[coinmaster]

Then there is coinmaster's version of the impedance mod using the 10M45S parts

Two different mods, the 10M45S are an improved version of the "driver bias" mod.

Although to have the ultimate upgrade to the driver stage you'd have to include a mu follower in place of the load resistors along with the 10M45S mod which is easy enough for anyone that wants to do it, I'd be happy to show you how, but I won't hold my breath. It seems like enthusiasm has waned for the MK6 mods.

The Improved "impedance mod" is a different beast.

which better matches the impedance to a whole lot of headphones at once I believe.

The impedance mod doesn't match the impedance to a single headphone or lots of headphones per se. The WCF topology can only be optimized for a single load impedance in which the current sharing between both triodes are equal.
Unless you are using planar headphones this means that the existing impedance mod will not work throughout the entire frequency range, the goal of the existing impedance mod is to find the a sweet spot to try to hit as many frequencies at once as it can but dynamic headphones have varying impedance with frequency so it will never be optimal.
My improved impedance mod does a few things at once, it gives a lot better PSRR, lowers the input capacitance, and keeps the current through both triodes balanced no matter what the load is.
The end result being less loading on the input stage as well as improved sound throughout the entire frequency range.

 

[gug42]

Hello,

Thank you for thoses explanation.
Indeed The switch mode is to adapt the bias point of the push pull to the charge.

So well i understand it could be really interesting to do it ... But i don't have the knowledge to do the math and calculation....

Lucky i m mainly use a planar of 50 ohms, a zmf. If you say the value of the resistor to use i will do the mod

When i receive the tube I can post some picture. 5998A are electricaly identical to 5998. 7236 are a little different.
http://tubedata.milbert.com/sheets/127/5/5998A.pdf

Regards

 

[baronbeehive]

Two different mods, the 10M45S are an improved version of the "driver bias" mod.

Although to have the ultimate upgrade to the driver stage you'd have to include a mu follower in place of the load resistors along with the 10M45S mod which is easy enough for anyone that wants to do it, I'd be happy to show you how, but I won't hold my breath. It seems like enthusiasm has waned for the MK6 mods.
......

I wouldn't say that, I think everybody is just taking stock atm and enjoying the results of their work, like I'm doing with my other amp.

I'm still interested in the mods but not in any position to do anything for a while. Also I'm not too familiar with the sound of the modded LD because I've only had it up and running for a short while, so I would need to re acquaint myself with it first. But I would certainly be interested in trying out your mods. I would like to see something along the lines of the first page with each mod, its purpose, what parts are needed and how to do it and the expected results. We could maybe take it from there and do the necessary testing to flesh out any problems?

.....

The Improved "impedance mod" is a different beast.

The impedance mod doesn't match the impedance to a single headphone or lots of headphones per se. The WCF topology can only be optimized for a single load impedance in which the current sharing between both triodes are equal.
Unless you are using planar headphones this means that the existing impedance mod will not work throughout the entire frequency range, the goal of the existing impedance mod is to find the a sweet spot to try to hit as many frequencies at once as it can but dynamic headphones have varying impedance with frequency so it will never be optimal.
My improved impedance mod does a few things at once, it gives a lot better PSRR, lowers the input capacitance, and keeps the current through both triodes balanced no matter what the load is.
The end result being less loading on the input stage as well as improved sound throughout the entire frequency range.

Right! I can see that keeping the current through both triodes balanced would help with the problem of varying impedance when using a range of dynamic headphones, if it does do this it should be interesting trying that out!

 

[coinmaster]

Right! I can see that keeping the current through both triodes balanced would help with the problem of varying impedance when using a range of dynamic headphones, if it does do this it should be interesting trying that out!

Keeping the current sharing between balanced doesn't help the issue of varying impedance in dynamic headphones, it's the other way around, the varying impedance of dynamic headphones breaks or weakens the push pull operation of the WCF at frequencies it is not optimized for.
In other words my mod ensures proper push pull operation regardless of the load, while the existing impedance mod only tries to find a sweet spot for your particular headphones so it can attempt to maintain push pull at at many frequencies as it can.

 

[gug42]

Oh really interesting indeed !
Ok i will read some post back to know what soldering where

 

[gug42]

Hello,

What could be the most size effective capacitor for 0,47uF / 250V ?
Any advice on this site please ? https://www.hificollective.co.uk/catalog/components/capacitors.html

For the power/driver coupling caps I will go with the big/large and expensive jupiter PIO because they are the best !

But for the WCF power tube coupling cap I can't spend so much ... and I'm concern by the place left in the boxe ... Perphaps I go with K75-10 250V 0,47uF ... really cost effective .... ?



Regards,

 

[coinmaster]

The optimal capacitor size would be about 2uf all around. Just buy the biggest size you're comfortable with with the highest quality capacitor you can afford. Don't get too obsessed over the details.

 

[gug42]

Yes aggree about details
Indeed my concern is related to physical size for 0,47uF / 250V

 

[baronbeehive]

Hello,

What could be the most size effective capacitor for 0,47uF / 250V ?
Any advice on this site please ? https://www.hificollective.co.uk/catalog/components/capacitors.html

For the power/driver coupling caps I will go with the big/large and expensive jupiter PIO because they are the best !

But for the WCF power tube coupling cap I can't spend so much ... and I'm concern by the place left in the boxe ... Perphaps I go with K75-10 250V 0,47uF ... really cost effective .... ?



Regards,

Yes, these are the ones we used from hificollective: https://www.hificollective.co.uk/catalog/jcw080-047uf-600vdc-jupiter-copper-foil-paper-p-9973.html
They are 21x52mm and if in doubt check out the ones we have used in the compact version of the mods on page 1 because then you know they fit OK.
The K75-10 should be fine, I'm not sure of size but they look like they will fit OK.

 

[gug42]

Hello I was looking for the WCF coupling cap between the power tubes.
Because physically place will be important indeed

So well What do you think about thoses one :
https://www.hificollective.co.uk/catalog/jcw080-047uf-600vdc-jupiter-copper-foil-paper-p-9973.html

 

[coinmaster]

I never actually implemented the WCF cap upgrade, how does it sound?

 

[baronbeehive]

The compact version used Mundorf MCap Supreme Silver/Oil 0.33uF 1000V but you could try the ordinary Mundorf Supreme if you wanted a cheaper cap.

I don't know how it sounded because I did all the mods at once, all I know is that Maxx really went for the Mundorf SiO as the best WCF replacements with a really strong treble sound.

Edit:
Please let me have quoted Maxx correctly lol!

 

[gug42]

I never actually implemented the WCF cap upgrade, how does it sound?

Redge tell me that is a really important upgrade for sound quality, ahead Bypass cap and coupling cap.
For Redge the order are :
- 5998A bias mod
- Output impedance bias mod adapted for the headphones (but to hard for me ! so I will not do it )
- Coupling cap between
- WCF cap inside the power stage (between power tubes)
- Bypass cap
- Decoupling cap on the power tubes (I will not do this one)

The compact version used Mundorf MCap Supreme Silver/Oil 0.33uF 1000V but you could try the ordinary Mundorf Supreme if you wanted a cheaper cap.

I don't know how it sounded because I did all the mods at once, all I know is that Maxx really went for the Mundorf SiO as the best WCF replacements with a really strong treble sound.

Well I'm looking mainly by a soft/mellow/laid back trebble. So I don't know how to understant your stance .... perhaps K75-10 will be a really good choice.

Thank you evryone ! Tomorrow i will post my shopping list

 

[coinmaster]

Redge tell me that

Redge is still alive?

 

[baronbeehive]

......

Well I'm looking mainly by a soft/mellow/laid back trebble. So I don't know how to understant your stance .... perhaps K75-10 will be a really good choice.

Thank you evryone ! Tomorrow i will post my shopping list

BTW have you seen this: http://www.humblehomemadehifi.com/Cap.html
It may help you make up your mind about caps.

Redge is still alive?

Redge???...... who????