Bi-amping old M.L (quest) whith not so good results.

Hi guys.

I am the happy owner of a pair of M.L. Quest’s ( the old model ) which I have been driving with a 6L6GC class A PP tube amp ( 20W triode coupled ) for some time and are quite happy with the result.
Source is a computer and a firewire 410 soundcard from M-audio

But, as usual one want’s to change the setup all the time ;-) so I bought a Single ended amp ( EL509-II) and a Accuphase P-300 for bi-amping.

The result was, to my surprise, quite disappointing. I changed the SE amp out with the old tube amp and this was better, but not as god as when I drive the Quest’s with only the tube amp.
Driven with the P-300 they also sound’s good, but when I Bi-amp the sound get’s less uniform compared with the mono-amp setup.

Does any of you have experience with Bi-amping a set of the old Logan’s whit good result ?

Hope to get some good inputs before the SE and Accuphase hit’s the road.

Thank’s

Reenberg

I'm not quite sure exactly what you're describing, but I have a guess as to what I think would be the most likely fault: If the amps do not have the same gain (usually around 26 dB but can vary a lot) then you'll get very unbalanced sound. Other than that, it could be a wiring issue or even a phasing issue between the amps. How did you split the preamps output? This might seem insulting, but did you remove the jumpers between the speaker posts? Maybe swap polarity on one amp and see if that's it.

A surprising amount of voice comes out of the bass units. Thus there are many many factors that effect sound, including amp gain, speaker cables.

I too tried a different amp on the bass (one with adjustable gain actually), and prefer the sound of my one main 125w/ch cj sa250. So my solution is I have just found another sa250, and I will use the same cables, one amp for bass one for treble.

why not try getting another 6l6 amp, and using the same cables. you will then have the same sound but more effective power...

The Accuphase has variable gain, so I adjusted that to the proper level.

I assume the phase on the Amp's are right ( at least they were connected right ) but I will cheek ( sometimes Amp constructers are not that keen about this issue ).
The reason for mixing two amp's was to get the sweetness of the tubes and power from the transistors, the result was just not that good ;-).

But thanks for the replies anyhow. I was just curios If any body had good results with Bi amping these babies.

( and the wires was silver ;-) but don't start that discussion )

Im unfamiliar with the accuphase house sound, but my guess would be, that coupled with silver wire, it made the bass somewhat bright, solid state I find tends to be a bit brighter on average (every amp is different), im guessing that the tube stuff being SE and SET is somewhat warm and rounded compared to the solid state gear, and your not liking the lean sound the bass is getting.

The way you can confirm / tweak this is listen to the accuphase full range, swap cables around until you have the sound you want, then swap the tubes back in.

Accuphase has a great reputation, so im guessing you just need to find a cable that compliments it well. I always liked silver with tubes, and copper with solid state, I always use silver interconnects though.

This might be interesting for better bass...

I power my Ascents with 80W 211 based SE monos. I also use a Descent. So I have the two Ascent bass units SE powered, and the 3 Descent bass cones class D powered. Amazingly this works extremely well!!!

Also, with RCA 211s, the bass switch is at 40hz with the volume around three. Replace the RCAs with Amperex 211s, and the drop in LF output requires the 70Hz setting, with volume at 4-5!!! There is therefore a big change in LF response for these differing tube types. Both combos sound great.

Lesson? Try a sub, and do some tube rolling to find out which sub-settings/tube types work the best.

Also note the sub volume settings are just average ones. For bass light stuff, I generally mess around with it.

Also, some more tube watts, especially with a Quest (MLs have gotten much more efficient these days), will help a lot.

You can hear my system right now by listening to the clip on the following thread:

http://www.martinloganowners.com/forum/showthread.php?t=6798

Be sure to use headphones, though. And obviously, it is only a rough idea.

Enjoy.