Are solid-state amps subject to speaker load restrictions like tube amps?

[Mango Moon]

Just to clear this up, I sent an email to Fender customer relations. The response was the opposite of 1) and 2) above. This makes the most sense. Either use no speakers or both left & right.
Here is the response I received:
"There is no problem operating the Mustang Amps without speakers attached. I read the manual and the point they are trying to get across is that if you are using speakers it A: Has to be connected to either a stereo speaker cabinet or B: Two separate 8ohm speaker cabinets. This is because it is a true stereo amp and if you use only one speaker connected to one output it will not sound right and the effects will not work. It is a solid state amp and is not affected by not having a speaker load on it."

G-One:

I guess its not unusual to get differing views on such things, and as I stated earlier, the specific Fender rep that I spoke with was apparently not a 'tech' per se, but it certainly makes you wonder who is running things down there (i.e., at Fender). Here's a set of three quotes from the Fender Customer Service rep that I spoke with (named 'Scott Marceau') in Scottsdale dated January 19, 2011 in reference to my question about speaker use with the Mustang V amplifier . . .

"Regarding point two, you are right that you can use either an 8 or 16 ohm cab on only one side. That being said, the head is pretty loud, so you want the speaker cab to be able to handle 100 watts of power.

For the last question, you do need to have speakers attached to the head at all times, even if you’re using the headphone jack as a line out. Using the headphone jack as a line out might not sound the best because of an impedance mismatch between your amp and whatever you’re recording with, but it will do the job.

The transformer on your amplifier needs to see a load from the speakers on it, so that’s why you have to keep the cabinet plugged in at all times."

There ain't too many ways that a guy can misinterpret those three statements, so clearly, one of these two parties in wrong, and from what you've said here, I strongly suspect that its the latter (i.e., Scott Marceau).

Thanks for pursuing it further. I'm glad to learn that I can safely disconnect any and all speakers, and its no small revelation, since it makes it immensely easier to transport the amp and use it (with headphones) in differing locations without attached speakers!

Cheers

[g1]

Thanks for posting the responses you got from Fender. It is now clear the rep you spoke to mistook the Mustang V for a tube amp as he mentions the TRANSFORMER needing a load. Solid state amps do not have output transformers, so they don't need a load.
If this amp really needed a load connected, it would not sell alongside all the other brands of solid state amp heads that can be used with headphones alone. The sales reps would make sure the design got sent back to the drawing board.
The owners manual should be reworded with regard to speaker use but I doubt it will happen.

[Mango Moon]

G-One:

You're quite welcome and I too noticed the 'transformer' (vs. transistor) language in his response, so I suspect you're right - I doubt any changes to the manual will ever take place. By the way, its been a few years since I was up your way, but howz life north of Fargo these days? Spent a few years near Ste. Agathe in Manitoba back in the 80s . . . played some hockey on the frozen Red River most every night - sniped a few snowshoe'd hares in the stubblefields on the weekends. Treacherous wind and colder than liquid nitrogen, but good memories all around. I hope its still rural and picturesque up there.

Cheers

[g1]

"colder than liquid nitrogen", I like that! It'll freeze your warts clean off.
Still pretty rural, they're starting to worry about major flooding of the Red this spring. About half the continent is north of Fargo so I'm surprised you got it pretty close. I'm actually a few miles south of Miami but that just confuses things.
My mom used to tell me about some mexican mennonite ladies up here who didn't want to say they were from Mexico, so when someone would ask they would say they were from "south of Fargo". I got a real kick out of that so I decided to use it in reverse.

[Mango Moon]

About half the continent is north of Fargo

Ain't it the truth! Few people on this side seem to grasp just how vast the real estate is up there - its un-real! In addition to southern Manitoba, I spent a number of years in north central Montana, and I vividly recall the many mennonite/hutterite colonies scattered across the plain there. In fact, that's precisely where we'd get our monster (range-fed) turkeys and rhubarb wine from for Christmas supper. Too funny! Anyway, good talkin' with you. Stay warm and keep your powder dry up there! And slap a stray puck for me sometime!

[teemuk]

Solid state amps do not have output transformers, so they don't need a load.

There are several solid-state amplifiers that use output transformers. Granted they were more common in the 1950's and 1960's but even today - especially among guitar amps - there are still designs that try to mimic tube circuits and do so conveniently by using an output transformer.

It's a case-specific issue. You can't assume; just because 90% of generic SS amps do lack one it doesn't mean they all do so. Invalid assumptions can lead to situations where the amp says "poof" and releases the magic smoke.

[Mango Moon]

There are several solid-state amplifiers that use output transformers.

This presents continued cause for concern regarding safe use of the Fender Mustang V head specifically, and its simply gotta get resolved, yet I don't know how to proceed?!@#$%&*? There are going to be many other Mustang V (head) owners out there who are going to be potentially putting their amps at risk by using them without speakers attached, based on what appears to be inconsistent or erroneous information. Can anyone answer here . . . what is the truth?

1) We've got the Owners Manual saying that a pair of speakers must be attached at all times;

2) We've got a lone Fender Customer Service rep who has clearly stated that one or more speakers must be attached to the amp at all times, even when the headphone jack is in use;

3) We've got yet another Fender Customer service rep stating that it is completely unnecessary to attach one or more speakers.

Forgive my saying it, but "Good Grief"! Where does one go from here to get reliable information? Obviously the manufacturer isn't "reliable"! Do I need to literally disassemble this beast to visually inspect whether its got one or more output transformers? Seems absurd!

In the words of Seinfeld character George Costanza . . . "George is gettin' frustrated"!!!

[Jazz P Bass]

I think that last post is muddying the waters here.
No offense.
If this amp has output transformers, I will eat my hat.
It is also stereo.
That means two transformers.
Somehow I do not see this happening.
Not for the price of the amplifier.
It's a modeling amp.
150 watts.
It has a usb port.
These are the selling points of the amp.
Forget the speaker has to be plugged in issue.
Play it.

[Mango Moon]

I appreciate your views and I'll trust that you're correct on all scores here, but I respectfully submit that it wasn't the "last post" that "muddied" the waters. Rather, its the inconsistent, ill-trained Customer Service folks at Fender Instruments World Headquarters and the Fender contractor or Fender reps who wrote the official Owner's Manual, yeah? That's where the mud comes in.

[J M Fahey]

I delayed my answer because I searched a little, here and there.
By the way, couldn't get the full User Manual, only brochures and similar light info.
The official Fender link you provided defines "voltage" as "array" and "wattage" as "array" too, whatever that means. UGH !!!
If that's the technical knowledge level Fender insists on or accepts, not only for sales reps but for user manual writers .... UGH!!! again.
Can only agree with jazzpbass:
given the price and what it is, there's no way there are output transformers *there*
They are expensive and can be justified if some designer finds their use important, either for sonic performance or practicity (multi-impedance), but this amp is a *modeler* , all sound are software made, and clearly states 8 ohms as the only acceptable impedance, so .... no transformers there.
It *might* have a Class D power chip, which *might* self destroy or overheat if unloaded, but i'mm sure they would tout their "futuristic/green/ecologic/efficient/groundbreaking/dolphin safe" digital amp if it were so.
The matching cabinet is stereo 8 ohms per side ; maybe their vague wording tries to force the user to buy it, for fear of burning it otherwise.
I also agree that nothing bad will happen if used without speakers.
Oh well.

[g1]

Teemuk: You are correct and I should have said almost all, rather than saying all. I didn't want to cloud the issue. As far as I know those rare SS amps with output transformers do not require a load and would not be damaged by running unloaded but please correct me if I'm wrong.
The point is what Jazz P was getting at. We are talking about an inexpensive modelling head with a USB port, and a headphone out that is competing with other SS gear at a low price point. No where is the head itself labelled "do not operate without speakers connected", no where does the manual state the warranty will be voided or that damage will occur if operated without a load.
I will up the ante here and say if it has output transformers, I'll eat three hats! (hat-trick?) http://music-electronics-forum.com/i...ilies/wink.png
Mango, if you really want to pursue this, talk to the dealer you bought it from and ask them to verify with their Fender sales rep. I've got $20 that says you are fine to run this amp with no speakers.

[Mango Moon]

Thanks JM!

Yup, there's no question that they need some work down there at Fender, at least regarding this particular line of product, and what you've said about transformers being expensive, etc., makes pertfect sense, so I'm going to move ahead and operate on the principle that no speakers are required for this hummer.

Case solved! Thanks to All for your various contributions.

[J1592]

I don't have one of these but based on my experience with other modeling amps, I'd wager the following clarifications are accurate:

1) It's perfectly fine to run with no speakers attached. As someone already said, it's likely that CS rep was unaware of the technical differences from their tube amps (and apparently unaware that in stereo tube amps you need a load on each side!). The fact that it was the same guy that said it's okay to run only one side reinforces this theory because I can't personally think of any stereo amplifier designs in which it would for some reason be okay to run one side unloaded.

2) While the statement that stereo effects won't sound right with one speaker is true, that doesn't mean you need to connect both sides to avoid damage. It should function okay, if not sound quite right, with one side connected.

[km6xz]

Which 10% of those currently available solid state guitar amps use output transformers? Ok, that would require listing 100 or more, so how about 1?
My 2105 Macs used autoformers but that was 45 years ago. I surely would not want to be accused of "invalid assumptions".

[J M Fahey]

Some Peaveys used autoformers but that was some 20 years ago; anyway less than your 45
I have used some in my "it looks like a tube amp"heads, mainly to provide the 4/8/16 ohms jacks some customers expect.
Really I provide 2/4/8 , being more useful in my situation. I have one of them on my bench, in case some customer got "creative" with impedance; but *could* provide 4/8/16 easily if needed.