so what to do next ?
i plan to build the Salas shunts now. the powersupply i am now using is the LC Audio Low noise supply in double mono. seperate supplies for the input and outputstage. i have the input and outputstage in seperate boxes. i will ad the circiut diagramm of the LC regulator in the attatchement.
second i plan to do a High Z FET version and then i whould like to try the inductive RIAA.
By the way i have already specified the 25mH inductors. they will be wound in OFC copper by a german specialist on a low distortion closed ferite bobin. i plan to sell them in matched pairs with 1% tolerance measured on a Wane Kerr bridge and Brühl + Kjaer quality control. they will not be dirt cheap but i plan to sell them for 50,-€ a pair plus shipping. this does not cover my expenses because matchig ferrite coils is not easy. to wind the same number of turns is not enough because the permeabiity of the ferite bobbins strays a bit. low level resolution of that coils is excellent because there is no Barkhausen effect and magnetising probems at low volume in that ferrrite that happens in iron cores and gives the boundary of resolution. look at the latest Audio issue of Elektor for an extensive explanation of that effect.
i plan to build the Salas shunts now. the powersupply i am now using is the LC Audio Low noise supply in double mono. seperate supplies for the input and outputstage. i have the input and outputstage in seperate boxes. i will ad the circiut diagramm of the LC regulator in the attatchement.
second i plan to do a High Z FET version and then i whould like to try the inductive RIAA.
By the way i have already specified the 25mH inductors. they will be wound in OFC copper by a german specialist on a low distortion closed ferite bobin. i plan to sell them in matched pairs with 1% tolerance measured on a Wane Kerr bridge and Brühl + Kjaer quality control. they will not be dirt cheap but i plan to sell them for 50,-€ a pair plus shipping. this does not cover my expenses because matchig ferrite coils is not easy. to wind the same number of turns is not enough because the permeabiity of the ferite bobbins strays a bit. low level resolution of that coils is excellent because there is no Barkhausen effect and magnetising probems at low volume in that ferrrite that happens in iron cores and gives the boundary of resolution. look at the latest Audio issue of Elektor for an extensive explanation of that effect.
today i did more carefully controlled listening sessions with the MPP and installed a Clearaudio Accurate in another turntable that was sitting for over 10 years in storage.
it has a very challenging combination of 60 Ohm coil impedance and 0.6mV output. it worked and i will tell you how that sessions went in my next thread. i put now more thinking into the Salas power supply and did some primitive simulation of the pre regulator (circuit shown) with a "misused" AJ Horn, a program for loudspeakers. look only at the SPL curve. with 2 x 10.000 uF and my 25mH 6 Ohm ferrite coil regulation is better then -35dB at 50Hz assuming that the Salas regulator draws 350mA. i will do the pre regulation double mono in an external box.
it has a very challenging combination of 60 Ohm coil impedance and 0.6mV output. it worked and i will tell you how that sessions went in my next thread. i put now more thinking into the Salas power supply and did some primitive simulation of the pre regulator (circuit shown) with a "misused" AJ Horn, a program for loudspeakers. look only at the SPL curve. with 2 x 10.000 uF and my 25mH 6 Ohm ferrite coil regulation is better then -35dB at 50Hz assuming that the Salas regulator draws 350mA. i will do the pre regulation double mono in an external box.
listening session
i have now listened enough to the MPP low Z version to know it´s sound quite well. first i listened to my usual reference turntable, the Spiral Groove SG 1 with Wheaton Triplanar Ultimate 7 and Lyra Titan i. at first i thought that there was a very mild loss in the stratospheric treble giving a bit less edje definition
that i am used too. i changed the phonocable from an old Wireworld Eclipse to a Wirewold Silver Eclipse 5.2 and everything snapped into focus. that silver clad ohno cast copper cable gave that extra definition i was looking for. so alone from that experiment i can draw some conclusion or better construct a mind experiment. does my usual phonostage need some taming in the treble and does the MPP simply show that the newer and more sofisticated Silver Eclipse is a superiour product ? be it as it may, the MPP has less spittiness and dsitortion in the treble then most and with the right mix of components the sound is superbly extended and balanced. was is also quite special is the way it handles the midrange. even in a very dense mix like electrible 101s first album vokals stand out crystal clear and the same time very smooth and fleshed out in tone. if you are used to a lesser phonostage that feature will give the music a quite shocking fresh and logical meaning. tonal balnce is now very close to my reference Goldstandart with Telepath. i was curious how another cartridge would sound so i mounted an over 10 year old and never played Clearaudio Accurate in my small Goldring turntable that is basically a Rega with MDF platter and RB100 arm. it costs less then 400,-€ in Germany, no match to the 33.000,-€ main turntable that sits on a quite eleborate stand from layers of steel, rubber, granite, wood and sorbothane. i made some modifications to it but nothing spectacular. i use a white swiss felt mat from the Reuther brothers and a aluminum weight from transrotor. i put it on an old Roxan stand, took of the plastic lid and put a heavy steel weight on the soundboard of the turntable. the Clearaudio is not easy to connect because the wires from the Rega where to short. i build some jumper cables from a headshell of a 30year old DUAL turntable so this is nothing fancy. how did that sound. well if a cartridge can bring the Low Z version of the MPP in trouble, this is it. i had to crank the volume really high. because of the transimpedance action of the input stage voltage amplification whent down a lot. for example the volume display of my MACE preamp showed "80" where it had been "40" with the Titan for the same subjective volume. i have not mesured it in the lab but that is a lot. hiss was still not audible in the listening chair but there was a very faint hum. this a function of the very primitive armwiring that has no seperate earth wire, something i never understood in the cheap REGA arms. well this cable INCLUDING the flimsy nickel plated jacks will cost only 50cents but it is just too compromised for my taste and 5 Euro more could buy something decent. but who am i to critisize the wise men at REGA? so how was the sound? frankly i expected some icecool wind in the treble because Clearaudios from that vintage are somewhat famous for extended and rising treble. not the case this time!
the sound was sweet as a lollypop and smooth as butter. well i know that you can download the Clearaudios much and i think 50-60 Ohms was recommended at that time to "avoid reflexions". what people often do not understand is that a transimpedance stage is not dumping the energy into a resistor like higher impedance stages do but make use of all the availlable energy in the form of lower voltage and higher current. so U x I is constant.
did the sound be overdamped ? i do not think so. after removing the lid and damping the soundboard the sound was spacious and free from the speakers. ok, in terms off edje definition, resolution and speed is was no match to my reference table but i do not think that was a major flaw of the Cearaudio-MPP combination. i know the sound of the REGA very well with my Helikon that is the smaller brother of the Titan and i heard the same substractive colourations i know so well. anyway, whould i had put a blanket over the table i could easyly fool most of you into thinking that quite an expensive frontend is playing. was it a totall success ? i do not think so and i really whould like to try the Clearaudion on a high Z version of the MPP with FETs.
i have now listened enough to the MPP low Z version to know it´s sound quite well. first i listened to my usual reference turntable, the Spiral Groove SG 1 with Wheaton Triplanar Ultimate 7 and Lyra Titan i. at first i thought that there was a very mild loss in the stratospheric treble giving a bit less edje definition
that i am used too. i changed the phonocable from an old Wireworld Eclipse to a Wirewold Silver Eclipse 5.2 and everything snapped into focus. that silver clad ohno cast copper cable gave that extra definition i was looking for. so alone from that experiment i can draw some conclusion or better construct a mind experiment. does my usual phonostage need some taming in the treble and does the MPP simply show that the newer and more sofisticated Silver Eclipse is a superiour product ? be it as it may, the MPP has less spittiness and dsitortion in the treble then most and with the right mix of components the sound is superbly extended and balanced. was is also quite special is the way it handles the midrange. even in a very dense mix like electrible 101s first album vokals stand out crystal clear and the same time very smooth and fleshed out in tone. if you are used to a lesser phonostage that feature will give the music a quite shocking fresh and logical meaning. tonal balnce is now very close to my reference Goldstandart with Telepath. i was curious how another cartridge would sound so i mounted an over 10 year old and never played Clearaudio Accurate in my small Goldring turntable that is basically a Rega with MDF platter and RB100 arm. it costs less then 400,-€ in Germany, no match to the 33.000,-€ main turntable that sits on a quite eleborate stand from layers of steel, rubber, granite, wood and sorbothane. i made some modifications to it but nothing spectacular. i use a white swiss felt mat from the Reuther brothers and a aluminum weight from transrotor. i put it on an old Roxan stand, took of the plastic lid and put a heavy steel weight on the soundboard of the turntable. the Clearaudio is not easy to connect because the wires from the Rega where to short. i build some jumper cables from a headshell of a 30year old DUAL turntable so this is nothing fancy. how did that sound. well if a cartridge can bring the Low Z version of the MPP in trouble, this is it. i had to crank the volume really high. because of the transimpedance action of the input stage voltage amplification whent down a lot. for example the volume display of my MACE preamp showed "80" where it had been "40" with the Titan for the same subjective volume. i have not mesured it in the lab but that is a lot. hiss was still not audible in the listening chair but there was a very faint hum. this a function of the very primitive armwiring that has no seperate earth wire, something i never understood in the cheap REGA arms. well this cable INCLUDING the flimsy nickel plated jacks will cost only 50cents but it is just too compromised for my taste and 5 Euro more could buy something decent. but who am i to critisize the wise men at REGA? so how was the sound? frankly i expected some icecool wind in the treble because Clearaudios from that vintage are somewhat famous for extended and rising treble. not the case this time!
the sound was sweet as a lollypop and smooth as butter. well i know that you can download the Clearaudios much and i think 50-60 Ohms was recommended at that time to "avoid reflexions". what people often do not understand is that a transimpedance stage is not dumping the energy into a resistor like higher impedance stages do but make use of all the availlable energy in the form of lower voltage and higher current. so U x I is constant.
did the sound be overdamped ? i do not think so. after removing the lid and damping the soundboard the sound was spacious and free from the speakers. ok, in terms off edje definition, resolution and speed is was no match to my reference table but i do not think that was a major flaw of the Cearaudio-MPP combination. i know the sound of the REGA very well with my Helikon that is the smaller brother of the Titan and i heard the same substractive colourations i know so well. anyway, whould i had put a blanket over the table i could easyly fool most of you into thinking that quite an expensive frontend is playing. was it a totall success ? i do not think so and i really whould like to try the Clearaudion on a high Z version of the MPP with FETs.
this is true but in this case it worked perfectly well. with my opamp based phonos i usually prefer pure copper but mix in some silver here and there. i also do not know why the used material is audible. what we found out is that me and my assosiates like litzwire construction so it may have to do with skin effect. i could also theorytise that between the differing metals a voltage could develop that creates some noise. well to be honest i gave up to find a scientific explanation. cable wise i am in a good situation because i get free samples from Wire World, Spiral Groove, Nordost, Sommercable and other. i have litarally hundreds of cables and some are found to work relyably for me.
i am working full steam on a high Z version of the MPP with Fet input. it will have an inductive RIAA that has many advantages. i will explain more later. the first version of the inductive RIAA had a mathematical error so it is obsolete now. the new version has all the features that i have learned to be good so far. Dc offset and distortion can be trimmed for minimum now independently.
Hmm, looks certainly very nice, pretty similar topology as in the Vendetta input stage except for the BJT cascode transistors. Is there no way to create a JFET transimpedance input stage, similar to your BJT version? Just an idea, but if you closely match N- and P-Channel current there should be very little offset voltage when running the input stage in common-gate mode?
You would not want the 6R series impedance of that choke on the B+ after employing a very low impedance regulator that you plan of, I would think. It defies the purpose IMHO.
After it being prefiltered with chokes for incoming gremlins and then regulated, if the Output Z of the reg is say in the 5mOhm area and flat up to several decades of kHz, just a 0.01uF COG/NPO (better it be SMT) or other good enough types with short legs and sizes that you can actually see for that matter (N.Pass TM speak), is all you need for locally decoupling the power receiving ends. A large electrolytic even if alone there, as the one you have now in LC configuration is going to interact and worsen the very high frequency Z of a remotely sensed shunt regulated B+/- voltage source.
It will be insignificant interaction between stages over a preserved very low and flat Z reg impedance even if its common between stages. Simply because there will be no Z to speak of for the different current demands to dance on.
Of course you could plan more regs for stage separation, maybe there will be other benefits in that, but you can safely run the whole thing initially on a common +/- shunt, given that your receiving ends and grounds are going to be arranged in short & symmetrical star fashion, for the sense wires to transfer meaningful interaction at the reg's error loop nodes.
After it being prefiltered with chokes for incoming gremlins and then regulated, if the Output Z of the reg is say in the 5mOhm area and flat up to several decades of kHz, just a 0.01uF COG/NPO (better it be SMT) or other good enough types with short legs and sizes that you can actually see for that matter (N.Pass TM speak), is all you need for locally decoupling the power receiving ends. A large electrolytic even if alone there, as the one you have now in LC configuration is going to interact and worsen the very high frequency Z of a remotely sensed shunt regulated B+/- voltage source.
It will be insignificant interaction between stages over a preserved very low and flat Z reg impedance even if its common between stages. Simply because there will be no Z to speak of for the different current demands to dance on.
Of course you could plan more regs for stage separation, maybe there will be other benefits in that, but you can safely run the whole thing initially on a common +/- shunt, given that your receiving ends and grounds are going to be arranged in short & symmetrical star fashion, for the sense wires to transfer meaningful interaction at the reg's error loop nodes.
I would decouple them with the COG/NPO initially. If there is a benefit for specific op amps to get something more substantial there, surely would not be too big or slow, and it would be chosen upon trial.
EDIT: Scott's AD797 has some recommendations to check out on its datasheet, for instance. Its a most capable op amp that I would not leave out of my subjective comparisons in such a phono BTW.
