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Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: aoresteen on August 18, 2024, 10:30:06 PM

Title: Adding a balanced XLR OUTPUT to a SS Amp
Post by: aoresteen on August 18, 2024, 10:30:06 PM
My Fender Frontman 25R project continues.  I need to add a microphone level XLR balanced output to feed it to to the PA mixer board in it's own channel.  My Carvin SS bass amp has such an output that I use all the time.

The signal level from the pre-amp to the power amp I assume is line-level which is too hot to use.  I could use a DI box but I would prefer to just have an XLR socket on the back of the amp and avoid using a microphone. Use would be primarily for live gigs.

Ideas?

TIA!
Title: Re: Adding a balanced XLR OUTPUT to a SS Amp
Post by: Loudthud on August 18, 2024, 10:50:07 PM
A typical circuit will include a low pass filter to simulate the response of a guitar speaker. If you search here, you can find several.
Title: Re: Adding a balanced XLR OUTPUT to a SS Amp
Post by: J M Fahey on August 19, 2024, 02:42:58 PM
Yes.
For the full experience, take speaker out signal, which will be about 10V RMS (WAY too high) and attenuate it 100:1 to 100mV using a 2 resistor voltage divider: 100k in series, and 1k to ground, which is perfect to feed it into a mixer Line input (every channel has one), no need to super attenuate it to microphone level (a few mV), nobody does that.

Insert a direct box circuit in the path as suggested earlier.
For example: Hughes and Kettner famous Red Box

Schematic and suggested PCB is widely available.
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