No load OK, who knew!

[nutdog]

Originally Posted by scottfeldstein

Page 7 of the MB500 manual clearly says: "Delivers 500w into 4 Ohm loads. Lower impedances such as 8 Ohms or 16 Ohms and no load are acceptable."

I'm no electrical wiz, and it is what the manual says, but shouldn't this say "higher" impedances?

[hdracer]

Originally Posted by Primakurtz

Aye, there's the rub. Some tube amps do have an automatic load built in, so that you can unplug the speaker(s) without harm. The new Fenders feature this. Others?

Originally Posted by KJung

None that I am aware of. Again, that head seems like it was designed for studio work. I don't think (could be wrong) the 300 watt version has that feature.

The 300 does not have it.

On the 100T you can not just unplug the cab.
On the back of the amp there is a 3-way switch 25W-100W- Silent
The DI is great.

[DiabolusInMusic]

If the Bassman 100T still needs a load but can mute the speaker outputs that is how the super bassman 300 operates. Very useful feature but it still needs a load connected to not kill itself.

And yes OP, all SS heads can run just fine without a load, one of the many benefits of SS. I have gotten quite lazy in regards to ensuring my speakon cable is connected since switching to SS, thankfully I don't play to go back.

Viva la SS!

[KJung]

Originally Posted by nutdog

I'm no electrical wiz, and it is what the manual says, but shouldn't this say "higher" impedances?

+1 My guess is, whoever wrote that was thinking 'lower power' as a result of the higher impedance, and the 'lower' just got written/printed.

[Mr. Foxen]

Some SS amps have an output transformer, like the Jonas Hellborg rig.

Usually have amps have shorting output jacks, which means they don't die if no lead is plugged in, its not ideal, but it isn't death. Its a lead in to the jack and nothing on the other end that toasts things as it is then open circuit. A dead short on a valve amp is ok.

[BassmanPaul]

If an amp has an output transformer it should not be run without a load. That goes for tube OR SS. The vast majority of tube amps require a load to be present.

[JimmyM]

Originally Posted by Mr. Foxen

Some SS amps have an output transformer, like the Jonas Hellborg rig.

As far as I know, the Hellborg power amps are the only SS amps on the market currently that have an OT. And this doesn't go for the lower priced Hellborg amps...just the more expensive Hellborg power amp.

[Mr. Foxen]

There are a few old ones with OTs though, keep seeing them as makes them look like valve amps at a glance, with two transformers.

[ckdhaven]

Originally Posted by scottfeldstein

Page 7 of the MB500 manual clearly says: "Delivers 500w into 4 Ohm loads. Lower impedances such as 8 Ohms or 16 Ohms and no load are acceptable."

The 1001RB manual says the same thing...

However, there is no headphone jack..

This kind of ties to your other post about DI units.. I use my Radial Bassbone DI for headphone playing...

[skychief]

Originally Posted by scottfeldstein

Page 7 of the MB500 manual clearly says: "Delivers 500w into 4 Ohm loads. Lower impedances such as 8 Ohms or 16 Ohms and no load are acceptable."

Apparently, this is a misprint. Im surprised the proof-reader let this slip.

Anyway, it should read: HIGHER impedances such as 8 Ohms or 16 Ohms and no load are acceptable.

[BassmanPaul]

Originally Posted by Mr. Foxen

There are a few old ones with OTs though, keep seeing them as makes them look like valve amps at a glance, with two transformers.

I have worked on a lot of TOA commercial amps that have OPTs. Used for driving 70 volt lines. In re-purposing these amps for normal use I simply removed the transformers.

[Munjibunga]

Originally Posted by scottfeldstein

So I'm up late last night and I get an urge to noodle around. I usually run my pedal board into my mixer, my mixer into my headphones. But last night I thought maybe I'd just plug my headphones into my amp and play with my amp's EQ for a change.

Surely the MB500 had a headphone out. It did!

But when I played, my cabs still made noise. Not what I had in mind for a silent jam in the middle of the night. I consulted the amp's manual and to my surprise it says 4 Ohms, 8 Ohms and no load are all OK. That is, I can unplug both cabs from the amp and still run it. That way, I can get the headphones working but have nothing come out of the cabs.

Am I the only one who didn't know this was a thing, no load being OK?

On solid state amps (even with a tube preamp) no load is fine. Think about it - if an amp is rated for 4 ohms minimum, you can run acab a 4 ohms or any higher impedance ... 5.3 ohms, 8 ohms, 16 ohm, -> infinity ohms (no load). I didn't read the whole thread, so I'm probably the 20th person to say this. Think of it as constructive reinforcement.

[KJung]

Originally Posted by Munjibunga

On solid state amps (even with a tube preamp) no load is fine. Think about it - if an amp is rated for 4 ohms minimum, you can run acab a 4 ohms or any higher impedance ... 5.3 ohms, 8 ohms, 16 ohm, -> infinity ohms (no load). I didn't read the whole thread, so I'm probably the 20th person to say this. Think of it as constructive reinforcement.

Hey Munj. I'm going OT here, since this thread seems to have run its course. I know you dig your Heartrock. Sell that thing and get a Blue Soul. I'm pretty blown away by it (as a former Heart Rock owner). 2/3rds the size, 1/4 the weight, and IMO all the slam with better mid presence. Amazing box, and your new Fodera NEEDS that head.

Dan Lenard is the man at Luthiers Access Group. Nice deal on the head, bag, and 'rack handle' package.

Just sayin'

[walterw]

Originally Posted by Primakurtz

Aye, there's the rub. Some tube amps do have an automatic load built in, so that you can unplug the speaker(s) without harm. The new Fenders feature this. Others?

only tube amps that make a big deal of the feature and have specific instructions on how to do it!

so almost none

as for ss amps, yeah, they don't care. the higher the "ohms" the lower the "watts", so "infinite" ohms=zero watts.

[Downunderwonder]

Originally Posted by skychief

Apparently, this is a misprint. Im surprised the proof-reader let this slip.

Anyway, it should read: HIGHER impedances such as 8 Ohms or 16 Ohms and no load are acceptable.

Funny, I had read "lower" as "other", maybe the proof reader did too.

[megafiddle]

It is the output transformer that causes problems with tube amps operating
with no speaker connected. Virtually all tube amps use output transformers.
Virtually all solid state amps do not use them (there were some very early
solid state car radios, at least, that used output transformers).

The problem with an output transformer (tube amp) is that there will be a
high voltage "flyback" effect if no load is connected. The primary appears
as a high reactance with no load on the secondary. With a strong signal,
the primary voltage can rise high enough to arc over at the tube socket or
even worse in the transformer.

It should be mentioned that the tube amps that can safely operate without
a speaker connected do require a low impedance load just as any other tube
amp. It is just supplied automatically if the speaker is disconnected.
The solid state amp is safe to operate with no load because it is inherently
immune from open circuit loads. Not because it has any automatic internal
load switching.

[Munjibunga]

Originally Posted by KJung

Hey Munj. I'm going OT here, since this thread seems to have run its course. I know you dig your Heartrock. Sell that thing and get a Blue Soul. I'm pretty blown away by it (as a former Heart Rock owner). 2/3rds the size, 1/4 the weight, and IMO all the slam with better mid presence. Amazing box, and your new Fodera NEEDS that head.

Dan Lenard is the man at Luthiers Access Group. Nice deal on the head, bag, and 'rack handle' package.

Just sayin'

I sold my Heart Rock quite a while back - George at Bass San Diego has it now. He's a young man of sturdy stock, so he can lug it around. However, I still have my DB750/GS410 rig that is ostensibly for sale, but I'm not working too hard at selling it because it's the last vestige of lead sleds in my arsenal. I'm also selling my TCE RH750, so if one of those goes, I'll give some serious thought to the Blue Soul. I've been thinking about an Epifani 501 or Piccolo, but who knows.

[KJung]

Originally Posted by Munjibunga

I sold my Heart Rock quite a while back - George at Bass San Diego has it now. He's a young man of sturdy stock, so he can lug it around. However, I still have my DB750/GS410 rig that is ostensibly for sale, but I'm not working too hard at selling it because it's the last vestige of lead sleds in my arsenal. I'm also selling my TCE RH750, so if one of those goes, I'll give some serious thought to the Blue Soul. I've been thinking about an Epifani 501 or Piccolo, but who knows.

Not a fan of those Epi amps at all. Suffered through a few months with a 502. All low end, not much else.

The Blue Soul sounds significantly better than the old HeartRock, which lacked mid punch no matter how you dialed the knobs, and has 'HeartRock/DB750' thunder down low. Really exceptional if you dig that general Glock tone profile of big and warm down low, and super hi fi, crystal clear up top. Much improved from the old Soul/Heartrock, and 11 pounds is wonderful.