Preamp for reel-to-reel

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aantunes

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Joined 2007
#1
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 😱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
 
#3
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
 
#4
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
 

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#6
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.
 

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#8
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.
 
#10
studeb said:
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.
Click to expand...

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

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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#18
Salas said:
You make me feel short and green with flipping ears like Yoda.😀

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.
Click to expand...

5mH, isn't to low for a PB head?
 
#20
aantunes said:
Just a small detail I'm not that hardcore in electronics....
Click to expand...
Why not learning from the Master? Mr. John Curl, a leading expert in the field of tape recorder electronics, is a member of this forum. Try to contact him.
Salas said:
Have read in a Manley manual 2mH to 10mH for most heads in solid state decks.
Click to expand...
On x-pro's site you'll find some values for cassette tape recorder heads.
 
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