Hi,
THOMAS MAYER
For a long time I've been tinkering with this type of RIAA correction for a tube preamp.
Since the LCR modules are again available I am looking for some input from others on how to best implement this.
More precisely, how to do this without using any stepdown xformers if possible.
Cheers,
THOMAS MAYER
For a long time I've been tinkering with this type of RIAA correction for a tube preamp.
Since the LCR modules are again available I am looking for some input from others on how to best implement this.
More precisely, how to do this without using any stepdown xformers if possible.
Cheers,
LCR RIAA web links
Frank,
Any reason you want to stay away from transformers? They're not that expensive and can sound pretty good. I think a tube loaded with a lundahl 1660 could drive the LCR network pretty well.
Here are a few links to get people started:
http://digilander.libero.it/paeng/inductive_riaa.htm
http://www.rintelen.ch/pdf/Preamp.pdf
http://www.vt52.com/diy/myprojects/amps/exopre/exopre.htm
There was also a japanese web page where the gentleman used a 6922 SRPP to drive the LCR without transformer, but I can't find the link right now.
---Gary
Frank,
Any reason you want to stay away from transformers? They're not that expensive and can sound pretty good. I think a tube loaded with a lundahl 1660 could drive the LCR network pretty well.
Here are a few links to get people started:
http://digilander.libero.it/paeng/inductive_riaa.htm
http://www.rintelen.ch/pdf/Preamp.pdf
http://www.vt52.com/diy/myprojects/amps/exopre/exopre.htm
There was also a japanese web page where the gentleman used a 6922 SRPP to drive the LCR without transformer, but I can't find the link right now.
---Gary
Hi,
Mainly because I don't want to take the "easy" way out...
Nothing is ever perfect of course but I feel I have a better chance of maintaining large bandwidth by using tubes.
There is also the possibility of a fully balanced preamp, you may of course say that this is easier to achieve by using xformers.
You're absolutely correct but I would love to try that with tubes as well.
If it turns out to be a delusion, than so be it.
Cheers,
Mainly because I don't want to take the "easy" way out...
Nothing is ever perfect of course but I feel I have a better chance of maintaining large bandwidth by using tubes.
There is also the possibility of a fully balanced preamp, you may of course say that this is easier to achieve by using xformers.
You're absolutely correct but I would love to try that with tubes as well.
If it turns out to be a delusion, than so be it.
Cheers,
Hi,
I have been really struggeling on this myself. I am not per se against using transformers, but with most "normal" valves (eg. 6S45-PE) you end up wedging the RIAA between two Transformers, the stepdown one probably having to be used in parallel feed as well.
This means two transformers add their rolloff, which even with something like a pair of Stevens & Billington TX-103 per channel for matching the RIAA (and yes, I did consider that and even tried something similar clipleaded with an RC RIAA just to ***** the impact of the Transformers) means you have over 2db more loss at 10Hz (and less consequentially but audible) 100KHz than without the transformers.
As few transformers offer relaibly such wide bandwidth at the required levels (such transformers also cost less of course) things may be even worse. I like transformers but not just for their own sake.
One option that frees you totally from the question how to drive a low impedance LCR RIAA EQ is to make a high impedance one. Yet given the problems of making the relative low value inductors for the 600 Ohm Impedance RIAA I suspect a 10k LCR RIAA may prove very difficult to make reliably.
Secondly, you could of course simply use any old Valve stage with suitable gain, take a small value coupling cap and use a solid state unity gain buffer to drive the pubishing (for valves and even most Op-Amp's) 600R Load of the RIAA, but of course, that is "cheating" (I'd say inspired and competent engineering, but I know it's cheating in the end.
I ended up persuing a very different Tack. Using suitably high Gm Pentodes (E810F - 50mA/V) you get plenty of gain even into a 600 Ohm load and even better, as the Output impedance of the Pentode Valve stage is very high you can at least partially compensate the use of a much smaller value than conventionally required coupling capacitor. I have tried as small values as 2.2uF in my circuit.
The circuit I'm talking of is of course this one:
Phonostage Circuit
Total gain of this Phonostage with a S&B TX-103 wired for 26db stepup is over 66db, output impedance is under 2k, just fine for a TVC with 6db stepup, which in total gives 72db gain.
With a typhical 0.25mV MC pickup this gives around 1V RMS out with around 14db headroom on top of this (the Max. Headroom on LP is around 14db above the reference 5cm/S at 300Hz), or up to 5V RMS on the highest peaks. Just right to feed an Ultracurve Digital EQ or low gain DHT Amplifiers.... ;-)
Assembled the whole thing with S&B TX-103 MC Stepups and Prototypes of the S&B RIAA-600 EQ Modules looks like this:
Phonostage piccie
Using the same basic principle of driving the RIAA from a very high source impedance I could think of using three or four paralleled 2SK170 J-Fets in Cascode with a valve (say a 6N30?) to give 60 - 80/V into the 600R RIAA. This will give a gain of the first stage of around 36 or 48 aka 31 and 33db respectively. The output could then be the other halve of the 6N30 again, very low impedance to drive a TCV or the like well. Overall gain of such a circuit without MC Stepup could be around 33 to 35db due to the low gain of the second valve.
Of course, if you liked you could use another 3 - 4 2SK170 Cascode in the second stage with 600 Ohm anode load for low output impedance. Then you have a total gain of 42 - 46db without MC Stepup and up to 72db with a TX103....
Maybe all this gives you some ideas?
Sayonara
I have been really struggeling on this myself. I am not per se against using transformers, but with most "normal" valves (eg. 6S45-PE) you end up wedging the RIAA between two Transformers, the stepdown one probably having to be used in parallel feed as well.
This means two transformers add their rolloff, which even with something like a pair of Stevens & Billington TX-103 per channel for matching the RIAA (and yes, I did consider that and even tried something similar clipleaded with an RC RIAA just to ***** the impact of the Transformers) means you have over 2db more loss at 10Hz (and less consequentially but audible) 100KHz than without the transformers.
As few transformers offer relaibly such wide bandwidth at the required levels (such transformers also cost less of course) things may be even worse. I like transformers but not just for their own sake.
One option that frees you totally from the question how to drive a low impedance LCR RIAA EQ is to make a high impedance one. Yet given the problems of making the relative low value inductors for the 600 Ohm Impedance RIAA I suspect a 10k LCR RIAA may prove very difficult to make reliably.
Secondly, you could of course simply use any old Valve stage with suitable gain, take a small value coupling cap and use a solid state unity gain buffer to drive the pubishing (for valves and even most Op-Amp's) 600R Load of the RIAA, but of course, that is "cheating" (I'd say inspired and competent engineering, but I know it's cheating in the end.
I ended up persuing a very different Tack. Using suitably high Gm Pentodes (E810F - 50mA/V) you get plenty of gain even into a 600 Ohm load and even better, as the Output impedance of the Pentode Valve stage is very high you can at least partially compensate the use of a much smaller value than conventionally required coupling capacitor. I have tried as small values as 2.2uF in my circuit.
The circuit I'm talking of is of course this one:
Phonostage Circuit
An externally hosted image should be here but it was not working when we last tested it.
Total gain of this Phonostage with a S&B TX-103 wired for 26db stepup is over 66db, output impedance is under 2k, just fine for a TVC with 6db stepup, which in total gives 72db gain.
With a typhical 0.25mV MC pickup this gives around 1V RMS out with around 14db headroom on top of this (the Max. Headroom on LP is around 14db above the reference 5cm/S at 300Hz), or up to 5V RMS on the highest peaks. Just right to feed an Ultracurve Digital EQ or low gain DHT Amplifiers.... ;-)
Assembled the whole thing with S&B TX-103 MC Stepups and Prototypes of the S&B RIAA-600 EQ Modules looks like this:
Phonostage piccie
An externally hosted image should be here but it was not working when we last tested it.
Using the same basic principle of driving the RIAA from a very high source impedance I could think of using three or four paralleled 2SK170 J-Fets in Cascode with a valve (say a 6N30?) to give 60 - 80/V into the 600R RIAA. This will give a gain of the first stage of around 36 or 48 aka 31 and 33db respectively. The output could then be the other halve of the 6N30 again, very low impedance to drive a TCV or the like well. Overall gain of such a circuit without MC Stepup could be around 33 to 35db due to the low gain of the second valve.
Of course, if you liked you could use another 3 - 4 2SK170 Cascode in the second stage with 600 Ohm anode load for low output impedance. Then you have a total gain of 42 - 46db without MC Stepup and up to 72db with a TX103....
Maybe all this gives you some ideas?
Sayonara
MISSING LINK.
Hi,
Gary B.,
Would this be link you're missing?
SHISHIDO
All,
EC8010 raised an interesting question regarding the input impedance of the RIAA network.
From the previous designs I've seen it was always stated as being 600 Ohm.
Is this information correct ? If so, shouldn't it than be drive form an even lower source impedance?
Cheers,
Hi,
Gary B.,
Would this be link you're missing?
SHISHIDO
All,
EC8010 raised an interesting question regarding the input impedance of the RIAA network.
From the previous designs I've seen it was always stated as being 600 Ohm.
Is this information correct ? If so, shouldn't it than be drive form an even lower source impedance?
Cheers,
Re: MISSING LINK.
Hi,
Actually, there are plenty more. My HDD holds over a dozend RLC or RL equalised Phonostages....
To save me excessive typing I shall quote here from the Application note posted here:
S&B EQ-600 RIAA Module Application Notes
"The EQ-600 is designed to operate in a 600 Ohm matched impedance system, as provided in many broadcast and similar applications. Either the load provided to the RIAA Module must be 600 Ohm in which case the drive impedance is immaterial and the RIAA Module presents the driving circuit with a frequency independent 600 Ohm Load (+/-5% or closer tolerance) OR the impedance of the source (drive impedance) must be very accurately 600 Ohm in which case the load impedance is immaterial."
"The specifics of the amplification stages are really up to the designer using the RIAA Module, the degree of freedom in choice of topology, active device and so on is huge and even a most scant coverage would require a long article. The RIAA circuit will in any case of application cause around 20db attenuation at 1KHz. Possibilities include Operational Amplifiers set to give 30db gain, Mu-Follower stages using a 6SL7 or similar valves for the gain parts and suitable follower devices and many other Valve, hybrid, discrete solid state or monolithic integrated solutions. As a rule the output of the first amplification stage should either be of a matched impedance of 600 Ohm or of low source impedance and able to drive a 600 Ohm load to significant level."
"Typically, to maximise overload margins and such one would have for a typical "moving magnet" type phono stage Amplification stages with around equal gain of around 30db each and suitable output impedance's. In such a case a phono stage using the RIAA Module would have a total gain of around 40db allowing an IEC sensitivity of 5mV for Phono."
"If a TX103 is added ahead of the phono stage to match MC Cartridges the IEC sensitivity becomes 1mV, 0.5mV and 0.25mV respectively for the 1:5, 1:10 and 1:20 step-up ratio. If a TX-102 based passive controller is used following the phono stage and if the output stage gainblock offers a compatible output impedance the TX-102 can be connected in 6db "passive gain" mode, giving IEC sensitivities of 0.5mV, 0.25mV and 0.12mV for the complete phono stage."
"Other gain schemes are possible but will result in reduced overload margins."
I hope this clarifies.
Sayonara
PS, driving a 600 Ohm load from an infinite source impedance is no issue, the load simply is driven in pure current mode. Equally a Pentode has no problems at all to lineary drive a dead short at all (the same cannot be said of triodes though).
Hi,
Actually, there are plenty more. My HDD holds over a dozend RLC or RL equalised Phonostages....
To save me excessive typing I shall quote here from the Application note posted here:
S&B EQ-600 RIAA Module Application Notes
"The EQ-600 is designed to operate in a 600 Ohm matched impedance system, as provided in many broadcast and similar applications. Either the load provided to the RIAA Module must be 600 Ohm in which case the drive impedance is immaterial and the RIAA Module presents the driving circuit with a frequency independent 600 Ohm Load (+/-5% or closer tolerance) OR the impedance of the source (drive impedance) must be very accurately 600 Ohm in which case the load impedance is immaterial."
"The specifics of the amplification stages are really up to the designer using the RIAA Module, the degree of freedom in choice of topology, active device and so on is huge and even a most scant coverage would require a long article. The RIAA circuit will in any case of application cause around 20db attenuation at 1KHz. Possibilities include Operational Amplifiers set to give 30db gain, Mu-Follower stages using a 6SL7 or similar valves for the gain parts and suitable follower devices and many other Valve, hybrid, discrete solid state or monolithic integrated solutions. As a rule the output of the first amplification stage should either be of a matched impedance of 600 Ohm or of low source impedance and able to drive a 600 Ohm load to significant level."
"Typically, to maximise overload margins and such one would have for a typical "moving magnet" type phono stage Amplification stages with around equal gain of around 30db each and suitable output impedance's. In such a case a phono stage using the RIAA Module would have a total gain of around 40db allowing an IEC sensitivity of 5mV for Phono."
"If a TX103 is added ahead of the phono stage to match MC Cartridges the IEC sensitivity becomes 1mV, 0.5mV and 0.25mV respectively for the 1:5, 1:10 and 1:20 step-up ratio. If a TX-102 based passive controller is used following the phono stage and if the output stage gainblock offers a compatible output impedance the TX-102 can be connected in 6db "passive gain" mode, giving IEC sensitivities of 0.5mV, 0.25mV and 0.12mV for the complete phono stage."
"Other gain schemes are possible but will result in reduced overload margins."
I hope this clarifies.
Sayonara
PS, driving a 600 Ohm load from an infinite source impedance is no issue, the load simply is driven in pure current mode. Equally a Pentode has no problems at all to lineary drive a dead short at all (the same cannot be said of triodes though).
Re: Re: MISSING LINK.
Hi,
On second thought, I always believed the best way to enrich oneself is to freely give away what one has, so I have uploaded/am uploading a library of LR/LCR equalised Phonostages for the general entertainment of the distingue audience....
All schematics are deposited here:
LR/LRC RIAA EQ Schematics
Note that some schematics (especially those from the Sakuma inspired school) do not offer an overly accurate RIAA Response. How relevant this is everyone must decide for themselves.
Sayonara
Hi,
On second thought, I always believed the best way to enrich oneself is to freely give away what one has, so I have uploaded/am uploading a library of LR/LCR equalised Phonostages for the general entertainment of the distingue audience....
All schematics are deposited here:
LR/LRC RIAA EQ Schematics
Note that some schematics (especially those from the Sakuma inspired school) do not offer an overly accurate RIAA Response. How relevant this is everyone must decide for themselves.
Sayonara
Frank, would you entertain a naive question from me? Since it's extremely easy to design a tube RIAA stage with arbitrarily low deviations from the standard, low noise and distortion, low source Z, and stable into the loads typical of cables and preamps (or 600 ohm lines, if it's for studio rather than home use), what's the point of using LCR circuits and transformers? What design advantages does one get for the expense and complication?
LCR.
Hi SY,
Sure.
From what I've read and tried to understand of it, this type of correction has the advantage of being impervious to ageing of the tubes.(Changes in operating parameters)
Another advantage is that you work into low impedances forcing current drive of the next stage.
Transformers have the added advantage of providing galvanic ( is that the correct Enlgish word?) isolation between groundplanes, so there is no interaction between them.
Personnally I do not use any, other people swear by them.
This is quite likely not the complete answer, so those who have actually built this kind of circuit may be better placed to answer any further questions.
Cheers,
Hi SY,
Sure.
From what I've read and tried to understand of it, this type of correction has the advantage of being impervious to ageing of the tubes.(Changes in operating parameters)
Another advantage is that you work into low impedances forcing current drive of the next stage.
Transformers have the added advantage of providing galvanic ( is that the correct Enlgish word?) isolation between groundplanes, so there is no interaction between them.
Personnally I do not use any, other people swear by them.
This is quite likely not the complete answer, so those who have actually built this kind of circuit may be better placed to answer any further questions.
Cheers,
Thanks, Mr d. "Galvanic" is indeed the correct English word, though the "advantage" of galvanic isolation in this application escapes me. And it's pretty easy to make an RIAA amp that doesn't change response significantly with normal tube aging. It's also unclear to me why forcing a stage to "current drive" is any kind of performance advantage. Someone will fill me in, I'm sure.
Hi,
All I can suggest is that if you are looking for a specific argument that can be quantified by conventional meaningless measurements (especially THD, Frequency response etc.) you will never "get it".
As a cute little aside, most of the cutting Amplifiers (certainly Westrex and earlier Neumanns) used LCR based EQ's to define the cutting curve. Now even the best inductors do not behave absolutely linear with level and frequency. And of course, if the cutting amplifier is green the playback amplifier needs a red front plate.
Anyway, to seek for the "sound" of a given thing (be it LCR Equalisers, Transformer coupling etc.) in simple, onedimensional steady state measurements is just like that old martian friend of mine I often quote....
Sayonara
"Ever heard the story of the Martian who visited Earth and was intreagued by the amount of attention these funny human paid to something called Music?
So he spend loads of time investigating. He recorded the Scores. He measured the physical properties of Instruments. He measured the size and shape of the Concert halls. And so on. This martian actually spend almost 20 Years in that. Then he returned with all his collected results to Mars, stepped in front of all his people, held up his collected Data and thought to them "Here I bring you MUSIC". You know of course that Martians communicate via telepathy and have no sense of hearing...."
All I can suggest is that if you are looking for a specific argument that can be quantified by conventional meaningless measurements (especially THD, Frequency response etc.) you will never "get it".
As a cute little aside, most of the cutting Amplifiers (certainly Westrex and earlier Neumanns) used LCR based EQ's to define the cutting curve. Now even the best inductors do not behave absolutely linear with level and frequency. And of course, if the cutting amplifier is green the playback amplifier needs a red front plate.
Anyway, to seek for the "sound" of a given thing (be it LCR Equalisers, Transformer coupling etc.) in simple, onedimensional steady state measurements is just like that old martian friend of mine I often quote....
Sayonara
"Ever heard the story of the Martian who visited Earth and was intreagued by the amount of attention these funny human paid to something called Music?
So he spend loads of time investigating. He recorded the Scores. He measured the physical properties of Instruments. He measured the size and shape of the Concert halls. And so on. This martian actually spend almost 20 Years in that. Then he returned with all his collected results to Mars, stepped in front of all his people, held up his collected Data and thought to them "Here I bring you MUSIC". You know of course that Martians communicate via telepathy and have no sense of hearing...."
Hi,
What type of "inverse RIAA". That which was used to cut the record? For this I recommend to place an LP on the Turntable.
What is a "properly designed" RIAA Stage? Please define your terms. From where I stand one might argue that a properly designed RIAA stage incorporates an LCR RIAA to replicate inversly the cutting EQ and that uses coupling transformers (as pro audio always does).
In which case the answer is - you will hear the same - of course.
If you where to ask me to describe my subjective perception as to the subjective differences between for example my "Blight Loesch" RC equalised Preamp (aka Toccata MK II) which is passive RC EQ, no transformers and J-Fet/Valve cascode input and my current "MK IV" Toccata, whcih uses LCR EQ, MC stepup via transformer and transformerbased linestage/attenuator, I could comment, if felt so inclined.
But as I resent the implication that a Phonostage using LCR equalisation is NOT properly designed I shall be petulant and refuse to talk...
Anyway, it is so much more satisfying to answer such questions oneself, empirically, rather than asking others for their opinions, which are often based on prejudice and a priori, ex cathedra knowledge and this is harly either objective or subjective, it is simply orthodox, religious fanatical... So I suggest you simply build such a Phonostage and find out.
Sayonara
What type of "inverse RIAA". That which was used to cut the record? For this I recommend to place an LP on the Turntable.
What is a "properly designed" RIAA Stage? Please define your terms. From where I stand one might argue that a properly designed RIAA stage incorporates an LCR RIAA to replicate inversly the cutting EQ and that uses coupling transformers (as pro audio always does).
In which case the answer is - you will hear the same - of course.
If you where to ask me to describe my subjective perception as to the subjective differences between for example my "Blight Loesch" RC equalised Preamp (aka Toccata MK II) which is passive RC EQ, no transformers and J-Fet/Valve cascode input and my current "MK IV" Toccata, whcih uses LCR EQ, MC stepup via transformer and transformerbased linestage/attenuator, I could comment, if felt so inclined.
But as I resent the implication that a Phonostage using LCR equalisation is NOT properly designed I shall be petulant and refuse to talk...
Anyway, it is so much more satisfying to answer such questions oneself, empirically, rather than asking others for their opinions, which are often based on prejudice and a priori, ex cathedra knowledge and this is harly either objective or subjective, it is simply orthodox, religious fanatical... So I suggest you simply build such a Phonostage and find out.
Sayonara
With unlimited resources and unlimited time, I'd try everything that comes down the pipe. But my resources and time are greatly limited, so you'll pardon me for asking for a rational reason why this is something I should try. Don't be petulant; I made/make no implications one way or the other as to whether or not an LCR is a "proper" design- I'm sure that one can make a good circuit or a bad circuit using coils and transformers. What I'm trying to understand is why this is a BETTER circuit than replicating the standardized RIAA curve using resistors and capacitors in a much simpler and less expensive tube circuit.
Hi,
Well, compared to my various "references" (see list below) I find the Phonostage with the LCR EQ to present music as more aalive, with (to quote Allan Wright) greater "downward dynamic range" with a less "mechanical, more natural flow, also instrument tonality and timbre seems more natural (yes, I do regulary attend unaplified live concerts).
Small inflections in how instruments are played become easier audible (or at all audible?) and small rythmic changes are easier percieved. Massed strings have a little more defintion of the individual instruments without dissecting each string seperatly.
Yes, there is more "detail" too and the soundstage is wider and deeper, and all this audiophile bump, I'd simply say that music sounds more real.
The system for evaluation uses a pair of digitally equalised (modified Behringer Ultracurve UC 8024) Tannoy Monitor Red Speakers in corner reflex cabinets (Corner York).
Amplifiers are 300B SE Amplifiers using WE 437A Drivers, LCL coupling between valves, no electrolytic capacitors except in the heater supply, CLCLC filtered HT (using wideband chokes) and CLC filtered heaters. Rectifiers are WE274A, various 300B's are at hand, i like usually TJ/Sofia/Full Music Globes best.
Linestage is a transformer attenuator (S&B TX-102 MK I) with a GEC Plessy solid silver contact switch and mercury wetted reed relais for selection of input/polarity plus an option for operation with 6db passive gain.
Turntable is an Acoustic Solid "Solid One", around 40Kg of polished german Metal, unsuspended with three Arm/Pickup combos fitted, including Ortofon RS-212 Special & SPU-GTE , SME 3009 MKII (not improved) with a Denon DL-103 and a Origin Life Silver 250 Arm with a Goldring Elite MC Cartridge.
(Just as a BTW- All Arms except the OL are C37 Lackquered, as are all cartridges, including cantilever).
Currently at hand or used in comparisons where the following:
DIY Preamp based on the Shindo Labs "Claret" with various MC Steput Transformers including S&B TX-103.
Modified Consonance Reference 1.2 full function Preamp including upgraded internal MC Stepups and external S&B TX-103.
DIY version of the "l'Pacific" J-Fet Phonostage (passive RIAA, 2 SE stages, sould really be a Valve Phono except for sound, somewhat similar to the Pass Pearl) either with internal J-Fet MC Stage or external transformers
DIY Phono with OPA637 as discussed a while ago on the analogue board
Beyound these I have had for extensive listening at various times other DIY units by myself, including the Toccata MK I & II, also around where the CAT (probably early MK II version), Croft (Vitale and Epoch Elite), Musical Fidelity (Nuvista Pre), a few earlier ARC and CJ Preamps from repair/refurbishment jobs and probably more I forgot about, where commercial stuff is concerned.
I hope this gives some idea of where I'm coming from.
Sayonara
Well, compared to my various "references" (see list below) I find the Phonostage with the LCR EQ to present music as more aalive, with (to quote Allan Wright) greater "downward dynamic range" with a less "mechanical, more natural flow, also instrument tonality and timbre seems more natural (yes, I do regulary attend unaplified live concerts).
Small inflections in how instruments are played become easier audible (or at all audible?) and small rythmic changes are easier percieved. Massed strings have a little more defintion of the individual instruments without dissecting each string seperatly.
Yes, there is more "detail" too and the soundstage is wider and deeper, and all this audiophile bump, I'd simply say that music sounds more real.
The system for evaluation uses a pair of digitally equalised (modified Behringer Ultracurve UC 8024) Tannoy Monitor Red Speakers in corner reflex cabinets (Corner York).
Amplifiers are 300B SE Amplifiers using WE 437A Drivers, LCL coupling between valves, no electrolytic capacitors except in the heater supply, CLCLC filtered HT (using wideband chokes) and CLC filtered heaters. Rectifiers are WE274A, various 300B's are at hand, i like usually TJ/Sofia/Full Music Globes best.
Linestage is a transformer attenuator (S&B TX-102 MK I) with a GEC Plessy solid silver contact switch and mercury wetted reed relais for selection of input/polarity plus an option for operation with 6db passive gain.
Turntable is an Acoustic Solid "Solid One", around 40Kg of polished german Metal, unsuspended with three Arm/Pickup combos fitted, including Ortofon RS-212 Special & SPU-GTE , SME 3009 MKII (not improved) with a Denon DL-103 and a Origin Life Silver 250 Arm with a Goldring Elite MC Cartridge.
(Just as a BTW- All Arms except the OL are C37 Lackquered, as are all cartridges, including cantilever).
Currently at hand or used in comparisons where the following:
DIY Preamp based on the Shindo Labs "Claret" with various MC Steput Transformers including S&B TX-103.
Modified Consonance Reference 1.2 full function Preamp including upgraded internal MC Stepups and external S&B TX-103.
DIY version of the "l'Pacific" J-Fet Phonostage (passive RIAA, 2 SE stages, sould really be a Valve Phono except for sound, somewhat similar to the Pass Pearl) either with internal J-Fet MC Stage or external transformers
DIY Phono with OPA637 as discussed a while ago on the analogue board
Beyound these I have had for extensive listening at various times other DIY units by myself, including the Toccata MK I & II, also around where the CAT (probably early MK II version), Croft (Vitale and Epoch Elite), Musical Fidelity (Nuvista Pre), a few earlier ARC and CJ Preamps from repair/refurbishment jobs and probably more I forgot about, where commercial stuff is concerned.
I hope this gives some idea of where I'm coming from.
Sayonara
Sound of LCR RIAA
I can confirm the findings of the illustrious Kuei Yang Wang on the sound quality of LCR RIAA stages.
I performed the following experiment. The reference preamp was a modified Loesch style preamp. This consists of an jfet/417a cascode input stage, split passive RC, 6GK5, the rest of the passive RIAA, into a 5687 line stage. This is similar to the Toccata II mentioned by KYW.
I bought myself a canned LCR network which appears to be a knock off of the Tango EQ-600P for Korea. You can see it here:
http://www.allnicaudio.co.kr/lcr-unit.html
Being anxious to listen to the thing, I slapped together a very
crude solid state test bed. I grabbed an INA103 and set it up
for 55db gain. This had trouble driving the 600 ohm impedance of the LCR network, so I ran it into a 4:1 step down transformer and then t the LCR network. This was then fed directly to the 5687 line stage. This set up was a bit short on gain and another step up after the LCR network or another gain stage is probably adviseable. Still it provided a quick glimpse into the sound of an LCR preamp.
The results, at least to me, were a bit shocking. The INA103/LCR phono stage was much better than the jfet/417/6gk5 stage. It captured the tone and natural decay of instruments in a way I have never heard before.
So I'm in the process of building up a tube version. Here's my current thinking:
MC transformer - 6C45 transformer loaded (4:1) - LCR- step up transformer (1:4) - 6C45 (exact config undecided).
---Gary
I can confirm the findings of the illustrious Kuei Yang Wang on the sound quality of LCR RIAA stages.
I performed the following experiment. The reference preamp was a modified Loesch style preamp. This consists of an jfet/417a cascode input stage, split passive RC, 6GK5, the rest of the passive RIAA, into a 5687 line stage. This is similar to the Toccata II mentioned by KYW.
I bought myself a canned LCR network which appears to be a knock off of the Tango EQ-600P for Korea. You can see it here:
http://www.allnicaudio.co.kr/lcr-unit.html
Being anxious to listen to the thing, I slapped together a very
crude solid state test bed. I grabbed an INA103 and set it up
for 55db gain. This had trouble driving the 600 ohm impedance of the LCR network, so I ran it into a 4:1 step down transformer and then t the LCR network. This was then fed directly to the 5687 line stage. This set up was a bit short on gain and another step up after the LCR network or another gain stage is probably adviseable. Still it provided a quick glimpse into the sound of an LCR preamp.
The results, at least to me, were a bit shocking. The INA103/LCR phono stage was much better than the jfet/417/6gk5 stage. It captured the tone and natural decay of instruments in a way I have never heard before.
So I'm in the process of building up a tube version. Here's my current thinking:
MC transformer - 6C45 transformer loaded (4:1) - LCR- step up transformer (1:4) - 6C45 (exact config undecided).
---Gary
SY said:
to answer that question is relatively straightforward but a bit counter-intuitive when it comes to what we are taught about inductance vs capacitance.
In capacitance, due to the excess memory or retentive function of the dielectric, we end up with a small delay characteristic on the the drainage side of things. Ie, the complex LCR of the capacitor can and does get in the way of things.
When we switch to the use of an inductive circuit, we end up utilizing the far more linear and 'aetheric' considerations of a polarized density field, ie 'current'/storage of an inductor, and get something that when utilized in the correct way, in a phono eq, is far quicker to release energy than any capacitor. This, of course, is true... only when this aspect of inductors is understood and utilized correctly.
Remember, an inductor will disallow rail sag via current injection, via collapsing fields. A properly designed inductor will have the most linear field collapse or current injection. Far more linear and most specifically - far faster than any 'capacitor'.
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