Loudness in smaller combo amps

RJ Guitars · Post by **RJ Guitars** » Sat Sep 29, 2007 4:41 pm

So when I think of smaller combo amps, Twins seldom come to mind... but if I was to evaluate them it seems obvious enough that it's by their brute design that they get the volume... big iron and in some cases high efficiency speakers. Then of course those 4 output tubes. I think everyone will agree that the cabinet design is not especially efficient...

How about the average Deluxe Reverb, or the more recent Pro Junior, or any number of other smaller combos? I put a high SPL speaker in a Fender Pro Junior (10" speaker & 2 EL84's) and that thing is so stinking loud I generally can't find occasions to crank it up into the sweet spot... now that is to admit I play small venues and maybe we need to define "loud". Still, even outdoors it's an earfull to stand in the path of this thing. I think it is that piercing high/mid range of the EL84's that allow it to really cut through the mix.

For me, the Pro Junior at $200.00 EBAY price, is the best sounding "loud for the dollar" combo amp you can get.... they are easy to carry around... (I've also eventually gutted and rebuilt every one I've ever owned - they are great donors!)

In a recent experiment to make an amp that I could play at church ( a well dampened 320 seat Auditorium), I went the other way with speaker efficiency and used a low SPL speaker in a push pull triode output amp... It is golden for that venue. I run it with everything on 8 and life is good. This amp defines for me what is "not Loud". It also provides a lesson that the loudest sound you can get out of an amp may not be the most pleasant... Take many of the "old worn out" amps that we used as high school kids in a band... some of those were awesome but the tubes and speakers were way past their prime and not very efficient.

Finally, is there more to be said about cabinet design? Below are a couple articles that provide much food for thought...

http://trueaudio.com/st_diff1.htm

http://sound.westhost.com/bafflestep.htm

rj

riscado · Post by **riscado** » Mon Oct 01, 2007 12:08 am

another big factor for me when it comes to loudness notion is the room you're playing and the compression of the amp itself...

My tweed deluxe clone seems to be a fairly loud amp when played in some rooms, yet move it to a different room and I got a not so loud amp...

A different thing altogether (not really the same as what you guys are discussing) are the amp deceiving capability to appear really loud, when you hit 6 on the volume, but afterwards they just start compressing with not real volume increase and our hears quickly seem to settle into the fact that the amp might not be as loud as it initially might have appeared.

completely offtopic: no matter how much I love other amps, narrow panel tweed deluxes are for me a thing of beauty, it seems somewhat bassy at first, but when you push it, there's a higher mid frequency grind that just sounds absolutly marvelous, also the notes played clean seem to swell and swirl around you.

bueller · Post by **bueller** » Mon Oct 01, 2007 7:01 pm

For loudness in small amps, don't forget about what voltage dividers and negative feedback can do. Adding negative feedback can make a loud amp not loud any more. The AC 30 is much quieter if negative feedback is added and well it doesn't sound like an AC30 anymore either, but thats another story...
I had the opportunity to fix the nasty buzz in this Montgomery Ward GIM 9131A, which is kind of a poor mans twin. It has two 6L6s at 400VDC or in this case the owner had erringly put in 6550s. This thing should be loud as anything, but it's not. The first thing the input signal sees is a 47K with 150k to ground, rather than the usual 1M to ground, and it has 10K feedback resistor against a 680 ohm to ground. Couple that with a tiny OT and cathode biased power section and I can turn this thing up to ten and it doesn't hurt at all. It sounds really good. I think a lot of "loud" combos may not have as much interstage voltage dividers and very little or no negative feedback to tame the output.

CaseyJones · Post by **CaseyJones** » Tue Oct 02, 2007 1:14 am

As far as I'm concerned there is one thing above all that will make a small amp loud and that's a good speaker. 100+ decibels at one watt is loud any way you count it. The trick then is not to muffle your good speaker in a poor cabinet design, for instance the Silvertone 1482 has got to have the worst cabinet ever.

The rest of it is to carefully manage your gain and obviously a 'Wreck is fabulous in that department.

WholeToneMusic · Post by **WholeToneMusic** » Tue Oct 02, 2007 4:06 pm

Another thing i thought that was worth mentioning is Lens technology, in the 70's i believe it was called tone ring. Where you dial in the projection of the cabinet by the thickness of the baffle board. An amp that has a 3/4" baffle is not going to sound as focused as an amp that has a 1 1/2" baffle, thus it will not sound as loud. Essentially this adds 1 1/2" to the cone diameter.

dartanion · Post by **dartanion** » Tue Oct 02, 2007 4:32 pm

FWIW, I used my new 18watt Liverpool last night for rehearsal with the SE/PP pot on full SE and the band was complaining that I was too loud. Mind you that I had the volume at a little over 1/4 and in SE mode is good for about 5-6 watts. I have been using the cab pictured in my avatar loaded with a AlNiCo Blue Dog which is very efficient.

riscado · Post by **riscado** » Tue Oct 02, 2007 6:43 pm

Another thing i thought that was worth mentioning is Lens technology, in the 70's i believe it was called tone ring. Where you dial in the projection of the cabinet by the thickness of the baffle board. An amp that has a 3/4" baffle is not going to sound as focused as an amp that has a 1 1/2" baffle, thus it will not sound as loud. Essentially this adds 1 1/2" to the cone diameter.

I will have to disagree with your statement wholetonemusic, out of experience of baffle thickness done with the same amplifiers/same speakers, I know for a fact that does not happen, actually if anything happen it was the opposite... more focused? Yes a little more. Louder? Not really, actually it was a little tamer...

CaseyJones · Post by **CaseyJones** » Wed Oct 03, 2007 2:55 pm

dartanion wrote:FWIW, I used my new 18watt Liverpool last night for rehearsal with the SE/PP pot on full SE and the band was complaining that I was too loud. Mind you that I had the volume at a little over 1/4 and in SE mode is good for about 5-6 watts. I have been using the cab pictured in my avatar loaded with a AlNiCo Blue Dog which is very efficient.

There you go! No wasted gain and a good speaker equals a loud amp.

John Frings · Post by **John Frings** » Fri Aug 13, 2010 11:05 pm

Bueller,
I came across this website recently while looking for info on a Montgomery Wards head I found in the junk about 6 months ago.
From the info I have gotten it is a GIM 9131A like the pictures you have posted. A few months ago I had a tech go through it and it is in pretty good shape. He didn't have to do much. I however decided to put a 3 wire cord on it instead of the 2 conductor ac cable it had. I ran the black or hot to the terminal strip, the white.neutral goes to the reset switch and the ground is soldered to the chassis. After firing it up I noticed a pretty audible hum so now I am considering recapping at least the power cans multi section caps and might go further and get rid of most of the ceramics if I can find some matching the values.
Have been advised by the tech to go with either Mallory 150 series mylars or Sprague orange drop propylene. Tough finding them though. Any tips are appreciated.

Structo · Post by **Structo** » Sat Aug 14, 2010 5:25 pm

The hot (black) wire should always go to the fuse first.
That lessens the chance of a hot chassis in the event of a short.

John Frings · Post by **John Frings** » Sat Aug 14, 2010 11:10 pm

I'll follow up on your tip regarding the hot going to the fuse. Thanks

JD0x0 · Post by **JD0x0** » Sat Aug 14, 2010 11:34 pm

I think the "volume" has alot to do with the amps EQ as well. It takes more wattage to drive bass and low mids. 50 watts into a tweeter can make you deaf, 50 watts into a subwoofer would be extremely quiet in comparison.

Good transformers and proper voltages will also yeild more clean headroom and volume usually

tubeswell · Post by **tubeswell** » Sun Aug 15, 2010 12:07 am

IME 'loudness' is affected by a range of things incl. speaker efficiency, pre-amp gain structure, OT size, output tube type.

E.g.: you can have a 'quiet' amp that all of a sudden is a lot louder with a pedal in front of it. Take a 5G9 for example, a tweed front end with a 12AY7 in v1, followed by a LTP inverter and fixed bias 6V6s in PP. This amp sounds nice'n'clean, without pedals, but with a pedal can sound about X times as loud, just because the power amp section has the capacity to be loud, but the pre-amp isn't configured to drive a lot of input signal into the 6V6 grids, but when you put a (booster-type) pedal in front, then because you are feeding a bigger input signal at the start, then everything is 'bigger'.

David Root · Post by **David Root** » Sun Aug 15, 2010 4:18 am

Wow! Nice to see this thread resurrected after 3 years.

In the interim I have started using more efficient and older speakers, Altec 417s (12") in oval back cabs and and JBL E130s (15") in a closed back crudely ported bass cab.

No doubt about it, efficiency works! These two speakers are pretty different, the Altec is Alnico, the JBL ferrite, but both have huge voice coils, 3" and 4" respectively, and big magnets too. They sound very different too, but I love both of 'em!

They force you to pick better because they are so articulate, especially with a Dumble type amp, the opposite end of the spectrum to a Celestion/Marshall/Les Paul where you can get away with a lot.

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