Tag Archives: txsound

Zoom F8 backup bag rig

I’m pairing up the Zoom F8 recorder with my size-modified Lectrosonics Venue Field receiver. See txsound’s Venue mod for details on how I trimmed about 1″ of thickness off that box for potential bag use.

The actual bag is a Canon 1EG camera gadget bag, about $64. (Don’t hate on me, K-Tek)

I created a little “front box” for easy access to transmitters and other stuff.  Before it gets used for anything serious, I want to run it through its paces as a backup to my Fusion rig. There’s always a lot to learn about the peculiarities of a new recorder.\

F8 bag rig and Deva Fusion rig

 

txsound zoom f8 venue bag

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Seeburg 1000 “Window Unit” Background Music Player restoration

A recently edited presentation of our Seeburg 1000 BMC player. We call it the “Window Unit”

Seeburg 1000 players employ special 9″ records with 2.5″ center holes. The device plays both sides of each record, then lifts the stack to the top of the spindle for replay. Seeburg BMS (background music systems) were In widespread use in department stores, restaurants, and other retail and industrial locations from the early 60’s through the late 70’s. They have become very popular mid-century modern artifacts.   The thousands of  music selections were individually crafted by professional musicians and studios, and are utterly representative of  a unique and often forgotten part of American culture.   The 16 rpm records are widely available on ebay.

This is my 4th complete restoration of a Seeburg 1000 player.  Thanks for watching!

-Pete Verrando

A saga of Kentli Lithium-Ion 1.5 volt AA rechargeable cells.

Many folks are very excited to see the first rechargeable Li-Ion AA battery, made by Kentli. 

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Kentli AA Lithium-ion rechargeable cells and charger.

 

 Here’s a cut-away view of their exciting new AA cell:

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The guts of a Kentli Cell.

The Kentli AA Lithium-Ion cell was perceived as an exciting development, because all Lithium Ion cells are normally 3.7 volts. So even if the cell could fit into the AA form, the voltage was too high for 1.5 volt applications.  What Kentli did was cram a 3.7 volt Lipo cell into an AA enclosure, and also stick a 3.7volt-to-1.5volt regulator inside there as well.  The charging groove (see diagram) allowed the cell to be charged directly by the charger at 3.7 volts, bypassing the “motherboard” (regulator).

Why would we want a Li-on AA cell, anyway?  The perceived advantages:

1. Ni-mH cells, the current rechargeable of choice, provide only 1.2 volts per cell.  That missing 3/10ths of a volt can really add up when using multiple cells in series (battery)! The lower voltage also increases current draw, shortening the power-up time of the cell.

2. Lithium Ion cells maintain almost their rated voltage right up till they die  Other cells, the voltage slowly drops as the cell discharges.  Many digital devices will shut-off when the supply voltage falls to a certain level, leaving much potentially live-giving energy in the cell.

3. For their weight, Lithium-Ion cells currently provide the most deliverable power than any other type of cell. They charge fast, are very reliable, and last for many charge cycles. They are also tolerant to recharging at various states of discharge.

More Advantages:

4. Rechargeable batteries create less land-fill waste.

5. Rechargeable batteries create incomeas you can bill the client for these batteries like disposables.  So, they can routinely add about $20 or more to your daily rental income, without buying disposable batteries.  Over a year, that can add up (conservatively) to about US$3000. (that’s if you work only about 14 days a month as a professional location sound mixer)

So how well do Kentli Li-ion AA cells work?

As Chinese Industry is prone to do, Kentli did some slight-of-hand marketing with these products. They listed the capacity in milli-watt-hours, so they could print that big 2800 mWh on the side of the cell.  For people who don’t pay attention, this rating gives the mistaken impression that they are more powerful than 2700 mAh (milli-amp-hour) Ni-MH rechargeables. 2700 is a common value when looking for a high quality Ni-MH rechargeable.  At 1.5 volts, 2800 mWh translates to about 1867 mAh,  so the Kentli cell technically has less power. But Kentli claims their cell lasts as long as the Ni-MH, because the regulator allows the 1.5 volts to be maintained till the cell is completely exhausted.

The street price for these Kentli AA cells is about US$11 per cell, and the charger about US$20. More expensive than Ni-MH rechargeable. They are shipped directly from China through a few distributors, including sellers on ebay.

 

lectrosonics smv verrando txsound

A Lectronics SMV transmitter. 1/3rd of the package is for the cell.

We bought 12 AA cells and 2 chargers to give these units a workout in our Lectrosonics SMV transmitters.  The SMV uses only one AA cell.  A disposable Energizer Lithium AA will power it for 5 hours (the longest). The best NiMH rechargeable will power it for about 3.5 hours.

And the result? A fresh Kentli AA, right out of the box ,will power the SMV for 3.5 hours. Same as a high quality, 2700 mAh Ni-MH rechargeable.

But here’s the rub, in a few easy steps.

1. In my application, Kentli AA’s take their internal cell from a full charge to near-exhaustion in every cycle. Over the long term, I think Li-Po rechargeables prefer a lighter charge-discharge cycle. so with this workout, these Kentli cells won’t last for very many cycles. A Lectro SMQV would treat the cells more gently, distributing the current draw between two cells, and possibly resulting in better performance.

2. Kentli AA’s use a 3.7v Li-Po cell and convert it to 1.5 volts. There is inherent inefficiency in this conversion process.  The Lectro SMV then takes the 1.5 volts and inverts it up to 5 volts, and 3.3 volts, to serve the various internal functions. Every time you convert a voltage, you lose some efficiency and power, in the form of heat.  The Kentli is already stretching the capacity to the max of its tiny 3.7 volt, 760 mAh cell, every time it is charged and used. With the SMV, there are multiple conversions, and those power losses add up.

3. These days,  the “power down” mode of many devices is not a true power-down. Even after its turned-off, the SMV draws a tiny “quiescent current.” This is simply power to enable the SMV to power back up with a momentary button-push. The Kentli sees this quiescent current, and therefore keeps its motherboard alive, affecting a continuous drain on its cell. So leave a freshly charged Kentli in the SMV overnight, and it will be dead in the morning.

4. Maintaining AA rechargeables for location sound use is a pain in the ass. They get lost easily. I lost one in the snow on the very first shoot! They are difficult to keep separate between used and unused. They require chargers to be travelled and plugged-in. They require extra time to sort and charge and check at call and wrap.  They create a level of uncertainty in the production process. Will this be the shot when the battery dies for good?

5. And obviously, in the SMV, a rechargeable will run for only 3 hours, and a AA li-ion disposable will burn for 5 hours.  In most cases, 5 hours is enough time to get us to lunch, when the battery can be replaced.  The SMV is designed to accept a cell that swings from 1.9 volts to .9 volts, and before it dies, will suck every last ounce of power from the cell!

6. Don’t talk to me about the Lectro SMQV, the double AA version. I know they will run twice as long. I don’t care. I like the smally-small SMV for so many reasons. I use it as a drop-weight when running the lav cable down shirts and blouses and pant-legs. The SMQV is almost as large as a UM400A, Lectros classic 9-volt transmitter, of which I already have a shit-ton.  The SMV is great for use on children, with their tiny pockets and elastic waistbands. It also has the lowest profile in a pocket or bra-strap.

Oh, and the Kentli Chargers tend to die. 

kentli charger txsound

The Kentli Charger with its ring-groove contacts. They contact directly with the Li-Po battery and charge at 4.2 volts.

kentli, location sound mixer, txsound.com

The innards of the Kentli AA charger

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A 5 volt phone charger inserted into the 5 volt rails of the Kentli charger. Fixed!

Of the two Kentli chargers I originally ordered, one died a couple of months in. The dealer asked for photographic proof that the charger was dead. They sent a replacement from China, which never arrived, and then sent me another.  Eventually I received both chargers, so now I had four. Then the other 2 chargers immediately died.  Taking this opportunity to either throw away the dead chargers, or take them apart, what do you think I did? The charger consists of a very flimsy switching power supply converting your AC house current to 5 volts DC. The voltage is then applied to a smart charging circuit for the AA cells. The flimsy switch-mode supply was the obvious culprit, so it was replaced with an outboard 5 volt phone charger, of much more robust design. So now we have 4 chargers.

 

Then, the Kentli AA’s start to show signs of age.

This is about the time that the Kentli AA cells stopped delivering 3 hours of power to the SMV’s.  This is not the cell you want in a transmitter that goes out on a competition shoot, where you don’t have access to the talent once the action begins. I would guess I got about 100 charges on my Kentli’s before they began to show signs of expiration. The chargers show a full charge even on the cells that have stopped performing. In a less-demanding environment, (like an LED flashlight or an ipod dock) they may give better service.

And Alas! one Kentli drops to the floor and pops open like a Zippo Lighter! (Also the shrink wrap on the cell will begin to tear and peel with daily use. )

kentli AA txsound.com

Pops open like a Chap-Stick!

kentli txsound sound mixer verrando

The Kentli regulator board.

UPDATE : Curious about the quiescent current draw of the Kentli Cell, on its own, we hooked up a micro-amp meter between the regulator board and the Li-Po cell. The result:

kentli AA self discharge txsound

Kentli AA cells discharge on thier own, with a constant current draw of 29 microamps from the internal “motherboard.”

You guessed it. The Kentli motherboard is drawing 29 microamps from the cell at all times.  By comparison, Lectro transmitters, when powered down, draw about 5 microamps from the cell.  This is in conflict with the advertising claim made on the Kentli promotional material:

discharge claim kentli txsound.com

Advertising claim from Kentli’s promotional materials

 P1010251And whats this? A 3.7 volt, 2.66 wH li-po cell! That’s 2660mWh, or 718 mAh! Not 760 mAh, as the label claims!

So there’s no doubt the Kentli folks are really pushing the envelope with this initial attempt at a 1.5V Lithium-Ion rechargeable. A little more conservative design paramaters are required for location sound use. But for flashlights and home use, I’m sure theres no telling! And no telling of what’s to become of my little AA canisters for a location sound mixer on the road!

16" transcription record

Presto T-68 16″ Transcription Turntable Restoration

 About 3 years ago, I saved the pieces of this 16″ transcription player & cabinet from a dusty internment.

The 16" platter, stripped, cleaned and ready for re-felting

The 16″ platter, stripped, cleaned and ready for re-felting

presto turntable

cabinet as found

16" presto turntable

Project in pieces before restoration

Presto top plate with idlers removed.

Presto top plate with idlers removed.

 

 

 

busy day at txsound

busy day at txsound

 

 

(Click the thumbnails above for a larger “before” view). ,  This Presto T-68 Transcription Turntable with Pickering 190D Tonearms was used at an Air Force base in Fort Worth. Found inside the cabinet was a 16″ acetate record, with the lacquer falling off the aluminum substrate. The disc labels indicated the acetate had various Reveille bugle calls, marching and teletype sound effects. The military base had its own radio station, or perhaps they used these effects over the public address system for PT!

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The acetate found in the cabinet.

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Old Acetate disc labels from in bottom of turntable cabinet

 

 

 

 

 

 

 

 

 

Upon complete disassembly, work started on the motor & start capacitor, with a gentle variac power-up to check for shorts in the windings, or a bad capacitor.  It’s an an Ashland Hysteresis Synchronous motor of 1/100 horsepower. after a complete overhaul, the motor ran continuously for a couple of days to observe operating temperature, let the bearings settle in,  and discover any latent noise or vibration issues.  New motor mounts were installed as well.

Ashland motor presto turntable

Motor removed for teardown, old lubricant removal, reassemble and re-lubricate. Slow power up with variac.

Three rubber idler wheels transfer the motor’s energy to the platter at 78, 45 or 33 1/3rpm, depending on which plane of the spinning motor shaft is engaged (see photo below).

presto t-68 idler wheels turntable txsound

Transport with Terry’s new idler wheels installed.

The existing idler wheels (above) were hardened and crumbling. The brass hubs were re-surfaced by Terry’s Rubber Rollers. The motor and idlers get the platter up to speed in about 1/4 of a platter rotation. Pretty quick, which was important for the operators ability to tightly cue the audio tracks.  

The tonearms are type Pickering 190D, originally wired for mono.  BTW, Mr. Pickering holds the original patent on the moving magnetic phono cartridge!  These tonearms were heralded for extremely low vertical to lateral moments of intertia, and minimal vertical mass.  Because of the big swing of a long tonearm, the tracking error is less than 2.5 degrees.

pickering 190D tone arm

Pickering 190D tonearms, mono wiring & magnetic arm rest.

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The Pickering 190D (click/enlarge)

The tonearm’s extremely low head-mass  can deftly handle a warped record very nicely.  The rear tonearm is intended for a 78 rpm cartridge/stylus.  The front arm is for a microgroove cartridge.  A top- mounted rotary switch selects which arm is fed to the pre-amp.  Before restoration, the signal passed through a Pickering model 132E passive equalizer before being pre-amplified by a mono model 230H Pickering tube preamp.

 

 

pickering 230H preamp. txsound

Ad for the original preamp. (click/enlarge)

pickering presto

Pickering passive cartridge equalizer.

presto tonearm selector

78- LP tonearm selector

presto power switch

Power switch with a hand-made plastic mount-plate

 

 

 

 

 

 

 

 

 

Both  tonearms get re-wired for stereo, no small task with hair-thin oxygenated tonearm wire. The rotary switch was replaced to enable stereo switching between tonearms. The mono Pickering equalizer was removed(which will fetch about $100 on ebay) and the resulting empty hole with a bat-handle power switch for the motor, a more practical use of the space.   The turntable previously was powered-up when the speed selector was enabled. A  black switch mounting plate was created to match the other label plates on the plinth.

 

 

A new stereo tube preamplifer is now required inside the cabinet, so a Little Bear Stereo Valve Preamp was shipped in from Hong Kong.  (below)

 

Little Bear Presto Pickering

The popular Little Bear stereo tube pre-amp from Hong Kong.  Very nicely designed!

 

presto rca patchbay txsound

RCA patchbay on rear panel.

 

To allow the user to select the internal or an external preamp, An RCA patch bay  is added on the rear cabinet panel. Also shown is the ground lift switch, power connector and chassis ground terminal.

 

 

 

 

 

 

 

pickering presto turntable txsound

Assembly and wiring of tonearms. Individual Channel signal/ground wires eventually made into twisted pairs for hum suppression.

 

The cabinet was a challenge, especially the plinth. The 3/4″ plywood base surface was covered in a thick, ancient, funky, dull- green laminate. The surrounding metal was painted industrial grey with a good deal of chipping & corrosion. The metal surrounding the laminate was refinished in hammer-tone grey .  The funky-green clashed with the other colors, so the wood top was refinished in solid satin black.  The platter had plenty-enough green in it after the re-felting, which is done with felt, spray adhesive, and careful lathe-style trimming with a razor. The plinth’s vertical edges were stripped down to the bare metal and polished to a bright shine, almost chrome. The polishing process was observed in a motorcycle restoration shop, and has been sucessfully used here on lots of projects.  (Enlargable thumbnails below)

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2014-07-04_13-36-10_96 2014-07-04_13-36-41_12 2014-07-04_13-41-56_855 2014-07-03_12-46-10_159 2014-07-17_21-07-16_881

 

 

 

 

 

 

 

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Collection of 16″ transcription records are stored inside the cabinet. Those suckers are heavy.

 

The Presto- DuKane cabinet, preamp and associated wiring came together as pictured. The tonearms get fitted  with  Shure M91ED cartridges, the rear cartridge with a 78rpm stylus. The unit is extremely well grounded, including the motor shell, and cabinet ground is independent of signal ground. Wether using the internal or an external preamp, there are no hum issues. As a precaution, a ground lift switch was added to the rear panel.  Power lines are capacitor bypassed at the entry points and at the power switch.  (below pics are enlargeable)
P1030664h presto4h presto17H presto19h presto20h

 

 

 

 

 

 

 

The table adds a special allure to vinyl activities. A heretofore ignored  pile of 78 rpm records have provided some very interesting listening!  It’s the record industry in its infancy. Various recording techniques can be discerned, qualities, different equipment eras, groove depth variances, etc can all be heard.

 

 

 

 

presto turntable t-68 transcription verrando txsound

 

There’s a million cheap 78s, lps and 45s still floating around out there, in thrift stores, estate sales, and flea markets.  Many found 78s  have never been played, and those make for remarkable listening. Back in the day, the commonly used steel needles would destroy a 78 after 20 plays. Many outstanding shellac records are still out there, They are remarkable examples of recording skills and standards through the era.

 

presto transcription vinyl txsound pickering tonearm trans.com txsound

The 60’s produced some remarkably well mastered LP’s as well.  I particularly like the Command 35mm series, which are still in plentiful supply at the above mentioned sources. See you at the Goodwill!

MORE ABOUT TRANSCRIPTION TURNTABLES….

In the US, professional transcription turntables were primarily made by RCA, Gates, Fairchild, Presto, and McCurdy in Canada. They also required a separately purchased  “transcription” tonearm, about 3″ longer than a standard tonearm. The extra “swing room” these arms create also reduce stylus tracking error, especially on 7″-12″ records.

I’d been searching for a 16″ transcription turntable for many years. These tables are a unique and dissappearing part of broadcasting history.  Unlike a 12″ platter, they can  accommodate vintage 16″ transcription vinyl records, popular in the radio industry through the 50’s, 60’s, and 70’s. Amazingly, for their size, these records only contain about 15 minutes of program material per side!  That’s because the grooves are spaced far apart. The discs typically cannot fit on a standard 12″ turntable platter without hitting the tonearm base. The US Armed Forces and Veterans Administration used these records extensively to distribute their radio programs. The records also were popular for distributing library music, jingles and commercials.
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RCA 70 transcription turntable. Thousands of these used to reside US radio and TV stations.

Beardsley.press

A 16 inch record press

 

Gates transcription turntable txsound

Earliest version of the Gates CB-500 Transcription turntable.

The big turntables often came mounted on a cabinet, the size of a dishwasher. The earliest tables used this space for a complex, gear driven, flywheel-stabilized motor, These motors provided the necessary torque required for slip-cueing records and fast startup rotation.  Eventually, the torque came from smaller, hysteresis sync motors with idler/puck drives.  By the early 60’s these became the standard turntable design for radio/tv stations. In the early 80’s, Technics Corp. introduced powerful, direct drive, crystal controlled motors. They were adopted quickly by radio stations and used until CD’s replaced vinyl entirely…

rcaTTunderside
Huge flywheel motor affair that is under the platter of the early RCA transcription turntables.
Maybe there's still some hiding out there, somewhere?

Maybe there’s still some of these hiding out there, somewhere?

RCA BQ-2B 04

A more recent underside of a transcription turntable, the RCA BQ-2B. I do not recommend placing a tube amp in the cabinet!

 

 

 

 

If you’ve got room in your listening area for one of these behemoths, you’ll find them few and far between, and priced outrageously. And that’s before the freight shipping required to send to your place.  The most current and popular transcription unit is the Gates CB-500 ,  and the cabinet (if you can find it).

The Gates CB-500 and cabinet. The Holy Grail? This one's in Russia! The front panel controls are a sloppy, abortive add-on. 

The Gates CB-500 and cabinet. The Holy Grail? The front panel controls are a sloppy, abortive add-on.

 

 

 

gray-research-model-206-12-1 tx sound verrando

Grey Research Viscous Damped Tonearm with installation template.

 

 

 

 

 

 

 Personal Story Time: In my college days of Radio and Television (circa 1980), the school had a large, 3 camera TV Studio, with a huge cyclorama curtain surrounding the walls.  One day, while scrounging behind the curtain, I found two of the huge RCA transcription turntables, in their massive cabinets. They had the coveted Grey Research Damped Transcription Tonearms, so named, as the arm rode on a layer of oil to isolate it from the turntable’s vibrations. And also to minimize lateral friction. The RCA tables were in deplorable, but restorable condition. Piles of 16″ records cluttered the space around the machines. I had little interest in vintage gear in those days, and forgot about them.  20 years later, I  learned l that when the TV studio was renovated into a dance studio, the turntables had been unceremoniously trashed.  Truthfully, over 30 years later, I still have lucid dreams about finding vintage broadcast equipment in the bunkers and catwalks of my alma-mater’s fine arts building.  – by Pete VerrandoMeadows_School_of_the_Arts