professorwiki
New Head-Fier
- Joined
- Dec 19, 2013
- Posts
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Thanks for the heads up. This is my first tube amp, so I appreciate the information. Adjusting the bias doesn't seem too difficult.
Just an FYI, but it's a problem with single-tube amps. To get stereo, single tube amps use one triode of a dual-triode tube for each channel. Trouble is, dual-triode tubes rarely test out equal between the triodes. Some are way off. A manual bias adjustment will allow you to "center" the soundstage with unequal triode output, but if one triode truly has a higher output, the peaks will always sound louder on that channel, even if the background has been centered with the bias adjustment.
It's why you see most tube amplifiers with one tube per channel. Almost all of those tubes are dual-triode tubes, but the circuit ties the two triodes in parallel, effectively averaging the output between the two triodes. This exponentially increases your chance of matching two tubes for the two channels, because all you have to match is the average combined output of the tubes' two triodes.
Thanks for the heads up. This is my first tube amp, so I appreciate the information. Adjusting the bias doesn't seem too difficult.
The Bravo amps are suitable for high impedance and low efficiency headphones only, while the Little Dot 1+ can handle low impedance, high efficiency headphones.
In Put Power | DC24V |
Input Sensitivity | 100mV |
Input Impedance | 100KOhm |
Out-Put Impedance | 20~600 Ohm |
Gain | 30dB |
Frequency response | 10Hz-60KHz +/- 0.25dB |
Signal/Noise Ratio | >90dB |
Dynamic range | 84.6dBA(300 ohm) 89.8dBA(33 ohm) |
THD | 0.016%(300 ohm) 0.45%(33 ohm)I |
MD + Noise: | 0.045(300 ohm) 0.42(33ohm) |
Dimension | 79mm (D) X 130mm (W) X 44mm (H) |
Input | Stereo RCA x1, Stereo 3.5mm x1 |
Output | Stereo 6.35mm x1 |
hey, this is off-topic, but I'm just curious about your guys thoughts on this. I read this on some random forum.
I was wondering how true this is as I compared the specs for both amps & their impedance is about the same:
Bravo V3: Out-Put Impedance: 20~600 Ohm
Little Dot 1+: Suitable Headphone Impedance: 8 - 600 ohms [Note: they do NOT state the actual output impedance]
If someone can answer this question, it would be much appreciated! I was curious b/c the poster claims that the HE-400 won't work well w/ the V3, as the HE400 are low impedance, high efficiency headphones (Impedance: 35 Ohm, Sensitivity: 92.5 DB). Any reason based on the specs that might be true?
Finally, have any of you guys are of the 1/8 rule? aka how amp impedance should be 1/8 of headphone impedance. seems impossible as I haven't found any amps that go down to 4 ohms.
In Put Power DC24V Input Sensitivity 100mV Input Impedance 100KOhm Out-Put Impedance 20~600 Ohm Gain 30dB Frequency response 10Hz-60KHz +/- 0.25dB Signal/Noise Ratio >90dB Dynamic range 84.6dBA(300 ohm) 89.8dBA(33 ohm) THD 0.016%(300 ohm) 0.45%(33 ohm)I MD + Noise: 0.045(300 ohm) 0.42(33ohm) Dimension 79mm (D) X 130mm (W) X 44mm (H) Input Stereo RCA x1, Stereo 3.5mm x1 Output Stereo 6.35mm x1
Frequency Response: 10HZ - 50KHz (-3 dB)
THD+N:
0.2%: 1Vrms @ 1000Hz
0.6%: 3Vrms @ 1000Hz
1.0%: 5Vrms @ 1000Hz
Signal-to-Noise: 92dB
Suitable Headphone Impedance: 8 - 600 ohms
Input Impedance: 50K ohms
Power Output:
150mW @ 300 ohms
300mW @ 120 ohms
800mW @ 32 ohms
User variable gain settings: 6.5x or 3.25x
Power Consumption: 15VA
THe bravo does not have an output impedance of 20-600 ohms lol. Output impedance is a constant
where the little dot uses the term "suitable headphone impedance" the bravo states as "output impedance" why because the english is wrong in teh BRavo spec sheet
also teh Bravo has a SET gain of 30, which makes it a very bad idea to drive high sensitvity headphones with as you have very little volume control. The LD 1+ has adjustable gain
ahhh... very enlightening. so basically every turn of the knob +30 for the bravo tube amp while +X user-set gain on the LD1+.
there aren't any other reasons why I should be worried about my adorable lil bravo amp though if I found no problems with the volume control?
hey, this is off-topic, but I'm just curious about your guys thoughts on this. I read this on some random forum.
The Bravo amps are suitable for high impedance and low efficiency headphones only, while the Little Dot 1+ can handle low impedance, high efficiency headphones.
I was wondering how true this is as I compared the specs for both amps & their impedance is about the same:
Bravo V3: Out-Put Impedance: 20~600 Ohm
Little Dot 1+: Suitable Headphone Impedance: 8 - 600 ohms [Note: they do NOT state the actual output impedance]
If someone can answer this question, it would be much appreciated! I was curious b/c the poster claims that the HE-400 won't work well w/ the V3, as the HE400 are low impedance, high efficiency headphones (Impedance: 35 Ohm, Sensitivity: 92.5 DB). Any reason based on the specs that might be true?
Finally, have any of you guys are of the 1/8 rule? aka how amp impedance should be 1/8 of headphone impedance. seems impossible as I haven't found any amps that go down to 4 ohms.
In Put Power DC24V Input Sensitivity 100mV Input Impedance 100KOhm Out-Put Impedance 20~600 Ohm Gain 30dB Frequency response 10Hz-60KHz +/- 0.25dB Signal/Noise Ratio >90dB Dynamic range 84.6dBA(300 ohm) 89.8dBA(33 ohm) THD 0.016%(300 ohm) 0.45%(33 ohm)I MD + Noise: 0.045(300 ohm) 0.42(33ohm) Dimension 79mm (D) X 130mm (W) X 44mm (H) Input Stereo RCA x1, Stereo 3.5mm x1 Output Stereo 6.35mm x1
Frequency Response: 10HZ - 50KHz (-3 dB)
THD+N:
0.2%: 1Vrms @ 1000Hz
0.6%: 3Vrms @ 1000Hz
1.0%: 5Vrms @ 1000Hz
Signal-to-Noise: 92dB
Suitable Headphone Impedance: 8 - 600 ohms
Input Impedance: 50K ohms
Power Output:
150mW @ 300 ohms
300mW @ 120 ohms
800mW @ 32 ohms
User variable gain settings: 6.5x or 3.25x
Power Consumption: 15VA
1. There's danger in referencing random forum quotes.lol not allowed to mention the forum here, but if you figured it out, you must have some damn good googling skillz b/c I edited to quote
2. There's also nothing in those specs that indicate the amp's output impedance. The Bravo amp is specifying output load impedance, just as the Little Dot does. mmm... ctrl+c the specs. I have no idea what they meanso I'm guess output load impedance is what suitable headphone impedance means & bravo mistyped their **** b/c they're chinese lol.
3. You must be referring to tube amplifiers, because there are many solid state amplifiers with output impedance < 1.
YESSS!!! tubes FTW!
Finally, I believe I stated this elsewhere in this thread, but a simple way to look at amplifier power vs headphone impedance is: for the same power, an amplifier must deliver more voltage than current to a high-impedance headphone, but more current than voltage to a low-impedance headphone. lol... I can't find that any info about amp power on the Bravo V3. those sketchy asians lol. Very helpful knowledge dump!
Efficiency is a separate relationship that defines how much power is needed for a headphone to supply a certain decibel level. Its impedance dictates the ratio of voltage to current that it needs for that power and that can tell you what kind of amp you want to have: one that delivers a lot of current or one that delivers a lot of voltage. k cool, thxs prof! I can understand that. low efficiency = less power for volume level, low impedance = high current, high impedance = high voltage
These are generalities, of course, but tubes can easily deliver high voltage, but not current. Conversely, solid-state can easily deliver current, but not high voltage. It's one reason why you see many low-cost tube amplifiers that are hybrids - tube gain stages (voltage) combined with solid-state buffers (current). There are exceptions, of course. The most expensive amps available can often supply plenty of both. hahaha... aka HE400+tube amp is not the best idea... oooopsyyyy
It's also easy to conclude that portable amps - restricted to batteries - have inherent difficulty with high-impedance loads because those kinds of loads want more voltage than current. portable amps can't handle high-impedance headphones. kk.
Damping factors have risen in interest with headphone amplifiers, but almost all of the talk is missing an important point: what's the headphone's damping properties? It's possible to be over-damped and cause distortion on the output as well. In terms of amps, however, generally speaking tube circuits have high output impedance, whereas solid-state have low output impedance. Again, hybrids are in-between but there are tradeoffs there as well. so in conclusion, tube amps for high impedance voltage-hungry headphones & SS for low impedance current-hungry headphones
Hope that helps ...
Thanks! That was incredibly informative!! I feel like i just attended Intro to Amps 101 heh. Thanks for the brainfood professor So basically, my love of the HE400 & tube amps is kinda a mismatch. mmm... welll, wat can i say, I'm attracted to dysfunctional relationships
please do though in teh future... when you quote some one, do not answer them inside of their quote... it's misleading. Respond to segments of the Quote one at at time, quote his post multiple times if need b but don't asdd you answer in bold inside of his quote. It look as if he is answering his own questions >.> and it leaves me confuzzeled some times :3 I know when you quote me it makes me question my self xD "DID I WRITE THAT o no"
so in conclusion, tube amps for high impedance voltage-hungry headphones & SS for low impedance current-hungry headphones
The headphones I plan to use are 63 ohm headphones. I generally consider low impedance to be 32 and below, and high to be anything in the triple digits, so to me the headphones I am going to use are middle range impedance. Of course this is a completely arbitrary division on my part, but I shouldn't have any problems should I other than the volume knob being a bit sensitive?
If it's just a small hum that's fine. My Fiio does that during silence, but once the music is going I can't hear it. According to the tracking it will be delivered tomorrow, and fortunately the mail comes here around lunch and since I am working at night tomorrow I'll have the afternoon to listen. I'll definitely post what I think here for others considering the amp!