| halojoy |
The Analog Addicts Phono Preamp
By Thorsten Loesch
It is also called "El Cheapo" (low price)
Hope noone will hang me, if I provide a schematic.
I have changed the size a bit, to fit DiyAudio.com.
Best is to read the whole article, that Thorsten Loesch have written.
See Link in post above!
/halo |
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| Mad_K |
BB OPA 637 is not 'cheapo in my book...
(But the design is 'cheapo in comparison to other Loesch riaa designs) |
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| Optical |
i'll be keen to hear what you think of it when its done!
Ive been meaning to build all of these simple phono circuits and do a comparison of each to mark the differences for future reference.. |
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| lohk |
Have you ever ordered an OPA627/637 ?
Must be one of the most expensive opamps available...
Klaus |
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| lohk |
| and please ask Kuei Yang Wang about that design |
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| Kuei Yang Wang |
Hi,
| quote: | | and please ask Kuei Yang Wang about that design |
Speak of the Evil one....
Not much to say about this thing really. I started fafelling about with Selfs "Precision Preamp" Phonocircuit. It sounded BAD. So I messed about a lot and tried many things.
Doing this circuit with lead acid battery power, OPA637A and a 10k Pot (later an unusual active linestage with a FET Buffered LM6181 and Volume control with a 1k Shunt Pot and a 150 Ohm output resistor) sounded rather decent for solid state. Acrylic case BTW, mixture of hardwiring and PCB.
Still, I like valves and transformers better. Butafter you put don the long green for a pair of S&B TX-103 MC Steups and the same amount for the LCR RIAA EQ Module and shelled out the green for a PSU using 8pcs 10H chokes and 6pcs 120uF Film Capacitors you appreciate just how good this little job is for the money, how simple to build.
And the price of a pair of OPA637 plus a pair of 2SK147 and four 12V/2.1AH Lead acid batteries is not THAT outrageous. Hell, my current RIAA Stage clocks in at near £ 1,000 in materials uses near unobtanium NOS Valves and it is NOT ten times better than the little ugly duckling solid state stepchild. In wood, netal and all it looks a lot better though.
Sayonara |
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| Mad_K |
| quote: | Originally posted by lohk
Have you ever ordered an OPA627/637 ?
Must be one of the most expensive opamps available...
Klaus |
I have them in a little box, along with some other goodies TI was kind enough to send me :D
And, yes I have yet to see an opamp with a higher price... |
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| Mad_K |
As I've changed the circuit somewhat I'm not allowed to say it's Thorsten's, but I think it is close enough.
Changes:
1. Only MM stage.
2. Not rechargeable batteries.
3. None of the specified components (brands) are used, except for the OPA637BP.
3. Supply filtering changed: Elna RJH 1000uF + 100nF Rifa MMK.
4. RIAA caps are WIMA FKP2, 2,5% but matched to exact value.
5. Outputcaps are Elna RJH 330uf (arranged as descibed) bypassed with 0,47uF SCR.
So, here comes the pics; board: |
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| Mad_K |
Hardwired my usual way. You can see that it was put together with a little haste. I know this is not the best way to build a circuit like this (PCB with ground-plane and p2p combo should be best), but it's my way..
backside: |
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| Mad_K |
| Here it is in it's lovely box and Duracell PSU: |
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| Mad_K |
| A little closer on the circuit: |
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| Mad_K |
| And, finally in it's place (without the top-plate), playing Mark Knopler... |
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| Mad_K |
Maybe, you are wondering about the sound?
The answer is I don't really know yet, but it seems very promising; neutral, especially in the critical midband. A little relaxed, dark-sounding maybe. Very precise and accurate. Bass is solid, and treble is excellent. I've tried (and listened to) some of the other simple RIAA pre's, but always found something that I didn't like about them. Noise is as low as one can expect. I have to turn the volume all the way up and put my ear near the speaker to hear anything. Surface noise is also very low. Previously, I have always had a problem with static jumping through when changing records. Somehow it's gone now...?
This is the one for me, thank you very much :D
BTW, it worked very well with the OPA604 also ;) |
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| Mad_K |
| Oups! Forgot the "whole picture" :) |
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| Mad_K |
| That seemed like a nice discussion, but I couldn't find the circuit :confused: |
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| Kuei Yang Wang |
Hi,
Nice job. And good to hear you like the results. Some comments on sound later....
| quote: | As I've changed the circuit somewhat I'm not allowed to say it's Thorsten's, but I think it is close enough.
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As you say, it's close enough. You can call it "Thorstens" if you like, though I think it is actually Mad_k's RIAA Pre and a nice one too.
Using Alcali batteries is still a battery supply, it qualifies too...
[QUOTE][B]
3. Supply filtering changed: Elna RJH 1000uF + 100nF Rifa MMK.[QUOTE][B]
Consider adding more bypass capacitors. Try especially a few nF Silver Mica (say 2.2nF) and a few nF Styroflex or Tinfoil/Polystyrene (say 3.6nF).
[QUOTE][B]
4. RIAA caps are WIMA FKP2, 2,5% but matched to exact value.[QUOTE][B]
This will be part of the "darkness". Try Silver Mica EQ Cap's instead. They will open up the sound....
[QUOTE][B]
5. Outputcaps are Elna RJH 330uf (arranged as descibed) bypassed with 0,47uF SCR.[QUOTE][B]
See above. Bypass a little more. Add a Foil & Film Bypass and/or the Styroflex/silver mica combo.
Sayonara |
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| Mad_K |
Thanks for your comments Kuei Yang Wang!
As I am (was?) in the progress of testing different MM phono-pre's I did them all with the same type of components (more or less). I think you are right about the WIMA's, but I kind of like it..
Later, I will build this circuit one more time with different (better) components, and take your advices with me, and maybe implement the MC-part also.
Now it's time to do some serious listening ;) |
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| Chris |
Congratulations !!!!!!!!!!!!!:D
Probably sounds the way it looks...........
And that would be just great !
(PS how about some Mark K + madK riia and some coffe tomorrow?) |
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| Mad_K |
Thanks Chris!
More impressions: Sound is controlled, with a unusually accurate soundstage. It sure manages to bring out a lot of details from my records -listening to "Röyksopp" was almost confusing, 'cause I'd newer heard all those weird little clues/mixes before (not even from my 2K$ CDP).
(Kfi i morgen kan bli vanskelig) |
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| Kuei Yang Wang |
Hi,
| quote: |
More impressions: Sound is controlled, with a unusually accurate soundstage. It sure manages to bring out a lot of details from my records -listening to "Röyksopp" was almost confusing, 'cause I'd newer heard all those weird little clues/mixes before
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Yes. This is very much and always has been my "house sound". Detail without fatigue. It has probably something to do with english being my third language and me always having problems following difficult lyrics. Loads of detail hels intelligibility. Loads of detail often hurts my ears in commercial designs. It's not the easiest job to achieve balance. You can kill it quite easily too in this Phono, just try some really high capacitance interconnects....
Sayonara |
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| Mad_K |
It is definately not fatiguing!
Kuei Yang Wang, I think we have the same preference:
DETAIL WITHOUT FATIGUE.
How nicely put.
It think it's very natural sounding. The treble is very transparent, with lots of info, but never hard/cold/over-anaytical.
Funny you should mention it, because one of the first things I noticed was that it was real easy to follw the lyrics...
You mean the output interconnects, yes?
-Not to worry: 7.6pF/ft :) |
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| Kuei Yang Wang |
Hi,
| quote: |
You mean the output interconnects, yes?
-Not to worry: 7.6pF/ft :) |
Well, that is splendid. I like low capacitance interconnects.
BTW, my E810F Valve/LCR EQ based Phonostage is much better still, but has a entry pricetag in parts that is lethal.... ;-)
Sayonara |
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| Mad_K |
| quote: | Originally posted by Kuei Yang Wang
Hi,
Well, that is splendid. I like low capacitance interconnects.
BTW, my E810F Valve/LCR EQ based Phonostage is much better still, but has a entry pricetag in parts that is lethal.... ;-)
Sayonara |
I'm shure; and it would most certainly KILL me ;)
For now, I'm just enjoing my new ultra-simple-cheapo phono-amp so very much. (I'm on a very tight budget these days):( |
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| Mad_K |
:o :o :o :o :o :o :o
Aaaahaaaaaa!
Thorsten Loesch = Kuei Yang Wang
Now I get it!
Man, if I could feel more stupid than right now...
(From now on, I'll always check people's profiles)
Part of the explanation is that I discovered your "The Analog Addicts Phono Preamp" by googling the web, and found this: http://www.users.nac.net/markowitzgd/phonopre.html
I think I have seen thunderstoneaudio before once, but only briefly (was searching for something else).
Now, if I could be so bold to ask about the story behind your username?
And, thank you very much for your excellent phono-pre design. |
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| Elso Kwak |
| quote: | Originally posted by Mad_K
That seemed like a nice discussion, but I couldn't find the circuit :confused: |
Hi Mad_K,
Please have a look here:
http://www.analog.com/UploadedFiles...0917MAT04_d.pdf
(Figure 6, page 9, Low Noise, High speed Instrumentation Amplifier)
:cool: |
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| Mad_K |
| Thank you, there X something about this circuit.... |
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| halojoy |
Surprise for you, Mad_K
most of us others, who knew,
thought that you knew also ;) ;)
-----------
Thorsten is surely glad if anyone can use his designs
and feel happy about them.
He puts a lot of hard thinking and work into so many things.
sometimes it gives some tasteful fruits, too
to us people
/halojoy - :cool: also known as "gromanswe" (260 posts) here at diyaudio
and "groman" at AudioAsylum (700 posts) :cool:
##################################################################
IMAGE: my uncle's illegal building (not authorized by swedish departments)
in the swedish mountain woods, small birch-trees |
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| Mad_K |
| quote: | Originally posted by halojoy
....
most of us others, who knew,
thought that you knew also ;) ;)
.....
/halojoy - :cool: also known as "gromanswe" (260 posts) here at diyaudio
and "groman" at AudioAsylum (700 posts) :cool:
|
I figured this, and I also had the feeling that "halojoy", "groman" and "gromanswe" where the same person.. (From your unique writing style).
Nice little cabin he's got there! ;) |
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| Kuei Yang Wang |
Hi,
| quote: |
Thorsten Loesch = Kuei Yang Wang
Now, if I could be so bold to ask about the story behind your username?
|
Yup, you grocked it right...
Kuei Yang Wang is one of the possible phonetical renderings of Kaiyanwang, a charater from the Anime' Series 3X3 Eyes also known as Shiva. He was a King of the Ancient Sanjian race (the Triclops for their third eye located in their forehead) and made a pact with the powers of darkness to gain domination of all the worlds (including this one) and in the process cheerfully butchered his own people.
He was stopped of course and put into an eternal state of not quite death and is awaiting his reawakening by his minions of the shadow world. (this does ring a faint bell of the Xenu guy that Ron Hubbard Dude babbled of in the OT levels of COS...).
Well, a pretty mean dude and unsavoury fellow, just right for my own alter ego, if I do not want to be nice and helpfull....
More 3X3 eyes here:
Non-anime watchers review of anime - 3x3 Eyes
Anime-archive.net .. 3x3 Eyes
Sayonara |
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| Mad_K |
| quote: | Originally posted by Kuei Yang Wang
Kuei Yang Wang is one of the possible phonetical renderings of Kaiyanwang, a charater from the Anime' Series 3X3 Eyes also known as Shiva. |
After googling a little, I kind of suspected something like that...
Now that the secret is out ;) it's actually kind of funny.. I gather you are a big anime fan (I think a saw a couple of movies in the pictures of "your temple").
Oh, gotta go to check out what Ben Harper is moaning about... :cannotbe: |
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| jag |
| quote: | Originally posted by Kuei Yang Wang
Kuei Yang Wang is one of the possible phonetical renderings of Kaiyanwang, a charater from the Anime' Series 3X3 Eyes also known as Shiva. |
There is a lot of misconception about Shiva in the popular (Western) culture. Shiva is never evil! Shiva is part of the trinity of Gods - Brahma (Creator), Vishnu (Elan vital), and Shiva (Destroyer). Destruction is NOT evil and is part of the natural cycle: Creation - Expansion - Destruction (Oscillating universe in endless expansion-contraction cycle). |
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| Kuei Yang Wang |
Hi,
| quote: |
There is a lot of misconception about Shiva in the popular (Western) culture. Shiva is never evil! Shiva is part of the trinity of Gods - Brahma (Creator), Vishnu (Elan vital), and Shiva (Destroyer). Destruction is NOT evil and is part of the natural cycle: Creation - Expansion - Destruction (Oscillating universe in endless expansion-contraction cycle). |
I am quite familiar with Shiva as the actual facette of divinity. However, my comments are strictly in the Context of the Japanese Manga (a Cartoon Magazine) and Anime (Animated Cartoons) Sazan Eyes, where the japanese Author took literary licence to show a different portrail...
Sayonara |
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| Hamish |
Kuei Yang Wang,
i just finished this phono-pre, in a configuration that would have you shaking your head in disgrace:bigeyes: . Poor quality caps, regulated power supply, all the evil things:bawling: . I knocked it up on a VERY tight budget. The first time i tried it, i had a hard-core audiophile with me, and he left cursing. All the money he had spent on expensive equipment did not even come close to my preamp running through a gainclone:clown: . Kudos to you and the excellent schematic. I think i'll try and get the proper parts now seeing how good this is.
Thanks again.
:) :) :) :) |
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| halojoy |
| quote: | Originally posted by Hamish
Kuei Yang Wang,
i just finished this phono-pre, in a configuration that would have you shaking your head in disgrace:bigeyes: . Poor quality caps, regulated power supply, all the evil things:bawling: . I knocked it up on a VERY tight budget. The first time i tried it, i had a hard-core audiophile with me, and he left cursing. All the money he had spent on expensive equipment did not even come close to my preamp running through a gainclone:clown: . Kudos to you and the excellent schematic. I think i'll try and get the proper parts now seeing how good this is.
Thanks again.
:) :) :) :) |
Audiophiles
are either made of money
or
they do spend all they have on "snake oil"
leaving nothing for food, clothing and normal life
and all audiophiles
are very easily fooled by listening reviews
/halo - does not believe his ears more than his measurments |
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| Hamish |
| it does have a beautiful, honest sound though. much better than anything i have heard commercially available (and i have been giving high-end stores a real workout while i have been building my first system. i don't think they like me much now. i'll HAVE to build it myself, as i don't think they want to do business with me). |
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| carlosfm |
Hi,
There's no doubt that this has to play well.
Thorsten knows what he's doing, I did exchange some e-mails with him once.
I have my oppinion about the best op-amps in the world, each one in it's own application:
- For CD-players: OPA627
- For phono pre-amps: OPA637
That's what I use, after many op-amp tests.:nod: |
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| Mad_K |
I'm enjoying them every day!
Thanks Thorsten:nod: |
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| peranders |
| quote: | Originally posted by carlosfm
- For CD-players: OPA627
- For phono pre-amps: OPA637
That's what I use, after many op-amp tests.:nod: |
AD8610 not so bad either...and much cheaper. |
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| rookster |
Has anyone implemented the MC section of this circuit? Most have done the MM, but no-one mentions the MC section.
I have a 0.4mV MC cartridge and I need the gain and loading of the MC section.
Does anyone have any experience or thoughts on the sound of this section? |
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| peranders |
0.4 mV is just 6-10 dB weaker than normal. I think you can try to increase the gain a bit. If it's too noisy then you may add an another stage.
Opamps with < 4 nV /Hz will do the jobb. AD797, LT1028, LT1115, etc. OPA637 is also probably OK. |
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| rookster |
Is the 30 Ohm 10Henry inductor required for the MC section. Am I reading the circuit wrong? This inductor would be HUGE.
Can anybody clarify? |
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| peranders |
10H seems big but you could ask Torsten himself, ID here http://www.diyaudio.com/forums/memb...nfo&userid=3984
One thing for sure you will need very quite supply voltage for the first JFET stage. You could without any harm increase the 2200 µF to 10 mF or more and exclude the inductor. You could also increase the resistance but the amp will get a longer start time. I can imagine up to at least 220 ohms would work. |
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| Kuei Yang Wang |
Koinichiwa,
| quote: | Originally posted by rookster
Is the 30 Ohm 10Henry inductor required for the MC section. Am I reading the circuit wrong? This inductor would be HUGE.
|
You are reading the Circuit right. :nod:
Yes, the Inductor is 10 H / 30 Ohm / 10mA. :nod:
There is only one thing that you are wrong about. The inductor is not HUGE, it is quite small. :scratch:
It is an item from Steinmusic in Germany. :devilr:
Steinmusic Chokes
Does that help? :confused:
Sayonara |
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| analog_sa |
Rookster
I have been using a similar front end for MC. Tried both 2sk147 and 2sk170 and settled for two parallel 2sk170GR as a compromise between resolution, noise and bass. For power i use the contents of 4 Nokia NiMeH rechargable batteries connected in series, i doubt if a much better sounding solution exists and of course it will sound better than sharing a common supply with the riaa section. Plus you won't need the inductor.
What really bothers me about El-cheapo are the humongous output coupling caps, surely they needn't be that big? If i had to build this exclusively for MC i'd check what's the output offset is like and if need be would periodically readjust it just to get rid of the elcos.
cheers
peter |
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| Kuei Yang Wang |
Koinichiwa,
| quote: | Originally posted by analog_sa
What really bothers me about El-cheapo are the humongous output coupling caps, surely they needn't be that big? If i had to build this exclusively for MC i'd check what's the output offset is like and if need be would periodically readjust it just to get rid of the elcos.
|
There is good sense in all of this. First, I have removed the DC blocking capacitor inside the negative feedback loop. This causes a lot of offset even with low offset, J-Fet input Op-Amp's. That is due to the very high DC gain of the circuit. Up to 1V offset is not unusual even with OPA637's.
Of course, you could use some for of external Offset adjustment or a DC servo. I never got either of these options to sound as good as an output capacitor with a suitable bypass combo as shown.
You CAN leave off the big electrolytic capacitors completely if your load will not be any lower than around 40kOhm, as I wrote in the text, which you clearly not bothered to read. By using very oversized audio grade (Elna Starget or Silmic) the influence of these on the sound is minimal as they in effect "bypass" the 2u2 Film Coupling Capacitor at low frequencies. To have a low sonic foot print you need these capacitors back-2-back and biased from the negative rail, plus very large values.
I have tested this whole circuit extensively and tried pretty much all options. For reliability (no DC on output) and smallest sonic footprint I found exactly the solution you dislike so much to be sonically most transparent.
I will still say that this circuit is not the final word for Phonostages, but in the context of invested materiels and costs vs. performance it is very good, IF BUILD AS DIRECTED, including observing the general passive parts quality.
Sayonara |
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| peranders |
| quote: | Originally posted by Kuei Yang Wang
Of course, you could use some for of external Offset adjustment or a DC servo. I never got either of these options to sound as good as an output capacitor with a suitable bypass combo as shown. |
Thorsten, have you checked my DC servo in my QSXM3 phono amp?
The servo can be seen in the datasheet of LT1115. See page 10 in the datasheet. If this circuit is to be used you have to investigate how OPA637 is built inside. When you have got everything right this is a cool way to connect a DC-servo.
The servo in my amp works really nicely. |
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| Kuei Yang Wang |
Koinichiwa,
| quote: | Originally posted by peranders
Thorsten, have you checked my DC servo in my QSXM3 phono amp?
|
No, it is the first time I noticed that. But I tried a good quality cermet offset correction pot and even that made the sound worse by more than the output capacitors do.
In the end you are still injecting a signal into the circuit. You have chosen a different junction but it is still the same story. Also, it is I think not readily applicable to the OPA637. I'd have to see the LT1028 schematic.
All first order servos I have tried where clearly audible, even when the "pull" range was minimised and audibly worse than a simple output coupling capacitor combo. I had little luck with 2nd or 3rd order servos, they tend to be, shall we say, tempramental (predictably so, look at the bode plot).
Hence the output coupling combo as it stands. These days I use a MKP of a few uF, a KP of 0.47uF (usually largerst value avialable) plus a few nF each of Styrene and Silver Mica.
Sayonara |
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| Kuei Yang Wang |
Elso,
| quote: | Originally posted by Elso Kwak
As time goes by, we seem to agree on more and more things!
|
Hardly as time goes by. Most of the work on the AA Phono was done in 1996/97, so is 6 - 7 Years old. The file creation date on the Graphics for this article on my Disk puts them at Feb 1998. This is anchient stuff for me for me at least.
So we have agreed for a very long time, except you did not know... :devily:
Sayonara |
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| peranders |
| quote: | Originally posted by Kuei Yang Wang
In the end you are still injecting a signal into the circuit. You have chosen a different junction but it is still the same story. Also, it is I think not readily applicable to the OPA637. I'd have to see the LT1028 schematic. |
It remains to be seen if it's possible to fiddle with the offset trim pins of the OPA637 but I think it's impossible to use trimpots with so high DC gain.
If you check closely I have used a low noise OP07, made it slow, together with an extra filter so not very much of the signal passes through the servo backwards. |
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| Kuei Yang Wang |
Koinichiwa,
| quote: | Originally posted by peranders
It remains to be seen if it's possible to fiddle with the offset trim pins of the OPA637 but I think it's impossible to use trimpots with so high DC gain.
|
Well, I suspect you CAN find a way, if neccesary with added current mirrors and stuff for level shifting. My original point remains that this does not remove the servo any more from the "signal path" (I hate that word) as feeding via a voltage divider into the "foot" of the feedback loop does.
Trimpots do work, but you need a low value, high quality pot and large value range limiting resistors. Use low tempco and the thing is even fairly stable with temperature. But with as high a DC gain I figured "Belts & Braces".
| quote: | Originally posted by peranders
If you check closely I have used a low noise OP07,
|
Very poor AC performance. I found the best DC servo for the OPA637 is an OPA627 but it is more expensive and sounds worse than the output capacitor combo.
I wish people would loose their paranoid fear of Capacitors or Transformers "in the signalpath". By avoiding a component in one place you only bring two or three in through the backdoor.
Like those "DC Coupled" Valve Amplifiers that proudly proclaim "no capacitors in the signal path", excepting of course the cathode bypass electrolytics and PSU electrolytics that could have been kept out of the SIGNAL CURRENT LOOP by using one good quality coupling capacitor, choke anode loading and fixed bias....
Anyway, you may wish to actually compare the two solution. Not in theory but in application. You may be surprised....
I started with Self's circuit from EWW with a DC blocker in the NFB Loop. Awful. Changed Op-Amp's, still awful. Increased the feedback loop impedance and used a film DC blocker, much better. Shifted the Cap from the feedbacl loop to the output, MUCH better, tried servos for about halve a year but always put the coupling caps back.
Go figger. Maybe I like plain straightforward capacitor distortion better than having amplified by the servo and reamplified by the Amplifier. Maybe I'm deaf.
Sayonara |
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| analog_sa |
I fully agree about the servos. The offset pots otoh have worked much better for me than couling caps. Of course one needs to be sufficiently neurotic to periodically (daily?) adjust the offset but for me that's part of the fun. It makes the listening experience that more special. And you can forget connecting carts directly, as their impedance will influence the offset too :) The topology i used was significantly different using split passive riaa and therefore 3 offset pots.
Paranoid fears about caps? We all have different sound idiosyncrasies (oops, meant priorities) and that's why a single solution doesn't fit all.
cheers
peter |
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| peranders |
| quote: | Originally posted by Kuei Yang Wang
Very poor AC performance. I found the best DC servo for the OPA637 is an OPA627 but it is more expensive and sounds worse than the output capacitor combo. |
OP07 is slow and made even slower (intergrator) and the purpose of that is just that I want DC-signals to pass or only low freuency signals. There is absolute no need for a high speed opamp in a 1-10 Hz DC servo. You have lots and lots of feedback left in the opamp.
One another advantage of a slow opamp is that you can be more sure of no oscillations. |
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| jcarr |
At least for discrete semiconductor circuits, I find that a DC servo is _by_far_ a better-sounding solution than an output capacitor.
But this is with the caveat that the servo circuit is intelligently designed and well-implemented. A poorly designed and implemented DC servo will definitely have an adverse effect on the sound.
If anyone decides to go with a DC servo, they should be prepared to invest a major effort in designing the circuit and board layout. If this is not feasible, or you do not have confidence in your design abilities, I recommend staying with an output capacitor. Simpler and easier - much less to go wrong with it.
For further study, I suggest reading AN232 from Analog Devices, authored by Walter Jung. Even if you don't use any of the methods proposed in the application note, it should give you some food for thought.
hth, jonathan carr |
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| rookster |
Thank you Kuei Yang Wang/Thorsten and analog sa and others for your responses and lively discussions.
analog sa/Peter,
apart from the slight change to the 2sk170GR and the power supply, have you altered much in the MC circuit? Have you had any issues with noise? I will be utilising an AT OC9 cartridge with an RB300 arm on a Rega Planar 3 (about 10 years old).
Kuei Yang Wang,
I am very inexperienced in the area of electrical circuits, but why is the 10H inductor/choke needed? I thought it was a filter, but the circuit is already running of a DC supply anyway. Thankyou for the details on the inductors, but I feel the cost and logistics of ordering 2 of these from Germay to Australia, would make it quite a hassle. Can i substitue something else? Any ideas? If this is the best option, then I will implement it. |
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| analog_sa |
Rookster
As i mentioned previously the number of parallel FETs is a compromise between noise, resolution and bass. A single device sounds the most resolved to my ears but the noise with a 100uV source is intolerable. At 400uV i find two parallel 170s to sound just fine. If i may chime for Kuei the 10H is to separate the MC section from PS interference coming from the RIAA. Even batteries are not perfect and wire has impedance too. It probably works very well but for me it's easier and likely better to use a separate battery.
cheers
peter |
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| Kuei Yang Wang |
Koinichiwa,
| quote: | Originally posted by rookster
I am very inexperienced in the area of electrical circuits, but why is the 10H inductor/choke needed? |
You need some filtering, the signal levels on the MC are very low. I already had the chokes. You can try a seperate battery as analog_sa suggests.
Sayonara |
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| Tube_Dude |
| quote: | | As i mentioned previously the number of parallel FETs is a compromise between noise, resolution and bass. A single device sounds the most resolved to my ears |
I agree 100% with you...any time that i parallel any device i find the some compromise in resolution...:nod: |
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| peranders |
| quote: | Originally posted by jcarr
For further study, I suggest reading AN232 from Analog Devices, authored by Walter Jung. Even if you don't use any of the methods proposed in the application note, it should give you some food for thought. |
Jonathan or somebody else, where can I find this application note? It seems to that AD has withdrawn this application note. |
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| peranders |
| quote: | Originally posted by rookster
I am very inexperienced in the area of electrical circuits, but why is the 10H inductor/choke needed? I thought it was a filter, but the circuit is already running of a DC supply anyway. Thankyou for the details on the inductors, but I feel the cost and logistics of ordering 2 of these from Germay to Australia, would make it quite a hassle. Can i substitue something else? Any ideas? If this is the best option, then I will implement it. |
I think you have figured out that designing electronics is like painting pictures. Many solutions are right, many are wrong :bigeyes: . I would have used a inductor as a last option. The goal is to make a very quite DC voltage because this first stage is very sensitive for noise in the voltage. One other idea is to use R+C+R+C. The advantage of a inductor is that you don't need so big capacitors effective filtering but on the other hand caps are rather cheap and available so what is best?
My suggestion is:
22 ohms + 6800 µF + 22 ohms + 6800 µF = cut frequency 1 Hz / 40 dB/decade => -80 dB at 100 Hz quite OK if the raw voltage already is stabilized.
You can increase the R and also the C, and even the amount of R-C sections. |
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| analog_sa |
| 6800µF may sound very slow and thick in a simple common source config. While a choke and a small cap may sound much more agile and musical. |
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| peranders |
| Do we talk about the same thing? The filter should be slow in order to reduce noise, but I'll guess you are pulling my leg :clown: |
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| fdegrove |
Hi,
| quote: | | 6800µF may sound very slow and thick in a simple common source config. While a choke and a small cap may sound much more agile and musical. |
Peter,
I am rather at odds with your statement here.
From experience I often prefer oversized filter caps and small value coupling caps.
The bigger PSU caps provide good PSU filtering and ample current reserve , whereas the small coupling caps provide for the agility and musicality... they also tend to sound faster than their larger brethren.
Also, just from listening experience I find the higher voltage coupling caps to sound way better than the lower ones.
Does this go against your own experience?
Cheers,;) |
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| analog_sa |
Frank
My remark is only for the specific case of MC input. Current pull is generally low and the 'sound' of electrolityc caps very exaggerated. I would seriously prefer to break a large cap into a smaller + choke. With a reasonable choke you get better regulation and filtration which is easy to calculate.
This deceptively simple circuit with a FET and batteries, when implemented well sounds amazingly good. I got mine powered by NiMH batteries and two 100µF BG caps close to the FETs. To my ears it plays better than my Koetsu step-up transformer in every respect but S/N.
cheers
peter |
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| fdegrove |
Hi,
Peter,
Thanks for the swift reply...
| quote: | | To my ears it plays better than my Koetsu step-up transformer in every respect but S/N. |
Doesn't come as a surprise to me.;)
Here's what I do in my MC stage:
I use a capacitance multiplier after a voltage reg and have that followed by a ccs sitting almost right on top of the anodes.
In order to bring noise down to inaudible levels I also need to put a few triodes in // which is indeed a necessary evil as you pointed out.
Bass shouldn't be an issue since the RIAA filtering is done in the following stages.
Cheers, |
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| peranders |
| Thanks. How did you find it? Interesting idea in the application note. |
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| jcarr |
Per: The input-compensated bootstrap idea is admirably suited for DC servos, because yotu normally want a high input impedance anyhow.
Like Jung, I find that having some sort of output buffer in place is a good idea.
The test results of the input-compensated bootstrapped configuration were fine. I don't utilize this concept at the present, but this is primarily because the DC servo circuit that I do use is inverting with bipolar inputs. OTOH, this latter type of circuit has its own unique quirks that need to be taken into account during the schematic design and board layout phases. You normally don't even receive a discount on lunch, let alone getting one for free. :)
Should I decide once again to make a high-impedance, non-inverting, JFET input DC servo circuit, chances are that I will revisit the input-compensated bootstrap concept and see if it is possible to advance it further.
Examples of other interesting DC servos would include the simple design that Luxman used in their A901 battery-powered preamp. The "AOC" discrete differential servo that Akihiko Kaneda has been using for his more recent designs is also worth trying, and this is fairly similar to the output buffer section of my own DC servo circuit.
In any case, it is surprising how important the DC servo design is for the overall sonics. As I mentioned in a previous post, you will need to put much more effort into designing a DC servo than you will in selecting an output coupling cap, and there is a commensurately higher risk of getting something wrong. But as far as I can tell, the concept is fine - the actual design and implementation stages are where it is likely that you will stumble.
hth, jonathan carr |
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| Mad_K |
| Finally I have made a version more in line with Thorsten's recommendations. What can I say? It is simply wonderful! Some pics: |
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| Chris |
Just finished a phono pre based on Thorsteins El Cheapo (MM part only). Simply great sounding......:bigeyes: :) :D
Later tonight I`ll try this one...:D |
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| analog_sa |
| quote: | | Simply great sounding |
Lucky you! I haven't been so lucky mixing phono with opamps - even a simple Pearl or Ono offer lots more soundwise and are likely not more expensive to build. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by analog_sa
Lucky you! I haven't been so lucky mixing phono with opamps - even a simple Pearl or Ono offer lots more soundwise and are likely not more expensive to build. |
Let me guess. Op-Amp's, passive EQ between two of them, possibly attempting MC sensitivity with Op-Amp's, mains based supplies. I never had any luck that way either.
Sayonara |
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| Kuei Yang Wang |
Konnichiwa,
I would call this neither simple nor particulary suited to being a RIAA EQ.
Even if the errors in the RIAA EQ are fixed, this circuit throws away nearly 20db overload (and slew) margin at 20KHz, compared to an active EQ and even more by selecting a poor distribution of gain around the passive EQ. You can hear the result easily with dirac pulses often called "click" & "pop".
Circuits like this, even when optimised always seem to emphasise these noises rather much, as do slwerate limited active EQ circuits (the classic Dynaco PAS phonostage comes to mind as excellent example of how not to do it).
And why on earth insist on using two Op-Amp where one suffices?
Sayonara |
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| Christer |
I suppose I am not the only one having a good laugh at
the name of the engineer and drawer of that schematic. :) |
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| fdegrove |
Hi,
| quote: | | I suppose I am not the only one having a good laugh at |
Ah, ah...you spotted that too, huh?
Suppose Elso fell for the Low Noise Clock....
This one even funnier:
HAVE A LAUGH...
Cheers,;) |
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| ashok |
For the Vinyl experts.
The 'typical' MM cartridge is specified at about 5mV output for a velocity of 5cm/sec . I think I read somewhere that the maximum output of the cartridge could be about 350mV on musical peaks.
The question is ,what is the maximum signal level over the full bandwidth ( 20 ~ 20KHz) that a MM cartridge can produce with a sensitivity of 1mV per cm/sec at 1KHz. I am assuming that this is measured using a vinyl disc with the highest recorded levels . Maybe the 1812 Overture?
Cheers. |
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| ashok |
I found some white papers at the Vandenhul site which has the answer - or does it ?
http://www.vandenhul.com/artpap/phono_faq.htm#78
It says the absolute max output expected is about 71mV for a cartridge with a sensitivity of 1mV / 5.7cm/sec. So for a sensitivity of 5mV it must be around 350mV !
So a linear front end ( buffer ) amp should be able to handle that signal without clipping. Assuming an opamp with +/- 15 volt rails, you should be able to get at least 7Volts rms unclipped. So the gain can be at least 7/0.35 = 20 or about 26db.
Correct ?
Cheers. |
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| analog_sa |
| quote: | | Let me guess. Op-Amp's, passive EQ between two of them, possibly attempting MC sensitivity with Op-Amp's, mains based supplies |
Not really. The split passive EQ was my most successfull foray into opamp phonos, it had obvious dynamic shortcomings but extraordinarily good PRAT.
What i played with for a while was a variation of the El Cheapo with an added BUF634 within the FB loop. OPA627/637 are obviously not my cup of tea but AD8610 sounded reasonably good and allowed for very low dc offset. PS was discrete, series, open loop regulated. The sound? Good bass and reasonable, but not great PRAT. So-so dynamics, **** poor voices and very low soundstage. Musically i would rate it inferior to the phono section of a NAD3020A (5 transistors IIRC).
Using the same RIAA values and PS but replacing the opamp with a discrete (Aleph OnO) brings real improvements as far as dynamics and human voices are concerned but bass and PRAT are just ok.
Interestingly i like the sound of the Ono better with reduced PS to 20v. A 500VA transformer makes a huge difference up from a 60VA. Bang goes my intention to build a cute small SS phono :)
I guess it's back to tubes.
MC via an opamp? Wouldn't dream of it :) |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by analog_sa
What i played with for a while was a variation of the El Cheapo with an added BUF634 within the FB loop. OPA627/637 are obviously not my cup of tea but AD8610 sounded reasonably good and allowed for very low dc offset. PS was discrete, series, open loop regulated. The sound? Good bass and reasonable, but not great PRAT. So-so dynamics, **** poor voices and very low soundstage. Musically i would rate it inferior to the phono section of a NAD3020A (5 transistors IIRC). |
I hate to tell you, but it seems your design was a poor one, not my one. Do yourself a favour and build the Phonostage EXACTLY as I suggest, battery supply, exact decoupling of PSU lines, OPA637 et al, plus add the output Biasing. No added buffers, bugged up regulated supplies etc.
Sayonara |
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| analog_sa |
| quote: | | I hate to tell you, but it seems your design was a poor one, not my one. Do yourself a favour and build the Phonostage EXACTLY as I suggest |
I hate to tell you but i started with exactly your design . The addition of the BUF634 was slightly beneficial. Of course it works better with batteries than 'bugged up regulated supplies'.
This is pretty much irrelevant as the discrete opamp uses the same power source. You don't seriously suggest that a simple discrete opamp is more sensitive to PS than a 637?
I guess it all boils down to sound priorities and preferences. Ours seem to be a world apart. And maybe i have elevated opamp intolerance :) I really try hard to like them but they all (and i've tried lots) have the same sonic signature. Twenty something years on and they all sound like a 5534 where it counts. |
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| analog_sa |
| quote: | | I guess it all boils down to sound priorities and preferences. Ours seem to be a world apart |
On second thought this is probably wrong. You like the El Cheapo but wouldn't actually listen to it given a choice, would you? :) |
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| Fred Dieckmann |
"I suppose I am not the only one having a good laugh at the name of the engineer and drawer of that schematic. "
I'll tell Beau you find his name funny at lunch next week. You are lucky you are in Sweden. Mr. Platz is about 6'5" and played college football for the Arkansas Razorbacks......... |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by analog_sa
On second thought this is probably wrong. You like the El Cheapo but wouldn't actually listen to it given a choice, would you? :) |
On a scale of 10 I'd give ElCheapor an 8.5, my current Phono is on 9.75 for comparison. As I have the choice, yes, I listen to something else. But that "else" has a 1:15 differnetial in cost and much in complexity and is not that much better than ElCheapo.
So I guess it does come down to taste and perception, PLUS system context.
Sayonara |
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| Christer |
| quote: | Originally posted by Fred Dieckmann
"I suppose I am not the only one having a good laugh at the name of the engineer and drawer of that schematic. "
I'll tell Beau you find his name funny at lunch next week. You are lucky you are in Sweden. Mr. Platz is about 6'5" and played college football for the Arkansas Razorbacks......... |
You mean that guy's an american?? I thought he was
a pole. :eek: |
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| Elso Kwak |
| quote: | Originally posted by Kuei Yang Wang
Konnichiwa,
I would call this neither simple nor particulary suited to being a RIAA EQ.
Even if the errors in the RIAA EQ are fixed, this circuit throws away nearly 20db overload (and slew) margin at 20KHz, compared to an active EQ and even more by selecting a poor distribution of gain around the passive EQ. You can hear the result easily with dirac pulses often called "click" & "pop".
Circuits like this, even when optimised always seem to emphasise these noises rather much, as do slwerate limited active EQ circuits (the classic Dynaco PAS phonostage comes to mind as excellent example of how not to do it).
And why on earth insist on using two Op-Amp where one suffices?
Sayonara |
Goedemorgen Kuei Yang Wang,
I received the following email from Pat's Lab which I reproduce here with full permission:
Thank you for visiting our site, and your kind words.
Yes, it appears that there is an error in the drawing that you refer to.
Please accept our apologies for this. Perhaps we need to add a "checked by"
line in the title block. When built as it is intended, we can assure you
that the RIAA response is accurate. We did not make provisions for the
additional IEC and Neumann time constants, as this is intended to be a
"simple" MM preamp.
In response to the other issues that you raise, we feel that it is very
discouraging that someone would see fit to make derogatory remarks about it
without building, testing, or listening to one. We have strong feelings that
passive EQ allows for accurate deemphasis that is not possible with a
feedback network.This is due to pole-zero interaction, and the effect of
finite open-loop gain. If you will examine the open-loop gain of the op-amp
that we chose, you may better understand why we feel that is it a good
choice to be used with passive networks.
As for suitability with MC cartridges, it is possible that the 100 ohm
resistor could be lowered to achieve additional gain. However, we have not
tested it in this manner. The cartridges that we use have an output in the
range of 3-4 mV. We prefer using inexpensive cartridges, and using the money
that we save to buy more records.
We thank you for your invitation to visit and register on your favorite
forum. We would prefer to remain independent. If you like, you may post this
e-mail in its entirety on your forum, if its rules permit. You have our
permission to do so.
Regards,
"P., B., and J." @ Pat's Lab
I addition to that I can submit that the circuit is very similar to the one in Analog Devices Application Note 124 fig.3.
Tot ziens.
:cool: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Elso Kwak
When built as it is intended, we can assure you
that the RIAA response is accurate.
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But not when build as drawn originally.
Looking at the names and the circuit as drawn I was forced to draw the conclusion the schematic was a ludibrium.
The revised design is indeed flat in RIAA response, assuming narrow Tolerance capacitors.
| quote: | Originally posted by Elso Kwak
We did not make provisions for the additional IEC and Neumann time constants, as this is intended to be a
"simple" MM preamp. |
These timeconstants do not make the circuit any more excessivley complex than it already is, anyway.
| quote: | Originally posted by Elso Kwak
In response to the other issues that you raise, we feel that it is very discouraging that someone would see fit to make derogatory remarks about it without building, testing, or listening to one. |
I have build very similar circuits before and my remarks hold in the areas criticised.
The first stage has a gain of 1+10k1/K1 or 102. With a "standard" 5mV rated cartride with peak outputs in the 350mV range this will pretty reliably clip the input stage with high level signals, especially with the kind of dirac pulses found with loud clicks but potentially also when the record is cut with high levels, examples may include many Audiophile pressings and many DJ 12". The overall gain
Secondly, the use of a passive EQ further reduces the overload margin at high frequencies by about 40db, in a design that already has a poor overload margin due to it's gainstructure.
The implications on the S/N ratio are material too. And if more normal Op-Amp's (lower bandwidth) had been used there would also be implications at higher frequencies. Of course, the price paid for using fast Op-Amp's is excessive noise, which is specified at 12nV|/Hz leading to an Ein of 1.7uF or a S/N ratio of -70db linear with respect to a 5mV input and -56db referred to a 1mV input.
| quote: | Originally posted by Elso Kwak
We have strong feelings that passive EQ allows for accurate deemphasis that is not possible with a feedback network.
|
I have found quite reliably that +/-15V supplied op-amp's lack the dynamic range required for use with passive EQ's. IN PRINCIPLE I am in favour of passive equalisation, but not if it leads to drastic tradeoffs elsewhere.
| quote: | Originally posted by Elso Kwak
This is due to pole-zero interaction, and the effect of
finite open-loop gain. If you will examine the open-loop gain of the op-amp that we chose, you may better understand why we feel that is it a good choice to be used with passive networks.
|
And if we observe noise and output range it is a rather poor choice, from the available ones.
| quote: | Originally posted by Elso Kwak
As for suitability with MC cartridges, it is possible that the 100 ohm resistor could be lowered to achieve additional gain. However, we have not tested it in this manner.
|
Well, using a (not untyphical) 0.2mV pickup the input reffered S/N ratio will plummet to around 41db. I find -56db Input referred S/N ratio easily audible in the pauses between music (and thus by definition low level detail is also effected) but -41db is absolutely unacceptable. So MC's are out unless the first Op-Amp is changed to something a lot quieter, like an AD797.
| quote: | Originally posted by Elso Kwak
We prefer using inexpensive cartridges, and using the money
that we save to buy more records.
|
One of the best inexpensive cartridges is the Denon DL-103, which happens to be a low output MC.
| quote: | Originally posted by Elso Kwak
I addition to that I can submit that the circuit is very similar to the one in Analog Devices Application Note 124 fig.3.
|
Very good. This adresses non of the critique points raised.
I PERSONALLY would for MM simply return to the much simpler 1 Op-Amp feedback combo with suitable Op-Amp's (yes, even the AD825 would be nice here) if simplicity with good sound is the goal, this way noise is better controlled by far and the overload margin is not frequency dependent.
Sayonara |
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| ashok |
The maximum signal output expected from a vinyl groove is about 350mV . This is due to the stylus velocity.
The Shure V15 specifies a maximum trackability of 80cm/sec at 5Khz and 60cm/sec at 10Khz.
The cartridge output depends on the groove velocity which varies with frequency. By that I mean a 1Khz signal and a 10Khz signal of same amplitude will have different groove velocity , the 10Khz having much higher velocity.
So when we talk of a maximum of say 70cm/sec we need not be talking about 1Khz or 10Khz - just groove velocity.
What I am getting at is that the preamp input will not see a voltage higher than say 350mV no matter what the frequency is. With a gain of about 20 it will comfortably handle any input peaks.
So HF overload is not a separate issue from this. Everything is taken care of. There should be no problems with HF . One could always include a Hf roll off beyond 20Khz in the first stage to take care of any severe clicks and pops. In any case a record that noisy will be a nuisance to listen to .
The cartridge plus loading in any case have a HF roll off beyond say 30Khz. So supersonic frequencies may not have any significant amplitude at all.
Cheers. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by ashok
The maximum signal output expected from a vinyl groove is about 350mV . This is due to the stylus velocity.
<snip>
With a gain of about 20 it will comfortably handle any input peaks.
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Yet the schematic discussed has a gain of 102, not 20 and thus will attempt to produce > 35V RMS from a 350mV Input with 15V rails. The results are predictable.
Sayonara |
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| jewilson |
Kuei Yang Wang
I have never seen a cartridge that can even come close to putting out 350mv, even at the highest frequency, however I don’t use Radio Shack cartridges and don't care about the ability to reproduce pops or clicks. However If your concerned about overload margin with some of the high out put cartridges the gain of the input opamp can be reduced to 30db with out penalty to the passive network.
As for as noise performance goes it best to have the majority if not all the gain in the first amp. Speaking of the circuit noise, if the gain was split 20db and 20db between the amps the noise then becomes greater than having the majority of the gain in the first amp. This is normally called adding the sum of the squares. Noise adds not multiplies through the changing of amps, do the math.
The passive network also allows the use to select the lowest values of components As apposed to the active feedback RIAA amp where the values do increase the current noise.
So the lower the impedance of the passive network lowers the circuit’s noise compared to the active circuit.
Also since the first amp runs at high gain it does not need to be unity gain stable and compensation is not needed. So the user has more options in the selection of amps. The active RIAA will increase the number of poles and change the open loop characteristics of the amplifier causing distortion and instability. So, the response of the passive circuit has better performance at high frequencies because it has much less interaction between the feedback network.
So picking this topology as a problem is barking up the wrong tree. However maybe we have, we shown you that this circuit has more potential than you realized, and you’ll try again with it or maybe you just want to argue.
Also, there are a number of way to design an implementation the passive RIAA beside the way it was done in PatsLab. Also, the fact is that all of the passive RIAA network don't have the same formulas. I can list a few if your really interested. |
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| Jocko Homo |
You are as confused as a barking bird. I would like to see a cartridge that can output that much.
It would overlaod any amplifier, too. How do you explain that, bub?
You can't.
The maximum voltage that a cartridge like the one these guys probably like (I am guessing a $20 Grado, maybe a $40 one when they feel lucky) will be roughly 20 mV. So.......2 volts max in the first stage.......and then attenuated in the passive EQ.
Yeah........35 volts output from a preamp. Give us all a break, pal.
Jocko |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Jocko Homo
You are as confused as a barking bird. I would like to see a cartridge that can output that much.
It would overlaod any amplifier, too. How do you explain that, bub?
You can't.
|
I have a Cartridge rated 6.5mV/5cm/s and it tracks reliably a +16db track on a testrecord, outputting thusly around 40mV lineary. Higher levels can be tracked by this pickup, as evidenced by some 12" DJ Pressings.
I have somewhere a complete set of calculations, based on stylus velocity etc. which suggest a the ability of the LP to have surprisingly high levels (and we are not talking telarc 1812 either). The 350mV came from a teoretical calaculation of trackable velocity earlier in the thread. I would expect on LP's cut to the limit still > 100mV with higher output MM Pickups on peaks, from experience.
And again, if your pop or click from some dust overloads or slews the Op-Amp (slewing not in your design) then the noise becomes more audible then it would be when it is not clipped.
I'm not sure about $ 40 Grados, never used one. But decent cartridges can track quite some level and it is present on more than a few LP's.
No matter how you turn and twist it, with passive EQ you are trading noise and overload margin and you don't have that much of either if you use Op-Amp's (you have tons of overload margin and very low noise using outdated and obsolete Valves, but that is another story). At best the tradeoff barely works well, at worst it either hisses a lot or clicks and clips a lot.
Sayonara |
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| Panelhead |
| quote: | Originally posted by analog_sa
Using the same RIAA values and PS but replacing the opamp with a discrete (Aleph OnO) brings real improvements as far as dynamics and human voices are concerned but bass and PRAT are just ok.
Interestingly i like the sound of the Ono better with reduced PS to 20v. A 500VA transformer makes a huge difference up from a 60VA. Bang goes my intention to build a cute small SS phono :)
I guess it's back to tubes.
MC via an opamp? Wouldn't dream of it :) |
The average bass response in my Pearl is something I would like to fix. This is the one area that could use improvement.
There is a 23 ufd cap on the coupling the output. The 2SK389 transistors were selected for a high current draw. Each channel is running 13 -14 ma now.
The input is feed with a pair of 2SK170BL jfets and cascoded with a ZTX450. The coupling cap here measures 1.03 ufd and the imput of the Pearl measures 45.4K.
Compared to my tube phono and stepups the bass is much tighter and clear. Very reduced in level though. I could blame this on the doubling and mushy tube phono bass just seeming larger.
But my disc player delivers chest and room pressurizing low end response that you feel and cannot really hear. The phono cannot duplicate this type of bottom end. The arm is an OLRB-250 and cartridge is a Denon 103R.
Is the RIAA circuitry the culprit, or is there another weakness in there somewhere?
George |
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| jewilson |
Kuei Yang Wang
As i stated the noise is only a few db worse, how then gain in Linearity is well worth it. Having read your responces it seem you may not understand how to measure noise, or locate the pole zero's, in the circuit so this discussion seems pointless. |
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| ashok |
For those who missed part of the thread.
The 350 mV figure came from Vandenhul , the cartridge people !
(check the link )
In addition I remember reading this in Wireless World many years ago when Vinyl was king.
I think this translates to over 120cm/sec groove velocity. Pick your cartridge and determine its maximum output. With lower sensitivities the " 350mV " figure will be much lower.
This was a Maximum Limit EVER possible and is much higher than the maximum groove velocity seen in commercial pressings. The figure was arrived at to design phono stages that would never overload under any circumstance. It is possible that an ocassional pop , even minor ones , could slew much faster than 70cm/sec. A piece of dust in the groove will produce a much faster stylus deflection than any recorded signal. So one has to take this into account . This is why probably many tube RIAA stages can sound "quieter" than some ss RIAA stages.
Cheers. |
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