EL84 vs 6v6

Dave_Mc

^ Yeah. Deferred.

 I always get mixed up between the class A/ class A/B thing (as you said, it's more to do with the "on all the time/not on all the time" thing than push-pull) and single-ended/push-pull. To be fair, it doesn't help that a lot of the marketing, and even supposedly-education articles you sometimes read, act like they're the same thing, when as you said you can have genuine class A operation in push-pull. (I meant to put that in my post but forgot ) )

BowynMadley

I prefer 6v6s. In fact I prefer most valves over el84s. I've had a genz Benz in the past and with a Strat it sounded great. With a les Paul (main guitar) it just farted and sounded terrible. I also have a blues junior that obviously runs el84s and I'm not getting on with that either and will be going in the near future. I really love big bottle tubes kt66s , kt88s ect but obviously if you want lower wattage you can't really use them. Saying that in cathode bias a kt66 is what around 14 watts @ICBM ?

ecc83

" Saying that in cathode bias a kt66 is what around 14 watts @ICBM ? "

The HT-20 is EL34s (could prob use a 66?) and uses a combination of cathode and adjustable bias to give just bang on 20 watts and really no more. The all FB rest of the HT range will deliver considerably more whallop than their "number" suggests.

Dave.

jpfamps

BowynMadley said:

I prefer 6v6s. In fact I prefer most valves over el84s. I've had a genz Benz in the past and with a Strat it sounded great. With a les Paul (main guitar) it just farted and sounded terrible. I also have a blues junior that obviously runs el84s and I'm not getting on with that either and will be going in the near future. I really love big bottle tubes kt66s , kt88s ect but obviously if you want lower wattage you can't really use them. Saying that in cathode bias a kt66 is what around 14 watts @ICBM ?

You can use KT66s etc to give lower wattage. 

You need to use lower HT voltage, and you will need to adjust the transformer loading for best performance.

We run 2 x KT66s at 350 VDC in fixed bias to get 25W.

Using cathode bias you'd probably get around 20W.

I think the reason more manufacturers don't do this is because from a marketing point of view 50W sounds more impressive than 20W, and you can sell a 50W amp for more money, even though it might not cost that much more to produce, so if the valves have a capability to produce 50W then it seem (economically) sensible to exploit this.

ICBM

jpfamps said:

I think the reason more manufacturers don't do this is because from a marketing point of view 50W sounds more impressive than 20W, and you can sell a 50W amp for more money, even though it might not cost that much more to produce, so if the valves have a capability to produce 50W then it seem (economically) sensible to exploit this.

Exactly. But I think it's long since past time when people should forget about the idea of cost and quality equating to power and volume and base the power requirement solely on tone. And realise that power and volume aren't the same thing either, which still seems to escape a lot of people, from the comments you still get about not "needing more than 10W" or whatever.

A 100W amp is certainly *capable* of far more volume than a 10W amp, but the reason most sensible people still want one is nothing to do with volume and all to do with clean headroom and/or a particular type of tone and response. So if you want to use bigger components that are also capable of more power but you choose not to because it gives you a particular type of sound you're after, that makes perfect sense to me.

57Deluxe

I like El34 because they actually offer the bridge between 6V6 and El 84 tonally

jpfamps

ICBM said:

jpfamps said:

I think the reason more manufacturers don't do this is because from a marketing point of view 50W sounds more impressive than 20W, and you can sell a 50W amp for more money, even though it might not cost that much more to produce, so if the valves have a capability to produce 50W then it seem (economically) sensible to exploit this.

Exactly. But I think it's long since past time when people should forget about the idea of cost and quality equating to power and volume and base the power requirement solely on tone. And realise that power and volume aren't the same thing either, which still seems to escape a lot of people, from the comments you still get about not "needing more than 10W" or whatever.

A 100W amp is certainly *capable* of far more volume than a 10W amp, but the reason most sensible people still want one is nothing to do with volume and all to do with clean headroom and/or a particular type of tone and response. So if you want to use bigger components that are also capable of more power but you choose not to because it gives you a particular type of sound you're after, that makes perfect sense to me.

I think that there is still a hang over from when amps weren't miced and needed to be loud enough to fill large halls.

Even when I started playing in the early 80s a "proper professional" amp was 100W, a 50W was "OK"  anything less than this was risible.

I suspect it's this thinking lead to the demise of many an AC30 for being "only" 30W.

EdGrip

I'd love to have a big-valves big-transformers amp. I just wish they weren't so physically big.

I have an irrational perception of EL84s as "low budget"/inferior and 6V6s as "better"/more proper. I don't know why, other than that you tended to find EL84s in budget amps in the 2000s, and also that Fender built all their smaller Hot Rod amps around EL84s rather than the 6V6s of their more expensive and prestigious vintage reissue brethren. All canny marketing, I've no doubt.
I love the sound of my Princeton. Not sure how much of that is 6V6 related. (Because of the knacky custom transformer in that amp, their plate voltages are ~360v rather than the ~440v of the original transformer. Hard to say what the difference in sound is as it was hardly an A/B scenario. ^_^ But it'll certainly be kinder to them over time.)

crunchman

There wasn't much in the way of 6V6 production 15 or 20 years ago.  That might be why Fender went with EL84s in their small amps.  SInce then you have had EH and JJ start production of 6V6s.

BowynMadley

@jpfamps I have a head running 2xkt66s in cathode bias and it produces 28 ish watts. Plate voltage is 350 I think but not certain. Depends on the valve and biasing I suppose

ecc83

Outside of guitar amps I was never a great fan of the EL84. Mind you, not much used the E version but you found UL84s in crappy Dansette record players where they did fail quite often (tho' IIRC the carbon 1W cathode resistors used to cook and go low but which failed first?) .

Can't recall a radio that used an EL84 but the earlier ones used 6V6 and were just about bombproof, lasted decades. A few radios used an octal EL32, not THE most reliable valve.

PA amps used KT66, EL34 (and old fairground stuff 807) never 84s. However there was a Philips rack PA amp used for headphone distribution in hospitals and they used EL81s, a 6volt version of a TV line output pentode. They ran at an elevated HT and gave I would guess 40-50watts a pair.

Speaking of "elevated HTs"! There was the EL31, top cap anode and Avon Cosmetics had an amp with a bloody big OPTraff in it and ran at about a kilovolt.

Dave.

jpfamps

BowynMadley said:

@jpfamps I have a head running 2xkt66s in cathode bias and it produces 28 ish watts. Plate voltage is 350 I think but not certain. Depends on the valve and biasing I suppose

If you have a choke filtered screen supply you will get around 28 Watts.

If you have a saggy power supply you'll get less power.

BowynMadley

Ha now you've lost me @jpfamps any reason why you dont see new production amps using kt style valves? I know they are a retro style design but they sound awesome

EdGrip

I would guess at limited supply of new valves.

ThePrettyDamned

jpfamps;566472" said:

BowynMadley said:

I prefer 6v6s. In fact I prefer most valves over el84s. I've had a genz Benz in the past and with a Strat it sounded great. With a les Paul (main guitar) it just farted and sounded terrible. I also have a blues junior that obviously runs el84s and I'm not getting on with that either and will be going in the near future. I really love big bottle tubes kt66s , kt88s ect but obviously if you want lower wattage you can't really use them. Saying that in cathode bias a kt66 is what around 14 watts @ICBM ?





You can use KT66s etc to give lower wattage. 

You need to use lower HT voltage, and you will need to adjust the transformer loading for best performance.

We run 2 x KT66s at 350 VDC in fixed bias to get 25W.

Using cathode bias you'd probably get around 20W.

I think the reason more manufacturers don't do this is because from a marketing point of view 50W sounds more impressive than 20W, and you can sell a 50W amp for more money, even though it might not cost that much more to produce, so if the valves have a capability to produce 50W then it seem (economically) sensible to exploit this.

Is this like the orange rocker 30, which uses a pair of el34s for 30 watts? That's a great sounding amp, both as a pedal platform and for the huge, thick crunch it has on channel two. It claims class A (which is presumably false) which people associate with small valves and ac30s/small fender combos but it sounds nothing like either.

The Laney l50H uses 5 el34s for 50 watts - and sounds absolutely glorious for it.

ICBM

ThePrettyDamned said:

Is this like the orange rocker 30, which uses a pair of el34s for 30 watts? That's a great sounding amp, both as a pedal platform and for the huge, thick crunch it has on channel two. It claims class A (which is presumably false) which people associate with small valves and ac30s/small fender combos but it sounds nothing like either. 

Yes, the Rocker 30 is a cathode-biased 2-EL34 amp. It *may* just about be Class A - I haven't scoped one to find out… it is theoretically possible. From memory the two valves are independently biased as well - ie there are two cathode resistors - although I've seen a schematic where the two appear to be linked, which would mean it's shared but they've doubled-up for power handling reasons. Unfortunately they almost never break down, so I haven't had a chance to investigate!

ThePrettyDamned said:

The Laney l50H uses 5 el34s for 50 watts - and sounds absolutely glorious for it.

This is truly Class A as far as I know - it's extremely unusual in that it's a parallel-single-ended amp, probably unique at this power level as Laney claim.

It's not *quite* true that single-ended means Class A - or not by the strictest definition anyway… it depends whether the bias point is chosen correctly to give a symetrical waveform, and most SE guitar amps aren't.

Whatever it is, it's a very unusual design and this is probably why it sounds quite different to most other amps, especially clean. Bear in mind that the *preamp* distortion is still completely standard though, the only real difference in the distortion due to the power stage will be if you crank it right up.