Voltage mode vs current mode phono stages

I'm in the process of having a phono preamp made manufacturable by a well known audio company. The first thing they insisted upon was that the design would be implemented in SMD- purely for manufacturing purposes. This had it's own unique set of difficulties- for example, some of my preferred capacitors were not available on SMD, so a search for suitable items of a different technology (ceramic MLCC C0G vs Polypropylene film) was needed, together with a proof that the distortion characteristics were essentially equivalent.

The other aspect was that the preamp design investigated two possible implementations, either a voltage mode input, or a current mode input, and with the 75uS RIAA TC implemented in the first stage.

I ended up with a voltage mode input, as when designed for equivalent gain and RIAA characteristic there is, generally, no measurable or audible difference.

However, there are indeed differences in operation and implementation.

To put this somewhat in context, I designed a number of "transimpedance" amps while at ADI, most notably the AD846, together with a number of conventional opamps, so I am familiar with the concepts. The AD846 was designed to have almost perfect current conveyance properties and could be operated open loop as a transimpedance amplifier. Most opamps/amplifiers use negative feedback to achieve this goal, or have high distortion levels if operated open loop.

As I don't want to make this into a "white paper" I'll try to be brief.

1. A phono cartridge is a voltage generator (Vs) with an output impedance which is mostly a resistance in series with an inductance (R+Ls). This can be converted into the Thevenin equivalent current source- which is a scaled current (Vs/(R+Ls)) with the output impedance in parallel to ground.

If you take this current and drive it into a virtual ground, which shorts out the shunt components, and convey it to the load resistance (Rl) then the output voltage is Vs*Rl/(R+Ls). If Ls is small then the gain is completely dependent on the series resistance of the cartridge and will vary from cartridge to cartridge, and if LS is large there will be a HF roll off.

Any shunt capacitance will be essentially ignored.

If there is a resistor added in series with the virtual ground, then the current is shared between the equivalent shunt components and the series R, and the gain becomes even more variable.

Voltage mode lacks this complexity. Provided the load impedance is relatively large compared to R the gain is easy to determine.

However, the shunt capacitance is not ignored, but for MC cartridges the inductor is so small that all parasitic capacitance values are irrelevant, assuming the load R is small enough to damp out the LC resonance. 

Current mode does not experience this resonance, but correct loading Rs plus a phono stage with a suitably good ultrasonic overload margin will take care of the potential problem.

MM cartridges into a virtual ground are not rational unless there is a very large resistor in series with the virtual ground. This is because the R is large but L is even larger.

 

2. In voltage mode the input stage is non-inverting and will experience potentially substantial deviations about ground. For many opamps, particularly earlier generations than the most recent ones, this voltage will cause increases in distortion due to the operating conditions of the input transistors being changed. 

This distortion can be highly sensitive to the source impedance and the input signal level.

In the transresistance mode the virtual ground does not move, removing this source of distortion.

Modern audio IC opamps are generally designed with this problem in mind and exhibit negligible changes in distortion when operated in non-inverting mode.

These are the two main aspects of current versus voltage mode inputs.

There are other, more obscure, aspects.

I chose voltage mode, but also chose appropriate opamps to minimize the down side of the choice.

The bottom line is, when properly designed both current and voltage input designs can have equivalent performance from the perspective of distortion, frequency response etc.- but the voltage input design is more predictable and easier to specify. 

The voltage input design produced has very precise gain, extremely precise RIAA compliance and unmeasurably low distortion.

 

Dear @mijostyn  : Thank's.  That only confirm why several top ranked SS designs manufactres/designers are using from some years now thwe SMD. It's not only Channel D but Boulder, CH, and many others. To many real quality advantages to let pass.

 

Today I think that the only advantage of true hole devices is that any gentleman/audiophile/reviewer or whatever when open that SS design at least can see and read inside the circuit boards which devices ( vishat, caddok, bourns, panasonic, tdk, kemet, xicon, etc. ) are using the manufacturers  and the cirduit boards looks really good with. In change with SMD you have not so easy that information.

 

Anyway thank's again.

R.

@ledoux1238 Thanks! I did not know he had reviewed it. @rauliruegas check out ledoux's link. I know you are into SMD and ultra accurate RIAA circuits. 

Michael Fremer"s latest review of the Channel D Lino C 3.3

@rauliruegas , I can not disagree. I am taking a risk with the Channel D unit but then I hardly ever get a chance to audition units before I buy them. I do my research and cross my fingers. Rob Robinson is a very bright engineer who is totally bonkers over vinyl. His construction methods are right up to date and you can use his units with digital RIAA correction which again theoretically has its benefits, theoretically. We shall see. If it does not I'll sell it and move on. 

I have this acre of land right in the middle of Central park:-)

lewm: More than a year ago I emailed that information, please look for. Btw, the signal in the design unit was designed it pass through only one resistor in each attenuator.

Dear @mijostyn  : Many years ago I had the opportunity to listen almost the first ( I think? ) BMC current phono design and I can't remember nothing especial about. The SMD subject it's not only that we can have shorter signal paths in the boards but with lower noise and distortion levels.

 

I know you are in deep foundation with the current phono stages that's not a new technology but what is almost new are the latest 3-6 manufacturers with that kind of design including CH that in this case and with out listen it  is more marketing than other real value but I never listen to it.

J.Carr latter cartridge models came with very low internal  resistance and inductance and seems to me that he designed that way not precisely thinking on the " new " current phono designs because to me that could not has " common " sense " when the 99.9% of all phono stages are voltage designs.

 

Today " current " is the histoty of the day but not a consolidated/matured phono stage industry design. 

I think that the " devotes " ( as you ) to that current phono stage designs need  give more time to the designer knowledge deeper down there along the understanding of them with the cartridge role.

 

This is something as in the Cartridge Loading 2 where the OP with not really high knowledge levels about now is " fasinated " in that thread with the dialogue that analize current vs voltage phono stages but with out really know for sure through measures tests and listen tests. I'm sure that his knowledge level about improved " nothing " because that kind ofdialogue is not really something that today can enhance our each one listened sessions that at the end it's what all of us are looking for.

 

Anyway, to each his own.

 

Regards and enjoy the MUSIC NOT DISTPORTIONS,

R.

@lewm , you still have not told me why you gravitate towards the BMC. The quality and type of construction used in a unit are important indicators as is circuit design. As far as sonic performance is concerned, it is much harder to get a bead on it and frankly all great phono stages should sound exactly the same. We usually only get to hear them after the purchase. I will go with the best construction every time for the type of unit I want in this case a Current mode phono stage.  

Raul, are you thinking of the Goldpoint series attenuators for your and my Phonolinepreamp? Yes, you did advise me to replace the originals with those Goldpoints that use SMDs. Can you tell me what value, in terms of Kohms? One thing I noted is that Goldpoint claim they no longer need to sell ladder type attenuators (one resistor in circuit per position both in series and in parallel with the signal) because the SMD resistors raise the quality of the series type to that of a ladder type. (For others, series attenuator will have a string of resistors soldered end to end, with resistors added as you go increasingly attenuate the signal. This is usually inferior to a ladder type attenuator, if you are seeking Nirvana. Since there are so many solder joints in a series type attenuator circuit, it is no wonder at all that SMDs will work better.) I probably should look into doing the mod but when I did, I also considered using Khozmo shunt type attenuators and got stuck on the decision between the two. I use the Khozmo stereo balanced shunt attenuator in my MP1 and they are excellent. A shunt type places only one resistor in the circuit in parallel with the signal per setting. What I tried to convey to Mijostyn is that I would not choose between two components based ONLY on the fact that one uses SMDs and one does not or that one uses fiberglass PCBs and one does not.

IMO, informed by imagination and. some high ( as in orbital and beyond ) end electronics fabrication experience, you want a designer fluent in: point to point, boards, multi-layer boards..and SMD and integrated circuits. Helps if they have ears also. 

Carry on…..

Dear @lewm ​@mijostyn   : " what is the big deal about SMD components?  Good for op amps in circuits with very very wide bandwidth but not necessarily an audible upgrade with a phono stage.   "

 

Really? because it's precesily where the SMD can helps especiaLLY IN THE riaa CIRCUIT WHERE NORMALLY IS NOT DEVELOPED HIGH TEMPERATURE. wITH smd parts THE SIGNAL " RUNS " a way shorter path and in a phono circuit that's important.

 

Several months now I told you to change the attenuators in your phonolinepreamp for attenuators with the same Swiss mechanism but with SMD parts. I don't know if you did it and if not then do it and latter on come back with muyjost to comment about. Till you try it and almost as always everything belongs to your " imagination " that's wider than mine because I always try and make tests.

 

Regard and enjoy the MUSIC NOT DISTORTIONS,

R.

Fremer by and large has better equipment than most of us have, not necessarily better hearing.  He's old, like we are.  Like I said before, what is the big deal about SMD components?  Good for op amps in circuits with very very wide bandwidth but not necessarily an audible upgrade with a phono stage.  That said, the quality of construction of the Seta circuit does appear to be very high, judging only from photos.  I've not seen the innards of a BMC. I'm not buying any time soon, or maybe ever.

Mr Fremer would argue with that, but he has better hearing than I have. 

Really? I spoke to him at Axpona and he could hardly hear me, had to repeat myself like 10 times. 😉

@lewm , I looked at the BMC and read Fremer's review. The current price is $4800.00 which is not bad at all. They are built in China.

Comparing the BMC to the Seta + is relatively easy in regard to their physical attributes. The BMC is very nice looking although some would argue that the on-off switch(that huge knob in the center) is a little over-baked. The Seta + is industrial looking in comparison. Inside the units is a different story. The BMC uses through hole phenolic boards and the Seta + SMD construction on fiberglass boards. The BMC uses standard regulated power supplies (good ones) while the Seta + uses  lead acid batteries and a charging system that disconnects from the unit when in use, perfect isolation. The Seta + is made in America and costs over $9K with the optional RIAA board. Made in America covers the price differential. 

Fremer reviewed an older version of the BMC and liked it very much. He also reviewed the the Seta's little brother the Lino C which he also liked very much. I suspect both units are excellent phono stages and would have been SOTA if they were three times the price. I am in the same boat Lew is in. I really like the idea of a current mode phono stage but am not going to spend silly money on the CH Precision unit. I do not need the added complexity and it is a very complex unit and I do not feel like spending money on complexity. But I would bet dollars to donuts that blinded, few of us if any could reliably tell the difference between the three stages. Mr Fremer would argue with that, but he has better hearing than I have. 

You been on a ride yet? My wife and I have new bikes this year. The drive trains are somewhere between New Hampshire and Italy.

This year's ride is leaving Banff on the 10th of June and hoping to arrive at Antelope Wells, NM in under 30 days (we'll see). https://www.youtube.com/watch?v=MW_z-z3tfxw In 2019 I made it to the Brush Mountain Lodge; Steven of this video passed me on Union Pass in Wyoming...

@lewm , what makes the BMC you favorite?

@atmasphere , HI Ralph! It's been a while. You been on a ride yet? My wife and I have new bikes this year. The drive trains are somewhere between New Hampshire and Italy.

Very true. I have worked on SMD boards with a needle point on a Weller station using a magnifier lamp, 10X I think. If you remove all the solder with a wick and have things nice and flat you can tack the component down with a dab of thick cyanoacrylate. When it dries solder the contacts. 

Personally, I'm a traditionalist and prefer the point to point wiring in your amps, a thing of beauty. Makes me want to wire a set for myself:-)

This is very true - the proper equipment required to work on SMD boards is around $100k.

@dover That depends on the type of SMDs used. The 0402s and the 0201s can be done with fairly simple equipment certainly costing maybe $500 if you stretch it! It can also be done by hand, which is how all of our class D stuff is done (locally). All you need is the right kind of solder station, proper magnification and a steady hand.

I suppose some aspects of SMD construction are beneficial, especially in a device centered around an op amp, but not all, and not when repair is needed.

This is very true - the proper equipment required to work on SMD boards is around $100k. Most tech's can't afford this investment, and if a manufacturer using SMD technology goes bust - then your precious unit, when it develops a problem will be toast. Even with most manufacturers that use SMD technology, if there is a fault - the "repair" is a new board.

Personally I would never buy a piece of audio kit using SMD technology - seen too many disasters. If you do buy an SMD based unit you have to assume it will need replacing within 5 years.

Without ever having heard or even seen any current drive phono stage, my current favorite just based on tech and reviews and cost, plus balanced operation, would be BMC MCCI.

I suppose some aspects of SMD construction are beneficial, especially in a device centered around an op amp, but not all, and not when repair is needed.

@lewm , IMHO the Grails are horrendously over priced. Looking at the internals the construction quality is not up to modern standards. As an example the boards are through hole not surface mount which is considered to be better. 

The Seta L Plus has significantly better construction, a better power supply and comes in at $10K. It's only down sides are it is not very versatile having only one input and switching between current and voltage mode requires going into the unit and removing or replacing a jumper. You would have no problem with that and I greatly prefer the simplicity.

Hi Ralph, You wrote, "This suggests that as the impedance of the cartridge goes up, the gain of the circuit goes down, which is probably good since the output of the cartridge will be higher."  The linear relationship between voltage output and stylus velocity (higher at higher frequencies) is accounted for by the RIAA correction.  Would you want the cartridge to alter that relationship by virtue of an upgoing internal impedance?

@lewm I don't think I would employ any EQ on the transimpedance input (meaning the opamp). I would leave that for later in the circuit, such as a passive EQ network at the output of the opamp. In this case the constant velocity aspect of the cartridge really has nothing to do with it.

@lewm 

I am curious about what happens when you mate a Sussuro, for example, with a current driven phono stage.

This post from a recent Little Loco thread may shed some light:

I ended up with a Soundsmith Sussurro cartridge, but the Low Z (Low impedance) version. I would suggest if you were to buy one make sure Peter Lederman knows it's for a transimpedance stage.

The long version is that I contacted Peter and he contacted Ron Sutherland and compared notes. Peter built a low impedance version of the Sussurro and sent to me. I didn't like it, thought it was rolled off up top a bit. Peter offered to refund my money but I told him I would prefer he try to resolve and asked him if he would be willing to put in the time to do that. He agreed and I ended up sending the cartridge and the Little Loco to him to work with. The results are as you would expect if one of the most knowledgeable and talented guys in the cartridge/phono industry had your gear on his bench...an excellent match, I'm loving what I am hearing. 

My comparison is the Audiotechnica ART-9 which sounds pretty darn good but not nearly as good as the Low Z Sussurro, and my digital: Innuos Zen MKIII and Bricasti M1 SE MDX (who names these things?!) DAC. 

I actually picked the cartridge and Little Loco up at his shop because I was in the area visiting family. Peter took me on a tour, we listened to music, talked about dogs...he's a great guy, I'm really thankful for the entire experience (and for sure I'm glad he was willing to take the time to make the cartridge sound so good).

Clearthinker, that’s an impressive list of cartridges. Your colibri with 36 ohm internal resistance probably has a healthy voltage output. Do you run it into the Grail in current mode or voltage mode or does the Grail even offer that choice via separate pairs of inputs? Thx.

Yes it was the Boulder 1008.  I really didn't like it.  It sounded very 'transistory'.  I didn't move on to the 2008 mainly because of the price, but I felt it likely there would be a house sound that doesn't suit me.

I have Ortofons A90, Anna, Verismo; van den Huls Grasshoppers II and IV and Colibri.  Also Audio Technica ART1000, another sleeper, uses entirely difference suspension engineering.  These are all low impedence, between 3 - 7 ohms, the ART1000 is only 3 ohm, save the Colibri XGP which is 36 ohm.  I do not hear any artifacts that distinguish that but overall these vdHs have fallen behind a little.  The ART and the Verismo are the best I have.  Anna has a high mass that unfortunately doesn't suit my ultra low mass parallel tracking arm, so I use it in my second system where the amplification is vintage.

@clearthinker If the Grail was ‘under-exposed’,  it certainly has caught my attention with the discussion here. 

What are some of the higher internal impedance LOMC you have tried? Presumably it was the Boulder 1008 that you made the compare to?

Here is the vdH website on their phono stages:

https://www.vandenhul.com/product-category/electronics/

The way I read it, the SB offers balanced operation; the base model may only offer XLR inputs into an SE circuit. I don't know. The language is only a little less vague and confusing than what you find on the Channel D website. Clearthinker, I think you made the most cost-effective choice among the many Grail iterations, but it occurs to me that their statement about auto matching for cartridges in the 40-400 ohm range might mean that if the cartridge has an internal Z of 4 to 40 ohms, which covers just about all low output LOMC types, then the current drive stage will accommodate it.  It's a bit confusing and suggests that voltage drive is an option.  I cannot blame drbond for being confused. But you own one, so let us know.  Most reviewers don't have a clue.

@drbond 

Firstly my Grail is the SB, not SE, sorry.  I have had it about two years.

The model range is Grail, entry.  SB, separate power supply on umbilical, but same amplification circuitry.  SE, separate supply for each channel.  SE+, some selected components.  SB and SE can be run balanced or single-ended but input and output must be the same mode.  One might have presumed the SE is single-ended and SB balanced.  Not so.

The reading of the literature you mention is a mis-reading.  In the vdH specs it is stated that the current operation provides automatic matching for cartridges in the 40-400 ohms.  On the SE and SB there is the additional possibility of changing the capacitance by hard-wiring capacitors into the back of an XLR socket.  vdH suggests this might be done in the case of moving magnet cartridges but doesn't see the need on moving coils.

I have listened to a wide range of top-end MC cartridges on the SB and it works well with all of them.  It is priced at c.£14k in the UK, but I believe cheaper in the US.  In my estimation it is at least a match for amps selling at double that.  For instance I tried the Boulder and found that to be dry and over-clinical, analytic rather than musical compared with the SB.  I found it noticeably better than the AR Ref 3 and lesser ARs.

@clearthinker 

Supposedly, one purported advantage of the current based phono stages is that you don't need any loading.  Some literature on the Grail SE indicates that you have options for MC loading from 40-400 ohms; however, other discussion about the same phono stage says that you don't need to adjust loading, as it's done automatically through the circuit.  Which is correct? 
Thanks. 

Yes, the Grail is a very under-exposed amp.  I have had the SE for two years having auditioned it at home for three months against two other similarly priced units (COVID prevented the dealer taking it back).

There are three Grails.  SE is the middle one, perhaps a bit more towards the flagship than the base.  It can run single ended or balanced.  I run balanced from cartridge to power amp.

Grail has a good claim to be in the best sounding group of phono amps.  It manages to combine a near clinical accuracy with a musical presentation, which is rare in phono amps; one usually has to favour one or the other - as others have stated, warm or lean.

I won't be replacing it.

I don’t understand. If you order the Channel D with digital RIAA, then you have to supply your own outboard AD/DA converter? Or does the Seta output a digital signal that the user has to convert back to analog, or what?

@lewm , I already have the program so, yes I plan on trying it. But, I am ordering the RIAA board as back up. I should be able to do it with the equipment I have now as long as I do not get into a jitter war. Channel D recommends a combination ADC/DAC using the same clock. Their favorite is the Lynx HiLo. Nice unit but I would rather not have to buy one. I'm pretty sure digital correction will sound fine. The question is how much more of a pita is it going to be playing records that way vs the old fashioned way. You know I will be happy to forward my opinion.

Peter Ledermann related to me directly that his MI cartridges will not work well with a current mode phono stage. The high frequencies will be rolled off. He did not give me the reason why but I am sure it has something to do with inductance and impedance.

lewm,

I would reach out to PL for clarification. FWIW, he was using a Loco with one of his LOMI pickups when he indicated the results were very encouraging as long as proper cables were used.

Boothroyd,

I found this in the Sussuro cartridge owners manual:

"Please also note that some designs of “current amplifier” preamp circuits will not allow loading in the range required, causing the Sussurro MK II ES to sound very dull – caused by improper loading, resulting in loss of high frequencies."

What I could not find was a spec for the inductance of the Sussuro, but if memory serves it is about 50 mH.  This would give an impedance of 314 ohms at 1000Hz.  Let's say it's only 10mH; then divide 314 by 5.  Still high for a typical current driven phono.  Add the impedance due to inductance to the coil resistance of only 10 ohms.  I emphasize again that I love MI cartridges as a rule.  This is more about the usefulness of most current driven phonos stages.

Hi Ralph, You wrote, "This suggests that as the impedance of the cartridge goes up, the gain of the circuit goes down, which is probably good since the output of the cartridge will be higher."  The linear relationship between voltage output and stylus velocity (higher at higher frequencies) is accounted for by the RIAA correction.  Would you want the cartridge to alter that relationship by virtue of an upgoing internal impedance? Also, the paradigm for current drive is you want the cartridge to have a very low internal resistance/impedance to begin with, which makes it a decent current generator.  Obviously, I am parroting ideas that are in the air without much depth of knowledge. But this question points out how consumers are a bit confused by "current drive" or a term like "transimpedance".  I think there are an array of products that each may do it differently enough to defy generalization.

@lewm Since the cartridge functions as the input resistor to the opamp, the impedance of the cartridge affects the gain of the circuit (as you probably know, the gain of an opamp will be the ratio between the feedback resistor and the input resistor). This suggests that as the impedance of the cartridge goes up, the gain of the circuit goes down, which is probably good since the output of the cartridge will be higher.

I've not messed with this circuit to any great degree, so I don't know what constraints might exist, but I'm sure there are limitations- there always are. I just thought I'd point this first bit out.

Boothroyd, LOMC cartridges, like the Lyra cartridges you mention, will have inductance in the low micro-Henry range.  The low output MI cartridges made and marketed by SS have an inductance in the low milli-Henry range.  In other words, the inductance of their LOMI cartridges is about 1000X higher than that of a Lyra or other typical LOMC.  (This is no attempt to critique the SS cartridges; I actually prefer MI cartridges over most other types, and I am grateful to SS for carrying the MI banner.) The point is that level of inductance might affect the cartridge's capacity to produce signal as current, especially at high frequencies. Thus I am curious about what happens when you mate a Sussuro, for example, with a current driven phono stage.

Mijo, are you going for digital RIAA correction?

 Isn't the difference between a 'warm' and 'lean' sounding system a shift in frequency responses? 

@ledoux1238 IME on a system level that is often caused by distortion. The ear assigns a tonality to all forms of distortion. Lower orders (2nd- 4th) add warmth and they can mask the presence of the higher orders. If the higher orders are not masked, even in tiny amounts they cause harshness and brightness. The ear is keenly sensitive to them as it uses them to sense sound pressure.

For example in a phono section to know whether its a frequency response error causing the tonality or distortion, you have to measure the phono section with an inverse RIAA network to see how accurate it is. If its has flat response but sounds bright, distortion is likely the cause.

@ledoux1238 , Yes, I will report on what I think in my system. That is a lot of stuff to cram into a Lino C! I was going to get a Lino C but it turns out the Seta L plus is a better unit even though it is less versatile. 

Most of the differences we hear are in amplitude variation across the frequency band, bright, dark, warm, vivid are all caused by frequency variation to which we are quite sensitive. These variations can be caused by intension, our systems, resonances anywhere and acoustics and are way more prevalent than other errors such as distortion and group delays. 

@lewm 

My question was more about the effect of MI inductance on cartridge output impedance as frequency increases and how that affects the efficiency of current drive.

Seems like a question for PL. I would pose a similar inquiry for J Carr to the evolution of the Lambda Series of Atlas & Etna as their current delivery seems to be much improved over previous versions. I suspect lower inductance generators.

@lewm

"Suitable" = very low capacitance, I assume. 

Please excuse my ignorance and technical understanding, but I have a strong opinion that the + & - cartridge signal paths should be as similar as possible. Such a belief shuns any use of coaxial cable - yes, inductance not good.

On transimpedance phono inputs featuring RCA style inputs, such an assumption isn’t so intuitive. Knowledge of SME’s use of twisted pair phono cable construction sheds light perfectly on this scenario as each + & - path of their RCA outputs feature identical runs all the way back to the cartridge pins exhibiting perfectly balanced cartridge signals without XLR outputs. Continuing on that theme, SME only accesses the optional signal shield via a “drain” wire which exits the rear of the output RCA connector for optional noise control if needed - just tie it with chassis ground.

As far as keeping capacitance low, as long as each + & - cartridge signal path is again equal, I cannot see where that would hurt - Mogami W2549 works exceptionally well and is a well known low capacitance conductor.

@dover Would you confirm if my guess on the Vd Hul Grail is correct? Like Lew, I did a bit more research on it, and it seems a very accomplished unit. 

@ledoux1238 

No it is as @lewm  stated - I have a bespoke moving coil step up using current mode/current sensing - the output is connected to the Marantz 7 phono (stage )  input.

It is not available commercially.

 

@atmasphere Of course, Ralph, you are right. A built-in phono, well chosen, is also a simplicity. I come from that tradition: Audible Illusions, CAT, MFA Luminescence. My current situation of line + phono stage is really to explore the possibilities of the medium, it's a learning experience for me, not a search for a particular sound.

 

@mijostyn Isn't the difference between a 'warm' and 'lean' sounding system a shift in frequency responses?  Or are you saying that the shift in frequency response is really a shift away from neutral / natural sound? I thought that's what difference devices do, ameliorate or exacerbate sound through the manipulation of frequency responses. Sorry, I get a bit hung up on terminology.

Please provide reporting of the Seta L+ somewhere in this forum. It would provide important data point, especially coming from you. BTW, in my communication with Rob at Channel D, he found a way to squeeze a '1/4 Seta L20' into a Lino C ( with a modified chassis). Yes, fitting a quarter of his TOTL phono into a Lino C! 

 

@dover Would you confirm if my guess on the Vd Hul Grail is correct? Like Lew, I did a bit more research on it, and it seems a very accomplished unit. Fremer compared it favorably with the CH Precision. Would be interested in hearing more from you on the Grail. Thanks!

 

 

 

 

 

 

 

 

 

 

"Suitable" = very low capacitance, I assume. My question was more about the effect of MI inductance on cartridge output impedance as frequency increases and how that affects the efficiency of current drive.  It would be of interest to know which of the many "transimpedance" phono stages PL uses.  Because my own investigation indicates they vary quite a bit in input impedance, some not so close to zero as one might like.

@lewm 

Have you tried to drive a current mode phono stage with an SS LOMI?

While I have not, Peter explained to me that he is quite impressed with the results as long as suitable phono cables are utilized - something which I’ve often tried to emphasize. 

whereas voltage mode is an endless pursuit of SUT’s and loading. I have admittedly rather entry level stuff, so not the final word. 

@ledoux1238 If you have the right voltage mode phono section, its also plug and play- no SUT and no worries about loading.

@lewm , I think Fremer sleeps with his CH Precision. Nice unit but way more stuff than I need. I prefer simple.

I will be able to address this better in a while as I ordered a Channel D Seta L Plus which can be run either way. I plan to run it in current mode because of the theoretical advantage, the most important one is less interference with tracking. Every generator is also a motor. With less impedance this effect is more limited. 

@ledoux1238 , I think what you are hearing is a frequency response shift. Whether or not one is more or less accurate than the other is up for grabs. If I have two systems and turn the upper midrange and treble just 2 dB on one of them everyone listening will prefer the brighter unit even though it is "less accurate." In my own system I intentionally boost the bass because I feel it gives you more of the experience of a live performance even though it is "less accurate." This is why everyone has the right to listen to whatever they like. Unfortunately, that might make someone else cringe. My point is what a system sounds like is an extremely fast moving target. Interpreting what other people say is virtually impossible. There are characteristics which are more definable like those of the image. 

Dover did not mention what current driven device he is using, so far as I can see.  However, he did say he feeds its output to the phono section of a Marantz 7 preamplifier.  That suggests he is using one of the very few available outboard devices that do the current to voltage conversion ahead of any conventional MM phono stage.  I think Sutherland makes such a device and a few others.  I think that's a great idea, as it does not require or may not require a major purchase cost for a whole new phono stage.  I am using such a device that was custom made for me, not commercially available. I use it only with the Ortofon MC2000 cartridge.  Output goes to a modified Silvaweld SWH550 phono stage in MM mode.  I have two other voltage driven phono stages that both have enough intrinsic MC gain for any of my other MC cartridges.

I did some reading on the van den Hul Grail.  The basic unit seems to be SE only.  The SB version costs nearly twice as much and provides balanced circuitry and some other unique features.  Depending upon whose review you read, the RIAA correction is done using either only inductors and resistors (LR type) or using capacitors along with LR (LCR).  Then there are the SE and SE+ versions that cost 3X as much as the base and include upgraded power supplies. I am not sure whether the base model (~$9000) has the fancy RIAA circuit or not. Fremer compared the base and the SE versions to the CH Precision with X1 PS.

I think this is like many other things in audio. An allegedly "better" technology does not mean the listener will prefer it sonically and, as with everything, you need to try and see. I recently had a current-mode phono preamp for audition, but I much preferred a similarly-priced voltage-mode preamp, which was slightly noisier, but much better to my ears. Understanding the technology is fine, but it always comes back to the same old story. No getting around it, IMO.