| Vortex |
Hi there,
me and my father are building a passive preamp of the best available quality for a DIY-er, it means, silver cables, very high quality RCA plugs and volume control, input switch selector both from DACT.
Now, we'd like to integrate in this passive preamp an active part, namely the phono preamp, to bring the phono's milivolts to line level.
The phono part will be for MC cartridges only, it means, very low level signal, you know how this is.
I asked my father, quite a professional electro technician, what he would recommend for the phono, to get very high quality sound with no audiophile-like magic and so on.. so just staying on the surface.
He told me, MC signal level is so small, that he wouldn't recommend a tube preamp for it because of the - in this case - relatively high dissipation noise itself - not to mention the strong microphonics at this level.
So he told me, he would build it using FET circuitry. Nearly the same characteristics as triodes but much lower noise, he argued.
The another thing was quite interesting: he told me, since this circuitry would be as small as a box of matches, the best idea would be, to build it into an existing LP, next to the point where the small level input signal comes (from the pickup). Argue was that this way, this low level signal doesn't need to run through longer cable lengths and as such collecting noise. Instead, it would at the end of the tonearm (at the tonearm-base of course) and this way the modified LP would also give the normal line-level signal just like CD players, tape decks, etc.. which signals are much more suitable for transferring them via RCA interconnects into the monoblocks, than the very low level phono (MC) signals.
And of course the 9-12V DC could also be get from the LP's drive system - no need of any separate transformer, which would of course occur in building the whole phono part outside of the LP.
And now, my questions:
1) What do you think about FET amplifying in this case ? (not overall).
2) How could the sound quality be that way. So, FET circuitry built inside the LP, not outside, or not in the "preamp". (It means, no need of extremely-low-voltage interconnect cables).
3) Can a quite audiophile level of amplification be reached this way, let's say, with an Audio Note TT1 LP and a reasonable good MC pickup ?
4) Any disadvantages, you would might consider? The simplicity of such a circuitry would also mean a good point, wouldn't it?
Thank you all! :)
PS: I see another phono preamp topic here, but that one was already decided to be tube-style. This isn't yet. I'm not for tubes. I'm for ultimate sound. ;) Doesn't matter, how. |
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| HDTVman |
Your father's plan is a good one. The reason phono systems are not setup this way all of the time is for marketing reasons, not ultimate audio reproduction.
Putting the phono preamp in the TT it by far the best way to avoid noise picked up in the cabling. Once the noise is mixed with the desired signal your stuck with it.
I have been using FET phono preamps for years, in fact I build FET cascode phono preamps with passive RIAA eq. I think they work very well and contribute no "sound of there own". The type of component used has less to do with the sound than the design of the circuit in my view. If you wanted to use a low noise opamp design I am sure very good results could be gotten that way as well.
For MM carts a tube preamp can be good also but when it comes to MC carts, the noise can be a problem and microphonics will be almost for sure. You can go through lots of tube to find the ones that are less microphonic but they all are to some degree.
Well good luck and have fun.
Later BZ |
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| analog_sa |
| quote: | | I'm for ultimate sound |
but no
| quote: | | audiophile-like magic |
and still using silver cables, expensive RCAs, etc?!
Where do you put the border between audiophile and 'just staying on the surface'?
About
| quote: | | And of course the 9-12V DC could also be get from the LP's drive system - no need of any separate transformer |
you can forget. No high quality MC stage will work with voltage 'stolen' from the TT.
Otherwise your concept is good. FETs are a good way to deal with MC levels. There is the Pacifique design, often discussed on this forum, Erno Borbelly's FET phono pre to give you some ideas.
You can also use a pretty good IC, the INA103 and build the input stage around it. Remarkably low noise but possibly not as good sounding as a discrete phono. |
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| Vortex |
High quality RCA is just because the whole passive preamp (I think, no more preamp, just a volume regulator - input selector box) .. well, this will be made in snow-white piano finish. Just like the two separate 10W Class-A monoblocks.
So optics does matter. That's the point I mean "high-quality RCA plugs". :)
"Silver wiring" -> "no silver wiring"
sorry for the "no", I'm just trying always to type with the least grammatic failures. My German is better, I think ;)
So, no silver of course. I don't think it would improve sound quality much... I'm not a voodoo-fan. :)
Thanks for the kind answers.. we'll try the FETs.
About the LP ... you're right. I think I'll let the transformed low-voltage power cable just lead into the TT1 with some kind of a professional (and cheap!) connector, so the transformer will be outside, but the signal will stay inside. The circuit too, of course.
Nice.
I'll let my father make the circuit diagram soon, you'll see it here if interested. (Probably nothing special... but anyway..)
I hope I'll be satisfied with it.
If you were ... ;) |
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| Vortex |
sreten,
I think we'll somehow manage the shortest route of the uV-signal. Don't know how. Having a look at the pass-labs diagram, it's easy to split (just as every circuit) :) .. so the uV-signal WILL STAY inside, no compromises. :):):)
The rest can be placed outside.
But anyway, I think, even this Pearl could be fitted inside the TT1. Lots of space in there.
It will be quite funny looking at the LP and seeing, that it has 2 transformers and 2 power cords ;)
(LOL) :)
I hope so at least. :) |
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| analog_sa |
| Ok, it's clear then. If you're not pursuing ultimate qualty i'd really recommend the INA103 followed by passive riaa and output opamp. It can be set to work with any MM or MC carts down to 100uV; it sounds pretty good (i think i used AD845 at the time) and is not too demanding towards the PS. Best of all it will easily fit in a cigarette pack. |
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| Vortex |
what to consider just in theory, if I pursuing the ultimate for an MC ?
:)
I don't think, I'll want to make several ones each week or month or year..
So the finished one must have to be able to do it's best for my ears for years long..
(Do I want too much at once?)
:confused: |
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| SY |
If you want to get ultraengineering-geeky, put the first gain stage right in the headshell, phantom-powered. This way, the voltages run down the wires are considerably higher and more noise-resistant.
I worked on a design like that with Murray Zeligman about 25 years ago, using 2N6550 FETs. We drilled two holes in the headshell to press-fit the FETs so the mass change wasn't too drastic. It was pretty cool, though truly overkill. I wonder if a tube implementation could work... |
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| fdegrove |
Hi,
| quote: | | I wonder if a tube implementation could work... |
Pencil tubes?
BTW, if I am not mistaken Clearaudio once had a MC cartridge with built in headamp.
Cheers,;) |
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| Vortex |
| quote: | | It was pretty cool, though truly overkill. |
What does it mean? :) (overkill... ?)
(sorry my english isn't very good) |
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| SY |
| quote: | Originally posted by Vortex
What does it mean? :) (overkill... ?)
(sorry my english isn't very good) |
Better than my Magyar, which consists of one word: Magyar.
"Overkill" means using something ridiculously overqualified for a task. An alternative idiom is "killing a fly with a sledgehammer." This is quite common in audiophilia where we design preamps that can swing 100V, power amplifiers that can pass video signals, and speaker wires that can handle the SNCF power grid. |
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| sreten |
| quote: | Originally posted by Vortex
3) Can a quite audiophile level of amplification be reached this way, let's say, with an Audio Note TT1 LP and a reasonable good MC pickup ?
|
IMO the Pearl will be good enough where-ever you place it.
IMO ultimate MC solutions are pointless to discuss for this.
And yes, audiophile quality can be achieved, unless your
definition of audiophile quality is simply based on being
ludicrously expensive.
:) sreten. |
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| Vortex |
oh, nice :)
I got it.
Nice to write on this diyaudio.com forum.. kind, helpful people here.
Not always the one and other audiophile "gurus" who always try to suggest us, which "magic" would work and which not, and even if there're ABSOLUTELY NO SCIENTIFIC MEASUREMENTS available for what they do, they "hear" the difference..
I like the objectivity of this forum.
Thanks a lot :)
Köszönöm ;) |
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| Vortex |
| quote: | | unless your definition of audiophile quality is simply based on being ludicrously expensive. |
Oh, no way.
Until reaching a level, I think, audiophiles and high-end people can argue well, their things they believe in, work actually, perhaps not always worth the money, but works.
But after a certain margin, there are such kind of high-end folks here in Hungary, who try to explain thing, that CANNOT BE explained with modern physics - which is the base of everything regarding sound, electricity and whatever all that (including quantum-physics, electromagnetic fields etc etc .)
So just to tell you an example, on a forum here in Hungary I opened a topic regarding suspensions of CD players, accuracy, EAC (Exact Audio Copy) - grabbed Audio CD-s (onto PC), etc...
The point, where I gave up, was, where they STATED (!) the following:
If you place the CD-Player on a wooden stuff (pad, sand-off...), it's sound will be more softer. If you place it onto a pad made of some kind of rock or metal, it's sound will be harder, more accurate, but less life.
And THIS PERSON said in his same posting, that there were measurements regarding the bit-flow, directly before the DAC chip, but also directly after the laser mechanics. And regardless of material quality or "resonance - they said", the bit-flows were COMPLETELY identical !!!
And after that all, I should believe, they still hear some difference between the pads, the materials, they put their CD-player onto it.
Oh God..
"Now, the CD-player is on this box, do you hear??? ... Okay. Now, I put it onto the ground. No box under it. Well, how does it sound? A bit harder, right, dude?"
:):):)
Yeeah dude, because in the 2nd case you put the box into the corner and according to it's size, it can quite reasonably influence the acoustics of the whole room.
:)
So, that's it. The rest with the pad's are magic, I think. And at this point, I really begin to hate them. Not because of their system - I also could afford it - but because they can be fooled by nearly anybody who just claims a system would with this stuff sound different. :whazzat:
On the other hand, acoustics is just like a tree, in my mind. Until a level, everybody has nearly the same hearing. (This is the "base" of the tree). Everybody can hear the difference between a Sharp Boombox and a well performing Rotel amp. But if we go further, I don't allow anybody to say, this high-end system "X" sounds much better, than "Y", I heard it at the new CES 2004 and it was AMAZING ...
And why ? Because our ears are biologically different. Some of us have higher sensitivity of highs than others, and the same of course with bass, midrange, phase, x-order harmonics, etc.
So everybody is just a leaf on the top... one other leaf's need cannot always cover the needs of the original one.
(Sorry I've gone a bit metaphoric or what) :bigeyes:
------
So it's the way I think about the word "audiophile" or "high-end".
Summa summarum: lot of stuff in electronics has a PRO and CONTRA. Where clearly not, we shall do our best to achieve it. Where a compromise cannot be avoided, we shall try to fit it to the listener's ears. Only if it couldn't be done better (still for each listener), I will say: "wow, that sounds maaan..." - and I'll say, it's quite audiophile-grade. Else never. (I know of course the "parameters" of my ears, so if I cannot do something in order to meet my ear's needs, a million dollar system wouldn't do it for me either. Everything's based on physics - and each part can be bought or made of ultra-high quality by ourselves, too).
There is of course a limit, which each of us has to set in order to NOT looking for the ultimate in his whole life. We're for enjoying music on this Earth. Listening is just the way it's functioning. Nothing more. |
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| Vortex |
Wow!
Interesting site for all non-commercial DIYers! Check out the root of this site, what they do, who they are...
I think, this will be our preamp. I'll report, when I'm finished :)
http://www.borbelyaudio.com/index32.htm |
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| analog_sa |
| quote: | | If you place the CD-Player on a wooden stuff (pad, sand-off...), it's sound will be more softer. If you place it onto a pad made of some kind of rock or metal, it's sound will be harder, more accurate, but less life. |
Have you ever wondered what would it feel like if you listened for yourself? Many are scared to try but it only hurts the first time :) |
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| Vortex |
| quote: | | And regardless of material quality or "resonance - they said", the bit-flows were COMPLETELY identical |
Explain the rest.
Then I believe.
:) |
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| fdegrove |
Hi,
The rest is mainly acoustic feedback IMHO.
Cheers,;) |
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| sreten |
Have you considered sometimes less is more ?
That is sometimes the "best" isn't necessarily so.
IMO the use of split supplies, DC servos and full
complementary topology is missing the point.
(In the Borbely design)
Fully balanced topology reduces even order
distortion leaving odd order distortion untouched.
In low level class A circuitry distortion is not really
a problem and IMO reducing even order is pointless.
IMO with the turntable and medium quality medium output
moving coil cartridge you appear to be considering I really
can't see any good reason the Borbely design would be
better than the Pearl design, and I can see several reasons
why its more "hifi" approach might not suit the application.
Another fundamental difference between the
two designs is active feedback for Bass EQ in
the Borbely against passive in the Pearl.
Not having heard or built either design, and personally
completely disagreeing with the garbage spouted about
FETs versus Bipolars, the Borbely design is too "hifi" for
me, I'd like something simpler and more elegant.
:) sreten. |
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| Vortex |
well just considering it's price - as a kit still extremely expensive - I really don't know.
I think I'll bulit both of them, the Pearl and the Borbely.
Better said: I'll begin with the Borbely one. We'll test it in high-end environment, which satisfied me quite well (a dream for my ears).. if it will produce about the same quality, like the factory-built one, or even better, I'll stick to it and forget the Pearl.
If not, I'll build the Pearl too.
I also have some another schematics of preamps from top level high-end manufacturers, perhaps I'll extract the phono amplifier circuit from one of them and try it. But I actually don't really think, it will be needed. |
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| analog_sa |
| quote: | | And regardless of material quality or "resonance - they said", the bit-flows were COMPLETELY identical |
You haven't heard of jitter? Of course, as Frank says mechanical vibration in the analogue parts may be also responsible. |
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| KlausB |
Hi Vortex| quote: | | What do you think about FET amplifying in this case ? (not overall). |
A jFET input stage is a very good solution for MC systems IMHO
| quote: | | How could the sound quality be that way. So, FET circuitry built inside the LP, not outside, or not in the "preamp". (It means, no need of extremely-low-voltage interconnect cables). |
The integration of the RIAA preamp or at least a pre-pre seems to be a good and practicable idea. ThoughI did not do this myself so far, I remember that turntables with integrated MC preamps and accumulator based power supplies were presented at the High-End in Frankfurt last year and they sounded good. Sorry I forgot the brand I think they came from Scandinavia.
| quote: | | Can a quite audiophile level of amplification be reached this way, let's say, with an Audio Note TT1 LP and a reasonable good MC pickup |
Definitely Yes. With a high gm jFETs such as the 2Sk369 you can easily achieve an amplification of 100.
| quote: | | Any disadvantages, you would might consider? The simplicity of such a circuitry would also mean a good point, wouldn't it? |
I would strongly recommend a separate power supply.
I experimented with MC preamps for a while until I found my personal solution. I have it on my website.
www.klaus-boening.de
Cheers & good luck
KlausB |
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| Vortex |
Danke Klaus,
ich gucke mal an. :) |
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| Posthorn |
| If you like to stay on tubes take a look at Application notes from Svetlana EF 86 or a bit more exotic but inexpensive c3m (German post tube) |
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| Vortex |
It doesn't matter, tubes, or not...
it should sound absolutely compromiseless :)
I'm thinking of two Borbely designs, one is the all-fet phono preamp but it needs to calculate the parts (not an easy job), the other is one which is a JFET-inputted tube preamp for MM/MC both usable, with numbers, everything, so we just have to buy the parts and solder them together as the circuit schematics say.
I'm still interested in the all-fet solution.
The fet-tube "combo" preamp of him was published by a magazine (I cannot remember it's name, perhaps somebody of you can give a link to it) .. |
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| GaryB |
| quote: | | The fet-tube "combo" preamp of him was published by a magazine (I cannot remember it's name, perhaps somebody of you can give a link to it) .. |
It was published by the now defunct Glass Audio.
Borbely has a copy of the article on his website:
http://www.borbelyaudio.com/phono.pdf
By the way, I agree that Borbely's equipment is top notch. I've built quite a bit of it including an early version of his fet phono stage and his all fet line stage. I'm still using the line stage but I've since retired the phono stage and moved on to tubes, with an FET/tube cascode as the front end.
I'm still experimenting with phono stages and recently finished a Pass Xono phono stage. It sounds quite promising but I still need to tweak it to sound the way I like. I haven't yet retired the tube stage, so maybe theres a message there.
---Gary |
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| Vortex |
| quote: | | I've built quite a bit of it including an early version of his fet phono stage... |
Could you please just eMail me the schematics with the exact parts list and values ?
I'd have a look at it. I'm building his preamp published in the former Glass Audio magazine - perhaps I can compare the two, which suits me better in sound.
If you won't, no problem.
Thanks :) |
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| GaryB |
| quote: | | Could you please just eMail me the schematics with the exact parts list and values ? |
Well I don't have a soft copy, but it was published in Audio Amateur, issue Two / 1991.
---Gary |
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