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New! WNA MKll Head-amp kit. - Page 7

post #91 of 760
2/14/05 at 7:18pm
Thread Starter 
Quote:
Originally Posted by biovizier
I am going to be swapping in the LM6181 all the way through my volco and phono - Dr White seems to be of the opinion the the LM6181 is superior also.
It's not "superior" per se ....... it's similar to the LM6171 but different in many ways (how's that for an oxymoron!) Some may like the clinical, fast, unforgiving and microscopic insight that is the LM6171 whilst others may like the same qualities with a touch of emotion and soul... if so the LM6181 is the order of the day...... neither of them is superior to one another they just do things in a different way.....

One difference I have noticed between the MKl and MKll is the space and inky black silence between instruments the MKll brings about...... the sound is so clean you can pump frightening levels into your eardrums and not even realise how loud it is....... this is a sign of a quality amp.... The additional decoupling probably accounts for this........ every instrument has air around it and distortion cannot be heard (probably cause there's no distortion to be heard) even the most maniacal crescendos are easy on the ear, even at very high levels.

I, originally, thought this was something to do with the setting of the gain but.... No. This amp gives you the music, the whole music and nothing but the music, hearing is believing and I urge you to have a listen to the WNA....... you'll never look back I can guarantee it.

Class on a stick.

revised:

MKl: 9 / 10
MKll: 11 / 10
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post #92 of 760
2/14/05 at 7:25pm
Thread Starter 
Meant to add,

Had a conversation with Dr. White earlier and LM6181 will now supersede the LM6171 in all Head-Amp kits.

All the best.

Mike.
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post #93 of 760
2/15/05 at 5:28am
I've ordered my LM6181 today (cheque's in the post). Build should be pretty much complete by the end of this weekend (barring domestic life intruding into build time again ).
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post #94 of 760
2/15/05 at 11:41am

LM6181

Steady on! The LM6181 takes about a week (at least) to bed in ... plus the wna mk II was specifically designed around the LM6171. If the next version is designed around the LM6181 - which is CFB and therefore has different characteristics - then the improvement may become unequivocable. The two chips are not being compared on a level playing field as yet. ;-) I am using LM6171 in my volco and will swap them out for LM6181 in the next few weeks - that may actually give a fairer comparison as the balanced module is not optimised for either chip yet. Certainly there is room for improvement on the lm6171 given my comparisons with the ad825. Which headphones are you using and which source with the WNA headamp? I suggest if possible you try to vary these factors as well to see how that changes the perspective on the relative merits of each chip - given that no source / sink is perfect then it's prudent to check that it is not a limiting factor on the comparison. I only have one vinyl source unfortunately so I wil be interested to hear your results. Have you tested with cd source only or also with vinyl?
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post #95 of 760
2/15/05 at 12:18pm
Thread Starter 
Quote:
Originally Posted by biovizier
Steady on!


Quote:
Originally Posted by biovizier
The LM6181 takes about a week (at least) to bed in ... plus the wna mk II was specifically designed around the LM6171.
MKll is in effect a MKl the only difference being extra decoupling. The MKl was designed around the OPA134 / OPA627 breed of chips. The circuit only needed minor modification to get the LM6171 to operate optimally in the circuit and these modifications included biasing the opamp into class A (changed I2 from a 3.5mA to a 5.6mA constant current diode and changed R6 from 120R to 75R resistor) replaced R4 with a zero ohm link and fitted output caps...... as easy as that.

As I say, the MKll is essentially a MKl with added decoupling..... to optimise the MKll circuit for the LM6181 simply involves scaling down the gain setting resistors so that the feedback resistor (between o/p and inverting input) is 1k. This means that if the feedback resistor was 3.3k and the resistor from inverting input to ground was 1k (for gain of 4.7), you would have to scale the 3.3k down to 1k, and the 1k down to 300R (or nearest preferred value) to keep the ratio the same...... this has been done.

Quote:
Originally Posted by PinkFloyd
Had a conversation with Dr. White earlier and LM6181 will now supersede the LM6171 in all Head-Amp kits.

Quote:
Originally Posted by biovizier
If the next version is designed around the LM6181 - which is CFB and therefore has different characteristics - then the improvement may become unequivocable.
The circuit has been optimised for the LM6181 as above


Quote:
Originally Posted by biovizier
Which headphones are you using and which source with the WNA headamp?
Headphones:
Sennheiser HD-600
Grado SR-60
AKG K-501

Sources:
Marantz CD-17 ki signature
Denon DCD-835


Quote:
Originally Posted by biovizier
I suggest if possible you try to vary these factors as well to see how that changes the perspective on the relative merits of each chip - given that no source / sink is perfect then it's prudent to check that it is not a limiting factor on the comparison. I only have one vinyl source unfortunately so I wil be interested to hear your results. Have you tested with cd source only or also with vinyl?
I've only listened with CD as a source (both Marantz and Denon) and through 3 different pairs of headphones, both LM6171 and LM6181 kick ass whatever combo I use....

Mike.

Edit: Just out of interest Biovizier, do you own a WNA MKll head-amp?
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post #96 of 760
2/15/05 at 12:48pm

LM6181

All of the previous chips are vfb - perhaps a cfb chip will open up whole new research vistas for the next iteration! Tailoring can involve fundamental design changes as well as just changing a few resistor values. Also - give it a chance to wear in! The LM6171 didnt reach its potential for well over a week of constant use and continued to improve for at least 2. Which areas do you think the LM6171 still has the edge in and how are they changing over time now?

Also, some other change or addition may be made that will suddenly reveal that a limitation lay elsewhere in the unit, or that two aspects were compensating for each other and this could lead to a reappraisal. Certainly the fact that the LM6181 sounds faster then the LM6171 in combination with a couple of things that are "in development" is of particular interest to me. There is likely a limit I have discovered elsewhere that when rectified might suddenly reveal that the performance advanatage of the LM6181 was much greater than previously imagined but was obscured by a bottleneck. OR maybe not. Or it may be that CD only listening biases the results (i.e. OPA627 makes a bright cd player sound palatable but is a pretty naff sounding op-amp otherwise). I have to determine all the unknowns to make the correct choice.
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post #97 of 760
2/15/05 at 12:50pm
Edit: I have the wna phono and "preamp" but I may also be purchasing the headamp soon. In addition I may use the buffer amp in the preamp (which is the basis for the preamp and the headphone amp). So it's still relevent. Just about.
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post #98 of 760
2/15/05 at 1:01pm
Thread Starter 
Quote:
Originally Posted by biovizier
Edit: I have the wna phono and "preamp" but I may also be purchasing the headamp soon. In addition I may use the buffer amp in the preamp (which is the basis for the preamp and the headphone amp). So it's still relevent. Just about.
As soon as you get the WNA head-amp I'll be interested to hear what you think of it Nick. I've been listening to head-amps for many years and have been heavily involved with the WNA head-amp for the best part of a year now (have a read through the original WNA thread).

I really appraciate your input re: the LM6181 but, with respect, I don't need to be told how to evaluate an opamp.... the LM6181 has been burning in for about 120 hours (with music playing) and that's enough time to establish whether it's a keeper or a throwaway.... It's good, not miles better than the LM6171 but different... I like it and will continue using it.... whether others will like it, well I'll let "their" ears decide. They're only £2.50 a pop so it won't break the bank rolling a couple in for a try.

Cheers

Mike.
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post #99 of 760
2/15/05 at 1:05pm
Thread Starter 
Quote:
Originally Posted by biovizier
Which areas do you think the LM6171 still has the edge in and how are they changing over time now?
I didn't say it had the edge..... read a few lines up

Quote:
Originally Posted by PinkFloyd
It's not "superior" per se ....... it's similar to the LM6171 but different in many ways (how's that for an oxymoron!) Some may like the clinical, fast, unforgiving and microscopic insight that is the LM6171 whilst others may like the same qualities with a touch of emotion and soul... if so the LM6181 is the order of the day...... neither of them is superior to one another they just do things in a different way.....

Quote:
Originally Posted by biovizier
I have to determine all the unknowns to make the correct choice.
You'll only manage that by buying a WNA head-amp and using your ears
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post #100 of 760
2/15/05 at 1:08pm

LM6181

I just think the LM6171 has a few issues and your findings seem to be different - just curious why that might be. Dont take it personally I am not casting aspersions on your op-amp assessment - just trying to determine the differences. They might be in my setup and need to be addressed. Rigourously!
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post #101 of 760
2/15/05 at 1:15pm

LM6181

I surely will but I am waiting to sort the phono and preamp first - otherwise upstream components will muddy the waters. The same types of tweaks and concepts are used. As I said the preamp and headphone amp are derived from (or even identical - not sure) the same circuit so whats good for one is good for the other. They are directly comparable so by finalising the preamp using the buffer amp I will have also then have finalised my headamp.
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post #102 of 760
2/15/05 at 1:22pm
Thread Starter 
Quote:
Originally Posted by biovizier
I just think the LM6171 has a few issues and your findings seem to be different - just curious why that might be. Dont take it personally I am not casting aspersions on your op-amp assessment - just trying to determine the differences. They might be in my setup and need to be addressed. Rigourously!
I'm not taking it personally Nick but this thread is about the WNA MKll head-amp..... The LM6171 may sound completely different in your application and I can only comment on how a chip sounds in the WNA head-amp. I suggest my findings may be different to yours as I am listening to the head-amp and you are not, you're probably listening through loudspeakers?

I've covered the attributes of the LM6171 "extensively" in the original WNA thread I'm not repeating myself over and over again so have a glance through that thread.... there's plenty there.

I'll obviously go into a lot more detail re: the attributes of the LM6181 after say 500 hours but, as it stands, my initial appraisal is "it does what the LM6171 does though it's slightly faster with a bit more warmth, soul and emotion"

I'll expand on that statement if there are any major changes after 500 hours.

All the best.

Mike.
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post #103 of 760
2/15/05 at 1:35pm

LM6181

I look forward to hearing your findings
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post #104 of 760
2/15/05 at 8:20pm
Thread Starter 
Quote:
Originally Posted by biovizier
I look forward to hearing your findings
I look forward to presenting them
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post #105 of 760
2/19/05 at 3:58pm
Well. the progress on my Mk2 has been a little slower than I'd have liked. I started to populate the PCB last weekend but family and domestic obligations, coupled with a sudden desire to use LM6181s (which I didn't have) halted progress until today. The LM6181s and required resistors for the op-amp change arrived in the post this morning (thanks David!) so I intended to complete at least the PCB and hopefully the whole amp. Well, I got the PCB finished, but a knock at the door turned out to be a friend from Inverness who I hadn't seen for a year, so that kyboshed any further progress. I'll try again tomorrow.

Anyway, the PCB is as well made and easy to populate as the original Mk1 (that's very easy), although getting a satisfactory result hooking up wires between the rail-splitter and the PSU inputs for the amplifier channels took a few attempts until I was happy. It would have been easier had I bought enough pin headers to cover this requirement, but I'm a cheapskate and didn't. To prove my progess, here are a couple of quick (read poorly taken) photo's showing the populated board and the PSU earth hook-up wires tacked to the underside of the PCB. More progress will be reported when I make any. (Please note that the PCB hasn't been cleaned yet).



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