Anyone built the phono pre from LM4562/LME49720 datasheet?

[defec]

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?

[ahaja]

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

[defec]

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?

[ahaja]

>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

[jackinnj]

Dead bug style:

[defec]

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

[ahaja]

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