Tube amps and speaker ohms

05-27-07: Bartokfan
True i did swap the KT90's for th eKT88's w/o biasing. But also had a KT88 NEW intergrated for demo purposes.

Was the new KT88 amp a Cayin? If so, it requires manual biasing. Tubes and tube amps require biasing whether they are new or not.

If the person from whom you obtained the Cayin did not bias the tubes before you received the amp, then it was not performing properly. I demo'ed a brand new Rogue Cronus last week, and I had to bias all the tubes after the initial warm-up (as mentioned in the manual). After running the amp for a half an hour, and before biasing the tubes, they were WAY out of bias.

Lastly, a tube amp paired with speakers that dip below 6 ohms may very well not work. On his product page, Tyler doesn't list impedance specs for most of his speakers, including the Linbrook Signature monitors, so it's impossible to determine why the KT88 amp you tried did not work to your satisfaction, but I suspect it had to do with a low impedance dip somewhere.

Tvad

The Tyler Signature Systems (1 Piece) have a nominal 4 ohm impedence and a minimal impedence of 3.5 ohms. I have driven mine with 160 wt amps w/6550s off an 8 ohm tap, 80 watt with KT88's off an 8 ohm tap, the PrimaLuna Five a 40wt amp with KT88's off the 4ohm tap (and 6550's as well), and my present Cayin a 70 watt amp w/KT88's off the 4ohm tap. The KT88's I was using are SED's. Power wise they all worked fine, the differences were in tone. I also used a 100wt high(ish) current ss amp and it in no way improved on the tube amps.

But, I also used another brand of KT88 in each of those amps and the sound of this KT88 was rolled off/enimic on both extremes and flat in the midrange. Very boring. I would have much preferred some of my 6550's, maybe even some of my old EI KT90's, if that was the only KT88 available to me. If I had speakers with no bass and a bright highs that particular tube might just be the tube needed.

I doubt that BF's experience has anything to do with Tylers Linbrook speakers impedence curve.

FWIW.

Divad, I am running a Tube Audio Design-60 with Vandersteen 2CE sigs (86DB I think. This amp runs 60 watts ultra and can be switched on the fly to triode (30 watts). This amp has plenty of juice for the vandys. I listen mostly to classic rock at room filling but, not loud levels and the vandys really sing. See Larryx7s post above. The TAD-60 can handle many EL-34 type tubes and is easy to bias. Check out the reviews on this amp. I haven't heard many other tube amps to compare but, I bet that it competes very well with amps in its $1300 class...

Eagleman

Newbee, can you provide a link on the Tyler website that contains impedance specs? Thanks.

I can't quite wrap my head around why some tube amps work with 3 ohm impedance loads and others do not. The Leben CS-600, which produces 32wpc with 6L6GC tubes sounded anemic and downright awful on the VR4 speakers, yet it is sweet, musical and downright incredible on the 5.5 ohm minimum Castle Howards.

The Rogue Cronus at 55wpc...just 13 watts more...brought the VR4 speakers to life. Yet, the Cronus has smaller transformers than the Leben.

On the other hand, the Cronus sounded congested and coarse on the Castles.

I'm sure someone like "Atmasphere" might explain it, but I'm at a loss. I do know that in general tube amps work better with higher impedance loads.

Tvad, This info came from the horse's mouth. I've never seen it in print, its what Ty told me.

Re impedences, there was an excellent thread in which Duke participated, within the last 6 months, where in not only were speaker impedence loads discussed but amp output impedences were also discussed. Amp putput impedences are seldome discussed and their impact is not generally understood. Most folks assume they are constant but they are not, they rise and fall with frequencies and have considerable impact of the sound which is produced by a speaker. You might be able to ferret it out by looking up some of the threads in which he participated. And, I think you are right the Ralph could help explain, but I can't recall if he participated in that particular thread. Maybe you could start a thread and get a discussion of this going and invite Duke and Raplph to participate. This may help you. Good luck......