[aurelius]

Philip,

I keep coming back to the VH teflon caps for the tweeter. They have sparkle. I've tried stock, PPS and sonicaps.

I take it you are using the VH caps on your AKSAs and not in the active crossover?

Grumpy, we raffle chooks (chickens) over here... having an apartment raffle would be a novel change...

Hugh, thanks...

[PT914]

Peter and Mark,

Sorry for the mix up.  I have VH caps in the Orion ASP tweeter segment, I believe its the .033 caps.  VH did a 2% hand sort.  The only problem was the burn in time, 200 to 400 hours.  I only noticed how good it was when I recently replaced them with sonicaps.  They are back in now.

I also have VH caps as output caps on the 25N+.  These are also in the .03 uf range.

Philip

[MikeC]

3. Re. "replacing OPA2134s with AD826s", a fella called "DVV" who posts here occasionally has written a comparison of quite a few op-amps on his web-site and the AD826 came out tops. So that's what I used in my Rod Elliott-designed L-R active crossovers.

have you got a link to his website?

Here it is http://www.zero-distortion.com/start.htm

This seems to have drifted into an AKSA / Orion thread

I am also slowly putting together an Orion system - slowed somewhat further by now having to put the entire system together from scratch (new AKSA 100N+, 55N+ & 21N+ with GK-1). I went with the OPA's to start with, but I may upgrade to AD826's later. I am worried by the output offset the AD's have, especially when cascading stages, which is why I started with the OPA's. If anyone succesfully used the AD 826 in the Orion crossover, please let me know. DVV suggests using a small diode from output to negative supply to cancel out the offset, if someone is willing to experiment.

I also have an upgraded power supply, regulated at 15V rather than SL's recommended 12V (the op-amps are speced to perform best at 15V, so why a 12V PS is recommended is a mystery). I have also upgraded most of the caps to PPS types where I could get the correct values, plus added some silver micas and BG's where applicable, although SL's recommended caps are reasonable. I also put additional tantalums across each op-amps supply rails as recommended by DVV.

I agonised over a tweeter coupling cap, before letting both Hugh and SL reassure me that it was not necessary. I did calculate the required cap to be huge (74uF or larger as I just calculated it if my maths is correct) as the filter knee should be at least two or more octaves below the tweeter HP knee (circa 360Hz or lower). If using a good quality cap (or multiple caps, 'cos there aint no 74uF teflons around), the protection would cost more than the replacement tweeter.

I also built up a 100W amp to run the woofers, also with 42 volt rails, but I also modded the power supply with an additional pair of caps per channel and upgraded the rectifiers to cope with the current draw. All the amps are using Schottky diodes in the PS.

When I finish, I will post how it sounds. Don't ask for comparisons on any of the mods though, because there is no reference at the moment. This is a clean sheet hi-fi system - I don't even have a CD player yet.

Cheers

Mike

[aurelius]

This is way off topic now, but I'm not sure why AD826's should be different to OP2134's in terms of their DC characteristics... both have max input offset voltages of 2mV.  Input Offset x DC gain = output offset.  In terms of accumulating offset over cascading stages, only 3 blocks of the Orion crossovers have DC gain; they are the 20-110 SLP [15dB] and 20-305 SLP [24dB] section in the woofer path only, and the 30-400 SLP [22dB] in the midrange path only(from memory).

So in reality, only the woofer path has cascading stages with DC gain.  Working this through, the output of the second SLP in the woofer path could have, worst case 168mV offset, which would not even cause the diode to conduct.

I may be wrong?

Having said all this, Blizzard PMed me (sorry, I have not responded yet) suggesting that the AD's have caused oscillation in his case.

[PT914]

Just realized my mistake, the 25N+ does not have output caps.  That's why I'm confusing people.  Guess I haven't worked on the amps in awhile cuz I'm very satisfied with them.  They reveal every change up front.
They are not the limiting factor in my system  They only have input caps and that is where the VH caps are.  My thoughts are on output caps because I'm working a GK-1.

Sorry,
Philip