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Pre-fix modding.

flashgo said:
You mean I need to build those Paradise boards that arrived a while back?
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This is interesting, as SQ's su Prefix and TPX are currently in my system and sounding absolutely awesome! Very 3D, fantastic PRaT, beautiful tone...all of it really.
 
Yeh, but you need to be up to date with the thread.

Match your input transistors as well as you can, don't bother with 10% try and get them to 1%. Same with the current mirrors, match them as well as possible. measure all your emitter resistor and match (yeh they are 0.1%). Stick to crappy electrolytics on the boards, low esr don't help. Fit the 470pf and 2n2 compensation caps to the shunt to stop it oscillating at HF, and you can replace the 10uf lytic with something with poor esr.

That seems to be the list of changes, best practice.

It is worthwhile, even if I had to go through 1300 transistors to get the matches I needed.
 
SQ, do you mean up to date with the Paradise thread? Sounds like I should stick with the Su-Prefix project for a bit and wait for more motivation before tackling the Paradise.

Dan, I had been planning to build STRs into the Su-Prefix, but separating the PSU will allow some experimenting. (I also have a TPX to build up.)
 
flashgo said:
SQ, do you mean up to date with the Paradise thread? Sounds like I should stick with the Su-Prefix project for a bit and wait for more motivation before tackling the Paradise.

Dan, I had been planning to build STRs into the Su-Prefix, but separating the PSU will allow some experimenting. (I also have a TPX to build up.)
Click to expand...

For my ears external TPX1 is better (Just a bit more kick/slam) than a Teddy. I don't know how much is gained by putting the regs in the same box as the Prefix - 'some say' nothing at all
 
I think SQ also observed that splitting the rails on the phono circuits produced no benefit, so the case for an external PSU is very strong.
 
Well, I followed Si's build, but knowing that an external PSU was sufficient allowed me to go with a much smaller (1U) box:



It's not all visible because there's a lot under the board, but I upgraded to teflon caps wherever possible. The purple shrink-wrapped jobbies are actually Soviet polystyrene. The input and output tants are bypassed with 22nF teflons. Other goodies are MKP4s on the rails, AVX FFB for FB, and Texas components nude resistors + teflon caps for loading. It's currently powered by 2 rails out of a converted 52PS.

It really sounds amazing and blows away anything I've had in my system before. My son, who has never before commented on the SQ of the system, said "You know that little black box you just made? It really sounds good."

The su-Prefix sets a very high bar for the Paradise project under way.
 
The thing is, the paradise is just so much better in every way it's not even funny. The top to bottom coherence and the way it just never looses track of the music no matter how complicated it gets will blow you away. Match the input stage to better than .1% and ensure the riaa is similarly matched and it will reward you with the most precise soundstage and stereo focus you've ever heard.

It would be interesting to see how a Su-Prefix sounded if similarly matched.
 
Yep, as sq says, good as the modified Prefix is the Paradise is genuinely in a different league (difficult to believe, but it's true).
 
We'll, the su-prefix may end up being a spare, but it's quite a competent one. One thing that's surprised me is how long it's taken to bed in - 3 months now and still offering up surprises. For a while now, it has blown away anything I've ever heard in the digital realm. My su also has the advantage of being small.

As always with this journey, each step allows me to see further, so I have some inklings of expectations for the Paradise. In particular, I'm looking for another improvement in distortion and better definition of spatial boundaries.
 
Flash, I think the long bed in period is due to those Russian caps. They took forever (3 to 4 months) to settle down in my ARC LS7 pre. My su-prefix is running off a TPX2 and sounds so 3D, and the music has so much air and fluidity that I really can't comprehend how the Paradise could be any better. If I were to build a paradise then I would have to sell the Prefix on.
 
Hi Dan, I suspect the soviet caps as well, although the Mkp4s can take a while too. I experienced a small upgrade going from a souped up SNAPS to the 52PS, and I've got a TPX build waiting to try out. However, I'm only expecting incremental improvements, while it sounds like the Paradise will be a leap. These projects plod along slowly, so I'm enjoying the Su-Prefix for now.

What are you using for coupling caps?
 
Particularly where you are using them at a fraction of their working voltage.
Best to try and reform them at near there max voltage in a test rig before soldering them into just signal path use

Alan
 
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