The impedance question.

Thanks.

Looks like this is for calculating the total resistance of parallel resistors. I don't see how I would use it in my circumstance.

 

I would think that if you are experiencing HF roll off, the splitter would be a serious culprit.
Adding multiple areas for loss of signal...like the splitter above, is not really a great idea for ultimate SQ, IMO.

 

Could be.

I won't really be able to judge the sound until I end up sending the preamp to ARC and get it back. I think it is likely that nothing has been done to it since it left the factory in 1980.

This is just a preamp that I thought I would probably like (after servicing) and the price was right. So far, I just hooked it up to see that it was working. I did not expect it to be up to spec.

I was interested in the impedance matching info. Sounds like I am in the ballpark on that. When I get around to the restoration, I will discuss that further with Audio Research.

 

The input impedance is a measure of resistance. Two inputs = two resistors.

Splitting the stereo signals into 4 channels to biamp means your pre is seeing 16.5K ohms, not the original 33K.

Adding the effects of a double run of IC's, will change things too. You might be better off with a single set of IC's and have the Y-splitter at the amp end.

If you biwire from the amp to the speakers, the pre will see the original 33K.

This is why some subwoofers, like REL's, take the signal from the amp outputs. Besides picking up the sonic signature of the amp, this method frees the pre from having to work harder. This is especially important if your pre has an unusually high output impedance, or if you are running a passive pre.

BTW, your pre's output impedance of 500 ohms isn't terribly high. one tubed preamp that I owned a couple of years ago had an output impedance of 2.5K ohms.

 

Someone correct me if I'm wrong but I believe some of the Rowland preamplifiers were transformer coupled - eg, perfectly capable of driving a 600-ohm load.

For the OP's setup - and in the majority of consumer applications - the higher impedance options is the better option for coupling a linestage to an amplifier.

For example, my venerable McIntosh 2100 has an input impedance of 250kohms. That means anything from a Dynaco PAS (high output impedance) to an Adcom 555 (low output impedance) has no issue with drive - high or low frequency roll-off.

 

It hurts, but there are copper versions that are maybe the best thing to use if you need them to evaluate loading scenarios.

 

I can't speak for a solid state preamp, but what you ask about mating a tube preamp to a solid state amp is true. In fact, I just went thru this exploration regarding a VTL 2.5i tubed preamp and a McCormack DNA 0.5 amplifier. The McCormack has an input impedance of 100kOhms, which is plenty for the VTL preamp. Lower values (and/or) long cable runs could potentially affect bass & treble the performance of the two together (rolled-off frequency response). According to VTL..."Generally for full frequency response it is advisable to match component impedances with a look-up factor of at least 200." So, the 2.5i has an output impedance of 200ohms - the DNA 0.5 would have no problems at all with it - in fact, I was told it would be a perfect match.

 

Is there a problem with a very low output impedance, for example 0.2 Ohm or 2 Ohm from preamp and 2,000 Ohm input impedance at power amplifier?

 

No. To minimize voltage loss at the input of the amp you'd like to have the amp's input impedance (the load) be at least 10X higher than the preamp's output impedance, so if you ave a 2 ohm output impedance on the preamp, 2k ohm is well more than 10X that source impedance. That said, those are very unusual numbers for hifi devices.

 

The 10X rule is not etched in stone. It's a rule of thumb.

 

Sure but its a rule of thumb based on basic science if the concern is minimizing voltage loss at the load input. More than 10X is even better. Can you get by with less that 10X? Sure.

 

Chervokas I am using Australian made ME24 preamp, 2 ohms output impedance with ME850 power amplifier which has input impedance of 2,000 ohms (balanced) in unbalanced mode.

I am considering using a Violectric V281 headphone/power amp with the preamp which has input impedance of 10 kohms.

The output impedance for the V281 if used to power speakers is stated at < 0,1 Ohm unbal. / < 0,2 Ohm bal.

 

Very unusual design with those ME products. Not sure that ME850 would work all that well with most preamps out there with more typical 600 ohm or 1K ohm output impedances, but obviously those pieces were designed to work with one another. This other amp you're looking at -- with a 10K ohm input impedance and a 0.1 ohm output impedance -- is much more typical for a solid state amp (though 10K input impedance is a bit low in a general sense, more typically you see 50K ohm, but irrelevant if you're using a preamp with a 2 ohm output impedance).

 

I found that audio sounds best when the amps are hit with a hot level. Low levels sound wimpy and lifeless.

I'm not sure this is what this discussion is about but I'd just set it and see (listen) which sounds best.