When is an amp 'All Valve'

[tomjackson]

I'm currenlt trying to work out the basics of how amps work and what the differnt configerations of valves are.

So I'm wandering when an amp is truly all valve, obviously we still class amps with solid state rectifiers as all valve but I can't work out the following.

The Rivera Clubster is marketed as 'All Valve'.  It has 2 channels and 2 6V6 power valves so I'm wandering how that could be all valve, considering it has reverb and only 2 12ax7's.  If one of these is a phase inverter (presuming it is not paralell single-ended) then surely the other 12AX7 could not function as input, driver and overdrive stages so either the amp has:-

A - Solid State overdrive
B - Solid state phase invertor (is this possible?)
C - Whichever surely the reverb is solid state?


My Laney VC30 has 3 12AX7's so I can work that out but it seems many amps nowadays employ a mixture of SS and Valve technology but still claim to be 'All Valve'.

Amp experts, care to shed any light???


Disclaimer:- I have nothing against Solid State amps or stages, Musicman made great amps with SS preamps and BB King uses Solid State amps, I'm just pondering how some amps work.....

[Twaddlefish]

I assume it means that the both the pre- and power amp are both fully valved, rather than being transistors. The Valvestate Marshall IIRC has a valve pre-amp with one EC338 (or whatever it is) in it.

[WezV]

gotta love the dynamics of a small amp with a valve rectifier

[Twinfan]

In the Rivera you mention I believe the reverb is solid state driven, not valve, plus it has a solid-state boost.  The main signal path is then valve like a non-reverb Fender Deluxe:

Input gain stage (half a valve) -> Phase inverter (both halves) -> Power valves

Channel 2 will use the spare triode from the input gain stage and some EQ bypass.

Calling it "All Valve" is pushing it somewhat....

[tomjackson]

gotta love the dynamics of a small amp with a valve rectifier

Definitely, but I've heard below a certain wattage it makes no difference as, say 5W is not powerfull enough to produce any sag?

If it sounds good it doesn't really matter I suppose...

[tomjackson]

In the Rivera you mention I believe the reverb is solid state driven, not valve, plus it has a solid-state boost.  The main signal path is then valve like a non-reverb Fender Deluxe:

Input gain stage (half a valve) -> Phase inverter (both halves) -> Power valves

Channel 2 will use the spare triode from the input gain stage and some EQ bypass.

Calling it "All Valve" is pushing it somewhat....

I suppose there should be a new catogory between all valve and Hybrid called 'mainly valve'  :D

[Twinfan]

Exactly!!!

Plus you're right about the 'sag' thing, plus it doesn't just come fromt he valve rectifier.  It can come from the circuit design too.  Ask MartinW if you want a more technical explanation, but we've had solid state rectifiers in JTM45s and they still sag.....

[martinw]

I'd be happy to call an amp with an SS rectifer, plus an opamp driven reverb or FX loop, "all-valve".

As long as all the amplification, tone-shaping and power stages are valve, that's what matters. The signal is not being processed by a solid state device where it matters. Reverb purists would want a valve driven reverb too.

However, there's quite a few amps with opamp driven overdrive channel or boost. The Koch Studiotone is one, and the H&K Statesman another I know of. Those amps are not all-valve when you engage the 2nd channel or boost. You often read in reviews of these amps that the high-gain channel doesn't sound as good as the clean channel!

Sag: overrated, and little understood. Not always desirable anyway. Having a valve rectifier doesn't guarantee sag; operating class, level of bias and power supply "stiffness" also contribute to it.
Many of the best sounding amps you can name will have had SS rectifers, with no-one complaining that they "didn't have enough sag."

[dave_mc]

I'd be happy to call an amp with an SS rectifer, plus an opamp driven reverb or FX loop, "all-valve".

As long as all the amplification, tone-shaping and power stages are valve, that's what matters. The signal is not being processed by a solid state device where it matters. Reverb purists would want a valve driven reverb too.

However, there's quite a few amps with opamp driven overdrive channel or boost. The Koch Studiotone is one, and the H&K Statesman another I know of. Those amps are not all-valve when you engage the 2nd channel or boost. You often read in reviews of these amps that the high-gain channel doesn't sound as good as the clean channel!

agreed. ss-driven reverb or fx loop isn't a dealbreaker (as long as you can switch them out, if you really care)... not too keen on op-amp parts in the signal path though. not that there's a problem (plenty of people use boost pedals with valve amps), just the principle of the thing (if it's not "all-valve", don't call it so!). plus if i'm going to use opamps in pedals, i like to be able to choose which pedals i use, for transparency, quality of tone, etc. etc.

[tomjackson]

Thanks Martin, nicely explained.

I suppose then that in a way a solid state boost is not that different from putting a solid state pedal in front of an all valve amp, only that it's earlier in the chain which changes them way it reacts with the valves.

Is cost reduction the main consideration for the inclusion of opamps then?

The Rivera, H&K and Koch are all relatively expensive amps so I wonder why an extra valve stage was not just employed?

[dave_mc]

gip, most likely :lol:

[martinw]

I suppose then that in a way a solid state boost is not that different from putting a solid state pedal in front of an all valve amp, only that it's earlier in the chain which changes them way it reacts with the valves.

Is cost reduction the main consideration for the inclusion of opamps then?

The Rivera, H&K and Koch are all relatively expensive amps so I wonder why an extra valve stage was not just employed?

Yes, the position of the SS bits makes a difference, or can do, as each valve stage should be configured differently, and will react differently to the boost.

Cost is one reason, but also some harder-edged opamp (or even diode) derived SS clipping can be better for high gain stuff. It's also easier to layout, and easier to control oscillation problems, and more repeatable from amp to amp. If not done right, it can suck the life out of the tone though.

[Roobubba]

I have no idea what 'sag' is, but it doesn't sound like a word that I would want attributable to any form of amplification...

Roo

[WezV]

no roo, it wouldnt be for you!!

here is a defination:

Sag refers to the drooping of the power supply voltage in response to large transient signals, which lends a certain dynamic "feel" to the tube amplifier that is not generally found in solid-state amplifiers.

  This lowering of the supply voltage lowers the output power slightly in opposition to the larger input signal, making it act like a compressor.  The lowered supply voltage also tends to decrease the available headroom, increasing clipping and changing the operating point of the tube dynamically.

many ways to get the same effect and as martin says it isnt always desirable anyway.

[Twinfan]

For Metal?  sag = bad = loss of tightness in tone, sludge

For Blues?  sag = good = spongy response to notes, warm and expressive response

As a very general rule......