Monday, February 22, 2010

Modifying the Rega Apollo CD Player

Recently I decided I needed a better CD player to use as a reference (I do have an audio manufacturing company after all- and the best I can currently afford is the Rega Apollo. My old AMC CD8b gave up the ghost a while ago, and since I mostly play vinyl didn't really care much.
Well, after getting the unit home (I bought it used from a local retailer in Seattle, Hawthorne Stereo - thanks Matthew) I just HAD to open it up and see..

Damn nice! High-end epoxy circuit board, nice components, etc. Not much for power supply bypassing around the discreet transistor output stage, though. And alot of 'lytic coupling caps, too. Also, the PSU for the audio stage doesn't have active regulation, just a simple shunt zener "regulator". But it sounded so much better than what I was used to that I let it be... for a while. I can never just leave it be.

So the first mod that I wanted to try was to increase the PSU bypassing on the output stage and install polypropylene bypasses around the output coupling capacitors. I had some 1uf Electrocube poly's for this, and ordered my favorite low-voltage electrolytic bypass caps from Mouser. These are solid organic polymer electrolytic that have very, very low ESR and will never 'dry out'. I use them for cathode bypass in my tube products.. they work great and sound great.

Carefully, I removed the 4 polyester .1uf bypasses, installed the 100uf 16V (Vishay 94sa107x0016epb) organic polymer caps, then re-installed the 4 polyester caps to the underside of the circuit board, along with the 1uf Electrocube output coupling caps in parallel with the stock electrolytics. Now I put it all back together and didn't have any leftover screws! Yay!!

The caps needed to break-in so I let it play in repeat for a day or so, and then listened to my favorite evaluation disc, YES Talk (1993- killer dynamic range and lots of recorded detail). There was an improvement in dynamic slam and a sweetening of the high-frequency details. The bass is tighter and more textured and at the same time goes a bit deeper. Overall an improvement... maybe I'll leave it alone for a while. We'll see...


Anonymous said...

I'm read with attention your mods about apollo player. Just a few questions: why do you put back the 100n cap in // with your 1uf and maybe the 470n, all this caps in // with the 22 uf electroytic? 4 caps in // !!! Is with this mod you get more bass? Or with your 100 uf decoupling cap? Thanks

-KE said...

The only bypasses that were there in the stock condition were the .1uf caps. I replaced them w/ 100uf solid polymer electrolytics so that each stage had better isolation from the other stage (parasitics via psu rails with signal modulation). These I bypasses w/ 1uf poly's and the original .1uf caps that I removed. Multiple bypassing make a more perfect cap with better frequency response.

Yes the bass response improved, but more noticeably the dynamics. Plus the high frequencies became a bit more pure and less grainy.

It's all subjective, but I could hear the difference!