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Anyone made a direct-coupled project? Only studio-manufacturer I can think of that makes true direct-coupled gear is GML. Be good to hear any suggestions for projects.
I'd also be interested if anyone can cite examples for off-the-shelf direct-coupled gear other than GML. Plenty of firms such as Millennia advertise their kit as "transformerless", but I can't think of any true DC units other than GML.
A lot of oems advertise their units as "DC-coupled", but unless they state: "DC-coupled throughout" wouldn't you suspect marketing to be at play? i.e. Only one stage is DC-coupled.
[img]graemlins/beerchug.gif[/img]
"actually, I'm not a trained technician at all, I used to play piano in a brothel but business was bad, so..."
"transformerless" obviously doesn't mean "DC coupled"
Would you include DC servo circuits, and do the GMLs DC to the outside world??
The Hardy M1 uses transformers to isolate from the outside world but has no caps in the signal path and uses a DC servo.
I've done some tube circuits were you go from plate to grid at 250-300v with no cap. But then every Marshall worth anything does that. But it's not completely coupled that way.
Good question!
Hi Ciminosound. The 8200 is fully direct-coupled, there are no caps or chokes in the path whatsoever from xlr to xlr. It is a mother internally, even at the price I think it's good value.
Direct-coupling requires careful servo design for sure (discussed here recently, my brain is still aching [img]graemlins/silly.gif[/img] ) .
My definition would be to the Massenburg protocol: no trannies, caps or inductors...
Anyone know of more gear like that? [img]graemlins/beerchug.gif[/img]
"actually, I'm not a trained technician at all, I used to play piano in a brothel but business was bad, so..."
Must be a mother inside, if it's correcting for 48V offset at the microphone inputs.. The SSL 9K is also DC to light, save input DC blocking caps on the pres.
So what's the big prob with caps? I think it's a waste to try to eliminate a few in one box, when the next box in the chain is full of them..
Shalimar
".. interesting on the first hearing, boring
on the second and increasingly annoying thereafter.. " Graham Hinton SSL engineer, on surround sound
And is a DC servo not considered in the signal path? And a DC servo isn't DC coupled. Or can one put a servo on the servo on the servo on the servo...??
Ten years ago, 'one point DC servos' was all the rage in the DIY hifi world in my country.
Shalimar
".. interesting on the first hearing, boring
on the second and increasingly annoying thereafter.. " Graham Hinton SSL engineer, on surround sound
I'm not sure what the big deal is about direct coupling...choose low offset devices, and maybe trim them even closer towards zero volts, and you should be able to get away with direct coupling. But in the end, you're going to want at least one servo stage to take out any DC that may have gotten into the device from something the user has plugged in (i.e. you may have trimemd out all the internal offsets, but the user plugs in a crappy source with 15 mV of DC on it, and you just amplify it).
Servo circuits are only quasi in the audio path...for all intents and purposes at audio frequencies a well designed servo is not in the audio path. A servo design does not do away with caps, but it lets you use high quality caps (for integrator time constant, and output filtering). Its worth mentioning that even servo circuits pass some DC....every servo circuit will have a DC component proportional to the servo circuit IC's offset (why it's important to choose a low offset IC for the servo app).
Servo circuits are not that uncommon in pro audio. I'm pretty sure Millenia uses them too...there's an option to direct couple the millenia mic pre's when you're using dynamic mics (i.e. turning phantom off bypasses the blocking caps). I've got a design for a servo based SSL type compressor...actually come to think of it, the Alan Smart compressor is servo coupled too.
Cheers.
Kris
Just to be clear, the 8200 is the eq.
"actually, I'm not a trained technician at all, I used to play piano in a brothel but business was bad, so..."
There's some vagueness on definitions here... when people say Direct-Coupled, they often refer to circuits with offset-cancelling servos on them... these servos also prevent DC from passing, so these circuits won't pass DC...
Anyone else here heard the (possibly apocryphal) tale of the front of house sound engineer -a few years ago- who lost one rail of the power supply on his Midas console (One power supply was already dead and now the spare had lost one rail...) minutes before the main act was due onstage...?
-Apparently he wired a 9V battery to an audio connector, plugged it into a spare Crown DC300 and adjusted the volume control to give 17Volts (or whatever)... then wired it across the dead supply to get the console running before the band took the stage...
Now THAT's Direct-coupling! -Try that with a DC-cancelling servo!
Keith
The old believe everything; the middle aged suspect everything, and the young know everything.
Hope I’m not giving the wrong impression here, I love the sound of transformer, and some cap-coupled gear. If I removed all the transformers from my studio I suspect I’d be left with a very sterile sound indeed, not to mention the possibility of ground-hum. But I do believe every studio needs as full-a-balance-as-possible between “light and shade”.
Fully DC-coupled units are a source of intrigue to me, why are there so few on the market? The 8200 constitutes the nearest thing I’ve ever used to a “wire with frequency-specific gain” (I believe it has a few small caps in the path, but they’re tiny mica ones that aren’t going to introduce much “smearing”/phase-shift).
Avalon is advertised as DC-coupled, but it uses input transformers, as does the John Hardy unit (I’m definitely interested in a Hardy when finances permit). Earthworks and Millennia make “transformerless” designs, I’m sure they’d state direct-coupled if they were. I suspect the discrete Sontec eqs are also fully DC-coupled as well, Massenburg had a hand in their design did he not?
Anyway, there’s not exactly a plethora of ALL-DC units out there, unless someone can name some I haven’t? I would’ve thought that DC pres/eqs are the bees-knees for classical recording? Maybe I’m barking up the wrong tree? Please tell me if you think that to be the case.
[img]graemlins/beerchug.gif[/img]
"actually, I'm not a trained technician at all, I used to play piano in a brothel but business was bad, so..."
1) Pain in the a** to design.Originally posted by thermionic:
Fully DC-coupled units are a source of intrigue to me, why are there so few on the market?
2) The sonic advantages are tiny in comparision to the cost.
3) The problems of external dc offsets...
I am sure the GML8200 sounds lovely but that is probably to do with a good design in general than the lack of DC-blocking capacitors.
Mats
Mats
"Great sound is no accident"
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