Thanks for the info, Tfkaudio. I might have to A/B my sound with some nice 12AX7's again in the gain stage. I think I still have the Telefuncan The Fisher 12AX7's around to compare my RIAA by ear. Now that I am listening for it I can pay closer attention to how much it is skewing my balance across the frequencies. I am working out of town again tomorrow, and Saturday going to see Zappa Plays Zappa. I will post what I hear and maybe get your comments after. |
If anyone wants to know, I am using VPI gear that I modded very much, along with Air Tight PC-1 and my prized Colibri XPW (platinum coils) that I got with about 3 hours on it and it is just breaking in now. There are so many posts that this phono stage cannot be SOTA,even with mods, but I do not agree. It is not that great with standard tubes as a stock unit, but becomes a monster if tweaked properly! |
Still talking by myself, but someone may find the info useful. I got a pair of 1970's Sylvania Gold brand 6201 gold pins and a pair of GE 5751 with the clipped getters from early 1950's from Mel (pharmacology PhD who is also expert on tubes) on here. After rolling I still like Volvo 6201 blue print best in V1, but have moved one Sylvania and one GE 5751 into the gain stages V2 and V3. Sylvania was close 2nd and GE close 3rd for best in the imput stage V1. The 5751 has the added warmth in the mids that worked well in my bright tri-amped system (class A SET OTL Transcendent monoblocks driving Ahh horns and Fostex super tweeters). |
Frogman, Thanks for joining the post. I had Telefunkan NOS 12AX7-The Fisher version, before Victor USCITY started giving me advice on the EAR 834P. It still left a dull haze and lack of detail/clarity for me. It was my first shot at tube rolling and was a big improvement over stock tubes.
I have seen posts on Mitch Singerman mods that were all favorable. David Schulte of Upgrade Company has done most of my equipment and does great work also and really transformed the unit.
Interesting dampening techniques you have with the lead. Does this absorb RFI and magnetic field radiation or just dampen and isolate from vibration?
I don't know the mm carts that you mention but might like to try one out if they are not too expensive. Generally the mm are much better priced. I only ever had a Grado- The Statement for mm cartridges and no longer have it.
I'll have to read up on the Raytheon 7025. I am getting amazing synergy out of my current combo. |
Stevecham and Frogman and especially Tfkaudio- thanks all for the tips. I am still a little run down from being sick for 10 days- but going to see Dweezil and company last night was worth the drive after working all day. After sleeping in I rolled some Telefuncan 12AX7's in and A/B'ed things. I have to agree that there was some RIAA change with the lower voltage just as you said. Like you said, Frogman, the Tele's do sound great in the V2 and V3 with the right imput tube in V1. I get a better overall balance of sound and really none of the lack of detail and focus that I felt I personally hear in my EAR phono stage with a 12AX7 in V1. The Sylvania gold pin 6201 easily beat out the GE 5751 ( though it does have lovely midrange warmth) and was very close to my still reigning favorite the Valvo 6201 blue print. You have me tweaked to hear a 7025, but I think I have spent a little much on tubes for a while. Thanks for setting me straight to listen with fresh ears and notice my bias that I had. I listened to Miles Davis Kind Of Blue Flamenco Sketches 45rpm and the first side of the new AP 45prm Dave Bubeck Take Five- which you might do yourself a favor and get a copy before they sell out- for the rolling session. Cheers you all! |
Revdog. Frogman does know his stuff. I however really get good sound with my setup with a step up transformer. It is a winding of wire that has just the right amount of turns and shielding to step up the voltage without noise. Voltage is like water pressure. Amps ( current) is like the size of the water pipe. There can be a lot of water ( like in a big water pipe) but how long it takes to fill your bucket up also depends on the pressure ( voltage). The current or amps times the voltage gives you the watts. Somebody stop me if I say something wrong. Passive preamps and attenuators add resistance to the signal path and boost the voltage. This voltage pressure is what moves your speaker-as it changes pressure high and low back and forth, making airwaves from your speaker. Passive can be the purest sound, but can also degrade the sound if the transformer is not top notch. MC ( moving coil) cartridges are high current + low voltage output and needs to have the voltage stepped up to run many phono preamps. The button is a cheap step up transformer. A better one will make a big improvement. |
Are the Telfuncan Smooth plates that much better than ribbed plates? My Fishers are ribbed plate. What do you all think? I am talking 12AX7 for the gain stage- V2 and V3. |
Slaw- glad your having fun with it. Read my simple post above again about SUT ( step up transformers) - the coil of wire that increases the voltage passively- without any active gain stage like an amplifier does.
MC cartridges are such low voltages that they have to be boosted before you put them into the phono preamplifier's gain stage in order to get a decent signal for the preamplifier. Or you can try some of Frogman's MM cartridge recommendations because they have a high voltage to start with. |
Found some good info Audio Assylum thread and Joe's Tube lore. Many agree ( Joe- and other tube experts that tell me Joe is pretty much right on on most of his analysis) that the 12AX7 is a hazy, cloudy, non-detailed tube in most circuits. IMO it is better to change to something else for V1 (toward the back of the unit). Tim DiP does say you can use a 12AU7 instead, but he recommends only 12AX7 in the other 2 spots. Apparently RIAA is handled mainly by V2. V3 is actually a cathode follower tube and some have used non matching alternatives in V2 and V3 against Tim DiP's advice with good results. I am buying a Brimar CV4004 (it better be worth the high price) for V2 and will leave the Telefuncan Fisher in the cathode follower V3, and my Valvo 6201 blue print in V1. |
Got the Brimar CV 4004 today- it is a variant of 12AX7 that went in to V2. Some one this thread had mentioned a Mullard CV 4004 for V2 being a good choice as well. The Brimar lowered my noise floor and increased the detail, but it did not match the telefuncan 12AX7 that I had in V3. My current recommendation based on my tube rolling with this modded EAR 834P:
I now have Valvo 6201 blue print in V1 ( 6201 is a 12AT7 variant), Brimar CV 4004 dated 1962 in V2, and Sylvania Gold Brand gold pin 6201 in V3. This is my best combination yet! I collected quite a few high end tubes on this journey, but should get many hours of vinyl/ tube pleasure. |
Lewm, So you are saying that attenuators made out of resistors only lower the gain by decreasing the amplitude of the wave, but they do not change voltage or current at all?
I mistakenly thought that transformers step up the voltage by adding resistance ( the coil of wire acted like a resistor).
I have used autoformers on OTL amps before to boost the voltage.
Glad you keep me from talking a fool, cause I don't have a full understanding of basic electronics- though I have been reading up.
Slaw- remind me, are you using all 12AX7 tubes?
I actually made one more change- Siemens 12AT7 1982 tube in V3 ( the Syvania 6201 Gold brand was to tight and thin- needed a looser sloppier sound to fatten it up and the Siemens works well) |
Found a clarification- thanks for pointing out my flaw Lewm. If a signal in a wire has a high enough gain, then a passive gain limiting preamp using resistors can be used to lower the signal to whatever listening level is desired, with full blast having no resistor in the circuit. These are often considered purer sounding than gain stages if you have enough gain not to need an active gain preamp.
"A resistor is a device that opposes current by reducing the voltage across it. If you look at a series circuit (a bunch of resistors and battery in series) you will see a voltage drop across each resistor, but the same current through each resistor." as one person explained.
V (voltage)= I (current) x R(resistance): is Ohm's law
Capacitors absorb preferentially low wavelengths, inductors absorb high wavelengths, resistors decrease voltage with no affect on frequency overall.
Can someone explain how transformer coils step up the voltage? |
