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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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After listening to the changes I had made to the Onkyo for several weeks ago I decided that it was time for round two. In round one, I replaced IC’s in the tone controls and replaced a few caps with larger values.
This was all very good, but it left a bottle neck too. That bottle-neck was the remaining 5532 IC on the main PCB. There are two there but one is the headphone amp, so I left it alone. There are also several 33 ohm resistors in series with the power rails that I decided had to go as well. There were two caps at the outputs of the voltage regulators that I had not replaced and three caps and a resistor at the black ribbon cable that takes power to the volume control PCB.
All of these changes can be easily made with the main PCB out of the chassis. Removing it was easy after removing the real panel. Then unplug everything that can be unplugged from the main PCB. But the gray and black ribbon cables do not come out, so leave them.
There are a lot of screws on the rear panel but they come out easily and leave the chassis wide open. There are four copper screws with shoulder-washers on the base of the heat-sink that have to come out as well. That leaves only a bunch of nylon standoff to deal with. I used a pair of long nose to deal with these.
The 33 ohm resistors can be removed or just jumpered out, I did both depending on the location. The solder they used on this PCB is funny stuff and does not wick-out easily. I had to add new solder to it in order to get it to flow. Be very careful not to rip-up any traces pulling on the components while removing them. The IC power pads are very small so watch out here. I put in a socket for the IC just in case they come out with a better IC some day. As with the tone control IC’s I installed an LM4562 in place of the 5532 stock IC. I had already replaced the caps for this IC in round one, so now I jumpered out the resistors. Then I did the two caps at the output of the regulators and a jumper in front of them that is for the input-output IC. The second resistor-jumper is next to a cap by the blue connector.
There are three caps and resistor-jumper next to the black ribbon cable going to the front panel. All of the caps were replaced with 1000uF units. They just fit in the space and I jumpered out the resistor on the bottom side of the PCB.
In the photos I took I show all of these changes, so write me for the pictures.
So, how does it sound? Well, first I am comparing it to my just up-graded Classe’ CP-35 and Model Ten power amps. Both of these have just received new LM4562 and LME49710 IC’s. These replace the OPA627’s I had used in my last up-grade. These gave my Maggie 3.3’s outstanding image and focus. Sharpe outlines and miles of depth. The Maggie’s too have been up-graded with all new crossovers.
The Onkyo amp comes so close to the performance of the Classe’ electronics, that it is hard to hear the differences. I do like the tone controls now (the Maggie’s can use a little bass boost) they don’t smear the sound. In the direct-mode the Onkyo is not glassy any more. The amp at only 85 watts has no problem driving the power hungry Maggie’s. Listening to an old favorite live recording where feedback and hum had been a problem, I now did not even notice those things; I was so much closer to the performance. This amp will never be a bottle-neck in any system I use it in from now on. Good Luck, bobwire
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Topic - Onkyo A-9555 Round Two - bobwire 09:29:19 01/08/08 (0)
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