Any pros/cons about an Ampeg SVT-CL, 2010 model?

[beans-on-toast]

Well I'll give you a more concrete reason not to use mismatched loads...it doesn't sound as good It always sounds slightly tighter and slightly more compressed to my ears.

A mismatched load will shift the operating point of the power tubes. The amp will sound different. How much so will depend on the design of the amp and amount of the impedance mismatch. So your ears aren't lying to you.

 

[jason the fox]

@ WretchedExcess:

almost over my head, but I've got more of a handle on it than I did. Excellent post(s) and very informative.

 

[WretchedExcess]

Let's keep things in perspective -- nobody's advocating an intentional mismatch as the normal operating condition for your SVT. The OP asked if he would run into problems trying out his new SVT with the only cab that he had -- an 8 ohm cab. In response, he got a bunch of FUD-rucking answers that told him that he shouldn't play his SVT into an 8-ohm cab, that he might break it, that it might not make it returnable if it broke, and that he should wait for a new cab before he played with his new amp.

That was really bad advice. For Pete's sake, the guy wants to try out his new amp and all he has is an 8-ohm cab, and the overwhelming response of the people here was one to promote Fear, Uncertainty and Doubt. That's just wrong.

I hope that if anything, the OP has learned that it's OK to plug his SVT into his 8-ohm cab and enjoy it while he waits for the new cab to arrive.

Now about tone -- Jimmy makes a good point -- optimal impedance will sound better / cleaner. The SVT was designed to operate at a primary reflected impedance that represents the lowest point on the impedance vs. distortion curve. Look here: this is the impedance characteristic for the GE-6550 tube operating in Class AB:

As I posted earlier, the SVT primary impedance for a sextet of tubes is 1850 ohms. That corresponds to 5550 ohms for a pair of 6550. Looking at the graph, we see that the distortion profile for the amp is at it's absolute minimum at around 5000 ohms. The SVT was clearly designed with HiFi reproduction and minmal distoriton in mind. If you want minimal distortion, operate with a matched load. If you want increased distortion, well, observe how the distortion increases if you mismatch either to the upside or the downside.

Beans makes a good point as well -- it always makes sense to operate in the middle of the SOA. that's what design center values are all about.

Now let's keep things in perspective. Nobody's recommending that you should go out and operate an SVT with a wildly improper mismatch. But those guys out there who keep harping on how dangerous it is to run an SVT into an 8 ohm load are just wrong. A 2:1 mismatch up or down is perfectly safe. The result will be higher distortion, and more or less power output, depending on where you decide to operate on the tubes' impedance characteristic.

The take home lesson? It's fine for the OP to plug an 8-ohm cab into his SVT and try out his new head. Just be sure it's capable of handling the power, so you don't blow the cab with too much enthusiasm.

 

[Psychobassguy]

A transformer is a coil with a primary and secondary connection. Any change to the secondary connection will be reflected back to the primary at the turns ratio of that transformer. Since speakers have impedance peaks all over the place, their connection ratings are the average of impedance across the entire frequency response of the speaker. The output tubes react to these impedance shifts by either increasing in plate voltage in the case of a high secondary impedance or lowering in plate voltage in response to a lower secondary impedance. The output transformer is wound to accommodate the operational limits of the tube and the average expected secondary impedance.

Putting an 8 ohm load on an SVT's 4 ohm output automatically shifts the operational voltages of the output tubes to a range potentially sustaining double the voltage of their idle state. Doing so across the 2 ohm tap is even worse. SVT's of all stripes generally run about 700 volts on the plates of their output tubes at idle. The operational limit of the 6550A and KT88 is 800 volts . Beyond that, the tubes themselves become prone to arcing internally and at their bases.

It is the output tubes to first feel the "pain" of a mismatched high load and they will demonstrate malfunction before significant damage occurs to the output transformer itself. All that is required is a single sustained impedance spike outside of the normal operation range of the transformer secondary to cause arcing in the tubes and output transformer.

With the SVT cabinet's original arrangement of eight 32 ohm speakers in parallel, all of the impedance resonances are averaged against each other, but in other multi-speaker cabinets, any series connection results in additive resonances increasing the chance of damage.

What this all means is that while an 8 ohm cabinet is not instant death for an SVT, it is certainly tempting fate. Considering the costs, voltages involved and the very real possibility of death by electrocution for the player from arcing voltages from the impedance mismatch alone, it is a situation best avoided.

 

[georgestrings]

No problem running an SVT with an 8-ohm cabinet at full power. I do it all the time.

Let's keep things in perspective -- nobody's advocating an intentional mismatch as the normal operating condition for your SVT. The OP asked if he would run into problems trying out his new SVT with the only cab that he had -- an 8 ohm cab. In response, he got a bunch of FUD-rucking answers that told him that he shouldn't play his SVT into an 8-ohm cab, that he might break it, that it might not make it returnable if it broke, and that he should wait for a new cab before he played with his new amp.

That was really bad advice. For Pete's sake, the guy wants to try out his new amp and all he has is an 8-ohm cab, and the overwhelming response of the people here was one to promote Fear, Uncertainty and Doubt. That's just wrong.

You've shifted positions - your first post on this subject was - and still is bad advice... Your 1st quote is directly contradicted by the 1st sentence of your next quote I posted - just sayin'...


- georgestrings

 

[beans-on-toast]

There's an old expression, do what I say, not what I do. In my case, I will push my amps under controlled conditions to see what will and won't work to determine what the limits are. There might be things that I do all the time with my amps that I wouldn't recommend that other do.

Under perfect conditions, you can get away with certain sins. Under not so perfect conditions, you might be pushing your luck.

 

[WretchedExcess]

.

... the very real possibility of death by electrocution for the player ...

.

STOP THE FUD!

I don't know where PsychoBannedGuy gets his ideas, but to me it seems like they reflect a total misunderstanding of how vacuum tube amplifiers work. There are so many bogus statements in his last post that it's not even worth addressing them all, I'm inclined to just discount the post as a whole.

I will, however, counter one point that he's made in his post -- his opinion that operating an SVT into an 8-ohm load presents a "very real possibility of death by electrocution for the player." That's complete malarkey, and it brings us to an all-time high in terms of the FUD-rucking posts about SVT operation. Now we've got people trying to intimidate end-users by telling them that their Ampeg product is inherently unsafe, and that it may STRIKE THEM DEAD if they make a mistake so minor as to hook up a speaker cabinet to the wrong impedance tap on the amp. What complete and utter BS.

It's important to keep in mind that hooking an 8-ohm speaker up to the 4-ohm output of an SVT reflects the same load impedance to the tubes as if you had hooked up a 4-ohm speaker to the 2-ohm output of an SVT.

It's also important to keep in mind that a 2:1 mismatch to the upside is something that's very easy to do -- on an amp with the slider-type of impedance selector like an SVT-2,. all that you have to do is to mistakenly have the impedance selector switched pushed down to the 2-ohm position for 2 fridge-type cabinets, and then hook up a single fridge-type cabinet without remembering to slide the impedance selector from 2-ohms back to 4-ohms.

On the new cabinets like the Heritage 810, this kind of mistake is as easy to make as plugging the speaker cable into the wrong jack. Even an experienced SVT user like Jimmy has made this kind of mistake and has lived to talk about it. But according to PBG, doing this subjects you to "the very real possibility of death by electrocution."

Bear in mind that Ampeg has been selling the SVT for 44-45 years, and that they've produced a whole lot of them. How many reports can you recall of a bass player being killed by his SVT?

Also bear in mind that Ampeg is building amplifiers that are UL-approved and CE-approved. It would be impossible for Ampeg to pass safety certification if the SVT were likely to kill it's end-user just because a back panel switch was improperly set, or because the end-user plugged a speaker cable into the wrong impedance tap on the output transformer, or the wrong jack on the speaker cabinet.

If the SVT were really this likely to kill people, then we'd see a lot of dead bass players lying in front of their amps, but we don't. We'd see lots of product liability lawsuits, but we don't. And we'd see Ampeg pulling the SVT from the marketplace in order to redesign it to make it safe so it doesn't go electrocuting end-users. But we don't see that happening either.

I think it's very unfortunate that there are fearmongers who are trying to intimidate end users, suggesting that the SVT is an unsafe amplifier that is likely to kill them. We don't need to hear BS like that.

 

[beans-on-toast]

If the SVT were really this likely to kill people, then we'd see a lot of dead bass players lying in front of their amps, but we don't.

Techs have been known to get zapped from working on them.

In the litigious society that we live in, I am amazed that someone hasn't tried to sue an amp company for making an amp that threw their back out.

 

[WretchedExcess]

Techs have been known to get zapped from working on them.

Yeah, but that's not an SVT-specific thing, that's a risk that any tech can run into when working on any amp if he lets his guard down. (or if he's just stupid!)

You know, there's a good reason that the old-timers like to keep one hand in their back pocket when they're working on a live circuit. It reminds me of the saying: "There are old techs, there are bold techs, but there are no old and bold techs." Safe technique matters when you have the safety panel removed from an amp chassis!

 

[beans-on-toast]

I'm ultra careful because I have a good respect for power. Like you said, you let your guard down, things happen and you get bit.
Thankfully, it's been many years since that's happened. Knock on wood.

 

[Mosfed]

Wouldn't the Ampeg 410 and 115 be a combined rating of 4 ohms? I know that running mismatched cabs is the reputational equivalent of being a child molester in prison here, but wouldn't it work until the OP gets his 810?

I miss my CL and it's intestinal discomfort inducing awesomeness.

This is clearly your answer if you are feeling impatient. I have used an svt with a 4x10 and a 15" plenty in the past and it's a good rig. Ok it's not a 8x10 or even a 6x10 but it works well.

I just got a slm 2001 svt-cl - super psyched. Great price too with new tubes. Can't wait to fire that puppy up at volume!

 

[tjconn]

Don't mess with this Amp in any load combos. Run it striaght to a 4 ohm cab. Anytime you see these heads they are almost always run through an 4X10 HLF or an 8X10. Huge Stadium shows may have the 2ohm load split into 2 4ohm cabs, but I would't mess with that unless I had a tech on tour with me.

I travel with the 4x10. I use the 8X10 in the studio. Nothing can touch the tone of CL/8X10/recorded on 2" tape. Except for maybe a Heritage or Vintage model.

With that said, I kind of have a love/hate relationship with my amp. It is in the shop a lot. I take a backup (b2R) on the road with me. A set of Sovtek power tubes are over 200.00. Ampeg reccomends that you re tube once a year.

The cost of maintenace is something to think of when buying this Amp.

 

[JimmyM]

Ampeg is being overly cautious in a world of baby whiners who can't figure out they have a bad tube when a tube amp goes on the fritz Actually, updated manuals don't say that anymore. They're more like they should be tested once a year now and changed whenever sound degrades. I've owned tube amps for 35 years, and the only time they need changed is when they break or get weak, and it may happen a week from now with one tube and the tube next to it could last 10 years.

 

[DiabolusInMusic]

Don't mess with this Amp in any load combos. Run it striaght to a 4 ohm cab. Anytime you see these heads they are almost always run through an 4X10 HLF or an 8X10. Huge Stadium shows may have the 2ohm load split into 2 4ohm cabs, but I would't mess with that unless I had a tech on tour with me.

I travel with the 4x10. I use the 8X10 in the studio. Nothing can touch the tone of CL/8X10/recorded on 2" tape. Except for maybe a Heritage or Vintage model.

With that said, I kind of have a love/hate relationship with my amp. It is in the shop a lot. I take a backup (b2R) on the road with me. A set of Sovtek power tubes are over 200.00. Ampeg reccomends that you re tube once a year.

The cost of maintenace is something to think of when buying this Amp.

You can ignore this advice.

I ran my SVT-CL with a 6 ohm load for over a year. It was perfectly fine, it just eventually blew a power tube. That is all that happens. It works fine once you put a new tube in, or in my case, the old tube.

I cannot even comment on the science spilled in this thread, it is WAY over my head.

 

[xshawnxearthx]

Dude, run that 410 and 15. You will not destroy 15. I used to run that same combo with a 4 pro and it took all the abuse the 4 pro could throw at it.