Best way to hook up a -10dBV console to a +4dBm tape recorder
- Thread starter timkroeger
- Start date
timkroeger
Custom Title User
Cory,
thank you so much for the schematics, I'll have a look at them tomorrow and post the ATR schematics.
Hehe, I didn't see the putput amp at first but now I can't "unsee" it. Can't stop chuckling, either. Hehe...
I believe they figured it was a good thing to put the balancing amplifiers on the dbx boards. On input prepare the signal ("normalize" signal, optionally add dbx NR), then prepare for putput again (optional dbx, then balance).
Cheers
Tim
thank you so much for the schematics, I'll have a look at them tomorrow and post the ATR schematics.
I looked at the 48-OB again too...the balancing amps are actually on the amp cards in that deck, but that (like the 58-OB) has unbalanced input and putput...sorry...output jacks as well as balanced jacks on XLR's.
Hehe, I didn't see the putput amp at first but now I can't "unsee" it. Can't stop chuckling, either. Hehe...
I believe they figured it was a good thing to put the balancing amplifiers on the dbx boards. On input prepare the signal ("normalize" signal, optionally add dbx NR), then prepare for putput again (optional dbx, then balance).
Cheers
Tim
timkroeger
Custom Title User
Fired up an 8 year old scanner, because the multi purpose scanner/fax/printer/whatnot went dead after 2 years of use. The scanner is still working nicely...
You can download the ATR-60/16's dbx schematics here. Judging from the schematics I think I would have to tap into each channel's dbx PCB card whereas the XLR and Sub-D connectors are connected to the dbx mother PCB. That sucks. I don't see a way to route the unbalanced level I/O levels to the dbx mother PCB. We'll see.
I'll check for amp PCB levels, when I have more time... Hopefully soon
Cheers
Tim
You can download the ATR-60/16's dbx schematics here. Judging from the schematics I think I would have to tap into each channel's dbx PCB card whereas the XLR and Sub-D connectors are connected to the dbx mother PCB. That sucks. I don't see a way to route the unbalanced level I/O levels to the dbx mother PCB. We'll see.
I'll check for amp PCB levels, when I have more time... Hopefully soon
Cheers
Tim
evm1024
New member
Need better scan
Hi Tim,
You need to make a better scan of those schematics. Very hard to read. With that said - What is the R/P amp?
U001 is the input amp that converts balanced to unbalanced. I can't quite read the resistor values so I cannot tell the gain of that stage. Q005 and U006 are fet (analog) switches that pass the signal pre DBX (U005) or post DBX to teh R/P amp (record/playback?). The output of U005 is where to tap the unbalanced signal in.
Signals from the deck are switched through Q007 and Q008 which are fet switches. When Q007 is on you get pre DBX, when Q008 is on you get post DBX. These feed U002 (section 2?) which feeds the unbalanced to balancer converter U003. The output of U002-2 is the likely place to get unbalanced output.
there should be some level diagrams somewhere inthe manual that may show if it is -10 dBV at those points. I would suspect so....
One issue may be phase. Many amplifier configurations invert the phase in one stage then re-invert it in the next. With an even number of inversions you get an in-phase signal chain. If you take out one of the inversions you will get an out of phase chain (180 degrees out of phase....)
Regards, Ethan
Hi Tim,
You need to make a better scan of those schematics. Very hard to read. With that said - What is the R/P amp?
U001 is the input amp that converts balanced to unbalanced. I can't quite read the resistor values so I cannot tell the gain of that stage. Q005 and U006 are fet (analog) switches that pass the signal pre DBX (U005) or post DBX to teh R/P amp (record/playback?). The output of U005 is where to tap the unbalanced signal in.
Signals from the deck are switched through Q007 and Q008 which are fet switches. When Q007 is on you get pre DBX, when Q008 is on you get post DBX. These feed U002 (section 2?) which feeds the unbalanced to balancer converter U003. The output of U002-2 is the likely place to get unbalanced output.
there should be some level diagrams somewhere inthe manual that may show if it is -10 dBV at those points. I would suspect so....
One issue may be phase. Many amplifier configurations invert the phase in one stage then re-invert it in the next. With an even number of inversions you get an in-phase signal chain. If you take out one of the inversions you will get an out of phase chain (180 degrees out of phase....)
Regards, Ethan
timkroeger
Custom Title User
Ethan, sorry for the low quality scans. I updated the zip and uploaded 300dpi scans. Please check it out. I had a signal level chart in one of the earlier posts. I figured the points to tap into the circuit would be to the right of C005 so I get either direct -10 dBV in or post dbx of the "injected" -10 dBV and to te left of C006 (same potential as output of Q007, Q008, Q009) so I get either dbx or no dbx just before the right U002 (2/2). The U002's are both labeled (2/2), so I mean the right on, not the left one. I don't know about input/output impedance though and how that would have to be designed.
Yes, R/P amp is record/play amplifier.
Yes, R/P amp is record/play amplifier.
miroslav
Cosmic Cowboy
Here's one of those Fostex 5030 Line Amps on eBay.....
http://cgi.ebay.com/Fostex-Line-Amp...emQQptZLH_DefaultDomain_0?hash=item45f21d1f3e
http://cgi.ebay.com/Fostex-Line-Amp...emQQptZLH_DefaultDomain_0?hash=item45f21d1f3e
evm1024
New member
Sorry for the delay.....
Getting close. The level diagram (now how did I miss that?) does not quite match up with the schematic. Odd.
I think that you can tap -10 dBV in to your deck on the left hand side of C5. This will then use C5 as a DC blocking cap (this is pin 7 of U001 (1/2)) And take your output to the right of C6 (U002 (1/2) pin 3) for the same reason. C6 blocks the DC offset if any.
Of course either side will work. You could put in a set of RCA jacks like a send-receive pair and that the input and output differential amps out of the picture.
The signal levels are -10 dBV at these points.
As for the schematic typos, you can guess which half of the opamp is 1/2 and 2/2 by looking at their pins. 1/2 outputs on pin 1 and 2/2 outputs on pin 7. Of course they could mess up the pinouts too.....
For what it is worth the gain calculation for the input differential amp (U001-1/2) goes like this. Because R1=R2 and R3=R4 the gain is R2/R1. So, 1.3k/5.3k = 0.255 which is 20 Log(0.255) = -11.97 dB The input is + 4 dBu and +4 -11.97 = -7.87 dBu. Converting dBu to dBV give us -7.87 dBu = -10 dBV.
Regards, Ethan