number of tubes

[jjl5590]

hey guys,

just curious about why some amps, like genz benz shuttle only have one tube in them, but others like the GK MB Fusion have three? Why do some amps have more than one? does it make them louder?


cheers

[BassmanPaul]

No it makes them more tubey!

Paul

[BassmanPaul]

You're also not allowed to post items for sale unless you are a supporting member.

Paul

[RickenBoogie]

Tubes in the preamp are nothing more than "tone machines". Volume comes from the poweramp, and equally, the speakers.

[jjl5590]

so as BassmanPaul said, the more tubes in the preamp, the more tubey the sound is

[johnk_10]

some amps use a tube only in the first gain stage and then solid state amps for the subsequent eq and driver stages, while others use tubes for the front end and the eq stages.

[agedhorse]

The "number of tubes" is a marketing concept, "how the tubes are used" is an engineering concept.

A tube is just a tool that, depending on how it's used, can make an amp sound "tubey" or "solid state like" depending entirely on how it's used and what circuit it is used in. The circuit used is just as important as the tube itself.

I can take 3 tubes and design a preamp that would be hard to distinguish from a solid state amp if I was to use a solid state design technique approach. I could also design a preamp that was so "tubey" as to be pretty unuseable. But, in the big picture, it's a combination of the tubes, the circuit and design techniques that make for a good sounding, useable, playable amp regardless of the number of tubes used. And, I have indeed designed enough multi-tube AND solid state preamps to justify my comments.

[Calaverasgrande]

the standard tube used in 90% (if not 99%) of amps is the 12ax7. This is a dual triode tube. this means that it has two gain elements in one package. So an amp that has one tube may be using that tube for preamp gain on one side and the other side can be, well anything the amp needs. Most often I think it is just used to drive the signal to the next circuit.
Most pres that have 3 or 4 tubes are pretty much an all tube preamp (with possible exception of graphic EQ). Most pres that have one tube are an all solid state pre that have a tube kind of duct taped on after the fact to give some "tube tone". To me its kind of silly to have an amp with only one tube in it and expect to get any benefit from that single tube. To my ears the euphonic quality of tubes is due to the other (non tube) parts of the amp. Most tube heads use passive equalizer designs that rely on having a tube after the EQ to recover gain lost by the eq. Solid state EQ usually functions with the transistor being part of the EQ (rather the eq is in the feedback loop of the transistor). Though you can certainly make a passive eq with a solidstate gain recovery. AFAIK every tube bass amp known to man, as well as every tube mic pre known to man involve transformers. If you compare a transformer coupled mic pre with tubes to one with transistors you will hear a lot of similarity. Take that transformer out of the circuit and use an op-amp instead and you get a more linear, flatter sound, but maybe not better!

So yeah, one tube=gimmick. 3 tubes means its a tube preamp, though with the raft of features that result from engineering by market research I kinda doubt that even a 4 tube pre is mostly tube these days. I suppose you could make a tube crossover though?

[JimmyM]

i'll say this for single tube pres...they always sound better to me with the tube involved. however, even though i think in some designs you're right that the pre tube is under-utilized, that's such a gross generalization that it sells short amps like the b-15n, which has a single tube pre, and the #2 channel on svt-vr's and vintage, which also has a single tube pre. nothing lacking in the pres of those amps whatsoever.

[agedhorse]

Originally Posted by Calaverasgrande

Most pres that have 3 or 4 tubes are pretty much an all tube preamp (with possible exception of graphic EQ). Most pres that have one tube are an all solid state pre that have a tube kind of duct taped on after the fact to give some "tube tone". To me its kind of silly to have an amp with only one tube in it and expect to get any benefit from that single tube.

I would like to characterize this statement as inaccurate and a gross oversimplification of a preamp design. It depends completely HOW the tube stages are used, the positions and slopes of the transfer curves and HOW they interface with the surrounding circuitry. Most quality designers will use however many tube gain stages required and in the topology they desire to achieve their design criteria.

Originally Posted by Calaverasgrande

AFAIK every tube bass amp known to man, as well as every tube mic pre known to man involve transformers. If you compare a transformer coupled mic pre with tubes to one with transistors you will hear a lot of similarity. Take that transformer out of the circuit and use an op-amp instead and you get a more linear, flatter sound, but maybe not better!

This is completely incorrect. I can't think of a single bass preamp that uses an input transformer or interstage transformer. Transformers have absolutely nothing to do with a bass preamp. I think you are comparing 2 different devices (mic pre and bass amp pre) without understanding the difference between the two. The input impedance of a bass amp is way too high to be useable with an input transformer, and there's no need for interstage transformer coupling as there are better ways to do this that the entire industry has enbraced. There is no need for an output transformer since the preamp is driving a fairly high impedance load (solid state power amp) which looks like a bridging load to the drive. (no relation to bridge mode in a power amp).

Originally Posted by Calaverasgrande

So yeah, one tube=gimmick. 3 tubes means its a tube preamp, though with the raft of features that result from engineering by market research I kinda doubt that even a 4 tube pre is mostly tube these days. I suppose you could make a tube crossover though?

A gross oversimplification IMO, and it is most definately possible to make a 1, 2, 3, or 4 tube preamp that is completely tube and without transformers. I have done it with up to 3 tubes and found no need for a 4th as I ran out of features at that point. Tube crossover? Sure, it's been done.

[WOOFMAN]

Kind goes back to the old days in the sixties(last century). Just about all electronics had tubes in them, ie. compressores, exciters, EQ's, preamps, poweramps and more...
I've seen pedal boards with one tube in them glowing and they seam to sound okay to me. But, for me the more tubes there are the happier I am. It's all in my head though.

[BassIan]

Originally Posted by agedhorse

I would like to characterize this statement as inaccurate and a gross oversimplification of a preamp design. It depends completely HOW the tube stages are used, the positions and slopes of the transfer curves and HOW they interface with the surrounding circuitry. Most quality designers will use however many tube gain stages required and in the topology they desire to achieve their design criteria.



This is completely incorrect. I can't think of a single bass preamp that uses an input transformer or interstage transformer. Transformers have absolutely nothing to do with a bass preamp. I think you are comparing 2 different devices (mic pre and bass amp pre) without understanding the difference between the two. The input impedance of a bass amp is way too high to be useable with an input transformer, and there's no need for interstage transformer coupling as there are better ways to do this that the entire industry has enbraced. There is no need for an output transformer since the preamp is driving a fairly high impedance load (solid state power amp) which looks like a bridging load to the drive. (no relation to bridge mode in a power amp).



A gross oversimplification IMO, and it is most definately possible to make a 1, 2, 3, or 4 tube preamp that is completely tube and without transformers. I have done it with up to 3 tubes and found no need for a 4th as I ran out of features at that point. Tube crossover? Sure, it's been done.

I just think this should be read clearly by everybody who sees this thread. Please understand the value of having an engineer who actually designs bass amplifiers weighing in here!

Everything above is entirely accurate. The tone of a particular piece of gear comes from HOW it is designed, which involves relationships between all components. Counting tubes (or transistors, MOSFETs, op amps, resistors, microprocessors, etc.) will not answer your questions about what an amplifier sounds like. Try them and listen with your ears to find the tone you like. When you start finding what you like, research the equipment that works for you to find out WHY it works. The more you learn, the more capable you will be of reproducing what works for you.

So, counting tubes won't answer any questions for you.

[jjl5590]

Originally Posted by Calaverasgrande

So yeah, one tube=gimmick. 3 tubes means its a tube preamp, though with the raft of features that result from engineering by market research I kinda doubt that even a 4 tube pre is mostly tube these days. I suppose you could make a tube crossover though?

So would you say the highly regarded Genz Benz shuttle series, which have one tube in the preamp, is a gimmick?

[Alexander]

Man, LOTS of decent amps only have 1 tube...

[agedhorse]

Originally Posted by Alexander

Man, LOTS of decent amps only have 1 tube...

Bingo, there's a LOT more that goes into a quality amp besides a tube(s). There's the DESIGN, which if not suitable to YOUR playing style, will not be helped by 1 tube or 100 tubes. There are plenty of manufacturers that make very good amps with one tube.

[johnk_10]

Originally Posted by jjl5590

So would you say the highly regarded Genz Benz shuttle series, which have one tube in the preamp, is a gimmick?

Not at all.
as it has already been clearly stated, it doesn't matter how many tubes are used in a circuit, it has to do more with how you use it (or them).

i've heard 100% solid state circuits that sound very tubey, and 100% tube circuits that sound like a sound solid state amp.
to me, its all about the design and not how many tubes are in it.

[R Baer]

Originally Posted by agedhorse

..The "number of tubes" is a marketing concept, "how the tubes are used" is an engineering concept.

A tube is just a tool that, depending on how it's used, can make an amp sound "tubey" or "solid state like" depending entirely on how it's used and what circuit it is used in. The circuit used is just as important as the tube itself...

+1 Absolute truth here. Our preamp's sound is derived not from the number of tubes, but from the overall circuit design in which those tubes were placed.

[JimmyM]

cal stirring the pot once again. honestly, i don't even think he believes half the stuff he says.

[seamonkey]

Originally Posted by agedhorse

The "number of tubes" is a marketing concept, "how the tubes are used" is an engineering concept.

As unpopular as it is on this board, you don't even need a tube to get "tube sound" - using a tube at all is a marketing concept.

[JimmyM]

Originally Posted by seamonkey

As unpopular as it is on this board, you don't even need a tube to get "tube sound" - using a tube at all is a marketing concept.

what a load of crap. this glorious "emulation" you keep hyping over tube amps has been good enough to compete with real tubes for about 2 years now. and it still isn't the same. yes, it can work very well, but for you to constantly call tubes a marketing concept is ridiculous and annoying and very untrue. of course, annoying people trying to have a discussion about tubes is your MO, so i'm not surprised.