-10dbv da converter outs to +4dbu tape recorder ins issue

[tedsorvino]

Hi all.
So long I’m using my presonus output da converters which are +4dbu (balanced) to send tracks from my daw to my Brenell 8 track tape machine which has +4dbu (unbalanced) ins. The vu meters work as expected. All good.
But when I try to use my other output da converters (either Motu or Behringer) which are -10dbv balanced only, in order to avoid clipping the vu meters on the tape machine show very low values (-10db minimum scale) and the signal/noise ratio is not good.
In all cases the rme interface sends around -18dbfs max. digital signal to the da converters. All signals measured for around 0db vu max. output.
Ok I can stick with the only da converter that I have that works well, but ….just in case …
Could I do something to convert the -10dbv to +4dbu (8 tracks) without having to buy expensive external devices, extra mixers etc.?
No problem to mod the devices or build a “-10dbv to +4dbu converter” or something with opamps etc.
Thanks in advance

 

[RRuskin]

Both Fostex and Tascam made converters that can go in either direction. PM is on its way.

 

[tedsorvino]

Both Fostex and Tascam made converters that can go in either direction. PM is on its way.

Just to mention. I already own a Presonus Digimax Fs unit which is an excellent +4db da 8 outs converter (and very decent ad 8 ins with preamps).

 

[sweetbeats]

Just to mention. I already own a Presonus Digimax Fs unit which is an excellent +4db da 8 outs converter (and very decent ad 8 ins with preamps).

I have two of them. Agreed, great box. Hard to find something that has 8 inputs all with pre-ADC hardware insert points and +4dBu pre-ADC analog direct outputs, along with the versatility of mic, line and hi-Z options on the 8 inputs, and the typical 8 +4dBu DAC outputs…and the Lightpipe I/O, 96kHz-capable…phantom power across all inputs…wordclock I/O on BNC connectors…the clock at the time was next generation, and I often use it as the digital clock master…it sounds better…versatile options for sync (BNC or Lightpipe). I also have promotional information that touts substantially higher audio power rails for at least the mic amps, which are discrete class A…so high-headroom. They do sound good IMO. I opened one of mine up at one point just to see the build and it’s nicely done…I did see the discrete mic amp, and then 33078 opamps, which are not cheap and look really good on paper…my Studer console uses them for a lot of stages…and AK5384 converters…a lot of through-hole components including the opamps and electrolytic capacitors…kind of a sleeper…came out during a shift toward heavier ITB reliance, so a lot of similar-class products that were contemporary lacked the analog interface options with the pre-ADC insert points and outputs…but it still benefitted from later-generation clock and converter tech and opamps, and precedes the heavy shift toward all SMT tech on the build…apologies to the OP for the detour.

On-topic, sure you can build your own active bump box, but after paying for the components and chassis and using proto board or having PCBs made you may as well just get one of, or an array of the Fostex or Tascam boxes. I’m partial to the Tascam offerings just because they are more common. I have 4 of the LA-40mkII boxes for 16 channels of bi-directional -10dBv unbalanced to +4 dBu balanced conversion and vice-versa. You would need two of them. Or you could get one LA-80 and one LA-81 for 8 channels bi-directional. If you are just needing to bump from -10dBv to +4dBu then you could get away with just the LA-80. I also have one of the first generation LA-40 boxes, which offers some unique features over the mkII including a higher-headroom discrete balanced output stage. You can find the service manuals for the first two generations of the LA-40 series around the interwebs if you wanted to use the schematics and parts lists as a template for your own DIY design.

 

[tedsorvino]

I have two of them. Agreed, great box. Hard to find something that has 8 inputs all with pre-ADC hardware insert points and +4dBu pre-…….

Thank you for the very informative post.