UPS delivered my Studer A807

[esb1954]

I watched in horror as the UPS driver cartwheeled the box off of the truck.  The outer box was all torn up with styrofoam peanuts falling from the box.  The inner box with the unit was intact.  The machine appeared to have survived the ordeal.  I put on the side panels and turned it on.  The tape playback mechanism worked like a dream.  Put on a tape and no sound.  Took off the bottom panel and took a look.  One sound card with its numerous pins had fallen out of the sockets.  The other sound card for the other channel was partially out.  The unit must had taken a hard jar or been dropped by UPS.  I put both cards back in.  When putting the unit on it's back to be opened there was still something loose inside.  Could not find anything.  Put the deck back together and I put on another tape to see if it would work and to my surprise, there was music.  All is working.  This is a non modified deck (no direct head out) and is a reproducer with no record or erase head.  I have Tenor 15 wi monoblock amps.  The Tenor is an integrated amp and can also be used in bypass mode.  I wanted to try the Studer using its own electronics first.  I also have a Otari 5050 mxBII 2 with a direct head out to a Seduction tape head preamp to a Foreplay III line stage.  I hooked the Studer directly to my Tenor and it was not as good as the Otari(with the Seduction and Foreplay) playing Tape Project tapes.  I then tried the stock Studer and ran it through the Foreplay to the Tenor (bypass mode) and what a difference.  Much better than the Otari with the direct tape out.  Much more detail.  The only problem is I am at the first click on the volume of the Foreplay and it is at a moderate volume.  Will it hurt anything by going directly out the Studer with its electronics into the Foreplay?  The Studer tape transport is on a whole different level from the Otari.  Now I have to decide if I want to do a direct head out with the Studer. 

[Ki Choi]

Hi Mike:

You are fortunate and good to be able to put the Studer back - making music after the shipping damages.  In most cases, the reel turntable spindles are bent or broken off, tension sensor get jammed...etc.

The A807 is calibrated to the pro +4dB for 0VU normal operating level with 1.225V output.  You will need to calibrate it to the consumer level of 0.779V as 0VU. 

Do you have the manual?  The procedure to calibrate the recorder is very well written in the manual and you can do the work if you have the correct test instruments.

[esb1954]

Ki Choi,

Thanks for the reply.  I believe that jumper JP3 on the audio card can be moved to the B position and this will change the output for audio use.  There is a preamp card behind the head stack.  The cable from this preamp connects onto the audio card (reproducer amp).  Also connected on this card are the wires that go to the audio out xlr.  There must be a way to run a wire with connecters to bridge and connect these wires to effectively by pass the repro amp.  I do not know how the preamp that the heads are connected to would effect the sound?  There is -18 db off of the preamp.

Mike

[Ki Choi]

Mike:

The jumper change is needed but you would also need to calibrate the output levels from the audio board to match your chosen operationg level, VU meters adjustments for 0VU, and output level adjust from the control panel playing the calibration tape.  If you subscribe to the Tape Project tapes, Doc B would send you the IEC 15 ips cal tape.

Again, I have not dug deep into the A807s to have any detail information but before you disconnect the repor head wires from the input of the pre-preamp under the headstack, you should read previous posts from others includeing Doc B's first hand info on how to direct wire the A810 to minimize the hum and other noise.

Ki

[esb1954]

Ki,

What would happen if you left the preamp behind the heads in place and do not try to go directly off of the heads.  Make a smaller circuit card that you could plug in the cable from this preamp into before where it would enter the audio card. Have a volume pot so you could reduce the output(gain) from the preamp and then hook the cable that leaves the audio card to the XLR output to this smaller card. From what I understand this preamp only adds gain.  The cable from the preamp connects to the audio card near where the cable to the XLR leaves the audio card. This would bypass the audio card.    Do you think I could then go out to the BH Seduction tape head amp?

[Ki Choi]

Hi Mike:

We may have some confusion - I checked the manual for my A807 Mk II and confirmed that the heads are wired directly to the DB25 male connector on the headblock and it to be plugged into the machine chasis.  Thus, the head wirings dosen't pass through the preamp within the headblock.

If you are refering to a repro preamp that is located behind the headblock as a part of the assembly in your machine, you might be talking about Studer A810, A812 or A820.

Let us know the model and version number of your Studer.

In either case, the A807 Mk II repro head is the same one used in A810 that Doc B had successfully direct wired to a Tube Repro.


Ki

[esb1954]

Hi Ki,
I have a Studer A807 MKI.  It is a playback only machine.  I talked to Steve Smith and he said the head was wired directly to a preamp which is a part of the head block.  From there three wires lead out to a separate audio card (amp) for each channel.  They plug into these cards.  Near this is a connecter to which the wires from the XLR's plug into the audio cards.  He had the idea of making a smaller card that these same two connecters from each audio card could plug into(and by-pass the audio cards).  I believe the preamp from the heads add 36 db of gain (-54 db at the head and -18 db after the preamp) .  He said a pot could be placed on the card to lower the gain. I just do not know if this would work.  Could you then go into the BH Seduction tape repro and would it sound any better than stock?  The A807 running with its own electronics and through the Foreplay line stage sound better than my Otari 5050BmkII2 with direct head out into the Seduction repro. 

Mike

[Ki Choi]

Hi Mike:

I could be wrong (that's a rare event ;-)) but the Repro Preamp (1.727.430) in A807 MkI is not a part of the Headblock assmebly (1.050.340).  The schematic for the headlock still shows the heads wired to a DB25 connector instead of to the Repro Preamp.  The connection from female DB25 (a part of the chasis) is converted into a ribbon connetor to the Repro Preamp outside of the headblock. Maybe your A807 MkI had been modified to by pass the M/F DB25 connectors and the ribbon cable/connector.

If you can post some photos of your Studer, it would clear up the confusion.  My bet is that you have a different model than an A807 but then again, I could be wrong...

thanks,
Ki