Preamp opamp upgrade

[d3imlay]

I'm considering upgrading the opamps on a Phase Linear 2000 preamp. The originals are RC4739 in the phono stage and RC4136 for line level. From my searching it looks like the opa2134 is the way to go assuming I can get/make adaptor boards.

Is there another opamp that should be considered?

I can post a PDF of the schematic if someone want it.

[jackinnj]

The RC4739 is a dual in a 14 pin shape so you will need an adapter -- the RC4136 is a quad of the uA741 (LM741 etc)

you might consider including the National Semi LM4562 -- as someone is organizing a group buy -- this is a very nice dual opamp recently introduced by Nat Semi -- it is available in 8 pin dip, soic and TO5 -- the TO5 is pricey at ~$12 but you can just fit the leads into the socket of the RC4739. Elsewise, just use a piece of perfboard and some molex 0.100 male headers to refashion a DIP-carrier.

the National LME49740 is a high performance quad opamp -- the Texas Instruments OPA4134 would also fit the bill.

Digikey carries the LM4562, LM49740 etc.

one thing you must consider is getting a pair of old colony super-regulator boards -- in addition to replacing the opamps improving the power supply will have a beautiful effect on the performance. I just finished up a mod to a Crown IC150a using the aforementioned nat semi chips and a super reg and the sound improvement was stunning. The topic of super regulators is flogged like a dead horse on this forum.

[DSP_Geek]

Just as an FYI, RC4136s have an unusual pinout which makes them incompatible with almost any other quad opamp. Not that OPA4134s are available in DIPs anymore...

[Leolabs]

If I was not mistaken,it does have some compensation pins.

[jackinnj]

here's a link to the datasheet -- http://staff.bcc.edu/eet/4136-rca.pdf -- it is indeed different from the standard 4 opamp pinout.

[Kurt Hyneman]

I found a place called Aceffects.com a year ago in Milwaukee Wisconsin that has drop in replacement IC's for the RC4739 / XR4739. I stopped by the guy's place and he is just loaded with effects pedals and parts piled up to the ceiling! He told me the chips are a custom circuit. It is a bit taller but worked great in my poly circuit. I think I paid around $6.00. Really neat place.

[Don Nebel]

There is a Browndog adapter for the RC4136 application. It will allow the use of 2 surface mount dual op amps.

[Jeff M]

I tried the brown dog adapter and it was a pain soldering the surface mount op amps. I ended up calling them at aceffect and bought a drop in unit for less than the cost of the adapter and the opamps plus I did not have to solder it. They also threw in some free stuff and had some other old effects parts I was looking for. I am also sent in an old MXR pedal that they restored to like new condition, the re-powdercoated it and did the silkscreening although it wasn't cheap but it looks great. They said they are upgrading their silkscreening process soon and will be able to cut times and prices in half. Neat place and the owner returned my call me personally.

[audiodoctor]

I was able to get both the XR4136 and XR4739 from aceffects last week. I just dropped them in and it was up and running.

They custom make them in house. Been living here 50 years and never knew there was a place like this just across town. I asked why they don't advertise and was told it is a side job and they are way too busy by word of mouth.

I tried a few of the pedals they were working on and they sounded good. I am thinking of getting a custom pedal made there, anyone know one who has one?

I also really liked their pedal look and colors and that it is all made in USA. Not a bad price either for being custom made but was told 3-6 month lead time. Wierd place being half in the back of an apartment and a small basement shop, really neat though!

[audiodoctor]

I picked up my custom distortion pedal (that took aceffects 2 month to make but quoted 6 months) It sounds awesome. I asked about the 4739s and they now have 6 different drop in replacements, with three being upgrades and three are "hotrodded" (their own words). I bought one of the "hotrodded" model HR1 and put it in my old Poly Brute and I could tell an improvement!