Tube preamp line-out into modern bluetooth system

Im curious to know, if I wanted to send the preamp of my fisher 500c (or other classic tube preamp) out to a modern Bluetooth system, what sort of buffer might be needed?

Although the preferences is the classic setup running from pre to power in the amp, there are times that it would be convenient to send the signal to satellite speakers. On the amp is a “record-out” set of jacks, but they do not appear to be buffered, and I am guessing there will be an impedance mismatch into a Sonos or other modern satellite system. Does anyone know if there is an easy off-the-shelf buffer to do this, or would it be best to build a cathode follower with a 12 ax7? My frame of reference is building tube guitar amps, so my guess is that the Soldano Effects loop would work. That being said, I am hoping there is an easier drop-in.


Not sure why it would need anything special - line out to line in, assuming there is one. Unclear what bluetooth has to do with it? Record out may not be adjustable, but neither is a CD player or other external source you would plug into the Sonos.

Thanks for the note. On the schematic, the record out is simply an in-line tap on the circuit. When circuits are labeled “line-out” usually they have a buffer built in the lower the impedance of the outgoing signal. My question, is does anyone have a recommended buffer to insert inline between the “record out” and whatever device it will then go into? CD players and other components have this as part of the internal circuit design.

I guess my question is, why would it require a buffer? What is the input you want to connect to? Typically a Record Out was simply a line-level output that follows the Source selection.

Typically, on tube powered pre amp devices, the output section has a cathodyne buffer stage for exactly the purpose of lowering the impedance before sending to a power amp. Although I don’t have any specific device to connect with, if one were to want the option of using some of the modern blue tooth devices for having satelite speakers, it would be good to know if anyone has a recommendation for an external buffer. Although it is speculative at this point, I was thinking perhaps Sonos, being that it is so popular at the moment.

OK - sounds like you’re still talking about guitar amps - which this is not. In this application, line output level tends to be a standard that doesn’t require any modification.

As far as using bluetooth to send audio to additional speakers, if they were to be in the same system (such as rear channels) I would be concerned about delay.

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it actually had nothing to do with guitar amps. if you take a look at mcintosh or ampex preamps you will see the final preamp triode is arranged as cathodyne. This is done for exactly this reason. Anyway, if you know of an in-line buffer, let me know. Thanks

OK, fair enough. Maybe someone else will chime in.

your feedback is appreciated nonetheless. feel free to drop me a pm anytime. username@gmail.