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Thread: Bgw amp plus eq for free!

  1. #91
    Senior Member RMC's Avatar
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    CORRECTING THE AT PROTRACTOR

    Took some time to correct the spindle hole size on the AT LP5 cartridge protractor provided (post 85). The too large hole = loosely fitting protractor on TT, simply pissed me off for what is an otherwise ok cardboard tool. Initially thought I could get away fixing this thing easily using adhesive looseleaf reinforcements for binders (1rst pic). Well, the center hole on these is too small at 5-6 mm dia. for a 7 mm spindle, plus didn't really want to do another tedious scalpel job to enlarge those holes: enlarging some to decrease another...

    Last resort idea was to put the protractor on the TT then carefully and equally share the loose all around the spindle, followed by covering the loose spaces around the spindle with small pieces of masking tape, doing that on both sides of protractor. Not sexy looking, but it does the job. The result is a 7 mm hole and a now quite usable AT protractor (2nd pic). I double-checked the results I got with it VS two other protractors (Shure's & Stevenson's) and they match. Despite that, most of the time I still use two protractors when adjusting a cartridge to compare/confirm results. Then the cart should be performing at its best.

    PHONO CARTRIDGE OVERHANG ADJUSTER

    The white plastic "L" shape cartridge overhang adjuster, seen on posts # 88 in the box and # 87 with the 408 cart/shell mounted on it, is the one from the old Technics SLQ2 gone to recycling. Because it holds the shell/cart in place while working on it I still use that adjuster for INITIAL cart setup on shell. This reduces handling of the fragile cart/shell/tonearm directly on the TT, therefore minimizing risks of an accident.

    That small tool (3rd pic) remains relevant here, saves some time and potential needle damage. I noted some guys sell their overhang gauge on E-Bay, same for their Technics clear box SH-98 cart holder previously shown.That adjuster, with 52 mm effective length, is for a 15mm overhang. The last three TTs purchased (SLQ2, LP120 & LP5) required needle overhang adjustments of 15, 16 and 17 mm respectively. So I start with the 15 mm setting indicated on the tip (4th pic), then add just a bit more for 16 or 17 mm as the case may be. Checking the cart is parallel to the headshell is also simple using the overhang adjuster: comparing cart's front line vs shell's front line for example.

    Note at the bottom of the second pic here, AT indicates "Perfect Overhang Settings, OK"circled. What is shown there is NOT overhang setting but rather making the cart parallel to the headshell. Overhang is a distance of where the needle should be located for lower distortion, represented on the protractor by the two black dots inside the lines shown.

    My initial settings with the overhang adjuster are about 90-95% correct for 16/17 mm, therefore only minuscule fine tuning is left to do with the cart/shell in the tonearm & protractor sitting on the TT. Most of the work being already done using the overhang adjuster, prior to moving to the turntable for final adjustment, the latter is a breeze with much less handling to do directly on the TT. The last cart pre-adjusted needed less than a parallel line further adjustment based on the protractors. Did that, done deal!

    Richard


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  2. #92
    Senior Member RMC's Avatar
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    The original 1979 crest audio p-3500 power amp




    I 've wanted to post this for a long time and kept forgetting about it. Seems to me quite a few folks here don't know or remember about this amp which was one of the Pro game changers of the seventies, along with Phase Linear and BGW.

    Touring amp with audiophile sound, hence the "Fidelity Sound Power Amplifier" on the front panel. Crest Audio's founder worked with BGW for some time before designing his own more modern Pro amp than others at the time.

    Tested for Modern Recording Magazine (June 1979 P. 67) by Len Feldman and Norman Eisenberg. Their comments about the amp were quite positive. I can indicate where the report can be found.

    In 1999 Peavey purchased Crest Audio and things changed, like with all those audio acquisitions...

    Unfortunately Crown's response to others eating its lunch (market share) took way too long in my view with model PSA 2 (1990, according to spec sheet date), so many years later than other ones.

    Richard

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  3. #93
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    The peerless "evergreen" tweeter



    With regards to nearfield monitor types I mentioned recently on "Back in the 70's" thread, the following contains some info for the Peerless "evergreen" tweeter as pictured from an old catalogue I have.

    The 1978 purchased Polk Audio Monitor 5 with pretty low serial numbers, are among the first models they released, I still own them and they're somewhat larger than typical small nearfields. At that time a trade magazine test compared the Polk's sound to the Spendor BC-? sound but the latter was said to be short on highs (13-14 khz max). I may add that in a Stereophile review seen the Spendor's tweeter limit was assessed to be extending to about 12 khz. Both reviews indicated the Spendor was missing some very high frequencies, but for the rest concluded they sounded good.

    The Polk doesn't suffer from such lower top end having that widely used Peerless model # 810665 hi-fi "Evergreen" tweeter (frequency response graph below shows its relatively smooth). Its still there up to 18 khz then rolls off. Near the top end, it sounds a little incisive since the tweeter has a small but noticeable peak at about 15 khz which is easily cured with -1 to -2 db EQ, if need be. Depending on program material sometimes I don't mind the peak and other times I do. Also, note from the same graph the tweeter's impedance curve is pretty flat at 8 ohms on a wide range of usable frequencies.

    In addition to the 1" dome, it has a 6.5" bass/mid and 8" passive radiator (both rubber surrounds, they last!). Inputs are on standard binding posts and each driver is fused. A pic shows the banana plug type used to feed the speakers. Fusing drivers, as well as use of passive radiators, were more popular in the old days. I guess Polk didn't want its customers to be overly ambitious power wise on the speakers and blow drivers, hence fuses. They're not very high output speakers, will do 105 db with program material, but nice sounding ones.

    The HF driver was discontinued long ago. A number of known hi-fi speaker manufacturers used this tweeter in their boxes, saw a list of these on the Net. The made in Denmark manufacturing was quality but higher manufacturing costs too. Companies like Polk Audio and others made or found lower cost replacement tweeters for subsequent versions of monitor 5 and others. Binding posts and fusing were also changed later, possibly to reduce cost...

    Tymphany purchased Peerless and Vifa some time ago and moved production to Asia. Though NLA, Parts-Express still has it listed with specs. Mid West Speaker Repair has a copy made of this tweeter they sell and Simply Speakers also sells a replacement copy for $50. Cannot comment on the copies, since the drivers in my pair have never been replaced, the speakers are fully original and in good shape after 41 years.

    The 30-20 khz bandwidth mentioned in the Monitor 5 sheet appears overly optimistic at each end, in practice. Moreover, the "nearly perfect hemispherical dispersion" touted by Polk seems more marketing than real life in view of off-axis data indicated on the Peerless 810665 data sheet here. Also the clean usable response down to the 36 hz resonance of the passive radiator referred to leaves me wondering. I suppose the key is one's definition of "usable". In my view, with reasonable output, its probably 10 hz higher. Giving a real life stand alone bandwidth of about 45-18 khz. Biamping the Polks with the 2214H cabs further improves the low end and makes a nice complement...

    Richard

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  4. #94
    Administrator Mr. Widget's Avatar
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    Evergreen

    I know that tweeter well... I used them in several designs back in the late ‘70s and early ‘80s. It had a pleasant if slightly rolled off sound. If I recall correctly it was available in the $10-$15 a piece range while the Dynaudio D21AFs that I moved up to next were in the $40-$50 range back then.

    Both Peerless and Audax made really excellent drivers that were extremely reasonably priced.


    Widget

  5. #95
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    Hi Widget,

    Thanks for your input here. Always interesting to hear from someone who has much wider view than JBL alone. Though I had/still have high respect for JBL's engineering, which made me purchase three pairs, two I still own, it never prevented me to look at other manufacturers as well. There's some nice stuff from others too, as you have already shown. We're not in the same league, equipment and budget wise, but that's fine.

    In fact I have a lot more non-JBL stuff and this hasn't eroded my esteem for that brand. But at time of choices I also consider other non-performance related variables, such as currency exchange rate, manufacturing country, space available, budget, application, my needs, etc. Ultimate WATTS/SPL often sought on LH isn't really part of my list.

    Btw at 9,999 posts you're just one post away from enjoying a big cigar... Probably will keep reading the next 10K considering their usual practical no non sense approach... Regards,

    Richard

  6. #96
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    Some headshell/phono cartridge issues



    AT distributor stretches my patience. Ordered more than six weeks ago two more AT-HS10BK headshells, like the one with the V15 IV. Learned wednesday they're back order, no date in sight. Digging further I found they have only one left in stock, order for two couldn't be filled, so it was put aside, no call no notice... Still want that single one they have, then I'll even take an AT-HS1 (not as nice & silver) for second one to put the Shure/Radio Shack M75 cart on it. And if the lone HS10BK happens to be gone then its two HS1 (they have 10 in stock). That's it. 6+ weeks wait for what?? Want to sell? Make it happen, get proactive, pronto! Did check EBay and others for good used shells, asking prices are simply crazy, unreal. Better buying new then.

    Had to put the round spacers back on between the AT headshell and the V15 cart otherwise the tonearm wasn't parallel to the record surface (post # 89 3rd pic no spacers on; pic # 875 here they're back on, also showing the 45HE after-market stylus installed and next to it a worn-out Shure original, sniff). Undid prior install/re-mounted the cart with spacers, used the Technics overhang gauge another time, but adding a little more for 17 mm. Checking initial adjustment with protractor on TT indicates no further adjustment needed, surprising! Double-checked with another protractor: same result, no fine tuning to do. First time initial and final adjustments for that TT are the exact same, my lucky day, I'll take it. But...

    Trying the V15 IV revealed the original needle on it has reached the end of its life: the two channels aren't at the same level and the sound is distorted. Stopped it there. Haven't used the V15 for a while since the LP5 came with a cart I wanted to try, and the previous LP 120 also had a pre-mounted cart, plus its tonearm was not worthy of a better cart due to higher friction.

    As mentioned, the new stylus put on temporarily is that after-market 45HE shown. Seen with the small 50X microscope (post # 43) the needle on it looks good. However, upon use I noted the small dust brush (also a record warp damper) built into the stylus frame has too short hair to even work, making that device useless! They say a problem doesn't come alone, so that's another with the too short hair-cut. Mfrg country not indicated on the stylus packaging.

    Fortunately, it can be used with brush in up position (out of service). Still prefer having an ok needle with a poor optional brush than the other way around. Since a hand-held carbon fiber brush is used anyway to remove record dust, plus the Bellari phono preamp has a 20 hz rumble filter taking care of record warp sub-sonic frequencies if any. This way the stylus brush issue isn't a big deal in the meantime.

    Haven't risked yet putting the Shure Micro-Ridge VN45MR on the cart pending I get some new VN45HE replacement stylus, since the MR is now the sole and ultimate genuine stylus I have left for the V15 IV. At least not before I secure some other proper one(s). Looked at LP Gear, some Japan made prospects identified as replacements. Need to order some soon, then I may get rid of that no country/no brush 45HE...

    Richard

    P.S. While re-confirming yesterday the details about the headshells I want (A+B, if no A left then two of B, etc.), since there's still some money in this year's budget, I decided to go ahead and ordered the Behringer DEQ 2496, along with the companion mic ECM 8000, mostly for its RTA feature, and considering its about the only affordable hardware unit left on the market...

    P.P.S. The surrounds of the 6.5" bass/mid drivers shown on the Polk Monitor 5 (post # 93 2nd pic) look more grey, like foam ones, than black rubber stuff. They needed some careful dusting/cleaning with a damp rag, which I now had time to do, to bring them back to their original color. They are now black looking except for the lighting reflection on the pic below, surrounds still quite compliant too. Been using them more these days and will comment on that later (e.g. the Peerless tweeter small HF peak hasn't been an issue with a number of records even with no HF EQ correction).


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