Pacific Riaa

codge · 3rd November 2010, 09:53 AM

Hi, i've been looking at the threads about the pacific Riaa Phono amp and i would like to build it on a tag strip. I have attached the layout, could someone tell me if it looks correct, and point out any errors for me to correct.

regards

pre2.jpg

DF96 · 3rd November 2010, 04:13 PM

Remove the ground trace from the bottom of the 470nF capacitor.

codge · 3rd November 2010, 04:22 PM

Thanks for the feedback

regards

pre.jpg

DF96 · 3rd November 2010, 05:09 PM

By the way, the LF poles in this RIAA circuit are not particularly accurate. Maybe someone has adjusted it 'by ear' or using an inverse network instead of calculating it properly? Time constants should be 3180:318:75us - I calculate 2438:294:76. This means that bass-mid (below 500Hz) will be boosted by 0.7dB, but will roll off from 65Hz instead of 50Hz. It is not worth using lots of parallel capacitors to make up an exact inaccurate value!

The simplest way to improve it is to change the second gate resistor from 100K to 470K. Alternatively, move the 100K resistor from the second gate to the junction of the 0.47uF and 27K resistor. The first capacitor bank should be 106nF (0.1uF may be close enough), and the second should be 27.7nF (27nF is close enough).

The input resistor ought to be 47K for most MM cartridges.

codge · 3rd November 2010, 08:22 PM

Thanks for the info, i will try your suggestions.

regards

codge · 4th November 2010, 11:53 AM

Thanks for the help.

revisedpacific.jpg

3rd November 2010, 09:53 AM	#1
codge diyAudio Member Join Date: Mar 2010	Pacific Riaa Hi, i've been looking at the threads about the pacific Riaa Phono amp and i would like to build it on a tag strip. I have attached the layout, could someone tell me if it looks correct, and point out any errors for me to correct. regards pre2.jpg

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
Need help with power supply for Pacific RIAA	Dmeister	Analogue Source	11	10th September 2010 10:58 AM
Hello from the Pacific NW!	Brian44	Introductions	4	7th May 2008 08:12 PM
Riaa Pacific Jfet	maxpou	Analogue Source	23	15th April 2006 05:51 PM
RIAA Pacific deluxe from Elektor	peranders	Analogue Source	4	26th February 2004 03:52 PM
Pacific Microsonics PMD200?	A 8	Parts	2	30th March 2003 02:39 AM

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


	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

3rd November 2010, 04:13 PM	#2
DF96 diyAudio Member Join Date: May 2007	Remove the ground trace from the bottom of the 470nF capacitor.

3rd November 2010, 04:22 PM	#3
codge diyAudio Member Join Date: Mar 2010	Thanks for the feedback regards pre.jpg

3rd November 2010, 05:09 PM	#4
DF96 diyAudio Member Join Date: May 2007	By the way, the LF poles in this RIAA circuit are not particularly accurate. Maybe someone has adjusted it 'by ear' or using an inverse network instead of calculating it properly? Time constants should be 3180:318:75us - I calculate 2438:294:76. This means that bass-mid (below 500Hz) will be boosted by 0.7dB, but will roll off from 65Hz instead of 50Hz. It is not worth using lots of parallel capacitors to make up an exact inaccurate value! The simplest way to improve it is to change the second gate resistor from 100K to 470K. Alternatively, move the 100K resistor from the second gate to the junction of the 0.47uF and 27K resistor. The first capacitor bank should be 106nF (0.1uF may be close enough), and the second should be 27.7nF (27nF is close enough). The input resistor ought to be 47K for most MM cartridges.

3rd November 2010, 08:22 PM	#5
codge diyAudio Member Join Date: Mar 2010	Thanks for the info, i will try your suggestions. regards

4th November 2010, 11:53 AM	#6
codge diyAudio Member Join Date: Mar 2010	Thanks for the help. revisedpacific.jpg

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