--------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00005 Date: 06/26/97 From: TERRY SMITH Time: 07:38pm \/To: ALL (Read 0 times) Subj: Most common cassette tape type After reading comments here on cassette tape, I'm reminded that the most common tape type universal to so-called serious audiophiles and to blue light special shoppers alike is "Type BS". Type "BS" tape has every characteristic ideal for your immediate need. It may cost under 35 cents per cassette, and include hours of recording time. OTOH, it may cost such absurdly high amounts one would question the sanity of anyone buying it to even use the old Norelco format tape, except among testosterone overdosed ego stroking competitors inclined toward similar lunacy on nights without full Moons. Type "BS" cassettes always include specific, finite technical specs which may be quoted at will to prove how good or poor they are for specific uses. Complicating fine print comparing frequency and operating level dependant distortion, headroom, bias noise, and other traits never need be included for numbers tossed out in tenths of a dB to be both precise and accurate when all test conditions and hardware references are ignored. Type "BS" cassettes are optimized for all user preferences. That includes portable machines bearing the name "Crown" not related to the Indiana company which stopped producing tape recorders decades ago, equally with machines bearing names like Studer or Nakamichi. Use of Dolby B, C, SR, DBX-II, no NR, or mismatched bias and Eq make no difference, nor does operating with meters held 20 dB below saturation or always off the red. Dolby HX Pro has no effect on effective headroom, distortion, or s/n, as Type "BS" tape is ideal for all user choices. ================================================= Bonnie of course gave a somewhat valid suggestion, that anyone having to ask what the best tape types are should pay to have equipment aligned to a few suitable choices suggested by more technically astute persons, and just stick to those. Not a very specific answer, but about the only one simple enough for average consumers as a general response. No one here mentioned that typical "chrome" tapes, which for a decade or more have often been modified ferric media simply optimied for the "chrome" high bias levels (which affect recording only) and 70 uS Eq (rec or PB), have higher typical audio distortion at operating levels than comparable quality ferric cassettes. This distortion spec is typically about 50% higher on chrome, in exchange for typically better high end headroom. The latter may yield lower perceived distortion (as well as high end loss) on some material, by keeping audio less often into saturation, even on tape with a higher distortion spec at typical single reference test conditions. On other material such advantages may be moot, and the ferric spec's may be preferable. A number of dynamic range specs were tossed out, and little mention was made of tape quality. To start with, some comments equated ferric (Type I) tape with traits which might include poor surface finish, marginal slitting tolerances, and junk shells. That's simply not true, as any tape type can be well or poorly made in such respects. In addition, different vendors may have typical physical tolerances which are not identical, another reason why use of a limited number of brands and models often gives better performance on specific equipment than mixing randomly nominally similar products. There's no such thing as Type I tape having 58.5 dB dynamic range and Type IV tape having 75 dB by virtue of the labels. Those are funny numbers, and are based on test conditions that include filters to alter direct measurements, as well as operating modes that are not direct indications of tape performance alone. In addition, they ignore the variations of up to 15 dB in saturation levels and noise at various frequencies of different brands and models of same nominal type tape from various vendors. It takes about 2 full pages of detail to list the real basic specs of any given tape type, usually with slight differences in references not always fully comparable if comparing Ampex, Agfa, 3M, BASF, Maxell, Sony, TDK, etc. Then there are tapes with packaging of various duplicator products with the same markings, sales of minor manufacturing rejects, and other such econo and marketing hype lines that can be impossible to compare without batch testing every single batch of product. Even major quality vendors have a bad run now and then. Anyone ready to use about $20,000 of test equipment and labor can easily develop some rational reasons for picking specific tape types comparatively. Others get to rely on trusted advice from dealers or magazine labs which may do such testing, or personal arbitrary perceived experiences. Terry --- Maximus 2.01wb * Origin: Do it near resonance! (203)732-0575 (1:141/1275) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00006 Date: 06/26/97 From: TERRY SMITH Time: 08:21pm \/To: KEITH KNAPP (Read 0 times) Subj: Isolation Transformer KK> I also built the phono preamp right into the turntable -- them KK> teeny little wires come right out of the arm and into the chip. In Europe a studio turntable is often a package that includes a line level output, and even cue/monitor amp. In the US pro- TT's usually are just motors with platters, with mounting, arms, and electronics separate and up to the user. Preamps with line outs (+4 balanced) are usually located just below the arm though. It's only in cheap home (and some semi-pro) systems that phono preamps are part of other electronics. That assumes that the whole system won't be spread over more than a couple feet, and often compromises other design traits. Terry --- Maximus 2.01wb * Origin: Do it near resonance! (203)732-0575 (1:141/1275) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00007 Date: 06/26/97 From: TERRY SMITH Time: 08:54pm \/To: DAVID SCHMOLL (Read 0 times) Subj: system balancing DS> I just read some information about system PA balancing, in some DS> information from Apogee, that I never thought about before, which made DS> me realize I probably have been adjusting things wrong all these years DS> if I'm to believe what I just read. Giving summary impressions first, it sounds like you read some silly marketing BS, with some slightly confused suggestions that aren't quite right outside being helpful simplified procedures within some possible context you didn't describe as being detailed in what you read. Overall, Bonnie's comments on balancing sound output are more realistic. DS> The article dealt with fixed gain on various amplifiers in a system. It Most amp stages other than mic inputs on a board are fixed gain, and levels adjusted with pads of some sort at key points. Functionally, so long as we're not discussing noise and headroom optimization, what's the difference between a 50 dB gain amp preceded by a 0-20 dB pad, and an amp with a variable resistor controlling gain from the feedback loop from 30-50 dB? DS> said all amplifiers have a fixed design gain, and that mixing different DS> amplifiers in a system with different gains would cause mismatched DS> sound. For example: one amplifier might have a gain of 40, which means DS> for a 1 volt input it will produce 40 volts output (assuming it has DS> that much output), while another amplifier can have a gain of 35, DS> producing 35 volts output. There are different vendor standards for producing full rated power at a standard input level like one volt, producing one watt with the same input level regardless of power rating (such that a 1,000 watt amp will need 10 dB more drive for full output than a 100 watt amp), and many variants or arbitrary designs. Within the same segment of the same array, all amps should be operating equally in most cases. If the compromise of defective amps (even if brand new from shoddy vendors, though even Crown has had bad runs now and then) or mismatched brands and models must be made, it makes sense to set them for as similar performance as possible. In an ideal system this can mean setting all knobs on identical model amps within a unit full open or to some standard point, at which all outputs should be the same for the same input (with inputs from the same crossover output or limiter). When this is not the case it means that either something about the equipment is substandard, or that within that band a compromise has been made to run similar speakers and amps on the same crossover but balance different venue areas by adjusting groups of amp inputs for some cluster segments. DS> This suggests to me that the system balance DS> would change as the overall system gain was increased at the mixer. The Not at all. That relationship should be static within other system limits. DS> article stated that the input volume controls on each amplifier needs DS> to be balanced - without speakers attached - so that all amplifiers DS> produce the same voltage output for the same voltage input. Buzz. Ideally all power amps are ideal current sources. In practice they all have some design source and optimum load impedance based on rail voltages, current capacity, and other design limits. Checking for uniform voltages might better be done to compare amps with all speakers connected, within a single bank of a given frequency, throw depth or coverage area, etc. Ideally all amps within such a cluster segment should be same brand and model, as they may have various differences in impedance, phase performance, etc. Good amps should at near full power change voltage little if you lift speaker loads, while less capable ones may rise in voltage without speaker loads. These changes if present may also be nonlinear with volume. If possible you stick the junk amps someplace else where they stand alone, in less critical applications. DS> efficiencies. For example: a bass speaker might have a 96 db rating at DS> 1 watt, while a midrange speaker might have a 98 db rating at 1 watt. I DS> would adjust this 2 db difference at the power amplifier, so that my EQ DS> setting would stay closer to a straight line across the bands. With the DS> matching of gain concept, the EQ curve would reflect the speaker DS> efficiency differences, as well as the room itself, in other words, in And mid/high horns might have much higher efficiency than that (I'd think front loaded mids would too, coverage dependant), as well as different bands having different power allocations. Obviously feeding some 120 watt horns 800 watts is absurd before even considering system balance. DS> My question is, is the gain matching I described really as important as DS> Apogee makes it sound, and are my conclusions correct? In my home There's got to be some fine print missing, which taken out of context (which may not be accurately described) is wrong. DS> theater system, I have an Adcom 545 running a (mono) pair of JBL DS> subwoofer's, an Adcom 535 running the (stereo) JBL main speakers, an DS> Adcom 535 running the (mono) center and (mono) rear channels. With 4 DS> distinct speaker sytems, each with different efficencies, and 2 models DS> of power amplifiers, with unknown gain and no volume control to adjust DS> on thte amplifier anyway, I can't test out this theory, but on the If you were talking about setting power amp gains to be uniform using existing (or other unknown source amps) in a home multi-channel full range system with uniform speakers and Apogee supplying the line level decoder, what you described could make sense. In any commercial system, or the home theater with mixed speaker types, it's absurd. Terry --- Maximus 2.01wb * Origin: Do it near resonance! (203)732-0575 (1:141/1275) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00008 Date: 06/26/97 From: TERRY SMITH Time: 09:29pm \/To: BONNIE GOODWIN (Read 0 times) Subj: system balancing BG> FIRST. One one side of the line, you have everything that you want to BG> feed the power amp/loudspeakers which is selected FIRST to deterime BG> coverage issues and having large enough/enough drivers to adaquately BG> cover that area with even sound, then you can look at how much power and BG> amplifier channels one needs to appropriately adjust these levels, BG> assuming no overworked drivers or amplifiers for sufficient headroom. At I'd like to be able to generate 10+ KW of acoustic energy (NOT amp power ) from 8 Hz through 5 KHz, tapering down to 1 KW of acoustic energy at 25 KHz, within an area the size of a 500 person hall. Care to try that goal, and more importantly, dare to venture in during an experiment in mind control through sound stimuli, audible and otherwise? <> I want this done efficiently, as you're limited to 1200 amps of 208 V 3 phase, including lower power incidental equipment for the hall. ;-) Square or sine waves shall be reproduced accurately within some absurdly demanding criteria we can develop. alt.sex.torture regulars can be SPAMmed as potential customers. ;-/ BG> At that point, then everything is handled from the program end of BG> things, the amp/speaker system is a backburner item, now. Plug in your BG> program sources and get creative!! Speaking of creative designs, have you ever had the chance to play with one of those theater/auditorium reinforcement systems designed to prevent regenerative feedback by using 100 plus drivers staggered around the audience, and computer switching which drivers are active quickly enough so that any given feedback path based on phasing and room quirks never has time to develop after space delays are included? Terry --- Maximus 2.01wb * Origin: Do it near resonance! (203)732-0575 (1:141/1275) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00009 Date: 06/27/97 From: PHIL ROBERTS Time: 03:04am \/To: DON DELLMANN (Read 0 times) Subj: Swapping Turntables -=[ Quoting Don Dellmann to Phil Roberts ]=- PR> I'm thinking of ripping out the old turntable entirely and installing PR> a more modern automatic turntable, maybe a single-play unit. This PR> would also mean adding a preamp for the magnetic cartridge. DD> From what you've said so far, I think your MIL would be unhappy with DD> a single play, she's gonna want a changer. The only problem you'll DD> have, is you will have to take out the original mounting plate, and DD> cut a new one (there should be a template with whatever unit you buy), DD> in consoles like this, usually 1/4" plywood. Actually this old thing is pretty massive, might be more like 1/2" plywood. Single play should be OK, as her other system has a single-play table on it. I can't say much nice about the electronics in the cabinet though. I'm wary of anything that has a "tone" control on it. That's a high-cut filter, kind of unnecessary on a box which can't produce any highs. Automatic is a must, as people from the steel-needle generation are really hard on the stylus and don't use the cueing lever! I think I have a lead on an old Garrard that's barely been used...which would be a great table for this system and is convertable between single-play and stack by changing the spindle. Phil --- Bink/Max/GE 1.20 Pro * Origin: Analytical Engine CBCS * 28.8k BPS * [216] 942-3876 (1:157/554) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00010 Date: 06/27/97 From: DAVID SCHMOLL Time: 08:23am \/To: TERRY SMITH (Read 0 times) Subj: system balancing Hi Terry, TS> Giving summary impressions first, it TS> sounds like you read some silly marketing TS> BS, with some slightly confused TS> suggestions that aren't quite right outside TS> being helpful simplified procedures TS> within some possible context you didn't TS> describe as being detailed in what you TS> read. Overall, Bonnie's comments on TS> balancing sound output are more realistic. Actually what I described was from a booklet from Apogee called sound reinforcement for worship, written by the Director of education and senior systems engineer of Apogee, Patrick Price. The section on matching all amplifier gains in a system was something I had never seen before, and that prompted wanting a second opinion from someone not wanting to sell the church their sound system. :) I'm not in charge of the church sound system, but I am learning about it. The exact text is as follows: Amplifier Gain - Amplifier spec sheets usually list a "gain" or "voltage gain" specification. Gain is usually expressed in decibles (such as +32db) or as a multiplier (such as 40 times). Given an amplifier with a gain of 32db or 40X, this means that the amplifier signal is amplified by 32db or multiplied by a factor of 40. It is important for you to know the gain of all your power amplifiers in order to properly "balance" your sytem at the offset. If you intermix amps with different power ratings or from different manufactures within your system you are advised to check to make sure they all provide the same amount of gain. I should Explain that all power amps run at some fixed gain, regardless of where you set the input level control. It all sounds confusing but the explanation is quit simple. All the amplifier level control does is shunt a portion of the input signal to ground. For example, if you connect a 1 volt signal to an amplifier with a gain of 40X you will get 40 volts out (assuming the amp can deliver that much power). However if you leave the same 1 volt signal connected and turn the amplifier's gain control half way down, you will have reduced the 1 volt signal down to 1/2 volt. But the half a volt will still be amplified by a factor of 40, and you will get 20 volts out. The amps's gaian is still 40, but you have shunted half the input signal to ground. The point you should be concerned with is that if you use an assortment of power amps in your system, and your high frequencies are amplified by a factor of 40X, your mids are amplified by a factor of 45X, and your lows are amplified by a factor of 35X, The high/mid/low balance through the speakers will be severely messed up. To properly calibrate a sytem using amps with different gains you must use the gain controls on the amps to match their output levels (given the same input) to that of the amp(s) with the lowest specified gain. Start by putting a 0.5 volt 1kHz sine wave signal into each amp (no speakers connected), and use an AC volt meter to measure the output voltage with the gain controls all the way up (write each output voltage down as you go). When your done, mark the amp(s) with the lowest output voltage (meaning lowest gain) as your "reference" amp. Now go through the remaining amps once again using the same 0.5 volt input signal and adjust their gain controls so that the output voltage matches that of the reference amp. ---- I attempted to say the same thing in less words in my original post, so the question remains is the above valid or hype? I can't see how not including the speaker efficiencies in the overall balance makes sense. ... dschmoll@nyx.net (David Schmoll) ___ QWKRR128 V5.0B [R] --- Platinum Xpress/Win/Wildcat5! v2.0 * Origin: The NeverEnding BBS/Deltona,FL/407-860-7720/neverendi (1:3618/555) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00011 Date: 06/26/97 From: BONNIE GOODWIN Time: 09:05pm \/To: GEOFF CONDICK (Read 0 times) Subj: Nothing much Hiya Geoff! I'd love to hear more about your Excel spreadsheets for speaker system design! Bonnie *:> --- QScan/PCB v1.18b / 01-0249 * Origin: The Capitol City Gateway, Since Dec 1979, 916-381-8788 (1:203/909) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00012 Date: 06/26/97 From: BONNIE GOODWIN Time: 09:04pm \/To: CAMERON HALL (Read 0 times) Subj: Re: Website for AUDIO Hi Cameron! I think we both agree that tubes are highly ineffecient, and rediculous to use in digital audio.. That tubes were used in early computers is in itself quite funny by today's standards. Bonnie *:> --- QScan/PCB v1.18b / 01-0249 * Origin: The Capitol City Gateway, Since Dec 1979, 916-381-8788 (1:203/909) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00013 Date: 06/27/97 From: NANCY WOOD Time: 03:15pm \/To: TERRY SMITH (Read 0 times) Subj: Most common cassette tape type * Replying to a message originally to All on 06-26-97 TS> After reading comments here on cassette tape, I'm reminded that TS> the most common tape type universal to so-called serious TS> audiophiles and to blue light special shoppers alike is "Type TS> BS". Maybe Bonnie will post her .faq's on Cassettes! . If she no longer has 'em, I think I've got mine floating around here somewhere (mine being those messages from her that I imported to text files.) Nancy --- FMail 1.02 * Origin: Electronic Avenue BBS 210-533-5668 San Antonio, TX (1:387/510) --------------- FIDO MESSAGE AREA==> TOPIC: 183 AUDIO Ref: EAY00014 Date: 06/27/97 From: JOHN ALLEN Time: 11:52pm \/To: DAVID SCHMOLL (Read 0 times) Subj: system balancing Hello David, Short and sweet: Yes. But to what degree is up for discussion. Cheers, John --- Maximus/2 3.01 * Origin: The Union Jack BBS, Phoenix, AZ, USA. 602-914-4162 (1:114/260)