How to use a subwoofer with a 2-channel amp

I have a 2-channel tube amplifier. It does not have a subwoofer out. There's a sub I want that has both line-level and speaker-level inputs. Can I split the speaker outputs on the amplifier, so that both the speakers and the subwoofer are hooked up at the same time to the same speaker terminals? Or is that going to degrade sound quality or somehow hurt my amplifier?


It should be fine, just check that the output transformers are fully floating, i.e. one side is not grounded. Else when you common one side to ground at the sub and you get the wrong one you will have melted wires and hot transformers.

The only thing I would say coming from experience of this kind of setup before, is that the quality of bass you will get will experience from the sub will be a very poor representation of what is possible, because the early bass roll off of the output transformers and poor speaker damping spoils the LF signal.
A buffer is an op-amp set up with unity gain to amplify the current of a signal, while the voltage stays the same.

This is to get the output signal from your preamp without loading it down. The buffer takes a small bit of current + voltage from your preamps output, and makes an exact replica of the signal, but with higher current and better drive - to send a good strong signal to your subwoofer amp.
OK, done. I was going to just P2P on a small proto board but my OCD got the best of me. I tested it on my system and bass is clean and plentiful.

OPA2134 buffer
Input impedance: 100k
Output impedance: 100R
DC offset Out_1: 1mv
DC offset Out_2: -1mv

Well, it's nothing fancy, but here you go....

The buffer arrived the other day, and I just wanted to say thank you thank you thank you! This is a really nice small design... but I have a question. I really don't want to fry this thing, and although I've downloaded the datasheet for the chip, I'm still not 100% sure what to connect to where. I'd really appreciate it if you could tell me what the pinout of the 3-port and 5-port connectors are. Thanks!

Sorry man, I can't read that diagram. I can follow simple instructions and solder pretty decent. I can replace components or make minor modifications. I can even build an amp from a kit. But reading and understanding schematics is beyond me, much less converting schematics into an actual device.

I haven't even looked inside the amp yet, and I don't really even know what voltages are availible... or how to get the required negative voltage.

…I haven't even looked inside the amp yet, and I don't really even know what voltages are availible... or how to get the required negative voltage…

:bigeyes: Ok, You really need help and a lot of hands on, I suggest you find someone you know in person that can read and interpret simple cut and paste schematics like the one I posted. Updated picture: 1(1)




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