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glenz66

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About glenz66

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  1. Thank you, Kimmo! I got a little derailed from this subject but I will soon be back on track to find the perfect solution for DC protection. And your information is always greatly appreciated! Best Regards Greg
  2. glenz66

    Thoughts on Amps for 3's

    I do not know why I had such a hard time on this quest for inline fusing. Lots of information that goes off on tangents gets confusing. For the AR-2ax and AR-6 speakers the following items are what I finally settled on from eBay. I had a horrible time looking for these: (BUSSMANN FNM-6/10 FUSETRON DUAL ELEMENT 6/10A AMP 250V-AC FUSE) And this one was extremely difficult to track down at a reasonable price: The 4515 open fuse block. I could not find the 4512 (for solder connection) Just leaving another trail for those who come after... Greg
  3. glenz66

    Would the inspector be pleased?

    Outstanding, Roger! This look like a fun project!
  4. glenz66

    Garage Sale Season

    Gentlemen, my warmest greetings! I hope that you are all having an excellent summer. At your convenience, would you please review the photos of what seems to be very early AR-2ax speaker. The back controls looks out of place to me. Has anyone seen or dealt such a thing? With Thanks, Greg Edit - Strike that request! It is an AR-2x... I keep seeing an "a" in these names for some reason...
  5. glenz66

    Another AR-4x restoration

    I know what was on my mind :-) Thanks for catching that, Roger. I also look forward to your AR-4x write-up.
  6. glenz66

    Another AR-4x restoration

    Awesome! That's the good stuff. If I ever stray upon a pair I will be set to conquer. Thanks again, Greg Edit -Will you fuse this pair?
  7. glenz66

    Another AR-4x restoration

    Kent - Congratulations on finding that great deal on the AR-4ax! And thank you for posting the renovation of the same. Do you have a before photo of the crossover so that we can follow the progress? I always get lost in translation. It is nice to see one of my tutors at work again! Best Regards, Greg
  8. While still chasing the ever elusive definitive speaker protection system against DC, I came across a wonderful thread that really spelled out the power amplifier and why things go boom. So I would like to share the following link with others who are as befuddled as I in the lost art of this subject... http://www.harbeth.co.uk/usergroup/showthread.php?1738-Can-speakers-be-protected-from-amplifier-damage-How-do-amps-work And below, as a sample of how illuminating this was, I copied post #2 from the link above: ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- A.S. Harbeth UK Join Date:Jan 2006Location:South of England, UKPosts:4,753 Default Thoughts about the workings of amplifiers .... Quote Originally Posted by broadsword View Post ...I have read a few times comments on these forums from members (and AS himself) that if an amplifier fails it can destroy the speakers. What is it exactly that happens that can cause a speaker to be destroyed?... First we have to consider what an amplifier actually is. It is nothing more than a high voltage reservoir - somewhere between 50 and 150 volts - which is sitting quietly minding its own business until some music appears at the input terminal and the volume control is advanced. You can think of the amplifier as a water reservoir high in the mountains, filled with water and contained by a dam. The dam has an opening, a gate, and under electrical control that gate can be opened a little, a lot or fully opened. Think of the fast-moving gate as being controlled by the music signal. When the music becomes loud, the gate rapidly opens and we (the listener, via the speakers), downstream, receive a gush of water. When the music falls quiet, the gate closes-off and we receive a mere trickle. Pause the music completely and there is no need for any water to flow - the gate is completely closed. Dam operation here. No, of course, there is far too much inertia in a heavy metal gate to be able to modulate the flow of water according to every note in the music, but the operational principal in the audio amp is exactly that. Rather than using moving parts, the 'gate' in the amplifier is literally the gate pin on the transistors and thermionic valves. See attached. What can go wrong then? The danger inherent in the storage of any potential energy source (water, high voltage, explosive, nuclear, heat etc.) is that the gate will fail and there will be a runaway leakage of the energy from where you want it (the reservoir) to where you don't (the loudspeakers). The implication of 'runaway' is that once the gate can no longer hold back the power, the power reserve is completely out of control and only when all the energy has dissipated (the reservoir has run dry) will the danger be over. But there will be consequent destruction to put right. What can you do to minimise the risk of the amplifier 'dumping' its entire power reserve on my speakers, and how long will they last if the amp's gate fails? From healthy to destroyed will take under ten seconds, too little time for you to realise what's happening and catapult yourself from your listening chair to pull-out the speaker plugs. Thankfully, electronics are very reliable and I've only seen this total destruction two or three times in the last 25 years or so. But there are some things you can consider which stack the odds for or against this happening to you. 1.The older the amp the more likely it is to fail. Components do not last forever, and capacitors are notorious for ageing. And the PSU reservoir is nothing but a bank of big capacitors! 2.Don't push your amp to the limits of its power ability. That will put strain on the components. So a 5W amp is just begging for trouble 3.Electronic components that run hot are inevitably less reliable than ones that don't. Solid state obviously is going to be more reliable than tube gear, all other things being equal 4.Budget equipment means that the specification of the electronic components has been made on cost grounds. That will inevitably impact on their durability 5.Cost into your amplifier ownership the need to have it properly serviced every 10-15 years or so, as recommended. Think of owning an amp as bringing the same responsibilities as replacing the timing belt in your car engine 6.Don't use an amplifier that is hugely more powerful than the speakers you are driving. You don't need the power reserve of the Hoover dam to fill one swimming pool: the more power the more destruction it can bring 7.Super-audiophile amplifiers that are capable of hundreds of watts and can hardly be lifted are just pure machismo. Their reservoirs have the explosive potential of a small bomb. When they fail the result is devastating, possibly combustion 8.For normal listening an amp in the 50-100W range is just fine and a good power match to most speakers 9.Turn off the amplifier when not in use at the wall switch. That lengthens the operational life of the components (which is stated in powered hours) 10.If you smell anything unusually hot in the amplifier or speakers, switch off immediately and seek professional advice Common sense about heat and durability. I've prepared an image of how an audio amplifier works. Any audio amplifier, from $50 to $50,000 - they all work this way. The circuitry could be a little less complex (but not much) and could be 100 times more complex (why?), but the result would be the same functionality: the reservoir high voltage is permitted in a controlled way to pass through to the loudspeaker. What you find under the lid is three basic blocks: the gate stuff, the reservoir capacitor (bank) and the mains transformer - that's the lot. How it works: a second or two after you turn on the mains, the transformer charges up the capacitors. If they are in good condition and not old and leaky they will hold that charge. Every 25th of a second or so, another little pulse of power will be drawn from the mains supply and presented to the capacitor reservoir. If they have discharged a little since the last mains pulse (because they have delivered some music to the loudspeakers and that power had to come from somewhere) they'll greedily take-in that top-up. If they are already fully charged, that's it; the reservoir is full. So the capacitors are topped-up twenty five times a second or so if they need it. The music signal is applied to the input of the circuit, the gate control arrangement. This particular mono circuit has four small signal transistors (Q1-4) and two really meaty output devices (Q5-6). Q1-6 are all three legged devices and I have marked the gate pin on each. Because the big old output devices are not very sensitive (but can really handle a lot of power, a trade-off) the small signal transistors incrementally boost the incoming audio from left to right through the circuit until it is strong enough to usefully drive the gate pins of the output bruisers, Q5, Q6. I've marked their gates in red. OK so far? So the music signal instantaneously works its way from left to right through the amplifier until it reaches the gates on Q5 and Q6. Exactly as with the water dam, those gates let trough the voltage stored in the reservoir capacitors to the speaker. If the music at any one instant becomes louder, the gates progressively 'turn-on' more and really let the juice flow from the PSU to the speaker .... if the music drops in level, Q5-6 progressively shut-off and the voltage flow from the reservoir diminishes to a trickle as commanded by the much smaller music signal. What fails? Any of these components could fail at any time, but experience tells us that anything that's running hot, either because it is working hard (such as Q5 and Q6 when playing rock music very loud) and/or poorly ventilated is susceptible to fail. And we know that the reservoir bank of capacitors, upon which the whole beast depends, is very vulnerable to ageing. So you could argue, with good justification, that the circuit design is not much important for the sonics but that the design of the seemingly humble PSU is in fact, much more important to the sound we hear. And it's the one part of the design which is vulnerable to age which must imply, I suppose, that an amplifier with a linear PUS as I've shown, could indeed measure, perform and sound different on day one or day one thousand of its life. That's really all you need to know about audio amplifiers. They are simple, dumb closed-systems with wholly predictable performance that can be software modelled to very fine degree. There really isn't any room for black arts in amplifier design if minimising long-term warranty claims is your commercial goal. Hope that helps. (3 hours) Attached Images Attached Images File Type: jpg Amp_principle-sc.jpg (142.8 KB, 66 views) Alan A. Shaw Designer, owner Harbeth Audio UK ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Best Regards, Greg
  9. glenz66

    AR3 unfinished pine ones. For now...

    The Horror! The Horror! Someone must help Turbon save that glorious tweeter! I must have something to hope for... You will be in my thoughts my brother, Greg
  10. Beautiful amp and inspiring work! Cheers! Greg
  11. This is becoming my favorite little corner as I try to get back to this page at least once or twice a week to reflect and chew on the wealth of the information, comments, and inspiration provided by you all. There is indeed a vast amount of knowledge that must be gained to enter this area of expertise and it gives me great courage to know that you fellows started your journey in a similar fashion. And cheers! on the careful study of safety regulations and basic information about electricity note! That 20% of lethality still is not favorable odds. Best Regards, Greg
  12. Awesome! This is just the type of information I was looking for. Vintage electronics can become somewhat addictive and I find much enjoyment soldering things with molecular structure. Especially if the end result leads to enjoying music. Best Regards, Greg
  13. glenz66

    AR-2ax Speaker "Tales of Woe"

    Encore photo with new grill cloth! :-) Thank you all for the comments and correct name for what I was calling speaker dope. I did the TT woofer check and the surrounds came back slowly so it looks like we have an acoustic seal. And with one final thanks across the board I will bow out of this thread and leave it drift through time in the archives. P.S. Kent? If you still have those AR buttons...
  14. Sorry to have turned this excellent page of yours to laments about my amplifier issues, Kimmo. After reading your comments and seeing your workmanship on that wonderful looking (and certainly sounding) Armstrong 621 I now aspire to learn the art of recapping and restoration of vintage equipment. Lots to study and prep-work ahead. For now I am still working on this Speaker Protection thing. David? Have you tried your hands at recapping vintage amps and such? In most cases it is the only route to take for lack of experienced techs. And If one is lucky enough to find one the wait game is the killing factor. Best Regards, Greg
  15. glenz66

    AR-2ax Speaker "Tales of Woe"

    I am extremely happy to say that my 2-1/2 year journey from "Songs of a Wayfarer" is near its end. Speaker #1 is ready for connection! And now to present the crossover cover! I was somewhat concerned about expansion & contraction loosening the screws though time so I bonded both sides of the wood spacers along with a shot down the drill hole with the Goop glue. I then, without pause, secured the cover to the crossover board with (4) 2-1/2" screws/washers and let the glue do its thing. Next I covered the structure with a layer of cellulose wadding to protect the rheostats from the new layers of insulation. The new stuffing was then packed in and around the speaker -- Roughly 2 bags in the upper mid /tweeter section and 1 bag in the lower woofer area. Lastly, a fresh layer of the cellulose wadding was used to contain the insulation in the cabinet and protect the backside of the woofer. And now we move along to the woofer's final placement. I figured it would be easier to lay the speaker dope in before the final wire soldering so that was next. I just winged the amount of speaker dope to use. I was trying for a 1/4" round bead but ended up with a layer about 3/8" in spots. And then the fun part! Reconnecting the woofer with my new found soldering skills. Call out to Roger's direction & ar_pro's excellent diagrams and advice. Check it. Final seating and lock down of the woofer. I was concerned about warping the outer rim of the woofer when it came to this leg of the journey; i.e. With the uneven layer of speaker dope and tightening the screws to much on one side vs another. The main concern was that the added stress on the outer rim would help to unloosen the cloth surround though time. To combat this concern, I tightened the screws as I pressed the woofer in the new speaker dope then backed off the presser and repeated the same until I felt it was evenly dispersed. I then waited 24 hours for a final turn of the screws. And so ends this road as I turn from it with a smile... Thank you! Greg
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