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Using Mono Tube Amp to Drive Two Speakers?

AlexHempel

AlexHempel

AK Subscriber
Subscriber
Hi AKers,

I assume my dilemma is a common one -- you find a super cool monoblock, but it's expensive and you know you're probably not going to find another orphan for years, if at all. My listening space is set up for stereo, so just using one speaker isn't really an option. I'm curious how many of you have used a mono amp to drive two speakers. Obviously the sound will be mono, but I can live with that. In my case, the speakers would have to be wired in series, because the amp doesn't have a four ohm tap. Are there any issues that typically crop up? Is the sound quality acceptable? Is this a brilliant idea or a terrible one? Any thoughts appreciated, I am trying to find any way possible to justify purchasing an amp that popped up near me.
 
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Never tried it --- only thing comes to mind is that series connection with raised impedence should reduce power output.

What is the super-cool monoblock ?
 
Run in series, which doubles the impedance but drops the actual load on the amp. Back in the early 80's, when on road trips for work, I ran a Pilot AA-902 little 6v6 monoblock feeding 2 rat shack minimus 7's, source was a Sony am/fm/sw portable. Modifications to amp by me were a switched power socket for the radio's wall wart, power switch, converted speaker connections from screws to spring-terminal push-ins, solid-state rectifier for the 5y3, & a protective shield to physically protect the phase inverter & AF amp tube, since they're close to the end of chassis & easily knocked out/around. Output is tapped for 4,8,16 ohms. Still have it, would love to stumble upon another.
 
@kappclark An IPC 1026, very good condition, best I have ever seen. It's on the auction site and priced at about 1/3 (or less) of what I've seen pairs sell for in the US. But orphans are pretty rare, so I'd be running mono for quite a while.
 
AlexHempel said:
... Any thoughts appreciated, I am trying to find any way possible to justify purchasing an amp that popped up near me.
Click to expand...

Yes, I have a thought.

As long as there is food on the table, the kids have shoes, and the other bills are paid, the only justifications necessary are that you want to and can. ;)
 
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pentode amps actually tend to fare better with a lower impedance load. Running too high makes life on the screens rough. Better answer would be to figure out what load the thing was designed for initially and see if series or parallel more closely matches that.
 
I've done it running them in parallel connected to a lower tap (ie two 16-ohm speakers in parallel on the 8-ohm tap).
 
Well, in the end I decided to fix my Capehart N2 instead of going for the IPC, but the Capehart is also mono so... exact same dilemma. And it has a bit less power (18 w) so I'll be interested to see how it handles two speakers. There are a few pairs available on Ebay, and if I really love the sound, I might buy another pair and keep the third for parts.
 
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