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Looking for a good tube amp for my Massdrop x Fostex Thx00 purplehearts

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#1
Hi

The tilte says everything, any reccomendations?

Or would i be better off with the Massdrop THXAAA 789? I will be buying the Khadas tone board DAC soon with the balanced outputs.

Best regards
 

M00ndancer

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#2
Don't you like the sound of your purple hearts? There is no benefit of getting a tube amp unless you want to colour the sound. (most tube amp adds distortion and artifacts) Do you feel that's it's underpowered with the gear you have today?
What are you using today to power your headset?
The THXAAA 789 is transparent amp (compared to a tube amp) and will only add volume and power.
 
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#3
Don't you like the sound of your purple hearts? There is no benefit of getting a tube amp unless you want to colour the sound. (most tube amp adds distortion and artifacts) Do you feel that's it's underpowered with the gear you have today?
What are you using today to power your headset?
The THXAAA 789 is transparent amp (compared to a tube amp) and will only add volume and power.
I was using for some time the Asus Xonar Essence STX soundcard of my PC, which sounds a lot better than my onboard sound from my desktop.

However a friend gave me a Technics A900s reference amp (picture attached) it's ca. from 1995. I connected my headphones to the amp, and the amp to the RCA outputs of my soundcard, so basically my Asus Xonar Essence STX is only functioning as a DAC now.

There was a good sound improvement , but i don't use speakers, so it's kinda wasted for headphones only. I am hoping to get further sound improvement with a headphone amp + dac. And maybe sell the amp.

I know that the THX AAA is transparent, that's why i am considering it. I do like the sound signature of a tube amp much more than solid state, and tube rolling is fun.
 

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solderdude

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#4
I was using for some time the Asus Xonar Essence STX soundcard of my PC, which sounds a lot better than my onboard sound from my desktop.

However a friend gave me a Technics A900s reference amp (picture attached) it's ca. from 1995. I connected my headphones to the amp, and the amp to the RCA outputs of my soundcard, so basically my Asus Xonar Essence STX is only functioning as a DAC now.

There was a good sound improvement , but i don't use speakers, so it's kinda wasted for headphones only. I am hoping to get further sound improvement with a headphone amp + dac. And maybe sell the amp.

I know that the THX AAA is transparent, that's why i am considering it. I do like the sound signature of a tube amp much more than solid state, and tube rolling is fun.
The reason for the Technics SE-A900S sounding different is of technical origin.
The output resistance from the HP socket is a whopping 330 Ohm as seen in the specs of the manual (have a poor quality copy of it).
The amp's power output signal is routed through R561 (150 Ohm 1W) + R562 (180 Ohm/1W) = 330 Ohm.
The other channel runs through R562 and R564.
This resistance is in series with the headphone.

So the real reason this amp sounded quite different is due to the high Rout, not the 'amplifier qualities', and creates a small bass boost of around 2dB around 45Hz.
This is certainly audible.

A tube amp also would not give the same bass boost as in general the output R is lower than 330 Ohm and those amps that have a high output R are not suited to drive low impedance headphones like the TH-X00
 
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#5
The reason for the Technics SE-A900S sounding different is of technical origin.
The output resistance from the HP socket is a whopping 330 Ohm as seen in the specs of the manual (have a poor quality copy of it).
The amp's power output signal is routed through R561 (150 Ohm 1W) + R562 (180 Ohm/1W) = 330 Ohm.
The other channel runs through R562 and R564.
This resistance is in series with the headphone.

So the real reason this amp sounded quite different is due to the high Rout, not the 'amplifier qualities', and creates a small bass boost of around 2dB around 45Hz.
This is certainly audible.

A tube amp also would not give the same bass boost as in general the output R is lower than 330 Ohm and those amps that have a high output R are not suited to drive low impedance headphones like the TH-X00
Well it doesn't just alter the sound, it improves it massively. More details come to light, the bass is much tighter, with the STX the bass was way too bloomy, the highs are not as sparkly anymore and not as sibilant. The overall sound is also clearer. The bass itself isn't louder, but more isolated, it doesn't invade the mids anymore.

i once tried the Schiit Fulla and it also sounded much better than my Asus essence stx, however differntly than the Technics.
The Fulla made the sound clearer, much punchier, and was more detailed, was more detailed. Also bassier and sharper in a pleasant way.

The Asus simply sounds bad compared to any entry level amp.

So i don't think it#s only due Technics technical origin.
 

solderdude

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#6
In that case just buy the THX AAA :D ... and add 330 Ohm output resistors.
 

solderdude

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#8
You don't have to 'get' me nor my explanations.

I never heard nor measured the amp section.
I worked for Technics/Panasonic (service dept) and happen to know the A900S.
Owned and measured the TH-X00 as well.

Also I am not saying there are no differences between amplifiers.
Have been designing/measuring this kind of stuff for long for that.
As the British say... horses for coarses.

I gave you a logical technical explanation ... the output resistance.
You are free to discard everything I say. Many do anyway.
 
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#9
You don't have to 'get' me nor my explanations.

I never heard nor measured the amp section.
I worked for Technics/Panasonic (service dept) and happen to know the A900S.
Owned and measured the TH-X00 as well.

Also I am not saying there are no differences between amplifiers.
Have been designing/measuring this kind of stuff for long for that.
As the British say... horses for coarses.

I gave you a logical technical explanation ... the output resistance.
You are free to discard everything I say. Many do anyway.
I don't quite understand it tbh, i am simply wondering if there is a not too expensive tube amp around that i could use instead of the Technics and get better sound, than i am already getting and if the THX wouldn't be a better option because the Fostex have low ohm's.

I am thankful for the technical explanation (even tho i don't quite understand it) as i am grateful to anyone that takes the time to answer my post :)
 

bunkbail

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#12
Loxjie P20 is a very affordable balanced tube amp ($99) and it measures very well for a tube amp. There's another forum you can find for the measurements yourself and it's a pretty exhaustive test.
 

M00ndancer

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#13
I don't quite understand it tbh, i am simply wondering if there is a not too expensive tube amp around that i could use instead of the Technics and get better sound, than i am already getting and if the THX wouldn't be a better option because the Fostex have low ohm's.
As @solderdude states: The reason you hear a different sound is the high resistance. Assuming that you're using the STX correctly (connected from the back and settings) it's pretty good card with a good enough amp.

The THX wont give you the sound you're after. If you don't like the sound from your purple hearts, get another pair or use an EQ. At least in my opinion. An amp should not alter the sound. But different headphones does as long as they are properly matched to the amp.
Sure, I can understand the fun in messing with tubes. But adding distortion to a signal is not the way to go.
The THX with the STX as a source is an excellent choice. You have to understand that with the technics or a tube amp, you're not getting a better sound just a different one, technically inferior. That might suit your taste.
 

M00ndancer

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#14
Yeah but there are a lot of tube amps that aren't featured in that list and measurement isn't everything.
Unless you can do a proper abx test with enough people, there is only the measurement to go by.
Tube amps distort the signal, does not improve it. They add stuff to the audio.
If you prefer another sound that's ok. But I would prefer to use an EQ or different headphone since no headphone is perfect for every user.
I prefer to have a transparent path of audio all the way to my headphones. Then I can use whatever technique, EQ, headphone to listen to the music to cater for the type of sound I prefer that day.
 

GGroch

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#15
Nobunaga,

The Purplehearts are quite low impedance headphones (25 ohms), so theoretically they will not provide an accurate sound, particularly in the bass, with headphone amps that have high output impedance. To match the Purplehearts you would want an amp with 3 ohms or less output impedance.

The Technics amp has an extremely high output impedance, which as Solderdude points out, means its output into your headphones should not be at all accurate. That does not mean you or others would not find it pleasant.

The Asus Xonar has a headphone output impedance of 10 ohms, so also too high to be accurate with your Purplehearts. Not a good choice for accurate reproduction.

The great majority of tube headphone amplifiers also have high output impedances, so will not match well with the Purplehearts for accurate reproduction. There are quite a few that will work well. The Woo WA6 is one example. Most are either Transformer Coupled (like the WA6) or are hybrid, with a tube preamp section and a solid state amp section.

So, neither the Asus or Technics are technically good choices...but, you like the Technics better. I think you need to compare to a better suited amp. Perhaps you should try or borrow a low impedance amp 1st (almost all of Amir's recent headphone amp reviews include a chart of measured output. See if you like an accurate amp low impedance amp 1st. If you do, then look for good matches like the WA6. If not, then you will probably have to listen to a bunch to see which ones best match your tastes. Nothing wrong with that
 
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#16
Unless you can do a proper abx test with enough people, there is only the measurement to go by.
Tube amps distort the signal, does not improve it. They add stuff to the audio.
If you prefer another sound that's ok. But I would prefer to use an EQ or different headphone since no headphone is perfect for every user.
I prefer to have a transparent path of audio all the way to my headphones. Then I can use whatever technique, EQ, headphone to listen to the music to cater for the type of sound I prefer that day.
it's not a question of "another sound", like i previously mentioned the Asus for sure isn't transparent, you can pretty much use any amp/dac combo, or simply a standalone amp and use the Asus soundcard as DAC and you will get a BIG sound improvement, wider soundstage, more details, tighter bass, more clarity, cleaner sound. These are improvement from an objective point of view.
 
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#17
Nobunaga,

The Purplehearts are quite low impedance headphones (25 ohms), so theoretically they will not provide an accurate sound, particularly in the bass, with headphone amps that have high output impedance. To match the Purplehearts you would want an amp with 3 ohms or less output impedance.

The Technics amp has an extremely high output impedance, which as Solderdude points out, means its output into your headphones should not be at all accurate. That does not mean you or others would not find it pleasant.

The Asus Xonar has a headphone output impedance of 10 ohms, so also too high to be accurate with your Purplehearts. Not a good choice for accurate reproduction.

The great majority of tube headphone amplifiers also have high output impedances, so will not match well with the Purplehearts for accurate reproduction. There are quite a few that will work well. The Woo WA6 is one example. Most are either Transformer Coupled (like the WA6) or are hybrid, with a tube preamp section and a solid state amp section.

So, neither the Asus or Technics are technically good choices...but, you like the Technics better. I think you need to compare to a better suited amp. Perhaps you should try or borrow a low impedance amp 1st (almost all of Amir's recent headphone amp reviews include a chart of measured output. See if you like an accurate amp low impedance amp 1st. If you do, then look for good matches like the WA6. If not, then you will probably have to listen to a bunch to see which ones best match your tastes. Nothing wrong with that
That amp is sadly over my budget :(. Do you think the THX is a good match?
 

M00ndancer

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#18
That amp is sadly over my budget :(. Do you think the THX is a good match?
You can use the THX, or the Atom amp.
This chart is what you should be looking for in impedance.
 

watchnerd

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#19
Is the goal to drive the Purplehearts as transparently as possible?

Or is the goal to have a tube amp, period, even if it isn't a good match for the Purplehearts, because you'll switch headphones at some point?
 

GGroch

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#20
The thing is, the choices below 1 ohm with sufficient output should provide the sound the Fostex was shooting for with your Purplehearts. The concern might be that you do not like the Purple hearts sound as envisioned by Fostex. So, my suggestion is to try to a good match 1st. If you do not like what you hear, then you can either choose a different amp that provides a sound closer to what you like...or choose different headphones that sound the way you like when they are driven accurately. The CTH and Schiit Lyr are both hybrids from the above chart should match well at a lower cost.
 
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