>>>mhz class-d amp for hifi audio MCD-6版本详细测试资料图片及组装方法,

peterleest

机壳为铝制。昨夜试机，夜黑风高，MCD静如止水，毫无噪声，果然名不虚传

一声道开声，另一声道不响，初听蔡琴老歌，仍然凄凄凉凉，如深闺怨妇，听了心酸。

开开关关，又烧了几粒main fuse，时好时坏，小姐脾气，胜難侍候。

查小transformer，名为12Vac，實出19.9Vdc。想MCD内线稳压，应无大碍。J15 & J16暂用2k。

地仍未料理，机壳没着地，疑有自激。近日远行，来日方试。

peterleest

yes, it is alumimum, 5mm thick, quite difficult to drill holes. My MCD is now working fine

the channel that didn't work previously is caused by a loose connector. For the fuse blown problem, it needs some explanations.

The relay in the remote control kit has a 47nf paralleled to absorb sparks. However, this capacitor allows the 230V main supply to pass thru even if it is off. It presents a 90vac drop to the small transformer, produces 9vdc and always supply to the MCD 15VDC Sub. It also triggerred my softstart circuit.

When the +/- 26VAC cuts in, it creates a large surge current and blow the fuse. After changing the capacitor to 0.01uf, it is working fine. The fuse that I am using is 2A fast blown type.

peterleest

I did a scope and find some interesting results.

pic 1 - MHz residue

pic 2 - 1khz sine wave on speaker terminal, it is encapsulated with the MHz residue, is it normal?

pic 3 - show channel A noise floor when volume turn to max with no input. about 33mv.

pic 4 - as above, channel B noise floor, about 42mv.

peterleest

By grounding the signal ground, MCD module ground, remote control kit's ground to the chassis, it didn't help to reduce noise floor. However, after grounding the selector board's digital ground to the chassis, it completely eliminated the noise.

It seems that the CPU generated lots of noise. Heyj; the designer of the remote control kit; did a good job, he elevated the board and as such, the CPU is hide underneath the cover, with the chassis and PCB ground plane's shielding, it helps to reduce noise. For this reason, I will keep the existing layout.

The triangle wave is loaded with 10R load paralled with 1uf capacitor, it looks very good as compared to an old commercial amp.

peterleest

sound wise, initial impression is that it is very detail, sound stage and instruments imaging is very good , mid bass is well defined but lack of deep bass.

LPRLLG

原帖由 peterleest 于 2008-3-16 23:32 发表
sound wise, initial impression is that it is very detail, sound stage and instruments imaging is very good , mid bass is well defined but lack of deep bass.

声音中性, 细节非常丰富,声场和乐器形体很好,低音很好, 超低音有所欠缺……

这听感还不错……，超低有所不足，是不是电源部分还需加强？

peterleest

I don't have a very good audio system. I have an Denon AV amp but the sound is not up to mark, as such, I move on to a diy Alpeh-X. The Class A Alpeh-X sound very sweet and soothing, one can listen to it for long hours without frustration. However, the Alpeh-X waste energy and generates lots of heat, not ideal for tropical country, I am looking for a good sounding as well as environment friendly amp.

my speaker is a bookshelf Dynaudio Countour 1.3, cd player is pioneer DV 989AVi, the pioneer dvd player uses ad797 ops amp.

will your new mcd module resolve the small ringing discussed in the diyforum

peterleest

原帖由 FUMAC 于 2008-3-17 00:53 发表



第一: 耦合电容, 我们现在MCD内部使用一个耦合电容 22u,

第 ...

Someone gave me a very old Parasound HCA800II, I am quite surprise to see that they used 3 MPP capacitors; 20uf, 0.01 and 0.47 in parallel for input coupling. Also, others use MICA for the feedback loop.

Perhaps it could be one of the secrets to achieve good sounds; It was done many years ago.

http://members.aol.com/sbench102/caps.html