Biamping Question

I have a solid state amp rated at 225 watts per channel. I'm told it actually tests a bit higher than that, perhaps closer to 300 watts. I just acquired a 100 watt tube amp. I had intended on running these separately with various components I have, but I'm wondering if it is worth trying to biamp with the solid state amp at the bottom and the tube amp at the top.

Can anyone offer advice or suggestions. The amps are a TRL D-225 solid state and a Music Reference RM-9 tube. Thanks
It is not uncommon for people to biamp with tubes and solid state, attempting to combine the advantages of both.

If you passively biamp, it is very important that the amps have the same gain. If the amps don't have the same gain, it would require a mod to one of the amps, which should be able to be done by any competent technician.

If you actively biamp, using an external, electronic crossover to bypass the speaker crossover, not only do you have to make sure that the gain matches, but you have to bypass the speaker crossover. This will require surgery to your speakers unless have something like Linn speakers, where you bypass the crossover by connecting to different speaker posts. Even if you did do such surgery on the speakers, it is possible that it could sound horrible. Speaker designers will match the crossover to the drivers and cabinet that they are using. If you bypass their crossover, who knows what will happen since the designer did not intend such a use when designing the rest of the speaker!

From your post, however, I am assuming that you are simply talking about passive biamplification, so it's just the amp gain that you have to watch.

Using Linn equipment, which is designed to biamped, I found passive biamping to make a small, but noticeable improvement. Active biamping, on the other hand, is a huge upgrade.
A lot depends on your speakers. If they are fairly efficient, over 90db, then 100 watts is more than enough.
Try the biamping vs either amp alone. You may find that biamping is more difficult with lessor results. I've always had problems keeping the gain equal between amps (ie the tube amp may be louder at low volumes but as volume increases the solid state amp may gain more quickly and overpower the tubes?).
Try it!
Try passive biamping!

If your amps have input volume control, thats it...
If not you can get a passive volume attenuator(Axiom, Creek, Placette) and connect it to the bass amp in order to match gain.
I have used (ahh tabu!) an Equalizer with my VOTs for bass in order to increase gain on the Bass amp with great results!! (I even added a little lower octave bass BTW)

Just connect them to your speakers original Xover.
The main point of biamping is to give less work to the amps so they can respond better, dont try to redesign your speakers....

I Recommend biamping mainly for complicated music, I have found that its very hard to get a full symphonic Orchestra with just one amp.... I dont know if anyody esle feel the same way?

What speakers do you have?
Thanks for the responses everyone. I much prefer the passive biamping approach based on the information so far.


I am using Spendor 1/2e speakers. Sensitivity is 88db and nominal impdedance is 8 ohms. The tube amp has adjustable gain: 27db (1.2V input sensitivity, 0.7db damping, 19db feedback), 32db (0.8V input sensitivity, 1.5db damping, 14db feedback), and 36db (0.4V input sensitivity, 2.5db damping, 10db feedback). The solid state is I believe somewhere in the 30 - 37db range for gain, 0.8V input sensitivity, and zero negative feedback.

I have tried the tube amp alone and even with a passive preamp (K&K TVC) the high and medium gain settings don't let me get too far up the volume control (9 - 10 o'clock) before the sound is too loud. The low gain is most flexible, but also has the most feedback which I would prefer to keep at a minimum. The designer prefers the medium gain setting. The solid state lets me get a couple more clicks in, to around 11 - 12 o'clock.

I do have a pair of EVS Nude attenuators lying around I can also employ if this would help me balance the gain in the amps. How would I go about employing the attenuators and how could I tell if I achieved the right balance. I'm considering sending my TRL D-225 back so I can have an input volume control added to it, but that would only be as a last resort.

Hello Clio09,

I guess the simplest thing (if you havent tried it yet) would be to put the tube amp on the medium gain setting which is the same gain as your SS amp and just connect them to your preamp output with a Y connector, speaker cable of the tubes to the highs and SS to the lows...
How does it sound?

If they dont match...too many highs for instance try lowering the input sensitivity on the tube amp again to 0.4V setting....and viceversa.
If you need some fine tunning then use the attenuators, hereĀ“s a couple of links that can help with the instalation of these.

Once you have a good setting with the attenuators you can put good quality resitors of the same value you settled on and just enjoy..... Audiophile accepted solution if you use Caddock or Vishay!

I am worried about biamping though since the Xover point of your speakers is pretty high, 3 Khz its like your speakers have 2 tweeters (they should be very resolving on mids), usually it is best to biamp at lower frequencies, say 100hz to 800hz, but do give it a try!!!

If you get away with it your system will have beautifull ease and power...


Thanks for the information and links. Yes the Spendors are well known for the midrange. The EVS attenuators use a 10K nude Vishay. I also have a pair of Endler attenuators that use a 4k Yageo resistor. I can hook these up to the inputs of the of the tube amp to attenuate any excess gain. It should at least give me an idea if biamping will work.
both amps need to have the same sensitivity for output or one section of the speaker will play louder that the other .usually when people biamp it is with the same amp