amp builders: switching off power section in an amp head

[duodecim]

To those that have some more than my rather minimal knowledge of electric circuits and tube schematics: would it be trivial to mod a head so only the preamp gets powered up? Since there must be some sort of converter to separate the low-power preamp from the power amp, it must be possible to add a switch that interrupts the power to the power amp (perhaps even by just rewiring the standby switch) but still supplies power to the preamp.

This way one wouldn't need a power soak to just slave the preamp into a recording interface or different power amp.

What I'm hoping to achieve is to slave a 100W head's preamp into a tiny (1W, 5W, ...) power amp without actually powering up the power section. It'd be cool to run a Soldano/Marshall/Diezel/ENGL... preamp into a low wattage power amp such as in the Blackstar (without all going rack gear).

Are there actually any tiny 1W/5W power amps (like a Blackstar HT-5 or Egnater Rebel)?

 

[titanamps]

this would be pretty easy to accomplish, and i can think of at least two different ways to do it.

that said, in most amps all you have to do is put the master volume on zero. i'd leave a cab plugged in just in case, though.

also, in some amps when you insert a plug in the FX send jack, it interrupts the signal going to the power section.

 

[duodecim]

Thanks. But how much does having the master volume on zero wear out the power tubes – having them on but pretty much idle?

I guess I'm just surprised that with all that talk all over the internet about power soaks and fake loads, nobody has released an amp yet where you can simply switch off the power section entirely.

Amps like that tiny Blackstar got me thinking about miniature power amps for practice... At low volume, a true 5W tube power section might sound better than a 100/200/... Watt section even when the amp has a decent master volume.

How's that 3 channel Titan coming along?

 

[RockNRollBabyHead]

The Marshall JVM and most Fryette(VHT) amps have that from the factory along with several other amps.

 

[Death by Uberschall]

Pull the HT fuse.

 

[duesentrieb]

The easiest way is to lift the grounds of the powertubes.
Thats a "standby" version some companies indeed are using, which keeps the preamp under voltage (pulling the HT fuse lifts the whole B+ of course and won't help you).

 

[Death by Uberschall]

The easiest way is to lift the grounds of the powertubes.
Thats a "standby" version some companies indeed are using, which keeps the preamp under voltage (pulling the HT fuse lifts the whole B+ of course and won't help you).

In fact most pre-amps are on all the time, so leaving the amp on stand-by is probably all you need to do.

 

[Shark Diver]

I guess I'm just surprised that with all that talk all over the internet about power soaks and fake loads, nobody has released an amp yet where you can simply switch off the power section entirely.
/quote]


But it's not the same thing. You lose the power tube warmth/distortion if you don't use it. So, a "power soak" is giving you more than what the preamp is. How much it matters is up to you.

 

[titanamps]

Thanks. But how much does having the master volume on zero wear out the power tubes – having them on but pretty much idle?

I guess I'm just surprised that with all that talk all over the internet about power soaks and fake loads, nobody has released an amp yet where you can simply switch off the power section entirely.

Amps like that tiny Blackstar got me thinking about miniature power amps for practice... At low volume, a true 5W tube power section might sound better than a 100/200/... Watt section even when the amp has a decent master volume.

How's that 3 channel Titan coming along?

if power tube life is an issue for you, you can just pull them. it's something of a PITA, but not the end of the world.

as for all the talk about power soaks, well....we gotta talk about SOMETHING people want the sound of a cranked amp but at non eviction levels. i'm of the opinion that they're chasing their tails (for a variety of reasons), but it's just my opinion.

the 3 channel is in the works, and that's about all i can say about it right now.

 

[Shark Diver]

as for all the talk about power soaks, well....we gotta talk about SOMETHING people want the sound of a cranked amp but at non eviction levels. i'm of the opinion that they're chasing their tails (for a variety of reasons), but it's just my opinion.

Man, I hope not. I get my Faustine Phantom this week, hoping it works as advertised.

 

[titanamps]

there's two things that are going to hinder getting that "cranked amp" tone at low volume:

1. speaker involvement. the only way to get the sound of a pushed speaker is to push it.

2. munson effect. humans perceive music that is louder as sounding better. this has a lot to do with the insane mastering techniques that are used today....it's a literal volume war.

will it allow you to get more power tube compression/distortion at lower volumes? sure. will it make you as happy in the pants? not a chance.

old gear heads have heard the phrase "there's no replacement for displacement" thousands of times. the same could be said of volume.

 

[Code001]

old gear heads have heard the phrase "there's no replacement for displacement" thousands of times.

No, but there is such a thing as forced induction.

 

[titanamps]

old gear heads have heard the phrase "there's no replacement for displacement" thousands of times.

No, but there is such a thing as forced induction.

yes, but what happens when you combine adequate forced induction with more displacement?

i wanted kinda back up a little bit on that pulling the power tubes thing. it won't hurt anything, but the plate voltages on your preamp tubes will be different/higher. this will make the preamp section sound different.

just a CYA thing

 

[duodecim]

But it's not the same thing. You lose the power tube warmth/distortion if you don't use it. So, a "power soak" is giving you more than what the preamp is. How much it matters is up to you.

Ofcourse, the mean reason I want to switch off a 100W power section is to slave the preamp into a 5W power section. I can get a decent practice TV-level sound out of one of those small tube amps like Blackstar and Tiny Terror, but most 100W/200W amps don't sound good enough at that volume even for practice. Such low wattage won't sound like 100W cranked to the max, but better than that 100W section at TV volume...

 

[rsm]

A good reason for having separate preamps and power amps IMO.

I went to rack gear in the early '90s, and had a mix of SS, tube, and hybrid preamps and amps. After awhile either I got used to it, or was able to dial in tones that worked for me using preamps (SS, Tube, hybrid) and SS power amps. Either way, I got away from amp heads / combos that combined the preamp and power amp sections, and away from tube power sections.

All the preamps I have now, I run direct to PA using speaker emulation / simulation: no guitar power amp, no guitar speaker cabs. I have a Vox AC4 too; though it isn't as versatile, it does what I need it to do. Very satisfied with my set-up these days.