| rjm |
Very Simple Phono Stage
Only 27 parts for the whole stereo unit.
User configurable gain 30-50dB.
Standard value components, even for the RIAA eq.
Allen Wright modded RIAA response. Accurate to +/- 0.25 dB.
Use any standard dual opamp.
Layout diagrams and photos included. Easy to build. (For those who previously visited, I have today updated the page to make it clearer and simpler to understand for the neophyte.)
-rjm |
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| Ropie |
Excellent page, RJM, with great scematic drawings.
How about including a battery psu as an alternative to mains? From what I have read/been told recently, a battery psu will give the best performance for a sensitive device like a phono stage. |
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| rjm |
Hi Ropie,
As noted, you could use batteries. I've never much cared for the results and that article at TNT does lend some credibility to that little prejudice of mine.
Be that as it may, as for a schematic since anything from 2 9-volt batteries on up through lead-acid cells up to caseloads of magnesium C-cells will work, I felt those who like the sound of battery PSUs are best left to implement their individual favorites.
I expect that while most people will be quite comfortable with the amp circuit, the regulation part might raise eyebrows. Pretty dinky hey? Sure, but it is "sufficient" and sounds surprisingly good - natural & musical. Please try it before experimenting with more conventional solutions.
All roads lead to Japan or some such nonsense. And I'm quite serious about those carbon resistors, too.
-rjm |
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| matjans |
did you do any measurements? noise floor level etc. would be interesting to know.
And, most important, how does it sound ?
I have recently bought a project phono box and after replacing a number of components it sounds pretty good. |
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| rjm |
| quote: | Originally posted by matjans
And, most important, how does it sound ? |
I'm avoiding plunging into a description of the sonics for two reasons: the practical one is that my current system is a bit of a knock-up affair and the speakers especially not really of sufficient bandwidth to make a full evaluation. And then the more acadamic one that the designer isn't really the right person to make an objective review now is he?
For all their faults though the speakers are very coherant and clear in the midrange, with a true to life instrumental timbre even if dynamics are rather compressed.
OK? With that, and remembering that the Black Gates haven't yet been fully broken in, my "golden ears" tell me the following:
RIAA is spot on, though I swear I can hear the Allen Wright mod as a slight increase in clarity over the normal eq curve. Hum is absent, noise is low but I can't get a good feel on this. Distortion is also low. High freq oscillation - assorted opamp nastiness - is mercifully absent. That at least I can tell with certainty.
Top to bottom (remember though I don't get the true extremes with my speakers) it all seems remarkably natural. No part of the music is over-accentuated, there's no overhang or smearing. No grain, no flatness. For any LP I play - and with the VSPS hooked up I'm playing everything I can get my hands on - I run into the limitations of the speakers well before I can detect any problem with the phono stage. Note the limitations of my QED Discsaver are readily apparent under the same circumstances.
Take that as you will - I think its pretty nifty. What's musically important to me it nails authoritatively - yet its dirt cheap and a quick and easy build. Cool!
-rjm |
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| Kuei Yang Wang |
Konnichiwa,
I have a few comments that may or MAY NOT interest you. They are meant constructive, in the interest of improving the design further....
1) For a MM sensitivity Phonostage to be used with a MM Pickup the Op-Amp's current noise dominates the noise unless the Op-Amp is very noisy. This due to the very high inductance of MM Cartidges, up to around 1H which causes material levels of impedance to appear on the input.
With FET input Op-Amp's input current noise is virtually nil, MOST BJT Op-Amp's have a rather high input current noise which will make the stage noisy with MM Pickups. For MC picups (even medium/high output types) a BJT input Op-Amp tends to be apropriate as the source impedance is low and the input noise current matters much less.
Also, MM Cartidges require a correct capacitive load (usually quite high) which forms a resonance circuit with pickups inductance to boost the treble. Usually the best course of action is to shoot for a capacitive load that places the peak at 18-20KHz and to adjust the load resistor untill a pink noise spectrum in the middle of the record shows no HF lift or droop. Then there will usually only be a small amount of HF loss in the inner groves.
2) This is a trick I learned from Allen Wright and have used many times by now. return the AC coupled Feedback loop components (R3/C1 & R4/C2) not directly to the Op-Amp output but to the output after the output coupling cap C3, follow this by the "build out" resistor R6. By insluding the output coupling into the feedback loop it's sonic influence is lowered somewhat and LF RIAA accuracy improves. Sounds notably better wherever I tried.
3) The RIAA capacitors are chose quite high in value. Remember that output stage must supply the current to drive the RIAA network and any external capacitances too. The load at high frequencies from the current values is equal to 1k in series with 3n3, this is quite a notable load which may make many an Op-Amp distort more than neccesary, especially in terms of the various non-harmonic distrotions.
I found scaling the impedances in the NFB Network up by a factor 10 (meaning all resistors * 10 and all capacitors /10), all else being equal sounded better with all the common Op-Amp's I tried. Also smaller value capacitors can often be had in better quality. For fun, try a air dielectric AM Receiver variable tuning capacitor adjusted to 330pF in the HF section of the EQ (they often have two identical sections with excellent tracking making one good for stereo). Very earopening....
The noise is usally dominated by the source and Op-Amp together, so the increase in noise from the higher feedback impedances tends to be minimal.
Combining 2 & 3 can mae a surprisingly large sonic change, which I at least consider a bona fide improvement.
Lastly, if you can find a 4-pin connector for the powersupply consider keeping the "grounds" of both supply lines seperate and only connect them together at the "power star", which would be the point where the output current loop and PSU decoupling capacitor current loop are "starred". I would recommend also seperate ground lines from there to the Input ground with R2 returned to the respective channels input "ground" point.
Anyway, just a few notes.
Sayonara |
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| rjm |
Your suggestions here are all very reasonable ones. In the spirit of discussion I’d like to respond to a couple of points.
Impedance of MM cartridges and op-amp noise.
If, indeed, the inductance of the cartridge is in the order of 1 Henry, then your suggestion that a FET input op-amp would likely have lower noise than a BJT input is at higher frequencies generally true and I urge anyone with such a cartridge to consider the OPA2134 etc. over the NE5532 in this circuit.
With a FET input op-amp it might also prove useful to scale the feedback components by 10. With larger impedance it is easier for the op-amp to drive, and with the high source impedance + low current noise op-amp there is no noise advantage to keeping it low anyway.
Since scaling the loop still keeps all the parts as standard values, its easily done.
Not all cartridges have such high impedances however. My daily-use Grado 8MZ has a resistance of 470 ohms and inductance of 45 millihenries. The more expensive models of that series have a resistance of 70 ohms and inductance of only 8 mH. Over most of the audio band the source impedance is below 1k, and best noise performance is obtained with bipolars (low voltage noise) in combination with low values for R2. This configuration will however favor op-amps with low distortion drive into 1k ohm loads - the NE5534 being one of these.
C3 in the FB loop.
That’s also an easy mod and worth trying. The only curiosity I see with doing that is the feedback at DC falls to zero. I actually prefer the sound of those nonpolar 4.7uF Black Gates to a piece of wire (I find it adds a hint of warmth with no loss of transparency) so I'm personally quite comfortable with the conventional position. The low frequency response is 3dB at 4 Hz for 10k load, or -0.25dB at 20 Hz, so likewise the RIAA error it induces isn’t something I’m going to lose sleep over.
Grounding.
Absolutely keeping the input grounds separate until the star point is the correct method. Call me unprincipled but considering the channel separation of the cartridge itself I just can’t get excited over 4 cm of shared input ground.
Separate power grounds to the transformer windings are likewise the best implementation I’ve so far seen. I would have hooked up both my Gainclone and the VSPS that way but for my lazyness: it’s a lot easier for me to come by 3 wire 16-18 gauge power cable than 4 wire.
-rjm |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by rjm
Not all cartridges have such high impedances however. My daily-use Grado 8MZ has a resistance of 470 ohms and inductance of 45 millihenries. |
Yes, Grado's use a different technology to Moving Magnet Cartridges (they are a "third kind" of cartridge outside the MM/MC division with Decca's being the "fourth kind"). The much more typhical Shure V-15 clocks in at 680mH or 0.68H....
| quote: | Originally posted by rjm
I actually prefer the sound of those nonpolar 4.7uF Black Gates to a piece of wire |
Well, that is a personal choice.
| quote: | Originally posted by rjm
The low frequency response is 3dB at 4 Hz for 10k load, or -0.25dB at 20 Hz, so likewise the RIAA error it induces isn’t something I’m going to lose sleep over. |
True. Another Mod I had not mentioned but actually highly usefull and somewhat original would be to make the EQ curves adjustble to match also the DECCA & COLUMBIA Stereo EQ curves and possibly CCIR (Europe mainly eastern)....
| quote: | Originally posted by rjm
Call me unprincipled but considering the channel separation of the cartridge itself I just can’t get excited over 4 cm of shared input ground. |
I understand that, channel separation was never the consideration, rather current loops per se are.
Sayonara |
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| bg40403 |
In the RJM circuit schematic, R3, 4 & 5 share the negative IC lead through R2 to ground.
In the "beginners" drawing they are depicted as a closed loop on the output leg.
What gives? |
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| rjm |
Checked it out and noticed the trace from the top of R5 to the blue trace connecting R2 to the IC isn't visible. It's "under" the resistor - there are only a couple of pixels peeking out! I'll fix that shortly.
Thinking about T's comments I'll branch the component list early on into a Version A (low impedance, bipolar-op-amp, for Grado-type carts) and a Version B (high impedance, FET op-amp, "typical" MM carts) with the difference being the 10x scaling of the feedback loop.
Since I have to fix the layout for the invisible trace I migth as well modify the grounding too.
-rjm |
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| carawu |
Moin T,
there is only one group between MC and MM: the MI = moving iron type. grado and decca share the same principles (some BangOlufsen too); of course decca is mechanical more complicicated. Please check this link for further information (sorry folks, german only and pdf size is >3mb!)
http://mitglied.lycos.de/carawu/hif...Artikel_RLA.pdf
Carsten |
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| spike_petar |
i have completed your VSPS yersterday and i must say that i am very happy with the results , the sound is very detailed, a bit on the bright side... :)
i haven't yet decided how to box the unit and whether to leave PSU separated or try to put it in the same box, also is it absolutely neccesary to put it in a box made of metal (to provide case ground) or could the box somehow be made of wood?
btw. the parts have costed me about 15 euro!
once again thanks for the very simple (cheap) project :) |
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| rjm |
Usually the turntable has to be connected to the circuit common. This is normally done at the phono pre through attaching to a metal case which is itself connected to the circuit common.
But you can attach the TT ground wire to the amplifier ground if you prefer, or directly to the circuit common of the VSPS. So, no, you don't have to have a metal case though I would recommend it for the shielding it provides.
For the brightness, there are two points: 1) the Allen Wright RIAA curve is "lighter" (brighter?) than the traditional RIAA. 2) the Black Gate output caps (if you are using them) take about 3 weeks to settle in. For the first few days they sound hyper-loud and flashy (bright?), then they turn abruptly stuffy/cloudy before they finally begin to clear up and the bass fills in. Week 3-4 is the best because each day the system sounds noticeably better than the day before.
I've been through this about three times now and it is highly unsettling each time. I should really break in the caps before listening to them but each time I tell myself I can't be bothered...
So I'd give it about a month before passing a final verdict. You can in the meantime try shorting over R3 with a paper clip or suchlike to defeat the Allen Wright treble rise.
If you build the "HiZ" version its very easy to just wire over R3.
If with the LoZ version you short over R3 maybe the brightness gets worse, this is actually even better result because it proves that its the NE5532 driving low impedance load rather than the AW curve thats at fault. Solution is to switch to HiZ feedback loop.
I'm still investigating the sound I'm getting "as built" and I haven't got around yet to tweaking even the obvious things like switching opamps.
Hopefully you'll keep us updated as well.
-rjm |
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| Werner |
The 50kHz Neumann correction (I don't call it AW as AW, AFAIK, did not 'invent' it) gives a 0.5dB rise at 20kHz. Lower than the frequency response aberations in almost any MM, MC, or dare I say it, curring setup. This is not the cause of brightness.
In fact I have a prototype on the bench, including 50kHz correction, measuring almost ruler flat up to 20kHz, and yet I can turn it from lush into steely merely by swapping one capacitor type for another.
I would rather look into the compound response of the opamp + RIAA network, calculated/simulated with the ACTUAL measured R and C values.
I would also ensure that the opamp is well-fed and decoupled resistively from any capacitive load, including the output cable. |
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| spike_petar |
thanks for your replies!
i forgot to mention in the earlier post that i built the loZ version, with NE5532, also i couldn't use Black Gate's since they are not avaliable in Croatia.
one more thing that bothers me is that the amount of hum slightly increased as the unit is breaking in, the hum in inaudible at normal listening levels, but when i turn up the volume it is there and it's annoying....
the cartridge is Rega bias |
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| rjm |
Ran through some analysis for ya -
Rs is the source impedance (cartridge) contribution
Vn is the op-amps voltage noise, 5 nV/rtHz
In is the product of the current noise and input impedances
Rf is the resistor noise of the feedback arm (R2 and Rf combined)
The plot shows various contributions to the total noise, for a NN5532 / 1Khz. The resistors are as per a VSPS in the hiZ configuration: R2 2.2k, Rf nominal@1kHz (220k). That's a hypothetical worst case scenario, just to see if hanging big resistors off a NE5532 makes a significant difference. The answer is: no, not a big difference. Switching to a OPA2134 won't change the total noise all that much either.
Remember that input-referred noise performance is not exactly the be-all and end-all of a phono preamp design. I just thought a quick calculation might be informative, that's all.
-rjm |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by rjm
Ran through some analysis for ya -
<heavy snipping>
The answer is: no, not a big difference. Switching to a OPA2134 won't change the total noise all that much either.
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Hmm, lets a Shure V15 (680mH/500R IIRC) with a 47k Parallel resistor.
The Impedance of this is around 910 Ohm @ 100Hz, 4k3 @ 1KHz and 22k5 @ 10KHz.
The Philips Datasheet lists the NE5532 as having an Ein of 5nV|/Hz at 1KHz and the Iin as 0.7pA|/Hz.
This current noise translates in a voltage noise derived from the impedance and the noise current as 0.6nV|/Hz @ 100Hz, 3nV|/Hz @ 1KHz and nearly 16nV|/Hz @ 10KHz. Or in other words, the noise from the source will be 10db higher at high frequencies than that from the source and in the "midrange" it will be more less the same as the self noise.
In other words, the self noise of the Phono Amp changes from "pink" to "white" with an emphasis on high frequencies and reduced S/N ratio. Given that the NE5532 is a little marginal for phono applications to start with, using a low noise FET type will eliminate the noise rise with frequency and keep the noise "pink" and low, with traditional MM Pickups.
For Grados NE5532 is not a bad choice, though other op-amp's are being made, with potentially superior sound.
Sayonara |
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| rjm |
Your numbers look right to me.
But .. you'll notice its the source noise 4kT Rs rather than the current noise term which dominates even for the NE5532 -at least below 10 kohm. So no benefit to further lowering the current noise by going with a FET input stage except for the 20kHz case.
(For those (trying to) follow - Rs is a function of just the input impedance and isn't influenced by the opamp at all. Current noise voltage is a product (loosely) of the source impedance and the opamp current noise.)
I'm not saying no benefit to a FET input - there is a benefit (the high frequency situation you mentioned) but it is more marginal than I originally thought - I had assumed current noise would dominate even at moderate frequencies and source impedances.)
and I'll tack this update on to avoid posting twice:
I tried shorting over R3 to see if I could hear the effect of the treble lift induced by the AW mod.
Well, I can plainly hear it ... more properly I can hear the effect of shorting over R3 in the VSPS circuit. Besides decreasing the high frequency response, the feedback impedance at high frequency is also decreased. What I hear could be due to the altered phase/frequency, impedance, or level of feedback.
Nonetheless it plays like a straight high-frequency lift: without R3 the sound is slightly soft. Putting R3 back in adds a more "live" feel to the music. Individual notes seem more precisely defined. Percussion has more transient snap.
In my system I preferred the eq. "with R3" by a wide margin - though it had me scurrying back to re-adjust the stylus azimuth. I wouldn't call the circuit bright, not at all in fact - but it will reproduce any upstream crappiness with pristine fidelity. :)
YMMV
rjm |
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| rjm |
Pick and op-amp, any op-amp!
For fun I reworked the sim to include the frequency dependence of an inductive source and a complex feedback impedance.
Now we have frequency on the X-axis, with noise calculated for a Shure V15VMR (1kOhm + 425 mH). VSPS circuit, NE5532, LoZ version shown.
1/f low frequency flicker noise is not modelled, so I haven't shown below 100 Hz. Opamp noise taken as the 1Khz datasheet values.
The blue line is the source noise. That's fixed by the cartridge and cartridge alone. The game is to try keep everything else below this as much as possible.
The horizontal brown trace is the opamp voltage noise. It starts to dominate at low frequencies.
The pink trace is the current noise. Somewhere above 12kHz, it overtakes source noise. (For the Grado cartridge it doesn't do this until above 100 KHz.) With a FET input opamp the current noise drops off the graph, no longer important.
The light blue trace is the noise of the feedback loop. It decreases at higher frequencies because of the RIAA filter. In the LoZ version shown, it doesn't play any significant part, but with the HiZ version its about 8 nV/Hz, about the same as the voltage noise of the OPA2134, and slightly higher than an NE5532 (5nV).
So it all confirms what we've been discussing:
FETs get you lower noise at high frequencies.
Bipolars get you better noise at low frequencies, unless the feedback impedence is high.
Somewhere in the middle it doesn't matter since source noise dominates.
And its all dependent on which cartridge you use.
-rjm |
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| rjm |
Same data as above, but referred to the output by multiplying through by the gain and displayed in dB.
The RIAA eq. means lower noise frequencies are amplified more than higher noise frequencies.
If anyone can suggest a better opamp to use for MM carts than the OPA2134 let us know! The AD825 has a good reputation, though you'll have to mess around with SOIC packages. It's noiser than the OPA2134 however...
Likewise a better op-amp than the NE5532 for Grado MI types. |
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| peranders |
rjm, it seems that you have forgotten one important part!
The whole noise generating source consists of L+R+C. You have forgotten the C of the cable and the input matching. 100-400 pF must be added to your circuit. This may have some influence of the noise. |
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| carlosfm |
rmj, you could do a much better circuit layout.
That's no way of using an op-amp.:whazzat:
No PSU caps near the chip?:eek:
I wouldn't be surprized if the NE5532 sounds better on this circuit that the OPA2134...
Anyway, for a phono pre with a double op-amp I would go for the OPA2228 instead of the OPA2134.
:angel: |
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| peranders |
Except for forgetting(?) decoupling caps of 100 nF (common practice) I think his effort is alright if the goal was to make it simple.
Please check datasheets of the IC's you have used and you'll see how you should power up the IC's. |
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| carlosfm |
Per-Anders, I'm just trying to be constructive and help rjm make a better circuit layout.
Spare two cheap caps doesn't make sense to me, even on a simple design.
And, I've said it several times here, you can ruin the sound of an OPA (or any modern/fast op-amp) just by using it the wrong way.
Believe me.
So... why bother to use an OPA2134 on this circuit?
Gotta tell you a secret: the OPA2228 behaves much better without bypassing.;)
If you try it on this circuit as it is, it will SOUND much better than the OPA2134.:cool: |
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| rjm |
P-A, is the cable capacitance in series to the cartridge impedance, R+L+C? I would have thought the capacitance is between the input and ground. In any event even 400pF isn't going to make much of a contribution at these frequencies, and pales in comparison to cartridge inductance.
As for the bypass question:
In my view this is not a high frequency circuit. Small signal bandwidth is about a megahertz depending on the gain setting and op-amp used. So "close" to the opamp may be taken in cm rather than mm.
The low impedance electrolytics, which are only 3 cm of straight wire from the op-amp's power pins, should provide good bypassing over the bandwidth of the circuit.
But, just because I don't always trust my own analysis :) last week I did put 0.1 uF ceramics in the "proper" place next to the power pins of the op-amp.
[I should add that most people seem happy if the cap itself is next to the power pins and don't worry particularely how far away it is to the load return. Be that as it may ... ]
I could, just about, hear a difference, though it was at the limits of my perception. The treble took on a slightly damped, closed in quality. With the caps gone the amp sounded more open and natural, but perhaps noisier.
For now the caps are gone, I think I prefer it this way but I'll keep an open mind while I continue the evaluation of the circuit in general and have a chance to check out how an OPA2134 sounds in there.
-rjm |
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| carlosfm |
rjm, it's more important to have capacitance near the chips than just a 0.1uf cap.
I'd put two small 22~100uf caps between the chip's pins and ground.
If there's no space to bypass with a small one, then don't bother.
The OPA2132, that I know very well (similar to the 2134) has a detached bass, uncontrolled, flappy, dominant, if used on a circuit like you have now.
Treat it as it likes and it will give you a tight, dynamic, detailed presentation, very impressive.
High-end, really.
I talk by experience with these chips.
I mean building and LISTENING experience.
Not just electronics by the book.
My passion is Audio.
:angel:
BTW to all, take or leave my advice, it's up to you. |
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| rjm |
To change the subject a little, what do you think of this then?
VSPS Ultra
It's a little extreme, in the early stages, and may yet be consigned to the dustbin - but feel free to chew into it anyway. I'm not too familiar with moving coils, so expect bugs.
-rjm |
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| carlosfm |
The value of the caps on the feedback loop is too high...
And I don't understand why you put only 220uf before the regulators.
And why 220uf after the regulators.
Better would be to bypass the regulators' output with a small cap and put the caps where they are needed: AT THE OP-AMP'S SUPPLY PINS.
Does it make this simple design more expensive?
Don't think so.
Just better.:) |
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| rjm |
I re-wired the VSPS filter caps as shown on the pic below.
The output from the regulator is wired directly to the IC power pin, and this 220uF cap is no in effect wired directly to the IC power pins too.
Granted the leads are still a bit longer that one might like, but any bypass cap would have to be connected to the load return point (the red oblong on the ground next to R7) so it isn't that bad a compromise.
So we now have the IC "directly" bypassed by a large value cap, as Carlos wanted. Simple experiment:
If I'm right then this connection change will make absolutely no difference in the sound. The circuit is equivalent but for a few cm of wire.
If I hear any difference then I'll have to start paying attention to his posts. :D
Guess what: pretty big difference. Similar but more significant than when I tried bypassing with the 0.1uF ceramics: less treble energy, less noise. The balance of the music is shifted quite dramatically downwards from the treble to the midrange. This time though the naturllness of tone is retained.
Go figure. I'm going to look at the layout again to see what can be done to tighten up the distances.
-rjm |
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| carlosfm |
rjm, next time pay more attention to my words.
I'm still not crazy and I know what I'm talking about.
:angel:
I mean something like this, and this is still "cheap and simple".:D |
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| rjm |
I realise that's what you had in mind.
(Where would we be without MSPaint!)
220uF is sufficient before the regulator to prevent dropouts. I see no point in increasing the conduction angle further by adding capacitance ... been there, done that, sounds bad. Though 2200uF is still borderline ok if you insist.
My main objection is those 47uF bypass caps now create a nice little ground loop indicated by my zigzag line. Noise currents off the power supply are now injected into the op-amp inputs. To prevent that you'd have to take the input grounds back to R2-R7 by a separate wire and that starts getting a bit messy!
Although having the caps physically sung next to the op-amp looks nice and correct, its really a false sense of security. The point the bypass has to get back to is R7. Whether the cap is next to R7 with a lead up to the IC, or at the IC with a lead back to R7, makes no difference to any electrical response.
rjm |
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| carlosfm |
What???!!!:confused:
Gotta run!:bawling: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by rjm
My main objection is those 47uF bypass caps now create a nice little ground loop indicated by my zigzag line. Noise currents off the power supply are now injected into the op-amp inputs. To prevent that you'd have to take the input grounds back to R2-R7 by a separate wire and that starts getting a bit messy!
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Yup. Good grounding is NOT easy. It does help to have the supply grounds separated until the star ground and to NEVER use BUS grounding (no matter how tempting). There are several possible neat tricks around this.
I prefer the one where there is only ONE local decoupling Cap between +V and -V instead of the symmerical pair of capacitors. Also consider making the supply lines lower inductance and shorter.
Or you could add some further RC filtering on the supplies, which is definitly good for the sound in more cases than it is not.
Anyway, there are many possible neat options to have clear grounds and layout.
Sayonara |
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| carlosfm |
Those 47uf caps are there just because the OPA2134 (or similar) NEEDS them.
I'm talking sound quality here. LISTEN to what you do.
Find a way to optimize the layout, but leave them where they are.
If everything is well, the OPA2132 is MUCH SUPERIOR than the OPA2604.
But you have to give it what it likes.
I'm not surprized that some people don't like the 2132.:D
It's only audio.
(c) Jean-Paul
:angel: |
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| rjm |
A star ground, when looked at closely enough, is just a short bus ground and for the beginner often as not turns into a mutant hedgehog with wires poking out every which way from out of a 50g solder ball. And since a few mm can be disastrous, I suggest people first learn enough to be able to wire a bus ground in the right order and then work on making it as small as possible.
For a single non-inverting stage it is really easy:
Front to back, we have: noninverting grounds, inverting grounds, load grounds, bypass grounds, regulator grounds, and power supply grounds. Stick with that and no ground loops will occur even if the power supply grounds or the inputs are shared, as in the VSPS layout.
No ground loops, but lead inductance can be a problem with a long ground bus, just as it is for long lengths of wire in other critical places. So the ground bus has to be as tight as possible between the bypass caps and the load, just as the power lead between the bypass cap and the IC has to be short.
Still the components - espcially through hole - are of a finite size putting a limit to how small everything can be made. And compromises: halving one lead length may more than double another for example.
I'll prioritize the bypass cap lead length and see what can be done in terms of a new layout.
-rjm |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by rjm
A star ground, when looked at closely enough, is just a short bus ground |
If it is THAT then it is NOT a star ground. I usually use multiple star grounds ensuring correct "kelvin returns" (meaning single physically extremely small points where all currents in the relevant loops add to zero) for the local loops. I then "bus" these local stars using low inductance techniques.
| quote: | Originally posted by rjm
For a single non-inverting stage it is really easy:
Front to back, we have: noninverting grounds, inverting grounds, |
Remember, you are in effect amplifying the difference between the two inputs, however especially low impedance feedback networks inject substantial signal currents into the "inverting ground". Bus groudning is thusly entierly inaproriate.
| quote: | Originally posted by rjm
load grounds, bypass grounds, regulator grounds, and power supply grounds. |
These again form current loops with significant signal current impressed and care should be taken how they are arranged. I prefer seperate PSU buses with each rail fully separated and the only "joining" of the various current loops at the load ground, which in effect forms the high level star.
| quote: | Originally posted by rjm
Stick with that and no ground loops will occur even if the power supply grounds or the inputs are shared, as in the VSPS layout. |
Sorry, I can see at least three unwanted current loops that cary signal currents. This is less relevant at low levels (as the currents involved are small) but can lead to plenty of problems even there.
| quote: | Originally posted by rjm
Still the components - espcially through hole - are of a finite size putting a limit to how small everything can be made. |
Hence the best solution is to keep any given curent loop seperate untill it is functionally essential to join them up.
Sayonara |
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| rjm |
| The flying wing approach. |
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| carlosfm |
One cap on each side of the op-amp, please.:dodgy:
And you don't need big 220uf there. |
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| Werner |
You'd better heed Kuei's advice about using CRC filtering after 78/79s. These are noise regulators, and with all-in-one-go phono stages at MC sensitivities, opamp PSRR is mostly an illusion.
The very best single 5534 phonostage I known happens to use a CRC with R a whopping 75 Ohms. Don't remember the cap values. Might be 1000uF and then 100uF. |
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| peranders |
| A golden rule is to keep things compact especially feedback networks. |
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| peranders |
| quote: | Originally posted by Werner
You'd better heed Kuei's advice about using CRC filtering after 78/79s. These are noise regulators, and with all-in-one-go phono stages at MC sensitivities, opamp PSRR is mostly an illusion.
The very best single 5534 phonostage I known happens to use a CRC with R a whopping 75 Ohms. Don't remember the cap values. Might be 1000uF and then 100uF. |
Werner, I agree that more can be done but this was a cheap and simple approach and also for MM pickup. |
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| Werner |
| quote: | Originally posted by peranders
Werner, I agree that more can be done but this was a cheap and simple approach and also for MM pickup. |
And what's the purpose of such a reply? Do we need your agreement on everything here?
And anyway, taken from the original VSPS site"
" a cheap and simple phono section with configurable gain, optional MM or MC loading" |
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| rjm |
| quote: | Originally posted by carlosfm
One cap on each side of the op-amp, please.:dodgy: |
Putting it on the other side would increase the total bypass path length, so, no.
With the new layout, the load ground, bypass ground, and even the + and - input grounds are all connected together within a few mm. (Those who look carefully will note that they were only a little longer than that for the old version, too, only the bypass ground was too far away from the opamp to allow for short connections to the power pins, hence the change.)
The shaded green ground "bus" would be used in the simple case with a 3 wire power cord. The rigorous version for retentive types would just use the green lines, forming an "H" with the connection being made at the bypass caps and requires four wires back to the transformer/diodes.
I'll let someone else experiment with CRC. I mucked around with that ages ago and did not like the results at all. Besides adding components isn't in the design brief.
I agree with Peranders that in general the feedback loop should be as short as possible, but with an active eq its always going to be relatively sprawling. Here, in the interests of a compact ground and bypass lengths I relaxed the feedback length a little, yes.
rjm |
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| rjm |
on the MC loading issue,
One can conveniently increase the gain in the circuit to the point where using it with MC cartridges is feasible.
I recently started using a Denon DL 103 (0.3mV) with the VSPS. I increased the gain to 46db, which isn't much but is plenty for my current system, and changed the load resistor to 1.5k (or whatever). For me, its fine. It might not be optimal (well it *isn't* technically, by all manner of reasons) but its very quiet (no hum and no hiss audible at anything close to normal listening levels) and sounds great.
rjm |
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| Raka |
| quote: | Originally posted by Werner
The very best single 5534 phonostage I known happens to use a CRC with R a whopping 75 Ohms. |
In my PS for a preamp, I used 100Ohm, for the pre, and for the MM stage I took from there another 100Ohm. Yes the voltage drops "a bit" |
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| carlosfm |
| quote: | Originally posted by rjm
Putting it on the other side would increase the total bypass path length, so, no.
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So please don't use the OPA2134.
Stick to the NE5532.:D
You're putting the caps away from the regulators now.:bawling:
They like caps near them.
I agree with the resistor on the PSU, I always use it before the caps on the op-amp.
Although I use smaller values (10~22 ohms).
And I agree also that you should try to shorten the feedback loop, too much lost space there.
If you don't need help for making a simple but decent SOUNDING phono pre, then I don't understand why was this thread started.
Maby you're willing to sell kits of this pre?:devily: |
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| rjm |
This thread has probably run its course. I'd like to thank everyone who contributed. Peer review, loud and chaotic though it might be, is still really helpful for me to add refinements to a design.
I'm particularely impressed with the dicipline shown by people posting to limit suggestions to those which added materially neither to the cost nor the complexity of the project. Fanboy comments like LM79xx suckx, NE5534 suckx were mercifully absent.
Thanks especially to Carlos for reminding me just how sensitive op-amps can be to seemingly inconsequencial layout changes.
The revised layout is shown below. If anyone thinks they can do a better job pm me. The original file is just an MSWord doc and I'd be happy to email it to you to play with to your hearts content. Credit please, though, if you end up using it as a base for your own work.
To them as don't like the grouding: The non-inverting and inverting input share 0.1" of common wire to the load star. And that's deliberate. I challenge you to find any issue more significant.
To them who don't like the position of the bypass caps. If you aren't going to take the trouble to listen to my side of the arguement there is little point, but once again: 10mm of lead at ground potential is equivalent to 10mm at Vcc as far as lead inductance goes, so its the distance from the power pin to the load return that is important, not the physical proximity of the cap to the power pin.
The feedback loop position allows the flexibility to accept caps of various sizes, using MKS or suchlike it could be slightly smaller but not significantly so. It'll never be pin-to-pin 8mm a la gainclone.
CRC is to first order a simple trade of power supply impedance for lower noise. It would likely also damp to insignificance any oscillation due to layout trace inductance of the kind responsible for the quirky dependence of the sound on capacitor position. Aware as I am of the benefits I an not enamoured with the sonic result. I prefer my power to be both low impedance and low capacitance. YMMV as ever.
Hush now, Peace! (or go make your own layout! :) )
Richard |
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| Jianjun Zhou |
| I am from China and very interested in this pre amplifier but i cannot reach the link to the circuit maybe because i am so far from this website. A few days ago i bought a Linn lp-12 and very enjoyed in it's music but i am not satisfied in the preamp, would anybody pls send the circuit to my email: zjianjun11@yahoo.com.cn,thanks a lot! |
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| ebijma |
Is the LM358 usable in this great circuit?
I have one laying around and do want to use for one of my turnables.
It doesn't have to be high end, not for this turntable.
The turntable im talking has a simple mm cardrige.
So no high end needed here.
You can see the datasheet of the LM358 here
http://www.national.com/ds/LM/LM158.pdf
It is used in this mm pre before, but i do not like this circuit
http://members.shaw.ca/roma/twelve.html
I think the best possible option would be your hi-z version.
Hope some of you can help me with this.
Thanks
Erwin |
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| Raj1 |
HI,
Could the ad826 be used or the ad8066? If either of these are used do I need the lo-z parts or the Hi-z types?
Also the output ofset of these types of opamps is usually low, so can the output cap be dispensed with?
Thanks
Raja |
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| PTSOUNDLAB |
Hello Raja,
have you try the AD826 ? It is ok ? I have some AD826, OPA2277, AD823,OPA604, OPA2134,OPA2604, OPA637 to try and I think I will try this simple phono pre with my Dual 522 (I prefer valve pre but this schematic is nice and could be a good thing to do)
Pascal. |
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| ebijma |
Hello everyone,
I have build this simple and very nice sounding phono pre amp.
Got only one problem.
The turntable i have uses a muting circuit when the needle is lifted
of the record or when the arm is traveling.
This i know is not the best option, but i restored it in its original state.
And i want to keep it that way.
But i hear plopping noises when the circuit is activated.
I had two 220nf caps laying around so i thought i give them try and
put one on each input of phono pre amp.
That did the trick.
I hear only one plop when the turntable is switched on.
My question is what would be the best capacity for an input cap?
Hope some of you can help me with this.
Erwin |
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| analog_sa |
| quote: | | My question is what would be the best capacity for an input cap? |
It will depend upon the recommended loading capacitance for your cart and the cable capacitance. |
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| ebijma |
| quote: | Originally posted by analog_sa
It will depend upon the recommended loading capacitance for your cart and the cable capacitance. |
That i don't know.
Its a standard Philips GP330 cardrige.
Nothing special.
The muting is done with a CD4066 Quad analog switch chip.
Can't find info on the cardrige.
Erwin |
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| ebijma |
| Is there no one who can help me with this? |
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| ebijma |
Hello,
Iv'e build this great Phono Pre with the 5532 chip.
Sounds very nice.
I got another question.
I do not like to play records night and day to run (burn) in this Pre.
Isn't it enough to just leave it on? (i wasn't planning on turning it off anyway)
Pleace give me some insite on this.
Bye. |
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| ebijma |
Here it is.
Not much to look at but works great.
Build it all in an old transfomer housing. |
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| rayfutrell |
The correct input capacity is the capacity which causes the Q of the resonant circuit formed by the cartridge inductance, load resistor and the total shunt capacity to be between 0.5 and 0.7.
The formula is Q=Rsquareroot(C/L) where R is the load resistor, C is the total shunt capacity in the cartridge, tonearm wiring, interconnects and preamp and L is the cartridge inductance .
For a Shure V-15 cartridge with about 0H5 inductance, C calculates to be between 65-120pF.
Note that this is less than half of what Shure recommends.
High inductance cartridges are difficult to terminate correctly. Regards,
Ray |
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| mattjk |
I want to built this preamp.
Anyone know where I can find a 1,0nF Polypropylene film and foil cap??? I've tried mouser and digikey. :confused: |
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| ebijma |
| quote: | Originally posted by mattjk
I want to built this preamp.
Anyone know where I can find a 1,0nF Polypropylene film and foil cap??? I've tried mouser and digikey. :confused: |
Hello Mattjk,
Just build the lo - z version, you can find it here.
http://www.geocities.com/rjm003.geo...o/diy_pho5.html
I could not get some of the parts for the hi - z version, so i build the lo - z version those parts are easy to get.
It sounds very nice.
It's playing now for about 4 weeks and sounds much better then in the beginning.
Im very happy with this phono pre, and im playing my old records on a dayly basis now.
Good luck on building this pre. |
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| mattjk |
Thank you! I will build the lo version. What did you use for R3?
Matt |
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| ebijma |
| quote: | Originally posted by mattjk
Thank you! I will build the lo version. What did you use for R3?
Matt |
Hello again mattjk,
For R3 i just used the Lo - z rating of 1 kohm.
This works for me. |
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| mattjk |
| ok, this is annoying. now I can't find the 3.3n and 10n 1% caps. |
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| ebijma |
| quote: | Originally posted by mattjk
ok, this is annoying. now I can't find the 3.3n and 10n 1% caps. |
Sorry can't help you there.
I live in Europe. |
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| enochRoot |
are good sources. you have to search for .0033uF though. that's the trouble i found. some are listed as 3.3nF. some are 3300pf and some are .0033uF. there are 1% values stocked of the 10nF, but the 3.3nF you have to get 2% ones, and hand match them. it is pretty easy w/ a decent hand-held dvm that reads capacitance. the absolute value might not be on, but you should be able to get closely matched pairs. i bought 10 caps, and matched out pairs rather easily. not sure which brands were which...but if you search mouser for the .0033uF 2% you should find them. same w/ .01uF and 1%.
hope this helps. i'm actually building another of richard's designs that uses the same cap values ;) |
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| mattjk |
ahhhh, thank you!
Is this OK?
Mouser Part #: 140-PF2A332F Page 508
Mfr. Part #: 140-PF2A332F Data Sheet
Mfr: Xicon
Category: Polyester Film Capacitors
Description: Xicon 2% Radial Polyester Film Capacitors CAP 100V .0033uF
I know he calls for polypropylene...
The other cap is:
Mouser Part #: 594-2222-460-41003
Mfr. Part #: 222246041003
Mfr: Vishay/BC Components
Category: Film Capacitors
Description: Vishay/BC Components Film Capacitors .01UF 63V 1% |
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| enochRoot |
| those are the exact ones i bought. i bought a number of different kinds, and think i got some from digikey as well. i went to check the amp...and i ended up using some 400v jobbers from bc components. might be that they were polypropolene, and the others were polyester. sorry...can't remember as it has been a while. maybe check digikey too. they might have been lower tolerance, but as i said...i matched them here. they were cheap enough that buying 10 didn't break the bank ;) |
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| mattjk |
thanks!!
I hate ordering all these parts :smash: want to build one for me and I'll pay you? ;)
I can't find the rectifier diodes either :( |
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| enochRoot |
| come on man...finding the parts and ordering them is half the fun :D |
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| bg40403 |
| Mongo like hunting and gathering. Satisfy primal urge |
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| toseland |
RJM
How does the VSPS Ultra compare in sonic terms with the VSPS with increased gain when using the DL103?
-Bernard |
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| maxw |
Newbie question: Is my Stanton 500 AL II a MM or MC cartridge?
I will make this phono pre :) |
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| Geek |
| According to the specs, MM. |
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| ebijma |
| quote: | Originally posted by maxw
Newbie question: Is my Stanton 500 AL II a MM or MC cartridge?
I will make this phono pre :) |
Hello maxw
The vsps is should work fine with a Stanton 500.
Nice homepage by the way.
You did a good job on your gainclone.
Sorry to see you destroyed the looks of you turntable. |
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| maxw |
| quote: | Originally posted by Geek
According to the specs, MM. |
I am not saying your wrong but where on that page does it say its MM? just curious as I looked at pages like that before I asked. Maybe the "Samarium Cobalt magnet" bit?
| quote: | Originally posted by ebijma
The vsps is should work fine with a Stanton 500.
Nice homepage by the way.
You did a good job on your gainclone. |
Thank you :)
| quote: | Originally posted by ebijma
Sorry to see you destroyed the looks of you turntable. |
LOL! I bought it when I was 14, stickers were cool back then:clown: |
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| Geek |
| quote: | Originally posted by maxw
I am not saying your wrong but where on that page does it say its MM? just curious as I looked at pages like that before I asked. Maybe the "Samarium Cobalt magnet" bit? |
The output impedance and output level. 47K ohms and 4.7mV is indigenous to a MM cartridge. An MC wouldda said like 120 ohms impedance (or something low thereabouts) and perhaps 500uV output. Though there are some high-output MC carts..... |
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| maxw |
| quote: | Originally posted by Geek
The output impedance and output level. 47K ohms and 4.7mV is indigenous to a MM cartridge. An MC wouldda said like 120 ohms impedance (or something low thereabouts) and perhaps 500uV output. Though there are some high-output MC carts..... |
Thanks Geek. You learn something new every day ;) |
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| Geek |
You're welcome.
You and I both - I learned that here too :) |
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| maxw |
What kind of caps are C1-3?
I assume from the diagram that C3 is non-polarised electrolytic and C1 and 2 are? |
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| ericpeters |
I want to modify my VSPS to be able to drive my AT-OC9 without transformer.
This will run only for a few month because I'm assembling a Pass ONO clone but this takes some time.
I built my VSPS using a OPA2134 and have about 10 of them laying around.
Can I simply put another OPA2134 before the input of the VSPS?
I assume removing R1, connecting the output of the new 2134 to the non inverting input of the existing one. Similar like this mini circuit from the WIKI
And put a 100ohm load resistor on the input of the new opamp?
and if so what resistors should i use for a 20 to 30db extra gain? |
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| ebijma |
Hello again,
I just wanted to share the upgrade i did on my own VSPS.
I used cheap monacor mkp capacitors of 4.7uf for the output.
And the sound was so nice. :-)
I could get my hands on Black gate non polarity 4.7uf capacitors.
Some of you wrote here on the forum that they sound very good.
So i removed the monacors and placed the black gates.
First listing impressions are very bad. :-(
No depth and the sound is very bright.
I know the capacitors have to run in.
Strange thing is that the monacor capacitors sounded nice when they where brand new.
The Black gates sure don't.
Hope they will improve in a couple days. |
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| ericpeters |
Well no one answered my question so I had to figure "something" out myself.
The board I used was too small to add another opamp.
So I halved the R2 to get some more gain (just enough)
But now I had a very thin sound, I figured this had to do with the input load resistance. Looking at some other schematic's I noticed that most opamp based MC head-amps (at least the simple ones I've seen) had no load resistance so I cut R1 (used to be 47k) from the board.
Now I have a reasonable sound, just enough to get me through the "Ono Clone" assebling period.
I tend to think this is all easier as I used to think before but It's probably better to think I've just been lucky. |
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| ebijma |
| quote: | Originally posted by ebijma
Hello again,
I just wanted to share the upgrade i did on my own VSPS.
I used cheap monacor mkp capacitors of 4.7uf for the output.
And the sound was so nice. :-)
I could get my hands on Black gate non polarity 4.7uf capacitors.
Some of you wrote here on the forum that they sound very good.
So i removed the monacors and placed the black gates.
First listing impressions are very bad. :-(
No depth and the sound is very bright.
I know the capacitors have to run in.
Strange thing is that the monacor capacitors sounded nice when they where brand new.
The Black gates sure don't.
Hope they will improve in a couple days. |
After listening a couple days, the sound improved allot.
Sound is more natural, depth came back and the highs are velvet like.
I prever the blackgates now.
And as a bonus the blackgates non polar capacitors are much smaller then any other good 4.7 uf capacitors.
So you can build a smaller amp.
http://again.at/bijma
Homepage is not ready yet but if you click on the button hobby, you'll find a photo gallery of my VSPS.
It's not most beautifull casing but it works for me. |
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| maxw |
I am making a single sided PCB for this design that uses 2x OPA637.....but I am having trouble knowing what capacitors to choose.
Mine will be high-Z so:
C1 - 330p
C2 - 1.0n
but I dont know what types to get. I can see from the photos on http://www.geocities.com/rjm003.geo...o/diy_pho5.html that they look kind of like green caps (Metallised Polyester) but then in ebijma's pics they look like box caps which are MKT (polyester) ???
does it matter?
Can someone point me in the right direction?
I will be using http://www.jaycar.co.nz/ as a source for components ;) |
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| ebijma |
| quote: | Originally posted by maxw
I am making a single sided PCB for this design that uses 2x OPA637.....but I am having trouble knowing what capacitors to choose.
Mine will be high-Z so:
C1 - 330p
C2 - 1.0n
but I dont know what types to get. I can see from the photos on http://www.geocities.com/rjm003.geo...o/diy_pho5.html that they look kind of like green caps (Metallised Polyester) but then in ebijma's pics they look like box caps which are MKT (polyester) ???
does it matter?
Can someone point me in the right direction?
I will be using http://www.jaycar.co.nz/ as a source for components ;) |
I didn't use the best caps for the RIAA and i use a input cap of 1uf.
I need the in input cap because the turntable i have uses a cd 4066 to turn of the sound when the arm is traveling. I could hear hard pop when the circuit is activated. With a input cap there's no pop.
And i didn't us regulators because with this transformer the rail voltage is +/- 12,4 volts.
But i did use snubbers in the power supply.
It's not the best config for the sound, but it sure sounds great. |
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| maxw |
| quote: | Originally posted by ebijma
I didn't use the best caps for the RIAA and i use a input cap of 1uf. |
But still what type of caps should I use? Greencap or MKT box shaped ones? |
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| ebijma |
| quote: | Originally posted by maxw
But still what type of caps should I use? Greencap or MKT box shaped ones? |
What you should use is totaly up to you.
For the RIAA i used MKT folie ones ( don't know the brand ), for the input 1uf MKT wima and for the output Blackgate 4.7uf non polar.
And i build the lo-z version.
I also put one 100nf wima on each power rail close to the chip.
Hope this answers your question. |
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| maxw |
| quote: | Originally posted by ebijma
What you should use is totaly up to you.
For the RIAA i used MKT folie ones ( don't know the brand ), for the input 1uf MKT wima and for the output Blackgate 4.7uf non polar.
And i build the lo-z version.
I also put one 100nf wima on each power rail close to the chip.
Hope this answers your question. |
I think maybe I thought it was more critical than it was :cannotbe:
I will use the MKT one, they look better.
Thanks for your help ebijma. |
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| DJNUBZ |
I am thinking about making this my first electronic DIY project. I would like to build the high Z version. The needles I will be using are these.
http://www.needlz.com/cartridges/m44g.asp
On the site it says that the load should be "47 kilohms in parallel with 450pf " does this mean I should hook up a 450pf cap in parallel with the R1?
I plan on building one for practice then I might build two in an enclosure to use with my Vinyl DJ setup.
Before I go and order parts is there anything I should be aware of? |
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| maxw |
| quote: | Originally posted by DJNUBZ
Before I go and order parts is there anything I should be aware of? |
If you have your TTs going through one of these you would then need to use a line input on your mixer instead of the phono input ;) |
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| DJNUBZ |
| you don't have to insult my intelegence. I know electronics. I just havn't built any electronics. |
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| Variac |
:cop: If you ask for help, then you shouldn't assume that someone is insulting you when they try to help you. Sometimes its hard to tell what background people have.
Best to keep a positive attitude:D |
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| DJNUBZ |
Sorry I should of said
you don't have to insult my intelegence:)
on a side note I am going to do this in hopes of getting a much better sound out of my mixer. Do you guys feel that this phono pre will be a step up from the one in my mixer? |
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| maxw |
| quote: | Originally posted by DJNUBZ
you don't have to insult my intelegence. I know electronics. I just havn't built any electronics. |
Dude chill out :D Just trying to help. I dont want you to build it and then find out you have to sacrifice an input from a CD to use it ;)
| quote: | Originally posted by DJNUBZ
on a side note I am going to do this in hopes of getting a much better sound out of my mixer. Do you guys feel that this phono pre will be a step up from the one in my mixer? |
Depends what mixer you have. Why dont you open it and see whats inside? You will probably find its based on dip8 opamps just like this design so maybe you could upgrade them to higher quality ones like in most CD players....(although my vestax wasn't like this). |
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| DJNUBZ |
Its a umx-9. I really would like a bozak,urei, or rane rotary mixer but I don't have the $$$.
I am pretty sure a good pono pre will be better then whats in my mixer. |
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| maxw |
| quote: | Originally posted by maxw
But still what type of caps should I use? Greencap or MKT box shaped ones? |
Got them today....I think I was thrown by the size of the ones in the pics but that is in the low-Z version which has bigger values so they are bigger (I think). I could only get ceremic caps in as low as 330p. If no one see any prob with these caps then I will design the PCB tonight. |
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| ebijma |
| quote: | Originally posted by maxw
Got them today....I think I was thrown by the size of the ones in the pics but that is in the low-Z version which has bigger values so they are bigger (I think). I could only get ceremic caps in as low as 330p. If no one see any prob with these caps then I will design the PCB tonight. |
Sound quality wise i should use MKT ones or better.
But he..... there's no harm trying it with ceremics.
You can always upgrade. I did. |
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| maxw |
| still haven't finalised the cap pin spacing yet. |
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