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 (NAD D 7050) and feed it to high power, differential input class d (Hypex NC400), in home use. This is to save money, so the solution needs to be cheap. Almost all commercial L-pad products are made for car use, which play a little different rules. Replacing the D 7050 with something else with similar or better digital features is mostly too expensive, but any recommendations will be considered.
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. The D 7050 has noise in abudance, as per ASR measurements, switching at ~850 kHz. The NC400 is a lot cleaner, switching at ~460 kHz. 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?
D 7050 has gain of ca. 20 dB, it should be SE on speaker out. Its noise starts to climb after 25kHz. NC400 has differential input and 100kOhm input impedance if my memory serves. Not sure if that makes a difference in the end. Service manual for D 7050 can be found here. Optionally if digital out can be realized easily, that would be great.
I posted this same earlier on analog forum.
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 (NAD D 7050) and feed it to high power, differential input class d (Hypex NC400), in home use. This is to save money, so the solution needs to be cheap. Almost all commercial L-pad products are made for car use, which play a little different rules. Replacing the D 7050 with something else with similar or better digital features is mostly too expensive, but any recommendations will be considered.
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. The D 7050 has noise in abudance, as per ASR measurements, switching at ~850 kHz. The NC400 is a lot cleaner, switching at ~460 kHz. 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?
D 7050 has gain of ca. 20 dB, it should be SE on speaker out. Its noise starts to climb after 25kHz. NC400 has differential input and 100kOhm input impedance if my memory serves. Not sure if that makes a difference in the end. Service manual for D 7050 can be found here. Optionally if digital out can be realized easily, that would be great.
I posted this same earlier on analog forum.
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Because he has a NAD D 7050 and wishes to use all it's clever features while making use of the higher available power of the Hypex amp. Therefore he wishes to use the NAD as a pre-amplifier by padding the outputs.
The NAD does not have pre-outs (at least not whilst they are configured as sub-outs).
The resistor divider will work (and will reduce any noise pro-rata).
The key question is - does the NAD require a dummy load ie very high power 8 ohm resistor to avoid damage while operating without a speaker connected?
If so, this is an added expense and an inconvenience as it would need to be mounted safely where it can dissipate a lot of waste power.
The NAD does not have pre-outs (at least not whilst they are configured as sub-outs).
The resistor divider will work (and will reduce any noise pro-rata).
The key question is - does the NAD require a dummy load ie very high power 8 ohm resistor to avoid damage while operating without a speaker connected?
If so, this is an added expense and an inconvenience as it would need to be mounted safely where it can dissipate a lot of waste power.
The NAD thingie DOES have 2 nice Signal Out jacks and then they should be used, period.
Youn "should" load the built in amp with current speakers (which I assume are matched to it) and use the higher power added amp to drive beefier ones, then everybody is happy.
Padding the 2 x 50W speaker out offers no benefit (since same program is sent both to Line Out and Power Amp) and has tons of possible problems, the least of them being noise contamination by a Class D amplifier, why on Earth would you do that is way beyond my mind.
Youn "should" load the built in amp with current speakers (which I assume are matched to it) and use the higher power added amp to drive beefier ones, then everybody is happy.
You are correct except - the op is using these outputs for subwoofer duty.
The outputs can be used as pre-out OR sub out using the onboard DSP capability.
Using the NAD to power external amplifiers AND a subwoofer (using the onboard DSP functionality) has been costed out in the design.
I had considered the headphone out jack but this also disables the subwoofer output.
Who'd have thought? It would seem natural to want your room shaking whilst listening on headphones!
The op originally posted in analogue source and got zero response (except my blind stabs in the dark) and has re-posted in this class D thread at my suggestion as (QED) I thought it would get a greater response.
There is a service manual online with full schematics.
The outputs can be used as pre-out OR sub out using the onboard DSP capability.
Using the NAD to power external amplifiers AND a subwoofer (using the onboard DSP functionality) has been costed out in the design.
I had considered the headphone out jack but this also disables the subwoofer output.
Who'd have thought? It would seem natural to want your room shaking whilst listening on headphones!
The op originally posted in analogue source and got zero response (except my blind stabs in the dark) and has re-posted in this class D thread at my suggestion as (QED) I thought it would get a greater response.
There is a service manual online with full schematics.
This is the key here, same program is not sent to both. Line out can be low-passed with internal dsp while power amp gets high-passed.
I could use the line out, but I would need to buy additional gear, which I'm trying to avoid. A few resistors and capacitors are within budget. This was discussed in the earlier thread, that i linked in the first post.
It starts to look like a bad idea to pad the power amp output, maybe i just should save up for a different kind of preamp. Still open to suggestions though.
No, using the outputs of a class D amplifier (probably with floating - !!!) to another amplifiers analog inputs is a plain bad idea. But feel free to do stupid stuff, it keeps the industry going 
The only valid solution is to use the line outputs and forget about using the subwoofers.
BTW you want to connect the symmetrical inputs of a NC400 to a device that only has asymmetric line outputs. Could it be that the NAD just is the wrong device to use in this setup?
The only valid solution is to use the line outputs and forget about using the subwoofers.
BTW you want to connect the symmetrical inputs of a NC400 to a device that only has asymmetric line outputs. Could it be that the NAD just is the wrong device to use in this setup?
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The NC400 has differential inputs - no need to ground the speaker out.
It is not uncommon for active sub-woofers to have a high (speaker) level input for amps without a line/sub out so it is not so stupid to connect to speaker out.
However, maybe the op should follow live sound practice & mic up? (that is a joke).
The alternative is ditch the Hypex & buy some more sensitive speakers (or move into a smaller listening room).
If the op tells what sub-woofer he has, this might assist.
It is not uncommon for active sub-woofers to have a high (speaker) level input for amps without a line/sub out so it is not so stupid to connect to speaker out.
However, maybe the op should follow live sound practice & mic up? (that is a joke).
The alternative is ditch the Hypex & buy some more sensitive speakers (or move into a smaller listening room).
If the op tells what sub-woofer he has, this might assist.
Results are often so so already when class AB amps are used but I am pretty sure it will be mediocre at best when a Class D amp is used.
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Where does he say so?
I do not read minds.
Where? Any direct link?
IF you are using it that way (no mention of that in your earlier posts) then internal power amp signal will NOT be full range, so your extra power amp reamplifying it will be also compromised.
You are NOT solving the problem introduced by using NAD in biamp mode.
Problem #2: IF you are currently using a subwoofer amp matching your current 2 x 50W internal speaker an d current speakers, AND you boost high-passed amp from 50W per channel to 400+400W (even 225+225W) , of course driving more powerful speakers THEN the new system will be completely unbalanced.
Subwoofer amps in general are 2X more powerful (or more) than mid/high ones; after conversion ratio will be inverted, maybe 0.5X to 1 or worse.
You really will listen to Music on that?
basically a rethoric question, because you did NOT describe your full system.
Please do, for any useful answer to be possible.
Maybe there is a reason your question could not be answered in another Forum.
I am a minimalist too, but there is a certain functional minimum you need to meet.
Maybe.
Are they enough? Maybe not.
Again, please describe what you are using or have available. Amps , speakers, maybe other stuff you didn´t mention.
This is a System, so we need the full picture.
A DSP in a box including software is 86 €. You can sell it again, and the total loss is 20 to 40 €
If no eq is required, a simple PLLXO is also a good choice
PLLXO Crossovers
Edit. Actually you can also use this to filter out hf after the resistor attenuation
PLLXO Crossovers
Edit. Actually you can also use this to filter out hf after the resistor attenuation
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More details:
- The NAD serves as preamp for multiple sources (computer, tv, occasional b, etct).
- NAD is currently used to crossover between stereo subs (line out) and main speakers (speaker out).
- The subs are Arendal 1723 subwoofer 1, which have basic plate amp and features, such as rca in, xlr in, xlr passthrough, phase, volume, defeatable low pass filter. The xlr out is unaffected by that low pass.
- Speakers are 8 ohm 86 dB sensitivity.
- Volume matching is done with mic+rew and using volume knob on the subs. Current volume setting is between -6 and -12.
- Perfect system, but too little power for main speakers. Also needs more gain, going above -10 with movies and mains are not exactly very loud yet.
The subs are the most recent addition, I previously used NAD line out --> NC400 --> speakers.
Even more details:
- NC400 can be used with SE source with a simple adapter cable, no problem there. Has greater gain than NAD alone in this configuration.
- I've been thinking of replacing the main speakers, but that's maybe next year. Going for DIY for sure!
- Any upgrade I can think of requires additional ad+da, and replacing NAD would be multi thousand euro operation. A perfect system would go digital as far as possible.
- Padding would introduce less components on the signal path than additional active gear, which possibly is overall better solution for the price.
- I'm a man of the future, but not a moneyman. The current gear has been acquired over long time and partially 2nd hand stuff.
I'll ditch the pad idea and go for dsp or analog crossover plugged into NAD line out, if you all say that's the best idea. Any pointers to reasonably priced gear with reasonable transparency, would be appreciated. That dsp in a box for 89€ sounds like distortion, any links?
PS. I prefer dsp, since that allows easy experimentation on xo frequency, filter slopes, timing, house curve etc.
- The NAD serves as preamp for multiple sources (computer, tv, occasional b, etct).
- NAD is currently used to crossover between stereo subs (line out) and main speakers (speaker out).
- The subs are Arendal 1723 subwoofer 1, which have basic plate amp and features, such as rca in, xlr in, xlr passthrough, phase, volume, defeatable low pass filter. The xlr out is unaffected by that low pass.
- Speakers are 8 ohm 86 dB sensitivity.
- Volume matching is done with mic+rew and using volume knob on the subs. Current volume setting is between -6 and -12.
- Perfect system, but too little power for main speakers. Also needs more gain, going above -10 with movies and mains are not exactly very loud yet.
The subs are the most recent addition, I previously used NAD line out --> NC400 --> speakers.
Even more details:
- NC400 can be used with SE source with a simple adapter cable, no problem there. Has greater gain than NAD alone in this configuration.
- I've been thinking of replacing the main speakers, but that's maybe next year. Going for DIY for sure!
- Any upgrade I can think of requires additional ad+da, and replacing NAD would be multi thousand euro operation. A perfect system would go digital as far as possible.
- Padding would introduce less components on the signal path than additional active gear, which possibly is overall better solution for the price.
- I'm a man of the future, but not a moneyman. The current gear has been acquired over long time and partially 2nd hand stuff.
I'll ditch the pad idea and go for dsp or analog crossover plugged into NAD line out, if you all say that's the best idea. Any pointers to reasonably priced gear with reasonable transparency, would be appreciated. That dsp in a box for 89€ sounds like distortion, any links?
PS. I prefer dsp, since that allows easy experimentation on xo frequency, filter slopes, timing, house curve etc.
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Sounds like a job for minidsp; now all you need to determine is how many channels you can see your system evolving into, and whether future upgradability of DACs will be important.
Cranky old fart rant: I do miss the old days when folks like NAD would include pre-out /main-in signal loops on their products, but in the name of compact size, lower cost and “purist” signal paths, those are harder to find.
Cranky old fart rant: I do miss the old days when folks like NAD would include pre-out /main-in signal loops on their products, but in the name of compact size, lower cost and “purist” signal paths, those are harder to find.
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