2. amps-preamps
  3. 138608-16942

Help me spec n class A AMP, power calculation 85dB @ 1W @ 1metre

I was playing few pieces and recoding dB levels on my phone. After playing few tracks I see some parts of music sustains at 88db and peaks at 96db. I do like to hear music at this level for short periods of time. 

I am using the following calculator: https://geoffthegreygeek.com/calculator-amp-speaker-spl/

Sitting at 10 feet away from speakers I see the following numbers:

Assumption amplifier headroom of 1.5 dB, 10 feet distance

For 88db 1 Watt + 14.2 dB requires an amplifier power of 26 Watts
For 96db 1 Watt + 22.2 dB requires an amplifier power of 165 Watts

For 102db (room SPL losses) 1 Watt + 28.2 dB requires an amplifier power of 658 Watts (Ridiculous?)

It would be great if I can go get a class A mono blocks that can do sustained 200 Watts for each speaker @ 8ohm/6ohm and call it day but I got no dough for that.

How do I spec for a good amp(and may be integrated). I would like something that can sustain 35-50 Watts for class A and have reserves for peak of 200 Watts.

geek101
15 responses Add your response
glennewdick's avatar
glennewdick
1,689 posts
 

I don't think you will find such an animal anymore. I think there was one or two made years ago similar to that but not resent (didn't Luxman and Krell make a big power class A). Pass Labs, Sungden, Accuphase and luxman are the manufacturers that come to mind that still make class A but nothing with that reserve power range. Really 50wch class A is about the max your going to find unless the amp also goes into class AB. Pure class A above that requires so much power dissipated as heat its not really practical nor comfortable unless you live in an igloo (ha that actually might be dangerous as the amp would melt the igloo most likely).

Hopefully someone else has a hidden class A gem they know of.

But in your nominal power output of 30-50wch pure class A your looking at Sungden. Luxman. Accuphase and Pass labs. few more but those are the biggest i'm thinking.

One more thing you may be surprised you may not need that reserve power if your speakers are a fairly easy load on the amp.

 Love Class A SS but man they are space heaters. Tube amps are less hot go figure.....

geek101 OP
284 posts
 
The speakers I am considering are 85dB @  8 ohm or 86 dB @ 6 ohm :(.
auxinput
2,920 posts
 
Krell made a series of amps called FPB - Full Power Balanced.  They were all Class A amps, but not in a standard way.  They had an auto-bias circuit and did not push full Class A all the time.  You can tell this because the amps had an idle current that was much less than full power output.  Their new "Chorus/Duo/Solo" series of amps are very similar to this.
geek101 OP
284 posts
 
I am thinking Parasound JC1 , 25 watts of class A ?. Wondering if this will work.
auxinput
2,920 posts
 
Ah.,  JC1 are excellent amps and they will allow you to switch between low bias (10 watts) and high bias (25 watts) Class A.  Generally, Class A will give you warmer and more rounded tones.
luxmancl38
580 posts
 
I would look for a Threshold T-200. 100 wpc Class A. A great space heater. I have a pair of T-50's that I purchased of a former Threshold employee. They were modified at Threshold to run as 100 wpc mono blocks. Michael Bladalius did the modification. These amps run hot and look at your electric bill.
d2girls's avatar
Ag insider logo xs@2x
d2girls
1,029 posts
 
Pass Labs XA30.8, or (budget willing) XA60.8 monoblocks are just what the doctor ordered. 
geek101 OP
284 posts
 
XA60.8 seems to be capped at 60 Watts. Am I missing something?.
Post removed 
d2girls's avatar
Ag insider logo xs@2x
d2girls
1,029 posts
 
@geek101 yes you are missing something. you talk about "200w reserves" like you meant the amp is able to pull out an extra 200w if needed. I honestly assumed you were referring to amps that run class a for the first 10/20/30/50w or whatever, and transition to AB above that. If that is what you are speaking of (the way you formatted your post would lead one to believe this) then yes, the 60.8 can handle the peaks you're asking of.

if, however you were meaning you want all 200w of that power of class a and "in reserve" well sorry but no class a amp is going to be in a "reserve" state, its going to run hot, it's going to be heavy and it's going to be outputting a lot of power at all times. 

The only amps off the top of my head that offer up 200w in class a are Pass Labs, and Krell. There's plenty of others but most of them are in the 5 figure range. 
geek101 OP
284 posts
 
I do not need continuous 200w class A. I am looking for continuous 35w to 50w class A but the amp needs to supply the transient load of 200w. I have no idea how amps work. If the 50w to 150w swing would mean engaging class B then it is fine by me. Tube amps seem to not able to manage the peaks(this is my understanding), may be this is incorrect.

Where do I find specification that 60.8 can handle such peaks?
Post removed 
geek101 OP
284 posts
 
I am going to try out Line Magnetic 508ia. Will update the thread on how they sound with my efficient speakers now and when I change my speakers to less efficient ones.
astelmaszek
125 posts
 
Find a Luxman M800.

60 watts per channel into 8 ohms is the Class A power rating taking at nearly non-existent distortion. This doubles all the way down to a maximum of 480 into 1 ohm. Actual power, according to Stereophile, is 160x160 into 8 ohms, 280x280 into 4 with a maximum of 480 into 2.

geek101 OP
284 posts
 
Yes a used M800 seems great, there are concerns with heat issues. I think an SS that can go up-to 100 watts class A and is reasonably priced is Coda 15.5. 
Log in to respond
More to discover
80x80
SJS Arcadia Model 7 Line Preamp
Balanced Audio Technology VK 80 tube Preamplifier
80x80
Luxman CL-38uC