[smeggy]

I have a 7Mk2, can I just strip it out and rebuild in a bigger case with new transfos as a direct replacement without changing anything else?

 

[krmathis]

Quote:

Originally Posted by pidesd /img/forum/go_quote.gif what lundahl trafos are you using? i d like to put these in my srd-6 (well not actually inside... ) also can you describe how connect them?

Would not be surprised if he use the same transformers as in this project.
the STAX Transformer

 

[spritzer]

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif I have a 7Mk2, can I just strip it out and rebuild in a bigger case with new transfos as a direct replacement without changing anything else?

Yup but you might as well sell it and start off fresh. I got the upgraded SRD-7 Pro bias PCB's yesterday but have to test them to see if all is a-ok. If all is well then I can build one for you. I even added some extra mounting holes to make them easier to use in a non SRD7 configuration.

 

[pidesd]

thanks for the link krmathis! but even though they likely are ll1630 that audiocat is using, i d like to have some kind of approval before i order them. furthermore, i have still no idea if these would be the best bang for my buck, especially with the not THAT high-end lamdas normal bias i plan to buy.

 

[pidesd]

spritzer,

i d really be interested in buying one of your pcb's if you have some spare and if you want to. of course they have to pass the test first. i m not sure about the circuit, but if it is similar to the mk2 one shown earlier in this thread, then i guess i just have to tap the the supply line a bit earlier when it s 230v if i want to feed normal bias phones?

 

[spritzer]

One thing about choosing the correct transformers is to keep the capacity of the windings vanishingly low or you will run into trouble. Almost any OPT will function as a Stax transformer but few are optimized with regards to capacitance.

Quote:

Originally Posted by pidesd /img/forum/go_quote.gif spritzer, i d really be interested in buying one of your pcb's if you have some spare and if you want to. of course they have to pass the test first. i m not sure about the circuit, but if it is similar to the mk2 one shown earlier in this thread, then i guess i just have to tap the the supply line a bit earlier when it s 230v if i want to feed normal bias phones?

It started out life as the SRD-7 Pro supply but has been modified to meet the standard to which Stax designs bias supplies for the Omega lineup. It also has a built in voltage divider (i.e. spots for 3 extra resistors) which allows you to set a second output to what ever voltage you like. The values for 230v and 500v (HE90 bias) configuration are printed on the board.

Once I'm sure that it functions perfectly then I will be selling them at cost.

 

[pidesd]

awesome!

 

[les_garten]

Spritzer,
Do you think that a TOP quality amp like a Krell or Threshold and this Transfo Box would be "better" than a GES, KGSS, BH, etc?

.

 

[pidesd]

if i can permit myself to try an answer...

i dont think it can surpass a dedicated amp as the trafo is an adapter. but my little finger tells me it could come pretty close. but keeping in mind that the goal is to make a stat amp for those who already have a dynamic amp or for those who dont only listen to electrostatics, i think the approach as its merits and the value might be outstanding. i guess only testing will tell...

 

[spritzer]

A transformer will never match a properly designed direct drive amp. There are a number of factors that contribute to this but it's largely due to optimizing the amp for the given task. A speaker amp, driving an odd load through a transformer will always be at a disadvantage.

 

[les_garten]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif A transformer will never match a properly designed direct drive amp. There are a number of factors that contribute to this but it's largely due to optimizing the amp for the given task. A speaker amp, driving an odd load through a transformer will always be at a disadvantage.

Kewl, thanx for the answer, this helps direct my attentions.

.

 

[smeggy]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif Yup but you might as well sell it and start off fresh. I got the upgraded SRD-7 Pro bias PCB's yesterday but have to test them to see if all is a-ok. If all is well then I can build one for you. I even added some extra mounting holes to make them easier to use in a non SRD7 configuration.

can it run pro and normal bias as I use both?

Great work btw, very cool indeed!

 

[spritzer]

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif can it run pro and normal bias as I use both? Great work btw, very cool indeed!

Yup, the pro bias is taken directly off the multiplier and the same goes for the NB, except it is taken through a voltage divider first. Stax just tapped into the multiplier after two stages on the Mk2 bias supplies to get NB but this works better IMO since it is adjustable.

That said a bias supply like this is a compromise since it doesn't have a transformer on the input. That's why I will be designing another one which will be fully isolated for the better transformers.

 

[AudioCats]

Quote:

Originally Posted by krmathis /img/forum/go_quote.gif Would not be surprised if he use the same transformers as in this project. the STAX Transformer

Mine are LL1627, similar turn ratio, larger and heavier.

 

[Victor Chew]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif Mine are LL1627, similar turn ratio, larger and heavier.

How is the performance with the Lunahl?