Forum upgrade to SMF 2.1.2, still working on re-theming.
Started by Koreth, January 01, 2010, 04:01:01 AM
Quote from: DartPlayer170 on October 26, 2011, 05:41:53 PMYour last statement is not correct. You can hook up a 4 ohm or an 8 ohm speaker to the 2030A.You can replace the wall-wart to a 20W ( more would be a waste since the 2030A cannot handle it ).The problem is to figure out how high of a voltage to get for the wall-wart.There are two problems:1 - the rating on the wall-wart is nominal. It may be more than the rating even at full load.2 - the current drain of the 2030A is dependent on the supply voltage, the load and the input signal. And hence, so is the power dissipation. The 2030A is rated for 44V max and 20W max. However, the current is dependent on the load. If you use a 4 ohm speaker then a 34V supply will dissipate 20W. I=P/V so the current is about 600mA.What I can tell you is that I have replaced the wall-wart with a 24V 600mA and it works fine. If you want to create a cleaner sound with the gain at 0, then you need to decrease the gain in the first stage of the amp. The designers set it too high. The clipping diodes that you were told to remove begin distorting the signal at about 800mVpp. You could just remove these diodes as suggested ( d1 and d2 ) if you don`t want to be able to use the distortion circuit. Another solution is to increase the negative feedback to the stage 1 amp. This can be achieved by replacing the feedback resistor with a higher value. The feedback resistor is in series with an electrolytic capacitor between either pin 2 or 6 ( depending on which one they are using as stage 1 ) of the JRC4558D and ground.
Quote1. Regarding the power supply: My intention is to hook this up to a 8Ω cabinet. So, are you saying that the original wall-wart will not be enough? If this is correct then, what are the specs for the proper PSU?
Quote2. I thought phatt's advice about removing the diodes meant the gain pot is still working and you still get some distortion, you just get less distortion or "cleaner" distortion. However, from your last post, if I understand right, are you saying the gain pot becomes inactive and you basically lose ALL distortion this thing can produce? If that's the case, then no this is not what I am after. I do want the versatility of having a Gain control before my Volume. Question is can this Gain control be more gradual in response and smoother in performance?
Quote3. The 24V 600mA wall-wart powers your MA007 right? Are you using it as is or you modified it and play it through a different speaker?Is this the MA007 ? Is it made of plastic? I'd be curious how it sounds!?!
QuoteSPECIFICATIONSOutput Power: 2 watts RMSFrequency Rang: 60Hz ~ 6kHzSpeaker: 4" / 8W / 4 ohmsInput Sensitivity: 26 mVPower Supply (not included): 14V DC 500mA or 2 x 9V batteriesDimensions: (LxWxH) 6.75" x 3" x 6.75"Weight: 2.5 lbsSPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE.