Bi-Amp w/ Tube Amp & SS

[RoadRunner]

The power side of my system consists of an electronic crossover, feeding two solid state amps, to two way speakers.

I am considering replacing one of my solid state power amps with a tube power amp.  My electronic crossover  is set at 800Hz. 

My first thought  is to  run the HF driver via a tube amp and the  LD driver via the solid state amp.

Any advise as to which type of amp is best matched to LF signal or HF signal and why it's characteristics would lend to its being best placed in that role?

At this point, I am not considering specific models, but overall general characteristic differences that would help in the  planning stage.

[opnly bafld]

This should help.
Altec Lansing 18"  horn/807-8A HF Driver  
Altec Lansing 15" 411-8A LF Driver

HF driver specs
http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/drivers/807-8A%20HF%20Driver.pdf

LF driver specs
http://www.greatplainsaudio.com/vintage_altec/411-8A_lfspkr_spec_sheet.pdf

[richidoo]

RR, Tube amps don't have as low of an output impedance as SS amps, so they cannot deliver current as fast and easy as transistors. The transformers they use to bring their real output impedance of several thousand ohms down to 2 ohms add their own distortion which is pleasant but warmer than a direct coupled transistor. So the transient response in the bass frequencies where more power is needed suffers with tube amps. Large transformers would help, but that is by far the most expensive part on a tube amp and so that's where the biggest compromises are made on commercial designs. Good transient response is required for punchy detailed bass. So SS is usually best for the bass, because transistors have very low impedance without any transformer. But of course, "tubes rule," and sound very nice in the mid and upper freqs. Part of that is the sweet sounding distortion of the transformer, and part of it is the lower amount of feedback required with tube amps than SS to achieve acceptable distortion. Tubes are usually warmer and less grungy in the treble than SS amp of similar price, but not always. It takes a very talented SS designer to make a low price SS amp sound as sweet and open as a tube amp at the same price. It is easier to make tube amp sound great in mid and treble without much fuss.

The problem you will face is the tonal difference of the two amps, especially crossing at such a low freq in the heart of the midrange where your ear is most sensitive, and especially with a horn tweeter which will show off the slightest tonal variation. When I have tried tubes on mid/tweet and SS on bass it has not worked well. The tonal difference is too great, the crossings were in midrange on Kaya panels, Piega ribbons, and Usher cones, and at 250Hz on Legacy which worked a little better. For me the tube always sounds too warm and distorted and sometimes weak compared to the ballsy but dry SS amp.

Of course a warm SS amp like Pass or Mac and a super clean tube amp like AtmaSphere might work OK. The horn will magnify the tube warmth especially so low, so you have to be careful. Definitely try before you buy.

What amps do you have and what are you thinking about for tubes?

[RoadRunner]

SS amps are Sony TA3130Fs vintage 1971.

With the electronic crossovers, I could select a crossover point anywhere from 500Hz to 1000Hz.

I will depend on  forum advice to assist in  looking at potential tube amps,  The horns are very high effeciency, so  I will not need gobs of power for them. 

[richidoo]

Try to borrow any old tube amp that is healthy and well groomed. If it has transformer output it will let you see what normal tube amp will sound like, close enough to get a feel for it. twhs

You can buy a new tube amp for $1000 from primaluna, but it will be very warm, with very cost conscious transformers, otherwise a nice little amp. Nightshade seems to be making clear sounding tube amps with quality transformers and high value price, but I've not heard one myself. Bunky has one and likes it, that's a big compliment considering all the tube amps he's been through. A transcendent SEOTL might be interesting for your project. There are lots of choices. Be sure that you don't get too much gain on a tube amp, they make funny noises and the horn will magnify all of it. These I mentioned claim to be quiet. You don't need more than a couple watts of power. Do you have a picture of the speakers? Sounds so cool!

[rollo]

  Since your speakers are highly efficient why even consider bi-amping ? Bi - amping is best when the the same amps are being used. Keep it simple. Try a single amp with NO crossover both SS and tubed and then report back your findings.
  IMO I believe you will be very surprised as to the outcome. KISS.


charles

[BobM]

I agree. Using amps of 2 different types will likely result in a discontinuity from top to bottom, unless one of them is driving things from perhaps 100-200Hz and up and the other is kust powering the midbass and bass region. In any case you definitely need an active crossover of some type to get anywhere near a balance between the two.

I did try this myself and couldn't make it work in my system. Using one amp to drive it all was far better. Unless you are using the same amp for top and bottom, but then what's the point I guess..

[AcidJazz]

I biamp with a tube amp on my speaker's mid-panel and tweeter (passive hi-pass network for the tweeter in place), and a big SS amp on the bass drivers with great results. Way better results than with the stock speaker and its passive crossover network being driven by a single amp.
So I don't agree with the statements above.
If you are going to crossover way up into the midrange, a gentler slope might be advisable. I crossover @ 320Hz/ 24dB, with a slight attenuation at the crossover point.