Why build a micro amp and not something a bit more capable?

cometazzi

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I mostly agree with you. My problem with the 2 watt amps is that they're still too loud to truly crank in my space. If I had a different living situation it would probably be different.

To be clear, my complaint isn't that low power amps aren't useful. It's that the micro amps aren't micro enough for my needs. I need one that is going to be another 10dB quieter, at least. Probably more.

Would this put you in the right territory if you knocked the plate voltage down on the output tubes a whole bunch? Or if you ran only one side of a 12AU7 (or whichever tube) instead of both? Single-ended EF80? You could even *gasp* build a hybrid with a tube pre and SS output.

I seem to recall this will change impedance and you'd have to look at different OTs, but if you want to crank something wide open so everything is cooking, it might be the way to go?

That said, my Black N Tweed barely breaks up at all when it's dimed. So I've got a few overdrive pedals added to the project list.
 
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owlexifry

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Not sure how you mean not about getting the tubes cooking if you attenuate with the fryette so the amp runs loud but speakers get little of the power?
what i'm saying is, a "good sound/tone" (to me) is less about how hard the amp is cranked, and more about how hard the speakers are getting driven.

I'm saying this because i have found, while using a very good quality attenuator (allowing the amplifier to be cranked up) it still doesn't sound very good at low volumes (at least through a mesa 4x12 cab), because the speakers are barely doing anything.

there's a threshold where once the output signal drops below a certain point, the sound coming from the speakers becomes relatively dull and lifeless, the frequency response dips at certain spots (mostly highs and low end)

i suspect this is why fryette decided to include these very nifty switching options, to compensate for this at low volumes:
1660864647986.png
 

FenderLover

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I think this thread might represent a small slice of low volume users. A vast amount of recording is done without amplifiers at all, not to mention another section of folks who use modelers and amplifiers with programmable preamps and class D power amps. Even D-type amps, and others, are primarily preamp based with power sections that are intentionally clean. Somewhere, one has to draw the line and use the right gear for the task at hand. And that's why we need more gear.

For low volume playing, by definition, we can't move a lot of air. Given the excellent sound and utility of something like the Yamaha THR10C, it's tough to beat. And it has 2-1/2" speakers. I've got 20 tube amps, but at night I turn on the Yamaha.

What confuses me is the need for preamp tubes in the power section at all. A Champ is how may watts? It is only a few dB louder, if at all, than some micro amps, while the transformers and chassis are often the same size as what a 'micro' is trying to represent. I have no illusion that a P-P micro is replicating the real thing at all, given the Fletcher-Munson effect, triode character, and limitations of small iron. A lot of micro demos I'm hearing sound like bees in a can, and are often indistinguishable from the sound of a cheap OD in front of any generic amp, regardless of what it is titled. How can we have a "Deluxe" micro without the second channel and P-P output? Not to pick on the genesis of these fine designs, but do we just forget what a Deluxe is? The Deluxe Micro is much closer to a 5F2 in many ways, so why not just put a 6V6 back in there? I digress....

Use what you want, buy more gear, build more amps. It's all good.
 

robrob

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@FenderLover the Deluxe Micro EF80 is a full up Deluxe 2 channel preamp. Only the power amp is different.

This is a decent demo of the JCM800 Micro 12AU7 (don't listen on your phone ;) )



I have lost the link to a mic'd Bassman Micro (12AU7 push-pull) being played live by the Australian Circ de Sole lead guitar during a performance and it sounds awesome.

I have hundreds of emails from micro builders that are surprised by the full-bodied clean and overdrive tone of these little amps.
 
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joulupukki

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The EF80 puts out about 3 to 4 times more power, approximately 1w vs. 3 or 4w.
So…that’s a yes? ;) Is there a noticeable dB increase between 1w and the 4w EF80 amp?

I have hundreds of emails from micro builders that are surprised by the full-bodied tone of these little amps.
…and you are definitely to be commended. This micro is a stellar amp!
 

2L man

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When I listen music from Stereos I like how the guitars sound althoug volume is reasonably low so I really wonder how the same is difficult to achieve for guitar bedroom players?
 

owlexifry

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When I listen music from Stereos I like how the guitars sound althoug volume is reasonably low so I really wonder how the same is difficult to achieve for guitar bedroom players?
full, properly mixed stereo audio track, playing through flat response stereo speakers

vs.

guitar, amp, and sound coming out of presumably 12" guitar speaker(s) --> which also have to fight the acoustic sound of the electric guitar


my assumptions/premature conclusions are: 12" guitar speakers just don't sound that great at low volumes (vs. the same guitar speaker(s) at "ideal" volumes)
 

Paul-T

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When I listen music from Stereos I like how the guitars sound althoug volume is reasonably low so I really wonder how the same is difficult to achieve for guitar bedroom players?
So much of this is actually in our heads that it's almost impossible to disentangle.

But all I know is that I downsized from a 20W Park to a 5W 5f2a and the latter sounds hands-down better and allows me to play guitar more - so for me it's more capable, rather than less. But I'm not comparing them A-B, as we invariably tend to prefer the louder sound when we're comparing.
 

jvin248

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Build two of the little amps and drive punchier speakers with both. Do a wet-dry set up or run both set the same. More loudness.

Mic the little amp into a huge Solid State amp or PA system for those outdoor gigs.

.
 

Lynxtrap

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Has anyone tried to chain the output of a micro amp to the input of a larger amp, like the Garnet Herzog? @robrob ?
 

chas.wahl

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When I listen music from Stereos I like how the guitars sound althoug volume is reasonably low so I really wonder how the same is difficult to achieve for guitar bedroom players?

full, properly mixed stereo audio track, playing through flat response stereo speakers
vs.
guitar, amp, and sound coming out of presumably 12" guitar speaker(s) --> which also have to fight the acoustic sound of the electric guitar

my assumptions/premature conclusions are: 12" guitar speakers just don't sound that great at low volumes (vs. the same guitar speaker(s) at "ideal" volumes)
Seems to me that the above summarize concisely what this discussion is all about. I agree that there are two crucial missing elements: lack of power tubes and speakers that produce close to the same audio output characteristics and distortion effects at a much, much lower power level. I doubt that this is impossible to achieve, in terms of the technology required, it would just be a matter of there being a large enough market for such innovations to be developed and marketed.

Unfortunately, that's unlikely to happen, at least in my lifetime; sort of like doing something about climate change and current forms of energy production and use: there just aren't enough people interested in making it happen. When you take all the people who love music, subtract those who don't care too much about electrically-originated music, don't create music, still feel that the ideal is some kind of 100 W monster amp, don't need or want to play at home-tolerated volumes, then you're left with about the same percentage as the number of people participating in this thread, compared to the number who've posted to TDPRI today.

Something like that Yamaha THR box mentioned by @FenderLover shows that some people at the "industry" level are paying attention to this, but (without having heard, much less played through, one) I suspect that it's a bit over-engineered and "consumer-oriented" for this crowd -- what we'd prefer is to be given the elements at a more basic component level, for integration into the sort of thing we're doing: replicating, reimagining and tweaking tube amps. And the emphasis seems to be more on portability and variety of effects than "same sound, lower level" performance.
 

King Fan

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Cool discussion of *what* home players want (with ‘bedroom' as a more stringent subset) and *how* to get it — in a tube amp. I’m sure modelers can do it… but can a ShockBro build a modeler? Would they want to?

In my (new) experience, my Bassman Micro gets exactly what I want — tube distortion at household volumes. I don’t for a moment think it’s like owning a real 5F6a. OTOH, I like the tune-able distortion more than what I’ve heard from most modelers or pedals — in some cases, a lot more.

Micros are not for everyone. A THR10 would be cheaper and easier. Gigging? See above. Flapping your bellbottoms? See above. A new builder looking for a simple, fully-defined build with no hunting for a chassis, no choosing of PT and sorting of tasty mods, pots, and switches? Stay on the main road. But a fun, easily-customized build to get some tube distortion for home playing and home recording? Oh, yeah….

And re the EF80 v. 12AU7 thing, I’ll combine Rob's good insight about watts, and the fact that ~doubling the watts will increase loudness by ~3dB, and that 3dB is audible if not amazing, plus the fact that @joulupukki and I liked the tone of both tubesets, and suggest you can’t go wrong either way — but if you want a little quieter, the 12AU7 is a fine way to go.
 
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SerpentRuss

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Obviously, everyone's situation and reasoning for building a micro project is different, but I've always thought the core concept is having a real tube output section that can be driven to distortion below a certain volume level coupled to a known pre-amp configuration that has a unique and desirable sound itself. So in short, stay faithful on the front end, downsize on the back end.

As some have mentioned, the resulting low-power designs negate speaker breakup. The output section however is different as well. Does a push-pull pair of EF80s driven to distortion sound exactly like a quieter version of 6L6 valves driven to distortion? Probably not exactly. It's easy to see why modelers are becoming so popular.

I like small amps and I think micro projects are a great compromise to building the big boys but we all know they're not a whole lot cheaper to build. I have a friend that works as a recording engineer and session player. If someone wants to record their big rig dimed out, they have a room just for the gear. Maybe my next project will be an amp isolation box, LOL.
 

joulupukki

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@robrob (or anyone), so I'm a little confused on the plate dissipation and the output wattage on this micro amp. Rather than guessing, I hooked up my multimeter with alligator clips in mA measuring mode. Right now I've got a 12BH7 installed as the power tube. The dual triode is working in push-pull mode with the plates being Pin 1 and Pin 6. These are my measurements...

12BH7Current (Plate to OT Primary/B+)Plate to Cathode VoltageDissipation
Pin 19.24 mA293.9 V2.7 W
Pin 28.04 mA294.3 V2.4 W

Do I add these two dissipations together to total 5.1 Watts total output? Or am I completely confused on this? If I'm right, doesn't this mean my amp is putting out as much as the 5W output transformer can handle?
 

SerpentRuss

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@robrob (or anyone), so I'm a little confused on the plate dissipation and the output wattage on this micro amp. Rather than guessing, I hooked up my multimeter with alligator clips in mA measuring mode. Right now I've got a 12BH7 installed as the power tube. The dual triode is working in push-pull mode with the plates being Pin 1 and Pin 6. These are my measurements...

12BH7Current (Plate to OT Primary/B+)Plate to Cathode VoltageDissipation
Pin 19.24 mA293.9 V2.7 W
Pin 28.04 mA294.3 V2.4 W

Do I add these two dissipations together to total 5.1 Watts total output? Or am I completely confused on this? If I'm right, doesn't this mean my amp is putting out as much as the 5W output transformer can handle?
You're using the 125B? If so, it's good for 30 mA of bias per side AND 5 watts of music power. None of your measured power on the primary side is transferring to the secondary, assuming you're not playing and measuring at idle. It's DC.

Also, your tube dissipation for the 12BH7 is safe, but you probably knew that. I think they're good for 7 watts total.
 

joulupukki

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You're using the 125B? If so, it's good for 30 mA of bias per side AND 5 watts of music power. None of your measured power on the primary side is transferring to the secondary, assuming you're not playing and measuring at idle. It's DC.
Yes, the Hammond 125B is the OT I'm using. Yes, measuring at idle. I guess I need to throw out most of what I thought about output tube dissipation and how it relates to music power through an OT. I guess how does that even work and how would I calculate what actual power is on the secondary? Still learning, obviously. ;)
Also, your tube dissipation for the 12BH7 is safe, but you probably knew that. I think they're good for 7 watts total.
Right. Running at about 73% dissipation right now.
 

mountainhick

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After building a flavor of @robrob 's Bassman Micro (here's my build thread: https://www.tdpri.com/threads/journey-of-my-bassman-micro-build.1100749/) I'm realizing how much I really like the features, versatility, and sound of this amp. At the same time, I'm wondering why didn't I just build this as a higher-wattage amp with a built-in attenuator (or maybe just a Type II MV control) so that it could be *the* amp I could use for gigging and at home practicing? Nothing crazy loud, but something between 15 - 25 watts.

The amp uses higher voltages on the pre-amp tubes like bigger amps. I'm simplifying, but would it just be a matter of increasing the power & output transformers (I guess probably the choke too ... and maybe the filter capacitors)?

I can't remember which one of the good amp techs on YouTube it was (watched his video a while ago) but he was basically trying to tell people not to spend $ on a micro amp and just play the amp you gig with at lower volume levels. At the time I questioned that, but now am coming around to that idea. Granted, a number of the micro amps available on the retail scene truly don't sound that great in comparison to Rob's great schematics.

Here's my herd of self-built hand-wired amps so far (Bassman/JTM45 Micro on the top of the stack):

View attachment 1017769


Sounds to me since you built the micro and the 18W, you should build that attenuator for the 18W and get back to us ;>)
 

joulupukki

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Sounds to me since you built the micro and the 18W, you should build that attenuator for the 18W and get back to us ;>)
Haha. The 18w works find plugged in to an attenuator (Captor X) but that's a different amp entirely. :) Still just trying to learn and understand all this stuff. Thank you for humoring me. I still can't decide which amp I like "better" (18w vs. this micro) ... like if I could only have one, which one would I keep? 8 times out of 10 I plug in and play the micro though, but probably because it's me goofing around inside my small home office.
 




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