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Topic: EAR834p how does RIAA feedback work?

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Posted by Romy the Cat on 11-13-2007

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

Posted by guy sergeant on 11-13-2007
The 'Death' phono stage.  I like it, it may have legs!

Posted by Romy the Cat on 11-13-2007
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

Posted by guy sergeant on 11-13-2007
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.

Posted by Romy the Cat on 11-13-2007
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

Posted by guy sergeant on 11-13-2007
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.

Posted by Romy the Cat on 11-25-2007
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

Posted by Paul S on 11-25-2007
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

Posted by Romy the Cat on 11-25-2007
 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?
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.

Posted by Romy the Cat on 05-24-2008

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.

EAR834PT.jpg

EAR834PT.jpg

EAR834PT.jpg

EAR834PT.jpg

The Cat

Posted by Paul S on 05-24-2008
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

Posted by Romy the Cat on 05-24-2008
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.

Posted by Romy the Cat on 05-24-2008

EAR834PT.jpg


Posted by Romy the Cat on 05-25-2008

The second stage switched to fixed bias

Posted by Romy the Cat on 05-26-2008
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.

EAR834PT.jpg

EAR834PT.jpg

EAR834PT.jpg


Posted by guy sergeant on 05-27-2008
 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.

Posted by Romy the Cat on 05-27-2008

 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.

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

Posted by guy sergeant on 05-27-2008
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 Smile

Posted by Romy the Cat on 05-27-2008


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

Posted by Romy the Cat on 05-27-2008
 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 Smile


... 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.

Posted by Romy the Cat on 05-29-2008

834PTF_and_PS.jpg

R22 is nor R but K


Posted by Romy the Cat on 05-29-2008

Here are some commentaries regarding my “End of Life" Phonostage.

The name of this phonostage derives from many factors. I am forty, winch it more or less a half live and in the first half I was playing a lot with different audio toys. The last 10 years I played more or less aggressively with phonostage as the RIAA stage were some kind of bottle neck of analog reproduction.  However, what I discovered that regardless what I did with RIAA filteres I always returned to a combination of Expressive Technology magnetic and EAR 834 phonostage. For whatever reason that sound to me is the most comforting of anything I heard or can imagine in LP sound. It has better sound then just good sound – it has some devilish musical magic that is so difficult to “get” in audio. So, from one side I had a very satisfying audio result. From another side I have a desire do not do anything with my references phonostages anymore (I have found a good “second rank phonostage” for my none-reference arms and will play with in later). From the third side I have a materialistic and rational presumption that it will no ever be any more interestingly sounding step-up transformers (available within my reach) then the Expressive Technology ET2 transformer… So, considering that I look forward to retire from my “reference” phonostage interests I decided to render a short “end of the RIAA desire” project…

Then, I got a phone call. It was a friend of mine, an audio guy, who was sick and who was kind of on his way out. Talking with him I got inflicted not by the sense of our own mortality but rather with a feeling of abnormal ratio that we practice on audio – the ratio between exercising of results and preparation of the results. We, at least some of us, spend a large amount to time and efforts to discover specific areas of sound understanding but the sad truth is that the time we invest in audio education of ourselves has a “price tag”. This tag is a removal ourselves from the experiences of actual consumption of musicality for the sake of learning about audio, or learning the rules of audio consumption via a playback.

So, I decided to end with it and I feel that I know in analog enough in order do not need to know or to care about anything else anymore. It is not that my analog setup is good or bad but rather it is about the fact that my results with analog sound are sufficient for me in order me do not invest more time or efforts in order have a desire to have better Sound. I recognize that the second part of my 40-years I have no interest to think that there is anything else out there in analog world that attracts my craving to try it. I understand that what I say is not the factual statement but it is rather my sentiment of self-delusion but I agree with myself in this delusion. Thinking about it all a few month back here is where the idea of “terminally beautiful phonostage” came to the existence. The dying friend proposed a good idea: his death will stop his peruse for his version of “better sound”, so I figure what why wouldn’t  I  declare the death of my analog desires right now, while  I still have 40 years ahead of me for actually practicing my analog expertise and practicing  my analog accumulations.

So, the “End of Life Phonostage” is my version of absolute RIAA references after which egos and sound have no needs anymore to be enlarged. I do not suggest that that the “End of Life Phonostage” performs better then other hypothetical phonostages I just state that I do not look forward anymore to answer this question to the rest of my audio life. So, I do not consider the “End of Life Phonostage” as a “Death phonostage” as it was proposed in the beginning of the thread but I rather feel that the “End of Life Phonostage” is a birth phonostage, the birth for a new level of audio practicing awareness.

Rgs, Romy the Cat

Posted by Paul S on 05-29-2008
Well, that sounds perfectly reasonable, and it also gives you an out in case you happen to hear something else that really turns your head.

Although 2007 did not make it appear so, I have had +/- the same thoughts about gear for some time, perhaps partly from the pressure/weight of 59 years, 45 of it spent effing around with hi-fi.  At this point I think I might be pretty close to "good enough", apart from the @#$%&* electricity.  Or, maybe I have to just let go and re-think things to allow for bad electricity.

Since the best sound I get is still from vinyl, the phono stage is critical for me.  But, by the same token, all sources have to be "aceptable".  I am beginning to think that "acceptable" means not so prone to screw things up as much as it means "revealing", or other hi-fi adjectives.

I still generally think I need +/- FR to really sink into a musical perfromance.  But, now that I am more familiar with my system it is quite clear that I will never get close in terms of absolute SPL/dynamics with my present set-up.

But since we are not, in fact, getting FR/natural dynamics anyway, then I suppose what I settle for at any point at least gets the musical message across, or at least it does this on a good [electricity] day.

Best regards,
Paul

Posted by Romy the Cat on 05-29-2008
The powers supplies are built and the corrector is fully operational. I will burn it in for a coupled days, then calibrate it and hope to listen it coming weekend.

EAR834PT.jpg

EAR834PT.jpg


Posted by Romy the Cat on 05-30-2008
 Paul S wrote:
I have had +/- the same thoughts about gear for some time....
Yes, many of us in one or another state of our audio progress come to the desire to retire from specific audio desires but in my desire to retire my references phonostage interest there is one more ingredients – I personally do thinks that ET2 and EAR-834PT is the very best thing that I ever heard or ever will come across. So, my abandoning of the the phonostage interest has also some very practical rational.

The that ET2+EAR-834PT combination (not in my current version – I do not know how it will sound but I presume that it will not lose it) handles sound in a very different manner than any other phonocorrector, so different that it eventually become too boring to ask the similar result from other phonocorrector. The ET2+EAR-834PT has amassing softness of the opening notes but at the same time it can accelerate within the note while it hits the pitch with  absolutely unmatched rate of dynamic change but at the same time it doe maintain the reference to the original softness and gentleness of presentation. That is so amusing characteristics and I got so addicted to it that if a phonocorrector does not do that ultra-dynamic softness then I have a definitive interest in tacky LP playing. To my knowledge not of the other tried by me correctors besides the ET2+EAR-834PT combination even try to do it. Partially the RLC phonocorrector have tendency to do something similar but the ET2+EAR-834PT combination sets juts a whole another demotion of the “ultra-dynamic softness”. This ET2+EAR-834PT’s intelligent softness is so ever-penetrating in whatever 834PT does that it become truely the only way of listening for me.

The Cat

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