2. amps-preamps
  3. 182100-102678

My 30 Watt class A is louder than my 100 Watt Class AB?

Curious observation…

I had just done some work on my DIY Hiraga 30 Watt Class A amp, and decided I would do an A/B comparison with my Adcom GFA 545.

To my great surprise, when I switched from the Hiraga to the Adcom, leaving everything else in the set up the same, and when I turned the music back on, it needed to be turned up to play at the same volume.

Input impedance is different, and I’m wondering if this is what could be causing this counter intuitive finding? Hiraga is around 33K and the Adcom around 100K.

Wondering if anyone has any thoughts as to why this is what I’m experiencing.

Thanks

 

perkri

Showing 5 responses by perkri

perkri OP
889 posts
 

Heard back from Stanton re: the Hiraga specs

Input sensitivity is .5v

30db of gain - not 26 as I had thought.

That would explain the volume increase!

The Cary SLP-30 I am driving it with has variable gain, so I gave some wiggle room to play w that adjustment.

perkri OP
889 posts
 

@yogiboy 

Thanks!

That was what I thought. Wasn’t until after I had listened for a bit that it dawned on me the impedance difference was the cause.

perkri OP
889 posts
 

Thanks. I re read the answers, watched the video, and it’s a bit clearer now! 

Hiraga has a gain of 26db, input sensitivity TBD.

Adcom has a gain of 27db, and an input sensitivity of 1.25V

I’m going to contact the vendor for the Hiraga PC boards I bought, and see if I can find out the input sensitivity.

perkri OP
889 posts
 

Volume isn’t my problem :)

Using 4ohm 84db speakers, I never go past 11 o’clock on the dial :)

perkri OP
889 posts
 

Very much appreciate the input/information!

This surprise, sent me down a rabbit hole of “research”.

Now, I have more questions than I had prior to this observation :)

 

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