Circuit before a recording head

mth5044 · 28th January 2009, 12:46 PM

Hello.

This may or may not be a noobish question, but I figure a forum full of incredibly astute people could help me out.

I've got an application that requires a signal to pass into a recording head and onto a recording medium, then to be picked up by a playback head(s).

I worked out a layout to take the signal from the playback head, bring it back up to a normal level and equalize it based on the LA3161 chip, but I am not sure what needs to happen before the recording head. I'm assuming that signal needs to be boosted to get a good signal down on the recording medium, but I don't know how the best way to go about this would be. I'm guessing it needs to be boosted, like a preamp maybe, but it can't get distorted.

I was thinking something based upon the BS170 transistor, but something else would work also. The simpler, the better. It doesn't have to be anything high quality, but I don't want to much signal degradation.

Thanks for any ideas you guys have. I appreciate it.

Take care,
Matthew

sreten · 28th January 2009, 01:30 PM

Hi,

If your talking tape your forgetting about / ignoring recording bias.

/sreten.

mth5044 · 28th January 2009, 10:28 PM

Unfortuantly, I haven't been able to find much information on what comes before the recording head, so I just figured that you had to boost the signal enough.

I guess I have some more research to do... *sigh*

Is there anything I can look at for an example? Or any known layouts/schematics I can look at? It isn't going to be on tape, but it's a similar material.

Thanks for the heads up!

Nigel Goodwin · 29th January 2009, 09:58 AM

As well as the requirement for bias, you need to provide a 'constant current' to the head - this is usually done very simply by feeding the head via a resistor.

I would suggest you check out old tape recorder circuits.

sreten · 29th January 2009, 12:34 PM

Hi,

Surely there are some cassette recorders / playback on a chip ?

AFAIK DC to a tape recording or playback head is a very bad idea,
you may thinking of the erase head which I recall being DC current.

/sreten.

Nigel Goodwin · 29th January 2009, 01:57 PM

Quote:

Originally posted by sreten
Hi,

Surely there are some cassette recorders / playback on a chip ?

AFAIK DC to a tape recording or playback head is a very bad idea,
you may thinking of the erase head which I recall being DC current.

No, it uses the same high frequency as the bias (the same oscillator), but at far higher power to erase.

Some really cheap and nasty cassettes use a permanent magnet to erase the tape, and a crude (and poor) DC bias.

mth5044 · 30th January 2009, 12:25 PM

Thanks everybody, I will look around for some tape player schematics.

I'm going to have a running project consisting of different recording mediums and I wanted to start with a floppy disc. Trying different coatings, testing wear and tear. Then maybe try running tape around a drum like the echorecs. Possibly harddrive recording.

I know, it's not practical, but I'm not a practical person

unsolved · 31st January 2009, 01:56 AM

Here is some schematics

http://www.audioschematics.com/tapelist1.html#Studer

When recording on tape you also have an equalization curve, to get better s/n and dynamics. worth thinking about.

recording on discs.. I have an old Rex Rotary, which is a dictaphone, "phonograph" which is recording on magnetic discs.... it´s from the 60's... Pretty cool stuff :-)

28th January 2009, 12:46 PM	#1
mth5044 diyAudio Member Join Date: Nov 2007	Circuit before a recording head Hello. This may or may not be a noobish question, but I figure a forum full of incredibly astute people could help me out. I've got an application that requires a signal to pass into a recording head and onto a recording medium, then to be picked up by a playback head(s). I worked out a layout to take the signal from the playback head, bring it back up to a normal level and equalize it based on the LA3161 chip, but I am not sure what needs to happen before the recording head. I'm assuming that signal needs to be boosted to get a good signal down on the recording medium, but I don't know how the best way to go about this would be. I'm guessing it needs to be boosted, like a preamp maybe, but it can't get distorted. I was thinking something based upon the BS170 transistor, but something else would work also. The simpler, the better. It doesn't have to be anything high quality, but I don't want to much signal degradation. Thanks for any ideas you guys have. I appreciate it. Take care, Matthew

29th January 2009, 09:58 AM	#4
Nigel Goodwin diyAudio Member Join Date: Jul 2005 Location: North Derbyshire	As well as the requirement for bias, you need to provide a 'constant current' to the head - this is usually done very simply by feeding the head via a resistor. I would suggest you check out old tape recorder circuits. __________________ Nigel Goodwin

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
recording amp	xautumnsashesx	Tubes / Valves	0	24th July 2007 03:53 AM
recording mic	jonastus	Parts	1	17th January 2007 04:31 PM
motor types head to head for a TT	p_ete2003	Analogue Source	20	11th January 2007 08:29 PM
Recording down to DC on CD.	Circlotron	Digital Source	1	31st August 2002 09:19 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th January 2009, 01:30 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, If your talking tape your forgetting about / ignoring recording bias. /sreten.

28th January 2009, 10:28 PM	#3
mth5044 diyAudio Member Join Date: Nov 2007	Unfortuantly, I haven't been able to find much information on what comes before the recording head, so I just figured that you had to boost the signal enough. I guess I have some more research to do... sigh Is there anything I can look at for an example? Or any known layouts/schematics I can look at? It isn't going to be on tape, but it's a similar material. Thanks for the heads up!

29th January 2009, 12:34 PM	#5
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Surely there are some cassette recorders / playback on a chip ? AFAIK DC to a tape recording or playback head is a very bad idea, you may thinking of the erase head which I recall being DC current. /sreten.

30th January 2009, 12:25 PM	#7
mth5044 diyAudio Member Join Date: Nov 2007	Thanks everybody, I will look around for some tape player schematics. I'm going to have a running project consisting of different recording mediums and I wanted to start with a floppy disc. Trying different coatings, testing wear and tear. Then maybe try running tape around a drum like the echorecs. Possibly harddrive recording. I know, it's not practical, but I'm not a practical person

31st January 2009, 01:56 AM	#8
unsolved diyAudio Member Join Date: Jan 2009	Here is some schematics http://www.audioschematics.com/tapelist1.html#Studer When recording on tape you also have an equalization curve, to get better s/n and dynamics. worth thinking about. recording on discs.. I have an old Rex Rotary, which is a dictaphone, "phonograph" which is recording on magnetic discs.... it´s from the 60's... Pretty cool stuff :-)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)