Why not mults on DIY preamp outputs?

[JW]

One of the really wonderful things about recording on an actual recording console is the ability to monitor oneself in real time made possible by usual multiple busing available. Take that preamp out of the console, rack it up and now we're reliant on post conversion monitoring, "direct moniting" DSP cards etc. Why not just add mults on our preamps? They'd function like a console that way. I don't see any harm as long as one is mindful not to load the output with too(two) low impedance loads. Typically, a headphone amp or input to a separate monitor mixer's line input would represent a reasonably high impedance input I would think.

Anyway, the difference I can think of would be that the multiple outputs in a recording console are often sourced from the unbalanced opamp output before the pan network, rather than after an output transformer, but does it really matter? For a post transformer secondary example, in Jeff's (API's) ACA output bus, the 2503's have 1 output + 1 mult on the same winding. I'm currently using this to feed both my main mix converter inputs and my high impedance monitoring. Can't hear any ills, but that doesn't mean there aren't any. But isn't that what these mults are for anyway?

So why not on the output of stand-alone preamps as well, which would be very useful (though situation dependent) Like, don't try to feed two Pultecs or something. . . . But if we're building them to use anyway, we are capable of being mindful when in use.

 

[JohnRoberts]

If you are doing a design for yourself you can add as many outputs as you want. Hardwire mults are cheap but could degrade the balance of an interface if one of the multiple units plugged in is not balanced. Of course you could design in multiple independent balanced outputs. It's only money and when its your money its your call.

JR

 

[TwentyTrees]

I agree - I did the same with my Helios clones recently, multed outputs for exactly that reason. One of the joys of DIY!

 

[NOON]

Many preamps do have multiple outputs and using an external mixer is exactly what I used to do 10-15 years ago. These days computers are fast enough and interfaces easy enough to use with great software mixers that I save all the desk space, cabling and extra hassle and just do headphone mixes in the box. The main change was getting an interface with a decent 'real-time' software mixer, monitoring via the recording software is still a PITA.

 

[NOON]

Having said that, in a really busy live location recording session I still prefer a hardware mixer for speed of being able to make changes without swapping windows and navigating the software patches / routing. That's possibly a legacy of my age though, I straddle the analogue and digital eras and used hardware mixers for years before software was good enough. 'The kids' these days are probably faster and more comfortable with software.

 

[Newmarket]

Of course you could design in multiple independent balanced outputs.

Indeed. An opamp amp/buffer stage. Z balanced output + a socket (TRS to save panel space). Job Done.

 

[JW]

Okay, Thanks JR

Interesting. Well, an Adcom 535 amp definitely is unbalanced. I'll have to research this matter a lot further I suppose. Would two transformers off the same opamp output be a more safe way to approach a mult? (especially when one is an unbalanced speaker amp input?)

 

[Newmarket]

Okay, Thanks JR

Interesting. Well, an Adcom 535 amp definitely is unbalanced. I'll have to research this matter a lot further I suppose. Would two transformers off the same opamp output be a more safe way to approach a mult? (especially when one is an unbalanced speaker amp input?)

tbh you might be overthinking this. An Opamp stage and you're done although I'd suggest an Impedance Balanced or Ground Sensing output (to maintain a useful degree of CMRR into an unbalanced input). Unless you'd want to go to a Cross Balanced output - but that is significantly more complex to implement.
Obviously you can 'go transformer' but it's not necessary unless you are working in extremely adverse conditions or want some "Iron Magic" (tm!) in the signal.

 

[moonTV]

Hi,

I'm new and wasn't sure this really merits a new thread, so please forgive me if this is too off topic but,

Would it not be possible to take this a step further and take an out from before the transformer in a tube DI?

Could you just cap couple your signal and run it through a pad and something like an INA137, and from there make some bal/unbal outs, and spend money on jacks and chips instead of iron and get a little more functionality in exchange for ?? I'm sure I'm just parading my ignorance here, but I'd really love to know just how.

Sorry if this is sacrilege, or a bad idea due to design considerations; it's either that or I simply don't know enough to find it by searching. That the only two people I've found doing this are on diyaudio isnt exactly encouraging. Either way thanks for your time and consideration.

 

[abbey road d enfer]

Would it not be possible to take this a step further and take an out from before the transformer in a tube DI?

Could you just cap couple your signal and run it through a pad and something like an INA137, and from there make some bal/unbal outs, and spend money on jacks and chips instead of iron and get a little more functionality in exchange for ?? I'm sure I'm just parading my ignorance here, but I'd really love to know just how.

There's absolutely nothing wrong with that approach. However, multing outputs is not condemnable, as long as some rules are obeyed, like not exceeding the global load and making sure the different destinations are not conflicting.
In particular if one of the destinations is unbalanced, it will unbalance the whole connection, and any disturbance on one will be transferred to the other.
That's why using separate secondaries is recommanded.

Sorry if this is sacrilege,

As it is, many tube preamps have solid-state outputs.

That the only two people I've found doing this are on diyaudio isnt exactly encouraging.

What is it they are doing and why not encouraging? Do you have a link?

 

[sahib]

I do not mean to pimp our equipment, but to stimulate some ideas.

A few good examples for this in 500 format.

MICPRE ONE has a second identical output stage which can be switched as a second monitor output for the mic-amp stage or DI output for the instrument input stage. This is through a TRS connector placed on the front panel. The output stages are opamp based (OP275)

Advance version of our racks offer unbuffered parallel input/output in passive mode and buffered when the Balancing Card is used. They can also be switched as inserts. Balancing card is based on THAT 1246 and 1646.

I have also prototyped a few cases in 1RU format. Picture attached. This again is basically the same layout as the 500 except in horizontal format.

 

[ruffrecords]

Mults do not need to be complicated. Just add an extra XLR in parallel with the main one. As long as what you connect it to has bridging inputs you should be fine.

Cheers

Ian

 

[amplexus]

Also if you’re using half normalled patchbays (even in a small studio setup i’m an advocate of a good patchbay for flexibility’s sake) then you have mults baked right in!

 

[Ricardus]

Also if your using half normalled patchbays (even in a small studio setup i’m an advocate of a good patchbay for flexibility’s sake) then you have mults baked right in!

Yup. And I never do a patchbay design without adding some parallel mults as well.

 

[ruffrecords]

Also if your using half normalled patchbays (even in a small studio setup i’m an advocate of a good patchbay for flexibility’s sake) then you have mults baked right in!

All Neve patch bays had groups of mults.

Cheers

Ian