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acg

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acg last won the day on February 14

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About acg

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    I can't jump puddles
  • Birthday 31/07/1973

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    Toowoomba
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    Australia

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  1. acg

    The null tester

    That's me too if possible: sum it up and get it over with quickly. What does that say about the world? And about me?
  2. acg

    The null tester

    That may be true, but Max (?) Townshend managed it and was playing music from a cd player and nulling (or not) while playing on a speaker. Is it audible? Probably is if my experience with low inductance speaker cables is reliable.
  3. acg

    The null tester

    Unfortunately that is true. But the guy is still an engineer, from WA if I remember correctly.
  4. acg

    The null tester

    But I've known plenty of dogs called Bluey...you may be surprised, we humans are not always particularly inventive when naming cattle dogs. Also plenty of blokes called Bluey as well. So, back to the topic, being a practical kind of guy I always prefer to see things tested in the way that they are actually used i.e. tested in use if possible. For example, I might be looking for a new plough and find one that is very heavy and uses large girths of steel with plenty of wall thickness, over-specified bearings etc. and think that it will last me my lifetime if I were to buy it. Get it home and stick it behind the tractor and I'm busting welds and bending this heavy steel and although it met my original specifications when shopping for the plough in real life, when I used the thing, those spec's were not suitable for telling me if the damn thing would last my lifetime or not. That's an extreme example, but testing in real-world situations is where things really matter and this null test machine does not meet that primary criteria for me because the cable is being tested in isolation from the audio system. Not that I am in any way disputing EW's null test results or his honesty, but I just think that if he were to test the wires/cables in the audio system the result would be more meaningful. Right near the start of the video he says... Here is an audio engineer making a somewhat different claim that transmission lines effects are significant at audio frequencies, and he is doing a real time null test in an actual representative audio system with a cd player, amplifier and speakers... EW also claims... I am disputing this, because when these wires are used in the real world for their real purpose other things may become important such as shielding. Anyway, I'm not presenting the Townshend videos above as gospel, but I do find them quite interesting nonetheless.
  5. acg

    The null tester

    Well, I've seen this now (thanks for that Dave) and I can't null Steve out of my mind...and who calls a cat Steve? 😄
  6. acg

    Vinyl Enlightenment and Celebration

    The major problem is that feedback corrections are applied after the problem has occurred and so are always chasing their own tail. Vinyl playback is a marvel of engineering that it even works let alone sounds ok.
  7. acg

    Vinyl Enlightenment and Celebration

    Hi Grant, It is a 4 phase sine generator with outputs at 90 degrees. With the standard L75 motor only one phase is necessary, but if I use a 3 phase motor down the track then that is also covered with this speed controller. To set the exact speed of the motor you just vary the frequency of the sine wave using a potentiometer until the tacho reads as it should then lock it in. I will also have a tachometer setup using a hall sensor which will very accurately display the rpm each revolution but will not provide feedback with which to correct platter speed. I don't think the whole feedback thing can ever really work 100% because of the inconsistencies of the drive system of any turntable be that idler, belt or whatever. Best is to have a platter that does not change speed in the first place when confronted by varying stylus loads...but that is not an easy thing to do. Cheers, Anthony
  8. acg

    Magico Q-Sub anyone?

    You may be surprised how easy things are to build with steel or aluminium, I find it easier than with wood. Design it up in CAD, have it laser cut, tap some holes to screw it all together and then send it to a powdercoater or have it anodised or whatever finish you think is appropriate. It all depends on your background I suppose, and what you have experience with and are comfortable doing.
  9. acg

    Magico Q-Sub anyone?

    My subs weigh 400+kg each...are low excursion (like one to two millimetre)...and can hit 110dB+ at 20Hz with 9w of valve goodness. Diy lets you do a lot of things you cannot buy from a shop...although it does not necessarily mean you do it well.
  10. My speakers are 2.4m tall with a lot of drivers. Without fault, every (non-audiophile) person that walks into that room goes "man they must go loud!" or "who you trying to deafen!" or something else to do with loudness. If only they knew...
  11. My Amazon experiences have been mixed. Locally shipped product has been packed well and no issues from about 20 deliveries. Amazon US though... they can turn up rattling around in an oversized box with turned corners and records busted out of the shrinkwrap... then it is $30 to send it back before everything is refunded including the return freight. Bought about 200 records recently through Discogs and all of them were well packed, including the international shipments. Also only had one problem with a problematic grading of a record... from a local seller.
  12. acg

    Vinyl Enlightenment and Celebration

    The guy that is/was Phoenix Engineering has a few threads on diyaudio where you can purchase pcb's and build more or less those speed controllers that he used to sell. I've built up a couple of boards and will have finished speed controller for my Lenco over the Christmas break. I've also some Papst external rotor 3 phase motors that I will get running with those pcb's... they are very flexible.
  13. @Primare Knobdid you get a sample of the melamine foam or the polyester foam? Sounds like the melamine. Yeah, the thinner melamine foam will support the steel plate. Smaller panels have more absorption above about 300Hz because of the increased relative percentage of exposed area of the sides. However, if the edges are acoustically closed (i.e. solid, no holes) there is no loss of LF absorption which tells me that the percentage of exposed perimeter is not important for effectiveness at LF and it is the piston action and resonances of the steel plate that do the heavy lifting at LF. The resonances are affected by the size and shape of the steel sheet, with bigger panels more effective at LF and the length and height being significantly different, which is why the standard panel you can buy is 1.5m x 1m. How does the foam thickness affect LF? I am not sure to be honest, it is not in my notes here, but I do know that thinner panels (70mm) have been made and tested and are quite effective. The piston or resonance damping action of the foam hen it is attached to the steel plate may be more 'supple' when a thicker foam is used...I'm not sure but it sounds like something for testing. Larger plates (i.e. bigger than 1.5m x 1m) will be more effective at LF and less effective above 300Hz or so. EDIT: no picture in your previous post...perhaps attach it again.
  14. acg

    Vinyl Enlightenment and Celebration

    I'll have a new production version of that tonearm shortly @Full Range... then I'll have to figure out how to set it up. Nice setup, it looks great.
  15. MICHAEL JACKSON - OFF THE WALL - Legacy 2016 reissue in gatefold - $14 FLEETWOOD MAC - TANGO IN THE NIGHT - 2017 Stereo remaster 180gm - $16 Please...
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