Building a phono preamp with noise filters

[vmscbe1974]

Dear friends

Iam interested to build a phono preamp(mm) with noise filters specifically for 78 rpm shellac records .I need guidance to source for RIAA circuit ,and noise filters circuit to remove surface noise, hiss,rumble and equaliazation above 6khz for shellac records. On googling i did find some circuit diagrams but wondering how to interlace them and is any transformer needed for the necessary amplication at the output stage.

My end result of the preamp is to signal out clear music to a good amplifier.Which is the best signal to noise ratio and how do i achieve it?

Kindly guide me.
Regards
srinivasan

 

[GeorgeO]

You need to do some more research and get more knowledge if the intention is to do it yourself. Hagerman Technologies has a forum on Audio Circle, I think, where you may be able to learn more, I suggest you check it out and ask questions. Since it is dedicated to this subject, newbie questions are often posed there and many experienced people can comment.His company makes well regarded phono stages in kit form, and a couple of friends have them and are happy users.

 

[arindamcc]

Dear friends

Iam interested to build a phono preamp(mm) with noise filters specifically for 78 rpm shellac records .I need guidance to source for RIAA circuit ,and noise filters circuit to remove surface noise, hiss,rumble and equaliazation above 6khz for shellac records. On googling i did find some circuit diagrams but wondering how to interlace them and is any transformer needed for the necessary amplication at the output stage.

My end result of the preamp is to signal out clear music to a good amplifier.Which is the best signal to noise ratio and how do i achieve it?

Kindly guide me.
Regards
srinivasan

With earlier LPs (some record companies didnt use RIAA before 1960), this curve is not correct. The cutting equalizations on all 78 RPMs and LPs before 1955 have been very different. 78rpm records in particular used curves very different from the RIAA curve. For this reason, you should not use the RIAA phono input on your amplifier if you want good quality reproduction of 78rpm records.

 

[Hiten]

Hello Srinivasan,
Rumble noise may not be that much a problem if your speakers can't produce below 20hz. Also good quality turntable with heavy platter will dampen the rumble noise. I did experimented with as simple circuit as putting a pot parallel to input of pre amp. Cranky (Former member) posted very good info in this thread.. http://www.hifivision.com/phono-turntables/9229-experimenting-high-pass-filter-old-turntable.html but now those posts are gone.. :sad:

few more links and circuits to learn...
Practical Transistor Circuits , Low-pass filters : FILTERS
if you are fan of 78 rpm records few other options I would suggest try to hook it up with an old valve radio or amp. Sounds too good. OR Some old amplifiers had subsonic filter for this purpose only. As I have around fifteen 78 rpm records (classical etc.) I will be also interested so please do keep us informed.

 

[anilva]

Dear friends

Iam interested to build a phono preamp(mm) with noise filters specifically for 78 rpm shellac records .I need guidance to source for RIAA circuit ,and noise filters circuit to remove surface noise, hiss,rumble and equaliazation above 6khz for shellac records. On googling i did find some circuit diagrams but wondering how to interlace them and is any transformer needed for the necessary amplication at the output stage.

My end result of the preamp is to signal out clear music to a good amplifier.Which is the best signal to noise ratio and how do i achieve it?

Kindly guide me.
Regards
srinivasan

My advice is that you need to attempt building a Phono preamp, only if you have built few preamps before. The reason I am saying this is because phono preamps, tape head preamps etc. are pretty high gain designs and are quite susceptible to hum, noise and RF interference. The PCB design also is very critical, because small capacitances on the PCB track and component leads can turn the preamp into an AM radio.

But, if you are upto it, there are many designs both discrete and OPamp based available. Check ebay. There are many kits. They are fairly risk proof.

Cheers.