awty Posted February 23, 2016 Posted February 23, 2016 (edited) Hi felix at least you have some sort of concept of how it all works, im still not convinced it's not the work of sorcery, elves and goblins. Ortofun mine is a hybrid, all valve through the signal stage but the power has external transformer with a step up transformer on board and IC's and stuff. Makes it dead quiet even with horns, but the trick is, I believe to make them tube through out...one day. Ha! had to shove a wooden plug up one of the legs of the phono, cause my modulating tripod stand some how ended out of level by 20mm, at least the TT and tonearm came out level. Edited February 23, 2016 by awty
RoHo Posted February 23, 2016 Posted February 23, 2016 My DIY pre-amp includes a phono stage. It is the "FVP5A" designed by Allen Wright. It can be configured as either MM or MC by changing a few resistors, mine is MM. The input stage is hybrid: a valve above a FET in "cascode" arrangement. I got lazy and used basic AC heating on the valves throughout. There is a little hum but it isn't intrusive at the listening position. I could post a photo but really all there is to see is a case from vt4c.com in Hong Kong with a few transformers and chokes on top and some valves sticking out.
Guest Muon Posted February 23, 2016 Posted February 23, 2016 G'day all, frankly I'm very jealous of the fine examples of general construction/metalwork/boxing seen in this thread, as I am perfectly hopeless in that respect. This (unfortunately) explains my tendency to build things 'unboxed'. If only I was better at my metal working skills! Regards, Felix. Felix, you can utilise old boxes from CD players, set top boxes, just about any electronics case that is of no use anymore that you might find suitable for the job
Guest Muon Posted February 23, 2016 Posted February 23, 2016 Hi felix at least you have some sort of concept of how it all works, im still not convinced it's not the work of sorcery, elves and goblins. Ortofun mine is a hybrid, all valve through the signal stage but the power has external transformer with a step up transformer on board and IC's and stuff. Makes it dead quiet even with horns, but the trick is, I believe to make them tube through out...one day. Ha! had to shove a wooden plug up one of the legs of the phono, cause my modulating tripod stand some how ended out of level by 20mm, at least the TT and tonearm came out level. You mean step up for the HT rails and stuff? Or are you talking about SUTs for MC/
awty Posted February 23, 2016 Posted February 23, 2016 You mean step up for the HT rails and stuff? / Yes. This is the designers blurb. " Our design also includes linear, regulated high-voltage and heater supplies for low noise and low operating drift. The 200 volt supply rail operates the tubes in their intended range - we don’t starve the tubes by operating them at low voltages. And, we completely avoid the use of switching power supplies. The unit is powered from an external AC wall transformer, using a small internal step-up transformer for the high voltage supply. This puts the larger, high-current transformer outside (and well away from) the enclosure. A sophisticated circuit board design with multiple ground domains eliminates coupled noise. Finally, we use a low-noise 5751 input tube (you can substitute a 12AX7 if you prefer). The result of all this is exceptionally low noise and hum for a tube phono stage, in a compact and low-cost package."
Guest Muon Posted February 23, 2016 Posted February 23, 2016 Yes. This is the designers blurb. " Our design also includes linear, regulated high-voltage and heater supplies for low noise and low operating drift. The 200 volt supply rail operates the tubes in their intended range - we don’t starve the tubes by operating them at low voltages. And, we completely avoid the use of switching power supplies. The unit is powered from an external AC wall transformer, using a small internal step-up transformer for the high voltage supply. This puts the larger, high-current transformer outside (and well away from) the enclosure. A sophisticated circuit board design with multiple ground domains eliminates coupled noise. Finally, we use a low-noise 5751 input tube (you can substitute a 12AX7 if you prefer). The result of all this is exceptionally low noise and hum for a tube phono stage, in a compact and low-cost package." Cool If I remember correctly TL in one of the changes to the EAR circuit he increased one of the valves plate voltages as he considered it as being starved too much, been a while since I looked at the individual changes in his design.
mwhouston Posted February 23, 2016 Posted February 23, 2016 G'day all, frankly I'm very jealous of the fine examples of general construction/metalwork/boxing seen in this thread, as I am perfectly hopeless in that respect. This (unfortunately) explains my tendency to build things 'unboxed'. If only I was better at my metal working skills! Regards, Felix. Have a go, it isn't hard.
mwhouston Posted February 23, 2016 Posted February 23, 2016 (edited) G'day all, frankly I'm very jealous of the fine examples of general construction/metalwork/boxing seen in this thread, as I am perfectly hopeless in that respect. This (unfortunately) explains my tendency to build things 'unboxed'. If only I was better at my metal working skills! Regards, Felix.I would say I have built about two dozen phono stages and all I enclosures. Edited February 23, 2016 by mwhouston
andyr Posted February 23, 2016 Posted February 23, 2016 (edited) G'day all, frankly I'm very jealous of the fine examples of general construction/metalwork/boxing seen in this thread, as I am perfectly hopeless in that respect. This (unfortunately) explains my tendency to build things 'unboxed'. If only I was better at my metal working skills! Regards, Felix. G'day all, frankly I'm very jealous of the fine examples of general construction/metalwork/boxing seen in this thread, as I am perfectly hopeless in that respect. This (unfortunately) explains my tendency to build things 'unboxed'. If only I was better at my metal working skills! Regards, Felix. Mmmm, in my world, Felix, you don't build the cases - you buy them. I use the excellent cases provided by Modushop.biz, in Italy. I've probably bought ... 25 or so cases from them over the last 3 or 4 years. Andy Edited February 23, 2016 by andyr
Guest Muon Posted February 23, 2016 Posted February 23, 2016 I couldn't build a metal case that wound be great, so I don't try.........so if i do it will be bought, there aren't many that actually build their won cases in the DIY world, Felix.
skies2clear Posted February 29, 2016 Posted February 29, 2016 Cool If I remember correctly TL in one of the changes to the EAR circuit he increased one of the valves plate voltages as he considered it as being starved too much, been a while since I looked at the individual changes in his design. That could be right if it's based on the 834P circuit. The first stage is a bit low in plate V for a 12AX7 to hit its straps.
Guest Muon Posted February 29, 2016 Posted February 29, 2016 That could be right if it's based on the 834P circuit. The first stage is a bit low in plate V for a 12AX7 to hit its straps. Apparently one of the things that gave it the sound it had, but I'm going on memory here....so i could be wrong.
sansui111 Posted April 9, 2016 Posted April 9, 2016 G'day all, just a general enquiry, how many use a DIY phono stage, either for MM or MC cartridges (or both). Regards, Felix. i am building one right now, 4 fets and a 12ay7 for the final output
sansui111 Posted April 9, 2016 Posted April 9, 2016 my valve phono i am building 2 fets per side. and a 12ay7 for the buffer amp with regulated EHT and regulated 12.6 volts for the heaters and the fets. zero 100 Hz hum, adding a cartridge loading switch sounds damn good few more tweaks the RIAA curve and behaviour compared to a premade one is spot on 1
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