Anyone built the phono pre from LM4562/LME49720 datasheet?

Ahaja, Thank you. I had some 100ohm resistors on hand so I installed them and it helped out. Are both methods to raise the gain that you listed equal or is one better than the other?

Do you recall the resistor values that you used in the variable gain dip that you installed in your build? I plugged in a Goldring 1042 and now it sounds pretty good. almost wish I even had a bit more gain:). How far can I push this until I have to worry about distortion?
 
If you need more gain change both 150R to 82R. This gives you about 44/45dB total gain. I think it would be sufficient for Goldring 1042. 1042 output - 6,5mV it is rather high ... that's why it seems dynamic compared to lower output cartridges ;-).

Both methods gives you more or less equal value of total gain.
The best is to try both and decide which one is the best for you.

I rather prefer more gain in first stage and less in output stage. In my preamp output stage is with lme49713.
I don't remember what values I used ... I have to check it ... if I got any data in my computer ;-). For gain I used 12 positions rotary dip switch. It gives me possibility to change the gain from 39 ... 51dB for MM/MC HO cartridges.

Here Gain and loss - damping and amplification in dB voltage power conversion - field and energy parameter - sengpielaudio Sengpiel Berlin is calculator.

You can place in your preamplifier a dip switch (4...8...12) positions for setting the R loading. It's very audible.

Krzysztof
 
Ahaja, thank you so much for the much appreciated help. I kept 100ohm resistors in the second stage and used a 60 in the first and now the gain seems great. I am getting a good amount of dc offset though. How tight do the non RIAA resistors have to match each other when used with a LM4562?
 
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>Defec
OK. :)
It gives you about 45dB total gain.

Resistors in NFB are set for low noise.
If you got trouble with dc offset you can place capacitors (bipolar) after the RG to ground (see my drawing in post 17).
Here: RC pad corner frequency cutoff calculation calculate filter time constant tau RC voltage power calculator capacitance resistance - sengpielaudio Sengpiel Berlin you can calculate these RC filters.
After 100R I would start with 220/330uF and after 60R I would start with 330/470uF.

Another way is to place output capacitor after the second stage.
1-4,7uF (polypropylen) and after this a resistor 33-47k to ground (check RC calculations like I wrote earlier).

Both metod are cheap, simple and works good.

What type is your power supply?

Krzysztof
 
Ahaja, thanks for the advice and links. Okay, I have some 2.2uf caps around that I'll install on the outputs so I'll have the opamp's output to a 100ohm resistor, I couldn't find any 47ohm around the house, then to a 2.2uf film cap and a 33k from it's out to ground. I'll try your other method of putting the NP caps from the 60/100ohm resistor to ground soon but I have to order the capacitors.

For the power supply I borrowed Jim Hagerman's Bugle power supply

http://www.hagtech.com/images/powersupply.gif

If I want to add a new stage after the final phono stage to be a rumble filter etc how'd I deal with the DC blocking capacitor and output resistors? Do I just move it to the output of the new stage? Is it okay for the new stage to see the DC offset? Also between the final stage of the phono do I put anything between it and the rumble stage or just have it wired right into it?

Thanks again for all the help. I'm learning a lot and having fun
 
Power supply is very important in phono stages.
Hagtech's psu is OK for start.
You can check other options of voltage stabilization:
- lm317/337 (after them you can add finesse regulator from wenzel site)
- emiter follower with zeners - very simple and very good
- shunt regulators - best for me

Rumble:
as I wrote earlier if you add a caps after RG you create natural RC filter.
First you get a low offset this way; second - rumble filter.
It's only -3dB but works OK. You can calculate values of these capacitors to get desirable cut off frequency. If you use this method you don't have to use output capacitor.

Active rumble:
You may leave these output caps as they are. And add addictional active stage for rumble switchable. Then if you must use it - turn it on, and if not - turn off.
The best is to use exactly as many stages as needed.

Rane Corporation has good www - many usable informations, projects and schematics.

Check also this site: DIY Homepage for inspirations.

Krzysztof
 
Hey,

I've built the LM4562 datasheet RIAA preamp, too.
Used Beyschlag resistors (and Dale in the feedback loop), Wima FKP 1% film-foil and silver-mica RIAA caps, C0G SMD and Elna Silmic II bypass caps. The PSU is a double emitter follower with TL431 voltage reference.

It sounds excellent, dynamic, fast, detailed and natural. I'm very satisfied with it, I think I'll keep it for years.
 

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I´ve been looking att this amp but schematis calls for different values for tha same component. For ex the resistor between to ops´s is set to be 26,1k + 909? And one capacitor has tree values, 22nF, 4.7nF and 500pF. Could someone explain this please?
 
Hi FdW,

I had a look on your modified circuit. I like it very much. I missed here the balanced input and the DC offset compensation. The DC power supply filtering with OPA is a wonderful idea.
Although I wanted to build a simply phono amp, but I will consider your idea.
Thanks,

Szabolcs
 
It is not a 'TRUE'-balanced input but a 'pseudo'-balanced version :)
(there is no 'ground' connection on the cartridge)

It functions good, it has had several auditions (mostly with a German audio designers and builders club, but also others), it got very good comments :)
 
Dear Frans,

The most problematic (lowest level) part is symmetric, so it is good from this poinf of view.
There is no capacitor in the signal direct route - also a good sign.

Since I ordered the 79720s I will not able to use your PCB. But I will use parts of your schematics; the DC offsetting and balanced input.

First I will build a simplier power side - keep it simple - (with LC filter and Transistor based noise reduction)
(Since I've ordered some quite low noise regulator lp5907 (unfortunately with low voltage 3,3V) - I'm considering to apply them wiht spearting the first stage power from the 2nd - where the signal is definitely much higher.)

Since China delivery is although cheap, but slow, I have plenty of time to finalize everything :) Thanks for the support.
I will post the result.

Szabolcs
 
Here is a set of links to the MPP thread, this is where I designed a shunt supply (I think there are near 600 builds).

Comparing results between 2 PSU on different RIAA-amps is difficult (if not impossible), so you need to select one.

Maybe it is best to first build an simple PSU like the opamp one, and then progress to a more evolved one like the one in the MPP thread.

These are the most important/relevant messages regarding PSU and Pre-Reg (that I collected).
  1. Mpp #4375 PSU-pre-regulator.
  2. Mpp #4610 V2 Schemas UPS and Amp.
  3. Mpp #6506 CCS fine-tuning.
  4. Mpp #6462 PSU with my notes.
  5. Mpp #6809 Do not try to feed the CVS of the CCS of the shunt with a regulated power supply.
  6. Mpp #7127 More about transformer selection.
  7. Mpp #7635 Single and dual transformer wiring (also corrected drawing) (See also #7733).
  8. Mpp #7733 Grounding (PSU, RIAA and Player).
  9. Mpp #7810 35V PSU for the CroMagnon.
  10. Mpp #7830 The PSU explained.
  11. Mpp #8386 My resistor recommendation�s.
  12. My Paradise #56 PSU Noise.
  13. Masterpiece #951 That's not a PSRR test (it's a CIR test) :)
  14. PradiseBuilders #13 Schema's and assembly guide.
  15. PradiseBuilders #155 Vdc input voltage minimum simulated.
  16. PradiseBuilders #970 PSU oscillates; posible solutions?
  17. PradiseBuilders #983 Compensating the PSU for oscillations.
  18. PradiseBuilders #1173 Fixing oscillations (up to #1182).
  19. PradiseBuilders #1322 Fuse :).
  20. PradiseBuilders #1387 Updated Paradise R3 assembly guide (Also German).
  21. PradiseBuilders #1403 Capacitors bad vs good.
  22. PradiseBuilders #1593 PSU Power Transistor selection.
  23. PradiseBuilders #1644 PSU Output Impedance.
  24. PradiseBuilders #1680 PSU Power Supply Suppression Ratio(PSSR).
  25. PradiseBuilders #1772 NJF selection for the PSU.
  26. PradiseBuilders #1887 Empirical NJF Rgs determination.
  27. PradiseBuilders #2127 More about the PSU fets (J113's etc).
  28. PradiseBuilders #2969 About the Paradise PSU using Calvin buffers.
  29. PradiseBuilders #3134 More ESR confusion :).
  30. PradiseBuilders #3808 Werner's PSU fix.
  31. PradiseBuilders #3830 PSU oscillating due to 'missing' input buffer/capacitors.
Have a look at these and their following messages.
 
It is not a 'TRUE'-balanced input but a 'pseudo'-balanced version :)
(there is no 'ground' connection on the cartridge)
........................
A ground connection is not required in a balanced interconnect system. In fact a balanced interconnect system does not have a ground wire. The system may or may not have a shield which may or may not be connected at the receive end. Witness recent pro audio interconnects using unshielded Cat5 cable.

However a phono cartridge cable should have a shield connected at both ends.
 
A ground connection is not required in a balanced interconnect system. In fact a balanced interconnect system does not have a ground wire. The system may or may not have a shield which may or may not be connected at the receive end. Witness recent pro audio interconnects using unshielded Cat5 cable.

However a phono cartridge cable should have a shield connected at both ends.

Yes, Yes and Yes (as in the referred schematic) :)