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
erik_squires
16,118 posts
 

The voltage gain of amplifiers is a convention, but not a rule. I think most solid state amps have 23 or 26 dB of voltage gain, but there’s no rule that forces this number. Lower gain may be a good thing given that so many preamps have too much gain already.

Also, there's no correlation between amplifier power and voltage gain.  From 50 to 500 Watts, amps following the convention will be just as loud at the same input.

mlsstl
1,437 posts
 

I had a situation that was opposite of the "too much gain" scenario. I tried to use a Schiit Saga preamp (unity gain) with their Aegir power amp which is on the low side of amp gain. I had to turn the volume up to near max on most recordings to get an average listening level. That meant when I tried to play recordings with lower-than-average volume levels I was unable to reach my desired volume even though the amp had more than adequate power. I solved the problem by selling the Saga and switching to their Lyr 3 which has switchable gain (+3.5 dB or 17.5 dB).

 

russ69's avatar
russ69
3,516 posts
 

I tried to use a Schiit Saga preamp (unity gain) with their Aegir power amp which is on the low side of amp gain. I had to turn the volume up to near max on most recordings to get an average listening level.

The Sega has no gain, your source has to be high voltage such as a CD player to drive an amp with enough voltage. If you were hooked to a low voltage source like a record player, you would run out of steam. And that is why active pre-amps exist. 

perkri OP
907 posts
 

Volume isn’t my problem :)

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

mlsstl
1,437 posts
 

@russ69 -- I know the Saga has no gain (that's what "unity gain" means.) And I was using a DAC with the typical 2 volt output, so nothing amiss there. While most of the time I got the desired playback volume, the problem was when the recording itself was recorded at lower than normal volume. Certainly not a problem with most pop/rock material, but there are some recordings out there where this can be an issue.  Its not an issue limited to certain turntables/phono preamps.

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