Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: Need some thoughts on setup with multi-subs. (Read 1885 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Need some thoughts on setup with multi-subs.

I am planning a stereo + multi-sub setup.

Here are the different scenarios.

1. Laptop headphone/line out -> t-amp -> speaker out -> speakers. headphone out -> line in on subwoofer
plate amp -> plate amp 2 -> plate amp 3.

2. Laptop -> usb -> hifimediy dac -> rest same as above. This one is more since the laptop out is a bit scratchy. But I could fix it with some rubbing alchohol.

3. Laptop headphone/line out -> line in on subwoofer plate amp 1 -> plate amp 2 -> plate amp 3 -> line out -> t-amp -> speakers.

I know the hifimediy puts out a full 2v rms on its line out. Not so sure about the laptop headphone out. I was told a headphone cum line out should have enough current to drive so many amps. Is that the only thing to be concerned about? What about impedance?

Back to the issue of gain structure. I have done some reading. However, I want to pick the best scenario in terms of maintaining the best S/N.

In case none of the above are ideal or even workable scenarios, I could get something like a fiio e09k. It has a fixed line out and a variable line out, that put out 2v and 0-6v rms respectively. Then it's a question of which line out to the stereo amp and which to the sub amp. I guess that depends on the input sensitivities of each.

Finally, on the input gain side. For the stereo amp, how high or how low is ideal? Most low to mid power class d/t amps that have their specs listed, have an adjustable gain in the range of 23-30 db gain. Is it desirable to have an even lower input gain in such a scenario?

Thanks.

Need some thoughts on setup with multi-subs.

Reply #1 –
Line out should be able to drive all of the sub amps.

A headphone amp will have even lower impedance, so it can also drive several amps.

The net power amp impedance should be higher than the preamp/DAC/headphone impedance.    Impedances in parallel divide, so 4 amps with 100k input impedance in parallel will be 24K (you can look up the formula if the impedances are unequal).    A typical DAC/preamp should have no problem with a 5K load.  Headphone amps usually have no trouble with 32 Ohm Headphones.

Quote
Back to the issue of gain structure. I have done some reading. However, I want to pick the best scenario in terms of maintaining the best S/N.

Typically you want a "hot" signal out of the DAC/soundcard.    The noise tends to be constant (or at least there is a constant component to the noise), so a stronger signal gives you a better signal-to-noise ratio.  But, it also depends on where your volume control is...

Quote
Finally, on the input gain side. For the stereo amp, how high or how low is ideal? Most low to mid power class d/t amps that have their specs listed, have an adjustable gain in the range of 23-30 db gain. Is it desirable to have an even lower input gain in such a scenario?
The important thing is that everything is balanced...  The sound-output of the subs has to match the main speakers.    You'd like enough gain so that you can get full-power, but not so much that you affect the noise part of the signal to noise ratio, at low volumes. 

Rather than a dB gain spec, the specs for most amps will usually tell you how much input voltage you need for full power, and it's typically around 1V, so that any line-level signal can give you full-power.

Need some thoughts on setup with multi-subs.

Reply #2 –
I love you DVDDoug. Ok, dont creep out. But I knew this forum would come through! That clears my doubts on using a single headphone/line out and daisy chain all the amps. I'll get a little t-amp with a headphone out just in case. I'll try out both scenarios. Going from all the plate amps to the stereo amp. And vice versa. The plate amps specify 'line level loop through' so no filtering. It's just that it strikes me as unintuitive going from sub amp to stereo amp rather than the other way around. Ofcourse, we are only talking about one impedance load being switched around in the chain, aren't we? Ie, the stereo amp.

I guess I'll run the dac signal full level(2.2v rms) and control volume at the t-amp. Yes, I'd need to set sub gain levels relative to mains. In fact the multi-sub method I am considering(geddes) calls for individual gain adjustment. I will do a bit more reading up on gain structure. Is higher input sensitivity in terms of volts is better in this case? I know there's no general answer..