Phono preamp without confusing RIAA stuff

PhantomBox · 11th February 2010, 06:03 PM

Hi.
I'm aware of the million threads on the famous RIAA phono preamp with all the re- de- pre-emphasis discussions, and I really got tired of searching the internet and not finding anything useful.
I just built one of those (google "PAiA - RIAA phono preamp kit" and the schematic pops up) and it works but it has the characteristic EQ curve with lots of treble and no bass.
I wonder if it is possible to built one of those preamps with a usable EQ curve that amplifies exactly the same sound that come off the record and converts it to line level or even a balanced line level as those used in professional mixing consoles?
Thanks in advance for any reply.
Phantombox

janneman · 11th February 2010, 07:37 PM

Quote:

Originally Posted by PhantomBox

Hi.
I'm aware of the million threads on the famous RIAA phono preamp with all the re- de- pre-emphasis discussions, and I really got tired of searching the internet and not finding anything useful.
I just built one of those (google "PAiA - RIAA phono preamp kit" and the schematic pops up) and it works but it has the characteristic EQ curve with lots of treble and no bass.
I wonder if it is possible to built one of those preamps with a usable EQ curve that amplifies exactly the same sound that come off the record and converts it to line level or even a balanced line level as those used in professional mixing consoles?
Thanks in advance for any reply.
Phantombox

What exactly is the problem? What do you mean by "it has the characteristic EQ curve with lots of treble and no bass"? Is the RIAA in error?

jd

AuroraB · 11th February 2010, 08:16 PM

Just off the top of my head , I can't see anything wrong with that schematic...
If you built it , are you sure you didn't mix up some of the parts? I've built several 5532 based RIAA pre's to be used with radio mixers without any problems - sounds quite OK. Maybe not super-duper Hi End, but actually very much OK

PhantomBox · 11th February 2010, 08:16 PM

What I mean is that the preamp that I built is exactly to specifications according to the schematic, and unless I made the same mistake on both channels (L + R) and my preamp don't "de-emphasizes", then I'd say that the RIAA is in error.
Fortunately I'm not such a square-head... Let me check my design over again, see if I really missed something.

janneman · 11th February 2010, 09:17 PM

Quote:

Originally Posted by PhantomBox

What I mean is that the preamp that I built is exactly to specifications according to the schematic, and unless I made the same mistake on both channels (L + R) and my preamp don't "de-emphasizes", then I'd say that the RIAA is in error.
Fortunately I'm not such a square-head... Let me check my design over again, see if I really missed something.

But how do you know it is in error? Did you measure? Does is sound somehow wromg? What's the problem?

jd

Joachim Gerhard · 11th February 2010, 09:22 PM

One little problem could be that this circuit has a rising response over 20kHz. A passive RC combination at the output can solve that. Another could be component tolerances. This DIY kit is dirt ceap so i do not expect close tolerance parts.

leadbelly · 11th February 2010, 09:31 PM

This might seem like a silly question, but you are using a turntable with no preamp in it and an input on the power amp that's not a phono input, right? You might want to tell us the signal chain in any event.

chili555 · 11th February 2010, 09:46 PM

A phono preamp without the confusing RIAA stuff would not correctly reproduce the signal on the record.

RIAA equalization - Wikipedia, the free encyclopedia

PLB · 11th February 2010, 10:20 PM

Hi PhantomBox,

I just entered the "PAiA - RIAA phono preamp kit" schematic into a Spice simulation program and it shows that at 20Hz the response is about 4dB less than the RIAA curve and at 20KHz it's about 4dB higher than the RIAA curve.

Regards

Peter

Joachim Gerhard · 11th February 2010, 10:23 PM

that whould explain the sound: no bass, too much treble. I expected the DC blocking cap to small and the circuit can not reduce the gain to zerro in the treble.

11th February 2010, 06:03 PM	#1
PhantomBox diyAudio Member Join Date: Jan 2008	Phono preamp without confusing RIAA stuff Hi. I'm aware of the million threads on the famous RIAA phono preamp with all the re- de- pre-emphasis discussions, and I really got tired of searching the internet and not finding anything useful. I just built one of those (google "PAiA - RIAA phono preamp kit" and the schematic pops up) and it works but it has the characteristic EQ curve with lots of treble and no bass. I wonder if it is possible to built one of those preamps with a usable EQ curve that amplifies exactly the same sound that come off the record and converts it to line level or even a balanced line level as those used in professional mixing consoles? Thanks in advance for any reply. Phantombox

11th February 2010, 08:16 PM	#3
AuroraB diyAudio Member Join Date: May 2001 Location: Norway, -north of the moral circle..	Just off the top of my head , I can't see anything wrong with that schematic... If you built it , are you sure you didn't mix up some of the parts? I've built several 5532 based RIAA pre's to be used with radio mixers without any problems - sounds quite OK. Maybe not super-duper Hi End, but actually very much OK __________________ While the Lie leapt from Bagdad to Constantinopel, the Truth was still looking for it's sandals!

11th February 2010, 09:31 PM	#7
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	This might seem like a silly question, but you are using a turntable with no preamp in it and an input on the power amp that's not a phono input, right? You might want to tell us the signal chain in any event. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Simple Single Supply Phono RIAA opamp preamp	audiomodder	Analogue Source	12	23rd December 2009 09:47 PM
Noise on the RIAA phono preAmp	diarav	Chip Amps	3	23rd March 2007 05:27 AM
RIAA phono stage	KevinTams	Tubes / Valves	10	16th May 2005 01:05 PM
Tubed RIAA phono stage	shif	Analogue Source	7	30th June 2004 06:22 PM
RIAA phono preamp using single ECC83	DJG	Tubes / Valves	19	29th March 2003 02:27 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

11th February 2010, 09:22 PM	#6
Joachim Gerhard diyAudio Member Join Date: Mar 2009	One little problem could be that this circuit has a rising response over 20kHz. A passive RC combination at the output can solve that. Another could be component tolerances. This DIY kit is dirt ceap so i do not expect close tolerance parts.

11th February 2010, 09:46 PM	#8
chili555 diyAudio Member Join Date: Nov 2009 Location: South Carolina, by the lake	A phono preamp without the confusing RIAA stuff would not correctly reproduce the signal on the record. RIAA equalization - Wikipedia, the free encyclopedia

11th February 2010, 10:20 PM	#9
PLB diyAudio Member Join Date: Sep 2008 Location: The backbone of England	Hi PhantomBox, I just entered the "PAiA - RIAA phono preamp kit" schematic into a Spice simulation program and it shows that at 20Hz the response is about 4dB less than the RIAA curve and at 20KHz it's about 4dB higher than the RIAA curve. Regards Peter

11th February 2010, 10:23 PM	#10
Joachim Gerhard diyAudio Member Join Date: Mar 2009	that whould explain the sound: no bass, too much treble. I expected the DC blocking cap to small and the circuit can not reduce the gain to zerro in the treble.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read