What is the ultimate bedroom tube amp?

[socalscott]

miniwatt (MOST of which are simple and limited designs) you get none of that. Sheesh... You'd think I insulted the pope.

Chillax, just a bit of OT chit-chat is all. Nothing wrong at all with your position and what is practical for you. I'll just add that my TW Express based Hall has 5 sub-mini tubes and amazing EQ section. It is nothing like 'most' ultra-low watt amps. Spanky as it gets, chunky chord-age, thump that stays tight to the end and singing solos.

Any way, the OP would be sitting pretty with something as simple as a Tech21 30, Mustang III or Vox 15R Pathfinder. Versatility and tube-ish feel. Lots of flavors in these econo amps.

[Muskratt]

I would suggest to look at the 1/4 watt amps. Seems there is a few out their that are switchable like the VOX. under 600 USD for the head and the lil cab. It is all tube too.

[socalscott]

Ye ole $80 DG-Stomp headphone jack out to Greenback = nice apartment solution. The latest modelers must be plenty good.

[Steve A.]

Nice, quality work. The Air brake uses a similar load and most players think it's great.

Chuck- what did you use for the 25 ohm/50watt pot? About 10 years ago I was given a schematic with a very detailed description of the parts in a real Trainwreck Airbrake, but was sworn to silence by the person who owned it and drew it up. But after 7 years hasn't the statute of limitations already expired? I'll post the specific details as soon as I mount the hard drive it is on in an external enclosure...

And yes it was the most transparent attenuator I'd ever seen- I think that Ken Fischer designed it to go along with his Trainwreck amps.

Steve Ahola

[Chuck H]

Well I have to admit that I have never used or cloned an Airbrake. But IIRC the average load of the Airbrake is 20 to 30 ohms for a nominal 8 ohm application. Interestingly the Ho attenuator (Ultimate attenuator) also uses a similar load. I think the motive here is that speakers do present a VERY high impedance at most frequencies and only present their rated impedance in a narrow band. So the higher impedance for a fixed load should make the amp behave more like it would with an active load than , say, a fixed 8 ohm load. I have to believe it's true because a lot of people agree that the Airbrake and Ultimate attenuators are the best sounding. I have seen shots of the inside of the Airbrake and it appears to be a tapped Ohmite brand resistor (the kind that's mounted on little end tabs) and a rotary switch.

My own attenuator uses a more typical 6 to 10 ohm load for 8 ohm application. My personal unit uses my version of Randy Aiken's speaker load for the resistor. So it's an active load. But I have built a purely resistive version into some amps I sell using a 10 ohm resistor for the load. The variable resistor I use is a plain Jane Ohmite rheostat available from Mouser. My design incorporates a .5 ohm resistor that prevents turning the volume to full "off". But it also prevents the typically glitchy noise that rheostats make when coming off full rotation. I build my attenuators either in a 3x3x6 aluminum enclosure for mounting inside a head or combo or I hand bend a piece of aluminum plate to fit between the back panels of combo amps and mount the attenuator comonents on that.

Here's the purely resistive version. I can post the active load version if your interested:http://music-electronics-forum.com/t16468/

[Ramsay]

2 watts of tubes is loud . It's loud enough to damage your hearing or to get you evicted.

2 watts is 38% as loud as 50 watts.
5 watts is 50% as loud as 50 watts!

Do a search and download an "Amp volume" chart. Being able to see the numbers really puts things into perspective!

I understand your point of view, and I apologize, but I am using a Orange Tiny Terror conected in a box with a Celestion Vintage 30, and I never used this amp at 7.5W but only at 15W, because the sound is so much better and louder at 15W. I use it at bedroom level with the level control at 12:00.

So I can't imagine how a tube amp with only 2W can give that sound for bedroom level.
But I may be wrong because it has an amp of 0.5W (I don't remember the brand) and it seems to be good.

[Steve A.]

But I may be wrong because it has an amp of 0.5W (I don't remember the brand) and it seems to be good.

I have the tiny amp that Z-Vex makes in the same Hammond stomp box enclosure as MXR pedals (1590B)- the Nano Head- and it puts out 0.5w dirty or 0.1w clean. If you plug it into a 4x12 cab it kicks butt and is louder than bedroom level (I guess that would depend whose bedroom we are talking about!)

I don't think that it is the total number of watts available but that it does produce a good sound at what you (or your wife!) consider to be bedroom levels. I've had big amps that sounded good turned down low and I've had small amps that sound like crap when turned down low...

Steve Ahola

[Alan0354]

The inductors are available from Parts Express or any other speaker building site. They're used for speaker crossover circuits. The difference in tone is not huge, but worth it. The "feel" and tone of the amp is the same from full output down to about -12dB. At bedroom levels any attenuator I've heard does "suck" some tone. But the active circuit does sound a little better at bedroom levels and a lot better at higher volumes.

The 12.5mH inductor does have a core. Otherwise it would be the size of a football.

OK... Here's a secret... On a public forum... Ha!?! The .5mH inductor is actually two .25mH inductors in series, but out of phase. I place two copper shields with an insulator between them to avoid cancelling the inductance, which they would. But what I found is that the no core small value inductors emit so much EMF that they can cause feedback problems with single coil pickups. By stacking two series, out of phase inductors, and insulating them from each other, I keep the inductance but beyond the shields each inductor is emitting EMF that is out of phase with the other. This cancels the feedback with the pickup.

The active speaker load is designed to be somewhat the same impedance curves as a Marshall 4X12 cab loaded with Greenbacks. I filched it from Randall Aiken's site (which is always worth checking out).

I have a THD Hot Plate, sounds pretty good to me. how is yours compare to the THD?

[MWJB]

"2 watts of tubes is loud . It's loud enough to damage your hearing or to get you evicted.
2 watts is 38% as loud as 50 watts.
5 watts is 50% as loud as 50 watts!
Do a search and download an "Amp volume" chart. Being able to see the numbers really puts things into perspective!"

Utter poppycock! This is one of those things that is interesting but ultimately pointless to know (like objects falling at the same rate in a vaccuum...do you live in a vacuum with a bowling ball and a feather? Well, do you?). Nobody who has actually seen/heard a guitar amp would make such a chart. Unless you know someone who has built a 50W amp running a single EL84 at 250vdc on the plate through a 8" 90db 10W speaker? My point being that when you compare a 5W amp to a 50W amp, there is typically not one factor that remains the same, you're comparing apples to oil tankers.

[Steve Conner]

I have built such a device! :P And sure enough, all other things being equal, every time the power is increased by a factor of 10 it gets about "twice as loud", maybe a little more.

But as MWJB points out, all other things never are equal. The amp maker will give his 50 watt model a bigger cabinet and bigger, higher efficiency speakers than his 5 watt model. So it's more than "twice as loud", it is more like the difference between nuzzled by a kitten, and a Rottweiler chomping on your leg.

[tedmich]

and your ear hears very differently at low volume too! Google Feltcher Munster Curves

[Steve A.]

"2 watts of tubes is loud . It's loud enough to damage your hearing or to get you evicted.
2 watts is 38% as loud as 50 watts.
5 watts is 50% as loud as 50 watts!
Do a search and download an "Amp volume" chart. Being able to see the numbers really puts things into perspective!"

Utter poppycock! This is one of those things that is interesting but ultimately pointless to know (like objects falling at the same rate in a vaccuum...do you live in a vacuum with a bowling ball and a feather?

When trying to keep an amp at bedroom levels those charts are very appropriate. 5W is too much. 2W is too much. Even 1/2W might be too much.

But I do agree with you as far as amps on stage go- "1/2 as loud" is meaningless. The question is whether it is loud enough. (In the bedroom the question is whether it is soft enough.) FWIW you can get the Mesa Lone Star Special in a 2x12 cabinet and that amp gives you the choice of 30 watts, 15 watts or 5 watts. Same construction, same speakers, lower wattage. So 5 watts doesn't necessarily mean cheap construction. Just my opinion. YMMV

Steve Ahola

[Chuck H]

I have a THD Hot Plate, sounds pretty good to me. how is yours compare to the THD?

Dunno. Anyone ever seen a schem for a Hot Plate???

As I mentioned, my personal unit has a reactive load. The Hot Plate does not. Mine is infinitely variable. The Hot Plate is not. The Hot Plate now uses a lamp circuit of some kind for something. Mine does not.

The resistive load version of my design is super simple. I seriously doubt that the core function of any resistive attenuator is truely significantly different from any other.

[socalscott]

Ramsay,
Your 7.5W setting is not a good reference for a 2W amp result for BR levels. A 2W designed amp or say a 1/2W are at no loss for tone and volume.
By design is the key. My 2W head has a hand wound(light wire) OP tranny to beef up the bottom frequencies. It also uses 5 sub-miniature tubes. Combined with a 1/2W head...hugeness in a BR way. lol

[MWJB]

Steve A wrote: "FWIW you can get the Mesa Lone Star Special in a 2x12 cabinet and that amp gives you the choice of 30 watts, 15 watts or 5 watts. Same construction, same speakers, lower wattage. So 5 watts doesn't necessarily mean cheap construction. Just my opinion. YMMV"

True, but the Lone Star isn't really a 5W amp, it's a "2x12 30W" amp with a 5W setting...5W amps are usually entry level amps, cathode biased etc. I have a 2x6550 amp, runs about 510vdc on the plates, fixed bias, good for 65-70W...with a 6W setting. Even set at 6W it is loud enough for a lot of gig situations because it has efficient speakers pushing a large soundwave, lots of B+, a huge power transformer...these are not things usually found in "5W amps" (as with the Lone Star), even high end SE amps (like say a Victoria 5112 or a Carr Mercury). But then most folks are not likely to spend a couple of grand on a 5W amp that weighs 60lb+ & is the size of a refridgerator!

Tedmich "and your ear hears very differently at low volume too! Google Feltcher Munster Curves" They do as to volume but not necesarily as to tone specifically (though I appreciate the concepts dovetail). Sure, you can't get the full experience of a pair of 100W Marshalls through 16x12" without being on the stage in front of them....but then neither can the audience at that venue if they are just hearing the same rig through the FoH system. If recorded, you still hear the tone of the amp, but without the physical presence & soundwave from the speakers...that is unless your Hi Fi is hooked up to a similar speaker array and you listen to it at comperable dB....which I very much doubt you do.

Plus you have to consider the tonal qualities of a sound (rather than purely a W output/dB level), even a <0.5W amp when overdriven will become pretty "strident" & objectionable for bedroom/apartment use (my 12AT7, self split, push-pull amp, with efficient speaker can only really be played clean in my apartment)...the upside being that at low output levels/voltages attenuation becomes much simpler & cheaper.