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05-29-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 21
Post ID: 7473
Reply to: 7461
The latest version of the corrector – not heard it yet. (corrected)

834PTF_and_PS.jpg

R22 is nor R but K


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-29-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 22
Post ID: 7478
Reply to: 5856
The sentiments behind “End of Life" Phonostage

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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-29-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 23
Post ID: 7479
Reply to: 7478
Going on from "There"
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
05-29-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 24
Post ID: 7480
Reply to: 7473
Ok, it is already almost there.
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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-30-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 25
Post ID: 7490
Reply to: 7479
The ET2+EAR-834PT and the ultra-dynamic softness.
 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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-31-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 26
Post ID: 7492
Reply to: 7480
I am semi-ecstatic; my vinyl will be back soon…
and I hope it will be up to the level … of FM in term of enjoyments. Anyhow, the phonostage is the already pack up in the chassis and running. I dropped the B+ supply to 270V and the R1 restore to 120K, keeping the 100V on the first plate. I can’t wait to listen this thing tomorrow, it shell be very-very interesting and long-expected.

EAR834PT.jpg


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-31-2008 Post does not mapped to Knowledge Tree
Reggie
Posts 13
Joined on 05-08-2008

Post #: 27
Post ID: 7500
Reply to: 7492
MFA Systems Phonostage

Hello Romy

This is my first post.

Did you take courses in electronics and mechanical engineering or have you learned yourself outside of a structured environment? I am very interested to become proficient in working on/modifying my own electronics. I would enjoy spending time at the workbench such as the one pictured above.  

Reading many posts on your site has caused me to think about my system. I'm facinated by horn systems and have heard several that were compelling in key respects, the ability to use a DSET such as your Melquiades amp being one. One the subject of a 'final' phonostage, my own is one of the three MFA Systems MC Reference prototypes built for CES in Las Vegas. This one, housed in an MFA Luminescence chassis is the ultimate of the three. It differs from the production version of the MC Reference in several ways. It is hard wired throughout and uses ECC88s, 12AX7s and 12AU7/AT7. The phono stage is battery-powered. I've included some photos for you to see. It is currently in need if repair. Bob Hovland took a quick look at it and identified two caps that needed to be replaced. they have been removed so you may notice them missing in the photo. This particular phonostage has the magic you talk about.

Romy I cannot upload the images. I tried using the 'insert images from gallery' button. Can you tell me how to do this correctly?
05-31-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 28
Post ID: 7501
Reply to: 7500
Good for them.

 Reggie wrote:
Did you take courses in electronics and mechanical engineering or have you learned yourself outside of a structured environment? I am very interested to become proficient in working on/modifying my own electronics. I would enjoy spending time at the workbench such as the one pictured above. 

Nope, have no structured training but juts a respect and discrimination to results, common sense and an opportunity of asking right questions. What I would like to note is that I have no specific pride of even interest in doing my own electronics and if I have somebody why would do it for me I would joyfully not have even a solder gun.

 Reggie wrote:
Reading many posts on your site has caused me to think about my system. I'm facinated by horn systems and have heard several that were compelling in key respects, the ability to use a DSET such as your Melquiades amp being one.

Reggie, I would disagree. DSET is not a key in horn systems. DSET is a way to fight with intrinsic limitation (or I would say complication) of SET topology. Horns by nature do not need DSET as they are harrow bandwidth devises…

 Reggie wrote:
One the subject of a 'final' phonostage, my own is one of the three MFA Systems MC Reference prototypes built for CES in Las Vegas.…This particular phonostage has the magic you talk about.

I never heard this phonostage but if it has that “it” then it is good for  them.

 Reggie wrote:
Romy I cannot upload the images. I tried using the 'insert images from gallery' button. Can you tell me how to do this correctly?

I really do not know – it looks like works top me. “Insert image from Gallery” is the yellow button right next to the printer buster in your reply interface. If you run some kind off the wall browser or OC then you can attach image to post.

Rgs, the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-31-2008 Post does not mapped to Knowledge Tree
Reggie
Posts 13
Joined on 05-08-2008

Post #: 29
Post ID: 7502
Reply to: 7501
Photos of the MFA Systems MC Reference
DSC01144b.jpg

DSC01145.JPG
05-31-2008 Post does not mapped to Knowledge Tree
Reggie
Posts 13
Joined on 05-08-2008

Post #: 30
Post ID: 7503
Reply to: 7502
A few more
DSC01146b.jpg

DSC01145.JPGDSC01150b.jpg
05-31-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 31
Post ID: 7504
Reply to: 7492
OK, it is over. Some preliminary follow ups.

I spent a bigger part of day today to finish the “End of Life" Phonostage, there were many things to do but it is now over. Done! Complete! Amen! I it closed up and sat in it’s permanent place.

EAR834PT.jpg

A few observations looking back. First, I spent a LOT of time trying to fine tune the RIAA curve. I use the test LP with 20-20K sweeps. I use Jim Hagerman’s contra-RIAA little tool, driving the RTA and scope from generator. I use my Wavelab’s phenomenal FFT meter driving the Phonostage into Pacific Microsonics analog-to digital (this A/D calibrated mind-bogglingly well). I usually use the Wavelab’s FFT and Phase meters to help myself to setup cartridges – very covenant. Anyhow, to my displeasure I learned that  the contra-RIAA devise was slightly off at HF, so I end up not to use it and used other means.

In the end of everything I was able to get very nice response. The response is nice and flat with 0dB at 18.1Hz and 0dB at 15.600Hz. It has plus 0.2dB from 1500 to 3500 which I feel is not a big deal. (Juts for my future reference: the values of the feedback capacitors have without de-soldering capS from the circuit are: 110pF= 136.2pF and 330pF=372pF)

 I found a very good grounding schema and the self noise this corrector of 26db+48dB=72dB gain is better than good – it has absolutely no noise. The previous adaptation had no problem but this one took noise even further – there is no difference for the system between CD input and phonostage input, and do not forget that we are taking about 109dB sensitive system.  I presume that my new construction techniques (mounting everything short point-to-point on a think copper plate that used as a ground terminal) do help. What I also detected over the second part of day playing the corrector that it looks like the gas regulation helps with good with electricity. Apparently the gas tubes shunt all power line dirt – a promising sign.

Sonic results. It is hard to say. I feel that there is no sonic difference between my former version and the new one, the new phonostage  is too fresh, the caps, the PS, the disturbed Dominus cables the total assembling - perhaps I need to return to the subject of sound after 500 hours. The new phonostage has the following changed compare to the former one:

1) Fix biasing on the second stage instead of the former automated
2) Different filament and anode PS, the anode supplies are gas regulated.
3) Better construction techniques  (the former version was my very first DIY Audio attempt since I began practicing the  US version of High-End Audio)
4) V-Cap coupling capacitors between the first and second stage
5) More immediate connection between the ET2 transformer and first grid

I did not study or observed the incremental changes, let see how it will turn out all together.

Preliminary conclusion: very good. It looks like the essence of the ET+834PT was not lost (that what I was afraid and this is why I built a new corrector and kept the original intact – just in case). The new corrector did not developed it’s full bass yet but I know the Nichicon caps and the disturbed Dominus – it shell come later. All together the sound as I expected – three is nothing alarming at this point. Some unique ET+834PT quietly are still there. For instance the ET+834PT is the only know to me phonostage that is capable to play  (if needed) without HF.  I mean any good phonostage I tried threw very high quality HF, demonstrating that analog HF might be very-very good. Only Boulder 2008 phonostage was a minor exception that was able to throw non-presumptuous HF up to a degree. The ET+834PT takes this approach to extreme – it has no HF at all and it pitch HF into the game ONLY when it is necessary. You listen it and it feels at beginning that there is not enough HF but you add .5dB and realize that it is how live Sound sounds. There is no HF in live sound; there is Space but no HF itself. ET+834PT does the necessary HF’ space tricks without actually making HF themselves. I can go on in many other specific distinctive characteristics of the ET+834PT but it is not my objectives at this point. The important is that the new procurator looks like preserve them all – God bless the smart Tim de Paravicini’s design of amplified Miller capacitance and feedback to high impedance.

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
06-01-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 32
Post ID: 7505
Reply to: 7504
"Lack" of HF, etc.

The "lack" of HF is definitely one of the wonderful things that makes one think of spending 30K on a phono stage.  Glad to hear you are "suffering" a similar "dirth" of HF [noise] with your DIY corrector.

I wasn't going to say anything, but I wondered up until I saw this "finished product" photo if you planned to run the 12AX7s horizontally...  That would have been "interesting"...

My "modern" Teflon composite caps did not take long at all to establish themselves; nothing like the "premium" electrolytics, which not only take a long time to sound decent but they also "revert" if you don't run them for a while.

Do I remember that Tim d' P. also likes to use one twin triode tube for two channels?  I am "iffy" on this conceptually; never tried it.

I know you are all stoked with FM benefits for some time now; but surely the musical treasures on vinyl are enticing, not to mention the potential?

I have also read your thoughts on VTA/SRA, but if your corrector is "articulate" then you must be pretty much stuck, needing to get it fairly close?


Best regards,
Paul S



06-01-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 33
Post ID: 7506
Reply to: 7504
“End of Life" Phonostage: what is next?

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.

Rgs, Romy


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
06-01-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 34
Post ID: 7508
Reply to: 7506
Hybridizing

The SS out does calm/quiet/clear things considerably, but there is a price for that clarity, as I have reported.

You probably already looked into JFET?

Do I "remember" that you had a stash of exotic adjustable air-core caps?  As you can tell from the question, I have not tried to run the math, but would the "trim-able" cap give you enough range to dial in the network?

The last time I ran into this, I think wound up with Audio Note tantalum R, which can do "hard" better than wire or carbon comp.  Vishay was "too much" there, as I recall, like on plates.

Best regards,
Paul S

06-01-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 35
Post ID: 7509
Reply to: 7508
I love it!
I actually woke up today at 6AM, check all settings on my arms (after a few month of not working), demagnetized the needles and was spinning records all mooring. One of the benefits that I got with new phonostage is that the grounding patters for all arms are identical and I might absolutely painlessly to flip between the arms. This morning I play mostly mono records driving from SPU Mono. I just love the result, I truly do. Funny-funny I removed yesterday my reference for this phonostage, selected by years of use, Telefunken –Sylvania-Telefunken tubes combination and put there cheap and no particularly good sounding 12AX7 (for a next 30 days I am not planning to shut this thing down). The corrector still sounds very pleasant and very much listenable and extremely peaceful for my iterated and sick audio mind. Very cool!

EAR834PT.jpg

 Paul S wrote:
Do I "remember" that you had a stash of exotic adjustable air-core caps? As you can tell from the question, I have not tried to run the math, but would the "trim-able" cap give you enough range to dial in the network?
Paul, it has nothing to do with math. It is one of the unlikeness of the Paravicini’s design. He runs feedback not to cathode but to high impedance of plate. So it is very high impedance and very low capacitance feedback (contrary to usual RIAA feedback with low impedance and high capacitance). Moreover he uses current feedback (cathode resistor) on the fist tube to raise the first stage plate impedance. Then he unites the miniature capacitance of the feedback with Miller capacitance of the first stage and et then let the combined capacitance to be amplifier by the second stage. Very slick, pay attention that the first stage Miller capacitance, the minute values of the feedback caps and the capacitance of the entire assembly are no consider in this design as parasitic but actually used for a purpose. In a classic RC design you would need relatively large caps to write the RIAA cure and you will be way beyond the range of no dialectic caps (air or vacuum). In the 834P design the feedback caps are very small values: 110pF and 330pF that allow using “nothing” as dialectic in the caps. The only thing that I would consider from here is to use doted symmetric air caps where the signal does not go over the movable contacts or the body of the cap. The only place where I see such air capacitors was inside my Rohde & Schwarz Tuner

“Rohde_Schwarz_caps

but I clearly understand that I will never found such caps…

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
06-03-2008 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 36
Post ID: 7526
Reply to: 7509
If I may be a litt;e suggestive.....
I have some ZVN0545A mosfets here for exactly that purpose of replacing cathode followers. You may like to try this starting at 2mA (250V supply, 125k biasing resistor). Did you or Dima try Soviet SSG silver-mica for the first coupler? I am using 0.175uF items for excellent results though I haven't compared to teflon.

The 834P circuit is not designed for low distortion (probably why Guy dislikes it) but for "listener-friendly" natural harmonic decay. I guess that accounts for the magic and I too have a corrector for life, though now with vintage moulded silver mica caps in place of the air vanes. My shipment of tuning caps from Ocean was destroyed by our paranoid customs!!!

Brian.
06-03-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 37
Post ID: 7527
Reply to: 7526
Mica, distortions, MOSFET and the Ocean State.

 Brian Clark wrote:
I have some ZVN0545A mosfets here for exactly that purpose of replacing cathode followers. You may like to try this starting at 2mA (250V supply, 125k biasing resistor).

Brian, and how do you find your MOSFET behaves compare the 12AX7-based cathode follower?

 Brian Clark wrote:
Did you or Dima try Soviet SSG silver-mica for the first coupler? I am using 0.175uF items for excellent results though I haven't compared to teflon.

Nope I did not try them. I have 5-6 different versions of silver-mica though and I prefer air caps. I do not know what Dima tried. He has the same corrector with Ocean State’s air caps only in place of the first 12AXy he uses Russian nuvistors

 Brian Clark wrote:
The 834P circuit is not designed for low distortion (probably why Guy dislikes it) but for "listener-friendly" natural harmonic decay. I guess that accounts for the magic….

This is big question but I would have a lot of to say. I do not think that 834P circuit is designed for any specific distortions.  I understand “distortions” differently.  You might read my Macondo Page that gives an idea how I see distortions….

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
06-04-2008 Post does not mapped to Knowledge Tree
deemon
Posts 23
Joined on 05-25-2004

Post #: 38
Post ID: 7529
Reply to: 7526
SSG
Brian , I never tried SSG cap in phonostage . SSG has a good reputation ..... but I'd prefer teflon for coupling . Mica caps , even good ones like SSG , seems too "bright" for me , but teflon sound pretty neutral .
06-04-2008 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 39
Post ID: 7530
Reply to: 7527
Of mosfets, caps and distortion.
 Romy the Cat wrote:
Brian, and how do you find your MOSFET behaves compare the 12AX7-based cathode follower?


Romy, I have yet to try. Only got them on recommendation very recently. They're cheap enough to try in a B9A plug-in without altering anything in the circuit, though perhaps a good idea to add a carbon comp resistor on the gate. I'll try and find one of those plugs in the garage and give it a go.

I have 5-6 different versions of silver-mica though and I prefer air caps. I do not know what Dima tried. He has the same corrector with Ocean State’s air caps only in place of the first 12AXy he uses Russian nuvistors


Yes but you can't use an air-cap as a coupler in that circuit. The SSGs are a whole lot cheaper than VenHaus's V-Caps.

I do not think that 834P circuit is designed for any specific distortions.


Whereas I do. deParavicini's worked on designs in Japan over several years and became familiar with the  research going on there in the Seventies which culminated in identifying the HD decay-spectrum as a key indicator for "musicality". I.e. a monotonically decreasing level as order increased such that each HD  component masked the following component. This occurs naturally in a single triode operating under normal conditions. When I simulated the 834P circuit two things were obvious - the level of THD was high but the aforesaid decay spectrum approximated that of a single triode valve.

For what it's worth and acknowledging it is part of a bigger picture of course.

Brian.
06-04-2008 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 40
Post ID: 7531
Reply to: 7529
USSR SSG
 deemon wrote:
Brian , I never tried SSG cap in phonostage . SSG has a good reputation ..... but I'd prefer teflon for coupling . Mica caps , even good ones like SSG , seems too "bright" for me , but teflon sound pretty neutral .


Hello Dima. In my application it is the first-stage coupler followed by an oil-type in second coupling position. This seems to work very well. However, I might try SSGs in both positions to hear if brightness prevails to a distracting degree. It would be interesting to hear SSG vs VCap. The Ven Haus should be the clear winner but just how clear would be .... interesting.


Brian.
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