About 220W to 230W power dissipation, all the time and gets typical “Class A hot”, that is about 50C (maybe less since I have 375mm deep chassis that still needs to be tested) at the heatsink fins. Rest of chassis about 35C. Yes, works very well with 10F/RS225 FAST. I use it as my main amp for this speaker.
Any updates on the matching preamp? I am very excited to get my ears on the A40, and doing some shuffling of gear right now and am in the market for another preamp as well. I am a sucker for matching components.
Hi Inoculator,
Thanks for your interest. I am stuck at finding time to build the verification board of the combined soft start/solid state relay/PSU main board for the A40. It’s basically a combination of 3 boards into one to simplify production and assembly. This will nudge me to work on it a little more. Thanks for asking.
Thanks for your interest. I am stuck at finding time to build the verification board of the combined soft start/solid state relay/PSU main board for the A40. It’s basically a combination of 3 boards into one to simplify production and assembly. This will nudge me to work on it a little more. Thanks for asking.
Howdy all. Thanks to Hugh and XRK for bringing us Alpha Nirvana.
Please put me on purchase list for 1 complete amp, 8R, 117V 60Hz. I'd like to include any potential cap upgrades, etc.
I have 3 speaker models in rotation, all having:
Speaker #1 90 dB, 8R; speaker #2 96 dB, 11R. What risk if any exists from occasional use of speaker #3, 4R, true 96 dB?
Is there a "Standby" mains switch and if yes, what is mains current draw in Standby?
How long after switching from "Off" or "Standby" does it take to sound its best or say within 75%?
Thanks.
Please put me on purchase list for 1 complete amp, 8R, 117V 60Hz. I'd like to include any potential cap upgrades, etc.
I have 3 speaker models in rotation, all having:
- Benign phase angles
- Moderate ratio of minimum to nominal R
- Bass reflex w/natural cutoff around 70 Hz
Speaker #1 90 dB, 8R; speaker #2 96 dB, 11R. What risk if any exists from occasional use of speaker #3, 4R, true 96 dB?
Is there a "Standby" mains switch and if yes, what is mains current draw in Standby?
How long after switching from "Off" or "Standby" does it take to sound its best or say within 75%?
Thanks.
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YMMV but I personally find Poseidonsvoice opinions to be pure unadulterated gospel and nothing else.
There is a mains cutoff rocker switch on the IEC that completely turns everything off. In standby, there is 5W (max) current draw for the AC/DC 5v PSU to provide power for the logic control on the SSR switch.
Once switched on, music can play within 5 seconds. For it to reach full steady state temperature takes about an hour but I think full performance is within 2 minutes.
90 to 96dB sensitive 8R to 11R speakers should work great. 4ohms but 96dB should work well too. I have driven XSD which are 4ohms and 93dB and it works well. Depends on what your max SPL needs are.
I found impedance and frequency response charts for my custom Selah Voce 3 way speakers.. my new plan is to use the A40 to power them in my nearfield setup with an eversolo dmp-a6 with upgraded linear power supply as the streamer/dac/preamp
it should be fine at non-extreme volume levels right?
lol also any update on development of the a40?
it should be fine at non-extreme volume levels right?
lol also any update on development of the a40?
Attachments
The reasons for delay include finishing up some other projects for delivery to our customers. But a large part of it was that we are also waiting on some major custom made components like the toroidal power transformers and chassis manufacturing always takes time. There are a lot of parts in a product like this. But we will get this built and moving soon. It’s our flagship product in XSA Labs / Vera-Fi Audio, so it will be done soon.
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We are making great progress with the latest pre production prototype build.
The front panel PCB for the VU meters and switches with Micromatch ribbon cable connectors look totally clean and pro:
Operation of power on / standby solid state relays (SSR) and soft start SSR, and speaker protection solid SSR are working nominally. Front panel mute switch controls the SSR and that is working nominally. A lot of SSR’s - no mechanical relays on board.
Some measurements of distortion too. Here is distortion vs frequency for 1W - note consistent level of dominant second harmonic and very little higher orders:
At higher power of 30W, second harmonic is still dominant and higher orders are monotonically descending in relative level:
And distortion components as a function of power:
The amp is working well as designed. DC offset is currently about 13mV. We are working on reducing this by adjusting the LTP tail current more precisely.
A great job by Keantoken on this verification build.
Funny thing is, I don’t think Keantoken has played music through it yet! 😂
The front panel PCB for the VU meters and switches with Micromatch ribbon cable connectors look totally clean and pro:
Operation of power on / standby solid state relays (SSR) and soft start SSR, and speaker protection solid SSR are working nominally. Front panel mute switch controls the SSR and that is working nominally. A lot of SSR’s - no mechanical relays on board.
Some measurements of distortion too. Here is distortion vs frequency for 1W - note consistent level of dominant second harmonic and very little higher orders:
At higher power of 30W, second harmonic is still dominant and higher orders are monotonically descending in relative level:
And distortion components as a function of power:
The amp is working well as designed. DC offset is currently about 13mV. We are working on reducing this by adjusting the LTP tail current more precisely.
A great job by Keantoken on this verification build.
Funny thing is, I don’t think Keantoken has played music through it yet! 😂
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On the bench is a working A40 amp undergoing calibration of the VU meters. We decided to set the meters to 0dB at 8Wrms into 8ohms (8Vrms) vs 40Wrms. Because… customers like to see the meters dance with music playing at casual domestic volumes. If we set it at max power, it hardly moves and people complain or wonder if it’s working. 8W is a round number that most casual playing hits occasionally. Thats about 94dB at 1m for a typical 85dB sensitive 8ohm speaker.
DC operating points on this unit are:
- 1.67A/1.63A DC bias current through the output stage MOSFETs
- DC offset is 6mV and 19mV
- Rails at 29.5Vdc. This is a bit "hot" and probably can be reduced by 1.5V or so for production.
- Heatsink temps are 55C for a 25C ambient room temp. (29.5vdc x 2 x 1.67A = 97W) this should drop a bit if we lower the rail voltage.
- LTP tail current is 2.6mA
Typically, vu meters are set 0dB at max power, then there is 0.1X switch for one tenth of that.