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Old 26th April 2011, 04:09 PM   #101
cbdb is offline cbdb  Canada
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That bass bump changes depending on the head output resistance, is there any way you can measure the DC resistance of the heads that the input sees?
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Old 26th April 2011, 04:14 PM   #102
cbdb is offline cbdb  Canada
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Quote:
The curve cleary shows that the slope starts about 6khz and is down about 3db at around 12khz.
The curves at the top of this page look like a higher freq. I would say 3db down at about 20khz. Which will be barely audible from old tape. I would concentrate on the 100hz to 10khz region, the HF roll off is easy.
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Old 26th April 2011, 05:58 PM   #103
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I could measure that, although I will have to remove the tape set so I can de-guass the heads afterwards. But if I am not mistaken, the impedance of the heads at that frequency would be more important?
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Old 26th April 2011, 08:57 PM   #104
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Quote:
Originally Posted by cbdb View Post
The curves at the top of this page look like a higher freq. I would say 3db down at about 20khz. Which will be barely audible from old tape. I would concentrate on the 100hz to 10khz region, the HF roll off is easy.


Yes,I was thinking that as well as it makes it diffcult to have to convert the voltage ratios in to db's.
So, That was a geusstemation from an eyeball's perspective from the shape of the curve. jer
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Old 26th April 2011, 09:04 PM   #105
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I pretty much think we have it nailed.
What do you think?
I do know that on most tape decks ( at least mine ) that the playback eq adjustments are 100hz and 10khz only this preamp lacks the feature of being adjusable and it is fixed.


jer
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Old 26th April 2011, 09:42 PM   #106
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Its no surprise to me that the EQ is only general here. The tape only moves at one speed.
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Old 26th April 2011, 10:53 PM   #107
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Or a variation of !
The greatest thing is the simplicity and how easy it is to work with them without having the latency and resolution with memory capacity problems that are incurred when working with digital systems.

I have everything to do all the digital stuff.

But you just can't beat the fact of setting the mixer and hit the record button and BOOM you have your take, rarther than fussing with a mouse just to do it again and loose that moment.
That is why I love tape machines.

jer
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Old 27th April 2011, 04:13 PM   #108
cbdb is offline cbdb  Canada
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I think its time you design something. That 100hz 10khz tape playback EQ is mostly to align different types of tape which is not a problem here. Idealy you need a test tape to test the EQ you design.
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Old 27th April 2011, 07:20 PM   #109
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Any IEC 7.5 ips tape from the early 1970s would do for that.
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Old 28th April 2011, 04:13 AM   #110
cbdb is offline cbdb  Canada
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Just popped the feedback network into an opamp circuit.

Just make sure the amp is high freq/high gain
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File Type: gif Mltr opamprespns.GIF (23.4 KB, 58 views)
File Type: gif Mltrn opamp.GIF (15.6 KB, 57 views)
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