My reason for asking, if you simply use a resistive splitting network you lose 3 dB for every split.
Therefore you need two buffers, one for the outside world and one for the interior. Also when using a buffer you counter the chances of the external equipment to mess with the phase and frequency response due to loading.
Although the amp output impedance is low, the series resistor in the output would cause the signal to be attenuated when inserting headphones, especially ones with low impedance.
Andrew's idea would work if we have a switched line out. In other words a selector that switches between headphones and line out. This would solve the problem. The line out could also include a resistor network that would counter the headphone amp gain.
I causion those thinking of this method simply because if the headphone amp is noisy in any way your power amp will boost the noise as well and this may not be such a good idea.
Ciao
Nico
Therefore you need two buffers, one for the outside world and one for the interior. Also when using a buffer you counter the chances of the external equipment to mess with the phase and frequency response due to loading.
Although the amp output impedance is low, the series resistor in the output would cause the signal to be attenuated when inserting headphones, especially ones with low impedance.
Andrew's idea would work if we have a switched line out. In other words a selector that switches between headphones and line out. This would solve the problem. The line out could also include a resistor network that would counter the headphone amp gain.
I causion those thinking of this method simply because if the headphone amp is noisy in any way your power amp will boost the noise as well and this may not be such a good idea.
Ciao
Nico
There is nothing different from this headphone amp to an opamp except more distortion, less OLG, etc. It's still an amp and with a line out jack it comes with the added functionality of being used as a preamp without unplugging headphones. A line out jack can only add to its value, not decrease.
If we use a opamp buffer, we defeat the whole purpose of having a line out. Hugh wouldn't want to add an opamp that wasn't really necessary (AFAIK).
- keantoken
If we use a opamp buffer, we defeat the whole purpose of having a line out. Hugh wouldn't want to add an opamp that wasn't really necessary (AFAIK).
- keantoken
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For what it's worth, I don't see the point of line out from this - this is an end of the line device from my perspective.
I'm probably not the only one here that would have a problem "daisy chaining" the audio signal through different gain stages.
In general, throughout all of this forum and the wider world there is the idea that opamps are bad and they have no place in "high end" equipment. I don't feel that way and I won't waste my time trying to convince those that subscribe to that particular notion otherwise.
So, my opinion: If it is to have line out, it should be buffered, using good quality opamps.
I'm probably not the only one here that would have a problem "daisy chaining" the audio signal through different gain stages.
In general, throughout all of this forum and the wider world there is the idea that opamps are bad and they have no place in "high end" equipment. I don't feel that way and I won't waste my time trying to convince those that subscribe to that particular notion otherwise.
So, my opinion: If it is to have line out, it should be buffered, using good quality opamps.
Agree. No requirement for line out at all, and if there were, the Zout of the headphone amp, and it's distortion profile, would make it an excellent opamp of the discrete persuasion.
Nico, I will try to find this enclosure on the net, I'm pretty sure I got it from RS Components.
Cheers,
Hugh
Nico, I will try to find this enclosure on the net, I'm pretty sure I got it from RS Components.
Cheers,
Hugh
If we were to have a line out. In other words use HAKSA as pre/line amp then I would suggest we use a headphone socket such as this one.
If the headphone is inserted it cuts off the rest of the audio equipment. When it is removed then it passes the signal to a pair of line out RCAs on the back plate.
http://za.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0449348#header
If the headphone is inserted it cuts off the rest of the audio equipment. When it is removed then it passes the signal to a pair of line out RCAs on the back plate.
http://za.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0449348#header
One may still want to use an attenuation pad to cancel the gain of HAKSA at the line out. This would facilitate HAKSA being the pre-amp having bass, treble, master volume, cross feed and balance controls to play with at hearts content.
I have just played a little with cross-feed into my main amp. It is quite useful when listening to your home TV watching movies. It eliminates the very pronounced car drive up on the left channel and drives off on the right channel.
The cross-feed gets rid of this very odd sounding effect and is most definitely useful in the application.
I have one bad thing to report as well. I fiddled with the circuit and decided to hard bias the bottom output devices the amp is now sinhle ended, The efective character is oodles nices. Very small change to be made which offrs a beter presentat=iun,
I have just played a little with cross-feed into my main amp. It is quite useful when listening to your home TV watching movies. It eliminates the very pronounced car drive up on the left channel and drives off on the right channel.
The cross-feed gets rid of this very odd sounding effect and is most definitely useful in the application.
I have one bad thing to report as well. I fiddled with the circuit and decided to hard bias the bottom output devices the amp is now sinhle ended, The efective character is oodles nices. Very small change to be made which offrs a beter presentat=iun,
Here is an URL to: Hammond 1455 extruded aluminum chassis. These are available as either anodized black or natural aluminum. Mouser stocks them.
Hello Hugh
A single ended with the Aksa sound... is it possible to see the schematic ?
Thank
Bye
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Hello Carl
The Hammond case 1455T1601B do have 160 L x 161 W x 51.5 H mm
It's one of the larger case, they don't go more than 161 mm of width for the flat face side.
Bye
Gaetan
Attachments
Thanks Carl for finding the boxes. Those are definitely not die-cast, it is extruded and very nice. I like this one, there is a lot of space inside and the size ratios make it look very attractive.
http://www.hammondmfg.com/pdf/1455T2201.pdf
http://www.hammondmfg.com/pdf/1455T2201.pdf
On the other hand, changing the current design to class A is a simple matter, the bottom output transistor is converted to a constant current generator.
It could be adjustable and guys can set the max current for their particular headphones. High impedance types will need less current while the few who has 32 ohms would need more current.
Not adjustable with a pot, but by resistor value only on a selection chart.
It could be adjustable and guys can set the max current for their particular headphones. High impedance types will need less current while the few who has 32 ohms would need more current.
Not adjustable with a pot, but by resistor value only on a selection chart.