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Instruments and Amps Everything that makes music, Especially including instrument amps.

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Old 11th June 2017, 08:37 AM   #11
Enzo is offline Enzo  United States
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I have no desire to push details around either. Yes we decided the original amp made 15 watts, but your first proposal was to use a TDA2050 plus a beefier power supply and..

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I might actually meet or exceed that 30w spec.
That is where I got the 30 watts. Then you pointed out you can get 35 watts with another configuration. My intent was to point out that getting 35 instead of 30 was a pointless improvement. Now you may have had other things in mind, but that is where I got what I was talking about.


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6db is double the sound pressure. Do we need to have an argument about how much fletcher-munson matters?
Sound pressure and amplifier power are not the same thing, no matter how related. I would suggest we determine what increase in amplifier power is needed to cause your increase in SPL. And perhaps our argument will dissolve.

And as to the sarcasm over F-M curves, frankly I don't need it. I was genuinely trying to have a technical discussion with you, and I just lost all interest. So do whatever you like, have a nice day.
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Old 18th June 2017, 08:02 PM   #12
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Originally Posted by Tubelab_com View Post
Note that the speakers efficiency plays a large part in the volume an amp can produce. A 5 watt amp through a 100 dB speaker is about as loud as a 50 watt amp through a 90 dB speaker.
Yes, right on!! I wish combo amp manufacturers would state both
power wattage and speaker sensitivity in their specs. "100 watts" by itself means diddle-squat! 100 watts driving a JBL D130 (103 db sensitivity)---now THAT's *******' LOUD!! 100 watts driving a Eminence Legend (90 db sensitivity)---well, not so loud....probably not enough to keep up with a loud drummer, unless you're clipping the hell out of it.
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Old 19th June 2017, 12:58 AM   #13
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Originally Posted by dotneck335 View Post
100 watts driving a Eminence Legend (90 db sensitivity)---well, not so loud....probably not enough to keep up with a loud drummer
100 watts is +20 dBW. Once you have converted an amps output power to dBW, it is simplicity itself to calculate the SPL produced by a speaker of a given sensitivity - you just add the two numbers.

In this case, 20 dBW of power feeding a speaker with 90 dB@1W sensitivity, gets you (90+20) dB SPL, or 110 dB SPL @1 metre.

110 dB is about as loud as a "chainsaw at 1 m distance" ( SPL level chart).

110 dB is also more than three hundred times as much sound power as you need to start causing hearing damage (85 dB).

Certainly 100W into a 100 dB @1W speaker would be even worse - 120 dB SPL @ 1 m, enough to cause permanent hearing damage literally instantaneously according to some sources I looked up.

At 85 dB SPL, the authorities claim you can sustain several hours of exposure without hearing damage (arguably, that limit is way too high, and was set for the convenience of the manufacturing industry rather than the protection of employees).

But, at 120 dB SPL, there is no such grace period of hours or even minutes. Damage is virtually instantaneous - by the time you hear the sound, your ears are already damaged. Even a seconds exposure could cause permanent hearing damage.

No surprise, then, that so many of those famous guitarists who used 100 W amps "back in the day", are now deaf, or suffering from severe hearing loss and tinnitus. Jeff Beck, Eric Clapton, Neil Young, Phil Collins, Pete Townshend, Brian Wilson, Chris Martin, and on and on and on. ( 8 Famous Musicians With Hearing Loss , 10 Famous Musicians With Hearing Damage )

Loud drummer? Fire him/her, or get him/her an electronic drum kit. A much better solution than being condemned to live out your life with deafness and/or tinnitus.

-Gnobuddy
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Old 19th June 2017, 03:32 AM   #14
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You are forgetting about necessary headroom. You need at least 10 db to avoid clipping; that puts your 100 watt amp + 90 db speaker at 100 db SPL. Loud, but not enough to keep up with an enthusiastic drummer. If you dislike actual human beings playing instruments, well...........
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Old 19th June 2017, 07:31 AM   #15
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Default Apples or Oranges?

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Originally Posted by dotneck335 View Post
You are forgetting about necessary headroom. You need at least 10 db to avoid clipping; that puts your 100 watt amp + 90 db speaker at 100 db SPL. Loud, but not enough to keep up with an enthusiastic drummer. If you dislike actual human beings playing instruments, well...........
Are we talking rock guitar or bass/acoustic guitar? If the latter, I agree with you. If guitar, the amp will be well into clipping (somewhere) regardless of its wattage

As a lapsed bassist I was always annoyed at the weight of gear I needed to haul to be heard over the guitarist with his 15W 1x12 combo. Which was well loud enough to be heard over the drummer.
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Old 19th June 2017, 12:26 PM   #16
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Originally Posted by dotneck335 View Post
You are forgetting about necessary headroom. You need at least 10 db to avoid clipping
With a fairly low crest-factor signal (bass guitar) and a built-in compressor, there's no need for that.

To the OP, I wouldn't bother with the marginal increases you can get by going from 15w to 50w.
Find a mono class D amplifier board, give it whatever SMPS is needs. Look for 3-500w.
Grab a good 8" PA speaker, tune the ports somewhere sensible and you'll have something that might not look like much, but will be very impressive to hear.

Chris
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Old 19th June 2017, 04:14 PM   #17
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Originally Posted by dotneck335 View Post
If you dislike actual human beings playing instruments, well...........
No, I dislike musicians going deaf through ignorance about the danger of excessive SPL. Being deaf is not fun, just ask any now-deaf former musician if he/she feels it was worth it.

The human race has had music for over 40,000 years, as documented by the discovery of ancient bone flutes. But going deaf in large numbers because of stupid-loud music is a recent phenomenon, going back less than a century.

Incidentally, contemporary popular music drum kits are stupid-loud, because they evolved from military drums, which in turn were extremely loud because they had to be heard, outdoors, by long columns of marching soldiers.

But the world is full of traditional drums of dozens of different varieties, none of them loud enough to deafen the musicians near them.

-Gnobuddy
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Old 19th June 2017, 04:31 PM   #18
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Originally Posted by chris661 View Post
With a fairly low crest-factor signal (bass guitar) and a built-in compressor, there's no need for that.
I usually plug into an ART Tube MPC ( https://www.sweetwater.com/store/detail/TubeMPC ), and then go straight into our little PA.

The MPC is a nice little preamp with a compressor that is polite and unobtrusive as long as you set the knobs with some awareness of what you're doing. It's got 1/4" and balanced outputs, switchable to line or instrument level.

There's a switchable high-pass filter at 70 Hz, which I find works very well with my 5-string bass, tightening up the sound, and spending the P.A.'s output power on the frequencies that matter.

The little MPC is quite versatile (works well on bass, guitar, and vocals too.) And it's very affordable as a bonus. Nice bit of kit!

Quote:
Originally Posted by chris661 View Post
Grab a good 8" PA speaker, tune the ports somewhere sensible and you'll have something that might not look like much, but will be very impressive to hear.
Lately I've been playing through an 8" speaker driven by 30 W of solid-state power, or sometimes a pair of old Yamaha 8" P.A. speakers driven by a larger Yamaha powered mixer (couple hundred watts, I think, though we never use most of that power).

Even 30 W is actually plenty of power for what we do. No stupid-loud SPL levels, and we go home at the end of the day with our hearing intact.

I am aware that kilowatt-level power is now commonplace among bassists. I have no comment on that.

-Gnobuddy
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Old 19th June 2017, 07:08 PM   #19
ericj is offline ericj  United States
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Quote:
Originally Posted by chris661 View Post
With a fairly low crest-factor signal (bass guitar) and a built-in compressor, there's no need for that.

To the OP, I wouldn't bother with the marginal increases you can get by going from 15w to 50w.
Find a mono class D amplifier board, give it whatever SMPS is needs. Look for 3-500w.
Grab a good 8" PA speaker, tune the ports somewhere sensible and you'll have something that might not look like much, but will be very impressive to hear.

Chris
I'm fairly skeptical of the 15W original rating. You can't find much in the way of positive reviews of the TB10. Mostly people bitterly complaining of how anemic it is.

I suspect that manufacturers are playing fast & loose with power output numbers. Like the Peavey GT-5 battery powered guitar amp, "5 watts" they say, but the chip amp in it is rated for 0.5W max. It's a horrible little piece of poo but learning that only set me back $3.

As for 8" PA speakers, I could probably find something - i have a friend who has a retail/design/install PA business. Former roadie with decades of bench repair and speaker design experience. He probably has something on a shelf in the back. He doesn't, fwiw, have a high opinion of the amount of design and testing that goes into most bass combos and cabinets. I think his exact words were "they just stick a speaker in a box".

As i said before, i know that for the electric guitar, the FR and distortion characteristics of the speaker are a critical part of the character of the total instrument. I suspect, for example, that the propensity for a 12" paper cone to distort above about 2khz, and to have issues with the cone rippling below 200hz or so, is actually considered a feature.

But i think electric bass is pretty different from electric guitar, and that electric bass can probably be very well played through a GOOD high fidelity speaker system with a tight, stiff low end.

And i think Crate stuck a 'guitar' speaker in this bass amp. I may even try it in a free-air guitar practice amp design.

So I'm going forward with this bigger power supply + tda2050 + heatsink + more gain + 8" wide-range woofer designed for a tiny reflex enclosure plan. I have all the stuff. I think it might be pretty good at 45-50w. Even just throwing the woofer into the box with no other changes has made it a much better amp.

Going forward i might try a hundreds-of-watts class-D approach. Sure has a 1x300w module that wants a 40v single supply. There are a lot of new mean-well switching supplies that are pretty svelt and would fit in this enclosure. But that's spending another $70 or so, which i might do anyway.

Might do it in the slightly larger (and substantially better) Peavey Max 158 Bass practice combo i picked up for $7. I don't like the preamp controls as well on the 158, but the onboard tuner is above average, and the output is a respectable and believable 15W. For some reason, the 158 Bass has a TDA2050 in it, but it's implemented solidly in TDA2030 territory with a +/-22vdc supply.
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