Multichannel looks very nice inside! 
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boXem A series
OP
- Thread Starter
- #102
This afternoon I ran a quick measurement of the A 4216/E2 with the new Purifi 1ET6525SA and I was nicely surprised, especially since the noise of the DAC (SU-9n) and preamp (A 70 pro) are making the values a bit pessimistic. Could do a bit better with a passive attenuator in place of the preamp.
- High gain is a sensitivity of 2V and low gain a sensitivity of 4V, so these are numbers (5W 4R SINAD 107/110 dB) attainable with real world sources
- The 1ET6525SA seems to be a very nice module but as I keep repeating, these new modules are so performant that the input/gain stage has now a real importance in the amplifier final measurements. With the reference design gain stage that most of our competitors are implementing with various opamps, expect a degradation of 3-4 dB if correctly implemented.
- High gain is a sensitivity of 2V and low gain a sensitivity of 4V, so these are numbers (5W 4R SINAD 107/110 dB) attainable with real world sources
- The 1ET6525SA seems to be a very nice module but as I keep repeating, these new modules are so performant that the input/gain stage has now a real importance in the amplifier final measurements. With the reference design gain stage that most of our competitors are implementing with various opamps, expect a degradation of 3-4 dB if correctly implemented.
OP
- Thread Starter
- #103
Measurements were done with banana plugs. Speakon is supposed to improve THD.
The idea behind the composite stage is to reduce noise even more without increasing distortion. Waiting for the production boards to provide accurate values.
The issue I am having right now is that the probes I am using to sense the signal have a significant impact on the measured THD, with values (notably H3) changing by several dBs between two measurements.
Do appreciate the ongoing finetunings, but aren’t we far exceeding what is possible to detect by human hearing, allready?
OP
- Thread Starter
- #105
Question is to provide a completed amplifier worth the modules it embeds. People pay a significant amount of money for an ultra high performance amplifier, I want them to have the product they paid for.
Max power is 210 W with an SMPS1200A400, so optimal gain is 20.4/26.4 dB.
The values you see on the measurements are lower than this for two reasons :
- measurements were done with a gain stage designed for the 1ET400A, so missing 0.5 dB. The production boards will have enough gain, which may degrade the results by 0.2-0.2 dB.
- the gain value REW calculates depends from the accuracy of the full scale in/out voltages entered as parameters and I have to admit that I didn't spend a lot of time on calibrating ultra accurate values
OP
- Thread Starter
- #106
I am saying that 230 W cannot be reached with a PSU with rails rated at 63 V. Better use a 65 V PSU for this.
This is a thread about boXem amplifiers.Buckeye say they are using this PSU and rate their amp at 230/480 watts.
Buckeye Amps
Buckeye Amps utilizes the most advanced audio amplifier technologies available. Authorized seller for Hypex and Purifi Class D amplifiers. Based in the US. Free shipping and worldwide service!www.buckeyeamp.com
It's not polite for him to point out mistakes from his competitors, you have to excuse him for that.
OP
- Thread Starter
- #109
On paper, the SMPS3k delivers 3000 W, that leaves 600 W per channel for a 5 channels amp. Perfectly good for 510 W + losses.
In real life, 2 channels are wired in oposition of phase to the 3 others, and audio signals are assymetrical . So at an instant t, each channel has even more than 600 W available.
Thanks. So, if a person got the A 4216/E5 vs the E4 or E3, they shouldn't see a drop in power even across a 2Ω impedance on any channel?
OP
- Thread Starter
- #113
The power supply is chosen to output a voltage as close as possible to the maximum accepted by the module. This will determine the maximum power of the amplifier.
Then the gain stage is configured in order to be able to reach the maximum power with a given input, 2 and 4 V on our case.
Is there a specific reason that would bring you to need a 29 dB gain?
To match the gain of my Class A/B amplifiers and to overcome the input sensitivity of 2V. Input sensitivity of Class A/B is closer to 1.5-1.6V. I would have to drive my pre-amp/processor less to attain the same SPLs.
OP
- Thread Starter
- #115
I am not sure if this is the best strategy for good sound. The higher the pre-pro output, the better it's SNR. And a pre-pro doesn't care about the gain differences between amplifiers since it already has to overcome the differences between speakers sensitivity.
That said, if you feel more comfortable with more gain, I perfectly respect this and would like to let you know that the A 5519/Nx allow a gain of 29 dB with the optional buffer.
OP
- Thread Starter
- #119
Talking here from the optional buffer for the NCx500 based A 551x/Nx, compared to the buffer embedded in the NCx500.
The optional buffer for the A 551x/Nx is indeed the standard one for the A 42xx/Ex with a different gain resistor.
I was wondering if you could share some measurements with the 1ET6525SA's input buffer as the previous tests were based on the 1ET400A's input buffer, also with your Arthur 4216/E2 & A 4216/E2 1ET6525SA based models will they both share the same gain settings of 20.3dB/26.3dB because the previous Arthur 4215/E2 & A 4215/E2 1ET400A based models had differing gain settings of 20.8dB/27.2dB & 24.3dB/30.5dB respectively?
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