P170 Power Amp My First Post

[13oots2]

Have managed to upograde my MF P170 with help from a couple of other posts in this forum. So far have replaced the LM318 opamps with opa627 by disconnecting pins 1,5,8 and the improvement is very noticable.

Next up is how to fit my replacement 22000uf 63v caps, have idea on how to fit them and will report on my progress.

This is a big thank you to the previous posts on the P170 that have enabled me to do the upgrades so far.

Mark

[13oots2]

Update to my last post, have replaced all the electolytics on the board and am stunned at the difference it has made. Perhaps it is the upgrade feeling kicking in but everthing now seems louder and clearer, stereo separation seems much improved too.

A word of caution to anyone working on this amp, despite being as careful as possible using solder wick and not rushing the job, several tracks started to lift and I had to use point to point wiring on one solder joint.

Also I bought myself a capacitance meter and matched values as closely as possible for each channel. Perhaps a little over the top but it pleased me to do it, I also seem to have been rewarded with very good stereo balance. All caps were slighly overated for voltage and 105c.

Looks like I have been bitten by the DIY bug and my MF 3b is up next, followed by an A1 that I bought on Ebay for a good price due to it having an intermittent channel. The caps in the A1 look in a shocking condition so am hoping replacing them will cure the problem

[whats gan on]

hi mark i have just bought a p170 its a cracking little amp the only problem i have is it lets you know which recordings are rubbish. hearing background noise and hum i never heard before how will i do this mod to the opamp did you remove components or did you bend the pins please help i want to do this mod thanks
john

[13oots2]

Hi John, no need to snip the pins or remove anything, just bend pins 1,5 and 8 out of the way. It all works straight out of the box so to speak

[whats gan on]

hi mate thank you for your help it works perfect what improvements did you get? is my p170 has more detail than before more natural vocals with more bass' better bass in fact i used a ad797 highly rated op amp used in hi end dacs
thanks for your help
john

[whats gan on]

AD797AN by Analog Devices

The AD797AN is a very low noise, low distortion Op-Amp. The "797" rivals the OPA627 for top spot and in some systems comes out the winner.

If your system tends to be a little dark sounding this is the one to try.

AD797 Characteristics

•Open, lively and transparent
•Fast and accurate with deep musical detail
•Ultra wide dynamic range of -120db at Audio Frequencies
•AD797 Spec Sheet

[nigelwright7557]

Originally Posted by 13oots2

A word of caution to anyone working on this amp, despite being as careful as possible using solder wick and not rushing the job, several tracks started to lift and I had to use point to point wiring on one solder joint.

It always pays to take upgrades one step at a time then if it suddenly stops working you know that the last change is where the problem lies.

I always do the same when upgrading a design of an amp, one mod at a time.

[whats gan on]

thank you for the very good advice i do that also. as in the past i modified everything all at once and when it did not work lol i did not know what the fault was i learnt the hard way

[whats gan on]

Originally Posted by 13oots2

Hi John, no need to snip the pins or remove anything, just bend pins 1,5 and 8 out of the way. It all works straight out of the box so to speak

have ever disconnected your interconnects from your pre amp or cd player when you turn your p 170 on i get a loud popping sound ,from speakers i used the ad 797 its ok when connected to source but when you disconnected it pops loud when i put the lm318's back in all is ok and i must admit its a good chip the lm318 sounds right in my system

[whats gan on]

i have put a 100 n cap a cross pin 4 and 7 and this seems to stop the low frequency popping from me speakers when the interconnects are removed after some time listening the AD797 is defiantly a better op amp over the lm318 in fact it is a new amplifier now with loads more detail the ad797 is amazing op amp it is cheaper than the BB 627 IT MAY WELL SOUND BETTER TOO