View Full Version : Marshall amp power reduction

04-29-2002, 05:59 PM
I've been trying to find a cheap way to lower the volume of my 100 watt marshall amps(with 4x12 cabs) when cranked up to 10(JCM800s seem to be WAY louder than normal 100watt amps). there are a lot of level reduction boxes that go between the amp and the cab, but are known for lowering the sound quality too. So an engineer friend told me that some guitarists use voltage reduction boxes (the ones that reduce the voltage coming from the wall), which are cheaper then the previous. It is supossed to work, but I'm wondering if it will damage my amps, and will I still get power tube saturation when I crank it up to 10??????

04-29-2002, 10:32 PM
There was a thing called the Power Soak that was built by Tom Shultz from the band Boston. It did the job very well. Don't know if it is still around though.

Zep Dude
04-30-2002, 12:14 AM
The THD hotplate can take the edge off without serious degradation. The more volume you take it down, the worse it sounds. Another trick is to wire a 4x12 cabinet so 2 of the speakers are out of phase. This will dramatically reduce the room volume because of the cancellation. It works if you're only close micing -and remember to flip the phase if you're micing several of the speakers. The sound will change a little. You won't get that huge Marshall bottom, but instead will get a more combo cabinet sound with a lighter bottom end.

Also, I've read that some people remove two of the tubes to cut the wattage in half. Be careful if you try this -it has to be the right two tubes and I'm not sure if their are long term consequences.

04-30-2002, 02:02 AM
I got a great 1971 100 W Super Lead Top.I took two of the power tubes out (every other, not two in a row). It works fine but it's still loud as hell, the difference is not that great although I think the sound is slightly better with all 4 tubes in.
In fact I've been using a POD for all my recording with PTLE so far.The Marshall impersonations are awesome.I use the real thing live for rock and roll gigs where it should be blasting images/icons/grin.gif images/icons/grin.gif


04-30-2002, 02:27 PM
The power bake takes the edge out of the amp, you still have power tube saturation. I've also pulled tubes out to make it 50 watts, but it sounds like a 50 watt cranked up, not like a 100 watt, which I think is different, plus also at 50watts the amp made a cracking sound very bad at half vulume. So seems like a Variac is the only way to go, for preserving the tone. I know a lot of the tone comes from the speaker distorting a little, but I'll still be loud, it's just that 100watts its too much, but the tone is amazing. well I'm happy to know that with a variac you can still have power tube saturation. I think they cost around $250-$350 like a power brake.

Andy Sneap
04-30-2002, 04:24 PM
Take the two outside tubes out(1 and 4) and run at 8 ohms into a 16 ohm cab, that apparently is the correct way to run at 50 watts, though this won't halve to output volume. Power soaks always colour the sound somewhat. 800's always sound the best I think, I have one standard one with a soldano mod and it's great. 6550 power amp mod works great in those also.

04-30-2002, 04:47 PM
When Marshall introduced the Master Volume in the mid 70-ies the idea was to get the 'sound' at lower levels.It never worked.

"We're close enough for jazz."
One trombone player to another, tuning up.

04-30-2002, 05:35 PM
get a pair of earplugs and cut at full volume.

05-01-2002, 05:44 PM
up to 10 ??? wow images/icons/grin.gif
most marshalls ive tried ended up being as loud as possible between 3.5 and 5 . all the stuff that happened when cranking up till "11" was just noise . especially using the vintage 30w speakers . i guess those load boxes were involved to bring the volume down to make those amps playeable in your " room " ... maybe i am wrong .
but if i watch the mic level of a sm57 micing a cabinet driven by a marshall up to 10 ... does that really make sense ??? only cool effect during this process " earthquake " images/icons/grin.gif

05-01-2002, 06:06 PM
The Variac should do the trick, though I'm not sure if you can get them new anymore. Another interesting thing about the Variac is that it can also overdrive the voltage level up to 130 volts. Gotta be careful overdriving circuits, though, because they were designed for 110 volts. I wouldn't overdrive anything new or expensive.

05-02-2002, 09:56 AM
The THD hotplate can take the edge off without serious degradation. The more volume you take it down, the worse it sounds.<font size="2" face="Verdana, Arial">Up to about -8db, I think the Hotplate sounds quite good. That's more than twice the volume reduction you'd get from pulling two output tubes.

Zep Dude
05-02-2002, 08:21 PM
The variac (which I've used) will take down the plate voltage -so it's like biasing your tubes way down -it will change the sound. Supposedly EVH reduced to 80watts for his brown sound. So you're not just taking everything down proportionaly like a fader on a console. I suppose you could then rebias the tubes at the lower plate voltage - I haven't tried this. You can get a used variac on ebay for probably $40 -make sure you get enough amps for your amp -at least a 5 or 6 amp unit, but your best off with a 10 or 15 amp unit. If I get a chance I'll try my variac again and report back here as to the percieved volume change.

05-02-2002, 08:58 PM
The variac reduces the headroom of the power tubes, so they aren't as loud, but they still distort and overload ...

05-03-2002, 10:54 PM
A 4x12 cab loaded with 25watt greenbacks
works wonders. breaks up just the right right way with a lot less input.

05-04-2002, 09:15 PM
Actually EVH ran his variac at 90v. He initially told everyone that he had it had 140v but later admitted he was just throwing people off on purpose. You can still get a great Tenma 10A variac at MCM Electronics for about $80

http://www.mcmelect ronics.com/Search/level_5.jhtml?PRODID=41656&SKUID=40900 (http://www.mcmelectronics.com/Search/level_5.jhtml?PRODID=41656&SKUID=40900)

However, a variac will only help your volume problem a little. By the way, it's very bad for your amp to pull two tubes. I wouldn't recommend it for more than a very short time.

Here's a great solution. Buy the HotPlate and set it to LOAD. You don't have to have it plugged into any speaker cabs. The HotPlate has a line-out with level adjustment. Your amp tone is now at line level. You can run it through effects, etc or dry. Doesn't matter. Then run that back into a dedicated power amp, and then into a speaker cab. You now have control of your volume and also have unmolested tone!! You can mic a speaker cone, but unless you crank it, you will be missing speaker distortion which does play a small role in great tone, but not that big of a deal. A good set-up is to run two cabs wet on each side for stereo effects, and then a completely dry cab in the middle. Sounds amazing too.

05-05-2002, 03:39 AM
Originally posted by 24-bit:
By the way, it's very bad for your amp to pull two tubes. I wouldn't recommend it for more than a very short time.
<font size="2" face="Verdana, Arial">I dunno, I did this (along with other people I know) without any problem.Tubes need to be replaced anyway after some time.
The problem is that it doesn't really solve the problem at hand- volume. Did EVH use a Variac to bring down his volume? I didn't notice.
I'd say either take this Marshall beast for what it is or use a smaller amp. Anyone remember James Marshall Hendrix ?


Doug Ring
05-09-2002, 08:20 AM
A good DIY solution is to get a bunch of high-wattage wire-wound or ceramic resistors and wire them in parallel. Say they were 10 watt capacity, you'd want 10 of them to dissipate 100 watts, and you want an 8 ohm load for the amp, so they need to be 80 ohms each... you can do the maths to suit other power ratings. This'll soak up some power and if you then connect an 8 ohm speaker as well and use the 4 ohm tap on the amp, you should get the cranked-up amp sound at a much lower volume. Or you could just take a line feed to your mixer from the other speaker socket via something like a 4k7 resistor in series and another in parallel, and not use the amp with a speaker.

After you've run the resistors for a while, slap a burger on them and it'll save you sending out for lunch.. images/icons/grin.gif

05-09-2002, 08:52 AM
Get a used Marshall studio 15. Thats a JCM800 made specifically for recording. It does the job really well.
If it doesn't cut it for you then i'm afraid that none of the other solutions will. The problem is that you can't really get the same impression of the sound produced on lower volume. So you have to accept that it really isn't gonna be the same as it used to be.

05-09-2002, 08:55 AM
Or build an isolation box. If it can take out 20-30 dB of the volume you'll have an acceptable volume.

The Chinese
05-09-2002, 10:21 AM
Get the Mesa/Boogie Rectifier Recording Preamp. Hands Down the Best direct to tape tone ever cfreated. Any sound you want. I seriously suggest getting this box. Clean/jazz/Rock/ Metal. Actually talks to ya.
-Todd A.

05-09-2002, 10:28 AM
Originally posted by Larsfrommars:
Get a used Marshall studio 15.<font size="2" face="Verdana, Arial">I did that.

But my Studio 15 still sounds rather "small" compared to my JCM800/4x12 combo.

Both are usable, It just depends on the sound you're going for.

The closed back 4x12's have a lot to do with the sound too.

05-09-2002, 10:31 AM
Originally posted by The Chinese:
Get the Mesa/Boogie Rectifier Recording Preamp. <font size="2" face="Verdana, Arial">Do you actually own one, I heard they weren't avail. yet?

Have you done much a/bing with miked amps?