Class "A" watts

Dan Tyack · Post by **Dan Tyack** » 11 Mar 2004 8:07 pm

David, on several tunes I used a prototype of the Univalve (one that I have been playing for almost a decade). On the majority of the songs, I used a prototype of a to be released THD amp nicknamed the 'Deco', which strangely enough is a 15 watt push pull amp with two EL84s (similar to the AC15 in the power amp section, but with a very different preamp). Apparently, this type of amp (AC30, Matchless) is AB, but when pushed close to the maximum power rating behaves more like a class A, hence the description of the AC30 as a class A amp. I don't know about the electronic theory aspect of it, but I do know that this particular amp sounds killer on about 9.

I personally prefer the BiValve on most sessions currently.

David L. Donald · Post by **David L. Donald** » 11 Mar 2004 10:38 pm

Dan thanks for the info.
I have heard a huge number of new and classic steel albums,
with a great variety of,... ooh, ooh naughty word coming, TONES.

You tone is one of my favorites.
And besides the hands, I am sure the amp is a good part of that.

Carl all good points from you, as usual.

There seems little consensus about up high frequencie or lower frequencies center points,
shelving or band type, etc.

It would seem a a 30w, true class A amp, with 15"speaker,
and a 800hz mid frequence w/ moderate Q bandwidth, would be a great preference for recording steel.

The purest path, the best choice of eq center points, enough power to move a full range speaker.

For added control semi-parametric mids EQ also.
For lows and highs I would say
200hz low with a half octave Q,
800hz mid but sweepable also, or with a variable Q control,
2.5 khz hi mid,sweepable with 1 octave q
and 3.5khz high band shelving with a soft slope.

A purist class A amp with the above would record to anyones specs like a dream.
And live stick it on a stand close to you and put a great mic on it and you would sound killer anywhere.

Ideal for me would be:
steel w/TT to amp tube stage (like SGBB)
with input and output level control and metering
patch out to Hilton and return
4 band fully parametric tube EQ
tube compressor stage with metering, threshold and ratio,
patch to effects loop,
Master output volume to
Class A output stage to
15" speaker of choice, as long as it is VERY efficiant.

And a Brauner Valvet, 8-10" away to mic it.

Any body drooling yet?
[This message was edited by David L. Donald on 11 March 2004 at 10:44 PM.]

Jussi Huhtakangas · Post by **Jussi Huhtakangas** » 12 Mar 2004 12:38 am

Steve ol' bubba, good to see you here!!! If I'm not totally mistaken, your amp is class AB and is rated around 80 watts. Only the first batch of 25L15's were "class A", based on Williamson specs. Your amp of course is probably louder than most other 80 watt tube amps, mainly because of the design and the super efficient output transformers Standel always used ( and still does ). Does yours have a JBL D130 in it also? That would be another thing, that adds the efficiency in it. But of course, you already knew all this, didn't ya!!

Dan Tyack · Post by **Dan Tyack** » 12 Mar 2004 10:00 am

Thanks for the kind words, David. The amp does have a real effect on the sound, as well as what I played.

I've got to say, though, that in terms of your ideal amp, sometimes more isn't better. That amp that I used on the majority of tunes on Blackened Toast had two controls, volumn and tone. The BiValve essentially has two: treble and bass (it does have a bright switch, but that stays off). IMHO, if the amp doesn't sound great without a fancy midrange eq, then adding the mid eq control can make it sound better, but I'd rather find an amp that sounds great without one. For one reason, every time you add complexity to a circuit, you change the basic sound. That's one of the reasons the UniValve and BiValve amps sound so good: they are really simple designs (e.g. no channel switching, very simple EQ). In terms of the speaker choice, I do love 15" speakers, but I have been using 2X12" cabs with a JBL and a Celestion for a while now, and I really love that sound. It's a lot bigger (more 3 dimentional and more low end) than a single 15", plus it sounds smoother with an overdriven amp. Plus, since I am using that ultra light Celestion speaker, it's about as light as a single 15" cab.

I agree about that being all you really need on stage. If I was in a band playing really loud in clubs with really lousy PAs, I might run the line out from the BiValve into another amp, but that isn't really necessary in most of the gigs I play.

Steve Merritt · Post by **Steve Merritt** » 12 Mar 2004 10:00 am

Hey Jussi,

Thanks for the info, that makes sense regarding the AB classification. It does have a JBL D-130F in it, which for my money is the best speaker around. It’s very efficient. I’m actually look at some other options for amps right now because as I stated earlier, the Standel is, at times, too powerful. It depends on the room and whom I’m playing with. So, I’m checking out some other option that are cheap(er) and still sound good. I’ll let you know how it turns out. I don’t have the money to buy a good sounding amp for every occasion…no money and no room to store them!!!!!

When are you coming to the states?

Jussi Huhtakangas · Post by **Jussi Huhtakangas** » 12 Mar 2004 10:33 am

Hate to be a thread-hijacker here, but Steve, we're coming for a short tour at the end of April, but no CA, "just" midwest ( your country's too darn big!! ). Hopefully you and Cari Lee will play the Greenbay fest next year, we would see ya there! Oh btw, tell her my kid still loves the Charlie Parker book she sent us!!

Bobby Lee · Post by **Bobby Lee** » 12 Mar 2004 12:47 pm

Some amps are swichable between class A and class AB output configurations. In those cases, "Class A Watts" could be a shorthand way of saying "watts in the class A configuration".

I've never heard a sound/tone advantage in class A. All of my favorite amplifiers have been class AB circuits.

I remember in electronics school class AB was described as the "push-pull" circuit. Everyone knows that push-pulls sound best (especially if they're black),

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<img align=right src="http://b0b.com/Hotb0b.gif" width="96 height="96">Bobby Lee - email: quasar@b0b.com - gigs - CDs, Open Hearts
Sierra Session 12 (E9), Williams 400X (Emaj9, D6), Sierra Olympic 12 (C6add9),
Sierra Laptop 8 (E6add9), Fender Stringmaster (E13, A6),
Roland Handsonic, Line 6 Variax

Larry Robbins · Post by **Larry Robbins** » 12 Mar 2004 3:02 pm

Thanks b0b, at last an answer even I can
understand!

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Sho-Bud ProII
"there's been an awful murder, down on music row!"

Dan Tyack · Post by **Dan Tyack** » 12 Mar 2004 4:40 pm

b0b, a lot of my favorite amps are ab as well (including a great old showman that I love to death). In general, with the amps I have with an class ab/a switch, I prefer the AB sound. In general, the class A amps I love really show their distinctive characteristics when being driven hard and put up wet.....

J D Sauser · Post by **J D Sauser** » 21 Mar 2004 4:12 am

I have no idea what I will talk about here, so please do not quote me if I say:

When I got re-interesed in tube amps I met an amp builder who builds custom order class A amps in Fort Lauderdale. His amps were single ended class A designs, as he said.
I asked him about the difference and the why's. He explained that;
only a single ended class A amp really would be operating in class A mode at all times.
only a class A operation would reproduce all sweet harmonies because a push-pull (class AB) would/(could?) cancel out some (even order?)-harmonics because of the cycling effect inherrent in a push-pull (described as ON/OFF) opperation.
(and now fasten your seatbelts!): a single ended class A amp would be louder Watt for Watt, which I understood as A-Watts being louder as AB or worse SS Watts. Now with Carl's explaination this can be read differently.

I currently own and play trou two single ended class A amps, both Rickenbacher attache cases out of the 1930's. The have very low rate outputs (W) and take up a lot of electrical power and will keep a bed room nicely warm and cozy during winter time, but they kick ass.
I have a Fender Twin (original BF), it's rated what, 80W output? So is my ShoBud Christmas Tree (SS) but the Twin seem 50% louder... but incredibely, without distorting the ShoBud is sweeter for pedal steel.

... J-D.

David L. Donald · Post by **David L. Donald** » 21 Mar 2004 8:10 am

Another way to add more class A power is to add another speaker and output stage to it. Driven from the same preamp.

2, 3 or even 4 class A output stages and a 10" speaker for each would push a a lot of air.

You could switch in another speaker/output stage as needed for bigger gigs.

$$ I hear the register ding here, but it would cover all bases sound wise.

Dan T, those other proccessing stages I mentioned in an earlier post would all be switchable in or out of circuit.
[This message was edited by David L. Donald on 21 March 2004 at 08:14 AM.]