The Dynaco's are originals that had some upgrades when I get them. I put in a Welborne cap board. Eventually I bought glass epoxy driver boards and used all high quality matched parts with Jensen Al PIO bybass caps. This made a big improvement. In the last few months I bought my first VTA product: the MK3 driver boards with 6SN7s. That has been a major jump in clarity and depth over the stock design.
Onto the phono stage: at the time I got the parasound I didn't want to jump into anything too expensive; and it seemed like you could push $10k with a phono stage. over the years I have learned (for myself) that there is a lot of hokus pokus in high end audio. I subscribe to the "anything better than 18 awg lamp cord is a waste" as quoted by Stanley Lipschitz and John Vanderkooy, members of the AES and the profs that run the Audio Lab at the University of Waterloo, where I went. I spoke with them at length over the years and they shared their research into the "sound of cable" which concluded that beyond good quality copper and well shielded interconnects, and 18 awg hardware store lamp cord speaker wire, anything else was simply a waste - there was no recorded difference when measured in their labs, nor was there any statistical relevance when testing with a wide range of listeners in a true lab quality A/B/X test scenario.
On the other hand, I do believe that capacitors make a sonic difference. I know, like me with cabling, there are people that feel caps don't make much a difference past a certain inexpensive threshold. In my own testing (not scientific) I have heard large differences between audio cap types and so this is going to be a big part of my PH15 build.
So back to my phono stage. I didn't want to make a big commitment with this and its basically the weak link in my system. I did however upgrade the parasound as best i could: upgraded all the components to higher quality and closely matched, replaced the opamps with ultra low noise ones ($30 each), beefed up the power supply and filtering, other things. here was the page I made covering all the mods: http://www.theplexus.com/pph100/.
After trying the VTA octal MK3 drivers I was confident in the VTA kit sound quality and decided to order a PH15 kit. I am going to build the PH15 with the highest quality parts I can afford. The topology uses 4 gain stages, the first which is a JFET. From what I can tell VTA bases their designs on Audio Research and the AR PH5/6 also use a JFET "front end". I'm not afraid of semi-conductors and I think in the case of the first gain stage of a phono stage, a JFET is a good choice. when you spread the gain over 4 stages, there is a strong benefit to using a JFET like that. although it makes the pre a hybrid and not a pure tube design. however I think, from the design, that the JFET "compromise" is only that in the sense of making the pre a hybrid - the sound quality should be better than a "pure" tube design (use google to search and you will see the reasons why).
Although the kit is only $200, I project the final cost of my PH15 to be around $1200. most of the additional cost is going to go into the component choice I made: Caddock MK132 resistors in all the critical places, V-cap cuTF bypass caps between stages, Jensen CuPIO on the output and Multicaps for all other RIAA points. All caps and resistors matched in pairs. I am also going to build in a pair of Jensen 34K step-up transformers because I need the gain for the Ruby 2. I current am running the Jensen step-ups with the Parasound set to the same gain at the PH15 (55dB) and it working out great in terms of final output level.
This is going to add an additional $550 for the caps, $125 for the resistors. I got a good deal on the Jensens which was $140 for the pair.
I am taking an (expensive) stab at the V-caps. I do like the Jensens Al PIO's and I did listening between those and Multi-caps, in the MK3 and in a 1 stage 12AU7 preamp I have. The Jensens had a wider, warmer, deeper sound to them. Larger sound stage. And now when I researched for cap choices for the PH15 I see that people do not like the Jensen Al caps very much, but the Cu caps are considered "good". the V-caps appear to get across the board top grades for sonic quality. they are expensive but they are not the most expensive caps. those, in listening tests, didn't do as well as the V-caps. so this is part of what fed my decision to go with V-caps. It's a risk however because I haven't personally heard them.
I decided to put V-caps in the 0.22uF bypass positions to, based on-spec, retain the sonic quality through the first 3 gain stages. I do know that the Jensen PIO caps have a different kind of colouration, more to a warmer fuller sound, from first hand experience. that and price drove the decision to go with Jensen Cu PIO on the final output, a 1.5uF cap. these are very expensive and the 2 Jensens will cost me $150 vs V-caps which would be $430. It's already a crazy amount to spend on 4 bypass caps, $400!
The Audio Research PH5/6 use Rel-cap PPMF's which ended up in Tier F "Best to Avoid" in one comprehensive cap testing effort (http://www.laventure.net/tourist/caps.htm). So if these caps can justify a $3500 phono stage which i have a feeling is very close in design as the VTA PH14/PH15 then perhaps my cap and resistors selection will raise it to a higher level of sonic quality? The Audio Research PH7/PH8 appears to use proprietary caps (http://www.drhifi.net.au/Reviews/ARC%20PH7%20Review/1.htm). The PH8 is $7000 so who knows, with my component choices will we be able to approach a $7000 phono stage with a kit cost of $1200?
I am thinking I will build the PSU in a separate case. I know I ordered the PH15 which has the PSU on the same board but it looks like I can slice the board in 1/2 because the PSU appears to be trace-discrete from the rest of it.
Speaking on which, any body know of a place I can get custom project cases made with proper punch outs? I found one place online and its $300 for each case! I could use hammond cases too but they don't appear to have cooling vents. I'd like cases with wood sides and ideally stainless steel.
PS. I also got a quad of V-Cap CuTF 0.22uF and a quad of Jensen CuPIO to try in my MK3's, replacing the Jensen AlPIO that are in there now. I want to "get to the bottom" of this capacitor issue (does it matter) and the best way is going to be listening to them myself. I'll pick out what I like and sell the rest. I don't go in with any preconceptions other than the AlPIO I have now sound pretty good and better than the Multicaps I was using.