So how do you explain these sound stage differences? Or is this again something that can't be measured and at the same time also a clever selling tactic with links to your shop?
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DIY Purifi Amp builds
- Thread starter JimB
- Start date
I don't. I'm only conveying my own subjective experience. I would love to go through the AES archives and do a proper literature review of perceived sound quality vs measured performance. I think that would be insightful. In fact, that's one of the reasons why I became an AES member. If you can recommend any research papers on this topic I'm certainly open to your recommendations. I figured I'd start with Olive & Toole and go from there.
I don't know if it can or cannot be measured (hence the need for the literature review). If it is a clever sales tactic, then it'll be the first time in history that I've had one of those. Should I take your notion of it as a compliment?
I provide more measurements and data for my products than anyone else in the industry, so if you're a hardcore objectivist you should be able to find the data you need on the product pages. If not, you're always welcome to suggest additional measurements. If you do so, I would appreciate it if you also explained why you would like me to add the suggested measurement.
I used to be more of a hardcore objectivist and was somewhat dismissive of subjective experiences as "biased" or "non-scientific". But more recently - I think following one of our exchanges here - I've become more open to the subjective experiences. After all, my customers are humans and they don't live in a science experiment. All of their interactions with the products will be sighted. I think it would be naive to ignore that. Just as I think it would be naive to ignore the measurements. Maybe I'm a professional fence sitter.
I apologize if I spoke too empathically earlier. I'm passionate about audio and my business.
Tom
I can confirm that it is pretty much trivial to add a through hole resistor. I configured the Universal Buffer for +7db (which is a bit too much for me, in fact) and I assume that for the Purifi/Hypex Buffer it will be the same.
OP
- Thread Starter
- #2,304
This is not trivial, physically, on the Purifi buffer. 0db gain by-passes the buffer - no gain to boost there. With the gain stage in-circuit, you get much more, so then you want to reduce it. Given the configuration used, that will mean increasing resistance. The board is already only SMD with little space, so it requires removing and then replacing the key resistor. This was addressed in some detail long ago in this topic, including around here:
https://www.audiosciencereview.com/...iy-purifi-amp-builds.10478/page-8#post-296652
https://www.audiosciencereview.com/...iy-purifi-amp-builds.10478/page-8#post-296784
Yep.
You are correct that configuring the Purifi EVAL1/2 for unity gain is not trivial unless you have the tools to deal with surface mounted components. However, on the Neurochrome Purifi/Hypex Buffer, you can select unity gain by moving a jumper. You can also customize the gain by adding a through-hole resistor (or a 1206 size surface mount one if you prefer that).
Tom
OP
- Thread Starter
- #2,306
Actually, unity on the Purifi is not so tough - just use the provided configuration jumpers to by-pass the buffer! Or, if you want an actual unity gain buffer, you can simply remove R17 (a good sized tip will heat both ends at the same time and it'll slide right off). However, I am not saying I know the stability of that stage with no gain (unity gain compensated?). It was clearly not intended for people to customize easily.
If you choose to bypass the input buffer just beware that the input impedance of the Purifi/Hypex modules is pretty low (3.6-4.4 kΩ differential if memory serves).
Tom
Tom
Yep. And for the NC500, which the Purifi/Hypex Buffer also supports:
"DM input, per input" is a misnomer. It's 1.8 kΩ from each input to ground. That would correspond to 3.6 kΩ, differential.
Tom
"DM input, per input" is a misnomer. It's 1.8 kΩ from each input to ground. That would correspond to 3.6 kΩ, differential.
Tom
OP
- Thread Starter
- #2,310
Ghent is now including their cables with their Purifi case ($250). I think the total for them was a bit more in the past. I don't know how long they have had it there, but they have a link at the top of that page to get a 29 page instruction presentation by a user, Richard Verhart. No excuses not to try it due to uncertainty of what to do (though some assembled models can be lower cost).
I use an RME ADI-2 DAC FS. Love it.
Tom
Tom
Those on the Purifi amp (with appropriate buffer), presumably. At least that's how I interpreted the question.
Tom
Tom
chips666
Active Member
JaapDeventer
Member
- Joined
- Oct 29, 2018
- Messages
- 31
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- 34
Today I gave my Pass Korg NuTube preamp a first try. Placed between Ares dac and Purifi amp. Great sound. Not balanced though.
Alpha Audio released a video on assembling an EVAL-1 amplifier.
https://alpha-audio.net/videocast/workshop-purifi-eigentakt-eval1-power-amplifier/
PS: they did not solder the Speakon connectors though.
https://alpha-audio.net/videocast/workshop-purifi-eigentakt-eval1-power-amplifier/
PS: they did not solder the Speakon connectors though.
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After having read @phoenixdogfan Purifi amplifier plight and sympathizing with the expense of shipping modules back and forth to Europe, I PM'd him and offered to help. I got the amp about 2 weeks ago and have been working with Hypex on it.
Initially I thought that it was a standby signal issue as the power supply would not hold maintain any voltage long enough to do much. After disconnecting the cables to the amp module, found the power supply would stay on. I checked the cabling and it was fine. However, as soon as any load was applied to the AUX power pins, it would shutdown. At this point as the power supply behavior was questionable, I contacted Hypex. Their previous repair was to the AUX power protection circuits and they shared some details with me. As mentioned, the SMPS was still in-warranty and so I was not tempted to do much, but they encouraged me to do some troubleshooting. Here is what I found that I thought might be useful to share...
R92 and R99 were open. These are 1 ohm SM resistors that are part of the SMPS AUX power protection circuit and are mounted on the bottom side of the board. As a quick test, shorted them out and the power supply started to behave normally. I hooked it back up to the amp and did a quick test on my QA401 and things were looking brighter.
I ordered some replacement resistors from Mouser and they arrived earlier this week. I got around to soldering them in and started re-assembling the amp to see if anything caused them to blow. The bad news is I did not find anything; the good news is that it continues to work! I have tested on my QA401 and did a quick listening test and all is well. Am packing it up today and preparing to ship it back to its owner.
Here is a pic of the amp with the LED shining just as @phoenixdogfan was hoping he would get to see someday…
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