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Messages - Dave Cawley

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Hi Paul

In the late 60's I prepared tape heads for samples.  I would do bias runs measuring output level and distortion and then frequency response.  Hard polishing on an Arkansas stone would often "sharpen" up the gap.  The customers were all down market such as Grundig and Fidelity and they were more interest in frequency response and rarely mentioned distortion. In fact automatic distortion meters had not been invented and they were manual with deep notches and many twiddly knobs!   The temptation to quote a bias figure that was clearly a tad too low, was simply irresistible.

The company was Marriott Marnetics in Penryn Cornwall England, and "old man Marriott" built a shining new factory with a penthouse suite overlooking the river.  He sold to IBM and then I moved away.  But that was 40 years ago, the factory still exists but is a shadow of its former self.

Regards

Dave

2
Hi Paul

What I meant was not over bias, like several dB's.  Clearly 0.2 is good, and shows you are on the peak in the right direction.  I'm always amused with cassette recorders that use bias to change EQ.

Regards

Dave

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From my dim and distant memory.  If you peak bias at 10Khz you will find you are under bias at 1Khz.   Under bias at 1Khz will give you distortion exactly where you don't want it.  Peak bias at 1Khz normally gives low distortion.

I would suggest peak bias (not over) at 1Khz and use the record EQ to get the 10Khz level correct.

Now this is based on my experience with tape more than a few years ago, and I'm up for anything more modern?

Regards

Dave

4
Reel to Reel Tape Machines / Re: Live recording on a RS-1500
« on: February 15, 2010, 02:19:34 PM »
OK, disappointed but all understood.  So, I'm checking and changing old capacitors right now.  Then I will pursue the bearings & tape path with a model maker friend before I take it into another friends professional studio.

Dave

5
Reel to Reel Tape Machines / Re: Live recording on a RS-1500
« on: February 15, 2010, 02:46:39 AM »
Hi Dan

I'm an expert on the Technics SP-10 turntable and have repaired several from the USA in the last two months.  A turntable less platter is quite manageable by Fed Ex, but a RS-1500 isn't.  I'm happy to share my knowledge on the phone to anyone here.  Dan, would you accept a telephone call from me in the UK to give me the benefit of your experience on the RS-1500 please?

Thanks

Dave


6
Reel to Reel Tape Machines / Re: Live recording on a RS-1500
« on: February 15, 2010, 02:45:43 AM »
Hi Steve

My test area is here www.soundhifi.com/test.html It might take me a week, but I'll go through the RS-1500 chain and measure as I go.  I did the same thing on a Quad 34recently.  The before and after was really quite different.

Thanks

Dave

7
Reel to Reel Tape Machines / Re: How do you measure tape tension
« on: February 15, 2010, 02:34:58 AM »
Hi Steve

I won!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150412401519

Thanks so much.

Regards

Dave


8
Reel to Reel Tape Machines / Re: Live recording on a RS-1500
« on: February 14, 2010, 04:54:28 PM »
We don't sell the parts for the tape path mod as a kit.

Hi Dan.  I'm in the UK and mechanically skilled?  What can you do to help me and others in Europe?

Thanks

Dave


9
General Discussion / Re: This Borders on the Ridiculous!!!
« on: February 14, 2010, 01:23:33 PM »
Two inches, zero feedback, registered under 2 months~~~~~~~~~~~~~~~

Dave

10
Reel to Reel Tape Machines / Re: Live recording on a RS-1500
« on: February 14, 2010, 01:07:47 PM »
Amazing, thank you!  http://www.aes.org/aeshc/docs/3mtape/aorprod2.html seems to identify them, but I'm struggling to see what the differences are?

Ah, see you edited it, give me a few hours.  This is just what I wanted.

Thanks

Dave

11
Reel to Reel Tape Machines / Live recording on a RS-1500
« on: February 14, 2010, 11:33:24 AM »
This might be off topic or even off limits, if so please tell me ?

I want to do some live recordings on one of my RS-1500's.  Before that I will refurbish one and make sure it meets the requirements of the service manuals and all signal path electrolytics are changed.  I used to lap heads as part of my job years ago, I think I still have the touch.  I would dearly like the tape path mods and new brakes, hopefully my wish will be granted?

But the question is.  The bias and equalisation switches, what sort of tapes were they originally designed for?   May not be relevant but I won't sleep unless I know.

Thanks

Dave


12
Reel to Reel Tape Machines / How do you measure tape tension
« on: February 12, 2010, 01:52:05 PM »
How do you measure tape tension?  Is there something you can buy, or is it so simple I am missing something?

Thanks

Dave

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Hi Charles

How does the A77 compare to the B77 ?  Isn't the A77 at least 30 years old?  I would like one to play with, here the A is cheap as chips but the B's are pricey.

Regards

Dave

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Reel to Reel Tape Machines / Re: New Deck or Upgrade
« on: October 29, 2009, 01:01:48 PM »
741's if used, will mask any changes, but you can buy op-amps that will plug straight in without resorting to really expensive stuff!

Regards

Dave

15
Tape Project Machines / Re: Technics flutter measurements with ST1510A
« on: October 22, 2009, 12:32:14 AM »
I'm not familiar with the ST1510A.  How close in can you see?  I use the HP 3561A FFT analyser, it can show flutter sidebands often as little as 30dB down.  I use it for measuring turntables and tone arms but have just become interested in reel to reel.  I measured an Akai GX625 and although the wow and flutter was within specification, the sidebands were disarmingly worrying.  Not being an expert I can't tell if this is a motor drive problem or a tape path/scrape problem?

Regards

Dave

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