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DavidR

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  1. For sale is my Bob Latino VTA ST-120 vacuum tube amp. It doesn't get a lot of use and I am trying to down size in preparation for moving. It comes with the following tubes. All tubes have been tested for emissions, shorts and grid leakage on my Sencore TC142. (4) Sovtek 6550 and measure 110 on emissions (2) Tung-Sol 6189 and measure 93/94 and 93/93 (1) NOS RCA 12BH7A and measures 100/101 (1) Sino 5AR4 Rectifier I would prefer to not have to ship. So for local pick-up (for now). I live in MetroWest MA area and will deliver within a certain distance. Asking $1200
  2. Try Lacquer Thinner; it contains many solvents and one in the mix might do it.
  3. I have no problems getting good bass........very good bass. I found that both the Pre amp Amp play a big role. A good current pushing amp does the job. I did find bass improvement, especially in the LMR, with the recap. I suppose you could try it. As I said above about another pair of speakers. It just sounded right with the tweeter out of phase. It maybe as simple as that. Perhaps Tom Tyson has some knowledge on this.
  4. Just compare the AR9 schematic to the 90 and pay attention to the wire color and where they go. For instance the 9 has the yellow wire (+) go to the series caps 4uF + 6uF The 90 has the blue wire (-) go to the series caps. As for why AR might have done this I remember modifying a mini pair of Yamaha speakers. The only component that remained was the woofers. I replaced the mids and tweeters and made a whole new crossover. I ended up wiring the tweeter out of phase for no other reason than it just sounded better; sounded right.
  5. The tweeter, UMR and LMR are wired out or phase from the woofers on the 90. AR still used the wire colors so that you will still use (for instance) the yellow wire to the '+' side of the tweeter BUT it actually goes to the negative side and not the capacitor. The blue wire goes to the series cap.
  6. The outer surround edge to the woofer frame/basket not the bead on the outer edge of the cone. The bead AR would put on some of the woofer cone outer edge was, I believe, rubber cement which is quite different than silicone rubber. Silicone is the issue.
  7. The glue on the woofer surrounds appears (to me) like it might be silicone rubber. Let us know if it is. It will have to be fully removed before a 'proper' glue can be used successfully.
  8. ROUND magnet vs SQUARE magnet. This has come up with other models like the AR9 and 90. I've read threads here on this site that AR sourced from different suppliers. NO differences otherwise.
  9. As I see it, AR was late to the 'College Craze' audio scene and probably quickly created something to offer in an affordable speaker. AR-8, 1973-1974, 10" Woofer, 1.25" Cone tweeter, 48-20k ± 2.5db, 1800hz, 15- w, 8 ohms, 13.5x24x11.5, 32.0 lbs, $129.00 AR-12, 1977-1979, 10" Woofer, 2.25" Cone Mid, .75" Dome Tweeter, 44-30K ± 3db, 86 db, 700/4000hz, 25-100 w, 8 ohms, 14x25x11, 37.5 lbs, $225.00
  10. Next time he runs a for sale ad message him and ask. He must find all the 9s in his area.
  11. On a side note I think you should contact Joe at MidWest and see if they can get some w/o the horn.
  12. Hi Roy, I really have no idea. Like the original there is a thin plate on top of the flange that surrounds the plastic horn. The MidWest driver appears to be ABS where the AR seems to be metal. The horn material is quite hard. I am guessing that the construction is the same but maybe different materials.
  13. The MidWest copy of the 044 mid is glossy black with the clear dome. They are exact copies right down to the holes and the magnet structure. Why they didn't use a black coating on the dome is beyond me. The tweeters resemble the older style found in speakers like the AR11 and 10Pi. The back is enclosed covering the magnet structure. Both are drop in ready.
  14. I ordered one of these new midrange copies of the 044 mid/UMR and a pair of their tweeters that I'm using in my AR10Pi. The dome is in fact a silk fabric dome with a clear coating. The coating is slightly tacky. I was unable to tell if there is any damping material below the dome. The mid/UMR has a free air resonance of 400Hz. Today I got around to installing one tweeter and the UMR into my AR90s. The tweeter sounded identical in tone to the original 200029 tweeter but has slightly more output/volume associated with it. I found it easier to hear cymbals and other high Hz music signals. The UMR also sounded like the original but I found it to be a bit clearer/cleaner than the 200028 UMRs which I find can sound honky at times. Could this be from drying ferrofluid or just a difference in the drives, I don't know. What I think is that these drivers, which are drop-in replacements, are quite suitable to replace the originals. Its only a matter of time before all the originals are dead or muted from dried ferrofluid. With nobody able to rebuild the originals to near factory specs I see no other solution at this point.
  15. DavidR

    Sad news

    OMG! 😢 Too young. His contributions will be missed. Thank you for posting.
  16. Short BYPASS white paper.docx George E. Short III BYPASSING North Creek Music The Art of Bypassing Bypassing capacitors is a little like blending watercolors. With watercolors, the dominant pigment can be brightened, softened, darkened or lightened with small additions of other hues, and it takes a delicate touch to make the perfect shade. With capacitors, the signature of the base cap can be brightened, softened, darkened or lightened with the addition of the appropriate choice of bypass capacitor. The "perfect" tonal balance can only be determined by ear. And, like watercolors, the whole is often greater than the sum of its parts. The bypass capacitors we have developed have very specific subjective characteristics that can be applied to improve the performance of most loudspeaker crossover capacitors significantly: Cascade Bypassing Classically, bypassing a capacitor means paralleling a very small cap (0.5% to 1% of the base cap) to improve the effective high frequency performance of the base cap. While this works to a point, the problem with simple bypassing it that it tends to sound a little discontinuous, with the large cap dominating the signature at the low end while the bypass cap dominates the upper extreme. Cascade Bypassing (or simply "Cascading") is a bypassing method that yields the best and most homogeneous sounding combination of capacitance. Cascading is essentially paralleling smaller and smaller capacitors of increasing voltage to reach the target value. We usually suggest a cascade of 5% to 25% steps, with each smaller cap having a higher voltage rating. Examples of Cascade Bypassing are: 100.0µF = 100µF 100V + 4.7µF 225V +1.0µF 625V (=106µF, within 10% of 100µF) 6.8µF = 4.7µF 200V + 1.0µF 600V + 0.10µF 800V 4.0µF = 4.0µF 200V + 1.00µF 600V + 0.10µF 800V Cascading sounds better than simple bypassing because it yields an overall homogeneity to the sound of the equivalent capacitor. Bypassing with North Creek Capacitors Harmony Capacitors were designed specifically to bypass other metallized capacitors. Their signature is lightweight with a wealth of detail, and the top end has a nice sparkle without being bright or forward. They are also much quieter than most capacitors, particularly those that wound with very high tension. We best describe the Harmony caps as "cleaning up the sound" of other capacitors. Crescendo Bypass Capacitors were designed to correct the harmonic imbalance we found in most of the film capacitors coming out of California; that is, a weak lower midrange, forward upper midrange and over-emphasized treble.. Many listeners equate this tonal imbalance with a "wealth of detail", although we find it unnatural and unsatisfying for long term listening. The Crescendo bypass cap, with the thick 600 Volt and 800 Volt film and heavy conductor, is very rich through the midrange and much softer in the top end than most of the premium capacitors coming from California. In designs where both the tweeter and the electronics tend to be bright, but a "wealth of detail" is a primary design goal, the combination of a "West Coast" capacitor with a Crescendo bypass capacitor usually yields the best of both worlds. Unusual Qualities of the Crescendo Capacitor We have noticed some of the strangest things can occur when one bypasses with a 1.0µF crescendo capacitor. Perhaps the most unusual is the way this cap can "quiet down" a woofer when used in the capacitor stack going from the output of the low pass input coil, to ground. This is true of both Zobel circuits and shunt legs of second or higher order low pass filters. Frankly, we can not pin down why this effect is so dramatic in a parallel application, but it is. Try it - you'll like it. It may even blow you away. We have heard of several customers using five 1.0µF 600V Crescendo caps bypassed with a single 0.10µF 800V crescendo to drive a Focal T120 tweeter. This is a driver with excellent information retrieval but when used with the wrong caps tends to get a little brittle. The stack of Crescendo caps is said to yield the ultimate combination. For those using the Scan Speak Revelator tweeter, one should cascade Crescendo caps throughout. The Revelator has a broad peak in the 8kHz to 20 kHz region that will be emphasized considerably by any of the brighter film and foil caps available. Make no mistake - this may be the best tweeter in history, but it needs proper care and feeding to sound its best. See our Rhythm-Revelator project for more information. Danny Richie of GR Research, concerning bypass capacitors: Danny felt that it wasn't just about the bypass cap being superior to the base cap. It was also the fact that you were adding a small value capacitor to a larger capacitor. Danny felt that the resulting paralleled pair of capacitors offered a better discharge rate than the single larger capacitor. Danny seemed to feel the faster discharge rate was audible, and improved the quality of the sound. He stated that it helped with the perceived 'speed' of the transient response of the circuit.
  17. There seems to be an issue with the editor on this site. Trouble uploading.
  18. You can use ordinary window foam gasket (comes in rolls) for the drivers. Its a little softer than the Parts Express foam and makes a better seal IMO. As for bypassing there is a guy named George E. Short III who was an audio engineer and worked for AR for a period of time. He went on to form North Creek Audio and made speakers and some great audio capacitors. He made a living on his bypassing and cascading techniques. I will try to attach a 'white paper' word document. I used some small (0.01uF) bypass caps on my 10Pi series caps (10 and 40) as I had used NPE and wanted a bit more detail than they are known to provide. There several current day audio engineers who incorporate bypassing in some of there designs. One is Paul McGown of PS Audio and Dan Richie of GR Research. If you add them and feel it is giving you a negative effect then its very simple to snip the leads. The switches might be more than you want to deal with. Each of the three switches has a hex nut threaded to the main shaft of the switch body. They all need to be removed and the pcb is pulled out from the inside.
  19. The AR9 and 90 used p/n 200028 UMR and the 91 uses p/n 200032 mid. The difference is the AR9/90 UMR has half the resonance of the 200032 mid. The AR9/90 UMR had ferrofluid on both sides of the vc. The 200032 can be used in place of the 200028 but not the other way around. The 200028 UMR just won't reach down to 700Hz IIRC that is required for the AR91. The 200044 came out when the 58 was introduced. It was mostly a cosmetic change. It was also used as an AR replacement driver from AR for the 200028 and 200032.
  20. I really think the iso-OH will separate the glue from the plastic. Can't hurt to apply some and carefully pry a thin blade between the 2. Better yet, just put a thin blade between the old cap and the glue after dribbling some iso-OH on it.. I bet it will pop off. I use one of the very small flat screwdrivers. Based on the stuffing material I can see it looks like version 1 that used fiberglass and not polyfill.
  21. You shouldn't have to add any wire. I left the old cap leads as long as possible as it is very tight in there when working. Makes it easier to tie on the new caps. I did add some wire from the transformer to the 2500uF cap but I used AR wire from a AR94 crossover board. Kent has a good point about hot melt effects on a cap. I used Goop and not a lot. Very similar to E6000. Not sure what's available down under.
  22. There is some info in this thread and an excel sheet with the cap values > https://community.classicspeakerpages.net/topic/9950-picked-up-some-more-ar-speakers/
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