Pre-amp Nirvana ?
- Thread starter Mr Tibbs
- Start date
Jo Sharp
Pulls on doors marked push
This is exactly what the Starfish pre-amp does when running in symmetric configuration.
That's fine as far as the 24V rails go, but you cannot configure the 0V rails as described above unless they are separate to begin with. I'll lash a drawing up later.
I actually did try this on a 42 preamp, using eight PP3s to give four separate 18V 'power supplies". It beat the same preamp fed with the 0V lines hooked up in conventional manner at the star 0V point.
Conventional method of connection:
Same PS but with 0V lines connected at each respective stage:
The alternative method has no power supply current flowing in the preamp star 0V system - that's the key to the improved performance this method brings.
Mr Tibbs
Hi Mr. Tibbs, I am sorry I have to revive this old thread but it seems your pictures are not working properly any more and I have two questions, please?
Q1: I use local ALWSRegs inside my NAC and each Reg has "In-Ground" and "Out-Ground". Do I use the Out-GNDs to connect to each pre-amp stages or like with your split-earth method I have to bring the 0V down from the reservoir caps again?
Q2: Each filer/buffer/gain stage has its own PCB trace connected to the pre-amp star ground. After terminating the new power supplies 0V's to each stage do I still keep those connections the the preamp 0V or they all need to be disconnected, please?
Thank you!
Best,
Ivo
Ivo, sorry about those pictures going missing (blame my ISP for that). I've tried to find them but no luck so far - and in this case they really would save 1000 words
Basically; The 'Holy Grail' of Naim preamp grounding can only be fully realised by building a power supply that is capable of fully isolating each stage at OV level. The 'Split Earth' and the 'Traco' mod's were a sort of halfway house to the fully isolated ideal arrangement, but (I think) gave a taster of the benefits of this approach. One way to achieve the fully isolated arrangement (as demonstrated in those missing photo's) is to have a fully isolated primary supply for each stage. That's is, starting with individual transformer/smoothing/regulation in an outboard supply for each stage. The 0V and 24V lines then routed directly to each stage, effectively eliminating power supply current from the preamp star 0V system. Naim used a symmetrical PS arrangement to achieve the same goal in their 552, by the way.
Unfortunately you cannot 'mix and match' with 0V systems as all you'll end up with are ground loops and poorer performance. Using a convention primary supply (with common 0V grounds) you need to keep the 0V arrangement fully star earthed in the preamp as well.
Hope that helps. I'll post those pic's if I can find them.
Mr Tibbs
Ivo, sorry about those pictures going missing (blame my ISP for that). I've tried to find them but no luck so far - and in this case they really would save 1000 words
Basically; The 'Holy Grail' of Naim preamp grounding can only be fully realised by building a power supply that is capable of fully isolating each stage at OV level. The 'Split Earth' and the 'Traco' mod's were a sort of halfway house to the fully isolated ideal arrangement, but (I think) gave a taster of the benefits of this approach. One way to achieve the fully isolated arrangement (as demonstrated in those missing photo's) is to have a fully isolated primary supply for each stage. That's is, starting with individual transformer/smoothing/regulation in an outboard supply for each stage. The 0V and 24V lines then routed directly to each stage, effectively eliminating power supply current from the preamp star 0V system. Naim used a symmetrical PS arrangement to achieve the same goal in their 552, by the way.
Unfortunately you cannot 'mix and match' with 0V systems as all you'll end up with are ground loops and poorer performance. Using a convention primary supply (with common 0V grounds) you need to keep the 0V arrangement fully star earthed in the preamp as well.
Hope that helps. I'll post those pic's if I can find them.
Mr Tibbs
Mr Tibbs, thank you for the reply!
I think that I got your basic idea but I am not very sure how to best implement it hence my two questions above.
As you said a picture saves a 1000 words so, I drew two schematics - please see the links bellow.
I suppose the first one is the one to go with but let me know if I am wrong, please.
Diagram 1 - the correct wiring?
https://goo.gl/photos/j5nmvNvpgj5TX5wz5
Diagram 2 - wrong wiring?
https://goo.gl/photos/81HdYEKkNBuKTway8
Thank you!
Ivo
mega lord
Centre tapped
I use the arrangement as drawn by Mr Tibbs in the diagram above.
My preamp has only 821A boards in at the moment but it really does work a treat. When i get the RSL phono boards purchased and installed i will be doing the same with their PSU too.
Will give it a go on my CD3.5 as well but that has a ground plane and so may not be effective. Dremel down the middle of the ground plane probably not a goer.
Stu
My preamp has only 821A boards in at the moment but it really does work a treat. When i get the RSL phono boards purchased and installed i will be doing the same with their PSU too.
Will give it a go on my CD3.5 as well but that has a ground plane and so may not be effective. Dremel down the middle of the ground plane probably not a goer.
Stu