"Millett Hybrid" redux: NuHybrid headphone amp, using the Korg Nutube

[HiGHFLYiN9]

I just built the headphone amp. Surprising headroom and power. My favorite build is still the Jonokuchi, but I digress. The nutube is definitely microphonic with a high frequency tone for the first few second after startup or if you touch the tube. Has anyone worked out a mod to subdue the microphonics?

It is inherent in the design. Per Korg: "as the Nutube is a directly-heated type tube, it can be affected by vibrations. Suppressing the microphonic effect can be done more easily than with a conventional vacuum tube, as ‘Nutube’ does not generate heat. We are also planning on offering accessories that can be used to suppress any microphonic effect." There are some various mounting suggestions in Korg's data sheets that can assist with vibrations, as well as mounting the chassis on EAR feet as described earlier in the thread. That's about as good as it's going to get for right now...

 

[silverfishla]

I tried using the Line Out on my amp, and it doesn’t seem to be working at all. Is there something I’m missing? Source to Line In then Line Out to amp. What is supposed to be happening here and does the pot control Line Out intensity or not? I wanted to check out what it does, but I don’t get a signal coming through.

 

[Detectit]

OK after some research on building my next DIY amp. This is going to be next...
Researched some Gilmore amps. But documentation is very cluttered. Maybe one step to far.

This is very well documented just like my finished SSHM. Which i enjoy.

One question. ...as esthetic is very important to me.
Could I raise the Korg tube module from the PCB and just wire it.? So i can mount it somewhere else?
Its not far away from the pcb. I want raise the Korg Module on the enclosure.

 

[ThermalAlchemy]

Wow, this amp kicks ass on my IPhone , my Surface Pro 4, and even my $400+ IFI Black Label DAC AMP. I feel like I dropped the soap in the mans prison shower room after buying the IFI Black Label compared to Pete’s nu-tube AMP. On my un-tube amp I only turn up the volume between 9 and 11 at 1 o’clock it too loud. On the IFI Black Label I need to MAX out the knob to distortion. On my DarkVoice 336 se I only can turn it up 9 o’clock and 11 o’clock max. Can’t wait to build the next one, Pmillett keep them coming.
Can we have a XLR headphone amp next?.

 

[Detectit]

I am sourcing the parts. And I will go for a onboard linear power supply.

This time i want to try those R core transformators.
These come with different voltage outputs.
15v 15v 9v 9v secundairies.
Can I wire 15V and 9V in serie to get 24v?
Or better take 30v and step down on regulator?

And the Volume Pot TKD 2CP 601 is recommended. But wont be a stepped Atennuator be even beter? The price is bit cheaper.

 

[pmillett]

I am sourcing the parts. And I will go for a onboard linear power supply.

This time i want to try those R core transformators.
These come with different voltage outputs.
15v 15v 9v 9v secundairies.
Can I wire 15V and 9V in serie to get 24v?
Or better take 30v and step down on regulator?

And the Volume Pot TKD 2CP 601 is recommended. But wont be a stepped Atennuator be even beter? The price is bit cheaper.

You should be able to wire a 15V and 9V winding together to get 24VAC. Rectified that will get you close to 33V DC. That is uncomfortably lose to the 35V rating on the electrolytic caps. So you should either change the caps to 50V - if you can find some that will fit - or use a voltage regulator on your power supply to drop it to 24V. That would be the best option. Then you could use the two 15V windings in series...

You can use a stepped attenuator, it just won't fit on the PCB.

Pete

 

[pmillett]

OK after some research on building my next DIY amp. This is going to be next...
Researched some Gilmore amps. But documentation is very cluttered. Maybe one step to far.

This is very well documented just like my finished SSHM. Which i enjoy.

One question. ...as esthetic is very important to me.
Could I raise the Korg tube module from the PCB and just wire it.? So i can mount it somewhere else?
Its not far away from the pcb. I want raise the Korg Module on the enclosure.

Sure, you can mount the Nutube a bit off the board. Don't go more than an inch or two or it may pick up noise...

Pete

 

[pmillett]

I tried using the Line Out on my amp, and it doesn’t seem to be working at all. Is there something I’m missing? Source to Line In then Line Out to amp. What is supposed to be happening here and does the pot control Line Out intensity or not? I wanted to check out what it does, but I don’t get a signal coming through.

Does the headphone out work?

The line out is connected to the headphone jack and is only active when the headphones are unplugged. It is the same as the headphone out, with some 150 ohm resistors in series.

Pete

 

[HiGHFLYiN9]

I feel like I dropped the soap in the mans prison shower room after buying the IFI Black Label compared to Pete’s nu-tube AMP.

Lol, that's quite illustrative. Given that Pete's offering his intellectual property completely for free (he doesn't make any money on the PCB sales) and the Korg is offered at a discounted rate with the PCB, it's not surprising it mops the floor with a commercial offering in the same price range. Most of what you pay for with commercial audio is distribution, overhead, marketing, packaging and overly fancy aesthetics.

Can’t wait to build the next one, Pmillett keep them coming. Can we have a XLR headphone amp next?.

Hear hear!

 

[silverfishla]

Does the headphone out work?

The line out is connected to the headphone jack and is only active when the headphones are unplugged. It is the same as the headphone out, with some 150 ohm resistors in series.

Pete

The headphone out does work. I'm going to follow the leads and see if I've got everything wired up and soldered correctly.

 

[Detectit]

You should be able to wire a 15V and 9V winding together to get 24VAC. Rectified that will get you close to 33V DC. That is uncomfortably lose to the 35V rating on the electrolytic caps. So you should either change the caps to 50V - if you can find some that will fit - or use a voltage regulator on your power supply to drop it to 24V. That would be the best option. Then you could use the two 15V windings in series...

You can use a stepped attenuator, it just won't fit on the PCB.

Pete

How much current do i need? 2x15vac is 0,5a output

 

[pmillett]

How much current do i need? 2x15vac is 0,5a output

0.5A is fine.

Pete

 

[Detectit]

The headphone out does work. I'm going to follow the leads and see if I've got everything wired up and soldered correctly.

Does the headphone connector Pins closes when you plug out the plug?

 

[pmillett]

Does the headphone connector Pins closes when you plug out the plug?

Correct. The headphone jack has switch contacts. When there is nothing plugged in, the output is routed to the preamp out. When headphones are plugged in, the preamp out is disconnected.

Pete

 

[silverfishla]

Does the headphone connector Pins closes when you plug out the plug?

I think you are right, I did not install the jack that was in the BOM. It's an open connector.

Correct. The headphone jack has switch contacts. When there is nothing plugged in, the output is routed to the preamp out. When headphones are plugged in, the preamp out is disconnected.
Ahh, I see. Electronics. :/ Haha. Can I make a jumper or switch that can toggle the input to the output? Simpler to just get a closed type jack, I suppose.
Pete

Ahh, I see. Electronics. :/ Haha. Can I make a jumper or switch that can toggle the input to the output? Simpler to just get a closed type jack, I suppose.