Output mod

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Re: Output mod

Post by Mosfet »

Bg wrote: Mon Oct 18, 2021 6:32 pm You are aware that dropping 100 watts to 50 watts won't reduce the volume much at all, you need to drop a 100 watt amp to 10 watts to get a half vol difference - its a logarithmic exponential curve. ( a factor 0f 10)

My bogner was still fucking loud on 7 watts.
100 watts -> 50 watts won’t cut the perceived volume by half but it will cut the intensity by half. Worth noting

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Re: Output mod

Post by Slowy »

Molly wrote: Mon Oct 18, 2021 8:37 pm
Slowy wrote: Mon Oct 18, 2021 8:26 pm
Thewilltopowerrock wrote: Mon Oct 18, 2021 6:39 pm The 100-50w was just an example. In reality I’m wondering more like start with something in the 20-40w range and drop down low, maybe even 5w.

Slowly, primarily decrease volume since bulk of playing is bedroom etc.
Jeez mate, I play to 100+ people in a 5 piece band with either 12 or 30 watts; both work fine. You must have an impressive bedroom!
My Carr has a max of 8w. I've wondered if it'd keep up with a drum kit.
If I have such a thing as a remaining dream amp, it's probably your Carr.
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Re: Output mod

Post by jeremyb »

Look into the VVR developed by hall amplification or the VCB (cathode biased version) by ampmaker.com :-)
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Re: Output mod

Post by NippleWrestler »

You can pull 2 power tubes from a 100w amp to get 50w output. But as mentioned you won't hear much change in volume, but you'll get less headroom and less thickness in the low end. Same goes for 20w too, you'll still have a shit ton of volume but less headroom and a narrower frequency range (which might matter to you).

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Re: Output mod

Post by MattAnt »

Kris wrote: Mon Oct 18, 2021 8:45 pm I don't understand anyone who says under 50w tube is enough for a jam situation with acoustic drums. Unless I just happen to have struck a homicidal maniac percussionist every band I've been in.
Which is actually likey....pitfalls of the genre I guess
Your drummer must be insane, or more likely, your low wattage amps on the quiet side.

I have 15w - 30w amps that I can barely turn on they are so loud, at full boar the are window shaking. Then I have 15w amps that are much more modest in volume and wouldn't keep up with a loud drummer.
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Re: Output mod

Post by olegmcnoleg »

NippleWrestler wrote: Tue Oct 19, 2021 8:43 am You can pull 2 power tubes from a 100w amp to get 50w output. But as mentioned you won't hear much change in volume, but you'll get less headroom and less thickness in the low end. Same goes for 20w too, you'll still have a shit ton of volume but less headroom and a narrower frequency range (which might matter to you).
This is by far the easiest option. But don't pull 3. And you need to be careful which tubes you pull You will also need to change the impedance setting for your speaker (usually, there is a switch round the back (or a different jack socket) to easily achieve this. Read more about it here: https://www.premierguitar.com/gear/revi ... duce-power

If you want the amp to be noticeably quieter, you will need a power soak/attenuator for the best results. You could also get a McPherson master vol modification (advertised on TM), which is cheaper, and built into your amp. But it will affect your tone more drastically. Or you could run your FX loop at a much lower volume (if you use one).



If all this advise fails, then as a last resort you could always try turning your amp down. :roll:

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Re: Output mod

Post by RectifiedAmps »

You can split output attenuation into to 2 categories: preamp and power amp.

Preamp scaling options:
- master volume mods (incl volume pedal in fx loop)
- lower gain preamp valves (12AX7 -> 12AY7/12AU7)
- Circuit mods (cathode bypass caps, voltage dividers)

Power amp scaling options:
- if you have four power valves, pull two. As mentioned, this doesn’t actually reduce volume much and it doubles the output impedance to the speaker
- attenuator. Probably the most ‘transparent’ option, but also the most expensive if you want a decent sounding reactive load
- Run power valves in triode mode. Again, not much reduction in output and the resulting tonal change is not pleasant (YMMV)
- Power scaling. Too many versions here to mention, but the ones that only affect the power amp and simultaneously adjust fixed biasing are the ‘best’. Scaling a 50w amp down to 5w will still not sound great, but it’s better than anything other than an attenuator.
- Speaker selection/reduction. Use a single, lower efficiency speaker and/or a smaler diameter (10” or 8”). Bass is usually the factor that needs attenuation the most in bedroom settings, so a 12” speaker is overkill at lower volumes.

I’m probably forgetting some other options, but these are certainly the most common ones. And remember that these various options can be combined to a greater effect. For example, pulling a pair of output tubes AND disconnecting a speaker is a good way to tame a Fender Twin (but not to bedroom levels).

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Re: Output mod

Post by Thewilltopowerrock »

Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.

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Re: Output mod

Post by Slowy »

olegmcnoleg wrote: Tue Oct 19, 2021 9:11 am
If all this advise fails, then as a last resort you could always try turning your amp down. :roll:
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Re: Output mod

Post by Slowy »

Thewilltopowerrock wrote: Tue Oct 19, 2021 9:53 am Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.
Mike, Alan, Rectified, Nipplewrestler? You're up guys.
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Re: Output mod

Post by RectifiedAmps »

Thewilltopowerrock wrote: Tue Oct 19, 2021 9:53 am Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.
The AC15HW changes the cathode biasing from cold to hot to achieve this (see below). You could implement it on any cathode biased amp I suppose, but again- halving wattage only gets you about 10% less output and in this case the tone of the power amp will be different (good or bad I can’t say).
D5E9D675-2A5C-44A3-9EE7-0CD2E8FE4422.png
D5E9D675-2A5C-44A3-9EE7-0CD2E8FE4422.png (326.11 KiB) Viewed 1693 times

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Re: Output mod

Post by MikeC »

Slowy wrote: Tue Oct 19, 2021 9:57 am
Thewilltopowerrock wrote: Tue Oct 19, 2021 9:53 am Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.
Mike, Alan, Rectified, Nipplewrestler? You're up guys.
Well it's a simple sounding question but it's not a simple answer! What amp specifically (my apologies if I missed it)?
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Re: Output mod

Post by Thewilltopowerrock »

RectifiedAmps wrote: Tue Oct 19, 2021 10:18 am
Thewilltopowerrock wrote: Tue Oct 19, 2021 9:53 am Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.
The AC15HW changes the cathode biasing from cold to hot to achieve this (see below). You could implement it on any cathode biased amp I suppose, but again- halving wattage only gets you about 10% less output and in this case the tone of the power amp will be different (good or bad I can’t say).
D5E9D675-2A5C-44A3-9EE7-0CD2E8FE4422.png
Thanks RA. I know it probably depends on the amp but is there much work in it?

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Re: Output mod

Post by Thewilltopowerrock »

MikeC wrote: Tue Oct 19, 2021 10:28 am
Slowy wrote: Tue Oct 19, 2021 9:57 am
Thewilltopowerrock wrote: Tue Oct 19, 2021 9:53 am Thanks everyone but I’m not sure my question has been answered 😬 so I’ll ask it another way:

The AC15HW (for example) is switchable between 15w and 7w. In principle, can you modify an amp to incorporate this feature? If so, how much of a process is it?

Please forget about specific outputs, pulling tubes, attenuators etc. I’m only curious about the above in principle.

Thanks.
Mike, Alan, Rectified, Nipplewrestler? You're up guys.
Well it's a simple sounding question but it's not a simple answer! What amp specifically (my apologies if I missed it)?
Would you like me to complicate the question for you? 😅

No specific amp, I’m merely asking in general terms about the feasibility of it. I know in real life there will be amp-specific considerations, but trying to avoid that at the moment.

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Re: Output mod

Post by MikeC »

Anything can be done (pretty much) with an unlimited budget.
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