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Banzai Cmoy mods

post #1 of 31
Thread Starter 

So I bought a banzai cmoy kit on ebay last night, looks like a fun little project. I have experience soldering from my childhood days in r/c cars, volt modding my old desktop video card, and soldering a chip into my car's ecu.

 

Do you guys think there are any easy mods I can adapt to this? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320881716963#ht_17010wt_1037

 

I know one would probably be to change the opamp to the more popular 2227 I suppose. 

 

I seen this video , the guy just talked about changes to building it. http://www.youtube.com/watch?v=JU_cpWLVx84

 

These are images taken from another thread here

d936cefd_v2_10wm.jpg

ab9df3cd_newstereo-1234690849-216.jpg

 

Do you guys see any potential to say add a/c power, and maybe some sort of bass boost switch?

post #2 of 31
Thread Starter 

ok i see i can add a dc power jack. http://tangentsoft.net/audio/cmoy-tutorial/tweaks.html#dcjack

post #3 of 31
Thread Starter 

i bought the parts to build a trickle charger for it.. Ill keep this post updated on how it goes.  http://www.head-fi.org/t/185377/trickle-chargers

post #4 of 31

What does "trickle charger" mean? And how well does this amp work?

post #5 of 31
Thread Starter 

it is just a slow charger for the battery while its plugged into a wall outlet. Pretty simple for the looks of it.

 

 

post #6 of 31

Change the two jumpers (for Bias) to a bias pot. I have 2, one stock and 1 for opamp rolling so far have a 2xAD9897 on a SOIC adapter and sounds brilliant. Another mod is to make a rechargeable system for it, will involve playing around with the circuit a bit, using 2 9v rechargeable batteries and a DC charger port, if you want this system to be an on the go portable amp still.

post #7 of 31
Thread Starter 

thanks that sounds cool, can you show me what yoru talking about? I'm not familiar with bias pot

post #8 of 31

I recently built a banzai cmoy v2 for myself, it sounds amazing with a JRC4556, my only problem is that it has a bit of channel imbalance particularly at low volumes. 

Does anyone know how can I fix this problem?

post #9 of 31
Quote:
Originally Posted by willmax View Post

I recently built a banzai cmoy v2 for myself, it sounds amazing with a JRC4556, my only problem is that it has a bit of channel imbalance particularly at low volumes. 

Does anyone know how can I fix this problem?



Check your solder connection. The two jumpers that are next to each other are the channel bias. Make sure you have the jumpers on the pins otherwise you may encounter one side with or without sound (happened to me at the start). Another reason for channel imbalance could be the 20k pot or the 3.5mm headphone jack itself, do a test and twist your headphone plug around in the jack give it a bit of a wriggle and see if your volume is balanced.

 

Also, when you start to hear either side of your IEM/headphone distort, a static or low humming noise in the background of your music, means that the power source is low, i.e. change the battery.

post #10 of 31

 

Quote:
Originally Posted by DefQon View Post



Check your solder connection. The two jumpers that are next to each other are the channel bias. Make sure you have the jumpers on the pins otherwise you may encounter one side with or without sound (happened to me at the start). Another reason for channel imbalance could be the 20k pot or the 3.5mm headphone jack itself, do a test and twist your headphone plug around in the jack give it a bit of a wriggle and see if your volume is balanced.

 

Also, when you start to hear either side of your IEM/headphone distort, a static or low humming noise in the background of your music, means that the power source is low, i.e. change the battery.



I've checked the solder connections and they are ok. The jumpers don't seem to have any effect, as I've removed them and also alternated them and there was no noticeable effects to my ears. 

The only thing I noticed was that when I put the source volume very low and I have to crank the cmoy volume I don't seem to notice much channel imbalance, I can still hear a small difference but it is negligible.

post #11 of 31
Thread Starter 

I bought 2 radioshack 470uf 35v caps to replace the included 470uf 25v elna caps, thinking i would have a little more headroom when i connect the system with a 12v or 24v ac adapter (if i run 1 9v or 2 9v) .

 

But im looking at the Elna cap, could it be higher quality than this radio shack cap?

post #12 of 31
Quote:
Originally Posted by hypertek View Post

I bought 2 radioshack 470uf 35v caps to replace the included 470uf 25v elna caps, thinking i would have a little more headroom when i connect the system with a 12v or 24v ac adapter (if i run 1 9v or 2 9v) .

 

But im looking at the Elna cap, could it be higher quality than this radio shack cap?



Yes they are. The Cmoy design regardless of type is limited and therefore hard to mod to provide more headroom, such as driving higher impedance headphones. Generally replacing caps with the same uf rating but move voltage unless it is a tube amp will provide no or very little and unseeable benefits. The only reason why some people mod certain full sized amps replacing with bigger caps is so the amount of power pushed through the system isn't limited by the cap but having more headroom preventing stress on the cap possibly having it bulged or leaking. Certain tube amp's for example my small Bravo v2 tube amp has a DC power input of 24v, the power cap bypassing between the IRL513 (mod) mosfets and the tube itself on the circuit was a 25v rated cap. Theoretically this is enough but since there can be interruptions to power, a 25v cap will have a lot more stress on it then a 35v cap since the power going in is 24v, 1v from the wall, which can damage the circuit or components if a power surge is to happen. 

 

The Banzai moy uses dual 9v rails so therefore 18 in total, and since 25v is the next rated [v] for the cap, it is used has ample amounts of power to flow throughout the amp. Maybe upgrading the ELNA's to a 640uf 25v solid cap may have a little noticeable amount of improvement.

 

If you are trying to make an AC power adapter for your Cmoy, 12-18v is plenty and sufficient, 24v is unnecessary.

 

@Willmax, either your pot or your opamp is the problem, have you taken out the JRC opamp and plugged in back into its socket retaining proper notched orientation?


Edited by DefQon - 4/13/12 at 9:28pm
post #13 of 31
Quote:
Originally Posted by willmax View Post

 



I've checked the solder connections and they are ok. The jumpers don't seem to have any effect, as I've removed them and also alternated them and there was no noticeable effects to my ears. 

The only thing I noticed was that when I put the source volume very low and I have to crank the cmoy volume I don't seem to notice much channel imbalance, I can still hear a small difference but it is negligible.

Apparantly it can kill your Cmoy if you don't have those jumpers on. I am unsure, but if you search it up there was a post by an early user that had there Banzai cmoy circuit kill itself because the user had 1 jumper on out of the two.

 

post #14 of 31
Thread Starter 

I was hoping i could run the batteries in series, perhaps add the trickle charger I made from the link posted above.. I dont know if a single charger like that can be added to charge 2x 9v in series? however, the banzai cmoy takes 1x 9v to each capacitor in the diagram.  However I saw this guy's setup using an ac jack and he just has the positive to one side and negative to the other. http://www.head-fi.org/t/578273/just-finished-my-first-cmoy

 

I built mine like this guy did, he just did a different way of soldering the capacitors http://www.youtube.com/watch?v=JU_cpWLVx84  , I used those radioshack 470uf 35v caps and 4.7k ohm resistors for the virtual ground like that guy above in the just finished my first cmoy thread, and i could not get it to power on..   So i am thinking about unsoldering those mods and just build it kit stock with the original capacitors it came with. 

post #15 of 31
Thread Starter 

ok after last nights fustrations, got some good rest and went back at it. Got it going . I just don't know how to wire up the coaxial power jack. I plug the jack itself into the wallwart and read the polarity, than i solder wiring to matching polarity, and when i plug it in, nothing. What am I doing wrong?

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