Allo gents,
not sure if you've seen this:
http://www.pmillett.com/etf_sod.htm
http://www.pmillett.com/file_downloads/ThesoundofDistortion.pdf

Pete devised a circuit whose distortion order and level could be controlled. It was for educational purposes but might find application in - to quote JC Morrison - a hedonistic preamp.
cheers
cv

Last night electricity was surprisingly OK, despite of the current heat wave and that everyone runs air-conditioning and I found myself listing deep into high. It was mostly LP and I came to a few interesting observations regarding the sound of my air-cap armed phonocorrector. The corrector has now it’s good tubes, closed up and as now it is in the state how it will be permanently.

I looks to me that corrector has own signature but not the signature that simile to any other correctors I have heard. The uniqueness that I would like to comment on this corrector is its ability go up in dynamic range of high frequency without introduction of… anything beside just a higher dynamic range of high frequency. The corrector gains volume in upper mid range with stunning cleanness. In my view it is unknown and not anticipated in audio as rise of HF volume is always associated with rise of some artifacts. The air-cap armed corrector does not do it, does not do it at all. While the air-cap filter has orders of magnitude more sophisticated and unsoiled ability to run across HF ranges it also open up unheard ability for discrimination of upper MF and HF differences. The idiosyncrasies of the “string bite” in each section, each orchestra, each style of playing manner and…. each pressing or each stamp batch became more highlighted, more insistently distincting one from other. Still, it is doe not by differentiating the artifacts patterns and most of audio does but somehow different, I do not know how to describe it at this point  – it shell be heard. You see, the air-cap has no “resolution”. It delivers very distinctive HF but no “resolution”. I always told that “resolution” was invented by Morons who would like to catalog the playback artifacts – the air-cap filter can afford to do “no resolution” type of sound.

Still, I feel that air-cap has own coloration. This “no resolution”, vacuum-clean HF dynamic is coloration itself as I do recognize this characteristic across all music that the corrector plays. The sound of the air-corrector has own signature- the “signature of tempted virtue” – this behavior does not exist during my experience of live musical events. I think I need some time to reflect and to think about what I hear from this corrector.

I do not particularly like Asian women. A few of them that I dated annoyed me tremendously with their overly zealous desire to compliment and please me. I am, as any other person, do not mind to be praised but I would like to get as a reimbursement for some kind accomplishes of mine that I personally values. To be admired by those Asian girls just because I was a current man in their live made me very fell boring and I always voluntary escape from the glorifications of the Asian women right into the hands of our Western bitching and demanding females. So far the air-cap filter in my phonocorrector acts in the way like an Asian woman those overly enthusiastic do essentially very positive things. Perhaps I ask too much or perhaps this effect will moderate itself with time but so far it is what it is.

Romy the Cat wrote:

Still, I feel that air-cap has own coloration. This “no resolution”, vacuum-clean HF dynamic is coloration itself as I do recognize this characteristic across all music that the corrector plays. The sound of the air-corrector has own signature- the “signature of tempted venture” – this behavior does not exist during my experience of live musical events. I think I need some time to reflect and to think about what I hear from this corrector.

Usually any piece of audio with which I dealt had own sonic set signatures. It is not necessarily bad thing. It like an accents in language – in many instances accents modify the meaning of said, however if the subject exposed at crucial level of depth then the presence and the value of accents become irrelevant. The same is with the sonic signatures of audio elements – the all screw up the sounds but if they hold the basic integrity of Sound then those signatures are out of attention. As I said the “End of Life Phonocorrector” has own signatures at “the sounds” level and I might not even convinced that they are so transparent from a perspective of Sound. However here is exceptionally interesting thing - the signatures are not static as in any other audio element I head but they shift from record to record.

Playing some records that I know very well for years and that I played in different settings I might identify the very fine specifics that I feel are not the part of this specific recording/pressing but rather a sonic contribution of my playback, a phonocorrector in given case. However, with another record the characteristic sonic injection from this phonocorrector changes. The phonocorrector truly prostitute itself, subduing own integrity and somehow reacting to the demands of the requestor. It is VERY interesting and in much unexpected behavior. I truly cannot get grip for it as now and I need to think about it more…

No, VTA is not in and of itself a characteristic of Sound; but in my own system the stylus' vertical tracking/rake angle is not something that results inthe same sound no matter where I put it.  In fact, even small changes profoundly affect the character of the sound that the phonostage is expected to "make the most of".  And in my system, record thickness and original cutting angle are both - apparently - factors to be reckoned with in terms of setting VTA, which, in turn, audibly affects the character of the sound, in a "pattern" similar to what you have described earlier.

Sure, it's a nuisance; but this does not make it go away.  And at the same time it is something I am able to dial to very beneficial effect.

Best regards,
Paul S

Romy the Cat wrote:

OK, here are some follow up thoughts after the completion of the project. I am sure I will burn it for a month or so. I think everything will be fine, I do not expect any issuers technical or sonic. The way how the entrance to the corrector done it is very easy to replace the 4 cable from 4 arms without replacing the cables. As I told I did found a very interesting “second phonostage” (very convent one) that I was planning to use with my other arms but if it is so convent to flip the cable I wonder if I go for the second phonostage. I still have my former 834PT and the 7788-7721 phonostage available, all performing perfectly fine … later on I will decide if I willing to use them. There is one area that I would like to explore with my “End of Life" Phonostage after it will settle down. The very smart fist stage in there will be stay as is, also I have no interest to experiment with second stage. The last stage is just a cathode follower. In my ultimate buffer experiment I never was able to get a good transparency from tube buffers, so I am intending to put there (as an experiment) a transistor instead the last 12AX7. I am not planning to change anything but juts to take a male 9-pin tube socket, solder in there a transistor that is able to care 300V and juts plug it and play. It is possible that with SS output buffer I might get different result. What kind result I would like to get? Sonically I can’t at this point to identify what I would like to get but measurements –wise I would like to drive the low range to sub 8Hz at 0dB. It is not that my hands are itching but I feel that at line level SS buffer shell do better than a tube…. If someone know any good sounding low power (5-15mA) transistor at 300V-350V then please let me know. So far I was proposed MPSA42, ZTX458 and suitable but too powerful MJE340. As a reader of my site suggested: “The NPN will reduce the output impedance => will affect the Riaa feedback increasing the gain by ~1db@20Hz and ~0.5db@50Hz(in your setup will be quite noticeable). A quick and dirty remedy is to add a resistor (1k5-1k8) in series with the emitter of the NPN. Although this could be useful to reveal the sonic properties of the NPN it may also defeat the trouble” I still consider the options how to make the experiment with buffers substation clean and methodologically kosher. Sine I have absolutely no knowledge at SS any recommendation are welcome via the site or direct emails.

The guys who red my site advised me in selection of a SS devise that would do no changes to sircut of any kind and would be just drop-in replacement. I bought MPSA42:

http://www.goodsoundclub.com/PDF/MPSA42.pdf

 and plugged them in. The result was surprising to me.

I lost all bass, the bass in amplitude (a lot) and in quality - the bass become very shallow and unpleasantly fast.  Also, in a very minor degree the very HF become too… SS-like. Surprise? Anyoe I hate the result and I put the tube back, I will not try it on my “End of Life" Phonostage

With my resent battle with Shelter and the off the FM session analog renaissance I am playing a lot of records and there is one observation I would like to make. I feed all my 3 “better” tonearms into the “End of Life" Phonostage and I can’t not to mention how beautifully the Phonostage behave and sounds, in fact it is beyond beautiful, it is truly extraordinary.

I usually is very bitchy about the performance of audio elements, would it mine or others. I know well where my own audio element slips. However, with the “End of Life" Phonostage I have literally no single point where I would have an issues. It just does phenomenal Sound and it turned out to be phenomenally friendly and accommodating in my setup. As far as I concern the “End of Life" Phonostage is truly deserves it’s name…

drdna wrote:

What specific objectives did the air caps address in the circuit? You refer to the tempted virtue sound but I am unsure as to the goals that you were trying to achieve with this circuit alteration?

 I what wrote about the air caps in the thread: “Where are our good phonostages?”

The genuineness of this Paravicini circuit is that he use feedback to plate – or to vey high impedance – and in this situation it revilers very small values of capacitance to write the necessary RIAA curve. In fact the curve is written not by the feedback but by the Miller capacitance of the tube. The 12AX7 was designer as audio tube, it is a radio-frequency rube  and therefore is has very high Miller capacitance, the capacitance the otherwise conceded as parasitic but the smart Paravicini put it actually in the beneficial use. So we have a circuit with “hidden RIAA”.

Now Paravicini adds the very light touch of capacitance into feedback to make the Miller capacitance to work what it shell work. The values are very small s the capacitance in feedback sort of multiply the tube’s own Miller capacitance. The series capacitors in feedback, regardless of value and types are very bad. In fact a feedback cap is the more auditable them loading, coupling, cathode or any other cap. The coupling cap for instance is charged with DC on both sides and the AC. What cap is? It is the sequence of conductive and non- conductive surfaces where non- conductive dielectric acts as an abrupt termination of AC flow. However, the dielectric is not a perfect dielectric and has some free electrons in itself that can care the signal.  This abrupt termination induces a microscopic force in the dielectric that make the dielectric to move, and by virtue of it creating variable reflections of transmission termination. So, that coupling cap has already charged or pollarded with DC on both sides and the cap’s conductors have already biased or physically oppressed the cap’s dielectrics. In case of cap sitting in feedback there is no DC (in second cap) and the dielectrics are not damped. Furthermore the re-polarization of dielectrics does not happen at non-auditable frequency but at very much auditable frequency – the frequency of the correction. I do not even mention that dielectrics experience different behavior of  electro- mechanic induction at different frequencies…

 So, how to create a better condition on this situation? The concussion is to get rid of dielectric all together. The non-dielectric caps: air or vacuum are very large for a given value but in this Paravicini case the values of the caps are so small (100pf and 300pf) that the air caps could be called for the duty.

I do not say the in the “End of Life Phonostage” the air caps is something that made all sound. The ET SU-2 transformer I think is the very heart of this Phonostage and 80% response for the corrector’s sound. Still, I think the air caps were very contributive as well. I did not listen the “End of Life Phonostage” with mica caps but I did listen and did “evaluate” the vintage mica, the polystyrene and air caps in context of my 7788-7721 phonostage.  (It uses the absolutely the same Paravicini’s ides of feedback only uses7788 pentode in input and has just two stages). The result was very superbly convincing and perfectly proved the theory about the fundamental advantages of air caps.

Paul S wrote:

Romy, doesn't Tim de P also use this cool Miller capacitance idea in his never-mentioned "high end" tubed corrector?  Also,  do I remember reading that he runs both channels through the two halves of the same twin-triode 9-pin tube?  Is this something you changed when adapting two units for stereo?  BTW, I have never heard the P88, or whatever he calls it.

Well, it was a long debate in the past if to keep my “End of Life Phonostage” as it use to be: six tubes, having 3 halves running right and left channels and keeping other halves half “cold”. I eventually decided to go for just 3 tubes running right and left on the opposite halves of the same twin-triode. I very careful considered the cons and pros and consulted with many people. I still do not know if my decision was “correct” but below is my rational. Subjectively I think that I did detect some very negligibly minor advantage of six tubes version but it was so none-conclusive and so non indicative that I discarded it as a margin of the experiment.

For using halves of the same twin-triode:

·  Less costly tubes.
·  Less inner chassis hit.
·  Less filament AC inside the phonostage chassis
·  More compact and elegant layout
·  Inability to reuse the tubes buy flipping them to another side when the current cathode is gone
·  The tubes of the right and left channels come from the “same barrel” (gas contamination, cathode poisoning etc)

Against using halves of the same twin-triode:

·   Alleged crosstalk

I truly do not know any other considerations then crosstalk and here how I thought:

According to the papers the crosstalk in the twin-triode is around 90dB-100dB. It is VERY high number; do not forget that cartridges have 20dB-30dB. The numbers of crosstalk are mystery for me and I was not able to see how extra 10-20dB of improved crosstalk do better for imaging subjectively. I figured that 90dB-100dB if electrical separation in twin-triode is too high do not worry about it. The 100dB of separation even my Macondo can’t handle as my horn pick the pressure from room and have their diaphragms to act as microphones. I have my amps off and might talk at my room in normal voice, having the channel loudness-to-pick- modulation meters on Macondo running a full scale…

So, I think and feel  that in practical application the theoretical crosstalk in twin-triode is way offset by the advantage I enumerated above.

To close the book on the correctors subject I put some comments in a dedicated page in “My playback” section.

http://www.goodsoundclub.com/EndOfLifePhonostage.aspx

Here is a Thai guy looks like built my “End of Life Phonostage”

http://www.kaponk.com/node/715

I do not see nether input choke or air capacitors in correction chain. The most important I have no idea what step-up transformer he used and what kind sound he is after. I am sure he can read schematic and to solder but it not so important skills. I do not read Thai but from I understood he did not talk about sound of this thing in his article.

It is always there is something that poisons everything. It is last night in my Boston apartment, a night before the final big move and I was in the middle if heavy packing. Suddenly as lighting stroke me: I was moving my moved audio equipment from one bedroom to another bedroom, letting the carper guy to do his job, as suddenly I realized that I did not move my End of Life Phonostage. All my equipment was sitting in one bedroom and all of it has one way or another some kind of handles. The End of Life Phonostage has no handles of any kind and I do remember that whatever I moved I used handles. I dropped everything and rushed to my new place and for sure I did not see my phonostage.  I do distinctly remember that I move it, right on the seat of my car, driving very gently in order do not fuck up the air capacitors, and now it look like it gone. If it so then it is VERY sad!!!

I heard that during the move the things walk. Over the last 2 week I have contractors working in my new place. I do feel very confident and comfortable about them, still where the hell my phonostage? I am sure no one need it beside me, particularly without power supply, still the bedroom is the only room where all equipment sits and the phonostage is not there.  If it were lost then phonostage itself is not a big deal but it had the Expressive Technologies SU2 transformer in it and this is non-replaceable. This feeling of lost phonostage really poisons my entire getting new house ceremony and I am very upset…

Is it God punished me for the overly ambitions name of the phonostage – “The End of Life Phonostage” or is it some kind of sarcastic message of him for my arrogant treatment of the phonostage as the last statement of pnonocorrector?  I do not know.  I was driving back to Boston to continue packing and was thinking that I would need a new phonostage – I so do not want to deal with phonostages anymore…

Anyhow, I got home and I am not in the mood the pack. A few thousands LPs left to be packed but I have no feel to touch the vinyl.  Fuck it, I will ask the movers to pack it tomorrow, I am in the moaning for my “The End of Life Phonostage”…

Romy the Cat wrote:

...This feeling of lost phonostage really poisons my entire getting new house ceremony and I am very upset… Is it God punished me for the overly ambitions name of the phonostage – “The End of Life Phonostage” or is it some kind of sarcastic message of him for my arrogant treatment of the phonostage as the last statement of pnonocorrector?  The Cat

Dear Romy,

I truly am sorry to hear about your loss. You certainly do not deserve this. If it is any consolation you might like to check out

the following website for an insight into the Bent transformers in relation to Expressive. Not sure how much credence you give to the 

info but you have  to start somewhere.

http://www.high-endaudio.com/RC-Step-ups.html

regards,

Gordon 

Reggie wrote:

Hi, Reggie here. Sorry Rakesh, but I have to say; what a smug tosser's answer. What the heck does God and Starving children have to do with his phonostage? Is he supposed to feel guilty for being upset about it being gone and why would you laugh about it?? Really Sorry Romy.. Hope you find it. Really I do...