transformerless compressors

maybe the wrong forum for this. But what if any are the advantages to having a trnsformerless compressor. Reason I ask is this. I have a buddy working at a mastering studio in town that prides itself on the fact most of the gear is tube and that they havn't changed it out since they oppened. For comprssion the are using a modified LA2A which as discribed by them is transformerless. They don't mention of op-amps. So I am wondering what advantages this would have from a design point other then less $.

In the LA2a, the input transformer limits the bandwidth quite severely. 35kHz is a long way down there.

The Mastering Lab used to take out the transformers, specifically because even two consecutively-numbered units could have different-sounding HA-100X's in the input stage. There's so much friggin'gain in an LA-2a (you never use it all!) that the transformers can be removed or at least stepped down to lower-ratio versions.

Keith

your buddy is probably running a mastering suite that is unbalanced and so has less circuitry and signal path.

This is great but does need carefully attention to the system as a whole and grounding and external noises.
Usually these places don't change and the owners CHOOSE to keep the stuts quo for long periods of time.
This seems to be backed up by your buddy.

The advantages of transformers do become more obvious when there is many changes and the distance between gear means different mains circuits and different noise issues in different buildings.

Transformers can also be one of the simple ways to impedance convert and connect things like tubes and mics and convert volts to current and so on.
Where an energy transfer is required the transformer can be a niffty single unit way of changing the nature or balance of the energy but still get the full energy transfer required.

:grin:
another one of Kev's strange left of centre ways to describe some thing that will continue to intrigue all people who love audio. The transformer is a wonderful problem solver and just when you think you have it worked out, a situation will come up that may send you back to your reference notes.

we love transformers

[quote author="Kev"]The advantages of transformers do become more obvious when there is many changes and the distance between gear means different mains circuits and different noise issues in different buildings.
[/quote]

Spoken like a true broadcast engineer. Good post, Kev.

SSL tech how did you know? wow your good I owe you a coffee and doughnut. :wink:
Thanks for the information guys. :grin:

I guess another way to put it is that transformers add some nonlinearity, just like any other real-world component. Excellent transformers distort the signal less than cheesy transformers.

A mastering suite is usually a self-contained "island" that, with careful design, does not need balanced lines or galvanic isolation between parts of the system. So you can remove unneeded components and unnecessary distortions. In a broadcast or other "large plant" environment, or in any situation involving unpredictable reconfigurations, the added component count of balanced circuits or the nonlinearities of transformers are usually lesser evils compared to the problems they prevent.

> a modified LA2A which as discribed by them is transformerless.

Look at the LA2 schematic. The core is unbalanced: resistor-pad in front, single-ended WCF output. The opto-resistor works great unbalanced, as does the sidechain, so they choose to use an unbalanced makeup amp too. Transformers are used only to break ground loops and get a little (not much) "free gain".

Bypassing the transformers gets rid of transformer flaws and also works the LA2 core at a little lower (cleaner) level. Without transformer isolation it is (as Kev says) hard to use in a big studio complex, but (as Dave says) a mastering suite is an island and often very stable.

Contrast with Vari-Mu, where a transformer is about the only sane way to drive the vari-gain stage. Until the advent of good opamps, diode vari-loss stages also made a lot of sense with transformers.

Prr ,KEV,SSL thanks so much for the information. As always I have much tro learn oh the how and why but I am good at the doing.

:guinness: :guinness: :guinness:

pucho-

easy answer, it sounds different. Im mastering a project right now and one choice in the signal path was adding or subtracting transformers, just sounds different...

dave

It became known as the "Doug Sax" mod, though I believe it should more accurately be attributed to his brother.

Bud Wyatt also worked at the Mastering lab, as has (I suspect) Bob Neill. Bob makes some stunning mics, Bud makes some stunning everything!!!! Last month I had the honour of working in Bud's workshop for a week while he was out of town. I was super-careful to leave everything exactly as I found it, (working on Pultecs, Fairchild 670's, RCA BA-11's, and lotsa old really nice stuff!!!) but it was very cool using his gear... lotsa old-skool test equipment, no super-computerised distortion analysers here!!!

The Mastering Lab also did those stunning crossover and cabinet replacements for the Tannoy monitors.

Those guys are good. There's not much imaginary hype about the place, they really are good. They don't need the transformers, so they took them out and extended their bandwidth. The output stage needed some re-working, but the input stage was a pretty-much straightforward iron-pull.

Keith

The Mastering Lab also did those stunning crossover and cabinet replacements for the Tannoy monitors.

Click to expand...

I have heard those B4 and been searching for them used. The M company is re making them but for 5000 a complete pair way out of price range.

It became known as the "Doug Sax" mod, though I believe it should more accurately be attributed to his brother.

Click to expand...

yeah his brother designed all their stuff.

Hmm i got some Tannoy 10's that are lacking in the high end for sure ,
anybody got an idea of what the crossover was ? mods ?