Hi people!
I need advice since my electronics knowledge is at beginner level. I would need a line level converter to take signal from low power class d and feed it to high power, differential input class d, in home used. This is to save money, so the solution needs to be cheap. Almost all commercial products are made for car use, which play a little different rules.
I've read about L-pads made of two resistors, which would be fine, but since taking signal from class d and putting it to another class d, I thought maybe I should filter the noise. So do I need a cap and how to wire with the L-pad? Just parallel after it? Which values you'd recommend for all components?
The low power amp has gain of ca. 20 dB. I run into its measurements somewhere, its noise starts to climb after 25kHz. The powerful amp is from Hypex, differential input and 100kOhm input impedance if my memory serves. Not sure if that makes a difference in the end.
I need advice since my electronics knowledge is at beginner level. I would need a line level converter to take signal from low power class d and feed it to high power, differential input class d, in home used. This is to save money, so the solution needs to be cheap. Almost all commercial products are made for car use, which play a little different rules.
I've read about L-pads made of two resistors, which would be fine, but since taking signal from class d and putting it to another class d, I thought maybe I should filter the noise. So do I need a cap and how to wire with the L-pad? Just parallel after it? Which values you'd recommend for all components?
The low power amp has gain of ca. 20 dB. I run into its measurements somewhere, its noise starts to climb after 25kHz. The powerful amp is from Hypex, differential input and 100kOhm input impedance if my memory serves. Not sure if that makes a difference in the end.
You absolutely need to filter out the switching frequency if its close to the other amps switching frequency or you'll have a huge whistle tone.
Some class-D amps have variable settings for oscillator frequency (usually touted as for avoiding AM radio interference). Even so a signal with ultrasonic noise will raise your noise floor I suspect, a good solid multi-pole low-pass filter may be wise in this situation, perhaps with a tunable notch filter.
Some experimentation is probably needed, the solution may or may not be cheap. You might be lucky with the oscillator frequencies being far apart, you may not - you've not given any information to help figure this out.
Also many class-D amps have bridged outputs to complicate matters.
Some class-D amps have variable settings for oscillator frequency (usually touted as for avoiding AM radio interference). Even so a signal with ultrasonic noise will raise your noise floor I suspect, a good solid multi-pole low-pass filter may be wise in this situation, perhaps with a tunable notch filter.
Some experimentation is probably needed, the solution may or may not be cheap. You might be lucky with the oscillator frequencies being far apart, you may not - you've not given any information to help figure this out.
Also many class-D amps have bridged outputs to complicate matters.
Why? Better to bypass the low power class D.
Saving money and Hypex are mutually exclusive?
Can you not connect your source to the Hypex amp?
If required, connect a pot for volume.
Saving money and Hypex are mutually exclusive?
Can you not connect your source to the Hypex amp?
If required, connect a pot for volume.
Thanks for replies.
I was upgrading my system, but run out of money before I could finish 🙂 The Hypex NC400 are earlier acquisition, so not related to saving money.
The low power unit is NAD D 7050 and reason for keeping it is in its digital features (usb in, 4xspdif in, bluetooth, lan for control and dlna, digital crossover). Commercial replacements are 1500€ and up, usually at least 4000€ since dsp would need to be included in the new system. So just using the Hypex is not an option in the current setup, the subs can't be integrated well without a crossover.
ASR has measured both devices. D 7050 has a lot noise, starting right after audible range. Switching at 850 kHz. NC400 is a lot cleaner and switches at 460 kHz.
If you can recommend something reasonably priced that has dsp, 4-channels out, and all the digital features mentioned above, I'm all ears. I'm a software dev and I've built computers, so I believe DIY is an option, cheapest, though not the easiest way. I was thinking of miniDSP SHD, but thats currectly strecthing my budget too far.
Attenuating the speaker output from the D 7050 would allow me to use most of what I got right now. Using smaller miniDSP units, like 2x4 HD at the end of D 7050 analog out would also somewhat solve the problem, but I was hoping of avoiding dsp after volume control (if it makes a difference?). Also it would go obsolete if I upgrade later. So in order to utilize the NC400 while looking for/saving up for new preamp, I would need a new kind of solution.
I was upgrading my system, but run out of money before I could finish 🙂 The Hypex NC400 are earlier acquisition, so not related to saving money.
The low power unit is NAD D 7050 and reason for keeping it is in its digital features (usb in, 4xspdif in, bluetooth, lan for control and dlna, digital crossover). Commercial replacements are 1500€ and up, usually at least 4000€ since dsp would need to be included in the new system. So just using the Hypex is not an option in the current setup, the subs can't be integrated well without a crossover.
ASR has measured both devices. D 7050 has a lot noise, starting right after audible range. Switching at 850 kHz. NC400 is a lot cleaner and switches at 460 kHz.
If you can recommend something reasonably priced that has dsp, 4-channels out, and all the digital features mentioned above, I'm all ears. I'm a software dev and I've built computers, so I believe DIY is an option, cheapest, though not the easiest way. I was thinking of miniDSP SHD, but thats currectly strecthing my budget too far.
Attenuating the speaker output from the D 7050 would allow me to use most of what I got right now. Using smaller miniDSP units, like 2x4 HD at the end of D 7050 analog out would also somewhat solve the problem, but I was hoping of avoiding dsp after volume control (if it makes a difference?). Also it would go obsolete if I upgrade later. So in order to utilize the NC400 while looking for/saving up for new preamp, I would need a new kind of solution.
According to NAD D 7050 manual - 'The AUDIO OUT sockets can be used to drive an additional amplifier.
Use a dual RCA cable to connect AUDIO OUT to the corresponding
analog audio input of compatible devices such as amplifiers,
receivers or other applicable devices. '
Use a dual RCA cable to connect AUDIO OUT to the corresponding
analog audio input of compatible devices such as amplifiers,
receivers or other applicable devices. '
Those line outs are low-passed and the speakers outs are high-passed in my current configuration. I cannot achieve the same effect without considerable monetary input.
Now I begin to see what you wish to achieve.
The amps are fed with a pwm signal so no signal can be taken from there.
Headphone out would probably work without attenuation; however, this tells the unit to disconnect the sub out. It may be possible to hack the unit to avoid this but not by a beginner.
One of the class D experts will hopefully chip in and advise how best to implement a resistive divider & if the amp requires a dummy speaker load to avoid damage - some don't like being operated without speakers.
The amps are fed with a pwm signal so no signal can be taken from there.
Headphone out would probably work without attenuation; however, this tells the unit to disconnect the sub out. It may be possible to hack the unit to avoid this but not by a beginner.
One of the class D experts will hopefully chip in and advise how best to implement a resistive divider & if the amp requires a dummy speaker load to avoid damage - some don't like being operated without speakers.
Okey, thanks. I didn't try the headphone jack yet. I'll give it a shot, but most likely it mutes line out or is not high-passed.
If only the D 7050 had a digital output, I just love it otherwise and the looks too. It saves a lot space on desk, since it can stand vertically.
I would be happy if I could modify the unit to output digital or otherwise, but that may be beyond my skills. I found a service manual from internet with schematics and stuff.
If only the D 7050 had a digital output, I just love it otherwise and the looks too. It saves a lot space on desk, since it can stand vertically.
I would be happy if I could modify the unit to output digital or otherwise, but that may be beyond my skills. I found a service manual from internet with schematics and stuff.
Headphone detection is pins 1&2 on header 8 (or 6&7 on the headphone jack). See diagram 7.HEADPHONE BOARD VM2.1 page 24 of the service manual.
It's a complex piece of kit & the manual is not easy to follow on screen - I have no intention of printing out.
Shorting the above pins would prevent the output relay and sub/pre muting.
Whether it also powers down the headphone out I couldn't say.
It's a complex piece of kit & the manual is not easy to follow on screen - I have no intention of printing out.
Shorting the above pins would prevent the output relay and sub/pre muting.
Whether it also powers down the headphone out I couldn't say.
I just tried headphone out without modifying the unit and it seems to always output full range signal. I have a hunch it's always going to be just that or if it's tied to anything, it's closest to line out at the back, which is low-passed. I could try again after shorting the pins.
There are a few mentions of I2S in the manual, but these cannot be tapped into?
There are a few mentions of I2S in the manual, but these cannot be tapped into?
I'd try posting 'how to safely pad the output of a NAD D 7050' in the class D forum.
Post a link to the schematic to save members a search.
Hopefully this would elicit a knowledgeable response.
Post a link to the schematic to save members a search.
Hopefully this would elicit a knowledgeable response.