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Universal Buffer achieving -140 dBc (0.00001 %) THD

not sure I understand

Hi,

new here :) have few stupid-never-stupid questions, hope you can advise

I plan out new car audio system that will be based on custom made DSP that has pseudo balanced output that than runs into "Volume regulator - РГ Никитина http://forum.vegalab.ru/showthread.php?t=48665&page=200&"

Than those output goes direct solder to the amplifier, which I'm trying to decide between NC400 or new Purifi.

Amps are powered by ICF0719V1xC Murata that converts 1000w 12v into 53v with proper galvanic isolation. DSP + Volume regulators are powered from another PCU also Galvanicaly isolated from the car 12v rail.

My question what does PURIFI 1ET400A / HYPEX NC500 INPUT BUFFER do?
From my understanding it is needed only if:
- source output is not balanced/symetrical
- there is is a great cable length between source and the amp

is that correct? in my case would input buffer be needed? (I have no idea what input buffer is or what it does lol)
 
The issue with the Purifi 1ET400A and Hypex NC500 (possibly other Hypex as well) is that they have low input impedance. So you need to provide a source that can drive that cleanly. Both the Purifi/Hypex Buffer and the Universal Buffer will do this. Most sources or opamps will not.

The advantage of the Purifi/Hypex Buffer is that it has all the connections for the 1ET400A/NC500 and is set for 13.2 dB gain, which gets you to a total gain of 26 dB when used with those amp modules. It's as close to a plug-n-play solution as you'll get.

BTW: It looks like those Murata DC/DC converters generate a single voltage. You'll need two of them with their outputs in series to get the split supply needed for the Hypex/Purifi.

Tom
 
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thanks for reply!

yes I plan on using Purify buffer as nothing beats it according to the tests so far.

ICF0719V1xC Murata provides 1000w 53v DC on out put + and -, I'm not sure what you mean by - You'll need two of them with their outputs in series to get the split supply needed for the Hypex/Purifi. (never heard the term split supply, and never expected that PSUs can be connected in Series)

Wouldn't connecting in series give 2x the voltage (106v, that is what happens with batteries? and 1000w should be enough to supply without need for 2 in parallel - there is a version of this dc-dc that can have 2 in parallel giving 1800w)
 
The issue with the Purifi 1ET400A and Hypex NC500 (possibly other Hypex as well) is that they have low input impedance. So you need to provide a source that can drive that cleanly. Both the Purifi/Hypex Buffer and the Universal Buffer will do this. Most sources or opamps will not.

The advantage of the Purifi/Hypex Buffer is that it has all the connections for the 1ET400A/NC500 and is set for 13.2 dB gain, which gets you to a total gain of 26 dB when used with those amp modules. It's as close to a plug-n-play solution as you'll get.

BTW: It looks like those Murata DC/DC converters generate a single voltage. You'll need two of them with their outputs in series to get the split supply needed for the Hypex/Purifi.

Tom

what is wrong with running 3 pairs of those from one Murata - it gives 1000w, when one amp will be driving a 30w 4ohm speaker up to 200w 10inch sub
- I do not plan to use 7 muratas to drive 7 chanels, that should be unnecessary.

If it comes down to mid bass / subwoofer channel "Stealling" all the power leaving 4 Tweeter and midrange amps sucking dry, I will add a battery capable of delivering 1500w = 35 amps at 50v (like 12s1p 21700) to provide a buffer so to speak (my worry in that case is that BMS will be controlling charging of the battery essentially from murata PSU and it may introduce undesired noise on otherwise perfectly clean power rail for Audio system
 
You need plus, minus and ground. I.e. 3 wires. Your murata only has two. Connecting the positive of one to negative of the other gives you the three wires you need. Better make sure to understand this piece, and indeed, how to safely handle those 100V.
It's not rocket science, but you have enough tension to kill a person and enough power to burn your car there...
 
I’m sorry but I would like to disagree.
- human can handle okey 3500w (220v * 16amp is common household in Eu), though it is the amps that kill, not the voltage, but 19.8amps that murata can put out won’t kill you :D well me.

- second of all ground in DC circuite means simply the lowest potential in a circuite (a battery minus for example) so here on Galvanically isolated power supply grounding would be done to the negative tab (just like a battery), unless circuit has both positive and negative supplies. Am I wrong? Or does Eval1 have posits and negative supply circuite?? (I don’t think that is what Tomchr meant)

digging in the connection diagrams, it seems like there are two rails on Eval1
- main + and common ground - (25-70v)
- Vdr + and common ground - (13.6v to 16.5v)
- ground connected directly with - of main and - of Vdr (common ground)

So it seems like I will need to run Murata to main voltage and than run non isolated 15v dc-dc from murata output to the Eval1
 
I think that configuration common ground would no be interrupted, but also no ground loops would be present I believe.

Please correct me if I’m wrong. I’m no electrical engineer, just have been building drone for 10 years and fair bit of high end car audio installations / consulting, but seems like implementation of those will require me consulting lol (nice mix of diy drone building and building a audio system :) )
 
Sorry to say yoodog, but you got that wrong on most points... . The 16amps is not there to save your life but to prevent setting your house on fire. Ground fault circuit breakers that are intended to protect your life will switch of the circuit at 30mA differential current or there around.

Search around a bit more. Typical car amps applications will indeed have common ground and minus at the same level. Not here...
 
House fuses are 16 amps if you stick your fingers Into the plug up to 16 amps will pass, fuse will not click right away because your body acts as resistance , no different to plugging in a lamp bulb - I have been shocked daily at the age of 5-6y o as my lamp in the room had naked contact 😁😁 it won’t kill you and won’t even trigger the fuse because resistance of the body is not high enough.

That’s off topic let’s stop it.

GND - all common it seem

This amplifier has common gnd with negative a coding to the diagrams. Feel free to show me why I’m wrong if so. See the diagram below

Here are the power inputs from the spec sheet
±25V to ±65V (VP)
15V (VDR)
±18V (VUNREG)

Power connection
- It looks like power actually has positive and negative supply!? Never worked with DC pcb that would require positive and negative supply feeds
—— yes confirmed found that being mentioned in the manual🙈 thank you Tomchr for setting me on the right path. Will have to get 2 of those murata - btw they are insanely clean PSU! I have had one on the bench for about 3 month running different tests, and I can not imagine anything being AIO psu in that size with true 1050w and that clean 🤙

Could any one (Tomchr seems like you understand topic well and better than I do) draw a power diagram for Eval1?
- It seems like beside two Muratas due to Positive and Negative supply needed
- I will also need 18v for something and 15v for gate drive (GaN tech is lovely, but implementation is more made for OEM than DIY. Though, I’m great-full that they even left DIY option for us 😊🤝)

Cheers
 

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By all means, if you have anything interesting to say on the topic "how to supply Purifi", and specially from 11-15v dc network, my ears (my eyes in this case) are all yours :)

So far only Tomchr has left a informative comment, which resulted in my researching and discovering more about how it all fits together. I would love to hear other people to share their experience in making custom supply for Eval1 - every one can by ready made solution when it exists, but I don't have that luxury, so I have to figure our how to do it (hope I came to the right place to seek help:magnet:)
 
I see now what you Tomchr meant and what would be the product of two PSU in series.

PSU1 + to +VP, - to GND
PSU2 + to GND, - to -VP

That’s what is called dual polarity power supply. No the question for me is how to implement output filter on negative polarity filter. Seems like Polarized low esr capacitors will have +leg on PSU2 - to -VP line, and -leg on PSU + to GND trace.:eek:

That dual polarity supply is really trippy :) I would appreciate if some one could confirm or correct me if I got it wrong (again sorry dual supply is new to me)
 

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oh dam ... Looks like I knocked on a wrong door :) Just saw a good discussion with good amount of technical knowledge and completely missed it was on a different product.. My bad! Thank you though Tomchr for setting me on the right path - research and learning :D
- I have figures the Positive negative supply, only two questions unresolved now
--- how to implement proper filtering
--- MAIN question: how to run positive supply VDR that is required to have its negative on -VP (which is the hot line :D)

But will have to move my questions to a proper discussion place :) Thank you all
 
oh dam ... Looks like I knocked on a wrong door :) Just saw a good discussion with good amount of technical knowledge and completely missed it was on a different product.. My bad! Thank you though Tomchr for setting me on the right path - research and learning :D
- I have figures the Positive negative supply, only two questions unresolved now
--- how to implement proper filtering
--- MAIN question: how to run positive supply VDR that is required to have its negative on -VP (which is the hot line :D)

But will have to move my questions to a proper discussion place :) Thank you all

You knocked on the right door but asked for help on the "wrong product", as TomChr has designed his own Purifi / Hypex input buffer Purifi 1ET400A / Hypex NC500 Input Buffer – Neurochrome

You can find the forum thread here: Purifi 1ET400A / Hypex NC500 Input Buffer
 
Hi Tom, thanks a bunch for your recent ultimate preamp guide! I ordered a universal buffer and just read the design documentation. I'm considering building the last topology in the preamp guide, with two input selectors, then a 4 channel volume put, then the ultimate buffer configured for balanced inputs and outputs.


All of my current sources are still single ended however. I'm building this preamp project to be future proof and wouldn't ever need more than 3 inputs. I'd like to keep things simple and just limit myself to 4 pairs of XLR connectors on the chassis, 3 pairs for 3 inputs and 1 pair for the output.


Would this setup allow me to use single ended sources connected with the pseudo-differential cables? Or will this screw things up for example with the voltage sensing in the balanced stage of the universal buffer, as the sources won't be true balanced sources in the beginning?
 
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