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Question about tube amps (now with review of Bravo V3 ) - Page 2

post #16 of 32
Thread Starter 

Thanks for the heads up. This is my first tube amp, so I appreciate the information. Adjusting the bias doesn't seem too difficult. 

post #17 of 32
Quote:
Originally Posted by tomb View Post
 

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.

 

 

Quote:
Originally Posted by professorwiki View Post
 

Thanks for the heads up. This is my first tube amp, so I appreciate the information. Adjusting the bias doesn't seem too difficult. 

Very good point 

post #18 of 32

hey, this is off-topic, but I'm just curious about your guys thoughts on this. I read this on some random forum.

Quote:
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.

 

Bravo V3 full specs (Click to show)
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

 

Little Dot 1 Full Specs (Click to show)
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

Edited by money4me247 - 12/21/13 at 7:54am
post #19 of 32
Quote:
Originally Posted by money4me247 View Post
 

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.

 

Bravo V3 full specs (Click to show)
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

 

Little Dot 1 Full Specs (Click to show)
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 

post #20 of 32
Quote:
Originally Posted by Mshenay View Post
 

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?

post #21 of 32
Quote:
Originally Posted by money4me247 View Post
 

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?

Nope :D if you don't have an issue with Volume do enjoy it!

 

Even my Schiit Vali has a smidge to much gain for my W1000x, it is how ever acceptable. I don't find the volume issue... an issue really 

post #22 of 32
Quote:
Originally Posted by money4me247 View Post
 

hey, this is off-topic, but I'm just curious about your guys thoughts on this. I read this on some random forum.

Quote:
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.

 

Bravo V3 full specs (Click to show)
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

 

Little Dot 1 Full Specs (Click to show)
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.;)

 

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.

 

3. You must be referring to tube amplifiers, because there are many solid state amplifiers with output impedance < 1.

 

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.

 

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.

 

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.

 

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.

 

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.

 

Hope that helps ...  

post #23 of 32
Quote:
Originally Posted by tomb View Post


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 :p

 

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 mean :confused_face: so 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! :D

 

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 headphonelol... 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 :rolleyes: 


Edited by money4me247 - 12/21/13 at 9:31am
post #24 of 32
Quote:
Originally Posted by money4me247 View Post
 

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 :rolleyes: 

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"

post #25 of 32
Quote:
Originally Posted by Mshenay View Post
 

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"

lol really? I see it being done quite often here on head-fi in response to really long posts. monkey see. monkey do. :p makes more sense to me as you can easily read the section pertaining to the response. but for you, mah audiophiliac brotha-n-arms embarking this noble quest for sonic perfection, i will keep your suggestion in mind.

 

ps: youse knowz i can ezily switch up mah writin stylez 2guarentee tat ya knowz dat u didn't write tat $hitttttt ;) 

post #26 of 32
Thread Starter 
Quote:
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? 


Edited by professorwiki - 12/21/13 at 10:37am
post #27 of 32
Quote:
Originally Posted by professorwiki View Post
 


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? 

that and noise, I can hear a little hum on my w1000x [32 ohms] from my Schiit Vali, and this noise is due to the gain. Gain raises the noise floor so high sensitivty and low impedance headphones are going to pick up on that extra smidge of noise. And honestly I don't mine the little extra bit of hum during the quiet tracks. It's part of the MAGIC of tubes, if I want JET BLACK I'll plug into my solid state

 

how ever, nicer tubes are DEAD SILENT. So most of teh draw backs to tubes are common to the entry level ones. As GREAT as the Vali is, even it's has a smidge of noise to it. But noise aside. The vali is an AWESOME tube! Do pick one up if you get a chance :D 

post #28 of 32
Thread Starter 

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!

post #29 of 32
Quote:
Originally Posted by professorwiki View Post
 

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!

enjoy it :D

post #30 of 32
Thread Starter 

Alright, so I got it in the mail, and I've had a chance to listen to it a little while. 

In short, it's awesome!

I am using Sony MDR-V6 headphones. My inputs are CD via an LG Blu Ray player. I just use the RCA outs for the audio. I also used my Sansa Sandisk Fuze MP3 player (it's the older one that came out a generation before these crappyy ones Sansa has out now under the name Fuze+). My other input is an Audio Technica LP120 turntable with Art DJpre II phono pre amp. 

The amp sounds great with all these inputs. I've listened to the Meet The Beatles album from the Capitol Records Vol. 1 set, a 45 rpm record of What is Life? by George Harrison, House of the Rising Sun by The Animals from Singles+ 2 CD compilation, and the song Make it bun dem from Skrillex & Damien Marley (I don't like dubstep or reggae, but I loved the Far Cry 3 game and the song is pretty cool from that haha). It sounds great with all of these. Of particular note are some songs from Alestorm on their Captain Morgan's Revenge album that usually sound quite clipped through good headphones, but it wasn't as pronounced through the tube amp. The tube does seem to smooth over some of that, which is great. Everything sounds like it should and is not overly colored, with the only difference from the solid state that I can really notice being the smoothing over some of the digital clipping. 

Quality wise, it feels pretty solid, a lot better than I expected actually. The EQ sliders are smooth and work well, although I am likely keeping the EQ flat.

There is no noise I can really notice through the headphones either. 

I might add more thoughts and details as I listen to it more (I'll likely try some of my Black Sabbath, Beatles, and Iggy Pop vinyl and some Ramones CDs next). 

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