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aantunes 23rd October 2012 08:16 PM

Preamp for reel-to-reel
 
Hi guys,

As been sometime I'm thinking to bypass the electronics of my reel-to-reel tape recorders and get the signal directly from the playing heads.

Indeed doc bottlehead as such preamp;;;but the price :eek:ui ui to high for my pocket.

So I beg any of you audio gurus have a simple schematic for such a preamp? with decent performance?

Thank you

john dozier 23rd October 2012 08:24 PM

You will need NAB equalization or its European equivalent, not RIAA. Regards

AMV8 23rd October 2012 09:26 PM

The only "tape" pre amp I have used is one designed by JLH. It worked fine as all his circuits do. It was a part of the tape player/recorder that he designed.
I do not think I kept a copy of the circuit but you could search in Google for it.
Don

Salas 23rd October 2012 10:04 PM

3 Attachment(s)
I had been asked once to embed NAB and IEC by a member but heard no news. Here are the circuits since it took me enough time to investigate. Maybe someone with open reel finds them interesting to test their fitness or tweak a bit from there.

edit: revised NAB circuit

kevinkr 23rd October 2012 11:35 PM

The NAB Bottlehead tube pre is pretty good sounding and I believe the schematics are available on that site.

Salas 24th October 2012 12:22 AM

2 Attachment(s)
Here is what the above circuits do by the way. First pic is the input IEC response that is corrected to flat by first circuit. Second pic is the NAB correcting EQ the second circuit imposes on the play head's signal. Open reel aficionados may examine. Both are for 15 inches per second. The input trimmers are for loading both low and high impedance heads better since load can affect their HF I had read.

franzm 24th October 2012 06:27 AM

@aantunes: What brand/type of tape recorder?

studeb 24th October 2012 06:16 PM

Master Salas,

What imp/resistance head did you model? Does it matter?
And if I wanted trimmers for gain and freq response, where would they go?

And for aantunes, the bottlehead seduction phono amp can be modded to NAB/IEC, it is not as expensive as the eros kit.

paulb 24th October 2012 06:25 PM

http://www.ti.com/lit/ds/symlink/lm4562.pdf
page 25

Salas 24th October 2012 07:19 PM

1 Attachment(s)
Quote:

Originally Posted by studeb (Post 3213960)
Master Salas,

What imp/resistance head did you model? Does it matter?
And if I wanted trimmers for gain and freq response, where would they go?

And for aantunes, the bottlehead seduction phono amp can be modded to NAB/IEC, it is not as expensive as the eros kit.

You make me feel short and green with flipping ears like Yoda.:D

I used 5mH lower impedance later heads assumption, and about 350R source resistance. The input does not care but the heads may care, hence the trimming load addition. Good multi-turn trimmers in the passive EQ section (R4 HF) and R10 for gain. Very sensitive in the IEC for R4, see how it goes for 85R example.

P.S. Its only a theoretical exercise remember, it should take some work from here when with the real reel beast at hand. Don't know for peak overload for instance.


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