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Post by cliveastro on Apr 6, 2009 19:15:18 GMT
Having got my WNA MK11 going I would like to do the following mods and are they worthwhile:- 1. The feed back distrubutor 330k pin 2 to 6 2. Zobel Network 3. Increase the quiescent current 4. Change R11 to zero ohm link or 22r resistor.
Lastly I have a 2 channel Cascode PSU is it worth running it as 2 channels and making a second power splitter? Clive
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Post by PinkFloyd on Apr 6, 2009 21:13:37 GMT
Having got my WNA MK11 going I would like to do the following mods and are they worthwhile:- 1. The feed back distrubutor 330k pin 2 to 6 2. Zobel Network 3. Increase the quiescent current 4. Change R11 to zero ohm link or 22r resistor. Lastly I have a 2 channel Cascode PSU is it worth running it as 2 channels and making a second power splitter? Clive Zobel network is a waste of time, forget it. Fit zero ohm links at R11, increase the QC.... all good.... the FBD adds a touch of "warmth" to the SQ though you can get this by binning that LM6171 and fitting AD843 instead. With AD843 you can also dispense with the input / output caps. I REALLY don't like the LM6171 in this amp, it causes more problems than it solves.... David White got a job lot of them which is why he supplied them with the kit..... not a good reason to use them...... I know this cause I came within a whisker of buying the WNA business! Seriously man, you are a lot better going down the AD-843 route.... the amp is a lot more stable with them in circuit.... you'll only need two and can fit something like OPA602 / OPA132 / 134 in the rail splitter. I've got a truckload of chips here so if you are stuck let me know and I'll sort something out for you. Mike.
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Post by cliveastro on Apr 7, 2009 7:34:45 GMT
Hi Mike Thanks for the reply. I think I have a couple of AD843s, will it work without removing I guess C1,5 @ 6? Have you tried or do you know of anyone who has added a Cascode PSU. How long is the burn in time? Mine works OK but with HD650s I dont get the zing of the cymbals like I do with my full HiFi. Regards Clive
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FritzS
Been here a while!
Sound of Blue Danube
Sound of Blue Danube
Posts: 1,364
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Post by FritzS on Apr 19, 2009 16:42:11 GMT
Hi Mike Thanks for the reply. I think I have a couple of AD843s, will it work without removing I guess C1,5 @ 6? Have you tried or do you know of anyone who has added a Cascode PSU. How long is the burn in time? Mine works OK but with HD650s I dont get the zing of the cymbals like I do with my full HiFi. Regards Clive Hi Clive, I use a WNA MKII to - the WNA HA controls the deep bass more with my Denon HA-D7000 as Solo. Today I use AD843 for amp and LM6171 in the railsplitter. I tested many of the current OPA's with the WNA MKII. PSU is the original SM-PSU. More about my mods and test's please see on my homepage www.stockhammer.eu/hifi/wna-main.phpSolo and WNA-MKII are on the same level, with AKG K701 Solo sounds a little bit brighter. With the D7000 there are no hearable / replicable differences, only the bass ... ... the zing of the cymbals sound very well with my mods in WNA MKII
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Post by cliveastro on Apr 28, 2009 19:58:35 GMT
Hi Sorry for the long delay in replying I have been away. I have just tried a different angle, I have made a new cable for my HD650's. The cable is 7/0.12 silver coated wire with a PTFE sleeve. I used 4 wires per channel 2+ 2- and Litz braided them (8 wires total) and Cardas plugs and a Neutric connector. Certainly made the HD650s a bit more zingy.
Clive
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Post by cliveastro on May 20, 2009 20:16:37 GMT
So after a long delay, last night I did a couple of the mods. I swapped out the LM6171's and replaced with AD843's and swapped the R11's with zero ohm links. I am now totally sold on the AD843's they are rounder. cleaner with a bit more bite. After the 843's have bedded in I will do the quiescent current mod. Later I will change the PSU.
Clive
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FritzS
Been here a while!
Sound of Blue Danube
Sound of Blue Danube
Posts: 1,364
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Post by FritzS on Apr 8, 2010 8:19:51 GMT
Hi, I will make some little mods around the output stage of my WNA MKII as look like the MKIII diamond star .... MKIII use here PNP/NPN (MPSA92/MPSA42) BJT's instead of the the both 1N4148 two 120R resistors - I will use Vishay MBB/SMA 0207 resistors all current source are 3.5 mA additional feedback 330k resistor between pin 6 and 2 of the OPA I have all schemas, if you want, please send me a PM Link to schema (after further inquiry to Mike) rockgrotto.proboards.com/index.cgi?action=display&board=modmodmod&thread=5313
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FritzS
Been here a while!
Sound of Blue Danube
Sound of Blue Danube
Posts: 1,364
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Post by FritzS on Apr 10, 2010 17:04:57 GMT
now I draw the mods with ExpressSCH (running under Crossover). MKIII use here PNP/NPN (MPSA92/MPSA42) BJT's instead of the the both 1N4148 I will use MPSA 06G - TO92 NPN / MPSA 56G - TO92 PNP or BC 548B - TO92 NPN / BC 558B - TO92 PNP two 121R resistors - I will use Vishay MBB/SMA 0207 resistors all current source are 3.5 mA additional feedback 330k resistor between pin 6 and 2 of the OPA optionally bypassed with a cap 10pF .... 40pF and experinent with the ferrite bead or a 47 ... 100 Ohm resistor
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