Studio 5 Watt Mode

[FrostyTheSnake]

Anyone have any technical knowledge regarding what happens in a studio amp when used in 5 watt mode? Specifically the SC20H. Mine sounds better in 5 watt mode? More spongy and less harsh. Also feels more saturated. More brittle and toppy in 20 watt mode. Everything I’ve read says 5 watt mode shouldn’t sound very good compared to 20?

This is through a 1960BV at bedroom practice levels via attenuation.

Makes me think I have a duff EL34 if one is switched off for 5 watt mode. 20 watt mode doesn’t sound “broken” just doesn’t have the same feel as 5 watt. Maybe it’s perceived volume and the difficulty that comes with high volume sat next to a 4/12. It’s a balance between good tone and deaf ears. 5 watt however is fantastic practice volume.

Any input would be fantastic.

 

[PelliX]

Mine sounds better in 5 watt mode? More spongy and less harsh. Also feels more saturated. More brittle and toppy in 20 watt mode. Everything I’ve read says 5 watt mode shouldn’t sound very good compared to 20?

I agree that some things can sound just as good or even a little better in the room in the low power mode. Recorded, this 'advantage' more or less disappears, but it's more compressed with less headroom and thus a bit 'easier to tame'. Brittle and toppy in full power? I can't say I've noticed that, though.

This is through a 1960BV at bedroom practice levels via attenuation.

In that configuration you're probably hardly moving any of the speakers, so that's a factor. Depending on the attenuation the sound can become a bit anemic and dull.

Makes me think I have a duff EL34 if one is switched off for 5 watt mode.

That's not how it works; they're both still operating in low power mode, just at lower voltages.

20 watt mode doesn’t sound “broken” just doesn’t have the same feel as 5 watt. Maybe it’s perceived volume and the difficulty that comes with high volume sat next to a 4/12. It’s a balance between good tone and deaf ears. 5 watt however is fantastic practice volume.

In full power mode, perhaps back the Presence off a bit?

 

[FrostyTheSnake]

I agree that some things can sound just as good or even a little better in the room in the low power mode. Recorded, this 'advantage' more or less disappears, but it's more compressed with less headroom and thus a bit 'easier to tame'. Brittle and toppy in full power? I can't say I've noticed that, though.



In that configuration you're probably hardly moving any of the speakers, so that's a factor. Depending on the attenuation the sound can become a bit anemic and dull.



That's not how it works; they're both still operating in low power mode, just at lower voltages.



In full power mode, perhaps back the Presence off a bit?

Thanks for the input great to know both tubes are working in 5 watt mode.

I think I’ll put it down to a roaring 4/12 in 20 watt mode is not always the easiest to practice with haha 5 watt is great practice level.

 

[vivanchenko]

The power transformer has two power supply windings, one for the higher power mode (higher voltage) and another one for the low power mode (low voltage). The amp also has 2 rectifiers, one for each winding. As a result, you get two B+ circuits, one is about 200 V and another one is about 260V (if memory serves me right). When you switch power modes you switch between 2 B+ circuits.

 

[FrostyTheSnake]

The power transformer has two power supply windings, one for higher power mode (higher voltage) and another one for the low power mode (low voltage). The amp also has 2 rectifiers, one for each winding. As a result, you get two B+ circuits, one is about 200 V and another one is about 260V (if memory serves me right). When you switch power you switch between 2 B+ circuits.

wow thank you!

 

[vivanchenko]

You are welcome.

 

[FrostyTheSnake]

Been playing with the 5 watt mode more. I must say it’s really good. Feels more responsive and less harsh AND less compressed. Anyone know any technical reason for this?

Old man noodling :

 

[21fret]

I don't have a studio amp, but aren't you guys discussing wattage and not voltage?

 

[FrostyTheSnake]

I don't have a studio amp, but aren't you guys discussing wattage and not voltage?

Indeed 20 watt amp you can also run in 5 watt mode

 

[RLW59]

I don't have a studio amp, but aren't you guys discussing wattage and not voltage?

Yes, but reducing the voltage going to the tubes is how they reduce the wattage that comes out of the tubes.

 

[Creach]

In 5W only the phase inverter and power valve are switched to lower b+ voltage (transformer tap) around 260v to 160v.

As their is less of load on the higher B+ the voltage on the preamp increase, around 230v to 260v.

So the switch affect power amp and preamp, it made the amp reacting differently.

 

[21fret]

Isn't that plate voltage?
(also cathode biased amp circuits)
seemingly things being discussed in variac territory.)

 

[RLW59]

Isn't that plate voltage?
(also cathode biased amp circuits)
seemingly things being discussed in variac territory.)

Yes, the full-power plate voltage to the power tubes is very low in full-power mode, and even lower in low-power mode, to 'trick" a pair of EL34's into producing only 20/5 watts. (Plus cathode bias to help reduce efficiency.)

Variac cuts  all the voltages, not just the power tube plate voltages. If you took a regular 50 watt amp and set a variac low enough to get only 260 volts on the output tube plates, you'd also reduce the voltages to the preamp tubes, so the preamp wouldn't sound the same.

But you wouldn't have to worry about how bad the preamp would sound, because the heater filaments wouldn't get hot enough for the amp to function.

You can think of the Marshall power reduction scheme as an internal variac that only affects the output tube plate voltage.

 

[FrostyTheSnake]

Thanks so much, that’s really useful stuff! Does that explain why it feels more spongy/less compressed? Or am I crazy?

 

[marshallmellowed]

Thanks so much, that’s really useful stuff! Does that explain why it feels more spongy/less compressed? Or am I crazy?

In my world, more "spongy" is more "compressed". Not sure that would be enough to classify you as "crazy", but maybe?

 

[FrostyTheSnake]

In my world, more "spongy" is more "compressed". Not sure that would be enough to classify you as "crazy", but maybe?

I’ll take it

 

[Sustainium]

Been playing with the 5 watt mode more. I must say it’s really good. Feels more responsive and less harsh AND less compressed. Anyone know any technical reason for this?

Old man noodling :

That was some wicked playing, I don’t think “old man noodling” quite fits your style. Maybe more like “Dude does LP justice!”

 

[FrostyTheSnake]

That was some wicked playing, I don’t think “old man noodling” quite fits your style. Maybe more like “Dude does LP justice!”

Too kind

 

[paul-e-mann]

I've been using 5 watt mode at home exclusively, just discovered the low input too, even quieter and sounds great!

 

[DirtySteve]

I've been using 5 watt mode at home exclusively, just discovered the low input too, even quieter and sounds great!

I am also using the 5 watt mode with my head, I think it sounds/feels better. When I had my combo I liked it better in 20 watt mode so that's weird.

I like the low input too, I think it's great and doesn't get enough love on the forum. There are great clean tones to be had and low gain stuff with an OD is really nice, plus I like a fuzz sometimes and it sounds way better on the low input.