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Re: AIMS Amps

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11/26/1999 4:48 PM

Re: AIMS Amps

Psycho,

You probably know this already but with your mental condition I can’t be sure (g). The max rated dissipation of a tube is the max power the plates can dissipate which is just wasted heat. That max audio power an amp can put out without exceeding the tube’s max dissipation rating will depend on the efficiency of the amp circuit. I’ve never worked on an SVT but the schematic shows the 6550s driven by cathode followers so it could run in class AB2 and be more efficient than the usual AB1 guitar amp.

Dave

11/26/1999 9:12 PM

Psycho Bass Guy

I understand that Dave, but why didn't the tube manufacturers publish for more than two typical applications? Class A and Class AB1 ratings rarely reflect what a tube is truly capable of. Also, I see a lot of max value and typical value used interchangeably. Did they get lazy or just not have time to test the tubes in a lot of different circuits? ( I guess that's what we're here for!)

Psycho( you know it's me because the poser nevers asks technical questions)

11/26/1999 11:52 PM

The data sheets are accurate--to a point.

Often the tubes are driven from a low Z source that does not collapse under grid current. When they say 60Vpp input, they mean it with almost NO distortion.

They are also tested with a RESISTIVE plate load, which does not have any appreciable reactance, unlike an output transformer. In a real OPT the impedance "seen" by the tube is a function of the primary inductance (at LF) and a combination of leakage inductance and paracitic capactiance (at HF). Let's not even talk about the crazy load of a speaker.

You can also be sure that the power supply is a regulated bench supply more than capable of supplying the peak plate current. This is not often the case in real-world amps.

With the use of conversion factors you can interpolate operating points from the given tabulated data. Generally though, the plate curves are only good for quiescent operating conditions. I wouldn't rely on them for hardcore distortion figures... they are not that accurate.

As usual, the greatest power output from a given tube will be in class B--or class C if you want to disregard audio use. Unfortunately, running the tubes colder has other drawbacks.

Did you know you can get 100W from 2 EL34's? That's class B, and it's due to the fact that Va is 800V max. You need high primary impedance to avoid totally fucking the tubes though.

KG

11/26/1999 5:39 PM
Ken Gilbert	You can get 100W output power with 6550's... Pentode connection 600Vp 300Vs -32.5Vg 65Vpp input 5Kaa OPT 100WPo That is the 6550A however. KG

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