Reel To Reel Modification - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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
Reply
 
Thread Tools Search this Thread
Old 7th December 2009, 12:14 PM   #1
diyAudio Member
 
Join Date: Dec 2009
Default Reel To Reel Modification

I have an AKAI 1710 RTR. 4 Channel (Two Tracks Stereo/One Track Monaural) tube driven, circa 1968.

Is there a way to modify the tape/rec head in such a manner that I could, for example, listen to one channel while simultaneously recording on the other channel? The RTR's Monaural record feature allows me to record on one channel while neither erasing or recording on the other, if there was only a way to monitor the unused channel, I could have a multi tracker. Of course, I realize that I would still only be able to record two tracks total, it would still be an interesting modification. IF it's possible.

I was thinking that if I could identify the wires soldered in to the tape head and solder leads to the correct wire(s), then run them to a separate preamp, or maybe run them to the preamp out jack on the back of the system, maybe put a switch somewhere in the line to enable/disable the function . . . something like that. Im not too familiar with the functionality of tape heads, other than that most heads handle record an playback duties. I suppose that if the machine can utilize one side of the head to record while disabling the other side completely, there must be a way I can turn it back on...
  Reply With Quote
Old 8th December 2009, 12:03 AM   #2
diyAudio Member
 
Steerpike's Avatar
 
Join Date: Jan 2006
Location: Johannesburg, South Africa
You can certainly do what you describe. Two areas of caution:
(1) the playback signal from the head is of very low amplitude (1 or 2 mV) so it wil be very susceptible to noise pickup. You need to ensure you use screened wiring, keep the wiring short, and don't route it past 'noisy' items like the power transformer.
(2) the 'off head' signal requires equalisation; simply routing it to a pre-amp will result in a terrible frequency response. Some older tube/valve amplifiers have a 'tape head' input specifically for this purpose.

Both the above wil be solved if you build a small "NAB" preamp, to install within the machine near the head area. This can be done with single chip.
Otherwise you'll have to mess around with the "record" and "mode" swiches to force the machine into play mode on one channel.
__________________
Steerpike's Toybox
  Reply With Quote
Old 8th December 2009, 07:09 AM   #3
diyAudio Member
 
Join Date: Dec 2009
Thanks for the info, greatly appreciated.

Ok, I spliced into the left channel of the tape head. I used a short length of old guitar cable, lined into a separate phono preamp and got a decent sound. Now my problem is, when you set the RTR to record on the right channel only, it disables the playback of the left channel. Does this mean I now have to find a means of supplying power to the tape head as well, or is there a way to modify the channel selector switch (Left/Stereo/Right) without activating the left channel eraser head? I dont have a service manual or any schematics, and like i said earlier, my knowledge on tape heads isn't all that great, but I'm pretty sure there's a way to do this.

Also, this NAB preamp. THe Only NAB preamps I know of are those expensive bottlehead preamps. Would you happen to have a schematic of what you're speaking of?
  Reply With Quote
Old 8th December 2009, 05:30 PM   #4
diyAudio Member
 
Join Date: Dec 2009
Never mind on that last one. I was having trouble finding a preamp due to improper googling. I found exactly what I need at Anykits for $7. Electronics Lab - Home even provided a schematic if I wanted to build it myself.

Now that I'm waiting on that to come in, I think I'll recap the motor as it is having some trouble playing on the high speed setting.
  Reply With Quote
Old 8th December 2009, 08:47 PM   #5
diyAudio Member
 
Steerpike's Avatar
 
Join Date: Jan 2006
Location: Johannesburg, South Africa
Quote:
Originally Posted by dr_zaius View Post
Now my problem is, when you set the RTR to record on the right channel only, it disables the playback of the left channel. Does this mean I now have to find a means of supplying power to the tape head as well, or is there a way to modify the channel selector switch (Left/Stereo/Right) without activating the left channel eraser head?
The tape head never "gets power" during playback.

You just need to tap into the head wires for the left channel head and route the head signal to your own pre-amp.

I'll have to actually LOOK at my 1710 (in the storeroom now) to refresh my memory on how it works exactly.

The heads plug into the amplifier via a circular multipole plug, so you dont actually have to make a permanent modificatio - just find connectors that match those already in use and patch in there.

Heres the circuitry to the 1720 - which is a transistor power amp version, but the layout is much the same. (the 1710 I think used transistors in the record amplifiers, but tubes for the power amps)
http://web.eject.co.za/s8nspawn/hifi/1720.jpg
I will only leave that pic on my homepage for a few days, so grab it to your own machine if you want it long term (I can't put it up here on DIYA, its too big)

Each channel has its own rec/play switch that are mechanically linked so they operate together. IF you can mechanically separate them, you can make it operate in play mode on one channel, and record mode on the other. That does involve physically modiftying the switching levers from the stop/play/rec knob to the amplifier box.
__________________
Steerpike's Toybox

Last edited by Steerpike; 8th December 2009 at 09:07 PM.
  Reply With Quote
Old 9th December 2009, 05:29 AM   #6
diyAudio Member
 
Join Date: Dec 2009
So, if I add an external tape head preamp, will I still have to fiddle with the Rec/Play switch?


The 1710 is kind of funky anyway. I cant check instument/mic levels until I have it in record mode, and even then the sound will only be heard through external speakers/headphones. I assumed that since there is a channel selector (L / L&R / R) selecting L will activate the Left REC head and disable the L & R Play head, and also switches the volume knob to a mic/input knob.

When I patched into the tape head, I ran my line to a phono preamp. I was able to listen to the playback, only in play mode. If I attempted to record on the right channel while listening to the left channel, I got nothing. I don't see how attatching an external tape head preamp will be any different, unless it somehow activates the head itself.

This is one of those times I want to shell out the $30 for a service manual.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Voice of Music Reel-Reel schematic needed Trout Tubes / Valves 3 23rd March 2009 01:58 AM
Revox, Studer, reel-to-reel and classical music Willi Studer Introductions 4 11th January 2008 08:03 AM
Akai reel to reel repair experts needed inside CBRworm Analogue Source 6 3rd November 2007 11:24 PM
Paper based reel to reel tape dates Zero Cool Everything Else 1 13th May 2007 12:54 AM
Full range in the Reel to Reel Sony TC230 alejo Full Range 0 17th April 2007 05:37 PM


New To Site? Need Help?

All times are GMT. The time now is 09:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2