Tube power sections, what am I missing?

[Chris 'Wighat' Jordan]

What?? You saying the Mesa was the copy? I don't know, I didn't buy them I just played them! The SVT was not the "classic" SVT, it had that normal Ampeg tone controls, with the ultra deep and bright switches, but also had a graphic EQ. Was that an SVT II or a II Pro? Are there two different II Pros they made?

Teach me, don't laugh at me. Those two sounded the best, the Aggie was a bit quiet and I ended up driving it pretty hard, although it still worked even pretty heavily overdriven.

I get it, the 400 and the SVT II have some similarities: rack-mount and graphic EQ. And the Mesa came out first. But I think it's more like the opposite: the SVT was already THE bass amp but 1985 was rock-bottom for Ampeg, you probably couldn't buy a new SVT so Mesa saw an opportunity to be the big power, all-tube amp on the market. But Ampeg rebounded and the SVT II is just an SVT in a rack-mount chassis with graphic EQ. Did Ampeg copy Mesa with the SVT II? I don't see it. You copy something because it is immensely popular. I had never even heard of the Mesa 400 until I got on Talkbass so I don't see Ampeg having any motive to knock it off. My best guess is Ampeg simply wanted to modernize the SVT to reflect contemporary gear trends.

 

[Worldeeeter]

You have now encountered the dangers of online forums. The concept of everyone having their own personal preferences is diluted from reading forum threads, and everyone starts questioning every piece of gear they own. Next thing you know, everyone thinks they need to try something different. Neck-through vs. bolt-on, tube vs. SS, Class A/B vs. class D amps, rounds vs. flats...and on and on and on.
I'll tell you what you're missing: back pain. Lugging around an 80-lb. head is no picnic. I'll have none of it. Of course, there's always the chance that you'll love a tube head, but I wouldn't place a $1200 wager on that. Not worth it. Find someone local that has one and try it out.

Of course, all of the second-guessing isn't that bad. Many folks have found some spectacular gear from trying a move in another direction, many times on here.

 

[bassboysam]

The good tone is from the pre-amps

lol.

 

[GreyBeard]

One thing I failed to mention is power section of tube amps and soft clipping. You have to push them right to the edge of breaking distortion to experience this but it is a band of power that while somewhat distorted sound musical and SS amps can not do this. When SS amps break into distortion it is instant square wave fart city. You have to be playing very loud or be using some sort of power soak to achieve this effect unless you are using a low wattage tube. Hence the popularity of 7-15 watt tube guitar heads and 25-40 watt tube bass heads.

 

[somebrains]

I get it, the 400 and the SVT II have some similarities: rack-mount and graphic EQ. And the Mesa came out first. But I think it's more like the opposite: the SVT was already THE bass amp but 1985 was rock-bottom for Ampeg, you probably couldn't buy a new SVT so Mesa saw an opportunity to be the big power, all-tube amp on the market. But Ampeg rebounded and the SVT II is just an SVT in a rack-mount chassis with graphic EQ. Did Ampeg copy Mesa with the SVT II? I don't see it. You copy something because it is immensely popular. I had never even heard of the Mesa 400 until I got on Talkbass so I don't see Ampeg having any motive to knock it off. My best guess is Ampeg simply wanted to modernize the SVT to reflect contemporary gear trends.

I had an SVT and a 400 in the late 80's/early 90's.
It was the end of the than era, dawn of the Soviet sourced tube, and hybrid was still a buzzwordy "lookeet mah toobz preez amps" deal.

Crazy power specs were common, and highly suspect.

If you wanted something SS and reliable, GK.
SWR, Demeter, and Eden were the IT brands in every magazine.

As someone mentioned, racks were the thing to have.

The cool guy setup was a Crown or Crest SS amp and a tube preamp.

I remember when Ampeg put out their tube power amp and tube preamp.
They were glorious sounding, but you'd lug around a bugger package than an SVT head for basically the same performance as an SVT 2.

So this was the era when the VTEC Integra and M5 were just emerging as the cars we know now.

That's your SS modern class D head.
It's been refined over time but the general idea is a no muss, no fuss, turn the key and stomp the throttle car.

Tube amps are like a 71 Chevelle that's been thru a lot of hands.
Many don't know what a ball joint is, or had an old restoration.
Breakdowns are few and far between bc you can drive a tube head or 71 Chevelle into the ground.
They're built "loose", and are simple.

Give me a car prepped to own the 1/4 mile and nothing else, I will drive it on the track. I'll change it's plugs often, I'll flush it's fluids often, and I will monitor and baby the few things on it that make it run. Really, there ain't much there.

Give me a E39 M5 to commute with, and I can keep it running.
I'll drive it everyday to work, and keep an eye on the many things that you need to for optimal function, and I'll be fine. That's an old hybrid AB head.

Give me some POS Kia gas saver junk that I drive until I throw it away. It's cheap, has some features I don't use, and is utterly replace be bc I have no real attachment to it as a thing I can wrench on and be satisfied by. It placates your needs, it doesn't really fulfill any desires, like many class D heads.

I guess if your desires are for a disposable car that's not user serviceable you can go the Tesla route, but I'll still smoke you in an E39 M5 or track car loving every 1/10th of a second doing it. I guess my Magellan 800 is that.

I could pretend my cars do something they can't, but I don't pretend my amps do. That's silly, as silly as a AMG G55 thinking it's a race car.

I also don't pretend my W $$'s do what at my Stingray, Spector, or P do.

 

[Deleted member 165050]

That's silly, as silly as a AMG G55 thinking it's a race car.

You mean one of these? Hideous wheels don't you think...

 

[CRich0205]

I had an SVT and a 400 in the late 80's/early 90's.
It was the end of the than era, dawn of the Soviet sourced tube, and hybrid was still a buzzwordy "lookeet mah toobz preez amps" deal.

Crazy power specs were common, and highly suspect.

If you wanted something SS and reliable, GK.
SWR, Demeter, and Eden were the IT brands in every magazine.

As someone mentioned, racks were the thing to have.

The cool guy setup was a Crown or Crest SS amp and a tube preamp.

I remember when Ampeg put out their tube power amp and tube preamp.
They were glorious sounding, but you'd lug around a bugger package than an SVT head for basically the same performance as an SVT 2.

So this was the era when the VTEC Integra and M5 were just emerging as the cars we know now.

That's your SS modern class D head.
It's been refined over time but the general idea is a no muss, no fuss, turn the key and stomp the throttle car.

Tube amps are like a 71 Chevelle that's been thru a lot of hands.
Many don't know what a ball joint is, or had an old restoration.
Breakdowns are few and far between bc you can drive a tube head or 71 Chevelle into the ground.
They're built "loose", and are simple.

Give me a car prepped to own the 1/4 mile and nothing else, I will drive it on the track. I'll change it's plugs often, I'll flush it's fluids often, and I will monitor and baby the few things on it that make it run. Really, there ain't much there.

Give me a E39 M5 to commute with, and I can keep it running.
I'll drive it everyday to work, and keep an eye on the many things that you need to for optimal function, and I'll be fine. That's an old hybrid AB head.

Give me some POS Kia gas saver junk that I drive until I throw it away. It's cheap, has some features I don't use, and is utterly replace be bc I have no real attachment to it as a thing I can wrench on and be satisfied by. It placates your needs, it doesn't really fulfill any desires, like many class D heads.

I guess if your desires are for a disposable car that's not user serviceable you can go the Tesla route, but I'll still smoke you in an E39 M5 or track car loving every 1/10th of a second doing it. I guess my Magellan 800 is that.

I could pretend my cars do something they can't, but I don't pretend my amps do. That's silly, as silly as a AMG G55 thinking it's a race car.

I also don't pretend my W $$'s do what at my Stingray, Spector, or P do.

This is a fantastic description. Well put

 

[JimmyM]

What?? You saying the Mesa was the copy? I don't know, I didn't buy them I just played them! The SVT was not the "classic" SVT, it had that normal Ampeg tone controls, with the ultra deep and bright switches, but also had a graphic EQ. Was that an SVT II or a II Pro? Are there two different II Pros they made?

Teach me, don't laugh at me. Those two sounded the best, the Aggie was a bit quiet and I ended up driving it pretty hard, although it still worked even pretty heavily overdriven.

Well now that you made me feel bad I goofed on you...


The 400 and 400+ were not SVT clones, nor vice versa. They had completely different design philosophies. Ampeg got their watts with fewer power tubes and big transformers. Mesa did the opposite. plus if I'm not mistaken, Mesa used the Fender tone stack or something pretty similar. They both had graphic EQ's, but at the time, graphic EQ's were big. But as Corey said, the SVT II was basically just the normal channel 1 of a regular SVT with a graphic. Same for the SVT 2 Pro, except it added a separate gain/master and a second drive switch. There were a couple variations of the SVT formula in these amps, but the end result sounded pretty much the same.

 

[mesaplayer83]

lol.

Yeah, I thought that was funny, too - guess who is invested in amp modeling? - lol

 

[somebrains]

You mean one of these? Hideous wheels don't you think...

Remember these? Loud exhaust, weigh a ton, can't take it fishing bc deep in the woods bc the wheelbase is too short. Owners thought they really had the do it all, but it didn't do much really well.

Tube amps do things really well.

AB, and hybrid AB, do things really well.

Class D does things really well.

Try to tell me how they replace each other and I'll imagine Spam jello parfait for breakfast.

If you wanted something like the GK400RB back in the day, you could get a D180 really cheap. Get everything super hot. It's like my Electric blue head in that jazz or upright guys really liked them.

People think they need a supercharged 550hp car all the time when it's hard for a good driver to use 300hp fully on the street.

 

[HolmeBass]

Well now that you made me feel bad I goofed on you...


The 400 and 400+ were not SVT clones, nor vice versa. They had completely different design philosophies. Ampeg got their watts with fewer power tubes and big transformers. Mesa did the opposite. plus if I'm not mistaken, Mesa used the Fender tone stack or something pretty similar. They both had graphic EQ's, but at the time, graphic EQ's were big. But as Corey said, the SVT II was basically just the normal channel 1 of a regular SVT with a graphic. Same for the SVT 2 Pro, except it added a separate gain/master and a second drive switch. There were a couple variations of the SVT formula in these amps, but the end result sounded pretty much the same.

Thanks for the explanation. For me, compared to SS rigs, they seemed quite similar, and definitely playing in a band setting was an eye-opening experience.

 

[bassliner50]

Tube circuitry adds significant weight. That for me, is a negative I cannot ignore at my age. Life is always full of compromises.

 

[bobyoung53]

Here's a question, in looking at the Ampeg SVT-VR reissue (new) and consideration in purchasing an old one in decent shape. Besides the obvious with the used one, making sure it works, having it gone through and possibly retubed by a pro.

Are there any real differences in the sound?

I've never owned or played through a VR although others say they sound the same but I will tell you one thing the 70's heads last a LONG time and sound good, as long as you get them checked once in a while depending on how often you play they are virtually indestructible. I recapped mine about 15 years ago, re-tube them once in a while (power tubes), have them in for service once in a while and don't worry about them, they always work.

 

[Metropolis_488]

Can someone explain what I'm missing with a tube power section? I'll take the plunge if needed at some point.

Several people already pointed out the simple reality that you need to try one for yourself. No amount of flowery language can replace what you will or will not hear and or feel when playing through a full tube amp.

You're not missing anything if you like the sound you got.
There is nothing magical about tube power sections. Reverse is also true, nothing magical about solid-state (any class) power sections. The good tone is from the pre-amps

You are correct in your assessment of magic - either pixie, dark, wiccan, vulcan or other. They don't exist and do not influence amplifiers.

The statement "Good tone is from the pre-amp" is grossly reductive. I didn't know the pre-amp was the only variable in a signal path... Also, solid-state is not a "Class" of amplifier such as "A" "B" "A/B" and "D".

Much of the compression and "sag" associated with tube power amps comes from the output transformer - not the tubes themselves. One only needs to measure (and hear) an output transformerless hifi tube amp to understand that all that "warmth" is not coming from the tubes themselves. It's part of the reason why Warwick sold that Hellborg SS amp with an output transformer in it and everyone remarked how "tube-like" it sounded. As a matter of fact, that seemingly antiquated technology that is found in a vacuum tube is, to this day, a far more linear output device than any "solid-state" component when examining output current relative to input voltage. It's why people are willing to spend a luxury car's worth on an 8 watt hifi single-ended triode stereo amp.

You may not like the sound of a tube power section, but the topology has a significant influence on what comes out of the speakers - the pre-amp is only one part of the chain.

Except, don't think that experienced amplifier designers haven't gone through this with decades of experience and research. There actually are designs of power amps, of any kind, that have a good overdriven tone.
Just waiting until the power section is overdriven would not be a popular design, or overall useful. An amp needs good tone quiet or loud.

Experienced amplifier designers work within a given set of requirements and then try and balance compromises between pre-defined measurable performance criteria and other factors such as cost, assimilation to existing production methods, component size, heat, safety regulations etc.

Also, if I am an engineer, and you task me to build and amplifier and the only requirement is to make it sound "good" - I will have no idea what to do. "Good" means different things to different people.

Conversely, you can provide a spec, such as "I want the amp to produce a max total harmonic distortion of -128 db and be even-order harmonic dominant". But this is still incomplete. You made the requirement "An amp needs good tone quiet or loud." Let's ignore what "good" means for the moment. Maybe you want it to sound the same at all volumes within the rest of it's design parameters... well, if you can achieve this, you would likely receive some award in electro-mechanical engineering. The reason being that every component used to build an amplifier behaves differently at various voltages. Beyond that, the speaker you are attaching the amplifier to will vary it's performance dramatically at different voltages and impedance - remember, that tag on the back of the speaker cabinet that says "8 ohms" is only nominal. The speaker may very likely dip down to 2 ohms when fed a 40hz signal. That 2 ohm load will draw a crap load of current from the amplifier for a couple of milliseconds, which will, in turn, change the performance, and resulting sound of the amplifier. This is a simplified explanation as to why power amps arguably have a LARGER impact on your overall tone than preamps. The power amp is dealing with higher voltage, higher amperage, and is tasked with controlling an unruly set of speakers. The preamp just needs to pass a line-level signal that has been buffered.

Just waiting until the power section is overdriven would not be a popular design, or overall useful.

Literally THOUSANDS of guitar players since the late 1960's with Marshall Plexi amps disagree with you on this point... Beyond that, many of the "great" bass tones over the years have been achieved by saturating the power section of a tube amp...

 

[baxter_x]

Interesting thread as I'm an SS guy. Not that I don't like tubes amp, it's just their weight I don't like. But next year I'll probably buy an SVT-CL or an SVT 2 Pro just to check once for all if all tube is as good as it is
.
I rented an SVT 2 pro a several months ago (check my signature) and was not impressed with it. I compared it with my SVT 4 Pro and was impressed how similar they were. I even had to visually check in what amp my bass was plugged to know what amp I was playing. On the clean side they were sounding exactly the same to me.
However I admit the best way to try an amp is onstage.

 

[Matthijs]

I have been a believer in "the sound is in the pre-amp" for over 30 years, until I played a SVT at full clean volume a year a go. First time I ever did a whole gig with a tube power section. This was a doubling gig with DB, so it was all about a clean sound. Even while I disliked the tone section and the overly dark Ampeg cab, the amp did it for me. I ended up customising an old Dynacord to fix my newfound tube craving. It is clean and hifi sounding ánd distinctly tubey. It's not a matter of EQ or overdrive, it's about filling up every single note with beautifull, musical, tailormade harmonics.

Did I miss something for those 30 years? For my kind if gig I probably will keep on using my hybrid amp. The size and weight of the Dynacord are just impractical and the difference in sound is too subtle to survive a 12 piece horn band. It is the only amp I use at home and on recordings know. And I'll probably take it out on special occasions. I made a special low efficiency cab for it so the amp has to work a little even at moderate volumes.

 

[baxter_x]

it's about filling up every single note with beautiful, musical, tailormade harmonics.

That's exactly my experience with all tub amps. In September we had a gig where an Ampeg SVT-CL Heritage was provided as backline amp. I A/Bed it against my SVT 4 pro. While they had both the "same" sound, I noticed the CL was producing a lot more harmonics than the SVT 4. This very detail made the SVT 4 sound "darker". However, to me they had the same fat growly sound.
According to my experience with all tube amps, it's all a matter of harmonics they produce.

 

[sratas]

Agree with baxter

 

[jazzbass_5]

Thank you for all your insights, I'm sure in the next few years I'll be picking one up, probably a reissue. Unless I find a deal on a vintage VR in great shape.
I really have collected and built some great equipment (3 of my cabs are DYI and have served me well for years) I don't -need- for anything, it would be more of a gift to myself and a luxury to own an SVT-VR.

 

[lowend1]

It probably is. But this business about tube power only mattering when you use overdrive is a bunch of poopity stinkity...

TalkBass: an invaluable resource for upgrading one's vocabulary of technical terms.