An amp on top of speakers is not a good place, especially a tube amp, they are better off on the floor (vibration control). The skin affect at audio frequency's is not worth worrying about especially with just a two foot run but a quality solid conductor cable will certainly do the job.
Math + Logic + Science = something completely mad...
So, I've done a metric fuckton of research, notwithstanding the clear bias the man who designed and built my Belles has against esoteric cabling. And here's the conclusion to which I arrived.
My monoblocks are sitting on top of the speakers. The distance from the amp to the speaker is barely a foot, which is exactly how long a run of wire I intend to use. Goal is to minimize the effect the wire has on the sound.
According to the calculations I've seen and done, the skin effect depth on copper wire at 20Khz is 461 micrometers. Meaning a 19-gauge copper wire (911 mics diameter) would reduce skin effect to zero. As in no impact whatsoever on the signal.
Of course, it's actually very difficult to find 19-gauge wire. 18-gauge (1024 mics) is much easier, and the skin effect is near zero, but not quite zero. Seems to be an acceptable compromise. Could go down to 20-gauge and eliminate skin effect entirely. If I could find insulated aluminum wire, 18-gauge would eliminate skin effect entirely, because skin effect depth on aluminum at 20khz is 580 mics.
12 inches of 18-gauge wire produces 0.006 ohms of additional resistance. 20-gauge = 0.01 ohms.
Frankly, I don't see the value in spending big bucks on esoteric, heavy-gauge wire for this application. I'd rather make the bigger investment in the 2m runs from the preamp to the blocks, because that's where the wire's going to have a hell of a lot more of an effect on the sound.
Stepping back to allow you all the opportunity to punch holes in my thought process here.
My monoblocks are sitting on top of the speakers. The distance from the amp to the speaker is barely a foot, which is exactly how long a run of wire I intend to use. Goal is to minimize the effect the wire has on the sound.
According to the calculations I've seen and done, the skin effect depth on copper wire at 20Khz is 461 micrometers. Meaning a 19-gauge copper wire (911 mics diameter) would reduce skin effect to zero. As in no impact whatsoever on the signal.
Of course, it's actually very difficult to find 19-gauge wire. 18-gauge (1024 mics) is much easier, and the skin effect is near zero, but not quite zero. Seems to be an acceptable compromise. Could go down to 20-gauge and eliminate skin effect entirely. If I could find insulated aluminum wire, 18-gauge would eliminate skin effect entirely, because skin effect depth on aluminum at 20khz is 580 mics.
12 inches of 18-gauge wire produces 0.006 ohms of additional resistance. 20-gauge = 0.01 ohms.
Frankly, I don't see the value in spending big bucks on esoteric, heavy-gauge wire for this application. I'd rather make the bigger investment in the 2m runs from the preamp to the blocks, because that's where the wire's going to have a hell of a lot more of an effect on the sound.
Stepping back to allow you all the opportunity to punch holes in my thought process here.
62 responses Add your response
An amp on top of speakers is not a good place, especially a tube amp, they are better off on the floor (vibration control). The skin affect at audio frequency's is not worth worrying about especially with just a two foot run but a quality solid conductor cable will certainly do the job. The floor is not an option (space issues), and they are sitting on heavy dampening mats. |
| Post removed |
running a short piece like that is going to act more like a light bulb than a speaker wire.I don't get how you arrive at this conclusion. Again, 12 inches of 18 gauge wire adds a net of 0.006 ohms of additional resistance to the signal. Also, light bulb filament is a mere 46 micrometers - it doesn't even rate on the AWG scale, the smallest gauge being 38AWG (100 micrometers). Care to explain the science behind your declaration? |
Wouldn’t the wire at least get warm if you played it at a continual hundred watts?Report this Two part response here: 1) These are 25-watt monoblocks going into horn-loaded loudspeakers. So they will never see 100 watts. Not even at peaks. 2) Heat generation is directly proportional to resistance and current. More resistance + more current = more heat. The amount of current flowing through a speaker wire is laughably small, even with big SS amps. And further, if a small-gauge speaker wire was at risk of catching fire at 100 watts, you'd have to think that the much tinier wires on the other end of the speaker's crossover would instantly burst into flames, because they're typically 24AWG or smaller. |
NO. Setting amps on speakers. NO. 18 gage cable. NO. skin effect If you don’t have the room for the amps come up with a different plan. A good 8 - 16 strand OCC/silver clad PTFE weave up to 3 meters long will work perfect. Red copper or copper/silver terminal ends. (B-16) is an option. OCC or OFC 8-24 strand weave PTFE is another. No idea where you got your information.. We’re not rewiring a toaster or an ARC welder. The RIGHT kind of cable selection goes a long ways as far as "How does it Sounds". You’ll squeak out some sound with #18 all right.. :-) The cable I’m talking about sells for 250 - 3500.00 +. Depends on who’s name is on it.. They actually cost about 150.00 usd. Delivered.. and put together pretty well if you want someone else to do the work.. Second option is a ribbon design.. Same price very close in SQ to Norcast Vanilla. They make anything sound as good as it’s gonna get.. Ribbons and weaves are really really good cables for the money. GREAT cables are very affordable, LOL so are BAD ones.. Time to feed the chickens.. Regards |
Can you provide a picture of your setup? Sure. https://pbs.twimg.com/media/E0JH7A2XsAcv-Zj?format=jpg&name=small Mats and interconnects are still en route, hence why I haven't powered them up yet. |
Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers. Your short 18 awg cables will work perfectly of course. The resistance is but a minuscule fraction of the speaker impedance. Following that short 18awg is a ton of wire in the cross-over, followed by a lot more small gauge wire in the voice coil. The variation in the resistance in the voice coil due to thermal effects is far more than the total resistance of that 18awg. Virtually every negative reply you will get will be hand-waving with no quantification as you have done. Keep in mind the wire is 2 lengths, resistance will be closer to 0.016 ohm. That will be consistent with virtually no thermal modulation. It is likely a very small fraction of the output impedance of your amplifier too. At 20KHz, the impedance will be up to 0.022. You did miss one critical element though, inductance. That will be the dominating factor. That will increase the impedance to 0.08 - 0.1 ohm by 20KHz. You won’t hear it, but it will be there. Skin effect is rarely an issue. Inductance can be. |
Skin effect is rarely an issue. Inductance can be. Only reason I bothered with the math on skin effect is because so many of these esoteric high-end cables do random weird stuff like adding dielectrics to "phase-correct" the signal. Of course, over 1-2 feet of wire, I doubt seriously that the signal could possibly get "out of phase" enough to be audible anyway. Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers. So you're saying that the speaker vibrating the amp will cause microphonics in the tubes? Or is there a concern about proximity to the magnets? Certainly I could build shelves, that's an easy thing. I'm just trying to make sure I understand the problem I'm trying to solve here in order to solve it correctly. If you don't mind, I'd love for you to go over the science with me here. |
So you're saying that the speaker vibrating the amp will cause microphonics in the tubes? Yes Only reason I bothered with the math on skin effect is because so many of these esoteric high-end cables do random weird stuff like adding dielectrics to "phase-correct" the signal. They say a lot of things that are not true. That is why they never provide any useful information. If they provided useful information, no one would buy them. |
While I believe that cables matter, skin effect is the biggest piece of hogwash ever. A more likely explanation for cables sounding different, based on what I've heard, is that the amp and speakers are more sensitive to the miniscule LC and R values than the math would have us believe. Perhaps feedback also plays some role here, but 100% of every cable effect I've ever heard can be explained purely in the frequency domain. Oversensitivity to basic cable measurements could explain it. Also, most cables are way pricier than the apparent changes they produce. |
A more likely explanation for cables sounding different, based on what I've heard, is that the amp and speakers are more sensitive to the miniscule LC and R values than the math would have us believe That's an explanation I can probably buy into a lot easier than idiotic jibberish like "time-correct windings". So now I'm thinking some basic 12-gauge Belden with some nicely welded spade ends from Blue Jean Cable is the correct answer here. One point was made in an article I read the other day that I had never contemplated, but certainly could appreciate, is that copper wire certainly does corrode over time, and some appreciable difference can be achieved just by replacing it with new periodically. No matter what the new cable is, it'll sound better than the old one, because it's new, clean copper. Fast forward a couple years and it's no longer new and no longer clean, and it'll need replacing again for optimal results. Which makes whatever miniscule gains that one could make spending $5K on a pair of one-meter runs kind of absurd, considering those gains will disappear over time from plain old, natural copper degradation. I can show you a photo of some Monster wire (that was given to me by the gentleman who sold me my Belle Klipsch) that is 10 years old and thoroughly green *inside the insulation*. |
"...Even when the amp has isolation feet on it and the speakers are sitting on a concrete floor, which is the ultimate vibration sink?..." The amp designer has done what they can do to reduce airborne microphonics (chassis resonances) but mechanical resonances from placing amp on vibrating surfaces will smear the sound sometimes and should be minimized as much as possible. |
| Post removed |
So now I'm thinking some basic 12-gauge Belden with some nicely welded spade ends from Blue Jean Cable is the correct answer here.
<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>> Yes and if you can manage, cold press the ends, no solder. Treat the bare wire before you install it into the bore with a good enhancer. Graphite dust works great. If you have to solder, use GREAT solder, that is another boo boo, people make. They solder ends instead of tinning and using and enhancer with a cold press or HEAVY hammer strikes will work. 20-30 tons with 2 of my hammer strikes.. 2 strikes with a 6 pounder will do.. One to set the cable and a second to cold weld them.. Up to 2.0 gage.. Hammer strikes.. Yup... Bla bla Bla.. 18 gage is perfect.. Not in this lifetime.. 40 watt reading light.. SOUND not appliances... Not anywhere close to the same application... Regards |
@jerkface - have you considered wire type, wire material, insulation?. Wire type: solid wire is far superior to stranded wire Wire Material: UP-OCC solid Silver is best, but to keep it reasonable then use UP-OCC solid copper Insulation has an impact on the signal, so you should look at getting as close to an Air insulation as much as possible. NOTE: Insulation acts like a dielectric and there is a measurement called Dielectric Constant, where...
I use cables that are 9ft long and get exceptional sound quality. Take a look at this thread... https://forum.audiogon.com/discussions/duelund-conversion-to-diy-helix-geometry-cabling The last two pages talk about Air dielectric and what others have found when applying this approach There is also mention of power cables and Interconnects that adopt the Helix geometry, materials and insulations mentioned in that post and they work extremely well Cables are far more complex than people believe them to be - it’s NOT as many believe just L, C, R. Regards - Steve |
| Post removed |
Yes and if you can manage, cold press the ends, no solderBJC will assemble your cables for you, doing an ultrasonic cold-weld instead of soldering the ends. Considering I *have* to use either fork or ring terminals on the speaker side, seems more convenient to just let them throw the ends on there for me and call it a day. @williewonka That sounds like a really cool DIY cable. It also sounds like way more time, effort, and expense than I want to endure at the present moment (mostly because I have SO many other things both in my listening space and in the rest of the house where I need to invest time, effort, and expense right now). Maybe I'll get a quote from you to make me a pair of them so I can audition them against the BJC/Belden joints. |
| Post removed |
@dietch2 - well I’ve just spent the better part of the last 4 years ACTUALLY TRYING all of the things I have mentioned and in that time I have found that EVERY one of the things I mentioned does actually make for a vastly superior cable - regardless of length. How did I measure all of this - with my ears. I have tried cables from 12 ft long to 1 ft long and YES the incorporation of the adaptions I suggested made a noticeable improvements, not only in high end gear but budget systems also MY PROCESS: I would change just one thing each time and make note of my observations. So I’m not disputing what you say - you seem very educated - I’m just stating what I have observed to make a noticeable difference Regards - Steve |
| Post removed |
Its transmission line effects, which don't matter in audio. It is skin effects, which are easily accounted for. It is triboelectric effect which is virtually never an issue in audio. It is E Its transmission line effects, which don't matter in audio. It is skin effects, which are easily accounted for. It is triboelectric effect which is virtually never an issue in audio. It is EMI, not an issue with 12" speaker cables. MI, not an issue with 12" speaker cables. I had this sneaking suspicion he was trying to mitigate skin effect when he started talking about dielectric. But I was also trying to be jovial and open-minded when he described all the effort he went through to build these cables. @williewonka Literally, at the outset of the discussion, I showed the math regarding 18 and 20-gauge normal speaker cable and the skin effect at 20Khz. Yet somehow you blew past that. I don't get why. |
Literally, @williewonka , there's a calculator for skin effect depth out there. https://chemandy.com/calculators/skin-effect-calculator.htm Skin effect at 20Khz on standard copper wire is 461 micrometers. Which means a standard copper wire with a diameter of 922 micrometers, just short of 1 millimeter, will show zero skin effect. Nada. Zilch. No dielectric needed. And then I showed the math on the net resistance of 18-gauge copper on a 12-inch run, which is 0.006 ohms. But frankly, I don't see how skin effect on a 1 or 2-foot run of wire is going to make any difference at all in the output signal. We are talking about a signal velocity approaching the speed of light. There isn't time in two feet of wire for the difference between HF and LF information to become out of phase at that velocity, even if the wire was 2-gauge battery cable, because comb filtering from phase cancellation doesn't even start happening until you get above the 20ms range. But I did the math on skin effect for precisely that reason - so that anyone who believed in skin effect could see that, indeed, there would be zero skin effect with minimal additional resistance on the length of wire involved in this deployment if I took the path of small-gauge wire. At some point here in the near future, I plan to have a conversation about interconnects, which will be much more in earnest, since the distance increases to 2 meters, and the current, as a line level signal, is FAR lower, which I believe makes it more susceptible to the various and sundry electrical effects we're discussing here. I'm open to being convinced of otherwise, however. But I'm a lot more open to a wider variety of solutions to that particular conundrum, and more willing to spend on solutions that make sense. Operative being "make sense", as in show me the math, show me the science, show me where we are on the perpetually diminishing returns scale, so I can make an intelligent decision about whether it's worth it. Pro tip: You'll be hard-pressed to convince me that it's worth it in the 4-figure range. |
Totally looney to put big amps on speakers. For all the valid and good reasons stated above. If space is at such a premium, why not hang the amps on wires from the ceiling so they sit in the air just 1cm above the top of the speaker. But @jerkface does make one interesting point: " We are talking about a signal velocity approaching the speed of light." This must be correct. So how come whatever wire you use can make a big difference to SQ. Especially for @jerkface who employs extremely short runs. |
| Post removed |
@jerkface - You seem to have misinterpreted my postings somewhere along the way, since I have made NO mention about Skin effect in any of my posts And for the record - I do not consider skin effect to be an issue in the audio bandwidth of 20-20kHz. But for everyone's edification, here is just one web site that I encountered during my investigations into dielectric materials - and they have far more experience in cable building than myself LAB: Comparing Dielectric Effect Distortion to Jitter (anticables.com) But in order to avoid a long read - here is an extract When the music signal flows through a cable, the dielectric material (insulation) around the wire absorbs some if this magnetic energy, but then re-releases it back into the wire slightly later in time. This time smearing of the music signal is called dielectric effect distortion. Both this and jitter distortion collapses the sound stage, makes the music sound hard and closed in, and reduces dynamics making the music sound lifeless and un-involving To complicate things further - consider the effect it has on what we hear from a two channel system - those distortions present minute differences in phase between L and R channels - these impact imaging, clarity and dynamics Will this impact a 12" cable? - I found it was discernible on my system So that's about all I have to contribute to this particular thread I wish you well in your endeavors to find your Nirvana Signing off - Steve |
| Post removed |
| Post removed |
Jitter for one is bidirectional. It causes harmonic distortion and uncorrelated noise.I'm not sure what "bidirectional" means. Do you mean "sidebands"? Jitter does not cause harmonic distortion and that's the reason why is still audible in spite of very low levels. Jitter only produces additional frequencies NOT harmonically related to root frequency. Yes, it is causing noise, but it can be correlated, uncorrelated or both. Uncorrelated jitter is a little less audible. Correlated jitter is less audible when sidebands are closer to root frequency (frequency causing jitter is low). It appears that according to numbers nothing in cables should be audible. Skin effect, that starts at gauge 18 causes extremely small impedance change at 20kHz - frequency that I cannot even hear and where most speakers (being inductive) have high impedance. Capacitance plays very little role in speaker cables and the same goes for dielectric absorption. Inductive reactance, assuming both wire gauge and wire spacing of twisted pair to be 50mils, would be in order of 0.1ohm at 20kHz and 0.05ohm at 10kHz (that I can hear). So, according to numbers, nothing should matter and all speaker cables should sound the same. The problem is that they don't. Perhaps audio, like women, is meant to be loved, not to be understood? |
| Post removed |
dletch2, I remember long time ago I had inexpensive cable from Best Buy. I believe it was Monster Cable brand. It consisted of two parallel runs of very thick stranded wire in thick clear plastic (most likely PVC) insulation. It was suppressing high frequencies to a such degree that I had to add few dB of the treble on my receiver. Later I replaced this cable with AQ Indigo and magically treble came back (everything else being the same). Indigo was OK, but Acoustic Zen Satori that replaced it is in different league. What surprised me the most was lower midrange (cello, chestiness of male voices) that got fuller. In comparison Indigo sounded thin. I would not even try to express it in electrical terms. Since then everything else changed in my system for the better, but speaker cable is still the same. My hearing was not that good because of age, but I could still hear a difference between AQ King Cobra and Acoustic Zen Absolute interconnect that replaced it (foam Teflon, oversized tubes, Zero Crystal silver). It is cleaner, faster, darker background, more instrument separation. Why? Is it because of insanely good specs (6mohm/ft, 6pF/ft, 20nH/ft)? Calculations would likely suggest that both interconnects should sound exactly the same, but they don’t. AudioQuest FAQ explains logic behind helical twist on oversized air tube. They stated that in order to avoid skin effect wires have to split into separate insulated strands, but then skin effect still applies since they are in magnetic field of each other. Remedy for that is to place them on the tube. That way each wire is only in magnetic field on neighboring strands. In addition it is interleaved with return wires to reduce inductance and twisted to reduce electrical pickup. That is exactly how my Acoustic Zen Satori is made. Different companies and the same design? Are they all doing it for show? Is it snake oil? I have pretty good understanding of electronics, but getting much deeper into something requires different expertise. I believe that we don’t even comprehend exactly the nature of electrical current. We know that it is motion of electric charge, but how energy can be delivered to load if exactly the same amount of electrical charge comes back by return wire? Why energy flows toward load while AC electric charge flows back and forth? Energy has to flow differently and it does - by magnetic filed outside of the wires (Poynting Field). Do we now understand everything? I remember some horrible amplifiers in 70s that had extremely low THD and IMD (achieved by deep negative feedback) and sounded bright and tiring. Later Transient Intermodulation (TIM) distortions were discovered. That makes me believe that trusting my own ears and cable companies is perhaps better than trying to make sense of it. I selected Acoustic Zen instead of AQ because it is better bang for the buck, IMHO. |
| Post removed |
So how come whatever wire you use can make a big difference to SQ.Because, as I've said elsewhere, there's no such thing as "perfect" wire. Just trade-offs. More inductance in exchange for lower resistance and capacitance. Less inductance in exchange for more capacitance. Even the insanely expensive stuff still trades one problem for another. How big the problem is and how much it affects your system is what will make one cable sound better than the other. But it also means, depending on the application, that a $25K cable will be outperformed by a $20 one. |
Oxygen free copper is nice to reduce corrosion, but never mind OFC or OCCC failing in blind tests, or silver Silver is a mind-blower for me. Because silver creates its own set of problems in terms of signal conductivity. Sometimes I wonder if there's just an opulence aspect going on there. Like, if a manufacturer thought they could make it cost-effective (for them, not for you), they'd put out a 14k gold wire, just to see if it'd sell. In fact, I seem to recall back in the 80's reading a Stereo Review article about gold speaker wire. But I couldn't say for sure who did it or what purity level it was. |
We end up where we started R, L, C.And now comes the money question. Presuming that I shelve the amps a few inches above the speakers (already bought shelf kits to do this), now I still have my 12-inch speaker cable run, BUT, I still have 2.5 meters between the amps and the pre. So now I have a milliwatt signal being broadcast on a longer run than the high-watt signal between the amp and the speaker. It seems to me that C should be my biggest concern when I contemplate my interconnect choices due to the longer run, though RCA cables tend to be far less transparent regarding their specs than basic speaker cable. Your advice would be useful here. |
dletch2, I'm trying to describe what I hear, while you're saying I have to be mistaken because something like that does not exist. That is my whole point - you're starting from the wrong side, trying to disprove what can easily be heard. You also imply, that I wouldn't be able to tell the difference in blind test. Are you a cable naysayer who tries to fortify it with measurements? Let me suggest, that placebo effect exist both ways - if you strongly believe that you cannot hear the difference you won't. Also, there are people with less then perfect hearing apparatus (I'm not suggesting it applies to you) who get very defensive about it making crusade against cables on cable forum. I'm sure my hearing, even at my younger age, wasn't as good as hearing of many other people and I would never dare to tell them what they can or cannot hear. |
| Post removed |
Use mogami balanced. While I'd love to go XLR for that application, it's simply not an option, because the pre only has unbalanced out, and the amp only has unbalanced in. So it is what it is. Unless Mogami has some fancy way to get the cancellation out of the XLR and still convert to RCA on both sides, then we gotta find a different solution. |
dletch2 Let me get to some technical points first. I brought example of amplifiers in 70s to show that there is always possibility of something we don't know yet. Designers then believed that NFB is a panacea for everything since it reduces THD and IMD, increases bandwidth and lowers output impedance. Some transistor amplifiers had extremely low THD and IMD (few zeros after decimal point) but sounded bad. This deep NFB not only brings TIM but also make amplifier sensitive to external electrical noise, since cable is an antena for RFI. Amplifier's output has low impedance only for low frequencies and it is an input to NFB at the same time. Yes, most likely there is a Zobel network there, but no filter is perfect. We are talking about additional about 40dB of gain in addition to existing about 26dB of amplifier's gain (amp has 66dB of gain before feedback is applied) plus what level down we're able to hear - at least 60dB. Twisting wires makes cable extremely immune to interference by exposing both wires evenly to external magnetic and electric field (as long as twist pitch is much smaller than wavelength of interfering signal). As for blind test - No, I did not perform such test. It happened by chance when after comparing cables I left old one plugged in and next day was able to hear that it didn't sound the way I remember it should. Also, changes in sound (like fuller lower midrange) were unexpected - reviews never mentioned it. I agree with you that we have to be objective, but at the same time I believe that we should be humble and accept that what we hear often cannot be explained (or at least easily explained). |
Keep going back to blind testing.. The whole point is not to blind test.. Just like not having an idea on earth about the Helix but makes a comment like this. <<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>> williewonka2,376 posts04-29-2021 6:08pm@dietch2 - well I’ve just spent the better part of the last 4 years ACTUALLY TRYING all of the things I have mentioned and in that time I have found that EVERY one of the things I mentioned does actually make for a vastly superior cable - regardless of length. You mean with your eyes. Sorry that you wasted 4 years. A book on electrical properties of materials and how to calculate L and C for round and parallel conductors would have saved you a lot of time. <<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>> Please move on NO ONE want to hear what you haven’t learned. I’ve followed this project and personally tried a few of the cables.. STUNNING.. You show your absolute ignorance when it comes to education, and APPLICATION. willies (Steve's) cable WORK. NO ONE wasted anything. As far a proof pay for your own... No one here need to validate your lack of experience.. Your just a Johnny come lately, with NOTHING but 1940s text book spew.. If you weren’t washed up, your sure showing you aught to be.. DENCE...MFer.. Your just a DUMMY.. Sit in the corner and learn something or take your spew and boogie.. Pretty simple for me.. Off the med on the meds off the med on the meds.. Mr/Mrs Yo Yo.. I really wish we worked together.. You’d last a 1/2 a day after telling people what they can or can’t understand or hear.. make that before first brake. IF they didn’t lock you in the shitter, load you on a truck and go over a couple state lines.. Teach you some friggin manners...QUICKLY.. Learn or leave.... You don’t know what your talking about.. WE ARE NOT wiring toaster OR ARK welders.. MY stereo gear NOT YOURS, you keep mixing that part up.. From watching your post, I question if you have a system I would KEEP Listening too after a few minutes.. Really makes me wonder how good a stereo can sound in a PADDED CELL? Oh and BTW it is time to feed the SMART chickens.. |
I still like mogami for RCA though they are on the expensive side I think they're constructed very well and sweetwater is great to do business with. https://www.sweetwater.com/store/detail/GoldRCA12--mogami-gold-rca-rca-12 |
| Post removed |
Those amplifiers had lots of feedback, but very poor gain bandwidth product. That was why they had bad distortion products, and why they had poor output impedance at high frequencies.They had excellent THD and IMD. Designers were sure they have to sound great. In 1969 I almost bought inexpensive 100W amplifier modules with incredibly low THD and IMD. NFB increases bandwidth and reduces output impedance. 40dB of negative feedback will reduce output impedance 100 times. Even when RF gets in, short of causing oscillation it may not even do anything.You don't even need nonlinear element, like diode, to demodulate. It is enough if amplifier's slew rate for positive and negative signal is different to demodulate, for instance, AM radio. It is called "rectification phenomena" and is very common to opamps. Yes, high impedance nodes are sensitive, but output of an amp, in spite of lower impedance (many ohms at high frequencies), is an input to the amplifier with 100x higher gain (for 40dB NFB) than amplifier's normal input. We want to reduce phase delay (improper summing of harmonics) at high frequencies caused by limited bandwidth. For that we increase bandwidth to more than 100kHz (my AHB2 has 200kHz@-3dB) getting very close to AM radio stations, not to mention switching frequencies of SMPS present everywhere (computers, TV) and even LED bulbs. |
