Paul, I do not think that “before or after RIAA losses” requirement has any merit as no matter what kind type RIAA filter is being used it always will lose around 20dB. I do not think also that there is a “safest path” or “reasonably affordable”. In my view any topology of RIAA filters are in the same cost, even the LCR RIAA filters are in the same price scale.  The 5K or 10K LCR would be expansive but 600R is tolerable. What I mean by tolerable is that the cost of the 600R LCR deluded in the cost of total corrector of compatible sound. To make a properly sounding feedback or RC phonostage is hard and when you do it then the cost of 600R LCR filter is well consumed into the cost of the whole project.

How difficult is it to find 437As good enough for a phonostage? For commercial applications is it a dead tube. WE might produce it again when they stated to redo the tubes but the existence of the Russian 6C45P pretty much killed the idea. For none-commercial applications it is a fine tube and if somebody has some stash of them then why do not use them?  And hard to get them new, they are expensive and mostly those 437A that let go are the noisy one, why would anyone sell good 437A?

It would be interesting to learn how much the 437A is better then 6C45P. The 6C45P are OK if they drive a lot of current. If do not use the stupid pulse version that everyone look like use and find them from 60s than the 6C45P might work out. I afraid that to find the 6C45P from 50s would be as hard as to find the 437A.  I do not know anyone who used 437A in phono. I think in Stefano case the 437A in input stage and output stage would behave differently.  Give him a few months and I am sure he will experiment with 437A, 417A, 6C45P, 3A/167M in different configuration and will decide what to use. Output tube in Thomas Mayer phono might be pretty much anything.

BTW, the stand alone LCR phonostages are not the optimum configuration in my view. It would be fun to have a full preamp with one two inputs with LCR RIAA, then you can optimize the amount of stages and do not use the preamp output stage as phonostage’s output stage, effectively dropping one active stage.

Romy the Cat wrote:

How difficult is it to find 437As good enough for a phonostage? For commercial applications is it a dead tube. WE might produce it again when they stated to redo the tubes but the existence of the Russian 6C45P pretty much killed the idea. For none-commercial applications it is a fine tube and if somebody has some stash of them then why do not use them?  And hard to get them new, they are expensive and mostly those 437A that let go are the noisy one, why would anyone sell good 437A? It would be interesting to learn how much the 437A is better then 6C45P. The 6C45P are OK if they drive a lot of current. If do not use the stupid pulse version that everyone look like use and find them from 60s than the 6C45P might work out. I afraid that to find the 6C45P from 50s would be as hard as to find the 437A.  I do not know anyone who used 437A in phono. I think in Stefano case the 437A in input stage and output stage would behave differently.  Give him a few months and I am sure he will experiment with 437A, 417A, 6C45P, 3A/167M in different configuration and will decide what to use. Output tube in Thomas Mayer phono might be pretty much anything. The Cat

twogoodears wrote:

Yes Roman... I feel pretty like I entered a sort of "cul de sac", tube-wise... I contacted, few months ago, Western Electric USA and they told me that, at USD 750 ea. they have "plenty" of N.O.S. WE 437A... I've been able to find and purchase for a much lesser amount, 9 tubes of different batches but in matched Mu pairs... despite Thomas' testing and matching and myself at the wallet commands;-) the consistency in perceived balance between left and right channel proved to be quite tricky, worth careful settings and several tubes swappings and combinations.

Yes, I did the same. What in 2000 I got Lamm LP2 that used 417A I also did call to WE and asked them about the 417 tubes. They told that they have them and gave me some absolutely ridicules price, with a first price drop of a few dollars after 500 tubes. I do not remember exact price they gave me but it was way in the realm of fantasy. Then I went “to word” and sourced of 417A, learning the 95% of them not usable. BTW, the $8 Raytheon 5842 was a very good sounding alternative to 417A. It had less flashy name but I learned that 5842 were more stable in quality primary because you buy a party of new 5842 vs. you buy the 417A as new that somebody have tried and find them to noisy – so I felt that the whole pool of 417A was better and I would not necessarily say that WE417A sounded better then Raytheon 5842. Now the whole phonostage did not sound right, but it was a totally different story…. Anyhow, that gave me some trepidations when I think about the high Mu triodes… I have a friend in NY in whose system a perfectly operating 417A totally out of bleu when nuts and blew up tweeters in $90K speakers. The high Mu fast triodes are strange….

twogoodears wrote:

Thomas reports the Telefunken EC-8020 as much more selected at factory before reaching final users...

One of the advantage of passive EQ that you have in your phono that you can use any tubes you wish, them design is not very strict as it is my case. Let your Thomas to cook for you your phonostage with 7788 in the first stage. You Europeans know it as E810F. That tube has higher gain at lowers noise and it is stunningly stable. You can take any Telefunken E810F, replace it with another and your will be have insultingly exactly the same operational parameters. I have less success with Mulard and Philips E810F but German E810F are very-very good. It is 5W tube and it will be able to drive you 600R load.

twogoodears wrote:

The British 3A/167M still more sought after and expensive than EC-8020 and 437A and - truly - unavailable everywhere, is a much better tube than WE 437A: sure mechanically, with its metal ring socket, it is.

…and I do not know if 3A/167M is better than anything else and I do not see why the metal socket is necessarily better then plastic – the socket is not the part of the tube. It is the same 7W tube with 1K on late and Gm of 42. The 3A/167M for sue is much more expensive and much more difficult to get. I did not use it and I did not hear it is anybody installations. When you say that it is “much better” then you need to understand that audio people love to create a cult-like BS, which makes the things to be “sought after”. I do not think that it would be a huge actual different for you to use 3A/167M or 437A beside to make good pictures for your blog and let the Audio-Morons to envy. However, what I would like to point out is the fact that when you read/hear the exuberant comments from some 3A/167M users about the 3A/167M superiority then… then NEVER talk about Sound. At my time what I collected information about 3A/167M I never was able to suck of the 3A/167M users any thinking about sound that I find not even attractive to myself but even rudimentary-sensible. Sure, it does not say anything negative about 3A/167M but rather about the community of all those stupid DIYers but still I did not develope any encouragement to peruse into the 3A/167M direction.
 

twogoodears wrote:

The 6C45P was a serious alternative to WE 437A, even less consistent in performance in a tube-to-tube comparison, but I'm much more confident the next German/Italian task will be, always using a Tango EQ600 LCR, the WE 416B and 416C. It's still available for cheap and in quantity and an italian tube scholar and builder, Daniele Ansaloni http://twogoodears.blogspot.com/2009/09/western-electric-416-b-and-c-golden.html (who built and listened to such a phono stage with full Tango (old) irons) says - in perfect italian: "Wunderbar!"

I never heard the WE416B/416C, not about them but from what I just have seen in their sheets and in the description of their design they might be very interesting tubes. The only thing that you need to watch with them is my Vacuum Cap Syndrome. The Vacuum Capacitors are the best caps to use in my phonostage but there is one ugly factor. The Vacuum Caps are high voltage and the contact surfaces are very large. When you have you .25mV signal coming from your cartridge across the 38ga cable then suddenly you expose a plate of Vacuum capacitor with a contact of 30mm diameter than the rapid change of the conductive volume is affect sound very negatively (read my comments about the superior  posts:  http://www.RomyTheCat.com/TreeItem.aspx?PostID=11807)

twogoodears wrote:

Last but not least, another viable tube for phono-stages - still elusive, BUT not hideously priced, yet - would be Western Electric 436... worth investigating.  The WE 437A are very nicely sounding in my system

And what is wrong with your Sound of 435 that might encourage you to look into 436?  :-)

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=432

twogoodears wrote:

...yet as Roman pointed out, I hope the search be not over... as it's a BIG part of passion.

twogoodears wrote:

Maybe someone read this http://twogoodears.blogspot.com/2009/05/we-437-based-phono-stage-solid-rock-did.html, worth reconsidering its design - also (partially) using WE 437A - after the last posts discussion at Roman's... also worth remembering that this super-expensive phono-stage went roasted in a fire at a Munchen Audio Fair, last spring...

From the picture it looks like they have a phonostage stage as a part of a full-blown preamp – that is a right direction to go. However, I really hate the Audio Consulting and the way HOW they think and WHAT they do. I have no negative experiences with them or anything like this that makes people to hate but the whole whorish and completely empty philosophy of sound from Audio Consulting is so disgusting to me that I feel a need to voice it. It is no surprise that the “sound” that Audio Consulting trying to promote made the 6moons cretin so “overwhelmed” (even I did not read the 6moons article).

Paul S wrote:

I have never used the 417 or 437, but I have heard plenty of whining from folks who do.  They often pay a small fortune for "special" tubes and wind up with tubes they simply cannot use for low-level input.

Paul S wrote:

Lastly, gain and impedance in the input or output tubes absolutely affect the sound of a tube phono stage.  As Roger Modjesky pointed out, these factors actually wind up affecting the "RIAA Curve" itself in any LCR RIAA circuit, whether "split" or "continuous".

Thomas Mayer wrote:

I never had a lot of trouble with high transconductance tubes. I use the EC8020 a lot.

Stefano, you might look into this EC8020. I never seen it but just looked into the datasheet and it looks very interesting tube and it might be better candidate to your phonocorrector’s fist stage then the WE 437A. I generally, under other equal conditions, prefer Telefunken/Siemens tubes to any other tubes. My second choose would be the older British tube and only then I would look into all of those RAC/WE/Raytheon. Of cause it is a gross generalization but … I am comfortable with this generalization.

Thomas Mayer wrote:

This is true for RC RIAAs, not for LCR RIAAs. This is one of the big advantages of the LCR technique. The network has a constant 600 Ohms input impedance, if it's terminated by the proper 600 Ohm value. Variation in the driving tubes rp does only affect the loss in the network, but the loss is always the same over the frequency band. So the RIAA curve will not chabge when the tube detoriates or when tubes are changed.

That is not necessarily true. I think any passive RIAA would not be a subject of curve variation with tube aging. Moreover, I would take this argument even further. Even if we have a feedback RIAA, where the gain of the open loop is in the task of direct shaping the RIAA curve, than I feel that aging of the tube and minor change of their gain is not truly a practical issue. There are a lot of people out there who go totally crazy with writing the accuracy of the RIAA curve with .05dB precession. I feel that it is absolutely not necessary. If you want RIAA precession then have your corrector to run multiple curves as 50% of records out there are NOT RIAA pre-equalized. It is not to mention that there was a huge deviation in the RIAA equalizers during the cutting of the records. From what I see the .25dB-.5dB accuracy is plenty for normal record playing. The MC R loading, MM C loading, VTAs, the cartridges themselves give much higher discrepancies then .25dB. so, if you look how the small tubes change gain with time then in most cases it is not significant to affect RIAA too mach. Unless your LP is the only source you use and unless you run your phonostage a few hours each day I would not feel that the tubes aging might be a factor in RIAA running away.

perrew wrote:

Romy, I might be confused with the passive and active, but from my understanding you prefer your active 834PT to the passive RC network and passive LCR networks. You also prefer the passive LCR to the passive RC. So 834PT>LCR>RC. If I got it right a RL network will be similar to a LCR from needing a capacitor for the ground and then additional capacitor for the amplifier stage unless the amplifier stage is direct coupled or you can use a Transformer in between, which need to be matched. If the biggest advantage from the LCR network is the RIAA curve is not altered from change in tubes is not such big advatage any longer why then choose the increasing complexity of the LCR over the simpler RC? P

Perrew,

We need to keep a perspective on what we are talking about. There is a different about what we prefer and what we use. What I prefer is RL filtration and in context of RIAA it gets converted into LCR filter. Theoretically it is possible to avoid the final cap at the bottom as well and use only pure inductance filtertration:

http://www.RomyTheCat.com/TreeItem.aspx?PostID=644

…but the pure inductive RX ides has own issuers.  That is what I “prefer” but it is not necessary what I use. We trade opinions about conceptual advantages but we do not justify that that what we use. I do use a phonostage with feedback, I like it very much and am not going to change it to LCR. (I have then LCR phonostage as well). My feedback phonostage is a different type feedback, the one that use native tube’s Miller capacitance to write the curve. Still, I have no experience to evaluate METHODOLOGICALLY PROPERLY the advantages of my type of RIAA vs. LCR RIAA.  To compare two completed phonostages does not signify a lot about the advantages/disadvantages of a given RIAA filtration method.  So, my position is my feeling that LCR might be adventitious and it is what I “prefer” as better RIAA filter. Still, I use my feedback RC, so what, who said that what I USE must be what I prefer?

Romy the Cat wrote:

I never had a lot of trouble with high transconductance tubes. I use the EC8020 a lot. Stefano, you might look into this EC8020. I never seen it but just looked into the datasheet and it looks very interesting tube and it might be better candidate to your phonocorrector’s fist stage then the WE 437A. I generally, under other equal conditions, prefer Telefunken/Siemens tubes to any other tubes. My second choose would be the older British tube and only then I would look into all of those RAC/WE/Raytheon. Of cause it is a gross generalization but … I am comfortable with this generalization.  Thomas Mayer wrote: This is true for RC RIAAs, not for LCR RIAAs. This is one of the big advantages of the LCR technique. The network has a constant 600 Ohms input impedance, if it's terminated by the proper 600 Ohm value. Variation in the driving tubes rp does only affect the loss in the network, but the loss is always the same over the frequency band. So the RIAA curve will not chabge when the tube detoriates or when tubes are changed. That is not necessarily true. I think any passive RIAA would not be a subject of curve variation with tube aging. Moreover, I would take this argument even further. Even if we have a feedback RIAA, where the gain of the open loop is in the task of direct shaping the RIAA curve, than I feel that aging of the tube and minor change of their gain is not truly a practical issue. There are a lot of people out there who go totally crazy with writing the accuracy of the RIAA curve with .05dB precession. I feel that it is absolutely not necessary. If you want RIAA precession then have your corrector to run multiple curves as 50% of records out there are NOT RIAA pre-equalized. It is not to mention that there was a huge deviation in the RIAA equalizers during the cutting of the records. From what I see the .25dB-.5dB accuracy is plenty for normal record playing. The MC R loading, MM C loading, VTAs, the cartridges themselves give much higher discrepancies then .25dB. so, if you look how the small tubes change gain with time then in most cases it is not significant to affect RIAA too mach. Unless your LP is the only source you use and unless you run your phonostage a few hours each day I would not feel that the tubes aging might be a factor in RIAA running away. The Cat

twogoodears wrote:

Actually a N.O.S. EC-8020 "diamond" is worth EUR 500+ ea., an STC 3A7167M is fetching EUR 750+ ea. (I own one N.O.S. sampler with original carton box, bought by chance for cheap, years ago) and WE 437A is at "only" EUR 350+ ea.... the only tube to be still commercially available is the Western Electric's, at USD 750 ea. (EUR 501,88)...

You got to be kidding? If the prices are in this scale then I would have problems. Perhaps not becose it is too expensive but become there is absolutely no assurance that the given bought tube will be able to work in your phonostage according it noise characteristic. I would agree that probably it worth to buy them ONCE to trey what they are all about but if I have a devise that I would really upon then I prefer to have a few spare tube. I would say for phonostage that I might settle you would need to have at least 3 pairs of tested replacement tubes for me to feel comfortable. The most ridiculously expensive tube I ever paid it was a pair of new RE604. I tested what the hype was all about and went for another tube. Now, if I did select the RE604 to stay in my amps then considering the power tube go south faster I would probably need to get 3-5 tested pairs of them to feel comfortable. It has nothing to do with rational or sanity, it is how my sick mind works. According to Zodiac I am a Cancer and like any crabs we Cancers always build the stash of possessions, otherwise we do not feel comfortable…. So, to have 3 workable pair of WE437A I would need 8-10 pairs of “random” WE437A. That sounds bitey… from another hard if  your Thomas claims that  EC-8020 is very stable then you would need just 3 pairs of them…

twogoodears wrote:

Tube market is quite strange: considering that a Telefunken VF-14 with original carton-box for Neumann U-47 classic microphones reached USD 1.000/1.200 ea. price-tags the WE 437A's appears like true bargains;-)!

And you know that 90% of this cost is not from the people who NEED them and know what to do with them but from the people, who hear the hype, buy them to learn what the hype all about. I think it would be a good idea to large dealers of NOS tubes to have trial stock of tubes.  I would not mind for instance instead of buying all those tubes that I have bought for my Milq MF channel to pay let say $500 for a weekend and to have an assortment of different tube send to me to try. Perhaps it would be a good business for somebody…

twogoodears wrote:

Now, I would probably go for WE416B or C or WE417 or Telefunken EC810F, not because I'm disatisfied with my actual LCR/WE437A, but because the cost involved in tuning and maintaining to specs, or simply obtaining the correct balance between right and left channels in such a design proved to be quite expensive... always less than any medical surgery, anyway;-)

BTW, the WE417A that I used have a habit to change gain very fast and very erratically, so if you match then NOW it does not mean that it would be matched in 3 weeks or in 3 month. I presume that WE437A will behave the same.

twogoodears wrote:

Herr Mayer and myself agreed and - all considered - that's what I ended with... a nicely sounding LCR phono stage, much better than my previous vintage preamp.

I do not know what previous vintage preamp you used, whatever vintage preamps/phonocorrectors I have seen they all where crap. In what you do you need to have a very perspective about what you are trying to accomplish. Mr. Mayer and anyone else on the technical side who might assist you with building of your phonostage are endlessly blind in what they do. They build just a phonostage as an absentminded instrument and it is up to you to make this inattentive tool to serve your purpose. You do not really need a phonostage but you are trying to construct a special sound. The knowledge that your technical associates have in design audio might not be in direct relation with your sonic objective. The DIYers would go over zillion topologies, tube and options without respect to Sound. It shall be your job to discriminate result, to navigate what they do in the direction where it shall go and eventually to say to yourself: “stop, here is where I have got what I would like to have.”

BTW, the hoodlums who are interested about Inductive RIAA might fins this link useful:

http://digilander.libero.it/paeng/inductive_riaa.htm