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Messages - slbender

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1
Tape Tech / Re: Tube pre-amp vs. Tube amp..........
« on: November 21, 2009, 11:29:40 PM »
Obviously SS has become better in the 70's, 80's, 90's, and 00's than it was in the 1960's.  Tube stuff has maybe remained the same.  Last time a RTR was made with tube preamp in general was the late 1960's or early 70's.

Custom (($$$)) stuff if you can find it and afford it is likely to be superb and might give a decent fight to middle of the road or high end SS.

The next thing one must ask is for playback... Which type of head is less distorted or sounds more like Live Music??  It has been my experience, that the worst lasting heads - Permalloy... sounds more like live music using a given pre-recorded RTR tape compared to playing that same tape on either a Ferrite or Single Crystal Glass covered Ferrite head machine, but then again some other type of head that I haven't heard, might be superior and I just don't know about it.... the Dokorder Molybdenum heads, or the Kenwood Super Long Lasting Heads if installed in a given machine might be both superior sounding and long lasting. Don't know.... but maybe I'd be interested to know!

Then again, one playback preamp might also sound way better than another brand, transistor vs. transistor... or JFET's, or MosFET's might best tubes or visa-versa.  I could also point out that different transistors sound different, your double diffused Planar, Epitaxial, Double Diffused, and Triple Diffused are only a few of the more than a dozen types of parts in use out there. Then again, some purists will complain about the sonic differences between Tube and SS Diode rectifiers, versus Hexfreds in the power supply complicating things to another level, regardless of whether the actual topology of the circuitry is: Transistors, JFET's, Mosfets, or Tubes.  Then again, there's directly heated vs. indirectly heated triodes to ponder on the tube end...  So it might not only be the playback head which contributes to this sounds more like live music phenomenon.

Too bad some rich guy, with too much money and too much time on his hands never installed six types of playback heads (Permalloy; Tandberg Ferrite; Sony F&F Ferrite; Akai GX Single Glass Crystal; Dokorder Molybdenum; and Kenwood S-L-L) on one machine, preferably a really good one, enabling one to switch between any of the six heads to see which sound better/worse than the others in a direct comparison.  At least we could have one opinion.

No, No, I'm not rich enough to get to do that, nor do I have the required machine shop to be able to custom install six various types of playback head mounts in one machine and align them all for zero phase shift and Azimuth.  Then again, the electrical characteristics of these various Playback heads might vary significantly from one brand to another so a given preamp playback circuit may not be optimum for more than one or two of the six; so much stuff is proprietary or at the designers whim, or personal best guess...

If I had to guess tho.... I'd bet on option #3, as the sonic best, but it might also be a bit noisier too.


-Steven L. Bender


What would be the sonical difference?

1. R2R with solid state pre-amp with tube amp

2. R2R with tube pre-amp with solid state amp

3. R2R with tube pre-amp with tube amp?

Has anyone of you compared the combination above?

2
Reel to Reel Tape Machines / Re: Technics RS 1800 on Ebay
« on: January 13, 2008, 01:26:48 AM »
I gotta admit that RS-1800 is a darn nice machine, never seen one except in pictures. Still, Akai made an almost the same set, two pieces, but speeds of 15/7.5/3.75 with a dual capstans belt driven by a servocontrolled motor. The PRO-1000. Maybe its 2nd best to that rare RS-1800, but again except for lacking the 30 ips its very similar, and people actually own them...

Was that seller the girl in that picture ???


Steven L. Bender


Actually that machine sold. He didn't quite get his asking price, but you still could have bought the Studer and made a down payment on one of our Repro amps for the price. Collectors are on another plane. You have to be able to convince yourself that rarity and status outweigh performance and practicality. I just can't do that.

3
Tape Tech / Re: How Long do Heads Last?
« on: January 12, 2008, 11:56:44 PM »
Hi RTR' Tape Users,

I think I remember answering a question like this once, so here it is again, the surface of a permalloy tape head is good if no uneven wear, until your fingernail gets "stuck in the groove the tape makes in the head surface. The amount of wear and tear it takes depends on several different factors

Factor #1 - Head surface material, ferrites can be several times header than permalloy and in general last longer, but bare ferrites as used in Sony and others tend to be very hard and also very prone chip off on a straight surface edge, so the thin gaps will develop chips making it wider and less uniform in areas, which worse then uniform wear causes anomalies in frequency response.

Factor #2 - Torque, the tape pressed against the head causes wear from friction, the combination of reverse-torque applied from the supply reel and the kg of pounds applied between the capstan and pinch roller results in an applied pressure against the heads. This physical system sees the head as the immovable force, and the tape as a fine sandpaper with iron oxide or other materials in contact with the head surface.

In the old, old days, the 1960's they used pressure pads, sometimes even into the 1970's, but most modern machines (1970's-80's) used the reverse torque, which applied more uniform pressure across the heads than did individual pressure pads on springs. Some sets applied a higher reverse torque (the  Pioneer RT-909 immediately comes to mind) which when aligned and set to factory standards has almost double the back-torque found on many other sets of that quality. The RT-909 therefore wore out heads about 50% quicker than an equivalent set would otherwise.

Factor #3 - The tape surface, mostly since it is a very fine emery cloth of sorts with paper or plastic backing instead of cloth, the tape if it looks dull and blotchy is fairly rough, but if it has a shiny mirror like surface, it is smoother and more refined. Clearly older tapes in the 1960's, like Scotch 111, Sony PR-150 are rough on the surface, while TDK GX, Scotch 207, or Maxell UD-XL have mirrored surfaces and all other things being equal would produce less wear. But some tapes like the 1980's EE tapes which have a splendid mirrored surface, but in actuality is a chrome tape, may induce more wear since it is a very hard surface.  Since true metal particles (as used in DAT and 8mm video tapes) was never used for reel to reel machines.

So, now to answer the question finally!!! The permalloy heads generally under typical conditions will last about 1500 hours (+/-) before the wear is serious enough to be measured on test equipment, and maybe 2000 hours before a user will hear or notice it.  Ferrite heads might last up to 5 times longer but due to head gap edge chipping effects, which probably require a microscope to see... they get worse with frequency response anomalies; however, if a ferrite chip gets knocked off and ends up stuck inside the head gap, I suspect it effectively shorts out the head and I could see that as a distinct failure mode...

Dokorders had a Molybdenum surface head which was claimed to last forever,  I have no idea... And some Diamond surface heads existed, mostly in some cassette decks I think.
 
Lastly, the single crystal glass covered ferrite heads supposedly the type all Beta and VHS video heads were made of, also found in later Akai GX RTR sets were quoted as lasting over 150,000 hours, but I kinda doubt those numbers, especially when using EE tape. So lets say they probably last about 5 times as long as bare ferrite heads, and never suffer the anomalies of edge chipping. 

So its from 1,500 hours typically for sets without pressure pads and less for the RT-909 and up to about 50,000 hours for some Akai sets depends on the actual products in use, YMMV.

Lastly, head relapping. Hmmm. The gap would have to be deep and uniform without widening in order for that to be effective without changing every electrical characteristic that makes the head, "the head".  Might be OK done once, not so sure about additional times.


-Steven L. Bender, Designer of Vintage Audio Equipment


Hi folks.

I'm curious - does anyone have an estimate of how long heads last in terms of hours of usage.  I realize that it differs with speed - twice as much tape travels past the heads for an hour of recording at 15 ips than at 7.5.  But, pick a speed.  So at 7.5 ips, how long would heads last in terms of # of hours of use - 1000?  2500? 500?  I realize it also varies with head design and material; ferrite heads supposedly last longer, but most of us are using pro or "prosumer" decks that don't use ferrite heads, at least not for R/P use.  I also realize that heads can be relapped once or twice before the gap opens and they are completely shot.  But even with the head material variable, does anyone have an estimate?  Techs who cared for these machines at radio stations and studios must have had an idea how long heads would last before replacement was necessary.  So how long?

The reason I ask is that as time goes on, parts for R2R recorders are going to get scarce.  I think you can still get parts for a Revox PR99, for example, but for how long?  If two years from now I need a new set of heads, will I still be able to get them?  If not, maybe I should go ahead and buy replacement heads for my Revox and Tascam while they are still available and just store them for that day when . . .

Thanks!

John C.

4
Tape Tech / Re: Sound Technology 1500A Questions !!!
« on: January 12, 2008, 10:57:34 PM »
Hi Ken,

I honestly don't recall where or when I got the 1500A and 1510A Manuals, I have several versions (different dates).  Never found any ST Manuals for download anywhere, so they are difficult to come by for sure.  I have been selling copies of mine for a while.

It is both time intensive and annoying to stand there at a huge Kinkos copy machine for a couple of hours to get a big manual done properly...  The Sound Technology 1500A, 1510A, 1700A manuals are among the biggest and thickest tech books I've ever seen, some are over an inch of pages thick!  If it was a PDF, it would be like several gigabytes in size.

I've been collecting rare electronics manuals for well over ten years, have around 250 -275 now.  I have both the ST-1500A and ST-1510A OP/SM listed on my web site, if you want it, not sure if it details the options, but 007 is the FFT analyzer board.

I'm still repairing my 2nd ST-1500A, its a brute to work on, but NOT impossible for someone who repairs Reel to Reel machines :-).

-Steven L. Bender

http://slbender.exactpages.com/manuals.html


  Stellavox,

 Today I checked the 1500 A I bought a while ago. It is a model 1510 A with options 007 and 011. I plugged it in and the display lights up.  I pushed the self test button and it referenced on the display.

    As you mentioned, their web site doesn't respond to an inquiry, so help from the mfg seems unavailable.

   With the info I posted regarding the options, can you tell me what it's capabilities are? I have no manual to follow. Is there a site where I can download the info or ?<>.

  By the way, I'm listening to the Arnold Overtures tape as I type, and on my 1958 Ampex  machine, I'd have a hard time finding vinyl that beats it.

  Charles, I thank you in advance for a reply.

  regards Ken

5
Tape Tech / Re: wild servo on technics 1500
« on: September 13, 2007, 07:26:53 AM »

Hi Rich,

A friend of mine had the same thing happen recently with his Technics 1100a direct drive turntable... He hasn't fixed it yet, but bought a similar armless 1100a TT and just switched the arm from the old one to the recently acquired one.  That was his solution.

Anyway, its been about 5 months since you posted, so I was wondering if you solved it ?

BTW - I've been supplying a DIY Servo Fix Kit for most AKAI RTR machines that use direct-drive servo-controlled capstan motors, since the late 1990's.   Turns out these RTR's often exhibit similar symptoms when they age after 25 to 30 years.


-Steven L. Bender



Went to use my Technics 1500 yesterday and it refused to lock on speed. It apprears to be 'whining', as if the servo has gone berserk. I never noticed any strange noises like this before. I've owned about 7 of these decks over the last 15 years and this is the first instance of a servo issue I've experienced. Any ideas about where to start on this?

Rich Brown
Acoustic Arts
Portland, Oregon

6
General Discussion / Re: Absolute Phase???!!!
« on: September 13, 2007, 06:53:36 AM »

Actually there are TWO topics here, first Absolute Phase of both channels and relative phase of ONE channel.

While Absolute Phase of both channels may be poorly understood, and some or many people can't even tell ( and I think I'm among those ) I'm still waiting to be wow'd hearing a really noticeable change by reversing the phase at both speakers.  Considering that there is a story that on many LP's and CD's the Absolute Phase is changed on odd and even cuts, or randomly, if that is true... I guess there is no set rule for Absolute Phase.

The other point, Stereo Channel Relative Phase - The aforementioned Phase Switch that David refers to as found on Early Preamps, and Integrated Amps... was used to reverse One Channel's Phase while not affecting the other Stereo Channel.  There exist many early Stereo recordings, Reel Tapes and LP's where either one channel is out of phase with the other, or some tracks of a multitrack recording, are out of phase with others.  Been documented, supposedly.

So there is Inverting, or Non-Inverting Absolute Phase, and there is Stereo Channel Relative Phase.

-Steven L. Bender


Is/was there any industry standard regarding phase? 

I am assuming here, but my guess would be that there was no standard for polarity in the industry either for manufacturers or recording companies, or else early pre-amps by Marantz, McIntosh, Harmon Kardon, and a host of others would never have installed a phase reverse switch.

I use the switch all the time to check recordings. I have found that some Columbia and Everest classical vinyl releases can benefit from reversing phase on playback. Also, multi-track recordings can have the singer in phase and the musicians reversed.

Some modern pre-amps will tell you if they are phase inverting. My Conrad Johnson PV-5 is non-inverting. And now, some of the new high end pre-amps have phase switching on them once again.

David

7
Prerecorded Tapes / Salvaging Smelly Moldy Pre-Recorded Tapes
« on: September 13, 2007, 06:12:38 AM »
Someone gave me several pre-rerecorded RTR tapes that have been stored badly, smelly and mold.  What to do?  I was told to toss them by she who must be obeyed, but want to try to salvage them.. Left outside in the sun for a couple of days, but that didn't help. Maybe I should put some clorox in a pyrex dish, suspend the tape it and cover with a large carton for a few hours, days, etc. ?  While the fumes might not affect either old acetate or mylar, what about the tape metal particles ?

Any other suggestions ?

tnx.

-Steven


8
Tape Tech / Sound Technology 1500A Questions !!!
« on: September 13, 2007, 05:56:52 AM »
Hey fellow Reel To Reel Tape Machine Users -

Got some questions on the vintage Sound Technology ST-1500A:

This is based upon an 8 slot motherboard, which typically has 6 slots occupied, plus a central power supply. 

As I understand it, some ST-1500A's have 7 slots occupied, the 7th board incorporates a 1/3rd Octave FFT Analysis function which is not documented in Operation Manual 7900-0021B.

And this is called Option 007.

If the above is correct, anyone have any data about Option 007 ?

Any Addendum information on Option 007 and its use ?

If the 1500A has an undocumented toggle switch on the rear panel, what is it for ?


Tnx.

-Steven


9
Prerecorded Tapes / Re: Tape Life
« on: March 16, 2007, 12:34:11 PM »

I find most tapes can be excellent, I have some old pre-recorded ones (acetate, you can see light through them sideways) which probably are as good as they were 40 years back. How long such tapes will last...Hmmm.  Anyone's guess, I'd think several hundreds plays if the tape transport treats the tape with even and constant tape tension - and add to that low tape tension.  They say acetate gets brittle, with age, but I've never seen that.  Sticky Shed Syndrome (SSS) I have seen; also instances where backcoated tapes have had the backcoating bleed to the edges and form clumps due to fast winding tension. Well sometimes Sh-t happens.

I also note that the Pioneer RT-909 as per factory spec, has tape tension set much higher (as I recall its over 30% to 40% higher) than most other high-end RTR's, so I would stay away from that set due to: faster head wear and high tension, if playing older acetate reels or very thin tapes like 1/2 mil. mylar are two of your uses for a machine.

The first thing I do with an older pre-recorded acetate reel, if it doesn't have leader tape (most don't), I put five to eight feet of paper or plastic leader on any reel I get.  Such old tapes should really never be played on a single motor consumer level machine. The tape tension and use of pressure pads can damage or ruin the tape by stretching and/or abrasing the oxide right off the backing. 

Also worn heads which have a groove cut in the surface can cause microscopic edge abrasions that ruin the edges of the tape and cause wow and flutter to be higher, and can lead to breaks and loss of oxide.  Lastly a clean tape path and clean heads are also necessary for the tape to remain intact and to retain proper channel balance. Gummy tape residue present on the guides will increase friction, which can lead to stretching, breakage, and cupping damage.

I think the best RTR players are those that feature dual-capstan transports, where both capstans are large in diameter, and rotate at slower speeds, and are located to the left and right of the tape path and all the heads.  On such transports, tape handling seems much better within the tape path, when compared to single capstan, 3 motor  sets, where a centrally located capstan, or offset (after the heads) capstan is present.  For me, only a few sets are like this and the list includes the servo-controlled motor, belt drive dual-capstan Akai's: The PRO-1000, GX-400D, GX-400D-PRO, GX-400D-ss, and GX-650D.  I own four of those five sets.  And also a couple of Sony's, the TC-558 or TC-756/758 in the 10.5 inch reel versions.

Next best would be centrally located single capstans, within an auto- reversing mirror image head lineup, as seen in the Akai GX-636, GX-635D, and Akai GX-266 MKII, GX-267D, GX-266D, Kenwood KW-8077; and Technics RS-1500, RS-1700, and the rarely seen RS-1800 series.

Slightly less best would be the offset capstan type, which can still treat tape well, if relay or logic is imposed with delays as seen in the Akai GX-630D, GX-625, GX-620, GX-255, and the Sansui SD-7000, and Tandberg 20A, 10XD, and 9000 series; Revox B-77, A-77, etc.


Steven L. Bender, Designer of Vintage Audio Equipment


Considering the forum you posted this in, I guess your talking about prerecorded tape. Most of them has lost just a touch of extreme high frequency. At least, that's the general thought. I've had incredible luck with the tapes I've bought. If it sounded good in the first place, it sounds good now. Some will knock your socks off! I think most of us will agree that the way that the tape was treated by it's former owner/owners has way more to do with how well they can be enjoyed now. If the tape itself is pictured in the ad ( I almost never even look at ones that don't have a picture of at least the box) look closely to see if the tape wrap is even and the end is held down. Look at the box condition. Even if you could care less personally, it shows how carefully the owner stored and handled the tape itself. I seriously doubt that most of the major sellers of r2r tapes really listen to all of them. So, having a good return policy is important. Finally, there was a shocking number of these tapes recorded. If you want an idea of this, check out Stellavox's post regarding his listings of 1/2 track r2r over on Yahoo's reel to reel group. He has invested a hugh amount of his own time to bring a fantastic service to us all.

10
Raw Tape / Re: Latest news on current production tape
« on: March 16, 2007, 11:29:20 AM »
I asked about 1/4 inch tape recently, and ATR replied that they have not made any for beta test, and may not make any for a while, so proibably not this year is my impression by reading between the lines.


Steven L. Bender, Designer of Vintage Audio Equipment


I know you're gonna kill me... "April 2007"... hehehe... gotta luv it!

besides, no mention of 1/4" tape anywhere which was supposed to have been their very first tape size...

*sigh*



11
As far as I can remember (I have the 100A Service Manual somewhere) the Advent 100 and 100A were both discrete transistors and FET's, except that one IC used as a microphone preamp in the earlier Model 100.  The Advent Model 100A's had Line 1 and Line 2 inputs (the leftmost pots) instead of a Microphone input and a Line input, and so I believe it lacked the UA-739 IC.  If not recording, all signals passed through discrete circuits only.

I also had a Teac AN-60 and AN-180.  Not quite sure about what the AN-60 had inside, but I did not like its sound, it soured me on Teac RTR's, which I also tended to think sounded shrill and "transistory".  I later found out the AN-180 was stuffed with nasty sounding UA-709 IC's in the signal path, which makes me glad I never used it, tho it did look nice~!

Anything as old as 1960's-1975 RTR's or Dolby units will be much less than optimum some 30, 35, or 40 years later.  Most RTR units I see these days, are not even coming close to meeting original factory specifications for frequency response, distortion, wow and flutter, and signal-to-noise ratio, without significant rebuilds, upgrades, or repairs.

I have some Dolby A-361's, and find it quite interesting that you say the A-301 was much better sounding.  Having looked inside, and based upon the massive use of cheapie tantalum caps inside the A-361's, I'm not surprised at all.  IC's and Tant caps, there are so many, some have to be in the signal path.  I'd love to go in and replace them all with lytics, or polypropylenes (as if there would be enough room...) and then do a comparison, but I don't have any extra A-361 units, or any A-301's to run such a comparison.


Steven L. Bender, Designer of Vintage Audio Equipment


I have used in the past the following: Advent 100 and 100a, Dolby Labs 334, Teac an-180 and Nakamichi NR-200B-c as well as Charlie's Dolby Labs A-301 beast. I really liked the A-301,as it was amazing for Dolby A tapes and pretty damn fine for the B tapes as well.The Dolby Labs A-360/361 pro units did not come close to the sound of the old A-301, which was the original Dolby Labs processor from 1966. Decca started using it in 1966 or 1967.  I now have a stock Advent 100, which is all discrete. I think the 100A went to ICs. I find the stock 100 to be on the warm side and the Teacs to be a bit brighter sounding.

It would be interesting to hear one of the Advents in stock versus modified forms.

Rich Brown
Acoustic Arts
Portland, Oregon

12
Raw Tape / Re: Recommendations for tape
« on: January 19, 2007, 06:20:29 PM »

Many USA tapes in the later 70's and 1980's are known to have had batches of SSS ( Sticky Shed Syndrome ). Debate continues as to whether this was due to environmental restrictions on Whale Oil, or other binder problems. Since its quite rare to find Japanese tapes that have the problem ( some Sony products being the exception ) since the Japanese kept Whaling despite resitrictions, I have to believe that since I've never seen a TDK or Maxell reel with that problem, I vote for the Whale Oil as the source of the problem.

Next Ampex / Quantegy type 456 is always a 1.5 mil backing in 1200' on 7" reel, or 2500' on a 10.5" reel, not 3600' ( 3600' would be a 1 mil backing or type 457 ).  I myself picked up a case of 12 Scotch 207 tape pancakes recently, about 20 years old, and have been putting it on empty reels too.  But, some metal reels have 3 screws, some have 4, even more, while tape pancakes come on standard three screw hubs.  So watch what reels you buy, the fancy TDK's ( LX and GX ) metal reeks as I recall have 4 screws, and will be incompatible with standard hubs.  Maxell metal reels, and most standard blank metal reels I think always have 3 screws.

Steven L. Bender, Designer of Vintage Audio Equipment



I'm having great results with Quantegy 456 and GP9...I've got a few Maxell's that I've picked up on e-bay for poor source material.  What I'm having trouble obtaining readily is 10 1/2" reels with 1/4" 3600' lengths of 456.  I've been getting pancakes of Quantegy 457 and "rolling my own", but need to find a relatively inexpensive source of 10 1/2" metal reels for the pancakes.  Anyone have a good source?

Heidana

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