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Bravo V2 Headphone Amplifier

Bravo V2 Headphone Amplifier

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I had one of these and it had terrible interference in an office environment, ended up getting the FiiO E10K. I replaced the tube and liked the sound though. The plastic top came in REALLY scratched, makes you wonder about their quality control.

It looks cool, but there's no shielding which is pretty dumb.


public
mine was picking up interference from a fluorescent lamp that was almost directly over my space at work. I found that just moving it a few inches eliminated the buzz. That being said, these are decent amps that deliver good power to your headphones. Just pair it with a decent DAC.
I bought one of these on Amazon so I wouldn't have to wait. It was only $8 more. My question is regarding a DAC. I'm using a Zorloo ZuperDAC that I picked up during the last drop. The question is what is the optimal way to use this combination. This is a setup for work so it did not have to be super high end. I have the volume turned up all the way on the ZuperDAC using my iPhone 6s Plus as the source. I only have to turn the volume nob up not even a quarter on the Bravo to get good volume output to my DT 770 Pro 80 ohm cans. Should the ZuperDAC only be at 1/2 volume since it has an amp also built in. Or should I get a DAC without an amp? I'm new to this stuff. I'm also going to try this out with Massdrop HD6xxx, and Hifiman HE-400i, and HE-560's.
If you like this form factor check out the originals at Garage 1217. They are pricier but also better as they are adjustable for whatever headphones you choose.
misterman14
thanks!
These Bravo amps are great fun but two quick bits of advice to potential buyers: Throw out the stock tube and get something half decent, or even better: spend a little more and get the Bravo Ocean instead; it's really worth it. (And then also throw out the supplied tube and get something better).
I was thinking of building a headphone amp based on a circuit like the one on which the Bravo V2 is based. Being kind of lazy, I just bought this version of the Bravo V2, instead. I'm comparing mine to an original version Objective 2 amp, which I built up from a PCB I got directly from NwAvGuy.

So, what do I think of this Bravo V2?

1) Its output impedance is too high. It loads down trying to drive my Fostex T50RP headphones with 60 ohm impedance. Driving those 'phones, the Bravo gets 'gnashy' sounding. Harsh highs, rubbery bass. It sounds kind of 'electronic.' However, driving my Sennheiser/Massdrop HD6XX 300 ohm headphones, the sound from the amp becomes acceptable. It's still a bit more harsh and electronic sounding than if I use the O2 instead. But at least it sounds on par with a typical PC laptop's headphone output when driving higher impedance headphones. That's a pathetically low bar to clear...

2) I'm not having any noise or channel imbalance problems. Mine seems good.

3) I expected the Bravo to sound mushy and 'tube-y.' Instead it sounds 'harsh,' even when driving high impedance headphones. I haven't tried any different 12AU7 tubes in it, which I will do. But unless the supplied Chinese-made 12AU7 is an utter piece of crap, I don't expect a different version 12AU7 will fundamentally alter the annoying sonic character of this amp.

I figure the amp is worth the cost of its constituent parts. At some point I'll try some of the mods people have suggested. But if you're shopping for a 'keeper' of a headphone amp, ignore this.

I'm still happy with my O2, so if an Objective 2 comes up as a drop again, I'd recommend that. This Bravo V2 doesn't sound anywhere near as good as the O2. Not even close. Sorry.
rongon
I tried a few different tubes and the best ones I came across was this one in my opinion https://www.amazon.com/Electro-Harmonix-12AU7-EH-Vacuum-Tube/dp/B000UMDYYW
it really fixed a lot of the issues I was having with it. I upgraded the caps on my V2 and the highs sounded clearer and it lost whatever rubbery bass it had (even if I put the crappy chinese tube back in). After changing the tube out I've used it for my Grados 225es, K7XX, and my friend's HD 650s and it sounds great on all of them (Admittedly much better on the HD 650s). I'd highly suggest switching out the tube or modifying it though. I've sunk about $150 into my tube and it sounds better than any of my other amps at this point.
This is pretty much just a toy for me. The sound is BAD for K7XX and HE400i (even worse than directly using my cell phone). I don't have 300 or 600 ohm headphones, so I guess my feedback is biased.

I'll probably use this to teach my son what is an AMP. LOL
DareToBe
I have a pair of Fostex T50RP cans that are 60 ohm impedance, and a pair of HD6XX that are 300 ohms. I've played them both through the Bravo V2 I just got. I can tell you that this amp sounds pretty miserable trying to drive low impedance headphones. It gets kind of bright and nasty sounding. It sounds acceptable driving the HD6XX cans, but not as relaxed and clean as my original-version Objective2 amp (built up from the original run of PCBs). I agree, this thing is a toy. Maybe I'll do some experiments on it or something.
DareToBe
Update: I got a DUNU impedance adapter from ebay to add another 75ohm on top of my 35ohm HE400i. Now the sound becomes OK to me.
just received mine last week and tried it once and it had a huge amount of hiss in the background to the point of being UN-listenable especially at low volume. I saw something about burning in the tubes for a different brand but not sure that's what I need to do.
I really like it for work listening, and it's very pretty as well.
crimsontime
What are you using for the DAC? Your MBP?
This vs the xDuoo TA-01 for Hifiman HE-400i.
I have one. I stopped using it. It was so biased to the left side at low volume, I couldn't use it with a lot of my headphones.
What are those extension posts called?
Is this unit somehow different than the one available in Chinese online stores like aliexpress.

Prashu
It's the same.
Has anyone looked into the actual engineering design of this amplifier? I found a schematic for it here: http://bilder.hifi-forum.de/max/415727/bravo-v2-schematic_691080.png
It shows some interesting things, not all of which look particularly 'good.' I don't know if that schematic is accurate, or is representative of the units that are actually shipping.

1) The input potentiometer (volume control) is 100k ohms. That is a common value for vacuum tubes. However, R4 and R5 (grid leak resistors) are only 24k ohms. That means the input impedance is 100k||24k = 19k ohms. That's only a little higher than you'd see from a typical solid state headphone amp. Maybe this is not a problem in this instance. BUT...

2) The input capacitors, C1 and C2 are 1uF (one micro-Farad). That creates an RC high pass filter (HPF), with bass roll-off that is -3dB at 8.4Hz. That means this little amp can only be truly flat (-0.1dB) in the bass at about 80Hz, and probably -1.5dB at 20Hz. That is kind of high, and would probably be audible used with cans that go really low. This thing won't make really deep bass, but this is probably not a problem. People who buy this are probably not looking for that, but rather are looking for that 'warm tube sound.'

3) The LM317 (IC1 and IC2) current sinks in the sources of the output MOSFETs IRF510 (Q1 and Q2) are set to 167mA (0.167A). Just FYI.

4) The plates of the 12AU7 (triode tubes V1A and V1B) are running with very low voltage, only 16VDC. If you look at the characteristics for type 12AU7, you can see that it must be running with practically no grid bias. That would mean the control grid must be drawing at least a little current. When the tube is drawing grid current, its input impedance goes low. The grid's input impedance is in parallel with the grid leak resistance (defined by the volume control with R4 and R5 in parallel), which is already pretty low. Audio sources with low output impedance and the ability to sink some current into that load will be necessary for good sound.

At any rate, I can see that this design would be very, very sensitive to tube characteristics that the tube itself wasn't designed for. Tubes in general are designed to be used with plate voltages of 100VDC and higher (up to 250VDC is normal for the 12AU7). Characteristics at plate voltage of 16VDC are likely to vary a great deal between different 12AU7s. Tube rolling indeed!

This looks like a fun little "tube-ifier", but it doesn't look like a truly high fidelity headphone amplifier. I might pick one up just to play around with, maybe swap out a few parts, play with some minor modifications. Looks like it could be fun. I think I'd change that blue LED for an amber one. I'd want warm colors for a hot little 'tube amp.'

Anyone else with experience with tube amp designs care to take a look at that schematic and comment on it?
rongon
So I bought one. It's as expected. Not exactly hi-fi.

Compared to my Objective 2 amp, this Bravo V2 sounds a lot more aggressive in the upper mids. Low impedance (50 ohm) headphones playing straight from the PC line out sound less bright. But this amp is kind of cute.

This amp does sound better driving high impedance headphones, but still very colored sounding. Its bright and aggressive character remains, just less apparent than when driving low impedance cans.

Incidentally, the output MOSFETs are IRF630, marked as such on the PCB. The schematic I linked to says IRF510. I'm not sure how much difference that would make.

Oh well. Maybe I shouldn't have bothered. I might try some mods to see if I can lower the gain and/or get it to sound more mushy and tube-y. That would be nice for mellowing out the hashy highs from MP3 streams. I can't think of any other use for this thing...
rongon
Um... Right!! What you wrote sounds very good, but you might as well have said, "may I mumble dogfish to the banana patch?" Definitely way over my head :)

Interesting though.

BTW: quote is from Steve Martin