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DIY Purifi Amp builds

mocenigo

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mocenigo

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Hope a kit with neurochrome buffer will be available soon.
It would be a matter of purchasing two 1ET400A boards (and two cable kits), two Neurochrome input buffers, a Hypex SMPS1200A400, and for instance a Ghent case. once the bottom is properly drilled, the rest should be piece of cake (a bit of crimping or of soldering).
 

JimM

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Question on using 1ET400 /fatal signal and Eval1 /fatal signal to control the DC Error on smps1200A400. The way I read the 1ET400 data sheet the /fatal signal will function as a open collector transistor output so the two are wire or'ed together on the FE02A and then pinned out to the various connectors, my question is the /FATAL a logic level i.e. high then low when activated or just a open collector output. or does it need to be pulled high with a resistor when connected to the SMPS DC Error? In reading the SMPS spec sheet it states that Hypex amplifiers use open collector output to drive this pin, which implies the SMPS has a pull up resistor of 1k. And requires either around 10 ma or 13 ma drive capability. Can any one verify if this is the case and all we need to do is connect EVAL1 /fatal to SMPS DC Error. Many thanks:
JimM
 
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Question on using 1ET400 /fatal signal and Eval1 /fatal signal to control the DC Error on smps1200A400. The way I read the 1ET400 data sheet the /fatal signal will function as a open collector transistor output so the two are wire or'ed together on the FE02A and then pinned out to the various connectors, my question is the /FATAL a logic level i.e. high then low when activated or just a open collector output. or does it need to be pulled high with a resistor when connected to the SMPS DC Error? In reading the SMPS spec sheet it states that Hypex amplifiers use open collector output to drive this pin, which implies the SMPS has a pull up resistor of 1k. And requires either around 10 ma or 13 ma drive capability. Can any one verify if this is the case and all we need to do is connect EVAL1 /fatal to SMPS DC Error. Many thanks:
JimM
My Eval1 /fatal signal is connected to DC Error on smps1200A400. I just measured /fatal on EVAL1 J3 and its sitting at about 19.8V with music playing. So there must be a pullup on the Hypex end I think? I also momentarily pulled /fatal to GND with a test lead and the SMPS shuts down and goes into protect mode.
 
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JimM

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Great, thanks I will open up my case and connect the signals up, also I am going to enable the buffer on EVAL1 and lower the gain on the Benchmark DAC, for two reasons, one to see if I can tell any difference in sound quality, and two the gain is a little to high with the DAC at 0 db rather than -10 or -20 db. Right now I am running the volume control around 10:00 to 12:00 o'clock rather than 2 to 3, and I have to be careful when switching sources to keep from over driving the speakers. Will report back if I can tell any difference in sound quality.
JimM
 

mocenigo

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Great, thanks I will open up my case and connect the signals up, also I am going to enable the buffer on EVAL1 and lower the gain on the Benchmark DAC, for two reasons, one to see if I can tell any difference in sound quality, and two the gain is a little to high with the DAC at 0 db rather than -10 or -20 db. Right now I am running the volume control around 10:00 to 12:00 o'clock rather than 2 to 3, and I have to be careful when switching sources to keep from over driving the speakers. Will report back if I can tell any difference in sound quality.
JimM
I would really suggest to use the buffer unless the DAC (or your preamp) is proven capable of driving low impedance loads. Excellent DACs (I am talking of behaviour of noise and distortion relative to the current signal level, not of beating SINAD world records) should perform well also with a volume setting of -30 Db or so – they should still give you 16-18 bits of undistorted resolution and effectively inaudible noise even with 26Db of gain and sensitive speakers downstream. My Soekris DAC1541 does that and I am sure your Benchmark DAC does that at least as well. [Effectively inaudible means: if you hear hiss/crackle/hum whatever only with your ear glued to the transducers, and as soon as you are one of two feet away you hear nothing. in my car there is only a hiss and I must be within inches from the mid/tweeter horn.] OTOH, with the buffer the DAC's (or the preamp's) output stage should be able to drive the amplifier more easily, with better bass response and less distortion.

If the gain is too much and you want to avoid risking to overdrive the loudspeakers when switching sources, you can use inline attenuators. If they are properly done they won't affect sound quality. I used JTS MA-123, and apparently the SHURE are even better. Some people swear by the fixed Rothwells.
 
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When my EVAL1 is powered on, there's a quiet "click" or "snap" sound coming from speakers right before the amp starts to play. (I'm not talking about the relay of the power supply).
AC power is switched fully on/off, I'm not using standby to power off. I have AmpOn and Fatal wires connected. I haven't yet tested if AmpOn is causing this and if the same happens also with the AmpOn wire disconnected and using just backpanel switch. Or is this a normal "feature"?
 

mocenigo

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When my EVAL1 is powered on, there's a quiet "click" or "snap" sound coming from speakers right before the amp starts to play. (I'm not talking about the relay of the power supply).
AC power is switched fully on/off, I'm not using standby to power off. I have AmpOn and Fatal wires connected. I haven't yet tested if AmpOn is causing this and if the same happens also with the AmpOn wire disconnected and using just backpanel switch. Or is this a normal "feature"?
A quiet click is absolutely normal. This happens because the amp has some DC at the output - in the order of a few mV, which is ridiculously low, but audible if your speakers are sufficiently sensitive (I got the impression that Bruno Putzeys listens on bricks, from what he writes).

Also a soft sound at power down is normal, which can sound like an very very short “whoosh”, because when the supply on the gate driver sinks the amp starts doing this sound and that supply will probably lower a bit before the undervoltage protection kicks in and shuts outputs off.
 
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JimB

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Thread Starter #672
A quiet click is absolutely normal. This happens because the amp has some DC at the output - in the order of a few mV, which is ridiculously low, but audible if your speakers are sufficiently sensitive (I got the impression that Bruno Putzeys listens on bricks, from what he writes).

Also a soft sound at power down is normal, which can sound like an very very short “whoosh”, because when the supply on the gate driver sinks the amp starts doing this sound and that supply will probably lower a bit before the undervoltage protection kicks in and shuts outputs off.
Yes, and it should not be a problem, normally.
https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-25#post-336085

@TimoJ, you can check the DC offset level of your channels if you are concerned (a DC voltmeter reading on the output) when you turn it on, with no music playing.
 
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JimB

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Thread Starter #673
... However, I wired the ERROR output of EVAL1 to the DC ERROR input
Would you like to SHOW your connection details for this? It is hidden in the (otherwise very nice) photos. ;)
 
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See if you can increase the signal to noise ratio of the preceding stage
I switched preceding stage from MiniDSP DDRC-88A to Monoprice HTP-1 and enabled EVAL1's buffer again: very little noise, 2-3 inches from the tweeter I can hear only quiet hissing. Major difference to the MiniDSP unit, with buffer enabled I heard it's noise 3-4 feet from the speakers...
 
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When my EVAL1 is powered on, there's a quiet "click" or "snap" sound coming from speakers right before the amp starts to play. (I'm not talking about the relay of the power supply).
AC power is switched fully on/off, I'm not using standby to power off. I have AmpOn and Fatal wires connected. I haven't yet tested if AmpOn is causing this and if the same happens also with the AmpOn wire disconnected and using just backpanel switch. Or is this a normal "feature"?
I have’nt wired the Ampon, and i have’nt plop
 
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Would you like to SHOW your connection details for this? It is hidden in the (otherwise very nice) photos. ;)
J3-3 directly to SMPS dc error J4-10
with a pin disassembled from the Hypex connector insulated with heat-shrink tubing
 

JimM

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I connected /fatal J3-3 to the J4 IDC breakout SMPS DC Error pin-10, seems to work ok. I also played around with buffer, no buffer in EVAL1 and DAC gain, went back to no buffer and 0 db on dac gain, will just have to watch volume level when switching sources. I could tell a difference when the EVAL1 buffer was in and preferred the no buffer the presentation was just clearer.
JimM
 
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JimB

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Thread Starter #680
... I also played around with buffer, no buffer in EVAL1 and DAC gain, went back to no buffer ... I could tell a difference when the EVAL1 buffer was in and preferred the no buffer the presentation was just clearer.
JimM
With the buffer active, could you detect any noise from your speakers?
 

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