Initial custom buffer design/pricing is done (very happy about the price). Not at all finalized, but would be using TI TPS7A49/30 voltage regulators, OPA1612, toggle switch for either "Norrmal" or "Low" gain (26dB/20dB range), slide switch for "On" "12v Trigger" "Auto Sense", PCB mounted Neutrik XLR connectors (with correct Pin 1 wiring), FastOns for connecting my own speaker binding posts (so can easily allow speakON option), Power LED....among other things.
The Hypex SMPS1200A400 is out of stock until end of April unfortunately. Would make a prototype hopefully in May to undergo testing (including tests similar to what Amir does to verify the input board performance, etc). So, fingers crossed, POSSIBLY June/July availability. Not going to take pre orders until the prototype is done and verified.
For a 2ch Purifi, I am shooting for a price range around $1129.
Somewhere on the internet, maybe here or maybe AVS, there was speculation that the actual voltage out was higher than 1v but that Onkyo was only promising a minimum of 1V across all pre-out channels. So there might be a higher voltage if you're only sending out the LR channel.1ET400A output spec = 425 W into 4 ohms which is 41.23 Vrms or 32.3 dBV so you'd need more than 1 Vrms to drive it to full scale. Onkyo does say on their website that subwoofer/pre outs are 1 V (https://www.onkyousa.com/product/tx-rz50-9-2-channel-thx-certified-av-receiver/).
i want to buy one.Initial custom buffer design/pricing is done (very happy about the price). Not at all finalized, but would be using TI TPS7A49/30 voltage regulators, OPA1612, toggle switch for either "Norrmal" or "Low" gain (26dB/20dB range), slide switch for "On" "12v Trigger" "Auto Sense", PCB mounted Neutrik XLR connectors (with correct Pin 1 wiring), FastOns for connecting my own speaker binding posts (so can easily allow speakON option), Power LED....among other things.
The Hypex SMPS1200A400 is out of stock until end of April unfortunately. Would make a prototype hopefully in May to undergo testing (including tests similar to what Amir does to verify the input board performance, etc). So, fingers crossed, POSSIBLY June/July availability. Not going to take pre orders until the prototype is done and verified.
For a 2ch Purifi, I am shooting for a price range around $1129.
I guess the gain needed for full power out of 1.5V (damn AV receivers don't reach 2V on their pre-out RCAs....) and 4.0V (balanced standard for DACs).So if I offer two gain options for my Input Buffer board, what would be the best targets to encompass the majority of equipment out there?
So if I offer two gain options for my Input Buffer board, what would be the best targets to encompass the majority of equipment out there?
How about 3 settings: high gain, low gain, no gain (bypass the input board)???
So if I offer two gain options for my Input Buffer board, what would be the best targets to encompass the majority of equipment out there?
March Audio P452IIRC the input impedance is pretty low without a buffer and the gain is also low. I am not sure 6~10 dB is adequate for anyone except those using "pro" equipment and thus fairly high output levels. I would be inclined to shoot for 20 dB and 30 dB or so but my suggestion would be to look at other amplifier offerings and see what they offer for gain and input levels.
FWIWFM - Don
There isn't enough usable advantage for a flow through option at 0dB in the input buffer to justify the extra cost of a 3 way switch. Or the user confusion it may bring. That configuration produces 10W at 6 ohms with 1.8V. The amp would need to be driven by an ADI-2 or the Benchmark LA4 to offer a reasonable volume with the 12.8dB gain. It might be interesting for testing purposes but I can't imagine recommending that setting for any home audio configuration. Two gain stages for the Purifi would be my preference.
Thanks Don, just curious.1ET400A output spec = 425 W into 4 ohms which is 41.23 Vrms or 32.3 dBV so you'd need more than 1 Vrms to drive it to full scale. Onkyo does say on their website that subwoofer/pre outs are 1 V (https://www.onkyousa.com/product/tx-rz50-9-2-channel-thx-certified-av-receiver/).
@Keened This is what I had heard as well.Somewhere on the internet, maybe here or maybe AVS, there was speculation that the actual voltage out was higher than 1v but that Onkyo was only promising a minimum of 1V across all pre-out channels. So there might be a higher voltage if you're only sending out the LR channel.
I would like to think they'd include the center in their plans as well but only the LR channels get the nice amplification (according to the manual/box) and I believe there are two kinds of DACs where the LR get a decent one and every other channel get the lesser version; so probably not. We'll know soon enough as the RZ50 review goes up.
P = V*I = V^2 / R = I^2 * R where P is power, V is voltage, and I is current. Note V = I * R so I = V / R to get P = V^2 / R
Gain in dB = 20*log10(Vout/Vin) = 10*log10(Pout/Pin) -- I usually work in volts since input sensitivity is specified in volts for given power output into given load impedance.
So Vout = sqrt(Pout * R) yes, and 26 dB of gain is a factor of 10^(26/20) ~ 20 V/V, so 1 V input yields about 20 V output instead of 26 V. Then run the numbers... If the overall gain to reach full-power output is 26 dB, then 41.23/20 ~2 V to reach full-scale output.
Check my math, doing other stuff whilst typing... - Don
The formula for voltage gain in dB is: Voltage Gain (dB) = 20*log10(Vout/Vin) -- it is a fundamental equation. You can re-arrange the equation to get Vout/Vin = 10^(Vgain_in_dB/20) and use 1 V as Vin for reference. Note that is for voltage, Vin, and not power, Pin.Thanks Don, i am sure you are right, can you tell me how you calculated gain factor of 20?
You say: 26 dB of gain is a factor of 10^(26/20) ~ 20 V/V.
In that formula, how did you know to use 20 as the Pin value?