Passive monitor controller design

[Thomas W. Bethe]

Originally Posted by da goose

Hi Tom,

I get your point about the external PSU but actually... i don't think it makes such a big deal anyway.
The DC voltage has to come into the box anyway and the external DC cable crosses the signal cables externally, tends to break soon, the PSU has to be somewhere in the rack (i hate that personally) and then you have AC and DC in the area of your cables.
I use really good shielded toroidal transformers and as you can see on the picture, i have extra shielding in the PSU section (in the final version there will be just DC going straight to the board.

About the 32 steps attenuator, i never seen these actually, did you see 'm anywhere?
I'm using my prototype for some time now (24 steps) and so far it's more then enough, i made the fixed point at 12 o clock right now so i have enough steps up and down and it's easy to go back to the centre this way.

But maybe someone else has some other ideas about that?

I'm still working on it right now, i think by the end of the summer i will have some new prototypes working here.
I'm about to get the key to my new house and that is priority number one right now.
I'm also think about a router for fast passive swithcing between sources, what would you like to see in a router? any fresh ideas might come in handy thumbsup

I saw the toroidal transformer and that is always a better way to go than an open frame conventional power transformer. Thanks for sharing your ideas and asking for suggestions it is always nice to see a builder worry about the people that are going to use his device. We had a old ADM console with an all passive monitor section that used relays for the audio (they were reed relays filled with some inert gas and worked very well switching the audio without changing it). If memory serves me it had a 40 step attenuator for the main output. Nice board that worked well and sounded good.

Thanks for sharing.

[AMIEL]

Originally Posted by George Necola

it's already developed..
Dangerous MONITOR

RULES!!!

[OndesX]

Originally Posted by dcollins

I don't think most people would agree with these statements!


DC

I do definitely agree with these statements. And I add that a TVC is BTW the best way to reduce noise, separate the circuits (ins and outs) and moreover, if good trannies are used, give the most neutral sound to my ears !

OndesX

[Lagerfeldt]

Originally Posted by George Necola

it's already developed..
Dangerous MONITOR

My dealer recommended me not getting one since it breaks down too easily. He had two machines break down on the same error due to very sensitive electronics, something about chosing components solely based on sound, and not considering durability or stability, according to his explanation.

[dcollins]

Originally Posted by OndesX

I do definitely agree with this statements. And I add that a TVC is BTW the best way to reduce noise, separate the circuits (ins and outs) and moreover, if good trannies are used, give the most neutral sound to my ears !

Fine, but no transformer, regardless of design, can ever be as transparent as a resistive divider.

In mastering the signal path is (or should be) short enough that transformers should not be vital for isolation.

DC

[inlinenl]

Originally Posted by George Necola

it's already developed..
Dangerous MONITOR

yes with more like this the world would still be flat and you will fall off the big plate when reaching the egde .... cool tutt





nice looking piece off equip. da goose

p.s. when using letters/fonts ... don't use so many ... really like you're logo but the fonts on the left are IMHO pretty ugly ...
is has to look cool to sell.

[da goose]

Just a quick reply to let you all know is still follow my own topic and read all realy usefull comments.
Right now i'm in the middle of preparing for moving houses and studio so it's kind of hectic for the next 6/7 weeks, after that i will be putting up some more info for a new prototype and stuff.

Thanks so far! thumbsup

BTW, Wim, your'e right on the fonts on the left side... i was a bit experimenting wich didn't work out the way i wanted it..

[Andy Krehm]

Originally Posted by Lagerfeldt

My dealer recommended me not getting one since it breaks down too easily. He had two machines break down on the same error due to very sensitive electronics, something about chosing components solely based on sound, and not considering durability or stability, according to his explanation.

Just for the record, I've had the Dangerous Monitor ST for a couple of years and the Dangerous 2-BUS LT for about 3 years.

There was never a single problem with the 2-BUS.

With the ST, our first model had a tendency to "Christmas Tree", in other words when it received an electrical spike (which we were having trouble with), all the lights went on and it had to be restarted.

Dangerous was very, very good with support and sent us a new controller overnight and no problems since then.

Dangerous is an excellent company and I would highly recommend their products.

[OndesX]

Originally Posted by dcollins

Fine, but no transformer, regardless of design, can ever be as transparent as a resistive divider.

In mastering the signal path is (or should be) short enough that transformers should not be vital for isolation.

DC

tutt I definitely not agree with you... Anyway, try yourself ! It's indeed very easy to design, moreover if you just want an input and an output (that is no need for input selection...). A pair of trannies are in the range of 200$ (for autoformers) to less than 500 $ for the more expensive. I build 2 versions with Chinese and English trannies : any resistive gear I also designed using very high quality resistors are just useless after comparison ! It's also true for mastering.
Don't take my word, go listen to a good TVC by yourself.

Just some very interesting specs with trannies :
- first, you may deal with both single-ended and balanced gear for ins and outs (this is not the case with resistive dividers...),
- secondly, you have de facto a galvanic isolation between ins and outs (obviously not the case with resistors...),
- the previous specs have a very interesting consequence : absolute silence for the output signal ! This is really and definitely... audible !
- also, you can very easily match the impedances for the sources and the loads without any loss (you always may have a loss in resistors...),
- a tranny doesn't have any noise and nowadays distorsion is low even for high level inputs (some can accept 7 to 14 volts without major distorsion)
- last but not least, as far as mastering is concerned, I find the TVC much more easy to work with, causing less auditory tiredness, than any resistive gear, because the sound seems much more "natural" and "transparent" or "neutral", even after several hours with sometimes high output levels... The sound of TVCs is less aggressive than with resistors, it's just... louder !

The only point that must be carefully checked when you deal with TVC is the input sensitivity of the amps or amplified monitors (in my monitors it can be adjusted from -6 to +6 dB to get 100 dB SPL). For the input level, most of the modern gear (DACs) will output 2 Volts or more (in balanced mode) that is much than enough to drive most amps and active monitors !

Hope this helps !

OndesX

[api2500]

This is an age old thread but stubbled across it whilst looking for exactly that.

How did it all go?

[Steab]

Originally Posted by api2500

This is an age old thread but stubbled across it whilst looking for exactly that.

How did it all go?

Curious as well.

[Nescafe]

Originally Posted by dcollins

Fine, but no transformer, regardless of design, can ever be as transparent as a resistive divider.

In mastering the signal path is (or should be) short enough that transformers should not be vital for isolation.

DC

+1, for monitoring purpose, it must be as transparent as possible

[dcollins]

Originally Posted by Nescafe

+1, for monitoring purpose, it must be as transparent as possible

It appears in the last three years the variable-transformer has not taken over the world.


DC

[da goose]

Wow! this thread came alive again.

Actually.. i haven't really been working on it since i just have been way to busy. But about a week ago i was seriously thinking of starting it all up again because i get quite a lot of requests for it.
I did make another version as well which is beeing used in pratice in a studio in belgium and the owner loves it! sidamosaemastering
The basics are the same, just a couple of differences. It has a mute all button instead of L R mute and it also has a phaseflip on the right channel. I also made a switch on the back so that range of the attenuator can be set from 1db per step to something like 2 db per step.

Be patient..

[807Recordings]

Originally Posted by dcollins

It appears in the last three years the variable-transformer has not taken over the world.


DC

But then again neither has Class D amplification, and various other superior technologies.

There is some interesting white papers from one of the guys at Jenson Transformers I read a while back. Somehow I can't find them at the moment. Anyways it talks about noise floors and impedance mismatches and how not using a transformer can often lead to very low signal to noise.

I have tried some very high end volume transformers with mixed results. On the plus they indeed sound really clean and clear. However the gear driving them must have enough juice to handle driving this. An analogy I was told it is sort of like a little Honda pulling a large boat and trailer (meaning a bit difficult), which sort of translates to reduced dynamics and control. Again gear dependent. The better equipment that I tried it on like Esoteric's SACD player drove the amps to amazing levels and maybe better than any preamp I had at the time, being either tube or solid state. However with a few phono stages it just did not work as well, and with some cheaper sound cards.

Short answer it all comes down to design and not all transformers are equal in quality (to say the least).

[api2500]

Originally Posted by da goose

Be patient..

We are Gearslutz. You do know that?

[dcollins]

Originally Posted by 807Recordings

But then again neither has Class D amplification, and various other superior technologies.

There is some interesting white papers from one of the guys at Jenson Transformers I read a while back. Somehow I can't find them at the moment. Anyways it talks about noise floors and impedance mismatches and how not using a transformer can often lead to very low signal to noise.

What the other poster was talking about was using a variable transformer instead of a conventional level control like a pot or stepped attenuator.

Jensen makes excellent transformers, but they aren't volume controls.


DC

[807Recordings]

Originally Posted by dcollins

What the other poster was talking about was using a variable transformer instead of a conventional level control like a pot or stepped attenuator.

Jensen makes excellent transformers, but they aren't volume controls.


DC

Sorry if I was not clear, but I do understand that. It was early and I mixed a few thoughts at once. :-) I still think that transformers for volume controls can sound quite amazing, but it requires a very good source to drive them. At least that was sort of my point. My other point was not so relevant to this topic but was more to the point that transformers can be good for isolation when implemented correctly in a circuit. They should be transparent if done well.

Short answer:
It comes down to the circuit design in the end.