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October 06, 2022, 09:03:47 PM

Author Topic: Moreplay Into SS (or low input impedance) amp?  (Read 245 times)

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Offline greg788

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Moreplay Into SS (or low input impedance) amp?
« on: June 24, 2022, 02:52:23 AM »
Is anyone using the Moreplay into an amp with a lowish input impedance? My amp is SS and has a 22Kohm input impedance. Interconnects will be short (3') but this is only a 10X impedance delta versus the Moreplay's output impedance. What are your thoughts or experiences here?

Offline Doc B.

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #1 on: June 24, 2022, 05:47:35 AM »
Sorry, I thought I answered this last night on my way out of the office. Must not have hit the post button. The 22K load will not be a problem. 10x is way plenty. IME 5x is usually just fine. I'm not sure why this greater than 10x thing has become dogma.
Dan "Doc B." Schmalle
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Offline Paul Joppa

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #2 on: June 24, 2022, 12:53:38 PM »
Re: Doc B. said "...I'm not sure why this greater than 10x thing has become dogma."

Just wanted to add that for power amps, the load that the output tube sees is usually between 2 and 5 times the source impedance (plate resistance). And those tubes are run at nearly the full available output, which is a worst-case condition for distortion.
Paul Joppa

Offline greg788

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #3 on: June 25, 2022, 06:11:07 AM »
Paul, can you elaborate on what you said in relation to the impedance delta with the preamp? Not tracking this

Offline Paul Birkeland

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #4 on: June 25, 2022, 06:41:10 AM »
PJ is describing the operating conditions for triodes in single ended triode amps, where the output transformer will reflect a load impedance that's only a few times higher than the plate impedance of the tube itself, and that the output tube is required to swing enormous amounts of voltage to get meaningful output.

In a preamp like the BeePre or the Moreplay, the amount of swing is maybe 5% of what you'd expect in an amp, and the load impedance is a fair bit higher and more constant than what you'd get with a transformer connected to a loudspeaker, so the conditions are far less demanding and unpredictable.
Paul "PB" Birkeland

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Offline greg788

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #5 on: July 02, 2022, 07:07:09 AM »
Is there a lowest ratio assuming short interconnects, like 5:1, or is impedance ratio an old wives tale in totality? I'm considering an amp whose input impedance is only 3.6 kohms

Offline Paul Birkeland

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #6 on: July 02, 2022, 07:11:47 AM »
I would suggest that an amp with a 3.6K input impedance is a rather questionable design from that spec alone.   Short interconnects minimize cable capacitance.
Paul "PB" Birkeland

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Offline greg788

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #7 on: July 03, 2022, 03:32:45 AM »
It's the Pascal class D module. The question is, would this present a problem?

Offline Paul Joppa

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Re: Moreplay Into SS (or low input impedance) amp?
« Reply #8 on: July 03, 2022, 04:32:07 AM »
In my opinion, Moreplay will not drive less that 10K ohms acceptably. The gain will be reduced and distortion increased.

It won't hurt anything to try it; music will come out, but it won't (again, my opinion) sound as good r work as well.
Paul Joppa