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Messages - James Guillebeau

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1
General Discussion / Re: Good luck in your tape venture...
« on: April 13, 2007, 02:17:22 PM »
Why do you have to pattern your marketing to the RICH? Why can't you pattern your marketing to people who have R2R players and want a reasonably priced and affordable tape at 2 track, 7.5ips.  I think you would certainly sell more. Bass actually improves at 7.5ips. Don't even think about DOLBY or DBX! Our ear-brains learn to pump with the compressors. I for one would rather hear the dynamics with a little noise than loose the dynamics. Thanks, James

2
I'm toying with an all FET cascode front end which offers lower noise using n and p channel jfets from Toshiba.  Thanks James

3
The EF86/6267 is an "old" solution. But then again most everything surrounding tubes is "old". I can't help but think if you are sitting on such excellent RIAA preamps, the EIA and NAB curves aren't that far off. By the way what in your experience is the lowest grid leak champion among hi gm tubes? Thanks James Guillebeau

4
The front end is two 12ax7s with both feedback and passive EQ between stages. I think much better pre-amplification could be found. It was great when good 12ax7s in the late 50s could be had. I would favor a much high mu front end as a equivalent input noise consideration.

5
Suggestion Box / Re: Test tones on ALL tape releases??
« on: March 02, 2007, 11:48:14 AM »
No, head bump is due to the width of the pole piece of the head. Heads for show speeds i.e 3 3/4 are very narrow and as the speed increases the pole pieces have to be made progressively wider due to wavelength. That is if you want good realistic bass at the higher speeds like 15 and 30 ips. At 7.5 ips, you get great bass but as you speed up the tape then the head bump gets larger or so it was told to me. Ray

6
General Discussion / Re: "Audiophile" tape decks - Mark Levinson ML-5
« on: February 15, 2007, 11:24:09 AM »
Yes, I like many things on the MR-70. The viscous damped inertia reel idler. The use of the high gain phase splitter in the re-pro amps. I don't like that lengthy tape path across the heads. It's interesting that Ampex copied the Fairchild 126  synchroll tape path in the solid state ATR-100. The tape wraps around the capstan almost 180 degrees. But it's a completely DC servoed deck. You can mount both reels off center and the DC servo will completely correct the error. But those nuvistors are hair trigger oscillators. I used the AKG C-12A condenser mic for opera which used nuvistors and was constantly changing tubes after no time at all. Howling oscillation! You have to have a stash of those tubes to service it. And the price of nuvistors is steadily climbing like everything else that can't be had with ease and is made from unobtainium.  It's only for the rich crowd that doesn't have to worry about "if you have to ask then you can't afford."

7
Reel to Reel Tape Machines / Re: Tape head to preamp cable
« on: February 14, 2007, 10:28:48 AM »
I use Belden 8450 or Alpha 2460C, twisted pair, shielded, solid. I agree with PJ. Keep the cable short and get the preamp as close to the head as possible without getting near a power transformer or motor. James

8
General Discussion / Re: "Audiophile" tape decks - Mark Levinson ML-5
« on: February 06, 2007, 07:43:32 AM »
HI! I'd direct that question to Jay McKnight at MRL. He  makes reference test tapes and was with Ampex when the MR-70 was being engineered. He was responsible for many of the innovations in the MR-70, I believe. James

9
General Discussion / Re: "Audiophile" tape decks - Mark Levinson ML-5
« on: February 03, 2007, 02:39:28 PM »
The Ampex MR-70 while a truly fine machine used the similar tape path as the old 300 deck with the addition of a viscous damped supply reel inertia idler  (flywheel ran in a sump of oil)but it's supported path from idler to capstan across the head is long. I also don't like those all Nuvistor tubes in the electronics of the MR70. They'll oscillate if you look at them crooked or not holding your tongue right!. Much prefer the Studer arrangement and the Studer choice of tubes. Cheers! James

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General Discussion / Re: "Audiophile" tape decks
« on: February 03, 2007, 08:53:49 AM »
The Studer C & J 37 were made to  beyond "audiophile" standards. So was the Ampex MR-70.  Tim de Paravacini is making a living modifying the still existing C & J 37s and A80s A 880 and Ampex ATRs. The Studer C&J37 machines was used little in the USA but a number of them were used in Europe notably by the Beetles starting on REVOLVER. 1", 4 TRACK.The only other system I considered better were the Westrex 35mm 3 track full coat machines developed for mo pic production and used by Robert Fine for the Mercury Living Presence and Command recordings.

Record-play electronics advanced little from the first AEG magnetofon except for experiments by Marvin Camras and his cross field head and Keith Johnson and his focused gap beamed bias head. If you look at the average solid state mastering recorder's record-play circuitry used in the height of multi-track era, it is really awful! Terrible design with crudely patched in solutions. Op-amps used willy nilly. P channel FETs used as EQ switches in feedback loops! You can't clean it up without a completely new design. James Guillebeau

11
General Discussion / Re: Using old tube preamps with "Tape Head" inputs
« on: February 02, 2007, 11:38:29 AM »
Most vintage were in feedback loops around 12ax7A circa Ampex, Magnecord, Scully, Presto, Stancil Hoffman, RCA. You need at least a 400mh playback head for good output into a direct coupled tube stage, preferably 650 mh but not higher. This puts the head resonance within the audio pass band and results in lowest noise. The other way is the use an input transformer with a very low inductance head; 4.5mh. This also yields good SN ratio. With the advent of multi track heads the closeness of the head stack put a limitation on the amount of wire they could cram into a head coil.  It's difficult to make a 650 mh multi track head. The Studer C37 used mostly passive EQ with a minor feedback correction. If you had an NAB or IEC EQ test tape then you could make several of the resistors variable and then set the proper EQ. You also need to check the time constants and maybe replace a few caps.  Cheers! James

12
Reel to Reel Tape Machines / NYoil by the William F. Nye Co.
« on: January 28, 2007, 12:40:21 PM »
http://easyweb.abtnet.com/inetisscripts/abtinetis.exe/ecproductlist@public?tn=          1059_oil.tem

This is a highly refined oil I have been using for years. I build clocks also and use it. It's the best oil I have ever seen. As to maintenance, you should consult the owners manual. Sometimes "O" ring belts can be had from Motion Industries if they can't be had from the deck's manufacturers. They have offices in most major US cities.

Demagnitization should be done every time you clean the heads but always turn your deck off,  remove the tape from both bubs, turn the demagnitizer on far away from your deck and approach it heads slowly and then remove the demagnitizer equally slow before turning it off. Don't get the demagnatizer close to a VU meter.

13
Tape Tech / You need an AC voltmeter calibrated in dbv
« on: January 23, 2007, 07:51:19 PM »
To set up your machine you would need an audio RMS AC voltmeter  like a Genrad 1840A or an Eico 250. Hewlett Packard also made some but I'm not familiar with the model. Basically you need to calibrate the output level (playback level) with the VU meter on your machine.  Then adjust the input level where they match the output level when you switch from tape to source. Might be also nice to monitor the incoming AC voltage with a separate digital voltmeter.

14
Suggestion Box / Re: Test tones- HEAD BUMP
« on: January 22, 2007, 09:16:45 AM »
If you put test tones on the tape then 100 hz is too high to adjust or optimize head bump. And at 15ips you really have to optimize this unless the heads have very wide pole pieces. So IMHO there should be several bass frequencies and fewer mid band frequencies. Just my two cents! Good luck! Docfeelgood

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General Discussion / Good luck in your tape venture...
« on: January 16, 2007, 09:20:40 AM »
nt

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