Page 5 of 6

Re: was HYPEX amps cheap surround system

Posted: Tue Apr 16, 2019 5:02 am
by mediatechnology
I have some Hypex nCore modues on my bench right now that are in a client's bass amp.

Do you see about 1V P-P of residual carrier on the output?

Re: was HYPEX amps cheap surround system

Posted: Tue Apr 16, 2019 7:20 am
by billshurv
Sounds about right if its at a few hundred kHz

https://www.stereophile.com/content/aud ... asurements for example.

Re: was HYPEX amps cheap surround system

Posted: Tue Apr 16, 2019 9:56 am
by JR.
mediatechnology wrote: Tue Apr 16, 2019 5:02 am I have some Hypex nCore modues on my bench right now that are in a client's bass amp.

Do you see about 1V P-P of residual carrier on the output?
Hypex FAQ wrote: 2 Q: I hooked up my UcD to an oscilloscope and I see some HF sine wave at about 400 kHz. Is this normal?

A: Yes. The 400kHz signal you see at the output of the amplifier is the residue of the switching nature of class D amplifiers. This is completely normal and does no harm. For more information please refer to our EMI application note.
Sorry no I have not put scope to the output, but the HYPEX class D is different from typical class d amps. Bruno connects NF to the very output and uses the natural lag of the switching stages and simple LPF to cause it to alternate, most class D amps take feedback from the nominal output before running through a big honking LP output filter that can introduce impedance changes and other stuff in the audio band.

https://www.hypex.nl/img/upload/doc/an_ ... nd_EMI.pdf Here is the emi note written by Bruno himself.
====
I am getting closer to final assembly on my new surround sound system, but taking my time (measure three times cut once).

I am adding 10k attenuator trim pots to each input for balance trim while the different Hypex modules in Ucd series use a fixed 26dB gain.

The hypex amp modules have a 5V DC output so I could actually power my digital decoder from one of the amp modules but choose not to, since I will continue looking to upgrade that... Note: The new cheap chinese 5.1 decoder is significantly different from the first one. If I leave the TV monitor speaker on with the surround playing I used to get a short combing between center speaker and TV speakers (less than 2 feet away). Now there is clearly a few tens of mSec more delay inside the decoder, not sure what this means if anything, but seems to work better than the old (cheap) one.

I still need to strip the relays off the output board and sort out the wiring.

JR

PS: I had a little drama trying to grok the pinning on the 22pin audio input connector, and figured it out from following the traces on the PCB... today looking at the data sheet I notice they label both pins 1 and pin 2... duh.

Re: was HYPEX amps cheap surround system

Posted: Sun May 12, 2019 7:31 pm
by JR.
Ran out of things to double check, and guessed right on a couple.... fired it up and now making good sounds and no smoke.

I will check it out further tomorrow for now I'm watching movies.

JR

PS: I miss the meters on my old cheap amps.

Re: was HYPEX amps cheap surround system

Posted: Sun May 12, 2019 8:16 pm
by mediatechnology
Nice!

So what kind of meters did the old amp have?

Re: was HYPEX amps cheap surround system

Posted: Sun May 12, 2019 11:39 pm
by JR.
mediatechnology wrote: Sun May 12, 2019 8:16 pm Nice!

So what kind of meters did the old amp have?
three separate stereo amps,,, lots of LED meters.

I need to see what I end up with for a front end.. the new (cheap) decoder is way better than the old one but still can get stupid and lose sync requiring a power down/up reset.

New amp sounds different but I haven't put my finger on it yet... nothing wrong, so maybe good for a change. :lol:

JR

[edit- using a variant on the multiplex LEDs in my drum tuner (3x12) I could make a 6x10 LED meters with that one 16 line latch/driver and 6 high side mosfets. That would be a lot of LEDs but not much of anything else. The hypex has a 5V@ 100mA supply available so I can easily power the meter and maybe even a few opamps.. or just use it as is. :roll: /edit]

[edit2] after a second night of watching movies without meters, I miss them less and less. :lol: I was going to dig in and check some more, but sounds too good to mess with for now, maybe next weekend. [/edit]

Re: was HYPEX amps cheap surround system

Posted: Thu May 23, 2019 10:29 am
by JR.
The first pass set up is working so good I haven't been motivated to go back and kick the tires.

One observation, the master volume control on a rotary encoder apparently resets to some nominal volume every time it powers up. I have been turning it up a few dB almost every night which should be way past full scale by now if it didn't reset itself back down every day.

If I were to add circuitry, like meters, I might be tempted to actively balance the audio output from the cheap 5V digital decoder. +6dB of gain, and more level/headroom, would probably be about perfect.

For now I will keep enjoying it without meters and extra complexity. I even entertained the possibility of using DPOTs to make a comprehensive balance trim with master volume but was rescued by this new improved cheap digital surround encoder with master volume.

JR

Re: was HYPEX amps cheap surround system

Posted: Sun May 26, 2019 9:31 am
by JR.
My surround system digital 5.1 decoder screwed up last night (first time in a while). Rather than use the Bangalore reset (power down and up again) I tried switching between 2.1 and 5.1 mode... It started working more correctly in 2.1 and fully correct in 5.1 mode, so my earlier theory that it was inadvertently slipping into 2.1 mode is busted. :lol:

I have seen similar behavior from my first cheap surround decoder too... Presumably different brands, but probably one design everybody steals from each other over there. :roll:

JR

Re: was HYPEX amps cheap surround system

Posted: Mon May 27, 2019 9:28 am
by JR.
I am now looking for common elements between first and second surround systems with similar symptom. Perhaps there is something weird about the digital data stream coming from the direct TV receiver, or the optical cable. I expect the optical cable to either work or not. When this works it seems fine.

I was going to try running coax to see if it is more stable, but that introduces hum into my floating amp. I prefer it without hum, so unwilling to listen to hum for weeks just to test this.

I could refine my amp grounding and tie the digital box to the hypex PS ground. In fact I could power the decoder from the Hypex 5V supply but I am still not ready to make the cheap decoder permanent...

JR

Re: was HYPEX amps cheap surround system

Posted: Mon May 27, 2019 10:13 am
by mediatechnology
Kinda OT WRT loss of sync/framing but...

In how many places is the Direct TV grounded?
Does it have a three wire cord?
Is the dish mount or RF cable lightning arrestor bonded to a different potential?

Curious about where the loop current(s) are coming from.
I've never had Direct TV.
Seems like it would have both a third wire ground and a ground for the lightning arrestor.