Acoustat Model 3 Questions

[DaveG]

"I suggested that to measure the DCR place say a 10 ohm resistor in series with the meter"

yes- missed that and good point, and I will also re-measure when I get a chance.

[john65b]

I have a precision 10ohm resistor that I used,and both of my Model 3's DCR at the Speaker input taps were 1.4 ohm.

I guess with the new C-Mod, and 10 ohms across the HF input tranny, the HF Balance adjustment could influence the reading a little bit??

[DaveG]

Varying the HF balance should not change the input DCR because the new "C" mod configuration of the capacitors block the HF transformer resistance from being in parallel with the LF transformer and the 1 ohm resistor. So the C mod also slightly (maybe 0.2 ohms) increases the DCR resistance the amp sees over the original interface wiring.

[jackaljohn]

Sorry for an off-topic post.I am new here and I need some quick advice.
I have a pair of Acoustat Model 3's I want to sell but I need to test them. All I have to test them with is a live-sound style amp ( Crown XLS 602 ). The rown is rated at 600 watts RMS @ 4 0hms/channel.
Is it safe to use this amp with these speakers? I don't want to damage them.
I apologize.Thanks for your help in advance.

[kevinkr]

jackaljohn, You're new here, but please do not post the same question to multiple threads on the forum. Once is enough. Thanks.

[jackaljohn]

I'm sorry. Thanks.

[bear]

Dunno if this Q was posted in another thread or not... but yes you can use that amp, just don't crank it all the way and it will be just fine. The impedance of the Acoustats is around 6 ohms, the DCR is not the same as impedance.

_-_-bear

[john65b]

OK, been a while, but I have been going back and forth on whether or not I want to keep these...but still playing around with more mods in the meantime...

The latest mod is the Bias...I don't know how you can get 5kv from a 750v secondary with a 5x voltage multiplier (seems to me thats no more than 3750v), so I added one more diode and cap to the ladder...I should be at 4500v now... see below - existing and with new 1N4007 diode and a 1000pf 5000V ceramic cap I had laying around...can't really tell if it made a big difference, but I need to listen a little more...It should be easier to drive now with 750v more bias, and louder too...

[tyu]

I Add two...your right the bais in all the Acoustats 121 interfaces are low....the best mod i have done to the Acoustat is to get the bias off the mixer board...an set it up so you can set the bias...my setup is from about 4k-6k...your right i can drive my M3s with a 50watt tube amp....I saw you were saleing....these M3 well kill the logans...goodluck

[bolserst]

Originally Posted by john65b

The latest mod is the Bias...I don't know how you can get 5kv from a 750v secondary with a 5x voltage multiplier (seems to me thats no more than 3750v)

The sections of the voltage multiplier are charged up to the peak of the AC waveform like any other rectified power supply with filter capacitors. The peak of the 750VAC waveform is 750 x sqrt(2) = 750 x 1.414 = 1060Vp.
So, output of the 5x multiplier(assuming no losses) is 1060 x 5 = 5300VDC.