OK, I have read most of the posts regarding this amp. I bought mine for about $500 expecting a very good, but not perfect amp. I am in love with HiFiMan phones, starting with HE-400s, recently graduating to HE-560s ( Christmas present to myself ).
Build quality is very good, I wish I could say the same thing about the documentation ! Well, being an Electrical Engineer has its benefits for an inquisitive audiophile. Here is what I learned, followed by my listening impressions, pre and post mod.
1) First off the stock Chinese/French tubes have got to go ! I went with a pair of NOS ST shape RCA 6AS7Gs for the outputs and a NOS Slyvania 6SL7GT chrome top for the input tube.
2) The HiFiMan cans are 35 ohm impedance, hard to drive and right near the lower limit of what the amp can drive. When driven from the std analog output of a CD player there just wasn't enough volume from the LD MK9 for me, I had the volume control turned all the way up !
3) I put the amp on the test bench and confirmed on the oscilloscope what I had heard in the phones. With the voltage level coming from the CD player the output from the amp was no where near its maximum level.
4) So the amp needed to come apart to see what was going on in there. (PLEASE DO NOT TAKE THE AMP APART UNLESS YOU ARE A CERTIFIED REPAIR TECHNICIAN AND HAVE EXPERIENCE WITH TUBE AMPLIFIERS, POTENTIAL LETHAL VOLTAGES ARE PRESENT!) This is where the men get separated from the boys, there is no bottom cover on this amp ! The chassis is made of a one piece flattened tubular extrusion. You have to remove the front and back panels, then try to slide out the PC board. Problem is there a gaggle of wires attached between the PC board and the power transformer. I didn't want to have to unsolder all these wires, so after wrestling with the board for 15 minutes I finally figured out how to get the board out far enough to get a good look.
5) I discovered two small red gain switches (one for each of the L and R channels). They were set for "low", this explained the low volume. I switched both channels to "hi" and things got a lot better! Turns out that you can access these switches through the oblong cooling holes in the bottom of the amp! Now the CD output was driving the phones to an acceptable level, but I wanted more !
6) I increased the bias in the output tubes by about 25% and was able to get another 100 MW of output power into the 35 ohm impedance of the HiFiMan phones.
7) Last remaining issue was still not enough gain. To take advantage of the extra output power I needed more input. I solved this by finally going digital with music source. Now running JRiver s/w on my laptop, USB out into a Raccoon tube hybrid SG300 DAC preamp/headphone amp (available on eBay for $149). The level of the Raccoon preamp section output adjusts with its volume control. When I hit the LD MK9 with about 4 volts peak (CD output is about 2 volts peak) I get the volume I desired, now I run the LD MK9 with the volume control at half way and it plays LOUD, with plenty left for those songs recorded at lower volume.
What I heard with LD MK9 stock (as delivered) running from CD player:
Good sound quality, but not nearly enough volume with just so-so clarity/resolution.
What I heard after setting gain switches to "hi" (still original tubes, from CD player)
Now I had enough volume for the HiFiMan HE-560s to come alive !
What I heard after installing NOS American tubes ( still CD player )
The slight midrange harshness gone, deeper bass, more extension on the top end too, and more clarity& detail. Plays slightly louder at same position on volume control.
What I heard after increasing the bias in the output tubes, laptop running JRiver s/w, Racoon USB DAC with DanaCable USB cable driving the LD MK9 amp, DanaCable headphone cable for HiFiMan phones.
In a word sumptuous, full bodied, imaging to die for, everything I could have hoped for ! My wife even called it addictive, said if she kept the phones on she wouldn't be able to get anything done all day ! One of my favorite tracks to listen to now is BS&T's "Spinning Wheel", the horns never sounded so vibrant and real. David Clayton Thomas never sounded so real and alive, I'm HOOKED !
Be sure to get hold of me if you have any questions or comments.
THAT's A GOOD COMMENTOK, I have read most of the posts regarding this amp. I bought mine for about $500 expecting a very good, but not perfect amp. I am in love with HiFiMan phones, starting with HE-400s, recently graduating to HE-560s ( Christmas present to myself ).
Build quality is very good, I wish I could say the same thing about the documentation ! Well, being an Electrical Engineer has its benefits for an inquisitive audiophile. Here is what I learned, followed by my listening impressions, pre and post mod.
1) First off the stock Chinese/French tubes have got to go ! I went with a pair of NOS ST shape RCA 6AS7Gs for the outputs and a NOS Slyvania 6SL7GT chrome top for the input tube.
2) The HiFiMan cans are 35 ohm impedance, hard to drive and right near the lower limit of what the amp can drive. When driven from the std analog output of a CD player there just wasn't enough volume from the LD MK9 for me, I had the volume control turned all the way up !
3) I put the amp on the test bench and confirmed on the oscilloscope what I had heard in the phones. With the voltage level coming from the CD player the output from the amp was no where near its maximum level.
4) So the amp needed to come apart to see what was going on in there. (PLEASE DO NOT TAKE THE AMP APART UNLESS YOU ARE A CERTIFIED REPAIR TECHNICIAN AND HAVE EXPERIENCE WITH TUBE AMPLIFIERS, POTENTIAL LETHAL VOLTAGES ARE PRESENT!) This is where the men get separated from the boys, there is no bottom cover on this amp ! The chassis is made of a one piece flattened tubular extrusion. You have to remove the front and back panels, then try to slide out the PC board. Problem is there a gaggle of wires attached between the PC board and the power transformer. I didn't want to have to unsolder all these wires, so after wrestling with the board for 15 minutes I finally figured out how to get the board out far enough to get a good look.
5) I discovered two small red gain switches (one for each of the L and R channels). They were set for "low", this explained the low volume. I switched both channels to "hi" and things got a lot better! Turns out that you can access these switches through the oblong cooling holes in the bottom of the amp! Now the CD output was driving the phones to an acceptable level, but I wanted more !
6) I increased the bias in the output tubes by about 25% and was able to get another 100 MW of output power into the 35 ohm impedance of the HiFiMan phones.
7) Last remaining issue was still not enough gain. To take advantage of the extra output power I needed more input. I solved this by finally going digital with music source. Now running JRiver s/w on my laptop, USB out into a Raccoon tube hybrid SG300 DAC preamp/headphone amp (available on eBay for $149). The level of the Raccoon preamp section output adjusts with its volume control. When I hit the LD MK9 with about 4 volts peak (CD output is about 2 volts peak) I get the volume I desired, now I run the LD MK9 with the volume control at half way and it plays LOUD, with plenty left for those songs recorded at lower volume.
What I heard with LD MK9 stock (as delivered) running from CD player:
Good sound quality, but not nearly enough volume with just so-so clarity/resolution.
What I heard after setting gain switches to "hi" (still original tubes, from CD player)
Now I had enough volume for the HiFiMan HE-560s to come alive !
What I heard after installing NOS American tubes ( still CD player )
The slight midrange harshness gone, deeper bass, more extension on the top end too, and more clarity& detail. Plays slightly louder at same position on volume control.
What I heard after increasing the bias in the output tubes, laptop running JRiver s/w, Racoon USB DAC with DanaCable USB cable driving the LD MK9 amp, DanaCable headphone cable for HiFiMan phones.
In a word sumptuous, full bodied, imaging to die for, everything I could have hoped for ! My wife even called it addictive, said if she kept the phones on she wouldn't be able to get anything done all day ! One of my favorite tracks to listen to now is BS&T's "Spinning Wheel", the horns never sounded so vibrant and real. David Clayton Thomas never sounded so real and alive, I'm HOOKED !
Be sure to get hold of me if you have any questions or comments.
OK, I have read most of the posts regarding this amp. I bought mine for about $500 expecting a very good, but not perfect amp. I am in love with HiFiMan phones, starting with HE-400s, recently graduating to HE-560s ( Christmas present to myself ).
Build quality is very good, I wish I could say the same thing about the documentation ! Well, being an Electrical Engineer has its benefits for an inquisitive audiophile. Here is what I learned, followed by my listening impressions, pre and post mod.
1) First off the stock Chinese/French tubes have got to go ! I went with a pair of NOS ST shape RCA 6AS7Gs for the outputs and a NOS Slyvania 6SL7GT chrome top for the input tube.
2) The HiFiMan cans are 35 ohm impedance, hard to drive and right near the lower limit of what the amp can drive. When driven from the std analog output of a CD player there just wasn't enough volume from the LD MK9 for me, I had the volume control turned all the way up !
3) I put the amp on the test bench and confirmed on the oscilloscope what I had heard in the phones. With the voltage level coming from the CD player the output from the amp was no where near its maximum level.
4) So the amp needed to come apart to see what was going on in there. (PLEASE DO NOT TAKE THE AMP APART UNLESS YOU ARE A CERTIFIED REPAIR TECHNICIAN AND HAVE EXPERIENCE WITH TUBE AMPLIFIERS, POTENTIAL LETHAL VOLTAGES ARE PRESENT!) This is where the men get separated from the boys, there is no bottom cover on this amp ! The chassis is made of a one piece flattened tubular extrusion. You have to remove the front and back panels, then try to slide out the PC board. Problem is there a gaggle of wires attached between the PC board and the power transformer. I didn't want to have to unsolder all these wires, so after wrestling with the board for 15 minutes I finally figured out how to get the board out far enough to get a good look.
5) I discovered two small red gain switches (one for each of the L and R channels). They were set for "low", this explained the low volume. I switched both channels to "hi" and things got a lot better! Turns out that you can access these switches through the oblong cooling holes in the bottom of the amp! Now the CD output was driving the phones to an acceptable level, but I wanted more !
6) I increased the bias in the output tubes by about 25% and was able to get another 100 MW of output power into the 35 ohm impedance of the HiFiMan phones.
7) Last remaining issue was still not enough gain. To take advantage of the extra output power I needed more input. I solved this by finally going digital with music source. Now running JRiver s/w on my laptop, USB out into a Raccoon tube hybrid SG300 DAC preamp/headphone amp (available on eBay for $149). The level of the Raccoon preamp section output adjusts with its volume control. When I hit the LD MK9 with about 4 volts peak (CD output is about 2 volts peak) I get the volume I desired, now I run the LD MK9 with the volume control at half way and it plays LOUD, with plenty left for those songs recorded at lower volume.
What I heard with LD MK9 stock (as delivered) running from CD player:
Good sound quality, but not nearly enough volume with just so-so clarity/resolution.
What I heard after setting gain switches to "hi" (still original tubes, from CD player)
Now I had enough volume for the HiFiMan HE-560s to come alive !
What I heard after installing NOS American tubes ( still CD player )
The slight midrange harshness gone, deeper bass, more extension on the top end too, and more clarity& detail. Plays slightly louder at same position on volume control.
What I heard after increasing the bias in the output tubes, laptop running JRiver s/w, Racoon USB DAC with DanaCable USB cable driving the LD MK9 amp, DanaCable headphone cable for HiFiMan phones.
In a word sumptuous, full bodied, imaging to die for, everything I could have hoped for ! My wife even called it addictive, said if she kept the phones on she wouldn't be able to get anything done all day ! One of my favorite tracks to listen to now is BS&T's "Spinning Wheel", the horns never sounded so vibrant and real. David Clayton Thomas never sounded so real and alive, I'm HOOKED !
Be sure to get hold of me if you have any questions or comments.
