Amplifier input impedance - can it be too high? Plus another question

I’m in the market for an upgrade to my current Gen 1 Wyred4sound ST-500 amplifier. I exclusively stream files NAS - laptop -Exogal DAC- BHK Pre - Wyred - Ohm 5000. I use Jriver on the laptop for library control.

I prefer a stereo amp due to space constraints. Need high power for the Ohms. Desire high efficiency (class D). Hoping for improvement that will be more than subtle.

I’ve been looking at amplifiers with input impedance rated at 3.3k (that was an outlier) up to 160k. Looks like the PS Audio BHK 250 is in the 100k area. Should I be looking for a “match” with the BHK pre or can I assume anything over 100k will work?

The new PS 1200 amp would interest me if there was a stereo version. I could use the 1200 or the M700 if I stacked them. Which prompts my second question. The BHK pre already has a tube input. Is there any benefit to a tube input on the amplifier if there’s already one in the pre? I’d like to minimize the number of degradable components in the system to the extent possible. The wyred has been rock solid and utterly dependable - I’d like that same dependability in my next amp.

Thanks in advance for your response. I read the forums frequently and I’m confident I’ll receive informative feedback.

I have a BHK preamp and M700’s in my other system. They perform really well. I did not stack the M700’s but they would stack up to roughly the same height as the BHK preamp. The Ohm speakers are a really interesting technology to me. The BHK 250 would also go well with the BHK preamp.

Thanks, Baldy. I have no doubt the PS Audio amplifiers would perform well with the BHK pre. Unfortunately none of them are hitting all my preferences for stereo, class D, high power, and latest technology. Each of the PS Audio amps is lacking something I really want. I’m most likely going to buy another brand of stereo amplifier, which prompts my question as to impedance matching (is higher better or is there an optimal range to match the pre?)

If I eventually give in and buy monos, my second question comes into play. Is there any benefit to tube input sections in multiple components of the audio chain? Because if I’m going mono I’ll be looking hard at the m700 and m1200.

I cant help on the impedance question. Just compatibility.

Generally recommended that Power Amp Input Impedance be at least 20 times higher than the Preamp Output Impedance (higher the better). BHK Preamp Output Impedance is <100Ω Balanced & Unbalanced.

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I think you’ve confused the BHK pre input and output impedance values. Output impedance should be lower. BHK pre specs say less than 100 ohms.

I’ve no doubt the PS Audio power amplifiers will match well with my pre. I just wondered if there was an upper limit on amplifier input impedance where higher is actually detrimental.

I use balanced connections between my DAC, Pre, and amplifier so the balanced values would apply.

By the way, just noticed I left my DAC out of the original post. I’ve corrected that.

Yes, corrected. No, the higher the better. I use an Audio Research LS28 preamp (600Ω output impedance) to BHK300 monoblocks (100KΩ input impedance) balanced; 167 times higher. A very nice match.


In my experience, low output impedance is good for sound quality.
The DS DAC has over 100 ohms, that’s why I assembled the buffer with the OPA1632 amplifier. This buffer has significantly improved the sound of my system, in which the SD DAC directly controls the active 3-way loudspeakers.
I do not include systems with current control, such as CAST and SATRI.