Rocker 32, bypassing the pre-amp

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samplehead
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Rocker 32, bypassing the pre-amp

Post by samplehead » Fri Jun 22, 2018 9:24 am

Hi,

I'm using a Rocker 32 purely as a stereo tube power amp and speaker cabinet. That is, I plug direct in to the Effects loop RETURNS.

It sounds fantastic. I'm absolutely stoked with this as portable solution for my needs. HOWEVER, I've notice two things that I'm not sure if they're by design or not...

1. There's NO master volume control. It turns out that the top panel volume controls are both pre-amp channel volume only. I guess this means that if you were using the preamp then the effects loop signal level would always be subject to the channel volume, no master volume. Ok, I can live with this, EXCEPT THAT...

2. The Half power switch (15W vs 30W), also has ABSOLUTELY NO EFFECT on the volume when running direct into the power amp. This I consider a bad thing. I really expected the half power switch to disengage 2 of EL84 output tubes?

Would love to hear your feedback on this.

Cheers
Pedro

bclaire
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Re: Rocker 32, bypassing the pre-amp

Post by bclaire » Fri Jun 22, 2018 11:37 am

Welcome to the forum.

Seems like you're using the amp for a purpose for which it wasn't designed - so I'm not sure that the half power "not working" is an actual bad thing. The difference in volume between 15 and 30 in the way you're using it might not even be perceptible. What are you using it for exactly? I'm not clear what you are plugging into it.

Les Paul Lover
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Re: Rocker 32, bypassing the pre-amp

Post by Les Paul Lover » Fri Jun 22, 2018 3:13 pm

For the natural channel, I would expect there to be no master volume - there's none. The volume control is a preamp gain control.

As for the dirty channel... It really depends on where the FX loop is located.

But as Billy said, you aren't using the amp for its intended purpose, so it isn't surprising it doesn't necessarily work how you'd want it to.
Ant

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samplehead
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Re: Rocker 32, bypassing the pre-amp

Post by samplehead » Fri Jun 22, 2018 11:47 pm

Thanks for the replies.

It's not uncommon to use any amp in this fashion these days. i.e. to plug pre-amp pedals straight into the power amp section.

I'm totally cool with there not being a master volume. The amp doesn't have a master volume control, only channel volume controls.

But surely the half power switch is meant to actually disengage 2 of the 4 output tubes? As far as I know that's how every tube amp ever built (that offers a half the watts feature) works?

Can anyone from Orange chip in on this question?

Thanks,
Pedro

fiveightandten
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Re: Rocker 32, bypassing the pre-amp

Post by fiveightandten » Sat Jun 23, 2018 1:50 am

Have you verified with a DMM that the half power switch is not doing anything? If so, than the amp is malfunctioning and you should take it back. Though, bear in mind that cutting the power in half does little to drop the volume in most situations. If you are pushing the amp hard, you will notice the EL-84's break up earlier at half power. But the volume doesn't drop considerably.

If you are nowhere near the full output of the amp, you will indeed have no perceptible change from full to half power. This isn't specific to the Rocker 32, it's the case with any amp that has a half power switch. I have a Hi-Tone HT30 head, and when I put it on 15W it's still deafeningly loud! Haha. It's cutting out 2 tubes, and I've verified that with my meter.

FYI, there are other ways to do a "half power" switch. Some manufacturer's will make this a triode mode switch, or a switch the lowers the B+ voltage, or a combination of both. There are other methods as well. Though, taking out 2 tubes is what most people want, is the least complex, and changes the tone the least. Unfortunately, it just doesn't yield the large volume change that many people are expecting.

-Nick
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samplehead
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Re: Rocker 32, bypassing the pre-amp

Post by samplehead » Sat Jun 23, 2018 3:33 am

Thanks Nick. I don't have a DMM unfortunately.

I'm not sure how close I'm running to the full output, but it's definitely not low volume, so I'd wager that I'm pretty close to full volume - but I don't hear any difference in break-up nor volume switching between half and full power, it really is identical to my ears.

One thought I had is that maybe I need to wait longer for additional tubes to fire up or vice versa for them to fade out before switching back and forth. Seems unlikely though.

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Re: Rocker 32, bypassing the pre-amp

Post by bclaire » Sat Jun 23, 2018 1:40 pm

Here's a test to do:

Plug a guitar into the amp - put everything on ten; and then switch to half power and hear what the difference is. Now do it at a lower volume setting...

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Re: Rocker 32, bypassing the pre-amp

Post by fiveightandten » Sat Jun 23, 2018 7:09 pm

samplehead wrote:
Sat Jun 23, 2018 3:33 am
Thanks Nick. I don't have a DMM unfortunately.

I'm not sure how close I'm running to the full output, but it's definitely not low volume, so I'd wager that I'm pretty close to full volume - but I don't hear any difference in break-up nor volume switching between half and full power, it really is identical to my ears.

One thought I had is that maybe I need to wait longer for additional tubes to fire up or vice versa for them to fade out before switching back and forth. Seems unlikely though.
The way the Standby/Full/Half power switch is wired, it would be extremely unlikely that you're getting sound and it's not doing anything. I'm guessing that you're just nowhere near the full power of the amp, so you're not noticing the difference, as it is rather subtle. This amp is unique in that it's two 15W amps running at once. So it doesn't have the same headroom as a 30W amp. You're really going from two 15W power sections to two 7W power sections.

Even 15W is deafeningly loud running full bore. I play with a hard hitting drummer and I get my Vox AC-15 up to about 4 (on the master) before I'm blowing the rest of the band out of the room. It's the same with my Hi-Tone on 15W mode.

Anyways, in the interest of solving your problem; it seems that you want some sort of volume control. You can easily have a tech make you a little box that does this. 1 dual ganged pot in an enclosure, and 4 jacks (in and out for each side of your stereo setup). You would just make this the last thing in line on your board before the sends to the R32. It would probably cost about $20 in parts.

-Nick
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'71 GRO100 || '96 OR-80 || AD30 || '64 AC-50 || AC-30TBX || Hiwatt DR504 || HI-TONE HT30
LP Standard || LP Studio || LP Custom Lite || Ric 620 || Ric 360 || MIA Tele || SG 61 RI

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