB1 amps have been sold as Class A; it really depends on how strong a driving signal they're being rated with as to which class they fall into. Keep the volume moderate and they're Class A. Crank 'em and they're Class AB.

First, Wes, thanks for the clips and the explanation. So, pretty much all classic rock, blues rock, etc. distorition is going to be power amp based? That means that because a master volume only lets you get pre-amp distorition at a reasonable volume you won't be able to get those sounds. You'll need an attenuator to get them, right?
I've heard that true class A tube amps (even w/tube rectifiers) do not have any sag.
Sag is suppose to happen in class A/B amps only.
That sure doesn't explain the ultra sag that 50's Gibson class A tube amps are famous for.
Any thoughts on that out there????

From the book that I'm reading on tube amps the claim is that there are very few "real" class A amps. The only ones that the book says exist are the single output tube amps (which must be class A - class AB requires multiples of 2 tubes) and the Gibson GA-8 and one of the boutique THD amps. Everything else is class AB. The book said that most amps that manufacturers who claim class A have is an amp with cathode biased power tubes which apparently gives most of the feel of class A amps.
The fly in that ointment is that though an amp may be designed as a Class A amp and intended by its designer to be run that way, it may have been built to be capable of being overdriven out of Class A operating conditions, and its user may like to use it that way quite a lot. And quite a few warmly-biased Class AB1 amps have been sold as Class A; it really depends on how strong a driving signal they're being rated with as to which class they fall into. Keep the volume moderate and they're Class A. Crank 'em and they're Class AB.

I was under the impression that you couldn't drive a class A operating amp into a class AB. Class AB requires two tubes working together whereby each tube amplifies half of the signal.

You most certainly can drive a single ended Class A amp out of Class A operating conditions. Might not be officially called a Class AB amp when doing so. It's just called "unacceptable distortion" in the textbooks. We call it "rock and roll." :lol:

So, am I getting this right....
The old 50's 5 to 12 watt amps that operate with only one power tube, one pre-amp tube,
and one rectifier are real class A amps - and that's pretty much it....?
You need two power tubes to be a class A/B????

And of those types of amps (class A/B) like old diamond covered Ampeg amps from the 60's,
Those seem to run pretty clean an loud most of the time.
They seem hard to push into overdrive....?

Ken

Well, you can have paired tubes and be in Class A. Class A can be run in push-pull. That used to be very popular, and was up to the end of the tube era. Class AB has to be run with push-pull paired tubes for undistorted output, which is what the books are talking about. It's also possible for paired or multiple tubes to be run in parallel as a single ended Class A amp, though that's not commonly done.

But yeah, you're right, the real Class A guitar amps are pretty much just the low powered single output tube ones. When you run them into output stage clipping they're not really in Class A any more, but they're designed as Class A amps and you don't quit calling them that, any more than you do the Class AB amps when grid current overbiases them so they're actually operating in Class C conditions.
:D

Class C amps - oh boy :shock:

Speaking of muti-tubes in parallel....
I know someone who has a Fender Twin Reverb.
He's not going to get an attenuator. (you'd have to know him)
He thinks the amp is a bit harsh.
I'm pretty sure that's because it's an 85 watt tube amp, and he can't come anywhere close to pushing it to overdrive.
Since the tube are running in parallel on that amp, I suggested pulling 2 out;
either the odd 2 or the even 2.
That should keep it going and cut the wattage in half, making it a more manageable amp.
(for the sound that he want's)
He said he asked someone about that and was told that it would fry the transformer.

What are your thoughts on that Ric. ????
(Or anyone who has anything to add)

Ken

When you pull two out and cut the wattage in half, the sound level difference is barely noticeable, as it amounts to 2dB. Ideally the output impedance should be readjusted when you do this. If I'm recalling correctly, you should plug your 8 ohm cab into the 4 ohm jack when you pull half the tubes out. Maybe the coffee hasn't kicked in and I've got that backward. Anyway, if you really want to cut down the volume of a cranked amp, you need an attenuator.

Anyway, if you really want to cut down the volume of a cranked amp, you need an attenuator.

Or ear plugs :?

Yeah, that works!

Personally, I use the volume knob. Simple, cheap and effective.

First, Wes, thanks for the clips and the explanation. So, pretty much all classic rock, blues rock, etc. distorition is going to be power amp based? That means that because a master volume only lets you get pre-amp distorition at a reasonable volume you won't be able to get those sounds. You'll need an attenuator to get them, right?

An attenuator gets you close to true power amp saturation, but not 100%. Part of the tone comes from overdriving the speaker, so you have to get the volume up to do that. And most attenuators tend to roll off the high frequencies a bit, so you are still not quite getting the true overdriven amp tone.

The best thing to do is use a lower powered tube amp that you can crank up full (or near full). I have used my Epi Valve Jr 5 watt at a gig and you can really crank it up in that type of situation. It will get over a fairly loud drummer. A 15 watt amp would probably be ideal for cranking up at a small gig.

Neil Young is only using a 40 watt amp. But he is on a large stage with a large crowd. So he can really crank the amp. But I am sure his amp is mic'd into the PA system. A 40 watt amp is super-loud, but not loud enough to play an arena alone.

When you hear these great tones on recordings, many times a very low powered tube amp was used and the amp put in an isolation box or booth.

So, there are alternate ways to get these great tones, but the best method is use a low powered tube amp you can crank. Then you will hear tones that blow you away. :twisted:

Wes -
I agree with the whole 5-12 watt tube thing.
That's where the best sound is.

To be honest; with the new technology of bands having PA systems and mixing boards and all that at live gigs now,
there really is no need to have anything more than a small tube amp.
You would be able to use it for gigs, recording, and practice.
And it would be easy to drag around where ever you go.

I think that Clapton started that 5 watt tube amp in the studio for great sound when he did the Layla album with
Brownie (a stock 56 strat) thru a 50's 5 watt Fender Tweed Champ amp.
Huge sound he had on that album.

ZZ-Top would also find the answer to Billy Gibons wanting a fuller studio sound in small low watt tube amps.
I think that's pretty much the norm these days.

And they have tremendous speaker break-up.

That though is a matter of taste.
I think it was pointed out earlier that some that are looking for a crunchier sound will say, load their 50 watt Marshall
with 2 20 watt Celestion Greenbacks.
While others who want nice warm tube overdrive with plenty of headroom will load say, 100 watt speakers into theirs.
And of course there's the matter of foam or no foam - and when buying a vintage 50's amp; the original CONE in the original speaker.

I do have to disagree with you on the amp that Neil Young uses though.
The new Fender Deluxe amps (Hot Rod/Blues) are 40 watt amps.
The original 50's narrow panel tweed Deluxe amps were 12 watt amps with nothing more than a volume and a tone control.
That's what Neil uses.

Ken