Dual TG 12 Tube Tape Recorder - Any interest? (Schematics)

[thomasdf]

Hi folks

I have the opportunity to get a Dual TG12 tape recorder. It is a 4 track tube tape recorder from the 60s, made in Germany.
I have all the tape recorders I need, but this one might be really cheap (read : free), so I was wondering if there was any way of hacking into it to turn into a stereo tube processor of some sort?

Here are the schematics.

I am particular interested in the output amplifier and its tone control. I believe that if I switch the 2 output transformers for something like 10K:600 transformers I may have a pretty cool stereo line amp + tone control?

Any thoughts?

Maybe it's just a silly idea...

 

[thomasdf]

Here is a close up on the output amplifier's schematics

 

[EKADEK]

loving this output stage. it seems to be just like that whole pile of beaut german radiograms. grundig. telefunken. nordemende etc. a signal triode and small output pentode(triode) run hot in a class.

a 'normal' 10k/600 transformer will make a sound but will change out the pentode condition. wont really fire up. .

and. i think that a normal 10k/600 trafo is probable not designed to have (whatever) dc current running through it.

this amp is all over the place with it's tone control flexibility . there's a volume control and then treble tone control into the pickup amp and then plenty of response control feedback switched and set network circuitry too, lovely.

seems like this is the that kind of output stage that delivers a low level listen that is extended fat- yet- not- flabby in the bottom with controled  tingling crisp at the top.  with a some delicious tube and phase distortion. 

a really clear fat satisfying result from a small 
hi efficiency german speaker. 

as a line stage - u need the right DC capable trafo probably more like  custom 3K / 600 / 8.    ? maybe . and then u'd be feeling  the feedback tone control in your line sound.

the line sound would  be pretty LOUD!  too i reckon. variable attenuator network on 600 ohm output.?
i want to build this one.  i have a danish radio cab with a stuffed chassis but lovely euro 6 x 9 . will do it sometime.  kind of esoteric..

 

[alexc]

plate-to-voice coil  traffos for this kind of thing were/are avail on ebay - telefunken 12Kohm single ended for el95 with around 2Wrms  to a 4ohm load at several % thd.

Reasonably affordable and of a fairly decent build quality - I'm using them as either 'monitor amps' (with speaker load connected) , or  'thd generators' (with a dummy load connected) - in a tube preamp rack.

el95s are a really interesting toob Quite a punch for such a low heater requirement.

For use as a line output, I'm sure the cheap 'se teles' can be set up with a dummy rated load on the secondary, then hang some parallel'd 'line out' feeds across it.

Wasteful of output power,  set up that way, but who cares ? You can get an 'old school crunchy' line-level distro amp going for low cost. A few Vpp of signal would be available for sure.

And quite variable thd too, set up with some triode/pentode switch and variable/switchable nfb into a driver stage of one's choice .

In my case, I'm doing a rack preamp with both point-point tube blocks and discrete sand-state modules for various I/O functions. Kind of the best of both worlds - gonzo thd with the german masters with the mod cons of discrete+traffos

I'm nearly done with the psu - an external 1RU job that powers the 2x remote preamp racks with 2m supply cables.

Being for SE tube usage, it benefits to have a very low ripple HV, so nice to have some regulation. I'm using some ebay sino pcbs for that role. PLUS no 'onboard hum' to deal with near all the signal traffos  (yay!!)

---

Anyway - good luck with it  el95s se are cool!