Power Supply for Neurochrome 686

Appraisal of fully pimped Neurochrome 686

Leading on from the discussion in this thread, the aforementioned 686 is now fully built with the following upgrades:

Copper RCA input sockets, copper speaker binding posts, gold plated IEC mains input socket, Nichicon KG Gold Tune reservoir capacitors and a
600VA O core transformer with individual secondaries for L and R channels. All internal wiring after the rectifiers is Triple C. The build is thus dual mono.

The source equipment used is Technics SL1200 TT, Dynavector Karat Ruby line contact cartridge, Bigbottle Ultime dual mono phono stage, BT2 (near)
equivalent preamp. The speakers used were Thiel CS2.2 and all cabling is OCC.

The comparison power amplifier was my own dual mono Neurochrome 286. Assuming any audible differences are not down to using 286 or 686 pcbs, as
the published spec is virtually identical, the differences have to be attributed to the listed upgrades above.

The 286 has gold plated brass connectors, bog standard internal wiring (not OCC or triple C) but does have L and R individual SMPS supplies. I do
have to state that I have some copper binding posts on order as the start of my own upgrade path. Space is very tight though.


Firstly I want to say that the overall performance from vinyl is sensational, I often have to pinch myself that vinyl replay can be at such an incredibly high
level from a rock being dragged through a plastic groove. I'm sure the circuitry used in the Ultime phono stage plays a massive part in this.

The test record was The John Barnes Roy Williams Jazzband, with very well recorded tracks.
Playing through the 286 was very enjoyable with plenty of clear space and natural sounding instruments.

Moving on the the fully pimped 686 initially seemed to be more of the same, but prolonged listening revealed that the brass in particular had more bite.
The trumpet and sax had more 'rasp' to the sound, in fact being a more realistic representation of the actual instruments, to my mind.

In the ultimate goal for better 'accuracy' or 'transparency' (please substitute your own preferred descriptors here) the pimped 686 is a step up for sure.

Thanks for the technical update Alan, I haven't been near a PC for a few days and hate doing long posts on my phone so was going to do it tomorrow, feel free to add the pics if you like?

I'll get to hear it this week but needless to say it will be first class due to the design and indeed builder!

Thanks again

- UPDATE -

I took delivery of this yesterday courtesy of Alan, very kind of him to drop it back to me on his travels. Certainly gave me peace of mind knowing it was in good hands rather than at the mercy of a courier company . . .


I plugged it in and left it to play for a time while I went about evening routine of making some food and trying to get younglings to bed etc etc.



Sat down for my first proper listen approx 8PM.



Initially I found it difficult to compare as I hadn't heard anything with the 686's level of transparency and clarity. I'd grown quite accustomed to swapping between a little ICE Power Class D (120w) and a 300B SET I'd recently pulled off the shelf, the 300B being freshly fettled with new regulators by Alan. The ICE Power amp has it's charm actually. I'd given it some proper input RCA's and binding posts accordingly whilst replacing the internal signal wiring with OCC stuff. It sounded quite big, well rounded and lively. Unfortunately even though my preamp can give it a relatively high output it really ran out of puff as the volume approached 10/11 on the dial. Where the 686 (and other amps) really start to sing.



At low volume the sound was actually excellent and with some more efficient, less power hungry speakers, it would do sterling service. I'm probably going to run it in my lounge system ultimately.



With the 300B things are also very interesting. The combination of the tube rectified 300B and electrostatic panels of the Logan's, is mesmerising. The 'speed' of a SET combined with stats really can sound glorious. This particular SET also has unusually good low end performance for a valve amp. Likely due to the giant transformers but it can really grip the low end better than all other valve amplifiers I've heard. The current handling of this amplifier is clearly an important factor, because at the same volume point (10/11) the SPL's are higher than the ICE Power amplifier. It also didn't lose grip or coherence which I was very impressed with.

One caveat to using an all valve pre and power combination however is that things can get a bit too 'lush' and indeed tube influenced shall we say. On some material (acoustic/jazz/vocal) it was possibly the best I'd heard my system perform (including the 686 in its prior guise, although as it has been nearly 3 months I cannot swear to that!). However on material with more going on I did feel it was giving up 'some' detail in the name of warmth. The presentation was delightfully ethereal however with a huge amount of ambiance and atmosphere on show.




So how was the upgraded 686 sounding in comparison.




Hmmm . . . . what's that. Doesn't have the impact I remember. Doesn't seem to have the ambiance or atmosphere I had been getting used to. Almost a slightly cold and sterile presentation in comparison.
Oli had advised me that the initial presentation might get some getting used to and that the new core/caps etc may take a while to 'open up' etc.


After an hour or so I was getting back into the music, with the drive and toe-tapping ability of the 686 still there in spades, if not a little more.

At this point I switched on the subs. I'd always felt that the system and speakers perform better with the subs but with a caveat. They have to dialed in PERFECTLY, and I mean perfectly. Volume has to be spot on as does the crossover point or it can actually cancel out a lot of the low end performance of the speakers as well as muddying the bass, smearing the midrange which results in the HF sounding a bit shrill and non coherent.


Luckily I've now had enough experience with these subs (REL T3's) and the speakers to know approximately where things should be set. The only change since I had them running last is the upgrades to the 686 so I did have to lower the crossover frequency (presumably the 686 is chucking out some superior bass to the Logan's now, negating the need for the subs to cover that particular frequency) as well as dropping the volume a notch.


Great, the low end was all there and fully extended. The sub's also lifted the Logan's performance a lot closer to where I remember them with the 686. Now we were getting somewhere.


Another hour passed (very easily, always a good sign). I realised I was listening off axis, something I don't often do as I like a perfect stereo image. It didn't matter, it sounded really good a few inches left or right of my usual sweet spot. Great, there must simply be more sound coming from the speakers (and indeed the amplifier, maybe).


Another half hour passed, getting towards midnight now, with a couple of young sprogs that's bedtime and then some for me so I was slightly droopy headed on the sofa, may have been some snoring going on. Anyway, suddenly I was alerted to an absolute ball (not wall as a wall is flat) of sound. Left, right, up, down, forward and back, things were poking out of the usual 'sound-field'. I'd previously managed to get the speakers to extend beyond the room boundaries but only on carefully recorded sound 'effects'. This was now solid coherent parts of the soundstage living outside the room.


I turned it up a tad just to see where the amp might start to run out . . . no chance, I'm still probably not even reaching 3rd gear of the amps capability, it would not break stride or even blink.


I still don't think the amp has fully 'opened up' that could take a good while longer, but it is really coming on song. I believe I'm also getting used to the extra clarity and detail the 686 offers, with the new power supply providing superior drive and allowing the speakers to sing when the volume is up a little bit more. The transparency offers a depth to the soundstage that I certainly have not heard these speakers do before. Sometimes one of the drawbacks of panel speakers and electrostatics in general, can be that they present you with a 'wall of sound', it can be spectacular and sound very 'large' but it can lack depth and overall dimensional presence. Hence my reference to a 'ball' of sound. It grows, it shrinks, sometimes it's small, sometimes it's large, but it's always 3D. Which this 686 is doing very nicely.



Unfortunately at this point I had to go to bed, not least because I was about to wake the entire house up post midnight on a weekday. I've got a very forgiving Mrs but that might be taking the biscuit somewhat, especially with both the subs going full chat . . . .



Can't wait to fire her up again tonight.

Currently a Musical Paradise MP 701 MK2 - www.musicalparadise.ca/store/index.php?route=product/product&product_id=103


Slightly pimped with copper RCA's, OCC wiring, upgraded selector switch and very specifically chosen valves for a certain 'flavour'.


All that is about to change though and no prizes for guessing what is replacing it. I heard the prototype and although initially I was still in two minds as to what it offered vs what the tube preamp brought to the table, the more I listened the more I couldn't deny what the upturn in transparency/clarity did for the system.

It's not the approach for everyone perhaps and it's sacrilege for me, but I'm moving away from having valves anywhere in the system.

I think the warmth/lushness associated with the valves can be achieved and indeed improved upon with SS equipment, but the right equipment it has to be.


I'm only just happening across the right equipment now . . . . 

As has been my mantra up until quite recently. Like you (I think) I always feel something is missing unless you have a nice balance of valve signature feeding SS power to the speakers.

I have surprised myself a little going this route too and of course there will be some adjustment time involved, but ultimately I don't think the clarity levels can be achieved with valves (at least not with preamps hovering around £500.00 as this one is) in such a pertinent position IE the preamp. I'm fast suspecting that the preamp is both the curse and the cure here. By that I mean it's providing a lovely sound BUT also hiding some spacial information which the rest of the system is capable of putting on show. I think the rest of the system has now overtaken the capabilities of the preamp, although a superb preamp it still is for the money. 


I think the case for valves in the phono stage is still a very strong one, highlighted by the sound people are getting from their BB3 and indeed the BBu.

Done right I have no doubt the shortcomings I believe I'm experiencing with my preamp can be overcome but I doubt there's much around to do it for anything near the BT2 price.

Sage words Oli.

Lol, it's all been downhill since 1999 for me...

"You must have drawers absolutely full of valves apart from all the of those you pop into your two phono stages which are at the beginning of the audio chain and have absolutely an influence on what you hear down the rest of the chain. Probably more so than in the pre or power positions."

Well, actually Jim, I haven't got any valves in my drawers. I sold them all. I haven't got a BB3 at the moment, and the replacement BBu i am building is currently only at the populating part of the PCBs. For the first time in about 5 years there isn't a single valve in the house, although i am expecting a delivery of two PS Vane ECC83's and 2 Colomore PCC88s. They are for a BB3 i am making for someone.

I limit the valve use to the Vinyl side generally, and that is because the theoretical maximum of SNR of vinyl is around -70db and the best case scenario for distortion is way below the performance levels of the BBu, in fact it pisses on those figures. The medium is now the limit to measurable performance in my system, not the equipment. Which is the way it should be IMO, and why i am comfortable having a top quality valve phonostage in the system. Only the best ones though 😉

Therefore I don't agree that a good Valve phonostage influences the sound of what i am hearing more than if i had valves in the pre and power position.

The power amp is a particularly critical point in the chain. Unless you are whacking substantial valve amplification on to most speakers, you are likely never going to be running them correctly. A lot of valve amps struggle to drive into the impedance levels required by 3 way floor standers, which can dip in to the 2ohm region. This is my point, IF your valve amp isn't driving the speakers properly, literally anything you are placing before it or after it is being undermined. You cannot, and will not be getting the best from that speaker IF the valve amplifier cannot drive them into the depths.

With the preamp, any time you add gain to a valve preamp you will increase background noise. It's unavoidable. Not much point going for -125db SNR in the DAC if your pre is hovering around -80db! It then literally undoing all of the excellent design work by the DAC manufacturer!

I am not saying that all Valve preamps are that bad, but i invite you to find a valve amp that gets anywhere near to a passive or a PRE90/BT2/Benchmark for measurable performance.

If i wait, i'll be waiting forever because it doesn't exist.

I dont want the equipment to be the limiting factor in my system, so the Pre and Power sections must be better than the medium (source in the case of the DAC) for that to happen. Only with vinyl is it possible to achieve that with valves. Thats why i use SS type devices like the BT2 and a 686 for those parts of the chain. I am not saying other equipment can't be used for this, but these are my choices.

"The reason many folk like valves is because of the influence they have on the sound whether you judge this to be good or bad is personal but don't kid yourself SS amps are a piece of "straight wire with gain". All SS amps also have their own "triats/limits/sonic influence" on everything that passes through them. Dont forget SS circuit design and components also influence hugely how an amp sounds otherwise all SS amps would sound the same.

I have heard some of the so called top SS stuff and yes it can sound invisible, so invisible that it can sound boring and not all top end SS sounds the same either. So they influence the sound too."

If a SS amplifier is boring, then its not TOTL stuff. Simple as that. I have a £100 Class D amp here that absolutely rocks, sounds extremely transparent and is highly detailed. It's well made and has a proper power supply....for £100. I would take this amplifier over most of the high end stuff i have heard. But that proves a point i have been making for years....cost does not equate to performance. When you say "Top SS stuff" what are you referring to? If it's got an exotica name on it, then yeah....it's crap in all likelihood. I was told recently that a £5k used Jeff Rowland amplifier was the "start of the non pussy amps" yet when i looked at the design, it was no better on spec than the £100 Class D i have here.

Real TOTL SS stuff can be bought off the shelf for £3k max. Measurably unbeaten in the commercial sector, at any Foo price.

And yes, before someone says "i use my ears" .... I do to.

My ears are the adjudicators of what i choose to use in my system, but understanding why i seem to be drawn to particular devices has proved very useful in navigating the hifi world. I know my ears! They like vanishing distortion and ultra low SNR. Yes, some stuff i have tried that did this didn't last because it didn't sound good. That comes down to topology and circuit design. The Topping D90 is a prime example. Swap to a R-2R DAC with similar performance levels and it stuck because it sounded right to my ears.

"I was listening to my humble valve / hybrid SS system last night and it sounds extremely transparent and "invisible", you would not know it was there as indeed you have heard and commented yourself. SS gear is never truly invisible in itself and either adds or takes away from the original source material you just never know how much because you have never heard the original source material. Ultimately surely it is best to put together equipment you like the sound of personally and not question if its SS or valve or digital or vinyl because you would never be wrong if you like the sound you are listening to even if it adds a little colour of its own. 😊"

It's not really so "humble" is it Jim lol. Your mono blocks are £1500ish?, the pre is what? £1k? How much on aftermarket valves? Plus i believe you had some mods done some time back? You are on at least £2.5k (- £3k with valves?) of amplification to be fair lol

The Croft stuff is so well priced. You could buy similarly built stuff from Conrad Johnson for £10k and not get the performance that you have in those Crofts. I know that to be true. Coupled with those HECO speakers that should cost at least 3x more than you got them for, you have a system that performs far higher than it's cost suggests.

But lets be honest, your system goals are very different to mine. I would imagine the thought of the physical limits in the vinyl medium and how to ensure the phonostage or preamp isn't limiting it further, have not crossed your mind. Or if they have, they haven't caused you enough concern to go down that rabbit hole? Also, You use MM, which really helps in that area. MM phonostages have the luxury of being quieter due to the lesser gain requirements. If you were using High end MC's, you'd probably notice this a lot more?

As for never hearing the source material, that's not right either. I have been in the studio. I have made recordings and i still have the instruments i made them on. I can fairly accurately still do a "live" comparison and have done on may occasions. The system i have (with 686) is the most uncanny reproduction of what i hear straight out of my guitars. That's all i have to worry about. If it's that close to my guitar, it wont be far of the guitars of others.

"Ultimately surely it is best to put together equipment you like the sound of personally and not question if its SS or valve or digital or vinyl because you would never be wrong if you like the sound you are listening to even if it adds a little colour of its own. "

I think that depends on the individuals system goal. If the end point of the system being built is to provide a particular sound you find pleasing, then yes, mixing and matching devices to obtain a sound you like is absolutely fine and as you say, cannot be wrong for the individual listening to it. That wasn't the goal for mine. It was to build a system that worked as a laboratory type device for developmental and critical listening to phonostages, preamps, DACs, amplifiers and Cartridges. However, in chasing down the performance to do that, i have inadvertently created a system i absolutely love more than any other i have heard.

Thanks Al.

Yeah, I absolutely agree with this.

I agree if you don't like what you're hearing then you're on a hiding to nothing.

But in reality it isn't that simple. You play say five recordings and they all sound wonderful and then recording number 6 it makes a right dog's dinner out of it and you realise that the system is badly flawed somewhere. That's the trouble with 'just listening' to assess the quality. You can't realistically  go through your whole collection before you make the decision to buy.

Then you end up with a system that dictates your choice of music.

Some people will blame this on 'bad recordings' but it isn't.

Excellent post. That's the way I build and listen to my system. I'm not interested in measurements etc. I'll leave that to the engineers 

For me it would highly depend on which genre it couldn't do. If for example it excelled with the 5/6 more so than the one that gets 6/6 'right' the shortcomings could actually be justified.

I know that sort of description is a little non specific but I've always owned things that are more fussy and fiddly and requite more specific working conditions.

More effort yes, but potentially worth it.

Of course ideally it would do everything right, but it ain't easy.

Oh and there are bad recordings, not as many as people think but there are.

My problem is the only sort of music I don't listen to is the sort that sounds good on stuff like Audionote (they're far from being the only one chasing that market).

I call it fake hi-fi. Only impresses with a few recordings, but it is a 'Wow!' sound with those few.