I don't know if this is the correct area for this thread but here goes anyway. I have about 200 hours of old demo and live recordings on cassette tapes which were recorded in the 1990's on my trusty Yamaha MT1X. I'm trying to get these onto digital and failing miserably with my current equipment. As my Focusrite only has two channels, I thought I would hook up my old Lexicon Alpha for the other two and use ASIO4ALL. This only caused severe artefacts throughout the recordings. Tried JACK and still no good. I've even resorted to attempting two separate recordings but the tape speed on each recording is marginally out each time, so that failed.
Now the question - my old DAW computer is currently being used for Office applications, running on Windows 7. If I installed Sonar onto it and used my Alpha soundcard could I record 2 channels onto it and 2 channels onto my DAW machine and later import the "Alpha" audio files into the DAW project? I'm not going to spend a lot of time setting all this up just to find that there are timing issues again.
Hope someone out there can advise.

There is only one way to do this my friend and that is using a 4 input device.
You have already figured out that the capstan fluctuations/drive motor have minor differences on each pass.
My suggestion is to either send them out to be transferred. However to be quite honest, for the money it will cost to transfer 200 hours (depending on IPS that's more than 200 tapes) some company's can charge up to 30 bucks a tape:
http://www.audiomover.com/transfer-4track-to-digital.html
You would be better off buying a 4 input device.
 
If you don't want to buy a device but want it done right (with good pre amps) just send it away.
 
There is one other way that people sometimes over look.
Using an older style Digital recorder that has 4 inputs. I had a Tascam 2488 that had 4-8 inputs on it a while back before I switched over to a newer unit (Focusrite Scarlett 18I20). I would use the Tascam to transfer and then burn it to disc.
 
Also remember if you send it out leave detailed Pitch information. I always ask my customers for IPS info.
Some companies just set it at 1 7/8 and call it a day. you need to be clear you want 3 3/4 and what pitch (what you set the Vari-speed knob at).
Back in those day we cranked that thing up to gain maximum speed/better fidelity. 
 

Hi Charlie - thanks for getting back. I was hoping that a single pass onto two computers would solve the problem but I suppose I really knew that a  4 input device was going to be the answer.

I did a similar transfer when I went from a Fostex VF160 8 track recorder to Sonar.  
I transferred two tracks at a time as I had a two track recording interface unit. 
I did have to do some (very little) track alignment but that was all.
 
It was time consuming but didn't really cost me anything but my time. I only had about 10 songs to transfer.  However with a large amount of recordings it would have been different and I would have had to consider whether I wanted or needed to transfer that large amount. 
 
 

I'm thinking that doing individual 3 minute demos might be possible using what I have - with a bit of patience. The difficulty would be the longer live recordings when any timeslip would not be easily rectified. It's looking like a shiny new 4 input device is looming.

I recorded by old 4 track cassettes, using my old, but trusty Walkman Pro cassette player into Sound Forge. I split the left and right of both sides into separate tracks. Of  course two of the tracks needed to be reversed. I cleaned up the hiss, and imported the 4 tracks into Sonar, and aligned them up, and re-mixed. It's very tedious, but it worked. 

Im not trying to disrespect anyone's opinions but trying to align fluctuating tracks is a nightmare.
Trying to match individual tracks recorded on separate passes (The phasing, the out of synch flutter) sounds awful.
DC servo capstan motors never sound the same.
 
Here is a good article from sound on sound:
https://www.soundonsound.com/techniques/transferring-old-multitrack-projects-your-software-daw
 
 

Thanks again to Charlie for the article. I don't think that I would have the time for all the fancy editing and aligning required for using my current equipment. Converting 200 hours worth of 4-track would be quite an investment in time, plus the live stuff would just be impossible. I should have thought about this when I upgraded my system last year and bought a 4 input interface. Never mind - Christmas is coming!

Duplicate post.

I wish you lived closer, for 4 track transfer I charge 10 USA dollars a tape (60 min in half=30 on 1 7/8 ISP).
That includes RAW track conversion. for a little more I can do noise reduction and restoration.
I do everything short of baking tapes which I did years ago but stopped.
Most places charge up to 30 so you could see how investing in a device is worth it.
 
Just a suggestion but this is what you want-
Focusrite Scarlett 6i6
https://us.focusrite.com/usb-audio-interfaces/scarlett-6i6
 
They can be bought used for under 200. They have 2 pre amps, 4 line inputs and 2 outs
this equals= 6 total inputs. They also have 2 headphone inputs with separate volume controls.