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Adding a pre out (subwoofer) to T1 ALPS?

Hi there

Total beginner here!

I'm busy putting together my awesome little T1 and the SMPS300R, and was thinking of including a pre-out section from the volume control as stereo RCA jacks on the back panel to drive my subwoofer.

Attached is a picture of what I have in mind.

Anyone have any idea how best to do this? I don't need to mix the signal to mono (my sub accepts stereo input), but from what I vaguely understand I need a "unity gain" buffer to keep the pre out signal clean from interfering with the subwoofer. Or am I overthinking this?

Any experience or advice regarding adding pre-outs to the T1 would be welcome!


Hi, yes that will work. 

Do you have a preamp already?

Hi Hifime - thanks for the reply!

Sorry, by "preamp" I just meant the preamp section of the T1 - the volume controller (ALPS pot). So in the attached image, there are two scenarios:

A) I just run some wires from the ALPS pot, connected to some RCA female jacks. These can then connect to my subwoofer.

B) In this case, a Unity Gain buffer is added between the ALPS pot and the RCA jacks.

So my questions are:

1. Is the Unity Gain buffer needed (scenario B)?

2. Where on the ALPS pot would I attach the wires needed to connect the RCA jacks?

Sorry, total newbie here - I'm essentially looking for some step-by-step instructions for how I'd add a pre-out to my T1 :)


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yes it will work like that without a buffer. You should keep the cables as short as possible to reduce noise.

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Hi Hifime

It's been a while, but I finally tapped the ALPS volume pot center pins, and wired them to a little through-hole terminal block. From there, I can connect two wires from the Left and Right outputs from the pot to some RCA jacks, and connect my subwoofer.

However, even without the subwoofer the amplifier is now extremely noisy - a hissing that reminds me of a grounding problem. The hissing/noise gets even worse and louder when the subwoofer is connected.

Any tips for removing the noise that tapping the ALPS pot for a pre-out has caused?


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