[seefeel]

A few months ago I posted about how the Earmax Pro didn’t drive my HD600s to very loud volumes at all. In fact, I was able to turn the volume knob all the way up without it being too loud to listen to. I never did get to the bottom of why I (and some others) found the Earmax Pro had a very low output. Recently it dawned on me the importance of matching the input sensitivity of the amp to the output voltage of the CD player. My player has a normal output for a CD player at 2.5V. Now, the input voltage on the Earmax Pro is listed as 18.9V. Am I correct in thinking that this input voltage is the gain setting of the Earmax Pro? If this is the case, isn’t that number WAY too high for there to be any real powerful sound to come out of the amp hooked up to a CD player with an output of 2.5V? And wouldn’t that explain why I was able to turn the volume knob all the way up? Am I on the right track to finding an answer to my dilemma or am I way off base here?

In my old post about this, I mentioned that my friend's MG Head was much louder and more dynamic. Well, the input sensitivity for the MG Head says 300mV. Wouldn't this be another factor that validates my assumption that the input sensitivity of the Earmax Pro is to blame for my lack of loudness?

 

[taoster]

Quote:

Originally posted by seefeel A My player has a normal output for a CD player at 2.5V. Now, the input voltage on the Earmax Pro is listed as 18.9V. Am I correct in thinking that this input voltage is the gain setting of the Earmax Pro?

The line-level source going into the EMP will have a direct impact on the volume of the amp but the 18.9V isnt the line level, it's the voltage of the power supply for the EMP.

I am stumped on why it doesnt blast your HD600 into oblivion as it does on my EMP. Works equally well with the Arcam CD72, and the attenuated ART DIO DAC (as well as pioneer DVD players).

 

[Rob N]

I don't understand either.With the difficult to drive HP1000 phones I can only turn the volume about a third round before it gets to loud.

 

[JaZZ]

Have you ever replaced the input tube (ECC81 / E81CC / 12AT7)? It's a possible culprit for your problem. (BTW, the Siemens ECC81 is my preferred input tube.)

A healthy EMP fed by a normal CDP/DAC with 2 volt output can drive the HD 600 to extreme levels. I never had any volume problems with any headphone, even the K 501.

Or have you tried another CDP? It seems unlikely, but maybe your current source doesn't supply the specified output voltage. If nothing helps, contact Stefan Brocksieper (you may PM/e-mail me for his phone number)!

 

[seefeel]

I did try a different source with the same results. I also was using the same source on the MG Head which had plenty of output to the HD600s.

Are you sure the 18.9V is not the line level???
As far as I know, "INPUT SENSITIVITY" is always the line level or gain of the amplifier. If that is indeed not the case, does anyone know what the input voltage is on the EMP?

It seems like the problem is a gain related issue. It would make the most sense I think. Is there another input tube that would dramatically increase the input sensitivity of the EMP? JaZZ, is that what you are saying the Siemens ECC81 would do? I don't think just using a "better" tube will fix what my problem is. Remember, I can turn the volume knob on the EMP ALL the way up and still be able to keep the HD600s on my head. It would seem that matching the voltage more closely to the 2.5V of the CD player would be a fix, if that's possible to do.

 

[JaZZ]

Don't care about the 18.9 V. It's most likely the power supply's voltage, otherwise it would have been named «input sensitivity». The EMP is designed to work with normal sources such as CD players, and it definitely does.

Just try another one of the mentioned regular input tubes. This measure has the highest chance of success.

 

[taoster]

seefeel, you mean you havent tried different tubes to see if it's a problem??

if you dont want to fork out big bucks, get some cheap tubes and ask the seller to test prior to sending. There's lots of operational but bad sounding tubes going for cheap.

 

[Jim R]

There is something wrong with your EMP. I use a CDP with the exact same output with my EMP and you would never turn it past the halfway point of the volumn control with the HD-600's. I bet you have a bad tube or there is something else wrong with the EMP. If replacing the tubes doesn't correct the problem, send it back for repairs.

 

[Hirsch]

Quote:

Originally posted by JaZZ Have you ever replaced the input tube (ECC81 / E81CC / 12AT7)? It's a possible culprit for your problem. (BTW, the Siemens ECC81 is my preferred input tube.)

This cannot be emphasized enough. The center tube controls the gain. If the tube is worn, or bad, you won't get volume. It's that simple. If the 12AT7 (ECC81) has been thoroughly tested and is known to be good, then it may be another problem. Try changing the tube anyway, just in case.