So, I've got it put together and tested the points.
TP1 = 13.4 V
TP2 = 13.89 V
Note: I'm using the left/right side of the power connector (J8) as the ground when testing these two points.
However, I have an issue with the right channel. The left channel seems to be working just fine.
When using SE input, the right channel is inaudible.
When using balanced inputs, the right channel comes through as extremely distorted.
Also, the DC offset in the left channel remains near 0V, even when turning the ALPS pot. But, when testing the right channel, the DC offset fluctuates quickly (to nearly 1V) then quickly settles back down near 0V.
I was all excited as I just received my LM317 from TI today, but what a bummer when I plugged in my cans. lol
TP1 = 13.4 V
TP2 = 13.89 V
Note: I'm using the left/right side of the power connector (J8) as the ground when testing these two points.
However, I have an issue with the right channel. The left channel seems to be working just fine.
When using SE input, the right channel is inaudible.
When using balanced inputs, the right channel comes through as extremely distorted.
Also, the DC offset in the left channel remains near 0V, even when turning the ALPS pot. But, when testing the right channel, the DC offset fluctuates quickly (to nearly 1V) then quickly settles back down near 0V.
I was all excited as I just received my LM317 from TI today, but what a bummer when I plugged in my cans. lol
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I would use the metal bracket on the RCA connector for the ground connection for measurements. I think only pin 3 of the power input connector is connected to ground. Pin 3 is the pin closest to the centre of the board. You can also use pin 2 of the output connector for ground.
The most common cause of a dead channel is a solder bridge or cold solder joint around the two surface mounted ICs or the resistors around them. Another common culprit is an incorrectly connected output. If touching up any suspect solder joints and double-checking the wiring on the output doesn't fix the issue, follow the debugging procedure below.
1) Download a -6 dBFS, 400 Hz test tone of five second duration from: Professional Online Audio Frequency Signal Generator
2) Play the test tone on repeat using a media player. Adjust the volume on the player so you get about 1 V RMS at the output (measure at the RCA connectors).
3) Plug the media player into the HP-2's RCA connectors and select the RCA input.
4) Unplug the volume control
5) You should have 1.0 V RMS on U4, pin 1 and U6, pin 1. You should also have 1.0 V RMS on J1, pin 3 and J1, pin 5.
If this works, switch to the balanced input. Adjust the volume control on the media player for 1.0 V RMS from XLR pin 2 to XLR pin 3. Select the XLR input on the HP-2 and plug the cables in. This should give you 1.0 V on U4, pin 1; U6, pin 1; J1, pin 3; and J1, pin 5.
If you get the correct voltages this far, the issue is in the output stage. In that case, follow the steps below:
6) Connect J1, pin 3 to J1, pin 9 and J1, pin 5 to J1, pin 7. You can do this by soldering on a couple of short wires on the bottom of the board. Do not connect the volume pot.
7) This should give you about 1.8 V on the output of the amp.
Tom
The most common cause of a dead channel is a solder bridge or cold solder joint around the two surface mounted ICs or the resistors around them. Another common culprit is an incorrectly connected output. If touching up any suspect solder joints and double-checking the wiring on the output doesn't fix the issue, follow the debugging procedure below.
1) Download a -6 dBFS, 400 Hz test tone of five second duration from: Professional Online Audio Frequency Signal Generator
2) Play the test tone on repeat using a media player. Adjust the volume on the player so you get about 1 V RMS at the output (measure at the RCA connectors).
3) Plug the media player into the HP-2's RCA connectors and select the RCA input.
4) Unplug the volume control
5) You should have 1.0 V RMS on U4, pin 1 and U6, pin 1. You should also have 1.0 V RMS on J1, pin 3 and J1, pin 5.
If this works, switch to the balanced input. Adjust the volume control on the media player for 1.0 V RMS from XLR pin 2 to XLR pin 3. Select the XLR input on the HP-2 and plug the cables in. This should give you 1.0 V on U4, pin 1; U6, pin 1; J1, pin 3; and J1, pin 5.
If you get the correct voltages this far, the issue is in the output stage. In that case, follow the steps below:
6) Connect J1, pin 3 to J1, pin 9 and J1, pin 5 to J1, pin 7. You can do this by soldering on a couple of short wires on the bottom of the board. Do not connect the volume pot.
7) This should give you about 1.8 V on the output of the amp.
Tom
It's amazing how clean the amp is, yet without being overly "dry" or "analytical".
I've sent it to my friend as a gift. He makes his own music as a hobby, and I figured he could benefit from the balanced input, and a headphone amp that does not impart its own "flavor" for mixing purposes. He's waiting on some 1/4" to XLR cables to connect to his audio interface. Excited to hear his impressions.
Thanks for another great head amp, Tom! My HP-1 has been rock solid for the past couple years.
Side tangent... have you explored class-D at all yet? Would love to build a solid, GaN-based Class D amp for my 2-channel setup.
I've sent it to my friend as a gift. He makes his own music as a hobby, and I figured he could benefit from the balanced input, and a headphone amp that does not impart its own "flavor" for mixing purposes. He's waiting on some 1/4" to XLR cables to connect to his audio interface. Excited to hear his impressions.
Thanks for another great head amp, Tom! My HP-1 has been rock solid for the past couple years.
Side tangent... have you explored class-D at all yet? Would love to build a solid, GaN-based Class D amp for my 2-channel setup.
Good to hear you like the HP-2. I'm curious to hear what your friend has to say about it.
I haven't explored Class D beyond making an input buffer for the Purifi 1ET400A / Hypex NC500. Bruno P. does Class D better than most and holds a patent on how to make Class D work well, so I just defer to him if you want a Class D amp.
Tom
I haven't explored Class D beyond making an input buffer for the Purifi 1ET400A / Hypex NC500. Bruno P. does Class D better than most and holds a patent on how to make Class D work well, so I just defer to him if you want a Class D amp.
Tom
Does the future hold a follow up to the HP-1? I know it's relatively niche for the DIY market -- but I love the "performance at any cost" mentality when you can build it yourself and save some cash that way (and have fun doing so). But, I also get why it may be hard to justify having such a product available from a business perspective.
Still -- I would totally jump on building an amp that supersedes the mighty HP-1.
Still -- I would totally jump on building an amp that supersedes the mighty HP-1.
This is what the future looks like for the Neurochrome HP-1: HPA-1 Headphone Amplifier – Tom Christiansen Audio
The TCA HPA-1 performs better than the HP-1 and costs less. But it's not DIY and never will be.
It's simply not realistic to support a DIY project on the scale of the Neurochrome HP-1.
Tom
The TCA HPA-1 performs better than the HP-1 and costs less. But it's not DIY and never will be.
It's simply not realistic to support a DIY project on the scale of the Neurochrome HP-1.
Tom
Hello, I´m looking for parts for my HPA-2 and there are some on backorder. I´ve searched for some candidates, but I mostly don´t know what I´m doing... can someone help a bit?
Can I interchange Texas Instruments CD40106BE with CD4069UBE?
Kemet EC2-24NU with EC2-24NJ (it has same footprint at least)
Will any Onsemi BC547 work? there are several surnames (BTA is the one on the BOM)
This one.. change the 2n7000 with TN0106N3-G from Microchip technology? The main difference I´ve seen is that it has higher "Rds On - Drain-Source Resistance" from 1.2 to 3 ohm... it´s quite a bit.
And last but not least. there are no OPA 1656 hahaha. Sooo. I have no clue what to do with this one. LM6142/6152? AD648? I wouldn´t mind to pay a bit more here. Led time for the OPA1656 is 8 weeks, maybe the best is wait, I don´t know.
thank you very much. I´ve managed to find substitutes for the rest of the parts that are backordered, some of them with the help of this thread
Can I interchange Texas Instruments CD40106BE with CD4069UBE?
Kemet EC2-24NU with EC2-24NJ (it has same footprint at least)
Will any Onsemi BC547 work? there are several surnames (BTA is the one on the BOM)
This one.. change the 2n7000 with TN0106N3-G from Microchip technology? The main difference I´ve seen is that it has higher "Rds On - Drain-Source Resistance" from 1.2 to 3 ohm... it´s quite a bit.
And last but not least. there are no OPA 1656 hahaha. Sooo. I have no clue what to do with this one. LM6142/6152? AD648? I wouldn´t mind to pay a bit more here. Led time for the OPA1656 is 8 weeks, maybe the best is wait, I don´t know.
thank you very much. I´ve managed to find substitutes for the rest of the parts that are backordered, some of them with the help of this thread
Digikey has the OPA1656ID in stock.
I have an extra LM317LZNS/NOPB I can send your way for free of charge if you'd like (if you live in the USA -- then I can just throw it in an envelope with a stamp haha). PM me your address and I'll send it out.
I have an extra LM317LZNS/NOPB I can send your way for free of charge if you'd like (if you live in the USA -- then I can just throw it in an envelope with a stamp haha). PM me your address and I'll send it out.
Btw -- I'm curious if anyone here is driving Audeze planars with the HP-2?
Specifically, the LCD-X (20 ohm; 103dB/1mW)? Looks like output drops a bit at 20ohm load -- tho, still well over 200mW. I've heard that Audeze cans perform best with amps that can supply plenty of current. No doubt the HP-2 would barely break a sweat, but would be curious to hear experiences from others.
Specifically, the LCD-X (20 ohm; 103dB/1mW)? Looks like output drops a bit at 20ohm load -- tho, still well over 200mW. I've heard that Audeze cans perform best with amps that can supply plenty of current. No doubt the HP-2 would barely break a sweat, but would be curious to hear experiences from others.
Wow. I can't believe the world has actually run out of glue logic. Who would have thought.
TI still has the 40106 in stock, though. They currently have 300k of them... The 4069 will work, but is not ideal. The 40106 has a Schmitt trigger input, thus, will work better in the application.
Yep. That'll work.
Any BC547 will work. I'd go with a B or C grade (so BC547B or BC547C). The higher grades have higher Hfe.
Yep. That'll work. It's just a relay driver. Nothing fancy is needed there.
Cry? Pray? I dunno...
Personally I'd order from Digikey. Alternatively, toss me an email and I'll help out. I have ~400 of them. I over-bought at one point. I'll use them eventually, but I have no concrete plans for them so I can certainly package a few in an ESD bag and ship them.Tom
Thank you both!
In the end I´ve split things between mouser and digi key, and that way I can have everything. Also I´ve found the CD40106BE in Ebay spain for 3 euros! but anyway, it´s just one...
So now it´s a matter of waiting. The pcb board should arrive next week or in a couple max. I will post pics when I get everything.
In the end I´ve split things between mouser and digi key, and that way I can have everything. Also I´ve found the CD40106BE in Ebay spain for 3 euros! but anyway, it´s just one...
So now it´s a matter of waiting. The pcb board should arrive next week or in a couple max. I will post pics when I get everything.
Hello Tom,
Hope you are right. I finally finish my hp-2 build. I have the pcb finished for a long time, but the final build was delay several time... I finish it today and i am happy with result, both aesthetically and sonically. Now i need better headphone, my akg k702 are destroying my ears
Some photos, the last one with my soekris dam1941 and ncore.
Hope you are right. I finally finish my hp-2 build. I have the pcb finished for a long time, but the final build was delay several time... I finish it today and i am happy with result, both aesthetically and sonically. Now i need better headphone, my akg k702 are destroying my ears
Some photos, the last one with my soekris dam1941 and ncore.
