The mighty CAT preamps. From the SL1 Reference to the SL1 Renaissance and beyond..

MylesBAstor

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Apr 20, 2010
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With regards to the CAT preamp being able to play low output mc cartridges, let me say this about that. I honestly don’t think that you can play any mc cartridge with an output below .47mV without a lot of noise. If you say otherwise, you have a high tolerance for noise.

And let’s expand that beyond just the CAT. Any pure tube phono section simply can’t amplify low output mc cartridges without adding noise. People with minimal to no understanding of electronics simply don’t understand how low of a voltage that low output mc cartridges represent to the input of a pre-preamp or a regular phono stage. There are lots of cartridges that hover around the .2mV range and some that even dip into the .1mV range. By comparison, the average mm/mi cartridge has an output of around 4.7mV which is a huge difference.

Tubes have a noise floor which is higher than transistors and can’t be denied. As tubes age, it’s common that they become noisier. When you are trying to amplify a signal that is .23mV for example, you are amplifying a signal that represents .00023 V. No matter how you cut the mustard, you are into the noise floor of the tubes. If you love the sound of low output mc cartridges and you don’t want the signal riding on a bunch of noise, you are forced to go SS or use a trafo. I prefer to use a SS phono section and keep the noise out. Anyone want to buy a Counterpoint SA-2 pre-preamp??

Understand what you're saying about noise, but not so sure about that. One thing that one also must consider is the amount of gain in your line stage. Many line stages, because of digital, now are only about ten to fifteen dB; CJ tends to be the exception with almost 25 dB of gain in their line stage. So you can have 53 dB in the cj phono and 25 dB in the line and if you have a sensitive amp (say 0.75 mV instead of my ART's 1.8 mV :( ), one can use about .3 mV (also some cartridges like the Benz, sound like they have more output than they are rated--and it's not due to the way the output is measured).

That said, I'm finding I want the gain in the phono as long as of course, it doesn't overload the line stage. With the GAT, I find around 60 to 62 dB optimal now (with the insensitive ART amp)

Two, the phono sound best with the gain in the phono eg. if we're talking a total of 80 dB, 60 in the phono and 20 in the line or even 65/25.

Next, there are some "pure" phono stages such as the Doshi and TW Acoustics that have 60+ dB and sound darn quiet. The question, though as always, is for how long will the phono stage sound quiet. And you know that not just any tube will do; one has to carefully select for these low noise tubes.

Lastly, I'm using the Allnic phono with a very unique SUT that gives me the best of both worlds. And it wasn't until the Allnic that I liked the sound of a SUT!
 

DaveyF

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Jul 31, 2010
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With regards to the CAT preamp being able to play low output mc cartridges, let me say this about that. I honestly don’t think that you can play any mc cartridge with an output below .47mV without a lot of noise. If you say otherwise, you have a high tolerance for noise.

And let’s expand that beyond just the CAT. Any pure tube phono section simply can’t amplify low output mc cartridges without adding noise. People with minimal to no understanding of electronics simply don’t understand how low of a voltage that low output mc cartridges represent to the input of a pre-preamp or a regular phono stage. There are lots of cartridges that hover around the .2mV range and some that even dip into the .1mV range. By comparison, the average mm/mi cartridge has an output of around 4.7mV which is a huge difference.

Tubes have a noise floor which is higher than transistors and can’t be denied. As tubes age, it’s common that they become noisier. When you are trying to amplify a signal that is .23mV for example, you are amplifying a signal that represents .00023 V. No matter how you cut the mustard, you are into the noise floor of the tubes. If you love the sound of low output mc cartridges and you don’t want the signal riding on a bunch of noise, you are forced to go SS or use a trafo. I prefer to use a SS phono section and keep the noise out. Anyone want to buy a Counterpoint SA-2 pre-preamp??

Mark , I used to own the original Benz Ruby, which had an output of 0.4mv. Through the CAT I had no problem with noise, which I must admit was somewhat of a surprise as I was expecting noise issues.:cool:

Basically, I agree with you as to the ability of tube phono stages to amplify very low output cartridges, however, I do think that there are several variables involved....the size of the room being among them.
 

karma

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Jun 17, 2011
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Next, there are some "pure" phono stages such as the Doshi and TW Acoustics that have 60+ dB and sound darn quiet. The question, though as always, is for how long will the phono stage sound quiet. And you know that not just any tube will do; one has to carefully select for these low noise tubes.

HI All,
I agree with this. But, I also agree that a .2 mV cartridge is a tough nut to crack. For years I had been using the ARC SP-11 Mk2 preamp for my .2 mV cartridges with great success. This preamp is a hybrid design. The phono stage first amplifier is an FET followed by a tube. It is essentially silent.

When I decided to experiment with an all tube phono preamp I was very skeptical concerning noise. I bought an Aesthetix Rhea for the experiment. The Rhea turned out to be much better than I expected. True, it's not as dead quiet as the SP-11 but from my listening position the noise is not not perceptible. To me, that is good enough. I do not see this as a problem. To quibble about noise that is not perceptible is an exercise in theory, not reality.

I currently have 3 low output MC cartridges connected to the Rhea. One is .2 mV, another is .4 mV and the last is .5 mV. The Rhea handles all three with no problems. The Rhea actually could be set for gains up to 70 dB but I have not found that to be necessary. I run the gain at 60 dB. As you probably know, the Rhea can be set up from the front panel or a full function remote. This makes experimentation with gain and loading very simple and encourages playing around for best results.

In short, it seems that all tube phono stages can be completely good. I'm sure that tube selection is critical. My Rhea is using the original tubes supplied by Aesthetix.

Sparky
 

mep

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Apr 20, 2010
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Myles filled in some other variables that are part of the total equation. The gain of the line stage plays a role as well as the sensitivity of the power amp and the sensitivity of your speakers. Now let’s throw in your average listening level into that equation. The louder you listen, the more likely noise is going to be a factor. If your tendency is to listen at very low levels or what I would consider to be unrealistically low levels (i.e.; if the music was being played live, it would never sound that low in volume), that will certainly help with noise. I tend to mash the gas pedal.

Getting 60dB of low noise gain from an all tube phono stage (and crossing your fingers and hoping it stays low noise) is damn near asking for a miracle. It is going to take pairs of tubes in parallel in order to attempt to pull this off which of course gives more opportunity for noise to creep in. But then, as a *former* dyed in the wool tube lover, I know that to own and use lots of tubes requires certain masochistic tendencies. Sometimes I can’t take the abuse anymore and I get rid of my tube gear and go SS only to find that I can’t convert and I flip back to tubes for more abuse. I think I may have come up with a combination of gear now that will wean me once and for all from tubes (with the exception of my Ampex 350s). Time will tell, but for now it feels good that the tube beating has stopped. And I do see the irony that two of the three SS pieces I recently bought are broke and need servicing and are back at Krell waiting to be repaired.
 

karma

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HI mep,
I try to scale the volume to the music being played. But this is not always possible and still be realistic. For example, a symphony orchestra is very difficult due to the dynamic range. But a jazz group is easy. Perceived listening distance in the venue is also a variable. There are hints in the recordings and I do the best I can.

Often, it is not possible to know what a proper scaling might be. For example, a studio recording has no references. So, again, I guess.

The point is that I have no volume habits. I can't characterize my listening style as loud or soft or anything. It is totally program dependent.

From my point of view, listening volume is as much a part of the high fidelity experience as any other factor. Accuracy for volume is as important as, for example, frequency response. Remember, we are after HIGH fidelity not simply loud. Composers take these things into consideration. So should we.

Sparky
 

andromedaaudio

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Well stargate how ist the audioresearch /cat contest playing out .
I have the ultimate mk 2 pre now running for half a year and i must say , its special stuff very very good in my opinion
 

andromedaaudio

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Actually i might do that soon , the phono is not as quit as it was , and i bought the unit second hand so i dont know how much hours the tubes have on them .
any recommendations / brands ???
I am also in the proces of getting a 4 year old JL 3 maybe , any idea how long the JL 3 tubes last .
He doesnt want to give a good price on the krells so i dont now if its gonna happen
 

DaveyF

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Jul 31, 2010
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As you probably know, the phono tubes are the most critical to get low noise. With that said, IMO, NOS tubes in that stage are very nice....I particularly like the NOS GE smooth plates in this area and if funds allow, Telefunkens or maybe better still Ampex Bugle Boys.
As for the line stage, I have experimented with JJ's, EAT's and Mullards....prefer the EAT's...(again budget dependent).
As for the JL3, and with all tube amps, the tubes are much more stressed in this application than in the preamp. I would say that depending on the amount of use in the 4 year life of that amp, that a tube replacement could be imminent and should be expected:(.
I am about to replace the driver tubes in my ARC D70mk2 and they are only about one(1) year old:(, but beginning to exhibit noise....I am using JJ's and GE NOS in that area and I think that the NOS tube ( The GE's) were probably not that strong to begin with, plus the JJ's are notorious for this kind of problem. ( Better suited to a preamp section than used in an amp driver section, at least IMO). I will be tube rolling again into the amp. Sometimes, one has to experiment a little:D
 

andromedaaudio

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Thanks , we also got some tubespecialized shops here in holland and i will ask them for some quit ones also , .
Its not that i dont have the funds , but i want to retire when i am 50 and live in the sunshine.

hj
 

DaveyF

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HJ, I am going to roll some NOS Mullard Cv4003's into the line stage. I think these may well be the best option for the CAT. Will check back once they are installed...should be by next weekend when we shall see.
 

andromedaaudio

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Hi davey great, looking forward to the results .
I changed the 2 JJ E 88CC phonostage tubes for svetlana 6n1p type tubes as they are similar " 6N1P tube, Double triode. Equivalent 6DJ8 = E88CC = 6922"
I dont go back , the result is not insignificant , quiter (could be because they are virtually new ) , the layering improved , the sound got symply more authentic

Almost similar : http://www.4tubes.com/DATASHEETS/SCANS-Original/!1Numbers-0--10/6n1p-all-versions.pdf
 
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DaveyF

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HJ, contrary to what some people seem to believe, I think that rolling tubes into the CAT can produce a very nice upgrade.

Glad to see that you are getting great results on your CAT.:)
 

flez007

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Both the CAT and First Sound preamps have been in my short-list for years.... Once I get tired (again) of SS then I might move on....
 

mep

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HJ, contrary to what some people seem to believe, I think that rolling tubes into the CAT can produce a very nice upgrade.

Glad to see that you are getting great results on your CAT.:)

I never said you couldn’t get a *better* sound by rolling in tubes, I Just said you need to be careful. It’s not a given that if you go out and buy some Mullards, Telefunkens, Amperexes, Valvos, Siemens Halske, or any of the rest of the usual suspect high-end ultra expensive NOS (you hope) tubes that you will automatically make your tube gear better. There is a big difference between saying you can’t do it (which I never said) and the fact that you need to be careful.

When you buy supposedly NOS tubes on Ebay, it truly is a crapshoot. Some peoples’ idea of what constitutes NOS is laughable. Some people think if the tubes are only ‘slightly’ used that makes them NOS. When you buy expensive NOS tubes, how do you know if the triode sections are matched? How do you know if they are noisy and/or microphonic? You don’t. You gamble with your money and hope you come out ok. Sometimes you do get lucky.

Buying tubes from the designer/manufacturer who has carefully selected them through testing and graded them is a safe bet. Buying tubes from Kevin Deal or RAM labs is another fairly safe bet. Buying tubes from Ebay or Audiogon is not so safe.
 

DaveyF

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Jul 31, 2010
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Hi davey great, looking forward to the results .
I changed the 2 JJ E 88CC phonostage tubes for svetlana 6n1p type tubes as they are similar " 6N1P tube, Double triode. Equivalent 6DJ8 = E88CC = 6922"
I dont go back , the result is not insignificant , quiter (could be because they are virtually new ) , the layering improved , the sound got symply more authentic

Almost similar : http://www.4tubes.com/DATASHEETS/SCANS-Original/!1Numbers-0--10/6n1p-all-versions.pdf


HJ, I listened to the rolled in NOS Mullards last night and tonight. A nice improvement over the stock tubes that I had in the line section. The biggest gain seems to be had in the CAT's ability to portray depth. The CAT wasn't a slouch in this area before, but now it seems to open a window that is several feet deeper and slightly wider than before. I rolled in the lowest noise Mullard CV4003 from Kevin Deal and the noise floor has dropped to some degree. Not a huge difference here, but worthwhile and along with the increased depth reproduction, an easy recommendation.

I posted more about my findings on the Thread: "Depth" the final frontier.:)
 

andromedaaudio

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Nice one davey ,i do like depth in the presentation as well, as long it doesnt give up on the sometimes upfront presentation , if it expands the outer limits of the presentation i like it , i dont like it when the image is totally only/behind the speakers
i might buy from kevin in the future , but at the moment the line /pre are low noise enough.
i ll look into the other thread

hj
 

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