Author Topic: Building my own: "NuHybrid" Headphone Amp  (Read 368 times)

Online dekardy

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Building my own: "NuHybrid" Headphone Amp
« on: September 17, 2017, 11:34:16 PM »
Recently I was lucky enough to get the PCB and Korg Nutube 6P1 from one of our forum members.  Thx Wolla.

Below is a link to this design and build from Pete Millet.
http://www.pmillett.com/nuhybrid.html

He sells the PCB and nutube and provides a bill of material, or BOM for short, that can be sourced from Mouser.  After a day or two trying to find the required parts and alternatives to the ones not available from RS I decided, after reading on AVForums, to contact TRX Electronics.  I sent them the BOM and an hour later received a proforma invoice.  The order was placed and I received the parts the next week.  Kudos to TRX.

I studied the build and placements and decided to tackle it this past weekend.

Apart from the occasional banana plug termination and re-solder here and there this is my second real build with the CMOY being my first.

Two boxes waiting to be assembled,  hmm build


The PCB and Nutube


Parts from Mouser still in the bags.


I installed the resistors, diodes and 8pin sockets.  This isn't to bad...


... but then things started going south a bit from here.
First I installed half the small electrolytic caps incorrectly  :facepalm:.  After removing them and installing them the correct way I think I messed up the track on one of the connections.  Ok let's hope for the best.

Secondly the relay sent by TRX was not the right replacement being to big.  Ok not their fault I should have double checked the order.  Urg do I go to Communica now or wait a few days for an order from RS?  I decided to go to Communica and fortunately they had one for me  :Whoohoo:.

Caps,  bias adjust pots , transistors, voltage regulator, relay and inductor or choke.


Finishing the install by adding the RCAs, volume pot, headphone out, power switch, power LED, op amps and of course the nutube.


After inspecting everything I did the first power on test.  No smoke and a nice bluish-white glow from the nutube.  I adjusted the bias output accordingly and it was time the first sound test...

I'm only getting sound on the right channel?  WTF.  After disconnecting everything I re-checked again.  Is it maybe the one track I messed up.  Perhaps the volume pot.  After looking at the schematic I realized that I stupidly assumed provision was made for a volume pot with a on-off switch witch was not the case.  With a lot of hassle I removed the volume pot, removed the two back legs, insulated them and re-installed the volume pot.  During this "struggle" I definitely messed up more tracks and connections.  :Ooooooh:.  I tried again and now its worse.  The sound is very soft.  Touching the volume makes a buzzing noise and will bring back sound but again only on the right channel.

At this point I felt very disappointing and despondent.  After disconnecting everything I came close to giving up and throw this project in the dustbin :vsad:.  Instead I just left it for a while.

Ok what do I do now.  There is no way to fix the tracks.  Do I buy a new PCB.  Do I recover what I can and try point-to-point?

Point-to-point!!!  (This was also suggested by Chris and Wola, thx)

I grabbed the schematic again and started testing all the connections.  Everything looks fine except for the connections from the input to the volume pot.  One channel's ground is fine but not the other.  Lets bridge between the two.  I also connected the two input using some wire straight from the inputs.


Ok let's try again.

It's working yeah  :Whoohoo:
« Last Edit: September 17, 2017, 11:52:12 PM by dekardy »

Online dekardy

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #1 on: September 17, 2017, 11:47:12 PM »
So what does it sound like?  Well since I just finished it I still need to listen a bid but for a start it quite good.  It's got enough power for my X2s.  The few test tracks I normally use did not miss any detail.

Off the bat I can say that,
The NuHybrid starts to distort slightly in the lower frequencies when really loud, the uDSD not.
It's got alot more power than the uDSD.  Considering that this runs of 24v and the uDSD of 5v I guess that is to be expected.
Sound on the NuHybrid sounds slightly easier to listen to.

Does it sound like a tube amp?  I honestly can't tell you because I don't know what a tube amps should sound like.

There is some microphonic noise when you bump it or plug in headphones.  This seems to be normal.

Towards the bottom of this link you can find information on how to prevent it.
http://korgnutube.com/en/guide/

« Last Edit: September 18, 2017, 12:00:54 AM by dekardy »

Offline Rhino

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #2 on: September 18, 2017, 09:05:40 AM »
If i read correctly, it can be used as an pre amp?
What was the cost of the project?
It does look like a great starter project.
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Online dekardy

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #3 on: September 18, 2017, 09:18:22 AM »
If i read correctly, it can be used as an pre amp?
Yes.  It you don't have headphones plugged in it works as a pre-amp.  One of the reasons I got it.

What was the cost of the project?

I guess your looking in the region of R2k

The PCB and Nutube is $50 + shipping.  I paid R950 for it.
BOM about $71 + shipping.  R900 was the quoted price from TRX including shipping but excluding the enclosure, PSU and Alps volume pot.

It does look like a great starter project.
I enjoyed the built, easy enough if you look past the silly mistakes I made.

Offline vinyljan

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #4 on: September 18, 2017, 12:19:51 PM »
Your caption for the pic with the components in plastic bag reads Mouser, guess that should be TRX  :thinking:.  Asking as I might be getting same in near future.
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Online Samayanaya

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #5 on: September 18, 2017, 12:42:59 PM »
Your caption for the pic with the components in plastic bag reads Mouser, guess that should be TRX  :thinking:.  Asking as I might be getting same in near future.

TRX distributes Mouser parts.

Offline vinyljan

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #6 on: September 18, 2017, 02:26:41 PM »
TRX distributes Mouser parts.

Good to know, thx :thumbs:
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Offline Curlycat

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #7 on: September 18, 2017, 06:49:57 PM »
Congratulations on your build  :thumbs:  Excellent that you got it working.

I enjoyed reading your posts on how you struggled and even got despondent at one stage... reminds me of my projects as well. There's nothing as pleasant as DIY, especially if you struggled a bit first  ;) ... I am not alone.


Online dekardy

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #8 on: September 18, 2017, 07:58:20 PM »
Your caption for the pic with the components in plastic bag reads Mouser, guess that should be TRX  :thinking:.  Asking as I might be getting same in near future.
Good to know, thx :thumbs:
@vinyljan.  Yes TRX is the authorized reseller for Mouser in SA.  The order was placed with TRX but the parts came from Mouser. I'll PM you a bit later with some details.  Also the correct relay to order.

Online dekardy

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #9 on: September 18, 2017, 08:06:09 PM »
Congratulations on your build  :thumbs:  Excellent that you got it working.
I enjoyed reading your posts on how you struggled and even got despondent at one stage... reminds me of my projects as well. There's nothing as pleasant as DIY, especially if you struggled a bit first  ;) ... I am not alone.
Thank you.  I'm enjoying them as I type.  This is final big "piece of the puzzle" or build I have in mind.  The other "pieces", DAC, Speaker AMP and PSU are done.  I'm still contemplating if I want to replace my current PSU with a LPSU.  As it stands I actually don't have an issue with the current PSU.  Then I need to fit everything together but that's for another thread  :shh:

Offline TranSonicX

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Re: Building my own: "NuHybrid" Headphone Amp
« Reply #10 on: September 19, 2017, 03:34:47 PM »
Very nice post.
That is one interesting amp.