szoze said:
Because it's George.
Actually we all got together on Sunday for the amplifier shhotout and guess which amp won? And George shook my hand. Just take George for what he is, crusty George on DIYaudio. But we have plenty of laughter when we get together, so don't get the wrong idea about 'crusty.'
George, reveal your lighter side here, people are getting only a half impression of you, and that impression is pretty right
, but it doesn't show your other side. Know any good audio jokes? That always helps to break the barrier.Here a pic of the amp (yes, George, I don't believe it happened - based on past experiences we have in common):
Joe R.
Joe Rasmussen said:
George, reveal your lighter side here, people are getting only a half impression of you, and that impression is pretty right
No! because it's the truth that counts here, nothing more nothing less. No half truths or giving anyone a reach around.
George
some results
Ok Joe, I have tried that using a 10uf Jantzen ( crosscap ) cap in series with a 301 ohm vishay dale rn55 resistor and a 1 nano silver mica cap across the rca socket.
The sound is improved, especially depth and presence,but I think I may have lost a little bit of dynamics, but that may be me adjusting to a small reduction in gain?.I think that the two series lm4562 (i/v and summing ) and the buffer after that robs just a little bit of the music away.
I think George might have said somewhere that the ad8066? was the only true Transimpeadance opamp??, but it would take a bit of surgery to impliment as i/v.Anyway do you think it would be beneficial to try that opamp as i/v over the lm4562??.
One last thing...the standard feedback resistor and capacitor in the feedback loop for the i/v are they acceptable....it would be easy for me to impliment different values.
Thanks again
PHP:
Hotwiring from one side of the outputs of the I/V converter, via a 2-3uF coupling cap to block the DC there, then a series resistor typically 330-390R and the 1n8 to 2n2 to ground and wire to a new pair of RCA sockets on the back panel.Ok Joe, I have tried that using a 10uf Jantzen ( crosscap ) cap in series with a 301 ohm vishay dale rn55 resistor and a 1 nano silver mica cap across the rca socket.
The sound is improved, especially depth and presence,but I think I may have lost a little bit of dynamics, but that may be me adjusting to a small reduction in gain?.I think that the two series lm4562 (i/v and summing ) and the buffer after that robs just a little bit of the music away.
I think George might have said somewhere that the ad8066? was the only true Transimpeadance opamp??, but it would take a bit of surgery to impliment as i/v.Anyway do you think it would be beneficial to try that opamp as i/v over the lm4562??.
One last thing...the standard feedback resistor and capacitor in the feedback loop for the i/v are they acceptable....it would be easy for me to impliment different values.
Thanks again
hhhhhmmmm
....just had a look on Farnell, and they only have the ad844 in 8pin dil or 16 pin soic!...so not sure if I could fit it somehow?...would it be worth the trouble to impliment anyway....what I am trying to say is...do u think it would be a clear improvement over the lm4562 i/v arrangement I am using at the moment??
p.s ..yes I dont like output caps either...but the jantzen crosscaps are very very good, way better than the Jaycar polyprops!
....just had a look on Farnell, and they only have the ad844 in 8pin dil or 16 pin soic!...so not sure if I could fit it somehow?...would it be worth the trouble to impliment anyway....what I am trying to say is...do u think it would be a clear improvement over the lm4562 i/v arrangement I am using at the moment??
p.s ..yes I dont like output caps either...but the jantzen crosscaps are very very good, way better than the Jaycar polyprops!
For all the trouble to implement the AD844 and you'll still be capacitor coupled (yuk), I would go with the discrete Transimpedance of the LC ZapII and it has a discrete single ended output stage as well, and the big bonus it's direct coupled all the way through from input to output with dc servo's taking care of any dc offset. Here are the fitting instructions to do it as now I have no use for them since the HD970 is no longer in production.
You may also look at Russ White's (Twisted Pear) Counterpoint output stage as this is true discrete Transimpedance also, but it doesn't have as low impedance output stage as the ZapII which is good to have, especially when driving passives like my Lightspeed Attenuator.
Cheers George
You may also look at Russ White's (Twisted Pear) Counterpoint output stage as this is true discrete Transimpedance also, but it doesn't have as low impedance output stage as the ZapII which is good to have, especially when driving passives like my Lightspeed Attenuator.
Cheers George
nice!
...I have done another mod over the weekend to my arrangement which is....lm4562 as i/v.... to output cap.... to 241 ohm resistor then out.
I read on here about biasing the lm4562 into class A operation, anyway I have used 6.8k ohm ( all I had on hand ) from output just before the output cap to -12volt ( close to pin 4 ). This gives me about 1.7mA constant current thru the resistor.
Anyway the sound improvement is not subtle...the depth and emotion it gives to voices and the dynamics are fantastic and very musical too.
Considering that there are two opamps on one die....How much do you think I could bump up the Class A level to?...I think the max output for the lm4562 is about 23mA ?.I dont want to really want to go the point of mounting a heatsink on the opamp if I can avoid it.
Paul
...I have done another mod over the weekend to my arrangement which is....lm4562 as i/v.... to output cap.... to 241 ohm resistor then out.
I read on here about biasing the lm4562 into class A operation, anyway I have used 6.8k ohm ( all I had on hand ) from output just before the output cap to -12volt ( close to pin 4 ). This gives me about 1.7mA constant current thru the resistor.
Anyway the sound improvement is not subtle...the depth and emotion it gives to voices and the dynamics are fantastic and very musical too.
Considering that there are two opamps on one die....How much do you think I could bump up the Class A level to?...I think the max output for the lm4562 is about 23mA ?.I dont want to really want to go the point of mounting a heatsink on the opamp if I can avoid it.
Paul
Just looked at the lm4562 it's slew rate (20v/us) is too low to be a good i/v converter.
Correct me if I'm wrong I've always been led to believe that you need good high slew rate amps up over >200v/us or even 2000v/us to be good i/v amps otherwise the hf corner noise spikes can't be handled.
Cheers George
Correct me if I'm wrong I've always been led to believe that you need good high slew rate amps up over >200v/us or even 2000v/us to be good i/v amps otherwise the hf corner noise spikes can't be handled.
Cheers George
hhhhhmmmm
...I dont know to be honest..I am still learning lots of stuff about opamps on here.I think Twisted Pair Audio use the lm4562 as i/v in one of there i/v buffers ??.....I dont know if anyone will back me up here....but I really do like the lm4562 biased into class A as i/v...dont worry, I have thought about trying a couple of different opamps there ..ad844,ad797,ad826,ad811 or ad8066 ( extereme boky loves those I believe )...
...I dont know to be honest..I am still learning lots of stuff about opamps on here.I think Twisted Pair Audio use the lm4562 as i/v in one of there i/v buffers ??.....I dont know if anyone will back me up here....but I really do like the lm4562 biased into class A as i/v...dont worry, I have thought about trying a couple of different opamps there ..ad844,ad797,ad826,ad811 or ad8066 ( extereme boky loves those I believe )...
Have a look at the data sheets on the ones Boky likes you'll see that the worst one has 10 x the slew rate of the lm4562 (20v/us)and the good ones have over 100 x the slew rate of the lm4562. This is why they're good for I/V stage, if I went for an opamp it would be the AD844 (2000v/us) and discrete i/v's can be even better.
See how the +&- inputs feed directly into the emitters of the transistors not the base of the transistors, this is a Transimpedace amp, true low input impedance (typically 50ohms for the AD844) that current output dacs like the PCM56, TDA1541 and others love to see for low distortion performance.
Cheers George
See how the +&- inputs feed directly into the emitters of the transistors not the base of the transistors, this is a Transimpedace amp, true low input impedance (typically 50ohms for the AD844) that current output dacs like the PCM56, TDA1541 and others love to see for low distortion performance.
Cheers George
Attachments
nice
Hhhhhhhmmmm, very interesting stuff....yes I was going to look around here today for Jocko's simple i/v thread and see how that stacks up.I also read that settling time for opamps is very important to sound quality ( Thorsten ? )..is it the ad811 that settles in 25nsec..( it is a single tho )..I think the lm4562 is at least 50 x worse?.
I find it very interesting to TRY and correlate these technical specs to sound quality!
Hhhhhhhmmmm, very interesting stuff....yes I was going to look around here today for Jocko's simple i/v thread and see how that stacks up.I also read that settling time for opamps is very important to sound quality ( Thorsten ? )..is it the ad811 that settles in 25nsec..( it is a single tho )..I think the lm4562 is at least 50 x worse?.
I find it very interesting to TRY and correlate these technical specs to sound quality!
hhhhmmmmm , food for thought... thanx.....those coupling caps must give you nightmares!
actually, I just thought of something ..I built the "Fetishisizator" for my tda1541A dac..it is i/v with a buffer..it has 100ohm input resistors....I wonder if I could adapt that to the ad1955 in the hd970?? 
actually, I just thought of something
..I built the "Fetishisizator" for my tda1541A dac..it is i/v with a buffer..it has 100ohm input resistors....I wonder if I could adapt that to the ad1955 in the hd970?? nice!
...since my last post I have increased the LM4562 class A value to 3.7mA from 1.7mA..a little better in sound quality, tho not as much as from going from virtually zero to 1.7mA.
Also I replaced the ceramic feeback caps (1.5nF ) to 220pF 5% wima wkp..nice improvement across the board..but the biggest change came when I changed the feedback caps to 220pF 1% silver mica...even more black background , more detail and even more musical and what a 3D soundstagel!.
Anyway I am over the moon with the sound I am getting now.and when my tent labs xo arrives ( not holding my breath ) it will be superb.
I can totally recommend this mod to anyone with the hd970 ( altho I have done other extensive mods which all bump up the performance to different levels ( some minor some moderate ).
My only gripe with the player itself, is that it takes an eternity to read discs and also dosnt track very well at all.
...since my last post I have increased the LM4562 class A value to 3.7mA from 1.7mA..a little better in sound quality, tho not as much as from going from virtually zero to 1.7mA.
Also I replaced the ceramic feeback caps (1.5nF ) to 220pF 5% wima wkp..nice improvement across the board..but the biggest change came when I changed the feedback caps to 220pF 1% silver mica...even more black background , more detail and even more musical and what a 3D soundstagel!.
Anyway I am over the moon with the sound I am getting now.and when my tent labs xo arrives ( not holding my breath ) it will be superb.
I can totally recommend this mod to anyone with the hd970 ( altho I have done other extensive mods which all bump up the performance to different levels ( some minor some moderate ).
My only gripe with the player itself, is that it takes an eternity to read discs and also dosnt track very well at all.
Re: nice!
You might want to update the software program for the transport/loader system, PM me your email and I'll send it to you. But do it on your own head and don't ask any questions, as I have never had to do it with all the ones I did mods to, but I know Harman Australia did quite a few and it seamed to fix the problems you are talking about.
Cheers George
Chilli6565 said:[BMy only gripe with the player itself, is that it takes an eternity to read discs and also dosnt track very well at all.
You might want to update the software program for the transport/loader system, PM me your email and I'll send it to you. But do it on your own head and don't ask any questions, as I have never had to do it with all the ones I did mods to, but I know Harman Australia did quite a few and it seamed to fix the problems you are talking about.
Cheers George
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