My build with this amplifier is almost complete (just cosmetics and speaker protection) and connected to a balanced source (tried both BII + NTD1 and the Mirand DAC + Discrete output) this amplifier sounds REALLY good. The mids are incredible and so are the highs. The bass is lesser than with my NX, B24 and USSA but it is still very good and well controlled, very natural. I have to do more listening sessions but last Sunday when I put it online with a bunch of friends over, they all liked it a lot.
Merry Christmas!
Do
Merry Christmas!
Do
The PWM boards are controlled by the dsp that also passes the digital audio signal to the dac's, so they won't operate on their own. The dsp is generating the correct PWM level that sets the correct voltage that is needed to output the required signal from the Extrema amps. And I don't have spares...
Everything works, and it adds no extra noise to the output. I did some hours of listening and testing. The PWM signal is very well filtered, and also the balanced layout keeps out the noise if there was any...
Result is the same audioquality but the amp runs quite cold now
At the moment I am constructing a housing for the amp (that matches the mediaplayer I build last year), because all pcb's laying around on my desk gave me a headache. Because it is a very Extreme amp I added a nice lcd display to make the design even more extreme
.New Extrema housing:
Some development of the interface:
The inside of my mediaplayer:
The mediaplayer, in the same style the Amp will be build:
Thanks. The mediaplayer is completely selfbuild. The computerpart is a pic32mx795 together with a vs1063 decoderchip. This chip decodes mp3, flac etc. and feeds i2s to two tda1541a's that do the conversion. The pic takes care of the tcp/ip stack and a Logitech squeezebox implementation. Display is a noritake itron gu3900 vfd. The mediaplayer also functions as pre-amp for two monoblock tube amps I build. These amps have two kt88's each.
The build is almost complete, so time to post some pictures and a block diagram of the complete amplifier.
![URL]](https://www.diyaudio.com/forums/[URL=http://s732.photobucket.com/user/gojita2025/media/DSC00629.jpg.html][IMGDEAD]https://i732.photobucket.com/albums/ww326/gojita2025/DSC00629.jpg[/IMGDEAD][/URL])
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Here is my low power modification that uses slightly modified ExtremA output stage in the opamp feedback loop, together with measurements performed with Audio Precision AP 2700 series system:
PM-A4 power amplifier
PM-A4 power amplifier
Hi all
I learned about the ExtremA design a few days ago, and I very interested in this. I had planned to build a FirstWatt F5 Turbo, but after listening to a standard F5 for a while I am not so sure anymore. So I am wondering if (some of) the parts I already bought for the F5 Turbo would work for for the ExtremA.
For a 100W / 8-Ohm class-A build I am estimating a peak current of 5A and a peak voltage of 39.5. This gives a bias current of 2.5A and a PSU voltage of about +/-40 V, which translates to a dissipation of 200W per channel. Correct?
So (for a single channel):
Any comments and ideas (or corrections to my math, if necessary) would be appreciated.
I learned about the ExtremA design a few days ago, and I very interested in this. I had planned to build a FirstWatt F5 Turbo, but after listening to a standard F5 for a while I am not so sure anymore. So I am wondering if (some of) the parts I already bought for the F5 Turbo would work for for the ExtremA.
For a 100W / 8-Ohm class-A build I am estimating a peak current of 5A and a peak voltage of 39.5. This gives a bias current of 2.5A and a PSU voltage of about +/-40 V, which translates to a dissipation of 200W per channel. Correct?
So (for a single channel):
- I have two 800VA toroidal transformers, each with two 30 VAC windings.
I'd estimate my transformers would give close to 40 VDC after rectification (assuming a diode loss of 1.4V), so that should work. - I have eight heatsinks, each 300 x 150mm, with 83mm fins. I'd estimate each heatsink to around 0.2 K/Watt or so. So using a single heatsink would give a temperature rise of around 40K, or about 70 deg.C on a warm summer day in Switzerland (just a crude estimate). That might be acceptable, but using two of those heatsinks would be nicer (to be on the safe side). What are the possibilities to spread out the power transistors to two of those heatsinks? Can I use wire connections to separate the transistors from the PCB? What wold be the max. wire length for this?
Any comments and ideas (or corrections to my math, if necessary) would be appreciated.
Outputs of each channel are bridged, so you not need so much supply, just a half of peak 39,5 V + something to saturate output devices, say +-25 V must be well enough.
And you must knew, that speaker is an active load, so current draw can be easily doubled at rated power, especially at high coil movement.
So 4 huge heatsinks? Are you shure?
~600 mm depth or ~300 mm height?
With lowering supply rails you will get much lower dissipation.
And double calculate, do you REALLY need 100w/8ohm. I suppose, that even with very ineffective speakers 20-40 W would be well enough for home listening. This amp must not be used for stadium scoring.
So, with design goals at conservative/moderate peak wattage you can safely use one heatsink per channel.
Uuups, yes, you're right. I forgot it's bridged.
What happens if the source is NOT balanced? If the "negative" input is grounded, the "negative" branch of the output stage would stay at GND, right?
What is the PSU voltage in the 100W/8-Ohm setup described in the original text at hardwareanalysis.com? I couldn't find this in the article.
Yep, I am aware of that. Just trying to get a ballpark idea of where I would end up with the parts I already have.
Not sure yet, again, just trying to understand what my options are. The idea with the F5 Turbo was to separate the driver part of the amp from the output stages, and have four output stages each on their own heatsink (for a monoblock). That's not so easy with the ExtremA, because the driver and output stages are on the same PCB. That's why I asked for the max. lead length between the power transistors and the PCB.
Sure...
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