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Posted by Romy the Cat on
11-13-2007
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Recently, I made a movement toward to a project that I have been contemplating for 5 years – I would like convert my Expressive Technologys SU2 and 2x834PT tandem into a final packaging solution.
For the last 5 years I have learned following:
1) 2 heavy phonostage boxes do not do well mechanically coupling via RCA jacks with heavy Expressive Technology transformer. They do well if they are not touched but if then moved frequently then the RCAs have tendency to lose ground and pick up some consequential noise.
2) If I direct coupled the Expressive transformer with the 2x834PT’s input grid then I will lose the unnecessary RCA male-female and ~ 3 inch of wire. There is nothing that will make me more happy in analog then loosing unnecessary cable and unnecessary connectors in the secondly of 28dB gain transformer.
3) I can make the entire new phonocorrector 2 times smaller – a good help for my always-challenged to of the rack’s real-estate.
4) Since I do not have a good sounding solution for switching the .2mV signals of MC cartridges and all my attempts to do it had failed. Also, since I can’t imagine better performing phonostage I would like in a new phonocorrector to have a provision to switch the cables from my different tonearms. Currently I have difficulties to do.
5) I would like to change the type of air capacitors that I use in the corrector 2x834PT, using larger caps.
6) I would like to change the diodes in the PS to new Silicon Carbide Schottkys.
So, the idea to take my existing two 834PT boxes, my separate 834PT power supply and my ET-2 transformer and arrange them in a separate accurate box with easy access to the RCA input s does look like very a reasonable project. It will not take a lot of efforts – a few hours no more.
I was thinking about the naming of my “new” phonostage. Considering the truly unparallel performance this corrector is capable and considering the fact that I know that I won’t be looking/thinking about another “reference” phonostages ever again I decided to name my new Expressive Technology SU2 + 2x834PT assembly as “End of Life Phonostage” . There is another dimension of Truth that is opens up to the people when they face the ends of their lifes. The “End of Life Phonostage” operates at the very same “other dimension” of listening awareness, presenting results form a perspective of completely different abstraction. You as a listener just need to be “ready” to understand it… Rgs, Romy the Cat
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Posted by guy sergeant on
11-13-2007
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The 'Death' phono stage. I like it, it may have legs!
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Posted by Romy the Cat on
11-13-2007
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Yes, I like it too. It is in a way symbolizes a termination of any superficial ambitions… the shallow ambitions that we have so many in our anxiety with RIAA correctors. I assure you that if you heard the “End of Life” then you might understand where I was coming from.
The caT
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Posted by guy sergeant on
11-13-2007
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Maybe, maybe not although I'd expect it to be unlikely with a Koetsu, Shelter 901 or an SPU at the front! Not unless they are very different cartridges to the samples I've listened to.
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Posted by Romy the Cat on
11-13-2007
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It is exactly what the “End of Life” means – you know all necessary answers and have no needs to prove anything to anyone. I heard from you before that you do not like 834PT’s sound, I presume that it was ether bad 834PT, or extraordinary-horrible step up transformer or some very inadequate listening expectations – perhaps all of factors combined. Still, I do not advocate you or anybody else to revise your opinion about 834PT, not to mention that you do not use ET magnetics. All that I did was a declaration that I am abandoning my interest in any other RIAA preamp besides my “End of Life” phonostages. I still keep my 7788-7721 with my mono tonearms and I will be interested in Lamm L3 full-function preamp, if Lamm will not retire before he does it. Still Lamm will be “competing” with the stunning TTH’s intelligence of my “End of Life Phonostage” and after the LP2 I have a LOT of suspicions that Lamm has no own realization how serious a phonostage might sound. Frankly speaking my interest in L3 will be not because it’s phonostage but rather it’s line stage… I think it will be the last “others” phonocorrectors that I will; unwillingly bring to my home…
THe Cat
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Posted by guy sergeant on
11-13-2007
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TTH's ?
By the way I've heard several 834's not just one. You are right though, I don't particularly care for what I feel is its rather obvious character.
No ET magnetics either, hard to find/hear over here. I think a just handful were sold in the UK. A friend had an ET1 but acquired an AudioNote ANS-7 instead. I don't know of anyone else who has the ET2 though so perhaps that is markedly better. Only you'll know the answer to that. As there aren't any more of them its somewhat irrelevant to the rest of us.
I'm all for the idea of something being the last or the end of the line particularly with regard to phono stages.
I hope to get somewhere closer to that happy state with my next (LCR based) effort.
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Posted by Romy the Cat on
11-25-2007
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Yesterday my machinist informed me that the End of Life Phonostage’s chassis will be reedy next week. So, I desisted update the power supplies of the thing replacing the FRED diodes with those no reverse/forward recovery Silicon Carbide Schottky diodes. It was kind of fun as I was not in that power supply for 7 years and it had spider net all over it and a few dinosaurs’ eggs…
There is nothing really special in that PS. Each channel has own separated transformers, separated rectivication and separated filters for plates and filaments. The filaments have input choke filters. The plates have practically default 843P PS circuit, with voltage bubblier) – in my past I was not able to get better sound for this phonocorrector from better and more sophisticated power supplies. So, I put the 600V Schottky in and closed it up. Well, considering the name and objective of this phonostage it should be the last time I ever opened this supply…
The caT
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Posted by Paul S on
11-25-2007
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Romy, I have noticed the same thing with the phono stage power supplies, that the big multi-chassis units with dual 100 lb. PS get no overall sonic advantage, all said and done. So how do we deal with the stupid, lousy AC that is too often present? I am happy with the good-AC sound from my modded K&K, but I do wish I could get its best more often.
Have you managed to get your phono stage clear of bad AC, and if so, how?
Best regards,
Paul S
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Posted by Romy the Cat on
11-25-2007
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 Paul S wrote: | | Romy, I have noticed the same thing with the phono stage power supplies, that the big multi-chassis units with dual 100 lb. PS get no overall sonic advantage, all said and done. So how do we deal with the stupid, lousy AC that is too often present? I am happy with the good-AC sound from my modded K&K, but I do wish I could get its best more often. Have you managed to get your phono stage clear of bad AC, and if so, how? |
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It is all depends of a specific circuit I guess, the 834P eats no current. I tried in past regulation and bleeded input chokes but 834P did not like it and felt good only with what it had. The AC factor? This is more complex. My last APS PurePower reregenerator (the fifth unit!!!) does quite amassing things but the reregenerator’s use is not as a straight forward as it might be expected. The PurePower is VERY idiosyncratic but if to treat it “properly” then it can do VERY interesting things. When I have time I will post my comments about the use of the APS unit in the appropriate thread.
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Posted by Romy the Cat on
05-24-2008
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Looking at my current 834PT phonocorrector I decide do not convert it into the “End of Life" Phonostage as it is good as it and I would like do not ruin it – I will always take advantages of a good MM phonostage. I took the Expressive Technologies ET-2 transformer and build another small board with 834PT RAAI correction circuitry. It took 4 hours and I love how I mange to layout everything. It will be incredibly small and it looks that in my new enclosure I will have some extra space.
Now I am thinking about the PS. The old PS I would like to keep with old 2x834PT. This corrector will be not dual mono and I will be using both halfs of the 12AX7. With the incredibly low current that this corrector sucks I think I will not go for dual mono PS . The leading idea not is the following: the filaments LCRCRC supply and the anode is LCRC +GGRC. The GGRC is a pair of my gas regulating tubes (0A2) that give exactly 300V that the corrector needs.
The Cat
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Posted by Paul S on
05-24-2008
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Nice minimal construction, Romy.
How do you keep the pots from drifting?
Have you thought of using small batteries for the filaments? I have not tried it yet myself, but it is the next thing on my list; dead simple and dead quiet, if you can put aside your anti-battery prejudice.
Gary Pimm over at Nutshell has a couple of ideas that look interesting, and you probably already know about Steve Bench's quiet, 2-channel PS (it is SS, however no reason you could not use tube diodes, if you must).
Did you split the correction over the 2 gain halves or use 1/2 as a cathode follower, or?
Best regards,
Paul S
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Posted by Romy the Cat on
05-24-2008
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There is no need to invent anything in the 834PT – it is good as is. The only think that I “might” do it conversion of the second stage to fixed bias and drive R18 resistor from 1.5V battery. Everything else is perfect in this corrector.
The Cat
Correction: There are mistakes on the circuit. The R3 and R4 are 330K not 330R. R11 is not 750R but 750K. Look below.
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Posted by Romy the Cat on
05-24-2008
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Posted by Romy the Cat on
05-25-2008
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The second stage switched to fixed bias
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Posted by Romy the Cat on
05-26-2008
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It is already converted to the fixed bias on the second stage with 47K and 10 voltage divider from negative filament (positive filament is in ground) and I have the perfect 150V on the second plate. It is already fully operational with 8mV noise not even shielded. I just love how it turned out to be as it has the exact layout as I want and it fits in the chassis-box perfectly. I might try a few parts (Multucap coupling cap as I had in my older version) and it will be it.
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Posted by guy sergeant on
05-27-2008
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| Romy the Cat wrote: | |
I hope no one tries to build this based on the diagram above. They won't get much output from it! If you can't see what I suspect are deliberate mistakes, you definitely shouldn't be trying to build one.
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Posted by Romy the Cat on
05-27-2008
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| guy sergeant wrote: |
I hope no one tries to build this based on the diagram above. They won't get much output from it! If you can't see what I suspect are deliberate mistakes, you definitely shouldn't be trying to build one.
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Guy, I think you have overwhelmed yourself with conspiracy theory. My attitude towards to all those projects of my is not the one that would make me to expose public to deliberate mistakes. I can make ignorant bloopers or demonstrate juts plane engendering stupidity (I did both in past) but the publishing deliberate mistakes it is not would I would do.
I did not use the schematic above to build the corrector – I built it from my head as the circuit painlessly simple but looking on what I draw I do not see that anything different then what I have currently assembled. I did not measured the corrector gain yet but preliminary I feel as it should be - I see no reason why the output shell drop after I went for fixed bias. Also, the corrector does a few mV ideal and when I touch inputs of makes under7VAC at output – the habitual voltage that I expected….
I will certainly measure and calibrate everything before I consider it doe but if you feel that there are any mistakes in there then please point them out. To me everything looks right so far.
Rgs, Romy
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Posted by guy sergeant on
05-27-2008
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Isn't 330 ohms a little low as a plate load for an ECC83/12AX7 to be running into? 330K ohms perhaps?
You often ask what is wrong with a given speaker installation, I thought you might be doing the same here.
Keeping us on our toes 
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Posted by Romy the Cat on
05-27-2008
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Referring to the threads a few month back:
http://www.romythecat.com/Forums/ShowPost.aspx?PostID=4937
I wonder if I need to play with the coupling cap between the first and second stage. Now I have my beloved ElectrocuCube 950. In my former version I had the Multucap RTX, that I also found extremely good. The RTX are slightly more rough, positively-rough vs. Cube 950 have positively-slower upper bass. I can live with ether cap with no problem. Still, I wonder if I shell try those new caps. For $90 each I can get the V-Cap Teflon Film & Tin Foil or for double of it I might try Duelund caps. I have no experience with ether of them but I have $200 for check my gullibility… did anyone used the V-Cap. Do not say yes and I will be holding you responsible for me burning another $200… well, I probably shell try it….
The Cat
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Posted by Romy the Cat on
05-27-2008
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| guy sergeant wrote: | Isn't 330 ohms a little low as a plate load for an ECC83/12AX7 to be running into? 330K ohms perhaps?
You often ask what is wrong with a given speaker installation, I thought you might be doing the same here.
Keeping us on our toes
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... but just a mistake of copy and paste labels in Visio. You are correct, it was of cause 330K – very much how it was on original EAR circuit. Thanks for pointing it out – I will correct it on the drawing when I get home.
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