Ampeg SVT really 960 watts?

[BogeyBass]

Maybe on the most amazing day on the bench and really really high line voltage.

I'm sure you could measure at 15 to 20% distortion and maybe get 338/ 342 watts.

Then of course round it up really really high.

Awwww it's 350 watts lol.

At 6% distortion and 750 volts a 6146 pair can do 120 watts.

But at Ampeg voltage and load line. Assume the usual 290 to 330 watts.

and of course screen melting failure.
Like it did on it's debut

Ironically it's pretty notorious long hour tube for communication and JAN production. Military actually still made these things till the mid 1980s.

This being a good 5/10 years past the point when most American tube manufacturing and sales was pretty much over.

 

[BurningSkies]

hmmm ... it appears that many/most SVTs with modern tubes scope between 240-270w ... not 300 as the Ampeg marketing blah blah blah screams ...
"This dynamically powerful all-tube bass amp delivers a thunderous 300-Watts of unsurpassed quality, reliability and tonal flexibility"

I know 300watts sounds better than 270ish in ad copy, but isn't that also somewhat dishonest ?

and the TC thing ... really ? after 4 or 5 years is this still a thing ?

Yeah, Mesa did that trick with that new-fangled amp, the 400+ too. 12x 6L6 doesn't make 400+ watts.

Other modern companies have less egregiously (than TC anyway) flexed numbers. For instance some of the more recent class D Peavey amps have been 'burst rated' which is a step further than even peak rating. But at least they honestly said that's how they rated and you could dig to find RMS numbers.

 

[Wasnex]

Maybe on the most amazing day on the bench and really really high line voltage.

I'm sure you could measure at 15 to 20% distortion and maybe get 338/ 342 watts.

Then of course round it up really really high.

Awwww it's 350 watts lol.

At 6% distortion and 750 volts a 6146 pair can do 120 watts.

But at Ampeg voltage and load line. Assume the usual 290 to 330 watts.

And and of course screen melting failure.
Like it did on it's debut

Ironically it's pretty notorious long hour tube for communication and JAN production. Military actually still made these things till the mid 1980s

Please see the following SVT CL bench test. At around 10:00 in the video, the amp makes 308W at 7% and then he bumps the power up to 340W at 10.7% distortion. At 10:40 he shows 240W at 5.8%. These measurements were at 100hz.


Pretty sure it's fairly common for 6146 based amps to make 350W at 5% if they are setup well.

The early amps did have a tendency for breaking down because of the way the driver tubes were setup. Basically when a strong enough transient was played, the first triode of the driver would push the second triode into blocking distortion, and this would cause the bias on the output tubes to collapse. Without bias the output tubes conduct as hard as they can, and self destruct very quickly. In 1970 a factory mod fixed this problem by building in node H of the power supply to reduce the plate voltage of the first section of the driver tubes by about 218V.

 

[JimChjones]

It does occur to me though, pace the nonsense surrounding the underpowering myth, there might be a certain amount of logic in matching the peak power of an instrument amplifier to the RMS power of a speaker system.

 

[BurningSkies]

It does occur to me though, pace the nonsense surrounding the underpowering myth, there might be a certain amount of logic in matching the peak power of an instrument amplifier to the RMS power of a speaker system.

I'm not against a few different ratings paradigms in amps or cabs...as long as people know what you're doing and how you've come to those numbers.

 

[agedhorse]

Yeah, Mesa did that trick with that new-fangled amp, the 400+ too. 12x 6L6 doesn't make 400+ watts.

Other modern companies have less egregiously (than TC anyway) flexed numbers. For instance some of the more recent class D Peavey amps have been 'burst rated' which is a step further than even peak rating. But at least they honestly said that's how they rated and you could dig to find RMS numbers.

The Bass 400 and 400+ is a little confusing and misleading without knowing more about the history and especially the evolution of the different version within the 400+ model.

From the original 6 x 6550 Bass 400, there were difficulties getting reliable deliveries of tubes going back maybe 30 years so Randy decided to go with a tube that he knew well, had good performance, and that the company had an excellent and consistent supply of. First starting with the 5881, we were able to get about 45-50 watts per pair and more importantly had a nice tone (especially when overdriven) that was more forgiving than the 6550 (under that particular topology). I believe we built some earlier 400+ units with these tubes and they were around 300 watts RMS at somewhere around 3-5%THD. This was just a precursor to the more common version with screened 6L6GC tubes which in the circuit that is used can generate approx. 65 watts/pair at between 5% and 10% THD (since that's how this amp was being used, few bought it as a "clean amp"). 65W x 6 pair = 390 watts RMS and because of the combination of plate loading and a supply compliance, a ~20mSec burst was capable of roughly 500 watts RMS. Note that measuring burst power in the old days was much harder and less accurate than it is today using (for example) an AP system, so +/-25 watts would not be uncommon or unreasonable. The + references the burst power or transient power, something that is common in many of Randy's designs going back decades. It's not some kind of fad...

Note that only the GC version of the 6L6 should be used in any of these amps that originally came with the 6L6GC (STR 440) version. While the 5881 is a ruggedized, high voltage graded tube, driving the 400+ very hard will reduce the life of the tube by as much as 50% due to limits in long term plate dissipation. Under more reasonable use, there's not much difference in lifespan. This is one of the reasons for the migration to the 6L6GC (which is also graded for high voltage and mechanical noise in our branded tube).

The regular 6L6 variants are not very suitable for this amp, lifespan will be short when driven hard and there may be serious and damaging issues with voltage limit thresholds

 

[agedhorse]

It does occur to me though, pace the nonsense surrounding the underpowering myth, there might be a certain amount of logic in matching the peak power of an instrument amplifier to the RMS power of a speaker system.

Peak power of an amp is 2x the RMS power, which would result in plenty of safety margin for the speaker but ~3dB given up in potential performance if matching RMS to RMS.

 

[walterw]

troll thread becomes worthwhile at the end!

 

[BogeyBass]

Please see the following SVT CL bench test. At around 10:00 in the video, the amp makes 308W at 7% and then he bumps the power up to 340W at 10.7% distortion. At 10:40 he shows 240W at 5.8%. These measurements were at 100hz.


Pretty sure it's fairly common for 6146 based amps to make 350W at 5% if they are setup well.

The early amps did have a tendency for breaking down because of the way the driver tubes were setup. Basically when a strong enough transient was played, the first triode of the driver would push the second triode into blocking distortion, and this would cause the bias on the output tubes to collapse. Without bias the output tubes conduct as hard as they can, and self destruct very quickly. In 1970 a factory mod fixed this problem by building in node H of the power supply to reduce the plate voltage of the first section of the driver tubes by about 218V.

Well that's kinda the thing.

I totally accept 340 watt rms bench marks
And yeah on a good day 350 watts is feasible for 6146.

I'm being turd on purpose cause I have secret fantasies about the 6146. And want people to be scared lol

Kinda over looked tube cause of it's bad reputation with the SVT.

Ironically there is literally thousands of very very high quality NOS General Electric JAN production tubes laying around from the 80s

Smoking bad boys that can be pushed at 750 volts.

So yeah we're talking 120 watt per pair at 6% 140 ish at 10/15%

Make for 420 watt 6x application.

People be scared. 420 watts with 6146? Lol.

People might think...
Dude is my house gonna burn down.
Nah bruh. Don't be scared

Can I get certified with dos wittle wires on the top . I don't need certification to torture military tubes lol

 

[BurningSkies]

The Bass 400 and 400+ is a little confusing and misleading without knowing more about the history and especially the evolution of the different version within the 400+ model.

From the original 6 x 6550 Bass 400, there were difficulties getting reliable deliveries of tubes going back maybe 30 years so Randy decided to go with a tube that he knew well, had good performance, and that the company had an excellent and consistent supply of. First starting with the 5881, we were able to get about 45-50 watts per pair and more importantly had a nice tone (especially when overdriven) that was more forgiving than the 6550 (under that particular topology). I believe we built some earlier 400+ units with these tubes and they were around 300 watts RMS at somewhere around 3-5%THD. This was just a precursor to the more common version with screened 6L6GC tubes which in the circuit that is used can generate approx. 65 watts/pair at between 5% and 10% THD (since that's how this amp was being used, few bought it as a "clean amp"). 65W x 6 pair = 390 watts RMS and because of the combination of plate loading and a supply compliance, a ~20mSec burst was capable of roughly 500 watts RMS. Note that measuring burst power in the old days was much harder and less accurate than it is today using (for example) an AP system, so +/-25 watts would not be uncommon or unreasonable. The + references the burst power or transient power, something that is common in many of Randy's designs going back decades. It's not some kind of fad...

Note that only the GC version of the 6L6 should be used in any of these amps that originally came with the 6L6GC (STR 440) version. While the 5881 is a ruggedized, high voltage graded tube, driving the 400+ very hard will reduce the life of the tube by as much as 50% due to limits in long term plate dissipation. Under more reasonable use, there's not much difference in lifespan. This is one of the reasons for the migration to the 6L6GC (which is also graded for high voltage and mechanical noise in our branded tube).

The regular 6L6 variants are not very suitable for this amp, lifespan will be short when driven hard and there may be serious and damaging issues with voltage limit thresholds

Yeah, I'd have suggested it was 270-300ish with a lower THD, I'd never think to rate it at 10% or something like that...but then I'm not looking for distortion. I knew when buying that it wasn't necessarily a 400w amp, so going into that with a track record given it had been around for 20+ years by that time...

I only kept it around for about a year...I really just couldn't find love for it. I was always tweaking to find a tone I liked and I just couldn't though I know how the tone stack worked and I tried using both channels solo and together. In the end it just wasn't the amp for me.

Also, the DI on the one I had was definitely not right, and rather than fight my way through get that sorted out, I ended up moving on.

 

[agedhorse]

Yeah, I'd have suggested it was 270-300ish with a lower THD, I'd never think to rate it at 10% or something like that...but then I'm not looking for distortion. I knew when buying that it wasn't necessarily a 400w amp, so going into that with a track record given it had been around for 20+ years by that time...

I only kept it around for about a year...I really just couldn't find love for it. I was always tweaking to find a tone I liked and I just couldn't though I know how the tone stack worked and I tried using both channels solo and together. In the end it just wasn't the amp for me.

Also, the DI on the one I had was definitely not right, and rather than fight my way through get that sorted out, I ended up moving on.

We found that most of these amps were being used by guys playing hard rock and metal, they preferred the tone when driven hard, well beyond the 10%. It was kind of the market that we were in at the time (and still are to an extent) but it's also an amp that has a voice that may not work well as it has a bit of brashness that some find challenging. There's a lot of charm in the amp's basic architecture, but this amp was voiced to be a bit "rude and imposing" for the hard rock market. Perhaps I will revisit the (basic) architecture sometime down the road, being aware that your comments are not unique would suggest updating the voicing to be a bit more player-friendly for today's player it anything was to ever come of it.

 

[BurningSkies]

We found that most of these amps were being used by guys playing hard rock and metal, they preferred the tone when driven hard, well beyond the 10%. It was kind of the market that we were in at the time (and still are to an extent) but it's also an amp that has a voice that may not work well as it has a bit of brashness that some find challenging. There's a lot of charm in the amp's basic architecture, but this amp was voiced to be a bit "rude and imposing" for the hard rock market. Perhaps I will revisit the (basic) architecture sometime down the road, being aware that your comments are not unique would suggest updating the voicing to be a bit more player-friendly for today's player it anything was to ever come of it.

Yeah, it was definitely a 'rock' amp for a long time by reputation, but I know a bunch of guys who came to them because you could theoretically do 'tube' at loud volume without breakup. And for me it was really the last of the all tube amps I used on stage. I found that it always felt a bit 'cold' to me and again I couldn't quite get the EQ to do what I wanted, which was sort of frustrating to me since it also was a 'fender style' tone stack, and I've had numerous Fender amps that were no problem to dial in. Lots of guys loved them and I have no doubt that if Mesa decided to revisit it, they'd probably have a winner even if it was a more limited production type unit (not too many people looking for that size/heft these days). I love tube tone but don't look for any distortion from the power stage, so if I'm going to get loud (and I do), clean reliable high headroom is my thing.

My next step was to go to really nice handbuilt tube preamps and huge class D power amps. And oddly after the Mesa; my first choice was the Kern, also based on the ol' tone stack...Still have that one in the rotation for some things.

 

[JimChjones]

Peak power of an amp is 2x the RMS power,.

Ha, I knew that, but it wasn't what I meant! I'm guilty of the sin of misusing a word that that is a technical term, which is a guaranteed way to cause confusion.

What I sort of had in mind was the highest output that the amplifier can sustain over a reasonable length of time, irrespective of distortion levels. With the speaker rating being the power level the driver can handle over a reasonable length of time, it seemed to me the two could usefully be matched.
But even then I'm being oversimplistic, 'cos there's also cone excursion to consider, and presumably that's vulnerable to transient events which it seems on some amplifiers at least may be greater than sustained power.
So perhaps I now conclude the subject is sufficiently complex that the end user is better off with RMS figures and some rules of thumb. What we have now in fact...

 

[Wasnex]

Yeah, I'd have suggested it was 270-300ish with a lower THD, I'd never think to rate it at 10% or something like that...but then I'm not looking for distortion. I knew when buying that it wasn't necessarily a 400w amp, so going into that with a track record given it had been around for 20+ years by that time...

I only kept it around for about a year...I really just couldn't find love for it. I was always tweaking to find a tone I liked and I just couldn't though I know how the tone stack worked and I tried using both channels solo and together. In the end it just wasn't the amp for me.

Also, the DI on the one I had was definitely not right, and rather than fight my way through get that sorted out, I ended up moving on.

When I listen to other people play a Mesa 400, it sounds awesome. But the few times I have played one I had hard time dialing it in. I find my M9 and Titan a bit difficult to dial in too. I just assumed that's the way the older Mesa tone controls work. They just seem to lack a certain finesse or eloquence that allows me to get them exactly where I want them to be, although getting them close is no problem. These amps do tend to sound really great in the context of a mix IHMO, so maybe I shouldn't worry so much .

 

[Wasnex]

I'm being turd on purpose cause I have secret fantasies about the 6146. And want people to be scared lol

Just don't hog all of them as I will eventually need a new set for my 69 SVT.

 

[BurningSkies]

When I listen other people play a Mesa 400, it sounds awesome. But the few times I have played one I had hard time dialing it in. I find my M9 and Titan a bit difficult to dial in too. I just assumed that's the way the older Mesa tone controls work. They just seem to lack a certain finesse or eloquence that allows me to get them exactly where I want them to be, although getting them close is no problem. These amps do tend to sound really great in the context of a mix IHMO, so maybe I shouldn't worry so much .

Frustratingly close but inducing me to spend half the set trying to adjust it that last 10% and not getting it.

 

[BogeyBass]

Think adjusting the tone is fun.
Wait for the power amp tube change bill
Lol

I remember a backlined show with a 400+
And just couldn't work around the random knob fiddles from previous bands.

Dialed it in with a Boss Multi band EQ pedal. The guy just bought the thing brand new and was appalled that a 60 dollar pedal was even near his wittle expensive amp lol

 

[agedhorse]

Little difference in cost compared to changing a set of tubes in an SVT (including driver tubes). Don't know why such a knowledgeable chap as yourself would be surprised?

 

[JimmyM]

Little difference in cost compared to changing a set of tubes in an SVT (including driver tubes). Don't know why such a knowledgeable chap as yourself would be surprised?

I can usually get a pair of 6L6GC's for $35-40. A single 6550 costs $35-40. So it's true that there wouldn't be a major difference in price to retube either.

 

[Koshchei]

Great amplifier comparisons by Jimmy! I loved that post in this thread!

Here is TC's claim on how they rate power:
Link Removed
Interesting that the Blacksmith is supposed to be 1600W @ 4 ohms....yet it seems that "long term" it's actually 924W @ 4R?

I'm in full agreement that a watt is a watt. Hard to argue a proven scientific measurement.
However, when watts are used to describe the perceived volume of an amplifier a battle starts between objectivity and subjectivity. I personally blame my experience when I bought my first bass amp, I was told by plenty of sales associates and other bass players that a tube amp would have the perceived volume of 3 to 4 times the power rating of a solid state amp. Making the 300W All tube wonder known as the SVT technically "sound like" it's producing 900W to 1200W of "solid state power", but I've never saw true scientific proof of this.

Can we blame Sweetwater???
https://www.sweetwater.com/sweetcare/articles/tube-amps-louder-than-solid-state-amps-of-same/

The fundamental issue is that watts are not a measurement of volume, perceived or measured. If I were to build a bass amp, it might be 1800 watts, but those watts would be being applied to burning my house down, not making sound. When you use a watts rating as a general indicator of volume, you're making some fundamental assumptions about efficiency, point of measurement, and amp behaviour, which won't be true of all designs.

It's a little like using clock frequency as a measure of CPU performance back in the early 00s: the amount of work being done per cycle can be vastly different, depending on architecture. The culmination of this was the low clocked AMD Athlon, which was VERY fast but had a low clock speed, compared with the Intel Pentium4, which did very little per clock cycle, but operated at ridiculous frequencies.

Fortunately, we DO have a measure for volume: decibels. Given a totally flat EQ, a few reference cabinets/speaker configurations with declared speaker efficiency and room dimensions, point of measurement, air pressure, humidity, and temperature, it would provide a solid apples:apples comparison across the amp's range, at least until the marketing people get involved and start messing things up again.