Tube vs Solid State

Lalitk
I am running pair of KWA150SE's in bridge mode (450Wx1) for the mighty B&W 800D2's

I had a look at the amp specs online.

so just my opinion

walk up a hill at an easy pace.
then run up that hill 4 times as fast.

Walking up that hill is like your amp in stereo
Running 4 times as fast up that hill is like bridge/mono mode.

imo - Your stressing the amps. All B&W 800 series have always been far too revealing of upstream components. So agree with Georgelofi to just run them in stereo mode. But I assume you have done that already?
You should also be running in high bias mode for those speakers. Again I assume you are doing this.
   
I noted that the amps are also not able to double down. 8 ohms going to 4 ohms and no figure shown for 2 ohms at all.

Power Ratings:
• 150W @ 8 ohms (Stereo) @ .06% THD.
• 450W @ 8 ohms (Bridged Mono) @ .06% THD.
• 200W @ 4 ohms (Stereo) @ .06% THD.
• 650W @ 8 ohms (Bridged Mono) @ .06% THD.

And from the amp manual

It is not recommended to run the amplifier in bridged mono into 2ohm loads.

This amp would not have made my final checklist for the 800d2 speakers.

http://www.modwright.com/products/kwa-150-signature-edition.php


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68pete
Hello ct0517
What 800,s do you have?

Hi Pete

my systems are shown here just click on the runner. 

In my Room A - Matrix 800 + Krell Bass Alignment Filter 

Cheers.

Not only are your speakers vicious (and tube-unfriendly) loads, as George points out above, but in the bridged mode you are using your amps will "see" speaker impedances equal to half of the already very low values he cited.  Which can't be good for the sonics of the amps, even though I note that you indicated in this 2015 thread that Dan Wright had "optimized these amps for bridged mode," whatever that may mean.  

Also, as others have alluded to there are a great many ways in which using solid state and tube amps in a biamp configuration can do more sonic harm than good.  And even more so when the speaker is inherently not tube friendly in terms of either its impedance characteristics or its power requirements.

My suggestion is that you consider trying your existing amps in a passive vertical biamp configuration, with each amp operating in stereo mode rather than bridged mode.   Your speakers have low impedances in much of the bass region, and the 250 watt/4 ohm rating of your amp in stereo mode could very conceivably be adequate, especially given that each channel of the amp would only be supplying current and power in part of the frequency range when used in that configuration.

The one caveat that occurs to me related to that configuration is that I'm not sure about impedance compatibility with your line stage.  In that configuration the line stage's output for each channel would be driving the inputs of two amplifier channels, and would therefore see a load impedance equal to half of the input impedance of each amp channel.  The input impedance of the amp is spec'd at "15K at 50Hz; 23K at 1Khz."  The LS36.5 has a specified output impedance of 110 ohms, which would seem compatible with a load impedance of 15/2 = 7.5K, but as with many tube preamps the 110 ohm figure might be considerably higher at deep bass frequencies.  That would be a question for Dan.

Also, assuming you are using balanced interconnections between the line stage and the amps you would need an XLR splitter, such as these.

In your older thread that I referenced earlier, BTW, I had advocated against a vertical biamp solution, but that was under completely different circumstances prior to your purchase of the Modwright amps.

Good luck.  Regards,
-- Al
 

This thread has been done many times!!

If you can't hear the difference, what's the difference?

"My suggestion is that you consider trying your existing amps in a passive vertical biamp configuration...."

Al, thank you for your feedback. I have already tried this, while I gain bit of better separation in mid’s and high’s, the bottom falls out a bit. The low bass frequencies are not a weighty as they are when I run the amp in bridge mode.

Secondly, the LS36.5 is configured with dual balanced outputs in parallel to accommodate bi-amping or a sub with balanced inputs.

@ct0517, I have tried all the options you suggested.

My room is fairly treated and power issues has been addressed with a pair of Audience aR6-TSSOX for digital and analog components.

It seems from rest of the feedback that KWA150SE may not be the ideal choice for 800’s. I am looking into a pair of Class D 1000W / 8 ohm amps to handle low bass frequencies. Add a electronic analog crossover to split bass and mid/high frequencies between class D and tube amps.

I hear Pass Labs SVR1 and Marchand tube or SS are among the best crossovers out there.

Thank you all for your feedback.