Clean 'headroom' on valve and transisitor amps?

[cockroach]

Just reading the Vox Cambridge thread, some one mentioned using different specified valves to be able to vary the pre-amp gain to give cleaner or dirtier headroom levels as desired.

I'm not really up with electronics or amp technology, so how do amp designers/manufacturers vary input gain levels with transistor amps? And can these gain levels be modified easily on a tranny amp, presumably as 'easily' as changing a valve or valves in a valve amp pre-amp section?

It's very ironic for me...back in the '60's, the exciting and desired high gain overdriven sound (Clapton, Beck etc) was damned near impossible to get, because most amps then were designed to give clean undistorted sound, unless really thrashed at maximum volume(which was not often practical)...but for the last 30-40 years, most amps seem to have been designed to easily give that type of overdriven sound, but it's now bloody hard to get a clean sounds with adequate live performance level, even using the so-called 'clean' channel' on modern amps.

My old first amp was a USA made Maestro 60 watt 2x12 combo- it was incredibly LOUD but crystal clear, and I've since found out it was designed as an accordian amp! But I couldn't get the overdriven sounds which have been so popular for years now.

However, nowadays, I prefer a cleaner sound, and using modern amps on the clean channel at live gig levels, even the supposed clean channel sound is still often distorted and fuzzy.

Please don't advise that I buy another amp- I can't afford to, and I am generally quite happy with my present amp! (Marshall MGX 50)

[Santoinetwo]

Oh yes I had the self same problem ! Making myself heard above the keyboard player, who was not only using his own amp. But also going through the mixer desk and front PA. Anyway, In the end I just got very powerful 200 watt Marshall Valve power amp ! So stacks of headroom there, plus with the Mesa Boogie Triaxis pre-amp I can obtain a good clean sound at very high volume without having to go through mixer desk and front PA. With some gigs an AC 30 can struggle to project clean volume, always near the edge of breakup. So microphone in front of your amp, then through PA is often only choice you will have.

[roger bayliss]

Most the 60's and 70's drive sounds came via say an AC30 or Fender amp that was clean and then overdriven at the front end with a suitable pedal. The likes of Clapton were using treble boosters back then as was Richie Blackmore, Rory Gallagher, Toni Iommi and Brian May et al. Then around late 70's interest shifted towards the Ibanez tube Screamers and the like and SRV sounds. I think clean amp and then overdrive / boost by a suitable pedal is the best way then its one click and you can change your tones. The treble boosters were often of the ' Dallas' type and sometimes the Horny Skewes variety such as used by Blackmore were employed. I'd say use a blues driver type for a little bit of dirt as the treble boosters really do have a lot of bite and treble in them !

HTH

[RayL]

The point that hasn't been mentioned so far is the distinction between 'gain' and 'volume'. The amps of the fifties, sixties and early seventies simply had a volume control on their input followed by one or two stages of gain and then the output stage. To overdrive the input stage (and get the desired distortion) meant that the amp had to be very loud.

Hence the appearance in the mid-sixties of the 'Tone Bender' and other pedals which pre-distorted the guitar signal so that the input volume control didn't have to be so high.

Then the manufacturers started adding a Master Volume control after the gain raising but before the output stage. This meant that the amp input could be overdriven (by keeping the input control high), but the amp didn't need to be so loud (because the Master Volume could be kept low).

Obviously, the distorted 'sounds' favoured by certain famous guitarists couldn't be reproduced simply by juggling input gain and output volume. Sometimes things like overdriving the output stage, or the way the power supply 'sags' under heavy load, or the way that the loudspeaker cones react when driven hard, are essential factors, which is why todays amps and pedals so often feature 50 or more 'simulations' of these factors to give 'Vox' or 'Marshall Plexi' or 'Mesa Boogie' at bedroom volume.

To get 'clean' sounds from your amp use the principle of keeping the 'Master Volume' at maximum and adjusting the input control.

Ray L

[cockroach]

Thanks chaps, but I was wondering about TRANSISTOR amp designers incorporating overdriven valve amp characteristics even on the 'clean' channel.

Just read my amp user manual again- and it actually says that when the clean channel volume control setting exceeds the halfway mark, the sound is modelled to resemble a valve amp gradually overdriving....well, that's that then!

I would have thought 'clean' means clean, but apparently not!

Perhaps I should have bought an old Roland Jazz Chorus amp- or something similar, which would stay clean at all levels...but there wasn't one in the pawnshop that day!

[RayL]

For a transistor amp where the clean channel stays clean, I can recommend my Fender FM212R (100w, two 12" speakers, built-in reverb, can be carried using one hand without discomfort). It has no Master Volume, and distortion (for those who need it) is provided on a second channel, selectable by a footswitch.

The nice thing about the FM212R (apart from the price, about £200 new at the time) is that Fender have recreated the clean, bright, sound of a Fender valve amp without the weight. There is plenty of gain on the clean channel. I usually use '3' for rehearsal. When The Triumphs played The Ace recently I increased this to '4' (The Ace is long and narrow) and for the Amersham Rock'n'Roll Club last Saturday I did actually use '6' (but the guitars weren't going through the PA system). Even Jim Nugent (who borrowed it for one number when The Secrets played the Dartford Shadows Club) commented on the power available!

Ray

[JimN]

I can recommend my Fender FM212R ... Even Jim Nugent (who borrowed it for one number when The Secrets played the Dartford Shadows Club) commented on the power available!
Ray

That's the black one with the black speaker cloth: http://www.guitariste.com/produit/photos/3752-d295c-big.jpg. It's a great amp - especially at that price.

The similarly-named, similarly-priced and ostensibly similarly-powered Fender Frontman 212 (but with more traditional Fender looks) isn't as good (even if it looks better):

http://www.guitariste.com/produit/photos/3778-49ac2-big.jpg

I have regular opportunities to play through one of these at local jam nights and rarely find a satisfactory sound from it.

Anyone who happened to want an unburstable amp which can stun at 100m (with pure clean tone) might care to follow my recommendation of another amp I have: the Peavey Renown combo, with two Black Widow speakers. I bought one new in February 1986 and it's still as great - and as lethal - as ever (ask RayL).

I note that there is one for sale on eBay: http://tinyurl.com/y3tz3ts. It is the 160w version (mine is 210w), but it'll still **** all over the Fender SS amp (sorry, Ray!)

Peaveys are so unfashionable that I bet it'll go for less than £100!

JN