Stewart World 2.1 crapping the bed?

[MassacreBass]

My Stewart power amp suddenly started acting up at practice tonight. With the volume knob on the A channel set anywhere past the 12 o'clock position (it's usually at 3 o'clock) causes the signal to break up badly. I've never had this issue before. I tried it with two different preamps and the problem persists. I'm running it mono into a Trace Elliot 4x10 cab.

 

[agedhorse]

Try taking it out of bridge mode and test each separately in stereo mode.

It's also possible that there is a defect in the speaker or speaker cable.

 

[MassacreBass]

I tried it with my Carvin 4x10 and a different cable. No bueno.

 

[agedhorse]

Did you try it in stereo mode?

 

[MassacreBass]

Did you try it in stereo mode?

Your original theory was correct! Tried a third cable that was brand new and it fixed the problem. Thanks!

 

[BassmanPaul]

If by running in bridge you have damaged two speaker cabinets perhaps you should change how you use the amp!

 

[agedhorse]

If by running in bridge you have damaged two speaker cabinets perhaps you should change how you use the amp!

It was bad speaker cables. In bridge mode, an intermittent short circuit can, depending on how the VI protection is implemented, result in unpredictable behaviors (including catastrophic destruction) by some amps. It's one of the negatives of bridged operation.

 

[Ken Morgan]

I’ve got the same Stewart amp..and their service people tell me it’s just fine to run only one channel on the amp in stereo mode. If you don’t need the full 1200 available watts in bridge, this might help in the future

 

[agedhorse]

I’ve got the same Stewart amp..and their service people tell me it’s just fine to run only one channel on the amp in stereo mode. If you don’t need the full 1200 available watts in bridge, this might help in the future

Correct.

 

[MassacreBass]

If by running in bridge you have damaged two speaker cabinets perhaps you should change how you use the amp!

This is totally incorrect, but thanks for your input.

 

[agedhorse]

This is totally incorrect, but thanks for your input.

I think he misread "cables" for "cabinets".

Though, if you have 2 bad cables, you might want to find a better quality cable or take better care of them.

 

[MassacreBass]

I think he misread "cables" for "cabinets".

Though, if you have 2 bad cables, you might want to find a better quality cable or take better care of them.

Yeah, after a gig, we are usually in a hurry to get off stage so the next band can get their gear set up. Cables generally get shoved in bags with little regard to the damage that may occur.

 

[agedhorse]

Just beware that a damaged cable can cause costly damage to an amp.

 

[MassacreBass]

Just beware that a damaged cable can cause costly damage to an amp.

I'll be more aware of this in the future.

 

[BassmanPaul]

This is totally incorrect, but thanks for your input.

I misunderstood. Sorry.

 

[steelbed45]

I misunderstood. Sorry.

No need to be sorry. TB knows your stance on bridged amps.

 

[mexicanyella]

If I may be permitted a minor detour here...I just bought an old Crown MicroTech 600 power amp. It can power my 4-ohm cab with 750 watts on bridge mono, or a little less (660, maybe?) in something called parallel mono.

In bridge you connect to the two red posts only. In parallel you jumper the two reds together and then connect your speaker cable to the A channel’s black and red terminals.

Is parallel mono safer, or easier on the amp? Do other stereo power amps offer that feature? I’d not heard of it before.

 

[Wasnex]

If I may be permitted a minor detour here...I just bought an old Crown MicroTech 600 power amp. It can power my 4-ohm cab with 750 watts on bridge mono, or a little less (660, maybe?) in something called parallel mono.

In bridge you connect to the two red posts only. In parallel you jumper the two reds together and then connect your speaker cable to the A channel’s black and red terminals.

Is parallel mono safer, or easier on the amp? Do other stereo power amps offer that feature? I’d not heard of it before.

I have never seen parallel mono on anything but a Crown amp. You choose bridge mono or parallel mono based on the impedance you need to drive.

The MT600 is rated for 4-16 ohms in bridge mode and 1-4 ohms in parallel mono mode. The power at 4 ohms in bridge mode is approximately the same as the power at 1 ohm in parallel mono mode.

 

[agedhorse]

I have never seen parallel mono on anything but a Crown amp. You choose bridge mono or parallel mono based on the impedance you need to drive.

The MT600 is rated for 4-16 ohms in bridge mode and 1-4 ohms in parallel mono mode. The power at 4 ohms in bridge mode is approximately the same as the power at 1 ohm in parallel mono mode.

Correct, the power delivered will be limited by the load's impedance.

 

[TomB]

I’ve got the same Stewart amp..and their service people tell me it’s just fine to run only one channel on the amp in stereo mode. If you don’t need the full 1200 available watts in bridge, this might help in the future

I had a World 1.6 - similar topology. Their tech told me the same thing, in fact, he suggested avoiding bridge mode if possible. So I did. Usually using one side was enough, but when needed you could run a 4-ohm load off each power amp from a single input, ~350 watts per side if I recall correctly (but it's been a while). In any case, that made for a LOT of headroom.