got this itch..............valves for bass duties

[paulf-2007]

Now that I have got around to rebuilding my new open box bass cabs, due to the originals being too tall and the 200Hz tractrix horns obscuring the 65" plasma my thoughts have turned to driving the 15" bass drivers with valves, but which valve is going to have enough grunt to compare with the Rotel 130w solid state I am happy with and does the job well. The set up is tri-amped with 4w sets driving BMS compression drivers 118db and Raal ribbons 95db. Bass drivers are eminence alpha 15A 97db but low power just doesn't cut it.

 

[speedysteve]

For me it is more complex than just grunt. Damping factor plays a part - do the amps control the bass cones to the best outcome.

For bass, high damping factor is generally indicated to be good. Too high and it might seem like you have less bass, too low and it is flabby and slow / out of sync.

Valve amps usually have lower damping factors. Only one way to go - test yourself forward.

Guess I am teaching granny to suck eggs here.

I prefer my the 80W T amps on my Tapped horns (Kappa LFII's) and mid bass horns (Kappa 15A's) both Eminence, than any of the valve amps I've tried. OK I have not tried really big valve amps as I don't have any, but KT88 PP and other smaller fair.

Now that I have got around to rebuilding my new open box bass cabs, due to the originals being too tall and the 200Hz tractrix horns obscuring the 65" plasma my thoughts have turned to driving the 15" bass drivers with valves, but which valve is going to have enough grunt to compare with the Rotel 130w solid state I am happy with and does the job well. The set up is tri-amped with 4w sets driving BMS compression drivers 118db and Raal ribbons 95db. Bass drivers are eminence alpha 15A 97db but low power just doesn't cut it.

 

[paulf-2007]

Mmmm probably why SS works better. Better just put some cream on that itch.

For me it is more complex than just grunt. Damping factor plays a part - do the amps control the bass cones to the best outcome.For bass, high damping factor is generally indicated to be good. Too high and it might seem like you have less bass, too low and it is flabby and slow / out of sync.

Valve amps usually have lower damping factors. Only one way to go - test yourself forward.

Guess I am teaching granny to suck eggs here.

I prefer my the 80W T amps on my Tapped horns (Kappa LFII's) and mid bass horns (Kappa 15A's) both Eminence, than any of the valve amps I've tried. OK I have not tried really big valve amps as I don't have any, but KT88 PP and other smaller fair.

 

[Valvebloke]

It can be done. But the amps would have to be fairly humungous. Low bass at high power needs a great deal of iron in the output transformers. In general the increased winding area that big iron requires generates problems with stray capacitance which knacker the high frequency performance. At a sufficiently high power the point is reached where a stable amp covering the full frequency range is simply impossible to build. I don't know if the power you need exceeds that limit or not (perhaps not, actually ?). You are in the fortunate position, however, of not needing any high frequency performance. So the OPT design might move from 'impossible' down to just 'challenging'. In that case you'd be talking custom trannies though, so not cheap. An alternative might be to monoblock a couple of high power stereo amps, or even to consider paralleling their outputs to get more power. You'd only gain 3dB each time you doubled the number of amps of course. So diminishing returns would set in very quickly.

VB

 

[lee1975]

J.wood all day long kt88 loads of grunt and power with transformers as big as they come. I have not heard another valve amp yet that does bass as well. Great amps that's not to say other amps don't do bass but yet to hear one that does as well as a j.wood.

 

[speedysteve]

Plus of course they must NOT hum - as NSM has found out with the mid bass horns

Silicon is good at not humming - when it's not bust.

 

[anubisgrau]

go and read whatever you can find on romy's site about his 6C33C amps. i've heard an amp made along a similar route (not feeding both triodes) with only 6-7w per channel, the best bass i've ever heard, iron grip but tuneful and melodic

 

[RobHolt]

Some loudspeakers seem to prefer less damping factor, particularly older high sensitivity types.

 

[RobsterD]

Ming Da 805's have been the best amps I've had on the 15" bass drivers ,nothing solid state has seemed to gel and I've tried loads !