Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Tube Emulation & EQ
Tube Emulation & EQ
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th March 2018, 03:49 AM   #411
Printer2 is offline Printer2  Canada
diyAudio Member
 
Join Date: Apr 2010
He did a speaker sim also.

Speaker simulator based on Marshall JMP1
  Reply With Quote
Old 8th March 2018, 04:52 PM   #412
Gnobuddy is offline Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by mjd_tech View Post
The kind of fizz I'm getting is different than the "tube screamer" or "rat" diode clipping fizz. It really does seem like a burst of oscillation, possibly at RF, so I can't see it on my "high dollar" scope.
Ah. It seems I completely misunderstood the entire situation and generally haven't got a clue. That probably means I should run for President.

What about a 100pF cap from each MOSFET drain to ground? With your 100k drain resistors (and ignoring loading, stray, and input capacitances), that will restrict bandwidth to about 16 kHz, three or four times more than we need for electric guitar, but hopefully enough to ensure RF stability.

Quote:
Originally Posted by mjd_tech View Post
I've looked around and have found most guitar speaker simulator circuits use a 4th order lowpass and there's a peak somewhere 2 - 4kHz and another one 100-200hz
I can imagine the need for the 100Hz high-pass if you're plugged into a powerful P.A. system that really does go down to 30 or 40 Hz, but most of the smaller P.A. and powered speakers I've encountered rarely have a response that goes below 60 or 70 Hz (this probably applies to your bookshelf speakers, too.)

So I have a suspicion that guitar speaker emulation doesn't really need to include additional bass rolloff for most typical situations. If we get the high frequency end right, it will probably do the job just fine.

Quote:
Originally Posted by mjd_tech View Post
Mine has a 6 saddle bridge, and 22 frets. It's a "parts caster". Gets the job done, nearly bulletproof, stays in tune, I don't care if it falls off the stand and gets dinged up.
Guitars are very personal things, aren't they? Probably my favourite is a Korean-made semi-hollow similar to an ES-335. Tonally, its almost at the other end of the electric guitar spectrum from a stinging 'Tele. A Blackface Fender seems to be a match made in heaven for this guitar - it sounds really good even with my hybrid Super Champ XD set to the clean channel.

But I also have a Les Paulish thingy I love, and I'm starting to miss having a 'Strat. But the narrow necks on Fenders are a headache for me.

I've grown weary of hauling an acoustic guitar, an electric guitar, and a bass guitar to jams, so from time to time I dream about a guitar that can do both passable acoustic sounds for chords and general rhythm playing, and also electric guitar sounds for solos. There are some commercial solutions, all beyond my financial reach. If I could find a way to put a piezo on my semi-hollow without ruining its appearance, that would probably do it.

But that's another project for another time. Now, I use my Super Champ XD and play both chordal and solo parts through the same semi-hollow guitar. If the KMG preamp sounds as good as the SCXD, I'll build one of those, and leave behind the SCXD. One less delicate box to haul around to jams.

-Gnobuddy
  Reply With Quote
Old 8th March 2018, 04:54 PM   #413
Gnobuddy is offline Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by Printer2 View Post
He did a speaker sim also.

Speaker simulator based on Marshall JMP1
That seems to have the same slope at both ends of the frequency response. Probably second-order.

-Gnobuddy
  Reply With Quote
Old 12th March 2018, 09:41 PM   #414
Gnobuddy is offline Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by voltwide View Post
Which brings me back to my personal opinion that the technical aspect most of the time is overrated.
I was reminded of Voltwide's comment last night.

Some days ago I stopped by at a local thrift store. A small speaker caught my eye - two roughly 4" aluminium-cone speakers and a tweeter, mounted in a D'Appolito (MTM) layout in a small enclosure with a roughly triangular cross section. Probably intended as a TV centre channel speaker, or for wall mounting to provide background music in a coffee shop.

The brand was Digital Research (do an Internet search for "white van loudspeaker scam" to learn more about this brand!), but the asking price was only $4.99. Not much to lose there, even if the speaker turns out to be dead or not to sound great.

I had a couple of possible uses in mind (as a mic-stand mounted foldback vocal monitor when my wife and I sing at jams, or in a battery-powered portable guitar amp.) For only $5, I decided to buy it.

So last night I connected the $5 speaker to a $15 class D audio amplifier board powered by a $4 switching power supply.

I made up a 1/4" jack to RCA plug adaptor cable, and connected a dirt-cheap ($25 USD) Danelectro Fab chorus pedal to act as a preamp. (It was within arm's reach; the graphic EQ pedal I would normally have used was in the other room. I was lazy.)

Finally I plugged in my beater Epiphone Les Paul SP-II, bought about 25 years ago for $150 USD (a new one costs $250 Canadian today: Epiphone Les Paul Special II - Ebony - Long & McQuade Musical Instruments )

No tone control (except on the guitar.) A full-range speaker with a tweeter. No valves. No JFETs. No de-nastifying filter.

Yikes - how nasty is this going to sound? Or will the chorus pedal suppress the harshness and save the day?

Well, after making a few slight adjustments to my right-hand playing technique, I got some really nice clean tones out of this $199 guitar and amp combination. Nice enough that my wife commented on how good it sounded from across the living room.

That's when I remembered Voltwide's comment, about how the gear doesn't matter anywhere near as much as most musicians think it does.

The Danelectro chorus pedal definitely played a role here, taking off the harsh edge that you usually get with a solid-body electric guitar plugged into an entirely solid-state guitar amplifier. Like other cheap Danelectro pedals I've tried, this Fab chorus pedal sounds really good, but looks really ugly in its cheap plastic housing.

I had anticipated a severe shortage of bass, but, at least at the low SPL I used last night, this was not really a problem. Open "cowboy chords" sounded full. There was no evident shortage of bass for single note runs all the way down to the low open "E" string.

The combination of Danelectro pedal, class D amp, and white-van-scam Digital Research speaker actually sounded good enough that I might put this together with a 20-volt cordless tool battery to make a small portable go-anywhere guitar amp. Spring is almost here, and this part of BC will soon be bursting with green things and beautiful wildflowers soon. It would be nice to be able to go to a park, sit in the middle of all that natural beauty, and play some electric guitar.

Given its shady origins and even more shady distribution/ marketing method, it proved rather hard to find an online photo of my $5 Digital Research speaker to show you guys. I finally found one - from a scam artist trying to sell it as a Polk system he claimed to have inherited from his dad!

So I stole the scam artist's "Polk" speaker photo, and attached it to this post. Now you too can enjoy the beauty of this white-van speaker special!

(It looks pretty decent. That - and the tempting backstory - are key ingredients in hooking gullible people into buying "white-van-speakers".)

-Gnobuddy
Attached Images
File Type: jpg Digital_Research_Centre_Channel_Speaker.jpg (122.6 KB, 85 views)
  Reply With Quote
Old 13th March 2018, 03:45 AM   #415
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
I'm highly amused at the brand name! The owner of the "original" company of that name wrote CP/M, the first microcomputer operating system (of any popularity), and infamously blew off (I forget which, maybe both - these computer history stories are so incredible but true) Bill Gates and IBM. By the time the brand name was used on speakers, the original company had surely folded.

I've seen some model of acoustic guitar with a speaker in it to give it a little more volume or bass or whatever, and I was thinking that kind of thing is the perfect place to use one of these modern low-power (2 watt? 20 watt??) Class D power amps.
  Reply With Quote
Old 13th March 2018, 04:15 PM   #416
Gnobuddy is offline Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by benb View Post
The owner of the "original" company of that name wrote CP/M
The version I heard was that Kildall blew off IBM, who then went to a young charlatan named Gates, who in turn bought Bill Paterson's "Quick n Dirty Operating System" for a song, sold it to IBM for millions, and so was launched on his long career of stepping on a thousand throats to get whatever he wanted by any means.

The first personal computer I ever used ran DOS, so I missed the era of CP/M.

After killing Seattle Computer Products and Digital Research, Gates went on to kill many other good companies, including Dr. DOS and Be, Inc, makers of the BeOS, the most fascinating PC operating system I've ever had the pleasure of using. By this time Microsoft had enough clout to simply tell computer retailers that if they sold BeOS, they would lose the contract to sell Microsoft products. No retailer could afford that, so BeOS died a sorry and undeserved death.

Quote:
Originally Posted by benb View Post
these modern low-power (2 watt? 20 watt??) Class D power amps.
If you believe the Amazon or Ebay ads, every class D amp starts at about 100 watts (even if it runs on two AAA cells), and power output only goes up from there.

The one I'm using is currently running on a 24V, 2A power supply. Like most of them, it's based on a chip containing four drive circuits, wired up into two bridge-mode power amplifiers.

I figure at least 2 volts lost across each output device, so a maximum peak voltage of 20V across the speaker. That translates to 50 W RMS into a 4 ohm load, or 25 W RMS into an 8 ohm load. (My power supply is marginal with a 4 ohm load, but I don't think I've gone beyond a few watts output power yet.)

The $5 "Digital Research" speaker measured 3.4 ohms DC resistance with my ohmmeter after subtracting its zero offset, so it's nominally a 4 ohm speaker.

-Gnobuddy
  Reply With Quote
Old 13th March 2018, 09:23 PM   #417
voltwide is offline voltwide  Ireland
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by benb View Post
I've seen some model of acoustic guitar with a speaker in it to give it a little more volume or bass or whatever, and I was thinking that kind of thing is the perfect place to use one of these modern low-power (2 watt? 20 watt??) Class D power amps.
Yes, for that app class-d is the way to go - TPA3118 from TI for instance. That is the one I use with my mobile 12V-amps.
  Reply With Quote
Old 14th March 2018, 04:52 AM   #418
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
Indeed, TI was what I was thinking of. It seems they've really been promoting their Class D stuff, so much it makes me wonder if they're going to drop analog power chips like the LM3886.
  Reply With Quote
Old 14th March 2018, 05:40 AM   #419
Gnobuddy is offline Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by benb View Post
it makes me wonder if they're going to drop analog power chips like the LM3886.
I have been staring at the same writing on the wall.

Mass-produced Hi-Fi is dead, and class D audio power amplifiers allow manufacturers to make products that are smaller, lighter, cheaper, and more powerful. That's a pretty potent combination of positives. Nobody cares if they are not (yet) up to true Hi-Fi performance levels.

There was a recent thread on diyAudio about a 600 W (!!) TI class-D audio power amp evaluation board that was selling (during a half-price sale) for something like $80 (USD). How can you possibly compete with that with class AB? The heatsink for a 600 watt class AB amp alone would probably cost more than $80.

-Gnobuddy
  Reply With Quote
Old 14th March 2018, 08:59 AM   #420
voltwide is offline voltwide  Ireland
diyAudio Member
 
Join Date: Jan 2010
agreed. The amp you are referring to is TPA3255 EVM-board. I could test this extensively here as a friend led it to me for several months. I would not really go for 600W with more than 40W power dissipation on that tiny chip. But it is a very nice choice to design a compact mono block for around 100W applications - that may be powered by a 36V pedelec battery.

Last edited by voltwide; 14th March 2018 at 09:01 AM.
  Reply With Quote

Reply


Tube Emulation & EQHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
CA 3080/LM 3886 tube pwr amp emulation metalhead Solid State 2 3rd February 2018 03:10 PM
SIT Device Emulation poynt99 Pass Labs 1 27th April 2014 09:14 AM
Tube emulation with transistors fireworks Tubes / Valves 17 4th February 2014 06:03 PM
Tube emulation (pritchard article) Barre Instruments and Amps 7 4th November 2010 01:28 PM
Tube amp semiconductor (FET?) emulation danV Instruments and Amps 11 24th June 2008 09:40 PM


New To Site? Need Help?

All times are GMT. The time now is 04:33 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki