Load Box Attenuator for Ampeg V4B

[agedhorse]

Thanks for weighing in - good to know, will definitely look into this more - however I am pretty certain than unless you are running the V4B absolutely full tilt, the Captor should be fine with this.

It's good to learn what the terminology means and the math behind it, it helps to clarify the information being presented.

 

[TomB]

130V, I don’t think so…

I meant to write watts, which now appears equally wrong. I used AI to check my memory. AI (below) and my memory scored roughly equally on this one. …fail. Thanks all.

AI Overview:
“When an Ampeg V-4B is pushed hard enough to enter output-stage distortion and power-tube saturation, it is entirely capable of producing 130 watts or more of output power.”

 

[agedhorse]

I meant to write watts, which now appears equally wrong. I used AI to check my memory. AI (below) and my memory scored roughly equally on this one. …fail. Thanks all.

AI Overview:
“When an Ampeg V-4B is pushed hard enough to enter output-stage distortion and power-tube saturation, it is entirely capable of producing 130 watts or more of output power.”

Ahhh, that makes more sense.

If you push the amp hard enough into clipping, it may very well produce 130 watts. It will also be quite hard on the power tubes.

 

[TomB]

Ahhh, that makes more sense.

If you push the amp hard enough into clipping, it may very well produce 130 watts. It will also be quite hard on the power tubes.

From the OP:

“Does anyone have recommendations for a load box attenuator that can handle an Ampeg V4B cranked? My understanding is that the common 100W-rated units risk damage from output spikes with the amp all the way up.”

Resting my case…

 

[agedhorse]

From the OP:

“Does anyone have recommendations for a load box attenuator that can handle an Ampeg V4B cranked? My understanding is that the common 100W-rated units risk damage from output spikes with the amp all the way up.”

Resting my case…

If "cranked", then I would consider the 130 watts RMS as a good working value PLUS the reduction in duty cycle/crest factor due to the effective compression that will be occurring (which will increase the effective power delivered over time). The derating factors will be known only by the manufacturers of these load boxes.

 

[tech21nyc]

There are a lot of misconceptions about using tube amps with attenuators. Check out the video below by Steve Fryette who has been designing tube amps for decades and he also makes the Power Station attenuator. I'm a lead guitarist and have been using attenuators for decades with many 100 watt amps. The first things to keep in mind when driving any tube amp into clipping for extended periods of time are the following:

The amp should be in perfect working order. (If it's an older amp a technician should service the amp to make sure that it is.) Matched and properly biased tubes, impedance on the amp and speaker matched correctly, properly working speaker cab and a good quality "speaker cable." The easiest way to blow an amp is to use an instrument cable instead of a speaker cable.

With all that out of the way keep in mind that driving the amp continuously into clipping will wear out the tubes faster. Using an attenuator will make it much easier to do that because the ability to generate "output stage distortion" no longer requires high volume levels to achieve that. Output tubes are expensive so keep that in mind.

 

[sumeursault]

There are a lot of misconceptions about using tube amps with attenuators. Check out the video below by Steve Fryette who has been designing tube amps for decades and he also makes the Power Station attenuator. I'm a lead guitarist and have been using attenuators for decades with many 100 watt amps. The first things to keep in mind when driving any tube amp into clipping for extended periods of time are the following:

The amp should be in perfect working order. (If it's an older amp a technician should service the amp to make sure that it is.) Matched and properly biased tubes, impedance on the amp and speaker matched correctly, properly working speaker cab and a good quality "speaker cable." The easiest way to blow an amp is to use an instrument cable instead of a speaker cable.

With all that out of the way keep in mind that driving the amp continuously into clipping will wear out the tubes faster. Using an attenuator will make it much easier to do that because the ability to generate "output stage distortion" no longer requires high volume levels to achieve that. Output tubes are expensive so keep that in mind.

Very informative. I watched the whole thing. Thank you!

 

[6thplanet]

Mr Fryette definitely knows his way around guitar tube amps, surprised he never ventured into bass amps.

 

[sumeursault]

Mr Fryette definitely knows his way around guitar tube amps, surprised he never ventured into bass amps.

I'd guess much lower demand

 

[sumeursault]

Anyone have experience using the Fryette PS-2A with bass amps?

 

[agedhorse]

Anyone have experience using the Fryette PS-2A with bass amps?

Depends on the size of the amp.

 

[sumeursault]

Depends on the size of the amp.

V4B

 

[agedhorse]

Ok, so figure the load portion needs to handle about 125 watts rms, maybe a little more if driven very hard.

 

[bknop]

Someone already beat me to it, I'd check out the Fryette power station, it's the only guitar attenuator that I've heard that sounded correct, probably due to driving the speaker directly from the Fryette's tube amp. Unfortunately I do not know the performance with a bass. They work fine with the 100watt guitar heads, so I don't think power handling will be an issue. I did find tests of the reactive load on a Fryette unit. The simulated impedance will be off on the low end. The Fryette units has the impedance peak between 100 and 200 hz. A sealed bass cab would likely have an impedance peak in the 60-90 hz range, and a ported box will have two peaks one below the port tuning and one above.
Link to the other forum.

Fryette Power Station users... Give me your thoughts

I'm still running the original tubes in my PS1 which was from the very first batch of them

www.rig-talk.com

 

[sumeursault]

Someone already beat me to it, I'd check out the Fryette power station, it's the only guitar attenuator that I've heard that sounded correct, probably due to driving the speaker directly from the Fryette's tube amp. Unfortunately I do not know the performance with a bass. They work fine with the 100watt guitar heads, so I don't think power handling will be an issue. I did find tests of the reactive load on a Fryette unit. The simulated impedance will be off on the low end. The Fryette units has the impedance peak between 100 and 200 hz. A sealed bass cab would likely have an impedance peak in the 60-90 hz range, and a ported box will have two peaks one below the port tuning and one above.
Link to the other forum.

Fryette Power Station users... Give me your thoughts

I'm still running the original tubes in my PS1 which was from the very first batch of them

www.rig-talk.com

Ah, yeah that makes sense. I wonder if it would sound better with both of the reactive switches set to “flat”.