Tube tape head electronics for Otari MX55

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

BradM

Well-known member
Joined
Apr 14, 2006
Messages
113
Location
Palo Alto, CA
I have an Otari MX55 1/4" machine in my studio that has been very reliable.  The transport is great and handles the tape beautifully.  The autolocator is very precise too.  I like everything about the machine, expect I really feel that the sound could be improved.

Last fall I rebuilt a Dynaco PAS3X preamp and turned the phono preamp into a 15ips NAB tape head preamp.  However I ran into problems with grounding issues.  I also wasn't able to get the low end right, but that was likely due to miscalculations on my part.  However, even with the bad hum/buzz I could sense a dramatic improvement in sound quality.  The depth and detail was immensely improved.  It was hard to go back to the stock electronics after hearing that.

So what I'd like to do is create tube record and repro electronics to replace the stock electronics.  I can leave all bias and erase functions on the stock Otari board.  I'm thinking I just need to bypass all the audio electronics, amp stages and EQ stages that are on the stock boards and insert a higher quality signal path, which can be housed in an outboard enclosure.  All tube would be my preference.  I actually have this old Teac all tube reel to reel with electronics that are based on the Ampex 350.  I’m wondering if I could somehow marry those amplifiers and EQ circuits to work with the Otari.  I have schematics for all this stuff thankfully...for both the MX55 and the Teac. 

Does anyone have any experience doing this kind of thing?  I've seen The Tape Project stuff and have read accounts on the Bottlehead forums regarding mods for the Technics RS1500.  That's actually where I got my inspiration to convert my Dynaco.  However, I've never heard of anyone doing an upgrade on the record electronics as well. 

Is it as simple as just finding the appropriate points in the circuit to bypass the stock electronics and then plugging in the upgraded outboard electroincs? 

Would anyone be interested in creating a project that could be adapted to work with a variety of tape decks?  Or perhaps one of you guys would be interested in designing something for a fee?

thanks,
Brad
 
Yeah, I searched throug the Bottlehead forums a bit.  I'll probably post something over there too.

Another thought I had was to redesign the audio cards using modern DIP op amps.  Basically a new card could be created that has the same connector interfaces and a similar routing.  But all the primary record and repro signal paths would simplified or optimized by using higher performance components.  I'm not sure if I have enough expertise to do this by myself though.

I remember there was a company that made drop-in replacement cards for old Ampex machines, but I've never seen anyone else doing something like this.

I wonder if the MX5050 would be a better platform for developing such a thing since it seems to be a failry ubiquitous machine.

Brad
 
Manley USED to make tube recording and playback electronics.  The critical stuff is the electronic specs on the heads and the rest is their doing. 
 
Back
Top