Resurrection...
Decided to build Mad_K's circuit. Too simple not to although the current availability of the 170s does present an issue.
Yess I've read 'most' of the Salas Upgraded versions.
Fascinating and Epic length threads
Baby steps first however.
Damn if this thing doesn't sound Good!
Previous claims were Not exaggerated...Perfect tonal balance.. and exquisitely detailed. What's not to like?
Ran it on 2 9v alkalines as a tester (~19V as opposed to the requisite 24v.. Mainly as I fitted 7.5ma Idss 170's Sounded "good' on the alkalines. Subsequently switched to a 19V Laptop brick Smps.
Hey! it was just sitting there
NO audible differences.
Gonna have to get bored with this thing .. Before.. I attempt a Salas version.
Despite having accumulated all the parts for a couple of version builds.
Decided to build Mad_K's circuit. Too simple not to although the current availability of the 170s does present an issue.
Yess I've read 'most' of the Salas Upgraded versions.
Fascinating and Epic length threads
Baby steps first however.
Damn if this thing doesn't sound Good!
Previous claims were Not exaggerated...Perfect tonal balance.. and exquisitely detailed. What's not to like?
Ran it on 2 9v alkalines as a tester (~19V as opposed to the requisite 24v.. Mainly as I fitted 7.5ma Idss 170's Sounded "good' on the alkalines. Subsequently switched to a 19V Laptop brick Smps.
Hey! it was just sitting there
NO audible differences.Gonna have to get bored with this thing .. Before.. I attempt a Salas version.
Despite having accumulated all the parts for a couple of version builds.
.
Hi aplt
It is a 2K4 to both the JFET drains on Mad_Ks original schematic.
Si.
t.S.E.c
.
... & Mr. Walters from 'Le Maison de L' Audiophile', Paris ... original 'Pacific' schematic.
.
Attachments
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Thanks! You can't be too careful with this stuff. Does anyone have the circuit for the Salas version? Sound comparison?
.
Hi aplt
It is a 2K4 to both the JFET drains on Mad_Ks original schematic.
Si.
t.S.E.c
.
... & Mr. Walters from 'Le Maison de L' Audiophile', Paris ... original 'Pacific' schematic.
.
All the circuits shown here seem to be of a common topology, namely 2 JFET gain stages with a passive RIAA filter in between.
The issue I have with such topology is of course the poor PSRR.
In particular, the power supply noise from the first stage is further amplified by the second gain stage.
Of course you can invest in a ultra low noise power supply, such as the excellent LT3045.
But perhaps one can also consider a topology similar to the vacuum state phono stage :
http://www.vacuumstate.com/images_upload/gross/rtp5_rev_1_s.gif
It still has only 4 active devices, but only one gain stage.
The tube cascode can of course be substituted by the likes of 2SK216.
The balanced outputs see the same power supply noise and therefore cancel them out.
If you do not like balanced output, you can just hang a transformer at the output.
The other approach is to use folded cascode and current source to fold the drain resistor to ground.
An excellent example is the Scott Wurcer balanced phono.
But that is no longer "ultrasimple".
A simplified universal differential or single ended phono preamp
A third approach that I like a lot is the balanced version of Mr.Evil's phono :
Mr Evil's Realm - Phono Preamplifier
I can tell you from personal experience that it really is worth the extra "complexity" :
https://www.diyaudio.com/forums/analogue-source/54658-jfet-loop-riaa-pre-amp.html#post610663
Patrick
The issue I have with such topology is of course the poor PSRR.
In particular, the power supply noise from the first stage is further amplified by the second gain stage.
Of course you can invest in a ultra low noise power supply, such as the excellent LT3045.
But perhaps one can also consider a topology similar to the vacuum state phono stage :
http://www.vacuumstate.com/images_upload/gross/rtp5_rev_1_s.gif
It still has only 4 active devices, but only one gain stage.
The tube cascode can of course be substituted by the likes of 2SK216.
The balanced outputs see the same power supply noise and therefore cancel them out.
If you do not like balanced output, you can just hang a transformer at the output.
The other approach is to use folded cascode and current source to fold the drain resistor to ground.
An excellent example is the Scott Wurcer balanced phono.
But that is no longer "ultrasimple".
A simplified universal differential or single ended phono preamp
A third approach that I like a lot is the balanced version of Mr.Evil's phono :
Mr Evil's Realm - Phono Preamplifier
I can tell you from personal experience that it really is worth the extra "complexity" :
https://www.diyaudio.com/forums/analogue-source/54658-jfet-loop-riaa-pre-amp.html#post610663
Patrick
Sling one together ... it could be c O O L
.
Interestingly enough, there have been at least several very reliable reports ...
... that the 'Pacific' works just great, using nothing more than an ordinary SMPS from a laptop !
It doesn't seem very 'audiophile' to me but reliable reports are reliable reports.
1-Ton worth of chokes enough to flatten the Roadrunner ...
... a couple of spare 9 Volts ...
... some AAs or serious Ds ...
... or just the previously mentioned laptop-brick ...
... the 'Pacific' has undeniably captured the attention of many 'music' fans !
Spec. beaters might be disappointed but music listeners might not.
I really must join 'The Club' and sling one together one day.
Si.
t.S.E.c
.
.
Interestingly enough, there have been at least several very reliable reports ...
... that the 'Pacific' works just great, using nothing more than an ordinary SMPS from a laptop !
It doesn't seem very 'audiophile' to me
but reliable reports are reliable reports. 1-Ton worth of chokes enough to flatten the Roadrunner ...
... a couple of spare 9 Volts ...
... some AAs or serious Ds ...
... or just the previously mentioned laptop-brick ...
... the 'Pacific' has undeniably captured the attention of many 'music' fans !
Spec. beaters
might be disappointed but music listeners might not. I really must join 'The Club' and sling one together one day.
Si.
t.S.E.c
.
Don't build this you'll be very disapointed.
.
My " level of expectations " would be ...
... that after a relatively simple build ...
... without too much difficult matching & without the frustration of a design containing almost unobtanium parts ...
... the 'music lover' who wishes to build a great sounding preamp, without being Albert Einstein ...
... would most likely be ploughing through their record collection at this very minute ...
... & enjoying every moment !
They could be totally miserable of course ... but I doubt it somehow !
Meanwhile they can be 'dreaming' of $$$ Nirvana !
Si.
t.S.E.c
I just love this build from the previous << Page ... You can just use regular perf. board easy enough though.
.
.
My " level of expectations " would be ...
... that after a relatively simple build ...
... without too much difficult matching & without the frustration of a design containing almost unobtanium parts ...
... the 'music lover' who wishes to build a great sounding preamp, without being Albert Einstein ...
... would most likely be ploughing through their record collection at this very minute ...
... & enjoying every moment !
They could be totally miserable of course
... but I doubt it somehow ! Meanwhile they can be 'dreaming' of $$$ Nirvana !
Si.
t.S.E.c
I just love this build from the previous << Page ... You can just use regular perf. board easy enough though.
.
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I built an almost identical circuit around 2000 dead bug style with the Toshiba pairs in the oversized TO-92 that a friend bought for me at the Akihabara. I used it for years.
The caps were Fdyne PP because one of our techs used to work there and was big on the "sound" of caps.
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.
ThorstenL :-
" We build the whole circuit hard wired, in a copprfoil clad wooden enclosure. We used Holco Resistors (sorry, no longer available as non-magnetic, current Holco's are NDFG), LCR 0.47uF Foil & Film Coupling Capacitors (plus MIT 2u2 PPMF "bypass" on the output) and LCR Polystyrene Cap's for the EQ. This Parts Mixture is true "UK Style" and most components are/where available from Radio Spares and/or Farnell."
" The gain is actually higher than 90, assuming the correct FET's are used. The 2SK170 @ 5mA has around 30mS (30mA/V) transconductance and operates into around 2k4 Loads. This gives a stage gain of 30mA*2.4k = 72. With 2 stages the overall gain becomes 5200 or 74db, of which a bit over 20db are lost in the passive RIAA EQ.
So the Pacific after accounting for the RIAA has around 60db Gain and around 0.15uV Ein (150nV Input Referred Noise) which makes it (marginally) suitable for medium output MC's without further Stepup or Pre-Pre. Output Impedance is around 2k. Not bad for a brutally simple circuit.
A friends Pacific runs fine and sounds VERY good. Originally it used 9V Block Batteries, when it stayed with me for a while (it drove a S&B TX-102 ever so much better than my Shindo copy Preamp) I converted it to using a 24V non looped switching supply, with better sound than we got from the batteries and no regular recharging!!!! "
.
ThorstenL :-
" We build the whole circuit hard wired, in a copprfoil clad wooden enclosure. We used Holco Resistors (sorry, no longer available as non-magnetic, current Holco's are NDFG), LCR 0.47uF Foil & Film Coupling Capacitors (plus MIT 2u2 PPMF "bypass" on the output) and LCR Polystyrene Cap's for the EQ. This Parts Mixture is true "UK Style" and most components are/where available from Radio Spares and/or Farnell."
" The gain is actually higher than 90, assuming the correct FET's are used. The 2SK170 @ 5mA has around 30mS (30mA/V) transconductance and operates into around 2k4 Loads. This gives a stage gain of 30mA*2.4k = 72. With 2 stages the overall gain becomes 5200 or 74db, of which a bit over 20db are lost in the passive RIAA EQ.
So the Pacific after accounting for the RIAA has around 60db Gain and around 0.15uV Ein (150nV Input Referred Noise) which makes it (marginally) suitable for medium output MC's without further Stepup or Pre-Pre. Output Impedance is around 2k. Not bad for a brutally simple circuit.
A friends Pacific runs fine and sounds VERY good. Originally it used 9V Block Batteries, when it stayed with me for a while (it drove a S&B TX-102 ever so much better than my Shindo copy Preamp) I converted it to using a 24V non looped switching supply, with better sound than we got from the batteries and no regular recharging!!!! "
.
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The Unetched Copper Board worked better than Perf board for me at least.
IF OCD/Anal A set of (old skool) Nicad Batteries Gives the V best possible PS.
Research (Albeit a while back) found that Nicads (and Only Nicads) gave such clean stable power, that it proved pure beyond the design range of the test lab equipment used.
Nicads of Decent pedigree are becoming tricky to source these days. But Sanyo or GP brands (best of Breed) can still be found in the 3000+ mah sizes
That said, this gizmo uses such little power that batteries last a looong time. And My Sanyo Nicads ..self drain.. faster than the Phono drains them.
So yeah.. An overnight recharge is necessary at 6~8 week intervals.
Small user price IMO.
IF
OCD/Anal A set of (old skool) Nicad Batteries Gives the V best possible PS.Research (Albeit a while back) found that Nicads (and Only Nicads) gave such clean stable power, that it proved pure beyond the design range of the test lab equipment used.
Nicads of Decent pedigree are becoming tricky to source these days. But Sanyo or GP brands (best of Breed) can still be found in the 3000+ mah sizes
That said, this gizmo uses such little power that batteries last a looong time. And My Sanyo Nicads ..self drain.. faster than the Phono drains them.
So yeah.. An overnight recharge is necessary at 6~8 week intervals.
Small user price IMO.
In progress 5-6 different phonos with all kind of material (MKT, styroflex, metal film, carbon comp, carbon film etc, expensive materials, very cheap etc) following MadsK schematic, which is very linear showing RIAA deviation of cca 0.1-0.2 dB.. i want to test all interesting JFETs on target available today from Mouser.. and see what can be done.
candidates:
863-2SK2394-6-TB-E,
863-CPH3910-TL-E,
512-BSR58,
863-2SK3557-7-TB-E,
757-2SK209YTE85LF,
512-MMBF5103,
512-MMBF4093,
863-NSVJ3557SA3T1G
candidates:
863-2SK2394-6-TB-E,
863-CPH3910-TL-E,
512-BSR58,
863-2SK3557-7-TB-E,
757-2SK209YTE85LF,
512-MMBF5103,
512-MMBF4093,
863-NSVJ3557SA3T1G