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#1
Posted to rec.audio.tubes
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PHONE PREAMP
Hi
where can i find quality tube phono preamp schematics? Thanks ec |
#2
Posted to rec.audio.tubes
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PHONE PREAMP
On Feb 26, 3:45 pm, "ec" wrote:
Hi where can i find quality tube phono preamp schematics? Thanks ec I put a search on dogpile.com using just those words... 60+ hits. Lots of chaff, but a few that looked at least OK. Naturally, Turner Audio figures highly in the "at least OK" hits. Peter Wieck Wyncote, PA |
#3
Posted to rec.audio.tubes
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PHONE PREAMP
In article .com,
"Peter Wieck" wrote: On Feb 26, 3:45 pm, "ec" wrote: Hi where can i find quality tube phono preamp schematics? Thanks ec I put a search on dogpile.com using just those words... 60+ hits. Lots of chaff, but a few that looked at least OK. Naturally, Turner Audio figures highly in the "at least OK" hits. Did you find any that you thought were better quality than "at least OK"? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#4
Posted to rec.audio.tubes
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PHONE PREAMP
On Feb 26, 5:16 pm, John Byrns wrote:
In article .com, "Peter Wieck" wrote: On Feb 26, 3:45 pm, "ec" wrote: Hi where can i find quality tube phono preamp schematics? Thanks ec I put a search on dogpile.com using just those words... 60+ hits. Lots of chaff, but a few that looked at least OK. Naturally, Turner Audio figures highly in the "at least OK" hits. Did you find any that you thought were better quality than "at least OK"? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ John: With respect, a home-brew phono-pre-amp is far down the line for me in terms of what I feel qualified to attempt. Accordingly, I am not really qualified to judge other than on the source of the design. Patrick Turner appears to be a good source. Otherwise, the commercial designs I have in present use work fine for me (AR, Revox, Dynaco, Fisher & Harmon-Kardon, some tube, some SS). Peter Wieck Wyncote, PA |
#5
Posted to rec.audio.tubes
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PHONE PREAMP
ec wrote: Hi where can i find quality tube phono preamp schematics? Thanks ec See the preamps pages and re-engineering pages at http://www.turneraudio.com.au |
#6
Posted to rec.audio.tubes
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PHONE PREAMP
Bret Ludwig wrote: On Feb 26, 8:07 pm, Patrick Turner wrote: ec wrote: Hi where can i find quality tube phono preamp schematics? Preamps are not too challenging to build. If you want one with lots of rotary switch selectable features such as the classic commercial ones that are convenient and spouse-friendly the issue becomes getting the switches. Rotary switches are more or less modular and you build them up or specify what you want but it can get expensive and time consuming. Many many many people have built Marantz 7 clones. Variations include using octal or other miniature tubes or even FETs in places, getting rid of the tape sections, transformer coupled outputs (the ollies have developed a taste for the WE transformers for this even though they aren't that great) etc, etc. The first and most famous M7 clone is the factory Mc C-22. They are as identical as twin sisters with a Horns of Venus. In my opinion the best of the tube phono sections is that shown in the German language book, "Audio-und-Gitatrrenschaltungen mit Rohren". Pat Turner has a copy. I know he does. It's a two stage design. Yeeeeaaaah, and I do have paper copies of something in German that someone so kindly sent me. But when I saw the schematics with 12AX7s I wasn't so awfully keen to chuck out what I have for 12AX7s. I don't have an electronic copy I can send along to anyone who wants one. But....if you are not primarily using vinyl as a source....your efforts are best directed to not having any preamp at all. You want a CD or universal player with a output section that will provide 0 dB into a relatively low impedance load. It's doable with tubes or discrete or op amp solid state. True, cd source just needs a 20k pot straight into the power amp. The opamps in the cd player have very low Rout, and usually a buffering resistor. Patrick Turner. |
#7
Posted to rec.audio.tubes
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PHONE PREAMP
Here's an excerpt from my notes on the subject:
#RIAA schematics: http://www.kabusa.com/frameset.htm?/index.htm has curve calculator Balanced - general http://www.dself.dsl.pipex.com/ampin...d/balanced.htm Balanced - ss http://www.klaus-boening.de/html/schematics.html#MKIII http://www.klaus-boening.de/html/phonostage.html http://www.quadesl.com/pdf/icphono.pdf http://www.chipcatalog.com/Datasheet...4216522E64.htm ina103 data Balanced - tubes http://www.tubecad.com/july99/page9.html http://www.rintelen.ch/pdf/DIY/Anastasia.pdf I have built the single ended 5842 preamp and the balanced 5842 preamp as described in the second edition of the Morgan Jones book. They both are very good performers. The designs are very well described. They both will accept 7mV input easily http://www.members.iinet.net.au/~quiddity/audio.html http://www.vacuumstate.com/schematics/rtp3b_s.gif Single ended - ss http://www.hiendfi.com/modules.php?n...article&sid=95 http://www.geocities.com/rjm003.geo/.../diy_pho4.html phonoclone http://www.passdiy.com/pdf/pearlphono.pdf Pass Pearl Single ended - tubes http://www.triodeguy.com/other_projects.htm Cascode http://www.izzy-wizzy.com/audio/preampnew.html http://www.lurcher.org/nick/audio/Phono-2.gif http://www.lurcher.org/nick/audio/Phono-1.gif http://www.rintelen.ch/hifi/lil_sis.pdf http://geek.scorpiorising.ca/contri...hono_preamp.gif The pre was actually designed to go into my "Ultimate Preamp" project. The mWCF is not really going to be DC coupled to the stage. There will be a cap and the selector switch and volume control in there. I just left it in to do the noise and THD tests as accurate as possible. (haven't settled on the line-gain tube yet, 6N6P or 12B4. Though I may DC couple that into the mWCF after all...) For a standalone phonopreamp, just leave the 120R||100uF cap out completely. The 10K tail end resistor's sole purpose is to bleed the static charge off the 4.7uF polycap I implamented a suggestion by SY over at diyAudio to reduce the first LED's dynamic resistance by tossing some more current through it. I wasted to keep this simple, so I skipped the CCS idea and went for straight resistive divider. The 56K/2W resistor coupled with the 100uF cap would take care of any supply noise. Any more noise injected by the 10K to the LED, would be for all practical purposes be bypassed to ground by the improved dynamic resistance. We have a total of ~6.3mA running through the LED now, keeping the resistance below 10 ohms and probably closer to 5. I also decided to clean up the schematic a bit around the mWCF (which is now a true WCF) and parallel two LED's, since it's drawing 16mA. I've also added measured voltages. The second attachment is the noise from this thing, even though it's spread out on a breadboard, looking like my typical mess. All the power supply harmonics were because to make this thing portable, I just slapped on a pair of 1N4007's to a Hammond 269GX I had laying around and AC fed the heaters (lifted 40V above ground). THD measurements were interesting. First time around, I ignored the 2nd harmonic. Well, all there IS from this thing is 2nd harmonic (seriously, none higher) and the fundimental difference with the 2nd harmonic tracked perfectly regarless if the input was 2mV, 1mV or 100uV. So, THD figures are regardless of input level. 30Hz - 0.4% (-48dB) 100Hz - 0.79% (-42dB) 1KHz - 0.45% (-47dB) 5KHz - 0.22% (-53dB) 10KHz - 0.13% (-58dB) http://geek.scorpiorising.ca/GeeK_Zo...31339#msg31339 ETF winner 2005 http://www.triodefestival.net/forum/...4f4df23a23c f The phono amp itself is simple and straight-forward: 6SL7 (or ECC35) input tube, one half for each channel, anode out into a passive RC RIAA, second gain stage is done with one EC86 per channel (I could have used a ECC88 or 6N1P but I wanted a bit more gain). The tubes all have auto bias, decoupled with 'naked' BG-N (stripped from their plastic wrapping). Rs are mostly selected AllanBradleys, Cs in RIAA are 1950's PIO (WestCap and the like) selected for 0,2 dB accuracy, output caps are AN-Cu. So nothing shocking here. In my opinion, what makes the difference is the power supply. In the amp, the phono circuitry itself occupies 10% of the physical volume, the power supply 90%. It starts with 6X4, followed by a CLC smoothing filter (first C is kept rather small). Mains transformer and chokes are C-cores. I use no electrolytics in the HT supply. I can do without and still arrive at low noise levels because of a shunt regulated current fed supply circuit, and each channel has its own. The current sources consists of a few FETs and a bipolar and give me 100 MOhm. The shunt is a E182CC (using a OB2 as its reference). Each channel of this is directly powering an EC86 (no electrolytic!), and from there via a RC (C is PIO again) to the input tube. Because of an additional trick in the shunt circuitry the PSRR is in the order of 130 dB in the audio band, and it will not dip under 100 dB up to many hundreds of kHz. Wiring is point to point, of course. Silver wire is used throughout, except for the filament supplies (though some claim that it sounds better there too). Housing is made of copper, as this tends to sound better than aluminum or RVS. In my opninion it is better to avoid plain steel. http://www.rintelen.ch/hifi/lil_sis.pdf Lil Sis |
#8
Posted to rec.audio.tubes
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PHONE PREAMP
Another very good option is the Hagerman preamp, found at hagtech.com His
schematics and manual are on line so you can build for free or buy his board or kit. I found that the Hagerman budget priced preamps and phono stages are very good as a starter set. You can upgrade pwr supply and components at will to improve. With respect to phono pre's I like the passive approach better than the feedback driven one--although it requires (usually) an extra stage of amplification. YMMV "ec" wrote in message ... Hi where can i find quality tube phono preamp schematics? Thanks ec |
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