[airil]

Hi,
I was browsing when I found this small amp, targeting at the Bravo V2, anyone has a review to share, please?

2018 Nobsound HiFi Mini Class A 12AU7 Tube Multi-Hybrid Headphone Amplifier Stereo Pre-Amp Little Bear P10
http://s.aliexpress.com/VBZbIZnM?fromSns=Copy to Clipboard

 

[serman005]

I haven't heard this one but another Little Bear product I auditioned was really good. Don't remember the model number--sorry. I also like the Bravo Ocean quite a bit, FWIW. I think it is better a bit than the V2--just my take and YMMV.

 

[airil]

@serman005 thank u!

I have the v2 with psvane tube and quite happy with it being my desktop set. I am thinking if this is superior by much, u know, since we can use a lot more tubes. Heard about Bravo Ocean but never tried.

Guess I just click buy and see later

 

[K31TH3R]

Not sure if you ended up buying one of these, but I did, and it just came today from Amazon and I'm about 6 hours in. I was looking for a decent review of this amp and I didn't find it, only this thread. So here are all my thoughts, equipment configs for testing etc. I'm using at as a pre-amp to add some color to my Pimeta. Hope it helps.

TL;DR: In it's stock form with the Chinese tube, I'd describe it as the definitive cheap basshead tube amp. If you are a basshead, you need this amp in your collection. The lows are something special through this amp. Jazz bass sounds absolutely wicked. As does drum heavy psychadelic/folk rock. The single tube means you won't hear the reverb and resultant inflated soundstage that "balanced" multi-tube amps bring, so if you're looking for that sound, this isn't your amp. The mids and highs are relatively untouched compared to the bass which is colored beautifully. I'm happy to discover this amp really seems to compliment Beyerdynamic drivers, as it removes sibilance to a fair degree and warms up the DT-990's slightly cold midbass without making it muddy. Unfortunately, it also loses some resolution and detail in the highs. I believe this is a fault of the included Shuguang 12AU7 tube, and I have an Electro-Harmonix balanced triode 12AU7 in the mail to determine if I'm correct.

Build/Design
I'm happy with the amps build quality, very happy with the input and output placements. I wanted a tube preamp that had no cords coming from the front, and that's what I got. I was worried with the open design that the components wouldn't feel solid, but I have some very tight RCA connectors, and I had no worries about knocking the RCAs off the PCB. It's larger than it looks in the pictures, and it's also really nice to look at. There is a red LED on the PCB below the tube, but it's not over driven and isn't too bright. The included power supply looks and feels very cheap, is not the same power supply shown in the pictures, but is rated at 24V DC 2amp. And the amp switches between them fine with no pops or unwanted noise. The amp has a soft start feature. There is no sound output for about 15-20 seconds, and there are no clicks/pops/audible anything when the amp begins playing, it fades in nicely. Slight thump and click when powering off, nothing alarming even on full volume.

The amp claims it has no op-amp, and I can't see an op-amp anywhere, and the mosfet heatsinks get VERY hot. It probably wouldn't hurt to have a low speed fan moving air around the components. The tube does get hot, but doesn't seem to get hot enough to be a primary gain stage, so I have absolutely no idea how the "hybrid" part of this amp works, especially without an opamp. Someone else would have to probe the amp to see how much voltage the tube is actually getting, it's not really my area. However, the tube is biased properly, maybe slightly too high, but the plate isn't being overheated.

Configs:
Cans: Cable swapped 3yr old Beyerdynamic DT-990 Pro 250ohm
Primary source: PCI Creative X-Fi Platinum output through front bay headphone amp on max volume (500mw) MK1 w/ upgraded caps on both card and front bay. Playing .flac.
Equipment: X-Fi Front Bay 6.35mm to RCA-> Little Bear P10 RCA out-> Pimeta Desktop (Pimeta Specs: https://www.head-fi.org/threads/fs-pimeta-home-amp.214569/#post-2595692)
Comparison as follows: X-Fi->Yamaha HTR-5240->Pimeta->DT-990 VS. X-Fi->Little Bear->Pimeta->DT-990

50hz-800hz: POWERFUL bass/drums, is just about the only word I could use to describe. By far the high point of this amp. I knew my DT-990's could make bass happen, but this amp makes them SING with low frequencies, and they really sound great together. No muddiness. Just deep, clean, BIG bass.
1000hz-2500hz: Slightly warm. Full. Smooth. Does well to cover up poorly mastered or harsh sounding albums. String plucks sound much thumpier and fun. Trombones sound fantastic. Also compliments older recordings, or high gain and loud albums like Red Hot Chili Peppers or The Prodigy.
2500hz-4000hz: I believe this is where I'm picking up the harmonics of whatever the Shuguang 12AU7 is adding. This range doesn't sound great, it's really lacking detail and sounds flat, there is a slight graininess which sounds unnatural, and almost like compression you'd hear in a VBR 160kb/s MP3.
4000hz-6000hz: More forward/aggressive/fatiguing compared to my more neutral Yamaha. A little bit of graininess that I think falls on the Shuguang tube. Somethings a little off here.
6000hz-8000hz: Notable loss of detail, but an overall reduction of sibilance. You do hear the either loved or hated tube "sparkle" in this range, and I think another tube would perform better here. If you have sibilant cans and don't like messing with EQ, this would do it for you.
8000hz-16000hz: Slightly artificial and distant sounding. Grain rolls off at this point and becomes smoother again. The frequencies are still there, they just aren't as forward as they normally are with the DT-990. You may like what this does for the DT-990, but I personally love the DT-990's detail and this isn't ideal.
16000hz-30000hz: My dog was outside during this review, so, no comment.

I'll report back once I put in the Electro-Harmonix tube on wednesday the 14th if anyone's interested, or if it changes the sound at all.

 

[airil]

Not sure if you ended up buying one of these, but I did, and it just came today from Amazon and I'm about 6 hours in. I was looking for a decent review of this amp and I didn't find it, only this thread. So here are all my thoughts, equipment configs for testing etc. I'm using at as a pre-amp to add some color to my Pimeta. Hope it helps.

TL;DR: In it's stock form with the Chinese tube, I'd describe it as the definitive cheap basshead tube amp. If you are a basshead, you need this amp in your collection. The lows are something special through this amp. Jazz bass sounds absolutely wicked. As does drum heavy psychadelic/folk rock. The single tube means you won't hear the reverb and resultant inflated soundstage that "balanced" multi-tube amps bring, so if you're looking for that sound, this isn't your amp. The mids and highs are relatively untouched compared to the bass which is colored beautifully. I'm happy to discover this amp really seems to compliment Beyerdynamic drivers, as it removes sibilance to a fair degree and warms up the DT-990's slightly cold midbass without making it muddy. Unfortunately, it also loses some resolution and detail in the highs. I believe this is a fault of the included Shuguang 12AU7 tube, and I have an Electro-Harmonix balanced triode 12AU7 in the mail to determine if I'm correct.

Build/Design
I'm happy with the amps build quality, very happy with the input and output placements. I wanted a tube preamp that had no cords coming from the front, and that's what I got. I was worried with the open design that the components wouldn't feel solid, but I have some very tight RCA connectors, and I had no worries about knocking the RCAs off the PCB. It's larger than it looks in the pictures, and it's also really nice to look at. There is a red LED on the PCB below the tube, but it's not over driven and isn't too bright. The included power supply looks and feels very cheap, is not the same power supply shown in the pictures, but is rated at 24V DC 2amp. And the amp switches between them fine with no pops or unwanted noise. The amp has a soft start feature. There is no sound output for about 15-20 seconds, and there are no clicks/pops/audible anything when the amp begins playing, it fades in nicely. Slight thump and click when powering off, nothing alarming even on full volume.

The amp claims it has no op-amp, and I can't see an op-amp anywhere, and the mosfet heatsinks get VERY hot. It probably wouldn't hurt to have a low speed fan moving air around the components. The tube does get hot, but doesn't seem to get hot enough to be a primary gain stage, so I have absolutely no idea how the "hybrid" part of this amp works, especially without an opamp. Someone else would have to probe the amp to see how much voltage the tube is actually getting, it's not really my area. However, the tube is biased properly, maybe slightly too high, but the plate isn't being overheated.

Configs:
Cans: Cable swapped 3yr old Beyerdynamic DT-990 Pro 250ohm
Primary source: PCI Creative X-Fi Platinum output through front bay headphone amp on max volume (500mw) MK1 w/ upgraded caps on both card and front bay. Playing .flac.
Equipment: X-Fi Front Bay 6.35mm to RCA-> Little Bear P10 RCA out-> Pimeta Desktop (Pimeta Specs: https://www.head-fi.org/threads/fs-pimeta-home-amp.214569/#post-2595692)
Comparison as follows: X-Fi->Yamaha HTR-5240->Pimeta->DT-990 VS. X-Fi->Little Bear->Pimeta->DT-990

50hz-800hz: POWERFUL bass/drums, is just about the only word I could use to describe. By far the high point of this amp. I knew my DT-990's could make bass happen, but this amp makes them SING with low frequencies, and they really sound great together. No muddiness. Just deep, clean, BIG bass.
1000hz-2500hz: Slightly warm. Full. Smooth. Does well to cover up poorly mastered or harsh sounding albums. String plucks sound much thumpier and fun. Trombones sound fantastic. Also compliments older recordings, or high gain and loud albums like Red Hot Chili Peppers or The Prodigy.
2500hz-4000hz: I believe this is where I'm picking up the harmonics of whatever the Shuguang 12AU7 is adding. This range doesn't sound great, it's really lacking detail and sounds flat, there is a slight graininess which sounds unnatural, and almost like compression you'd hear in a VBR 160kb/s MP3.
4000hz-6000hz: More forward/aggressive/fatiguing compared to my more neutral Yamaha. A little bit of graininess that I think falls on the Shuguang tube. Somethings a little off here.
6000hz-8000hz: Notable loss of detail, but an overall reduction of sibilance. You do hear the either loved or hated tube "sparkle" in this range, and I think another tube would perform better here. If you have sibilant cans and don't like messing with EQ, this would do it for you.
8000hz-16000hz: Slightly artificial and distant sounding. Grain rolls off at this point and becomes smoother again. The frequencies are still there, they just aren't as forward as they normally are with the DT-990. You may like what this does for the DT-990, but I personally love the DT-990's detail and this isn't ideal.
16000hz-30000hz: My dog was outside during this review, so, no comment.

I'll report back once I put in the Electro-Harmonix tube on wednesday the 14th if anyone's interested, or if it changes the sound at all.

Thanks for the detailed review. I don't really know how to write that long or technical. Having a Dt990 250ohm, and HE4xx, comparing side by side to the audio bravo v2 with same 12au7 tube swap between them (since I think it's Apple to Apple comparison), I decided to put it on the sideline.

The build quality I agree with u, very nice, but it's a bit troublesome to swap tube, I need to remove the top plate.

Cheers

 

[K31TH3R]

Excellent pictures! Thanks! Funny that we both ended up with a P10 with DT-990's, we seem to be the only ones on the internet with that setup, or at least vocal about it. Haha.

Cool to see it next to the bravo, as that was the other pre-amp I was looking at. The Bravo seemed like the safer bet due to all the good reviews and experiences with it. I only went with the P10 because it has RCA connections on the back instead of the side like the bravo.

I'm not 100% sold on this amp. I do really, REALLY like what it does to the low frequencies, but I feel like it's really sacrificing so much in the highs that the lows don't quite make up for it.

Which 12AU7 tube did you end up swapping in? Did you notice a difference in sound with a different tube?

 

[airil]

@K31TH3R lol! What a small world.

I swap with my favorite tube which always been in my Bravo v2, the Psvane Tii A-grade. I have a pair of them, but to be fair to the P10, I ran it for 30hrs on standard tube, then remove the tube on my V2, and put it in the P10.

Despite how increasingly musical, detail, and improving the Soundstage of the V2, what I heard on the P10, is actually towards the bass, a little more, which is against my preferences. I am quite sure though there is a perfect tube for this P10, waiting to be discovered. But I have sold/give my 12au7 tubes to friends and families after I found that psvane tube. So now it's on my sideline, until someone on internet perform a tube roll on this amp. Maybe in 5-6 more years to come, it'll stay there.

The V2, is pretty good for the price and size, it's one of my favorite.

 

[K31TH3R]

I'll let you know what I think of the Electro-Harmonix tube. If it doesn't clean up the highs enough I may be trying the Bravo V2.

I really wanted to figure out how the mosfet tube amps work, and if you're interested in some "light reading," this is a great rundown of how these amps work: https://www.audioxpress.com/article/a-hybrid-valve-mosfet-se-amp-complete-project

One of the unfortunate side effects of this type of amp means that mosfet temperatures will heavily impact both the sound and the longevity of the amp, as well as the tube. Mosfet output current goes down as temperatures go up, so when they're too cool, more current flows to the tube which raises output voltage and degrades the signal. Too hot, and the mosfets will wear out more quickly, and the tube could become under biased which also will impact the sound. The mosfets provide current to the heater, and the tube acts to deliver voltage to the signal. It also means that each channel must have it's own power supply, and the input splits stereo to dual mono. It's.... bizarre..

The amps use the tube in the input stage, and from what I understand, it means that this particular style of amp should be heavily influenced by the type of tube used, more so than designs which incorporate op-amps like the NS-08E. It also means these amps will probably need bias adjustments if you change tubes.

 

[K31TH3R]

@K31TH3R lol! What a small world.

I swap with my favorite tube which always been in my Bravo v2, the Psvane Tii A-grade. I have a pair of them, but to be fair to the P10, I ran it for 30hrs on standard tube, then remove the tube on my V2, and put it in the P10.

Despite how increasingly musical, detail, and improving the Soundstage of the V2, what I heard on the P10, is actually towards the bass, a little more, which is against my preferences. I am quite sure though there is a perfect tube for this P10, waiting to be discovered. But I have sold/give my 12au7 tubes to friends and families after I found that psvane tube. So now it's on my sideline, until someone on internet perform a tube roll on this amp. Maybe in 5-6 more years to come, it'll stay there.

The V2, is pretty good for the price and size, it's one of my favorite.

So an update.... If you haven't, you may want to adjust the bias on your P10. Surprisingly, the tube was biased too cold on mine. During startup of the amp I was having more and more prolonged static and distortion on the left channel that eventually stopped going away. The factory trim setting was 11 o'clock on the left channel, 11:30 on the right. The adjusted bias ended up being 8 o'clock on the left, 10:30 on the right.

After biasing I am VERY happy with how this amp sounds, to the point I no longer feel the need to try the Bravo V2. The adjustment drastically cleaned up the mid-highs, removed ALL the graininess and "compression" sonics, basically all of my complaints I had about the amp are gone, and the warm/colored beefy bass is still there. If there is any improvement from how it sounds with the new EH tube I would be absolutely amazed.

After biasing, my recommendation for this amp has gone from "get it if you're a basshead" to "get it if you want an excellent cheap desk tube amp."

 

[airil]

Thanks @K31TH3R I'll try later, when I am back home and have time.

Also need to read that post you shared. Seems like a good one.

Cheers!

 

[TheCannibal]

I ordered one of these out of curiosity and then found this thread. Created an account just to say hi.
I have a pair of he4xx on the way, but will be testing this amp with a t50rp for the harder to drive side and a pair of AT ad900x

@K31TH3R I saw your amazon review and that is what convinced me to get this over the bravo v2. Thank you for that review and the note about biasing the tube. I have a few different tubes to try out when it shows up, this seems like it will be a very fun little amp to play around with and dial in.

 

[K31TH3R]

I ordered one of these out of curiosity and then found this thread. Created an account just to say hi.
I have a pair of he4xx on the way, but will be testing this amp with a t50rp for the harder to drive side and a pair of AT ad900x

@K31TH3R I saw your amazon review and that is what convinced me to get this over the bravo v2. Thank you for that review and the note about biasing the tube. I have a few different tubes to try out when it shows up, this seems like it will be a very fun little amp to play around with and dial in.

Cool! Glad I helped you out. Interested to hear what you think of it and your opinion on what different tubes do to the sound.

The Electro Harmonix balanced triode 12AU7 tube I ordered showed up bad. I couldn't bias it into sounding good no matter what I tried. Let it burn in for an hour and it never improved no matter the bias setting. I suspect the tube may have been gassed. I sent it back and am waiting for a replacement, so I still haven't had a chance to try out another (working) tube yet. Depending on how different a working EH tube sounds I may try rolling a few more.

 

[TheCannibal]

Cool! Glad I helped you out. Interested to hear what you think of it and your opinion on what different tubes do to the sound.

The Electro Harmonix balanced triode 12AU7 tube I ordered showed up bad. I couldn't bias it into sounding good no matter what I tried. Let it burn in for an hour and it never improved no matter the bias setting. I suspect the tube may have been gassed. I sent it back and am waiting for a replacement, so I still haven't had a chance to try out another (working) tube yet. Depending on how different a working EH tube sounds I may try rolling a few more.

Just got a shipping notification! It should be here by early January...looks like it is on the slow boat. Gives me time to source more tubes I guess?
Patience is not my strongest virtue.

That sucks the tube was no good. I am looking forward to hearing how well this amp does in different configs!

 

[K31TH3R]

Just got a shipping notification! It should be here by early January...looks like it is on the slow boat. Gives me time to source more tubes I guess?
Patience is not my strongest virtue.

That sucks the tube was no good. I am looking forward to hearing how well this amp does in different configs!

Wow, that is most definitely the slow boat. There were 2 left in stock when I ordered mine, so someone must've sniped the last unit before you ordered. The good news is the contact I've had with Douk audio has been good. They were quick to respond to my questions and provided helpful support. So hopefully the long shipping is the only inconvenience you have to deal with.

The replacement Electro Harmonix 12AU7A tube arrived in the mail today, and after some oddities and hiccups getting it biased and burnt in, I'm finally listening to the amp with another tube. It turns out that the unit wants a power cycle and a complete drain of the capacitors, and needs the power cable completely disconnected from the unit before it plays nice with another tube. So it seems the circuit does have some self biasing, and the bias pots are there simply to fine tune the circuits self biasing. Again, I'm not sure if that's correct, as the way this amp works is still largely a mystery to me.

The EH tube definitely changed the sound in many ways. Overall it is an improvement over the Shuguang tube, and the sound changed a lot more than I expected in a "hybrid" tube amp.

1. The sound stage and instrument separation has been the most noticeable change. Very difficult to describe, but to try and put it into words the staging with the Shuguang had a more 2 dimensional sound. There was instrument separation, but it all seemed to be on a flat plane, whereas the EH sounds more like there's stereo separation and verticality as well.
2. Surprisingly the ridiculously nice, full, clean bass has stuck around, I don't notice much of a change in the lows. Still some of the best bass I've heard my DT-990's make.
3. Mids are "punchier," still has the nice mid warmth tube sound, but slightly less metallic and synthetic sound than the Shuguang. More energetic sounding impacts in snares, bongos, string plucking.
4. The harmonic distortion is more difficult to detect in the EH tube, so if you're actually looking to get the "tube sparkle" then the EH may not be the tube you want, because there is less of the signature tube breakup. With this tube, you probably wouldn't realize you're listening to a tube unless you know what to listen for.
5. The highs are much cleaner. The overall sound of the EH is brighter. As someone who loves the sound of the DT-990 I consider this a GOOD thing. Some might consider it fatiguing, but I don't.

After hearing the EH for only a few hours, it has already impressed me enough that I won't be switching back to the Shuguang. But don't get me wrong, I spent a lot of time listening to the Shuguang, and if you never swapped out the stock tube you'd be doing just fine. But I can definitely say it was the limiting factor in this amp, and there are improvements to be made in the sound with other tubes.

 

[TheCannibal]

Amp finally showed up! Took nearly a month but I am thankful it showed up before everything shut down for the holidays, and it gives me a new toy to play with while I'm off!

Initial impression is good overall!
The build quality really surprised me. The knob and switches feel solid considering the price point, and the switches are labeled. The comparability chart for different tubes underneath is a really nice touch too. The unit is bigger than expected, I thought it was going to be smaller. This is not a negative, just an observation.

The sound is pretty good. I'm getting a slight hum that might go away with time or could be the need for biasing. It is faint though and not distracting once anything starts playing.

I am listening on he-4xx's and the amp drives them well. Lots of power out of this amp, I am only at 12 o'clock on the dial for a comfortably loud level. The sound is good, there is decent separation of instruments and the clarity is excellent. I was thinking there would be more low end but I need to compare next to a solid state too see if there's a difference.

I am pleased with the sound and aesthetics of the device. I need to spend more time getting to know it, but I'm excited for this gem of a find.