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Speaker amps for headphones - Page 148

post #2206 of 2709

The plot thickens....

post #2207 of 2709
Quote:
Originally Posted by potterma View Post
 

I know who the holder of a bit of stock is of those SemiSouth parts ....

I'm tempted to ask, but I am pretty set on building an Aleph lol. Care to play devil's advocate here?

post #2208 of 2709
Quote:
Originally Posted by brunk View Post
 

I'm tempted to ask, but I am pretty set on building an Aleph lol. Care to play devil's advocate here?

Well, its not me!  I've got a few matched sets squirreled away, but that's it.  More are available from the same source I received these from...

post #2209 of 2709

I have an old Hafler DH220 that I would like to try with my HE-500's and Schiit Bifrost and am thinking of a passive preamp. I would use the setup only with these headphones, no speakers or other headphones. I read somewhere online (so it must be true) that for passive preamp you need an impedance ratio between amp and source of greater than 100:1, so 47,000:75 in my case and the source voltage is 2v.

Would a passive preamp work in my situation?

Any suggestions for a passive preamp?

 

Thanks

post #2210 of 2709
Quote:
Originally Posted by jamc View Post

I have an old Hafler DH220 that I would like to try with my HE-500's and Schiit Bifrost and am thinking of a passive preamp. I would use the setup only with these headphones, no speakers or other headphones. I read somewhere online (so it must be true) that for passive preamp you need an impedance ratio between amp and source of greater than 100:1, so 47,000:75 in my case and the source voltage is 2v.
Would a passive preamp work in my situation?
Any suggestions for a passive preamp?

Thanks

Try Creek or Pro-ject.
They may still offer some passive pre-amps.
post #2211 of 2709

Folks:

 

I don't know if I should start this discussion here or in a separate thread, but I have a question for you designers/builders/tinkerers.  It seems that pre-amps, given that they are just switches and attenuators, are simpler to design and build than DACs or Amps (or cans, obviously).  Okay, so if you had to design/describe a "dream" pre-amp (hey, I'm sure some of you dream about audio components... why not pre-amps?), assuming it had to have multiple inputs and outputs  -- but no head-amp -- what would it's design/description be and why?  Any explanation is fine, though I personally would prefer to see at least some technical basis for the choices -- but not too technical, so that us non-EE's can follow most of it. 

 

You can spend as much or as little as you want, and can offer up an existing model (boring) or a design of your own or a kluge, or whatever... just please explain why that particular design/description is optimal in your opinion.  The idea here is to educate me, and everybody else, about a part of the audio chain that doesn't really get much coverage... or respect, for that matter.

 

Thanks in advance for letting me riffle through your brains,

 

Gary

Troublemaker

post #2212 of 2709
Quote:
Originally Posted by Gary in MD View Post

Folks:

I don't know if I should start this discussion here or in a separate thread, but I have a question for you designers/builders/tinkerers.  It seems that pre-amps, given that they are just switches and attenuators, are simpler to design and build than DACs or Amps (or cans, obviously).  Okay, so if you had to design/describe a "dream" pre-amp (hey, I'm sure some of you dream about audio components... why not pre-amps?), assuming it had to have multiple inputs and outputs  -- but no head-amp -- what would it's design/description be and why?  Any explanation is fine, though I personally would prefer to see at least some technical basis for the choices -- but not too technical, so that us non-EE's can follow most of it. 

You can spend as much or as little as you want, and can offer up an existing model (boring) or a design of your own or a kluge, or whatever... just please explain why that particular design/description is optimal in your opinion.  The idea here is to educate me, and everybody else, about a part of the audio chain that doesn't really get much coverage... or respect, for that matter.

Thanks in advance for letting me riffle through your brains,

Gary
Troublemaker

Mr. Gary,

In some ways a pre-amp is very close to a headphone amp in terms of it's design.
A pre- amp normally has fixed gain, often 20 dB ( maybe more, maybe less!)
A headphone amp often has adjustable gain....say anywhere between 0 to 20 dB.
A headphone amp should have much lower output impedance, maybe as low as 1 or 2 Ohms.
Since a pre-amp is driving a high impedance load.....typically between 10-100 kOhms, a pre-amp can have an output impedance on the order of 1,000 Ohms (again, maybe more, maybe less).
And since a pre-amp is driving a fairly high impedance, it doesn't need to be able to output as much current as a pre-amp.

So in many ways, the ultimate pre-amp should have the same laundry list as the ultimate headphone amp:
Low noise
Low distortion, THD, IM
Wide enough bandwidth for audio
High enough slew rate for audio
Let's just say the maximum output voltage should be 10 Volts rms, enough to drive any load with lots of headroom to spare.
Maybe the ability to drive balanced lines, for power amps that accept balanced inputs (or "balanced") headphones.
Maybe the ability to accept balanced lines from your DAC or phono pre-amp or 8 track player (I'm so funny....)

To look at the schematic for the Bryston BHA-1 headphone amp, if you didn't know what you were looking at, you might think you were looking at the schematic for a Bryston pre-amp!
In fact, one of the selling points of the BHA-1 is that you may also use it as a pre-amp.

If you were talking about vacuum tube amps, the vacuum tube pre-amp would probably not have an output transformer.
But the vacuum tube headphone amp may have an output transformer if we want it to drive low impedance headphones.
It depends.....

Chris
Agitator
Edited by Chris J - 1/11/14 at 6:34pm
post #2213 of 2709
Quote:
Originally Posted by Gary in MD View Post
 

Folks:

 

I don't know if I should start this discussion here or in a separate thread, but I have a question for you designers/builders/tinkerers.  It seems that pre-amps, given that they are just switches and attenuators, are simpler to design and build than DACs or Amps (or cans, obviously).  Okay, so if you had to design/describe a "dream" pre-amp (hey, I'm sure some of you dream about audio components... why not pre-amps?), assuming it had to have multiple inputs and outputs  -- but no head-amp -- what would it's design/description be and why?  Any explanation is fine, though I personally would prefer to see at least some technical basis for the choices -- but not too technical, so that us non-EE's can follow most of it. 

 

You can spend as much or as little as you want, and can offer up an existing model (boring) or a design of your own or a kluge, or whatever... just please explain why that particular design/description is optimal in your opinion.  The idea here is to educate me, and everybody else, about a part of the audio chain that doesn't really get much coverage... or respect, for that matter.

 

Thanks in advance for letting me riffle through your brains,

 

Gary

Troublemaker

For me,first and foremost, it would have to be remote-controlled and passive (assuming the system is compliant). I would also want atleast 60 steps for true fine grain control. Standard steppers would be a no go because they like to degrade over heavy use, or get crackly from dust. This pretty much leaves 4 options - transformer, digital, relay and LDR. Digital is great, but high quality analog is better. Transformers are big and expensive, no thanks. So now it's up to relay or LDR based. Relays can achieve less distortion than LDR, but LDR has less components in the signal path. Both can be used with a micro-processor. Here's where I single one out. I would not use a LDR preamp without a microprocessor because of the varying impedance and non-linearities in their native state. As far as I know Tortuga Audio is the only one in the market with that capability. For relays, you have quite a few options open to you. If going balanced, relays offer a higher precision than LDR. If going single-ended, LDR will be pristine. Pick your poison! All IMO and YMMV of course lol.

post #2214 of 2709
Just throwing it out there but what about an audio gd M9. I have the M8 in office big rig and it is sweet .

Al
post #2215 of 2709
Quote:
Originally Posted by ALRAINBOW View Post

Just throwing it out there but what about an audio gd M9. I have the M8 in office big rig and it is sweet .

Al
.

You're throwing it out?
In the garbage?
Let me pick thru your trash, please!
post #2216 of 2709
Lmao. Yea my garbage ain't that good. He did say cost no object didn't he .

Al
post #2217 of 2709
Then I'd like gold plated connectors, please!
And a nice looking case.
With shiny knobs.
Maybe an impressive display. tongue.gif
post #2218 of 2709
A quick off topic , I am looking for dipole planner drivers for mids in speaker setup. . Similar to monsoon planers . Any body got some links please.
Al
post #2219 of 2709
Quote:
Originally Posted by ALRAINBOW View Post

A quick off topic , I am looking for dipole planner drivers for mids in speaker setup. . Similar to monsoon planers . Any body got some links please.
Al

Don't ask me.
I'll just say "MartinLogan".

BTW,
In my opinion, the best factory stereo I ever heard was in a GM I rented with Monsoon speakers.
post #2220 of 2709
Quote:
Originally Posted by Chris J View Post

Then I'd like gold plated connectors, please!
And a nice looking case.
With shiny knobs.
Maybe an impressive display. tongue.gif


How about a gold case, nice-looking connectors a shiny display and impressive knobs?

 

To follow this topic a bit further, the Audio-gd M9 appears to use relays for attenuation, and has 100 steps of attenuation. If I am understanding all of this correctly (not likely) that means that there are 100 relays, and one of them is opened for each step, allowing the signal to flow to one of 100 different resistor circuits, thus varying the output signal level.  So the components in the signal path include the open relay and whatever resistors are in the selected circuit.  The relay controller is not technically in the signal chain, since it is simply telling the relays to open and close according to external commands.  And of course this is duplicated for each channel.  Right?

 

Alternatively, if I am understanding the LDR system correctly, the the only thing in the Tortuga signal chain is the LDR, which varies its resistance based on how much light hits it. I assume that means that the LDRs are shut off from all external stray light in the critical wavelengths, and I'm guessing that those wavelengths are well into the optical part of the spectrum, otherwise you would get significant drift due to changes in temperature introducing stray light...???  In any case, the light has to be carefully controlled to ensure proper attenuation, because the LDR response is not perfectly linear with changes in the light. Based on earlier discussions in this thread, the response of each individual LDR is also unique, so you would have to either map each LDR's response and then teach the controller how much light to shine on that particular resistor to get a particular level of resistance, while hoping that it never changes (fat chance) or instead put some sort of feedback loop in to measure the actual output level and adjust the light accordingly in real time.  With the latter, the chain is not perfectly pristine any more, and is definitely not as simple as the relay system, which would seem to me to be a bit more predictable, as long as one assumes the resistors are stable in their performance over time.  

 

So how much of this did I get right?

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