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Discussion in 'Amp Central Station' started by surfoverb, May 18, 2015.
an ac15 is at least twice as loud
Right, and about three times as "Voxy" ... problem solved. No?
My "loud" amp is a TE Velocette 15 watt screamer. It's plenty loud for any space I care to play.
If it's not loud enough to fill the room, then it's likely there is a PA for the FOH anyway. I've never played a stage so huge that I can't get a great stage mix going.
But 12 watts? Way too puny.
im sorry but 12 watts is not "way too loud"
Sorry, i found the schematic, it's got TLO-72 op amps for the first two gain stages of both channels, but the op amp signal levels are low enough to stay clean, all dirt is handled by tubes..
As un-awesome as that sounds, it's actually a good way to make the amp much more reliable and quiet,
The op amp part can get the signal level up to where noise and heat is not an issue on the circuit board, then the leads running to the tubes are less likely to pick up hum.
They had it together enough to mount the sockets off the main board so tube heat didnt maim the printed circuit.
Take the back off and look, just don't be touch anything that could shock you!
It's actually pretty good for modern factory stuff..
Except for the reverb mount.. horror
surfoverb, I would assume....might be wrong...that those stock 16 ohm speakers are wired in parallel to get to that 8 ohm load. When replacing the speakers, one would want 1) 1 x 8 ohm speaker, 20 2 x 4 ohm speakers wired in series, or 3) two 16 ohm speakers wired in parallel.
Re: 15 watts versus 18 watts........IF...big IF....if those amps' output are measured in the same manner and are actually 15 and 18 watts prior to breakup, the 15 watt amp will NOT be any louder than the 18 watt amp through the same speaker set up....just as the 18 watt amp cannot possibly be louder than the 50 watt amp when both are run through the same speaker set up.
For the 15 watt amp to 'be twice as loud' as the 18 watter, the 15 watt amp would need to be run through a speaker than was 6 db more sensitive than the speaker that the 18 watter is running through. Through the same speaker, the difference in their output will be negligible to the human ear...at max clean output.
Bingo. Like many here, I've spent years gigging in bands, and know what I need when working with drums, other guitarists, etc. For me, my DR at perhaps 5 delivers about the right volume, and if it doesn't, then the band is too loud for me (how guys stand in front of Marshalls at full tilt remains a mystery after 40+ years of playing).
That said, I cannot comfortably play my '66 Champ at home with the volume more than halfway up - it's piercingly loud, and yet I know that it would be drowned out on stage. The difference is context and location, and no single amp covers all.
that explains why this amp is dead quiet even when cranked.
I can get some feedback with the vape engaged with fildertrons oddly but this amp is very quiet.
also it seems to take a long asstime to warm up. Im talking seconds but still seems longer than usual.
and when I turn the amp off I always crank everything and strum
which is supposed to discharge the caps, but it shuts off faster than other tube amps. usually when you do this you can strum for a few seconds
and hear sound fading away, but this amp you shut it off its a very quick fade to nothing, almost like a solid state.
well its not literally twice as loud .
20 speakers? **** that! thats like the deads wall of sound but id have a wall of mouse farts
thanks though I get the maths now
That's easy tell him to turn down. And you can't get much cheaper than free. Usually there is a reason something is free.
Lots of specific speaker recommendations.
But the thing that matters is the sensitivity rating in decibels. A 100db speaker is going to be MUCH lower than a 97db speaker in the same amp.
Power means very little. A Deluxe Reverb with the right speaker can keep up fine with a Twin Reverb that has the wrong ones.
BTW- there is NOT a difference in power tubes - there, power is power assuming the same type of circuit/bias system. You're probably thinking 6V6's are louder than EL84's. If so you have probably never heard an mid 60's Vox AC15 vs a mid 60's Deluxe Reverb. The DR has higher rated power, but (unless it has a high-sensitivity replacement speaker) the DR is nowhere near al loud as the Vox.
Sorfoverb, I have no idea where that '20' came from. Obviously 2 x 4 ohms was intended.
My rule of thumb was always 30 watts. Then a microphone if needed
Hmm... a 10watt through a 102db speaker pushes loads of air..enough
to trip up a young drummer....I have heard Princetons in 12" baffles
work great in bands..I think they are 12watters
My DRRI is overkill in most live situations...22 I think
Clean sound requires more power
Big amps are underrated IMO. I get it that aging players want smaller and lighter amps, which is cool. I have some 1 watt to 5 watt amps that are loads of fun, unless I want to hear big cleans.
Lots of people post about speaker sensitivity and amplifier watts as if those are the only considerations when calculating how much power is needed.
Other factors to consider are the distance from your speaker to your ear, how loud you want the direct sound average level to be at that distance (tip #1, you don't usually listen at 1 meter!), and also, if you are looking for cleans, you need to consider the waveform crest factor. If you want to amplify something that is clean and dynamic (like a Tele), you may want up to a 10dB crest factor over and above the average level, to allow you to reproduce waveform peaks without clipping. These are peaks that don't show up on a garden variety SPL meter, but are critical in reproducing a dynamic, clean sound. You can hear the difference.
An oscilloscope is the right tool to determine how much crest factor you like, and how much clipping (no matter how soft or "tubey") is acceptable to you for your clean sound. Some people describe liking their cleans with some ""hair". The crest factor discussion does not really apply to them, or any other type of distorted sound.
Pull out your scope, attach the probes to the speaker leads, and measure the voltage when you see the waveform start to clip. Next, square that number, then divide by the speaker load impedance to determine how much clean power you have on tap.
So, if you assume a speaker sensitivity of 97dB/W at 1M, and you are 10 feet from your amp, and you want your instrument to average 95dB at your ear, you need almost 6 watts of average power. if you are playing something clean with a lot of dynamics, that 6 watts isn't going to get it done for you. if you add a 10dB crest factor, your amp needs to put out an unclipped 58 watts. If you just want an 6dB crest factor, you would need over 23 watts. Again I reiterate, different people may prefer a different crest factor.
Then there is the issue of power compression, which is what happens when you heat up a smaller voice coil. As you push power into the coil, it heats up, and the impedance rises. Your 97dB/W at 1M speaker may become something less.
There is nothing wrong with smaller crest factors, or speaker compression, unless you want sparkling clear cleans. I like big cleans, which is why I like big amps. This is why a Twin can sound glorious at lower volume levels, and if you like cleans, a smaller amp may not get you there.
12 watts is not too much for me. YMMV, the math does not.
that's a fallacy. no need to strum chords while the amp is shutting off. the caps drain at the same rate just by turning it off (without the standby engaged, if there is one).
It depends if the caps have a draining resistor- most modern amps do, many vintage do not. The 'strum' trick does work since it is the last push the speaker gets from the voltage in the filter caps. Amp voltages can kill you, better to be safe than sorry IMO.
+1 with Dan. I like to 'hear' that voltage drain.....and then I check when the chassis is out. And..it is best with those amps that do not have draining resistors to maintain the drain by taking the power supply to ground because caps can sometimes recharge on their own....and like Dan noted....
it is a dangerous environment in there if you get to self-assured.
Paratus, that was an interesting post, thank you.
I dunno, I just re-read it and started yawning
It's efficiency. Your old speakers were maybe 96db SPL rated, CRex is a 102db speaker. Same place on volume knob, say pushing out 5w, with the 6db more efficient CRex speaker, your amp will now be effectively twice as loud as it was before using the 96db speakers. The old utah might even be less than the 96db, think I was being generous there. The Rex is just better, more efficient at turning that same amount of energy coming from your power amp into sound.
Think of the way intel has improved their processors over the years, every new revision, the wattage goes down, uses less power, but the actual processing it can do on less power goes up, their more efficient.
Think of light bulbs, heck some of the 6-7w LED bulbs these days can put out as much light as what a old 40-50w incandescent bulb put out. Their more efficient at turning that energy into light.
CRex is more efficient at turning energy into sound, same energy going in, more sound coming out.