[slowpogo]

My 470uf electrolytics are socketed and they test fine. I think I’ll replace the choke, and the following 10uf and diode. Everything beyond the diode was likely protected from negative voltage, right?

It’s always humbling to remember that despite a fair amount of experience, you can still make idiotic mistakes.

 

[RestlessZombi]

My 470uf electrolytics are socketed and they test fine. I think I’ll replace the choke, and the following 10uf and diode. Everything beyond the diode was likely protected from negative voltage, right?

It’s always humbling to remember that despite a fair amount of experience, you can still make idiotic mistakes.

I've just ordered my third PCB after making a few mistakes along the way. Nothing at fault of the creator, but my own lack of concentration. First time i made it fine but wanting to put it in an enclosure i tried to removed the "In" RCA and the solder point came off with it. Still trying to fix the second PCB at the moment, ordered the third PCB to make a proper job of it (plus new parts ). Cap C11 is the issue on the second, solder point on ground came off so i had to "mend" it.. Now all checks out but no glow from the tube and only getting 1.2v on the test points no matter how I adjust it.

Again,i messed up, not the board.

 

[slowpogo]

I replaced a few parts as described above and voila, my Nuhybrid was in business.

I built mostly with the recommended parts, except the capacitors and the pot (TKD). The input 0.1ufs are ClarityCap SA, which are not that expensive ($4 each) but a very clear upgrade over Wimas. For the power section electrolytics I used Panasonic EEW-PS, which seem to be the new champion in terms of very low ESR while still being compact (the ones I'm using are 470uf 80V and still not huge). A mix of Elna Silmic II and Cerafine for the 10uf, except for C13-14 which are Wima film caps. They're big, but they fit fine on the bottom of the board (and would fit on the top too with some creativity). For C3 and C6, I'm using some old Black Gate NX 680uf caps I had from a previous build. They still sound wonderful. I tried a few other types in C3/C6 out of curiosity: Black Gate Std, Elna Silmic and Cerafine, and Nichicon FG.

They all sounded good and I'd be happy to use any of them, with the caveat that the Cerafine had recessed vocals, but was otherwise fantastic for, say, jazz. This might bring out the Black Gate skeptics -- I wouldn't pay the crazy prices they go for on ebay these days, but they were absolutely worth the extra bucks at the original prices when they were still being made, if you were in a "spare no expense" mindset. The NX in particular are very vivid sounding, and it's not just a vague feeling of mojo; I can point to specific things that simply aren't there with the others. They manage to be very dimensional with no lack of detail but also have a certain richness, and the backdrop behind the sound feels "blacker" somehow.

Anyway, I'm really happy with the amp. I just built a WHAMMY and I feel I've got two poles covered: a highly detailed, neutral reference amp (WHAMMY) and a more fun, euphonic type amp (NuHybrid).

 

[JRRJ]

Hi - I'm new here and need help with this amp. I've built a few things, including the MiniMax (love the sound), but am pretty clueless. Here is the problem: no sound of any sort from my NuHybrid, not from the headphone jack, not from the RCAs. The tubes light up, I've biased them at about 11v, checked and re-checked parts locations, volume and jack wiring and other wiring. Because of the absolute silence I am wondering if the relay is functioning. If it's not, could it be the relay itself or some obvious mistake involving it? Sorry, but I haven't figured out how to post pics here. Any ideas are welcome. Thanks.

 

[Alkolor]

Hello JRRJ,

When I start mine up and the relay activates, I can hear a faint hiss and click from it. It takes about 10-12sec on mine since I used a larger C2, and I think the normal capacity C2 has been reported to take about 6sec. Does yours make any noticeable sound? Otherwise, bridging between pins 4 and 5 or 8 and 9 on the relay would bypass it so you could test one channel and see if it is just the relay. These would be the first and second pin from the side by the larger capacitors. Looking at it from the side with the components as pictured on Pete's site, the top two would be 8 and 9 for the right channel, and the bottom two would be 4 and 5 for the left channel.

Good luck with your troubleshooting.

 

[JRRJ]

Hello JRRJ,

When I start mine up and the relay activates, I can hear a faint hiss and click from it. It takes about 10-12sec on mine since I used a larger C2, and I think the normal capacity C2 has been reported to take about 6sec. Does yours make any noticeable sound? Otherwise, bridging between pins 4 and 5 or 8 and 9 on the relay would bypass it so you could test one channel and see if it is just the relay. These would be the first and second pin from the side by the larger capacitors. Looking at it from the side with the components as pictured on Pete's site, the top two would be 8 and 9 for the right channel, and the bottom two would be 4 and 5 for the left channel.

Good luck with your troubleshooting.

Thank you for the suggestion. I first replaced the diodes and the relay (foolish fit of impatience, in the process making a mess of the underside of the board) and the situation did not change. Jumping those pins to bypass the relay as you suggested has yielded audio -- and revealed a new problem -- oscillation on both channels. This is where I have stopped for the night, as frustration and fatigue take over.

 

[Alkolor]

I’d keep looking at the rest of the muting circuit components and their connections/orientations (capacitor, MOSFET, etc.), and check if the circuit is receiving power. Until it’s activating property, it seems likely the issue is in there somewhere. I didn’t think of it before, but with the relay in, it would be creating a ground connection through the nominal relay position when you bridge to bypass. I haven’t dealt with oscillation yet to know if that could be a cause, but I would guess it doesn’t help. You’d need to bridge to connection with the relay removed to prevent that. Unless you happen to remove the relay again, I’d go at the activation problem first though. It seems to be the bigger problem for now.

 

[JRRJ]

Thank you again. I ended up starting from scratch because of the damage I did to the board. And it works, and sounds fantastic.

 

[SanderFI]

I've build the NuHybrid in the last couple of weeks in between job and family Used the stock parts exept the pot, offboard Alps 50k.

It works, nice glow on the tube, voltages within spec and sounds great but... I wonder why it is noisy when not playing music. So i shorted the input to find out if its coming from my source or if its inherent to my build. The noise is still here so i guess it is part of the NuTube? The noise can be described as grey noise. When music starts playing i cannot hear it anymore, it's drowned out bij the music. But still.. is it supposed to have an noticeable noise level?

I'm using a Denon Ah-D7200 headphone with 25ohm impedance. Could the low impedance have anything to do with it? Can i change the gain of the amp?

 

[AddiDub]

I have built this beauty months ago and still have a second set of PCB including NuTube and parts (according to the official BOM) lying around. So if there is someone located in Europe who wants to build this, please contact me. Set of parts will be going for €90,- plus shipping.

Regards, Andreas

 

[gaz2613]

I've build the NuHybrid in the last couple of weeks in between job and family Used the stock parts exept the pot, offboard Alps 50k.

It works, nice glow on the tube, voltages within spec and sounds great but... I wonder why it is noisy when not playing music. So i shorted the input to find out if its coming from my source or if its inherent to my build. The noise is still here so i guess it is part of the NuTube? The noise can be described as grey noise. When music starts playing i cannot hear it anymore, it's drowned out bij the music. But still.. is it supposed to have an noticeable noise level?

I'm using a Denon Ah-D7200 headphone with 25ohm impedance. Could the low impedance have anything to do with it? Can i change the gain of the amp?

Hi you need to check the ground of the Alps pot. If you don't have one, attach a ground wire to the body of the pot to eliminate noise. Also to eliminate noise at either end of the pot on absolute minimum and absolute maximum, you need to attach 100 ohm resistors to the middle pins of the pot. Hope this helps.

 

[stephengee77]

The one I built has a clicking sound and a high pitch hiss. It does play audio, but the noise is still very audible. Does anyone know what the cause could be?

Edit: I have isolated the problem to likely be an induction problem or something similar. When I take the amp out of the chasis and hold up the pcb up in the air, the ringing goes away. When I put anything near the bottom of the pcb, it makes noise again.

 

[ClaudiuS]

Hi Andreas, I am interested in your set. Because I am a newbie I can post only once per day. So my response might take some time.

Regards,
Claudiu.

 

[HumanFly1977]

Hi, I'm very much a novice with electronics, but I successfully built a NuHybrid a few months ago. It had been working great until recently—it seems like the headphone jack (the Neutrik NRJ6HF as per the BOM) has become wonky. I only get audio out of one side now, and the only way I can get audio on both sides is if I pull the headphone plug out so it locks to the middle clip in the jack, but then the audio is mono. I don't even know how to begin troubleshooting this problem. Did the jack fail and need to be replaced? Is it just a bad solder job? Any help would be appreciated—thanks.

 

[HiFan]

HI all,

I'd like to share some experience on this amp. This is my first DIY project, and the first successful one. I then went through a great length to get the most out of this circuit.In the process I gained a lot of experiences, skills, and interests in DIY.

Let's start with my first built. This amp really sounds good and I had a lot of fun. However I think the hiss is quite unbearable once opamps are changed. So I started thinking about how to improve it.



Then I went through a series of builds and settle with this. You can see I got some jump wires linking to something beneath the board. It is a Super Regulator board. This board is a fantasic regulator and can turn the switching PSU to a high performance PSU. You might also noticed that I got a small black block sitting next to HP jack in place of ua78m33cks LDO. That is a tarco TRS DC buck converter.





In the original design, when OPAMPs are changed, background noise would very likely to be strange. I have tried a variety of opamps. Opamps like LT1354, AD8065, etc would produce a constant "wooooo" sound. That's probably a character of the LDO.

With Traco, that "wooooo" goes away but hiss is a tiny bit stronger (depending on the opamps you use). However the benefit is huge here since the range of usable opamps becomes wider. And Traco really runs cool. It is not warm at all after running for a whole day.

To address the hiss Traco introduces, I think 2 things might work: 1) use an opamp whose PSRR is higher (closer to 0), like AD8055 and HA5002; 2) swapping out the 10uf grounding cap with a larger cap, such as ZLH, then bypass with a MLCC.

I think the SuperReg is overkill, if I am to build a new one I won't use it. In Pete's original design, filtering caps for the power section is too small. If you don't want to build a new PSU reguator as I did, at least consider putting in a 1000uF cap in the place of C1 or D1 (in Parallel).

I actually plan to add a few more jump wires to the bottom and put more filtering caps into the output of traco.

This is a really fun project.

[Update] I use jump wire to hook up 4 extra caps to increase the 10uf grounding capacitance to a totally around 370uf (Traco's maximum load capcitance is 470uf). I used a ZLH 120uf, a EPCOS 41858 220uf, a epcos c0g, and a vishay 0.1uf MKP film cap. Now noise floor is really low (AD8055) and barely noticeable with audio-technica LS70 iem. In fact my Ha21 has the same level of hiss when used open frame. If you use less sensitive headphones or put it in a case, I think hiss will be completely gone. I am quite happy.

[Update 2] OPA209 works better to my taste than other opamps I have tried, including SS3601.