Cap Coupled vs Direct Coupled
- Thread starter RoSu_30
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read this thread post 2 tells how to tell the difference
https://audiokarma.org/forums/index.php?threads/cap-coupled-receivers.646419/
https://audiokarma.org/forums/index.php?threads/cap-coupled-receivers.646419/
RoSu_30
Active Member
RoSu_30
Active Member
Lavane
Lunatic Member
That link to the post about how to tell the difference is mostly correct. There is some equipment that may take a closer look to be able to tell the difference.
Realistic is one of those brands. Some of the receivers and integrated amps can look like they are cap coupled at a glance. You will see three large caps, but the amp or receiver is acually direct coupled. The SA-1000 and 1000A integrated is one example. Pop the top, and you see three big caps. Its a DC amp, but the circuit design is a bit different. No DC offset or bias adjustment pots, just a single voltage adjustment for each channel. When I went to recap an old SA-1000A, I thought at first it was cap coupled. After looking at the schematic it was clear it was direct coupled.
twiiii
Lunatic Member
which ever has the lowest distortion, least phase shift, at least an acceptable damping factor, the least ringing, over shoot, and best signal to noise. It should sound great, too. Its should also be perfect for my speakers. No one else's just mine. Thats why I bought two MC-830s last month instead of a MC 462.
Lavane
Lunatic Member
I have a cap coupled integrated amp I really like. Some feel they have a warmer tone to them. At higher volumes the coupling caps can struggle to keep up and the bass can become loose and flabby. The one I own has had the power supply upgraded to accommodate larger value coupling caps and main filter cap. This helps to keep the amp from running out of steam at higher volumes. I've seen some just replace the filter and coupling caps with higher values, but the power supply needs to be looked at to be sure there isn't any undo stress put on it.
peguinpower
Well-Known Member
I really want to hear a transformer coupled preamp 
Lavane
Lunatic Member
The difference may be like some of the Sony amps. They have a switch on the back. If I remember right, when switched to DC, this bypasses the small caps at the input of the amp board. In the one manual I read, its to be used for testing only. Those caps are usually a small value like 1uf.
I really want to hear a transformer coupled preamp
Why? On so many levels, why? It wouldn't be hard to experiment with. I'm sure Jensen or somebody makes some little trannies that would do the job. You just don't see it done for the cost, the expense, the distortion, and complete lack of necessity. You usually use transformers where you need impedance conversation in an output, but power amp inputs have tens of thousands or hundreds of thousands of ohms. Even tube pre-amps don't really need an output transformer to drive a 50,000 ohm amp input.
peguinpower
Well-Known Member
It's not a cheap implementation, but for what it's worth, I have heard that transformer-based volume control in a pre-amp is probably the best sounding kind. I am pining for the soon to be replaced transformer coupled BAT VK-33SE preamp to hit the used market, when the new one comes along.
I dunno.... I think it's pretty hard to beat a stepped attenuator with good matched resistors.
peguinpower
Well-Known Member
I want to hear one. I am fascinated by it, as much as I am fascinated by the sound of different amplifier topologies.
edwyun
Super Member
There are sevaral preamps with transformer coupled inputs and/or transformer coupled outputs. Most modern preamps from Jeff Rowland, Zesto, Allnic, BAT, etc., for example. At least on the Rowland, there is immunity to background noise/RFI/ground hum on inputs/outputs, and with lower output impedance across the frequency range, better bass response.
Last edited:
Steven Tate
CEO Flat Forehead Soc.
If I understand correctly, one of the main benefits of a well thought out output coupling strategy is the protection of the speakers from bouts of unwanted and potentially damaging DC. Big caps and transformers make a direct barrier to the DC. In a direct coupled design, you really need a speaker protection circuit that will shut things down if DC rises above a certain threshold. Probably an oversimplification, but that's about the limit of my understanding of output coupling.
something I always found curious about early transistor gear is that it had a lot in common with early tube gear. Tubes got away from transformer coupling by the mid 30s, but fast forward 30 years and it was back again. And then abandoned for the same reason the tube designers dumped it decades earlier.
peguinpower
Well-Known Member
And what was the reason? Can you share?
I am fascinated by different equipment designs and I have marveled at the way BAT makes preamps. I own one and the stepped resistor volume control and super pak capacitor bank sounds real nice. The bring out a lot from the amp I put on them.
Upscale can get salesy, but this is a good look at a transformer coupled VK-33SE. I want one.
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