So you have me thinking...
If you use a tube preamp to get the second harmonic rich sound: one produces. Do the second harmonics from the preamp get cancelled in the balanced mode?
The balanced mode tends to cancel the amplifiers harmonics. So its distortion figures are lower. But those harmonics are the ones generated inside of its own device.
If the amplifier input, to output is flat. And the output of the tube preamp is flat. In my head the harmonics from the tube preamp should pass right on through. Or not? Maybe someone can measure that?
If you use a tube preamp to get the second harmonic rich sound: one produces. Do the second harmonics from the preamp get cancelled in the balanced mode?
The balanced mode tends to cancel the amplifiers harmonics. So its distortion figures are lower. But those harmonics are the ones generated inside of its own device.
If the amplifier input, to output is flat. And the output of the tube preamp is flat. In my head the harmonics from the tube preamp should pass right on through. Or not? Maybe someone can measure that?
So then educate me on something I've never understood about SE amp specs.
Tor the ACA stereo version the power into 8 ohms is 8 watts. The power into 4 ohms is 5 watts.
I would expect the power into 4 ohms to be exactly half what it is for 8 ohms.
In every SE amp spec I've seen the power into 4 ohms is always a bit more than half what it is into 8 ohms.
Why is that? How is the power into 4 ohms and 8 ohms calculated for an SE amp?
Nelson, you numbers don't seem to agree with the graph I posted in post 6200 of this thread. I used the schematic for version 1.6 . The AP software won't allow you to change load impedance without resetting the graph so I overlaid two graphs with Paint.
Highlights:
Single channel:
8 Ohms 1KHz 7W at 1%.
4 Ohms 1KHz 10W at 3%.
For Balanced drive at 8 Ohm 1KHz I got 20W @ 3%, 12W @ 1%.
For SE drive Bridge at 8 Ohm 1KHz I got 20W at 4%, 6W @ 1%.
I didn't test parallel mode.
Highlights:
Single channel:
8 Ohms 1KHz 7W at 1%.
4 Ohms 1KHz 10W at 3%.
For Balanced drive at 8 Ohm 1KHz I got 20W @ 3%, 12W @ 1%.
For SE drive Bridge at 8 Ohm 1KHz I got 20W at 4%, 6W @ 1%.
I didn't test parallel mode.
Without going into specifics and using vernacular vs. engineering terms, I think it depends on whether the limitation to the max power is available current or the max voltage at clipping into the load. There's probably more to it though.
If you are current limited, you'll have lower maximum rated power into the lower impedance load.
What current would be necessary to be able to drive a 4 ohm load to clipping at 32V? What would the total power output be? How about for an 8 ohm load?
What if my amp only had 1A0 of current available until I reached temp limits or some other design limit (bias current)?
SE is (generally) current limited / heat limited - thus you may see lower max power ratings into lower impedance loads. However, some amps have oodles of output devices, big ol' honkin' heatsinks, or use other methods and will drive either a 4 or 8 ohm load to clipping at the same voltage. If you're seeing amps that show that they're stable and have increased max power output down to 2 ohm loads, you've likely got a beast on your hands.
At least I think that's the basic concept. Others far more knowledgeable can fill in some blanks as needed.
If you are current limited, you'll have lower maximum rated power into the lower impedance load.
What current would be necessary to be able to drive a 4 ohm load to clipping at 32V? What would the total power output be? How about for an 8 ohm load?
What if my amp only had 1A0 of current available until I reached temp limits or some other design limit (bias current)?
SE is (generally) current limited / heat limited - thus you may see lower max power ratings into lower impedance loads. However, some amps have oodles of output devices, big ol' honkin' heatsinks, or use other methods and will drive either a 4 or 8 ohm load to clipping at the same voltage. If you're seeing amps that show that they're stable and have increased max power output down to 2 ohm loads, you've likely got a beast on your hands.
At least I think that's the basic concept. Others far more knowledgeable can fill in some blanks as needed.
in theory it does, but i have made a lot of hybrids before, the differences were subtle, but both enjoyable....
class A SE amps have efficiencies in the 25 to 50% of input power, this is one way to look at it, with tubes, it is even less if you consider total efficiencies.....that is from wall to speakers...
I simply measured the unit that Variac brought up here. Since your
numbers are better, I will be happy to use yours.
Hi. I am noob in audio and electronics, but I loved the idea to build the Amp Camp Amp yourself and enjoy it's nice sound in my living room. Could anybody please advice me what speakers should I be looking for (or even better - making them myself also from the kit) that would be a nice companion to the ACA? What are the main characteristics of the speakers that would go well with this nice amp?
Well, that is a really subjective question that can not be specifically answered, but I'll say this.
8 Ohm gives the most easy power. Horns are usually very efficient, so a small amount of power goes a long ways.
Something like the Econowave style speaker should be a good choice, Klipsch Heritage series should be good, etc...
I have run my KEF LS50s with them in parallel mode and they worked well, but I felt like I did not have enough overhead power (though they never clipped....).
8 Ohm gives the most easy power. Horns are usually very efficient, so a small amount of power goes a long ways.
Something like the Econowave style speaker should be a good choice, Klipsch Heritage series should be good, etc...
I have run my KEF LS50s with them in parallel mode and they worked well, but I felt like I did not have enough overhead power (though they never clipped....).
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Thanks for the comment, @SiliconTi.
Then can I ask if streaming Spotify from the phone to ACA and that small DIY speakers
Buying a Overnight Sensations? - SoundImports
in the bedrum is a reasonable setup, or is it a waist of the good amp?
Then can I ask if streaming Spotify from the phone to ACA and that small DIY speakers
Buying a Overnight Sensations? - SoundImports
in the bedrum is a reasonable setup, or is it a waist of the good amp?
Those speakers are very inefficient @ 83db/W and only 1db up on the Celestion SL6 I used to use way back.
It is all so subjective that it's hard to advise really. You won't raise the roof, that's for sure but it will still play quite 'loud'.
Ideally the ACA needs to be used with something efficient and that also presents a relatively flat impedance curve... but until you try it you will never know.
The ACA can be partnered with speakers costing 10 to 20 times the cost of these... the amp is not the limiting factor for sound quality but it does have it's limits on what it can drive to high levels.
If that makes sense
It is all so subjective that it's hard to advise really. You won't raise the roof, that's for sure but it will still play quite 'loud'.
Ideally the ACA needs to be used with something efficient and that also presents a relatively flat impedance curve... but until you try it you will never know.
The ACA can be partnered with speakers costing 10 to 20 times the cost of these... the amp is not the limiting factor for sound quality but it does have it's limits on what it can drive to high levels.
If that makes sense
I simply measured the unit that Variac brought up here.
I confess the internal wiring was pretty sloppy with longish runs. I was focused on making sure my new rear panel switching system for V1.8 worked correctly. Well it worked but It didn’t correspond with the proposed rear panel labeling correctly. Nelson helped me see the errror of my ways within seconds!
Now the rear panel is labeled correctly and I neatened and shortened the wiring and at least it looks better. And there’s the problem with just measuring one amp-it doesn’t apply exactly with others. Especially because they are handmade by individuals! So take measurements with a grain of salt....
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I am planning on using my ACA 18 the DIY GR-Research X-LS Encore standmounts from Danny Richie (just Google it, you'll find it). Danny is a big DIY proponent and all his speaker sets are sold as DIY kits. The basic kit is only $250 and you can order CNC cut flat packs for the cabinets from Peter Rawlings or affordable built-up cabinets, finished or unfinished from Killian Smith (contact me via PM if you want their emails).
The speakers have 87 dB/1Watt efficiency, and a nominal 8 ohm impedance, so they should be easy to drive.
My recommendation? the GR-Reseach X-LS Encores I've linked above...they will be better, trust me on this. Danny Richie at GR-Research ships worldwide.
An externally hosted image should be here but it was not working when we last tested it.
Not a great impedance curve. Especially with the bridged ACA you will hear that midrange bump, not as bad with a stereo ACA, and likely not an issue if in parallel.
dave