[StevieDvd]

The bypass option has been done on the Xin Supermacro and there's probable a list of opamps on Xin's forum which have the bypass (not all do).


the next trick was to use both the bypass and to class A the opamp which needed a simple resistor bridge between 2 pins. Again only certain opamps were fit for this.

 

[FritzS]

Quote:

Originally Posted by StevieDvd the next trick was to use both the bypass and to class A the opamp which needed a simple resistor bridge between 2 pins. Again only certain opamps were fit for this.

You mean OP's as NE5534, SA5534, SE5534?

Another way use a current source diode (1mA ... 2mA) between output and -V if this feature isn't integrated in the power stage (as in WNA MKII).

 

[StevieDvd]

Quote:

Originally Posted by FritzS You mean OP's as NE5534, SA5534, SE5534? Another way use a current source diode (1mA ... 2mA) between output and -V if this feature isn't integrated in the power stage (as in WNA MKII).

yep as well as AD829, AD8021 & LT1115 when I eventually found the thread over at Xin's forum here

Not sure about the diode option that's getting to techie for me and I have a mk1 WNA.

I wonder just how many WNA amps are actually out there!

Steve

 

[AntiGeek]

Hello

This is my first post so please forgive me for going off topic. I have just constructed a Super Cascode power supply for my WNA MK2 headphone amp and was just wondering how to best connect it up for maximum sound quality.

I have tried to follow the printed construction manual however this left more questions unanswered that answered.

As can be seen from the pics, i have tried to set up the PSU so both power output channels are connected in series.

Basically my problem is that no matter what toroidal transformer secondaries I use (at the moment blue & yellow), quite abit of heat is emmitted from the output heatsinks and the AD843 chips.

Is this normal or is it something to do with the sensor lines (pretty much left a mystery in the manual) not being connected to the headphone amp??

Sound quality through the headphone amp is vastly improved howvever I am really worried by this heat issue especially to the AD843 chips.

I have scanned the Cascode Instruction manual & Headphone amps MK2 & MK3 onto word documents if anybody wants these.

This is a great forum.

Many thanks in advance for any help.

 

[PinkFloyd]

AD-843 runs warm / hot, Normal. BD139 / 140 run hot, Normal.

You can dispense with those blackgate output caps, your amp will sound a lot better without them in the signal path. DC offset from the 843 should be <8mV so you're safe to remove them. Of course check the offset first.

Mike.

Quote:

Sound quality through the headphone amp is vastly improved howvever I am really worried by this heat issue especially to the AD843 chips.

This post may help you. Note I was running the amp with increased quiescent current so the temps were even higher.

 

[AntiGeek]

Hi Mike

Many thanks for the swift response. Sorry for the confusion but I was actually referring to the AD843 and heatsinks in the Super Cascode PSU. I have not yet played around with the headphone amps OP amps (still stock LM6171s).

I reckon both the AD843 chips and heatsinks in cascode are about 60c (they heat up in less than a couple of minutes from switch on).

All the soldering appears OK and the thing does make the headphone amp sound a hell of a lot better.

I know you have a built mk3 (I have yet to build mine though have got the pcb.)

Unfortunely I don't have a test meter (the one I brought off Ebay was totalled!!).

Would you like to borrow the Super Cascode to test with your MK3 and check out how it sounds??

I did ask doctor White about how to set up the Super Cascode and he sent me the below:

"You use the 24V tappings on the transformer and configure the super csacode for independent 24V outputs. You only need to use one channel, leaving one spare. You still need to leave out one of the IC2 lm6171s on the MkIII headphone amp. Connect the P4s of each channel in parallel and then connect P4 +v to +v/+s on the cascode and P4 -v to -v/-s on the same cascode channel. You can't use one psu channel to power one headphone amp channel and the other psu channel to power the other headphone amp channel unless you have a system which is isolated dual mono throughout - usually difficult/impossible to arrange. The only other psu option is to use two super cascodes, one for each headphone amp channel, but bypassing the rail splitter/capacitance multipliers on the headphone amp pcb.
I can still supply spares/components in cases of dire necessity.

Regards, David"

"Hi John,
I misled you about using a super cascode with the MkIII headphone amplifier. I'd got so hung up on making sure that customers with the standard switch mode psu didn't blow up their headphone amps that I shut my mind to the other possibilities. If you use a cascode or super cascode psu configured to give two independent 24Vdc outputs then you can use each output to power one headphone amp channel separately via its P4 connector. In this case you need to insert LM6171s in both IC2 positions. I hooked up a system to check this out this afternoon. It works fine and makes a really worthwhile improvement - I heard small details on my test CD ( a Byrds compilation ) that I'd never heard before.

Regards, David"

Once again many thanks for your help and swift reply.

John

 

[PinkFloyd]

Quote:

Originally Posted by AntiGeek Would you like to borrow the Super Cascode to test with your MK3 and check out how it sounds??

Hi John,

I really don't want anything to do with the super cascode or MKlll as they were rushed designs and I think David White is making up most of his answers to "build problems" as he goes along. The best person to contact would be David White himself

First question is "why" are you using the 843 in the super cascode? is that the stock opamp for it? 60C sounds about right to me (for both the transistors and 843) and you'd be OK leaving them naked. You could, if you want, fit heatsinks and that would assist in dissipating any heat........ perfectly normal for these components to get hot to the touch so don't worry about that John.

All the best.

Mike.

 

[AntiGeek]

Hello again Mike

Yes the PSU comes stock with AD843s. Apparently they balance low noise with dynamics.

Below is the explanation given:

"The regulator error amplifier is an op-amp and the device chosen, the AD843, gives best all round performance. The AD825, on a surface mount to dil8 adaptor, performs equally well but is marginally less convenient to use. Lower noise can be achieved by using op-amps such as the AD797 or LT1028, whilst better dynamic performance can be had with the LM6171 or AD817. All nasties, such as noise and ripple, on the output of the Super Cascode power supply are at least l00dB down."

Neither the Amp nor PSU has gone up in smoke so I assume they might be working ok. As far as heatsinks go, its abit of a tight fit as they will short if they come into contact. For the AD843s I May try getting and dremeling some of the chip heatsinks that computer overclockers use on their memory chips. When thermal pasted on they may improve heat dissipation a little.Maybe!!

I agree with you about the MK3 being a rushed design though the Super Cascode seems like a fairly sound bit of design.

Everything played through the headphone amp especially sax and female vocals really does sound far cleaner and like several veils have been removed from the performance. As the cascode has two totally separate channels, I may try feeding each channel direct into each of the P3s of the headphone amp.

I may still build the MK3 when I can track down a supplier of all the welwyn resister values required.

Is your new heed amp any better than the WNA mk1 & MK3??

Many thanks for for your help.

John.

 

[FritzS]

Quote:

Originally Posted by AntiGeek I may still build the MK3 when I can track down a supplier of all the welwyn resister values required.

Try http://www.farnellinone.com/ and
http://www.rs-components.at/
http://www.rs-components.com/
both have welwyn resistors

Quote:

Originally Posted by AntiGeek Is your new heed amp any better than the WNA mk1 & MK3??

I have MKII with AD843 now
http://www.stockhammer.eu/hifi/wna.php
http://www.blue-danube.at/

My experience about AD843 please read here
http://rockgrotto.proboards39.com/in...ead=1146567048

 

[FritzS]

Hi,
gives a new Super Cascode and WNA MKlll PCB source?
David has closed his shop and did not answer

But some have schemas and photos about ......

 

[PinkFloyd]

Quote:

Originally Posted by AntiGeek Yes the PSU comes stock with AD843s. Apparently they balance low noise with dynamics.

Oh, he finally agrees with me that the 843 kicks the LM6171's arse then

 

[AntiGeek]

Hi Fritzs/Mike

Try http://www.farnellinone.com/ and
http://www.rs-components.at/
http://www.rs-components.com/
both have welwyn resistors

Yes Fritzs, I have tried most of these +Maplins and Rapid.

Can't seen to find 100ohm or 120ohm anywhere. Is there another make of resistor available which would do as good/better job?

Hi,
gives a new Super Cascode and WNA MKlll PCB source?
David has closed his shop and did not answer

But some have schemas and photos about

Unfortunetly/fortunetly not. I got my MK3 & Super Cascode shortly before Dr White closed up shop.

If you need them, I can email you the construction manuals in word doc for both & realsize scans of both sides of the MK3 board.

Oh, he finally agrees with me that the 843 kicks the LM6171's arse then

Would it be worth trying these AD843s in place of the LM6171s in my mk2. Would the sound be noticebly improved especially with the removal of the blackGates??

Many thanks for all your help

John.

 

[PinkFloyd]

The resistors you want are 25 pence each. They are exactly the same as the Welwyn RC55Y.

Most definitely worth trying the AD-843 and, yes, you can dispense with the output caps completely. You could swap the 843 that's in your PSU into the amp and the LM6171 that's in the amp into the PSU and give them a listen.

I prefer the 843, I think Fritz likes it too?

Over to you Fritz...................

 

[FritzS]

Quote:

Originally Posted by AntiGeek Hi Fritzs/Mike Try http://www.farnellinone.com/ and http://www.rs-components.at/ http://www.rs-components.com/ both have welwyn resistors Yes Fritzs, I have tried most of these +Maplins and Rapid. Can't seen to find 100ohm or 120ohm anywhere. Is there another make of resistor available which would do as good/better job?

http://www.farnellinone.com/
welwyn RC55C 0,25W 0.5%
9497978 100R RESISTOR, 0.25W 0.5%
9498079 121R RESISTOR, 0.25W 0.5%

or Dale - but they are hard to get in Europe, till now I did not found - but some DIY's tells one of the Dale resistors familie are "superp audiophile high end"

 

[AntiGeek]

Mike/Fritzs

Many thanks for the details on suitable resistor suppliers. Shall now be able to get on with my mk3 build.

Shall leave testing AD843s until mk3 is built as I have rather stupidly soldered the lm6171s direct to the mk2 pcb.

Anyhow it leaves me with a nice build project to get stuck into.!!

Regards

John