Considering Large Tube PushPulls... Advice!

Well, I assume they are not using different drivers. I don’t get it.

 

now I am in fact curious myself due to you two. I will make note of this.. The double impacts are standard spec’d at 4ohm. They can be wired to 8 upon request. Keep in mind there are 11 drivers technically in this unit, so is it really in fact not as simple as an alternate means of wiring, aka series vs parallel and so on? Meanwhile, the lores come in 8ohm and do not note 4ohm as an option. Maybe this would dispel the notion of them using resistors to alter the impedance, as it would possibly mean they would have the same option of impedance selections for the lores as well would it not?

I actually spoke vtl over the phone today as well as tekton. I was after an answer as to which impedance would be ideal between 4 or 8, for the vtl units. I was ultimately unable to yield an answer from them as to a preference of 8 or 4ohm speakers for their amps.

 

No one could give you a perfect answer. The only way you know is to listen to the speakers. Tube amp at 8 ohms usually sound a little better on 4 ohms speaker load due to lower distortion at higher volumes. Or if multi-tap output transformer connecting the amp 4 ohm out on 8 ohm speakers. Does same thing, audio transformers reflect back twice the audio transformer rated primary impedance. Problem is tubes are rated at 'X 'watts out at 5% distortion (single-ended) and lower distortion (push-pull). Some tube amp manufactures follow the tube specs and the smarter manufactures tune the tube for best sound and power output. That is why some amps rated a PP pair of KT-88 at 40 watts and others at 30 watts using approximately the same plate voltage. I take the 30 watt rated amp.

 

The thing is that if they change the impedance of the driver, it will throw-off the entire crossover network. My resistor suggestion was largely intended as a facetious suggestion of an absurd solution.

Something just doesn't smell right about this claim of being able to change the impedance of the drivers without screwing-up the performance of the speaker.

 

I have read that they use a pretty simple crossover for the center tweeter so it functions as a super tweeter and the surrounding tweeter array is left to run down to 650 Hz with no cutoff. No idea on the larger drivers.

The little I know about a Zobel network is that it doesn't alter the crossover performance, but changes the load that is presented to the amp.

 

I believe they use different woofers in the 4ohm and 8ohm versions

 

Update-

I have decided to go with tube monos. I am between rogue m-180 monoblocks, or a pair of vtl mb 450. They will be paired with Tekton Enzo XL floorstanding speakers ( 2 10" woofers, 3 tweeters). They are rated 95db, but were measured at 90db by stereophile, thus are 90db. Yes, the VTL's would have more power than ill need, but it wont hurt... The rogues will be cheaper, but the vlt's wouldnt be out of reach, so i am tossing between the two. Would it be safe to assume the vtl's would have firmer control over the low end due to their wattage? I dont think that it would be a safe 'assumption' based off of wattage alone. You would assume larger power supplies with the vtl's but its not all their is to the story. If anyone can compare these mono's, please do so!

 

I would suspect that the VTL might be a smidge tighter on the bottom. But that is just a guess. However the exact choice of which output tube that you decide to roll-in will probably make a bigger difference in regards to the bass tightness than will the choice of which P-P tube amp you decide to buy.

 

I've never heard the Tektons before, but I thought his sensitivity ratings have been challenged more than once. That said, have you looked into Linear Tube Audio at all? I've heard some pretty good things about them and they are often paired with Spatial's open baffle speakers with good results.

The Z40 Integrated is not cheap, but it seems pretty reasonable for an all made in the USA integrated with enough inputs and features to be an end game amp for some. Cirsuit designed by David Berning, Case work done by Fern & Roby. Tube goodness with solid grip bass is what I've read in some reviews.

There is also the Z40 Amplifier that can be mono blocked for 80 watts ... pricey for sure though.

 

Yes, as stated above the Enzo xl is actually 90db not it’s claimed 95. However it’s impedance curve is pretty nice, staying above 8ohm through most, just touching a tad below 6ohm for a moment. Hence, a friendly load for tube amps to drive.

 

I'm not familiar with the 450 design, but I am with their older 225 & 300 monoblocks.
PLEASE make sure the 450 has a soft start design feature!
Trust me on this one...