Impedance Question

[Puguglybonehead]

I tried searching to see if this question had come up before but couldn't find what I was looking for. I'm intending to put together a battery powered busking amp, using a prebuilt class-D stereo board.

https://www.parts-express.com/Sure-AA-AK32151-2x15W-Class-D-Stereo-Power-Amp-Kit-TPA3122-320-322?turntoflow=qco&ttdat=eyJjIjoxMzc3MCwidSI6MjYyMTQyMTAsImYiOiJQYXRyaWNrIiwibCI6IlRheWxvciIsIm0iOmZhbHNlfQ&tttok=eyJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJUdXJuVG8iLCJleHAiOjE2NTkwNjk1ODUsInUiOjI2MjE0MjEwLCJzIjoiVVNFUl9DT05GSVJNRUQifQ.WWDIEXZIlO6wTDFISbWkHg6d3VFPSHzlTzAi2Uy3gBg&turntosku=320-322

I was going to put vocals through a mic preamp into one channel and in the other channel for the guitar, I was thinking of using a Blues Breaker kit as a preamp. I really like the tone of the Blues Breaker as an always-on pedal. Sounds more convincing than most of the tubes-to-FETs pedals to my ears. The class-D amp needs to see a low impedance in. Not knowing much about calculating the impedance of pedals, do I need to add a buffer between the Blues Breaker and the amp board input or will the signal already be at a low enough impedance?

[idy]

You will need some kind of isolation, whether passive resistors or buffers: The Bluesbreaker, like so many pedals, has a volume pot right at the output (well, there is a pull-down R and an output cap after.) So if you just stick the output of your mic pre amp and "Y" it with the BB you will reduce or kill the volume on both when you turn the BB down.

It is not a matter ( I think) of giving the BB some stiff impedance, but rather of interaction with that volume pot. At minimum the other channel will see 0ohms impedance.

But passive resistor mixing could be enough.

[Clint Eastwood]

The original bluesbreaker pedal has a tone and volume control at the output, and so although I cannot tell you the exact output impedance, I don't expect it to be very low. So it is probably a good idea to use a buffer. Your class D amp by the way has an input impedance that varies with its gain setting, between 10 and 60 kohms.

[PRR]

> preamp into one channel and in the other channel for the guitar

"Channel" means different things in Stereo and in Stage amps.

That Sure AA needs TWO loudspeakers. Are you planning for that? (Seems awkward for a busk-amp.)

What you maybe want is a MONO amp and a 2-input mixer.

[iainpunk]

What you maybe want is a MONO amp and a 2-input mixer.

or use this amp in bridge mode for more power (using higher impedance speakers) and use that mixer.

cheers

[Puguglybonehead]

> preamp into one channel and in the other channel for the guitar

"Channel" means different things in Stereo and in Stage amps.

That Sure AA needs TWO loudspeakers. Are you planning for that? (Seems awkward for a busk-amp.)

What you maybe want is a MONO amp and a 2-input mixer.

I am thinking of using one speaker for each channel so that the guitar doesn't walk all over the vocals. (or vice versa) I've got an 8 inch 4 ohm  for the guitar. Not sure what would be best for vocals. Of course, a more powerful bridged mono amp is an idea.