On Tue, 14 Mar 2017 19:43:52 -0400, rickman <gnuarm@gmail.com> wrote:>On 3/13/2017 2:59 PM, Jasen Betts wrote: >> On 2017-03-13, dcaster@krl.org <dcaster@krl.org> wrote: >>> On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote: >>>> I've been looking into buying an Audio Generator (Sine and Square Wave). >>> >>> In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits. >> >> Also search "suite", which seems to be a common miss-traslaion of "kitset" >> >>> Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible. >> >> Electrically, tubes are harder to bust... > >No they aren't. Just leave one on for a few weeks and the filament >will go out, if it hasn't busted your wallet on the electric bill.Weeks? MTBF of 336 hours? You can't aford a tube's filament current? GMAFB I guess you never turn on a light bulb, either. Heaven forbid that you would make diner!
Audio Generator or Function Generator? Which to get?
Started by ●March 13, 2017
Reply by ●March 14, 20172017-03-14
Reply by ●March 14, 20172017-03-14
On 3/14/2017 8:23 PM, whit3rd wrote:> On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote: >> On 3/13/2017 4:26 AM, oldschool@tubes.com wrote: >>> I've been looking into buying an Audio Generator (Sine and Square Wave). >>> I mainly want this to run thru an amplifier to listen to... > >> I haven't read all of the posts in this thread, but I see a lot of >> confusion of the terms "function generator" and "audio generator". >> Audio simply refers to the frequency range of the signal generated >> without saying anything about the manner in which it is generated. But >> most signal generators output a sine wave and perhaps a square and >> triangle wave. > > That's incorrect; most inexpensive signal generators output a square and > triangle (hey, it only takes two op amps); adding a sinewave is complicated. > To do a GOOD sinewave, the old HP20x units had matched pairs of adjustable > capacitors, which are VERY pricey items. > > So, the iCL8038 and XR2206 and some other IC generators (which dominate > the market at the low-cost end) distort and/or filter the triangle wave to make > a "sinewave". The sinewave outputs are dreadfull.So they *do* produce a sine wave?> For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital > sythesizers are good, too. Neither is convenient for a test bench, though.I'm not clear on what you consider inconvenient, but you don't need much space to create a decent sine wave. I produce a board with a stereo CODEC and during test it produces a sine wave that I can't visually detect and defects in at any resolution. If I removed the application specific items and gave it a useful PC interface it could sell for maybe $50. It would have perhaps $20 worth of parts and could fit in an Altoids tin easily. I believe there are similar products on eBay which sell for less. -- Rick C
Reply by ●March 14, 20172017-03-14
Prickman wrote:> > > I haven't read all of the posts in this thread, but I see a lot of > confusion of the terms "function generator" and "audio generator". >** There is no such confusion here.> Audio simply refers to the frequency range of the signal generated > without saying anything about the manner in which it is generated.** But an "audio generator" has a particular meaning NOT the same as "function generator". FYI, terms mean what people men when they use them. ..... Phil
Reply by ●March 14, 20172017-03-14
On Tuesday, March 14, 2017 at 5:52:48 PM UTC-7, rickman wrote:> On 3/14/2017 8:23 PM, whit3rd wrote: > > On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote:> > So, the iCL8038 and XR2206 and some other IC generators (which dominate > > the market at the low-cost end) distort and/or filter the triangle wave to make > > a "sinewave". The sinewave outputs are dreadfull. > > So they *do* produce a sine wave?Not a sinewave suitable for a set of test results that can be easily analyzed. The "sinewaves" have all the harmonics of a triangle wave, but at lower amplitude, and this is accomplished with hand-tweak adjustments. If/as you want to test an amplifier for distortion, that 'sinewave' is not pure enough to use.> > For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital > > sythesizers are good, too. Neither is convenient for a test bench, though.> I'm not clear on what you consider inconvenient, but you don't need much > space to create a decent sine wave.What is inconvenient, is that one cannot dial the frequency with an analog knob, while listening for room resonances or speaker-crossover blips. A DDS solution will have to be programmed to do a sweep, and reprogrammed if you want to check that one part of the range that sounded odd... or at least, that was how the old Agilent DDS worked.
Reply by ●March 14, 20172017-03-14
On Tuesday, March 14, 2017 at 8:51:22 PM UTC-4, k...@notreal.com wrote:> >>> Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible. > >> > >> Electrically, tubes are harder to bust... > >> Weeks? MTBF of 336 hours? You can't aford a tube's filament current? > GMAFB I guess you never turn on a light bulb, either. Heaven forbid > that you would make diner!When I was in the Navy I had a mk 37 gun fire control system to maintain. The radar used a fair number of vacuum tubes. When the 5 inch 38 guns were fired the radar would go down after about two salvos because some tube had failed. So the system had a MTBF of about 5 minutes or less. Dan
Reply by ●March 14, 20172017-03-14
On Tue, 14 Mar 2017 18:34:53 -0700 (PDT), "dcaster@krl.org" <dcaster@krl.org> wrote:>On Tuesday, March 14, 2017 at 8:51:22 PM UTC-4, k...@notreal.com wrote: > >> >>> Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible. >> >> >> >> Electrically, tubes are harder to bust... >> > > >> Weeks? MTBF of 336 hours? You can't aford a tube's filament current? >> GMAFB I guess you never turn on a light bulb, either. Heaven forbid >> that you would make diner! > >When I was in the Navy I had a mk 37 gun fire control system to maintain. The radar used a fair number of vacuum tubes. When the 5 inch 38 guns were fired the radar would go down after about two salvos because some tube had failed. So the system had a MTBF of about 5 minutes or less.You're not supposed to aim the guns at the fire control computer!
Reply by ●March 14, 20172017-03-14
On 2017-03-15, rickman <gnuarm@gmail.com> wrote:> On 3/14/2017 8:23 PM, whit3rd wrote: >> On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote: >>> On 3/13/2017 4:26 AM, oldschool@tubes.com wrote: >>>> I've been looking into buying an Audio Generator (Sine and Square Wave). >>>> I mainly want this to run thru an amplifier to listen to... >> >>> I haven't read all of the posts in this thread, but I see a lot of >>> confusion of the terms "function generator" and "audio generator". >>> Audio simply refers to the frequency range of the signal generated >>> without saying anything about the manner in which it is generated. But >>> most signal generators output a sine wave and perhaps a square and >>> triangle wave. >> >> That's incorrect; most inexpensive signal generators output a square and >> triangle (hey, it only takes two op amps); adding a sinewave is complicated. >> To do a GOOD sinewave, the old HP20x units had matched pairs of adjustable >> capacitors, which are VERY pricey items. >> >> So, the iCL8038 and XR2206 and some other IC generators (which dominate >> the market at the low-cost end) distort and/or filter the triangle wave to make >> a "sinewave". The sinewave outputs are dreadfull. > > So they *do* produce a sine wave?curved: yes a sin(2 pi f t + phi ): no.>> For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital >> sythesizers are good, too. Neither is convenient for a test bench, though. > > I'm not clear on what you consider inconvenient, but you don't need much > space to create a decent sine wave. I produce a board with a stereo > CODEC and during test it produces a sine wave that I can't visually > detect and defects in at any resolution. If I removed the application > specific items and gave it a useful PC interface it could sell for maybe > $50. It would have perhaps $20 worth of parts and could fit in an > Altoids tin easily. I believe there are similar products on eBay which > sell for less.there's probably a free signal generator app that will run on that $10 cellphone mentioned in the scope camera thread. -- This email has not been checked by half-arsed antivirus software
Reply by ●March 15, 20172017-03-15
On 3/14/2017 9:24 PM, whit3rd wrote:> On Tuesday, March 14, 2017 at 5:52:48 PM UTC-7, rickman wrote: >> On 3/14/2017 8:23 PM, whit3rd wrote: >>> On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote: > >>> So, the iCL8038 and XR2206 and some other IC generators (which dominate >>> the market at the low-cost end) distort and/or filter the triangle wave to make >>> a "sinewave". The sinewave outputs are dreadfull. >> >> So they *do* produce a sine wave? > > Not a sinewave suitable for a set of test results that can be easily analyzed. The > "sinewaves" have all the harmonics of a triangle wave, but at lower amplitude, and this > is accomplished with hand-tweak adjustments. > > If/as you want to test an amplifier for distortion, that 'sinewave' is not pure enough to use. > >>> For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital >>> sythesizers are good, too. Neither is convenient for a test bench, though. > >> I'm not clear on what you consider inconvenient, but you don't need much >> space to create a decent sine wave. > > What is inconvenient, is that one cannot dial the frequency with an analog knob, while > listening for room resonances or speaker-crossover blips. A DDS solution will have to > be programmed to do a sweep, and reprogrammed if you want to check that one > part of the range that sounded odd... or at least, that was how the old Agilent DDS > worked.You mean like this? http://www.etc.sk/index.php/en/products/auxiliary-equipment/control-panels/item/136-control-panel-for-usb-oscilloscopes.html -- Rick C
Reply by ●March 15, 20172017-03-15
On 14/03/2017 13:58, tabbypurr@gmail.com wrote:> On Tuesday, 14 March 2017 09:22:05 UTC, Martin Brown wrote: > >> There used to be old school analogue function generator chips that >> made a triangle wave and then applied diode shaping to get a >> pseudo-sine wave. HP made one design implementation that was >> surprisingly good. Intersils 8038 was the poor mans alternative for >> DIY. >> >> http://www.intersil.com/content/dam/intersil/documents/icl8/icl8038.pdf > >> > I built one of those decades ago. What a car crash. The wave forms > were hopeless. I don't remember the details to know why, I presume > the problem was the 8038 though.It was never anything like as good as a Wein bridge sine wave but it was good for about 0.5% THD if you trimmed it properly. I suspect manufacturing tolerances made it inconsistent batch to batch. Cute chip in its day, but that was a long time ago. -- Regards, Martin Brown
Reply by ●March 15, 20172017-03-15
On 3/14/2017 9:21 PM, Jasen Betts wrote:> On 2017-03-15, rickman <gnuarm@gmail.com> wrote: >> On 3/14/2017 8:23 PM, whit3rd wrote: >>> On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote: >>>> On 3/13/2017 4:26 AM, oldschool@tubes.com wrote: >>>>> I've been looking into buying an Audio Generator (Sine and Square Wave). >>>>> I mainly want this to run thru an amplifier to listen to... >>> >>>> I haven't read all of the posts in this thread, but I see a lot of >>>> confusion of the terms "function generator" and "audio generator". >>>> Audio simply refers to the frequency range of the signal generated >>>> without saying anything about the manner in which it is generated. But >>>> most signal generators output a sine wave and perhaps a square and >>>> triangle wave. >>> >>> That's incorrect; most inexpensive signal generators output a square and >>> triangle (hey, it only takes two op amps); adding a sinewave is complicated. >>> To do a GOOD sinewave, the old HP20x units had matched pairs of adjustable >>> capacitors, which are VERY pricey items. >>> >>> So, the iCL8038 and XR2206 and some other IC generators (which dominate >>> the market at the low-cost end) distort and/or filter the triangle wave to make >>> a "sinewave". The sinewave outputs are dreadfull. >> >> So they *do* produce a sine wave? > > curved: yes > a sin(2 pi f t + phi ): no.Under 1% distortion when tweaked. I don't think our op would notice. Mikek --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
