Zenbret
A simple transformer consists essentially of two coils of insulated wire. In most transformers, the wires are wound around an iron-containing structure called the core. One coil, called the primary, is connected to a source of alternating current that produces a constantly varying magnetic field around the coil. The varying magnetic field, in turn, produces an alternating current in the other coil. This coil, called the secondary, is connected to a separate electric circuit.
The ratio of the number of turns in the primary coil to the number of turns in the secondary coilthe turns ratiodetermines the ratio of the voltages in the two coils. For example, if there is one turn in the primary and ten turns in the secondary coil, the voltage in the secondary coil will be 10 times that in the primary. Such a transformer is called a step-up transformer.
The cartridge is the source of alternating current that the primary winding sees.
If you like equations : Power = V(volts) x I(current)
and VI(primary) = VI (secondary)
The transformer takes the high current low voltage from the cartridge and converts it to higher voltage lower current.
Because of the low current after the transformer, the interconnect from transformer to pre should be kept as short as possible.
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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? |
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) |
Zenbret: I was having fun but working hard at the same time. I guess I failed to mention I'm using a BOb's Cinemag 3440 w/ Dyna Karat D3. I'm in the process of listing my system, so it will take a while to complete. In what could only happen to me, last weekend I was using my motor enclosure design and the sound seemed different than ususal which is mainly why I decided to experiment with tubes again. Found out later that night my enclosure had split ( part of it was made from Purpleheart, I'm assumming it hadn't completetly dried. anyway, it changed the character of the sound, thats's when I started another day of re-experimenting. Luckily, I had a replacement (upgrade enclosure already in the works and installed it Tuesday). After tube swapping a good bit this week I'm back close to where I started. Siemens in V1 @ V2, Tele in V3. The enclosure works very well. |
Zenbret, You wrote, "Passive preamps and attenuators add resistance to the signal path and boost the voltage." That statement is kind of a mess. Some passive preamps do employ transformers or autoformers as "volume controls". Such devices can change the ratio of voltage to current of an audio signal (i.e., for any increase in V there would be a proportional decrease in current, or vice-versa; it's the law according to Ohm). But there is no free lunch, because they are passive, which by definition means they add no gain. A conventional attenuator, of which there are several types, is purely resistive. It also can add no voltage gain, because such a device is also "passive". A "resistive" attenuator is only able to decrease the amplitude of the signal that passes through it, via presenting a resistance to that signal. The subtracted energy is dissipated as heat. |
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. |
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. |
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. |
Information overload. The other two posts I made aren't up yet, I've made one more tube change. I put the two Tele's in V2 @ V3, (still have the Seimens in V1). It's obvious that the Tele smooth plates are more sonically neutral than any of the other tubes I own. I feel the Seimens have an edge in bass power/extension,... maybe slightly unrealistic in the treble region. If I had 1 more, I'd try them in all 3 positions. |
OK, I switched to the Bugle Boy in V2. Less open, only a hint of the bass the Mullard had, (soft sounding). Put the Mullard back in.
I'm working too hard, party people. Time to sign off and enjoy. |
This thread got me wondering about my tube compliment. In the context of my system, these are the changes I made today while listening to Elvis Presley "Live From Memphis" Speakers Corner,. The tube orientation I previously mentioned had a little "spotlight" effect. I had previously used (2) 60's Seimens in V2 @ V3, then went for the Mullard in V2. The Mullards are warm with nice bass, however they are not the greatest for transparency/dynamics. This was a nice compliment to the other tubes, but too much of a good thing. Trying another Mullard in V3 produced a even warmer sound that I'm not very happy with. I then left one Mullard in V2, @ switched the others so the Tele is in V3 and the Seimens is in V1. Things are pretty nice now. Somehow I get the feeling of trying a Bugle Boy in V2 to replace the Mullard. Maybe later, will report back. |
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. |
As Frogman stated earlier, and I'm paraphrasing, the tube compliment you find most pleasing will be according to your own tastes, preferences and components/set-up. I've tried a few,( no where near most of you) and the Sylvania black plate, steel pin, 5751s were a let down in multiple configurations. While I'm not yet finished listening to different tubes, my current favorite set-up is V1 Telefunken smooth plate, V2 Mullard CV 4004, V3 60's Seimens. That's just me.
Mine has no internal mods. Replaced the stock RCAs with chassis mount WBT knock-offs. IMO, aftermarket power cord and isolation makes a substantial difference for the better. |
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. |
The two parts are most likely the two SUT's (step up transformers). The "MC stage " is comprised of the MM stage+SUT's. You may find this thread to be helpful:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1278350882&read&keyw&zzsut+shootout
Food for thought: The EAR sounds much better (in absolute terms) without the SUT's in the signal path. Have you considered a top MM cartridge? In my experience, with anything less than a top MC, I get better results with a good MM and no SUT's. Good luck. |
I'm wondering if you guys could help me out as EAR has been less than helpful. A long time ago I purchased an 834p that was supposed to be mc and mm - it has the switch - the box says so etc. - but come to find out from my tech there is no mc stage! The two parts for it in the back corner aren't there. Talk about frustrating - anyway, could anyone tell me what those two parts are exactly (OEM) so I can have him put them in? EAR wants a gob of money for them but wouldn't tell me what they are. |
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! |
Frogman no offense taken and I want to be clear that I did not get the recommendation to try a 12AU7 in V3 from Audiogon members; it was from another popular but unmentionable site that, more and more, I have shied away from. |
Stevecham, to be clear, I didn't mean to suggest you were being silly. I was referring to then references you cited. Regards. |
As I mentioned in my first post, it is not the type of tube that matters as
much as wether that particular tube (in your case a 12AU7) is a good
sounding tube or not in it's own right, and complements your setup and
your tastes; as long as that variant works in a particular circuit, of course.
I find it more than a little silly that someone would suggest that 12AU7's
as a group improve bass; it's simply not the case. Having said that, the
right 12AU7 can sound very good in V3. I sometimes use a German
Amperex 12AU7 in V3 and it sounds excellent, with a very refined and
smooth, detailed sound; although not as full-bodied as my Tele 12AX7's
nor Raytheon 7025's.
Another example: I don't know how often I hear guys say that 5751's are
the ticket in this phono stage. They then go out and buy inferior 5751's,
and wonder what the hoopla is about.
BTW, the lead bars are for dampening. I never considered that they may
be help shield RFI. They just might especially considering I don't use the
cover. Regardless, I find them very effective in really tightening things up,
and improving definition. |
As I have read elsewhere, in other threads, using a 12AU7 in V3 has been cited to improve bass. So last night I tried the experiement with two different 12AU7s (an EH and a JJ) in V3 (the position closest to the front of the preamp).
This did NOT improve the sound at all.
I found it to be etched and bright, and not at all improved in the bass. Replacing the Gold Lion 12AX7 brought back everything into balance and focus. |
I replaced the three tubes with current "Genalex Gold Lions," selected for low noise (TubeDepot) and, after five years of owning and tube rolling this preowned stage, this phono pre simply sounds wonderfully magic now. Previously I had tried NOS Telefunkens, JJ standard ECC83 and ECC803s and gold pins (both selected for low noise), Tungsol, Ei regular and gold, Mullard (new version), EH, Sovtek LP and LPS (both low noise selected), as well as the stock "dPS" 12 AX7s it came with. Those Gold Lions are certainly worth the price. |
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. |
Just a note... Tube V2 MUST be an ECC83/12AX7 or RIAA equalization will not be done correctly. If your system sounds better with a lower voltage tube in V2, then I'm guessing you prefer boosted highs and muted lows.
I've replaced V1 with a 5751 and it sounded good, but currently have a Brimar 12AX7 in there. Also sounds very nice.
Fyi... my unit has the full Mitch Singerman mods.
Tom |
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. |
Zenbret, I too am a fan of this phono stage, and have had it modified by Mitch Singerman with outstanding results. Additional tweaks that I have found to be very effective are the use of BDR cones underneath, and use of the unit without it's cover and weight placed on top for dampening. I use lead bars covered in black cloth tape. Lastly, particularly if your unit is an older one where the circuit board is not attached all the way around it's periphery, the use of small sorbothane squares directly underneath the board for extra support and dampening also helps.
Have you tried a good MM cartridge yet? The EAR really shows it's
potential with it's MM stage (no SUT's). I never imagined that a MM would best my VDH Grasshopper, but an Acutex 420 STR, or Empire 4000D do exactly that. Not necessarily that the MM's are superior to the VDH in absolute terms, but that the EAR minus SUT's is superior.
I am not a proponent of the idea that 5751's as a family or 6201's, or whatever are superior to 12ax7's. It depends on the particular 5751 or 6201. For me, in my system, nothing has yet to beat good Telefunken smooth plate 12ax7's, and biggest surprise of all (and I have tried them all) Raytheon black plate 7025's. Check them out, you'll like them. |
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). |
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! |
