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DIY Purifi Amp builds
- Thread starter JimB
- Start date
Would highly recommend you use nylock or nylon nuts, or at least threadlock on those nuts. Not great to have one of them fall into a powered circuit.
Good idea, just ordered a bunch of M3 nylon locking nuts.
So I'm finally making some good progress on my build and have most things wired up. Last thing to figure out is standby functionality on the SMPS1200.
I want to use a latching push button on the front to toggle between standby and power on. My understanding is that sending a +12V signal to J5.1 and J5.2 on the SMPS1200 will put the smps and the Purifi amps into standby mode, and interrupting that signal turns everything on.
So I'll need to wire up the front switch to be normally closed, correct? I'll be using a screw down terminal to be able to send +12V to J5.1 and J5.2.
I know that typically an electronic circuit needs to be closed, or a loop if you will. J5.1 and J5.2 only take in +V. So where does the -V go?
Otherwise the amp works, or better said, the amp enabled leds come on.
I want to use a latching push button on the front to toggle between standby and power on. My understanding is that sending a +12V signal to J5.1 and J5.2 on the SMPS1200 will put the smps and the Purifi amps into standby mode, and interrupting that signal turns everything on.
So I'll need to wire up the front switch to be normally closed, correct? I'll be using a screw down terminal to be able to send +12V to J5.1 and J5.2.
I know that typically an electronic circuit needs to be closed, or a loop if you will. J5.1 and J5.2 only take in +V. So where does the -V go?
Otherwise the amp works, or better said, the amp enabled leds come on.
SMPS standby will disconnect power from purify so using amp standby is not necessary.
GND can be taken from J5.5.
As you have a lot of space inside the enclosure, maybe it will be better to use additional relay to cut off the power instead of using SMPS standby? Smps1200a400 takes around 10W in standby mode and it’s quite a lot...
Yes, I'll be adding a 4ch relay board to be able to use 2x 12V triggers + front power button. Still trying to figure out how to wire that up correctly, this will be the most complicated part of this build for me, as I'm a complete noob when it comes to electronics.
Happy to take any advice
Well, I figured out the power switch. Turns on with the power switch now
Hooked up the amp to my speakers and my Yamaha receiver with the RCA > XLR cable I had built myself. Hear this weird loud buzzing sound. I went, ugh, did I screw something up in the build?
Answer is yes, I did, but it was the cables. I must've gotten the wiring wrong? Because after testing the amp with my laptop > audio interface > balanced XLR > amp, it all works fine (and it sounds fine, but it's getting late so no serious testing yet).
Will need to figure out what I did wrong with my cables. I followed this schematic:
Maybe wires are shorting each other, no idea yet.
Hooked up the amp to my speakers and my Yamaha receiver with the RCA > XLR cable I had built myself. Hear this weird loud buzzing sound. I went, ugh, did I screw something up in the build?
Answer is yes, I did, but it was the cables. I must've gotten the wiring wrong? Because after testing the amp with my laptop > audio interface > balanced XLR > amp, it all works fine (and it sounds fine, but it's getting late so no serious testing yet).
Will need to figure out what I did wrong with my cables. I followed this schematic:
Maybe wires are shorting each other, no idea yet.
Shield and black need to be shorted together on rca side.
They do? I thought I didn't need to connect shield to anything on the RCA side per that schematic.
Alright, I'll fix those cables tomorrow. Thanks!
D
Deleted member 65
Guest
Finally finished my project!
It took a while to collect all parts and assemble the amp as they were ordered from many different places.
Some key info:
Both power amp modules and smps are screwed to the bottom plate with additional layer of thermal paste in between. SMPS has also thermal paste layer between front panel.
Additional shielding of EVAL1 was done from sanded steel (parts taken from another, smaller DYI enclosure).
All "key" mounting points are cleaned of paint layer providing GND continuity.
Momentary switch is designed for 12V (with built-in resistor). Initially I wanted to power it with J3.2 "READY" signal but there is no voltage for some reason. Temporarily I've taken 5V from J3.4 pin which is 5V/20mA. Power consumption of button's LED is 1mA in that scenario and it is not too bright. As few more users reported here they also haven't "high level" voltage on J3.4 I've asked Purifi for solution and waiting for response.
Everything is working like a charm and now I'll have more time to perform some deep comparison tests with Tannoy XT8F speakers (my old amp is NAD C356BEE).
It took a while to collect all parts and assemble the amp as they were ordered from many different places.
Some key info:
- Enclosure is Galaxy GX288 based
- I modified CNC drawings and enlarged recess area to provide enough space for EVAL1 PCB
- "AMPON/AMP Enable" and "FATAL/DC Error" connected to SMPS (S1 swicth removed)
- Standby mode realized via additional smps and 10A bi-stable relay (power consumption ~0.1W)
- Thermal paste used for additional heat dissipation
- Additional steel shielding for EVAL1 board
- Weight 3527g
- Total cost: ~1200 EUR including VAT and all additional necessary parts (EU)
Both power amp modules and smps are screwed to the bottom plate with additional layer of thermal paste in between. SMPS has also thermal paste layer between front panel.
Additional shielding of EVAL1 was done from sanded steel (parts taken from another, smaller DYI enclosure).
All "key" mounting points are cleaned of paint layer providing GND continuity.
Momentary switch is designed for 12V (with built-in resistor). Initially I wanted to power it with J3.2 "READY" signal but there is no voltage for some reason. Temporarily I've taken 5V from J3.4 pin which is 5V/20mA. Power consumption of button's LED is 1mA in that scenario and it is not too bright. As few more users reported here they also haven't "high level" voltage on J3.4 I've asked Purifi for solution and waiting for response.
Everything is working like a charm and now I'll have more time to perform some deep comparison tests with Tannoy XT8F speakers (my old amp is NAD C356BEE).
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It has 2 47 K resistors at the input. I believe the circuit diagram is posted somewhere in this thread. So unless they have changed it recently.Hmm I've got different response from Purifi...
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Congrats! Very nice build and finish. If I had moved forward with my DIY project it would have looked exactly like that, if my skills allowed.Finally finished my project!
Silly me, I didn't post my measurements with my previous post...
That means they indeed changed the circuit. I'm wondering what was the reason for that change and how it can affect measurements (except potential issues with preamplifiers with high output impedance).
Interesting.
Measurements should improve since they are noise dominated and noise will decrease with this change. Wondering if they also made changes in the gain stage to also decrease the noise.
Can you post closeup pictures of EVAL1 board's preamp section? I'm interested if they just changed R14/R19 values or also something else.
It's best what I have for now. Pictures are low quality as this area was not in "main interest" when picture was taken
I can take better photos toady evening.
Looks like the other resistors are same as before. R14/R19 are now 5.1K, before 47K. This will reduce/remove noise when there is no input connected. I may change those, I'm going to change gain with R17, so I'll do those at the same time.It's best what I have for now. Pictures are low quality as this area was not in "main interest" when picture was taken
I can take better photos toady evening.
