BA-3000 upgrades?

[xoaphexox]

Thanks for posting the model numbers and prices!

In all honesty I don't think you will hear $10 worth of improvement. It's just something I wanted to do because this was/is the "best" piece of equipment I own and I wanted to spoil it rotten! :yes:

 

[xoaphexox]

Just got done dialing in the bias and offset. Not the easiest bias in the world to set but I managed to get it in.

It sounds fabulous - thanks Warren, once again you really helped me out!

 

[dr*audio]

You're welcome!:thmbsp:

 

[Kale]

Just got done dialing in the bias and offset. Not the easiest bias in the world to set but I managed to get it in.

It sounds fabulous - thanks Warren, once again you really helped me out!

Here I wish to say you something, because you have thermal compenzation transistor on heat sink of drivers transistors, when you will checking BIAS, you should check it with top cover on its place, if not, you will get the wrong results!
BTW, did you change thermal grease on driver transistors?

 

[xoaphexox]

Here I wish to say you something, because you have thermal compenzation transistor on heat sink of drivers transistors, when you will checking BIAS, you should check it with top cover on its place, if not, you will get the wrong results!
BTW, did you change thermal grease on driver transistors?

How can you adjust the bias with the top cover on? That is where I had to make the adjustments. I had the unit on it's side for an hour before making the adjustment.

The thermal compound had been changed on the driver transistors by the previous owner.

Thanks Kale!

 

[dr*audio]

Kale is right. Here is how I do it, and it's tricky. The bottom panel and feet must be in place for this to work properly.
1. From the top, with a hemostat, you attach alligator clip jumper wires to the emitters of 2 output transistors; one NPN, one PNP on each channel. You can access the emitters on the transistor sockets on the heatsink.
2. Drape the wires over the back of the amp, out of the way, and make sure they can't short to each other or the chassis. Connect your meter to one set of wires for one channel. I use 2 meters so I can do both channels at once.
3. Place the top cover onto the unit with no screws. If you are careful you will not crimp or damage the testing wires.
4. remove the cover over the driver board.
5. Turn the amp on and allow it to warm up for a few minutes, then adjust the idle current for 20mA across the 2 emitter resistors. I don't remember the values of the resistors, but you multiply 20mA X the total resistance to get the voltage reading you want.
6. Take a piece of electrical tape and stick it to the top of the driver cover, to use as a handle. Place the cover over the drive board and attach with one screw.
7. Monitor the voltage and adjust after 10 minutes. Always replace the cover over the driver board.
8. After it has been stable for 30 minutes you are done.

 

[xoaphexox]

General question - will the bias creep upwards as the unit heats up, or downwards? In my unit last night the bias seemed to settle downwards as time went by.

When I first powered up after putting the new transistors in the bias reading was 170mV! And the heat sinks got hot very quickly. I dialed them down to 20mV and they ran much cooler but they continued to drift ever-so-slightly down from 20mV as time went by.

 

[dr*audio]

With the case open the bias drops, but with the case closed the bias rises. I think this is caused by the output transistors warming up (with less ventillation) and drawing more current. Since the current sensing diodes are on the driver transistor heatsink, they can't sense what the output transistors are doing, and the control is not as good. I am thinking of a mod where the diodes are moved to the main heatsink. I might try that on mine next time I have it open.

 

[Kale]

...Since the current sensing diodes are on the driver transistor heatsink, they can't sense what the output transistors are doing, and the control is not as good. I am thinking of a mod where the diodes are moved to the main heatsink. I might try that on mine next time I have it open.

That BA3000 what I am working now, has BIAS transistor on heat sink of power transistors, look here

and i putted some Arctic Silver grease to better thermal transfer...

 

[xoaphexox]

What happens when bias is too low? Distortion? And when bias is too high? First distortion, then heat breakdown and destruction?

 

[roy55]

What happens when bias is too low? Distortion? And when bias is too high? First distortion, then heat breakdown and destruction?

I was thinking the same thing. Don't know if I want to know the answer. I guess I better follow Dr*Audio's steps above. Thanks Dr*Audio and Kale Great info.:thmbsp:

 

[dr*audio]

That BA3000 what I am working now, has BIAS transistor on heat sink of power transistors, look here

and i putted some Arctic Silver grease to better thermal transfer...

They put the transistor on the board, not on the heatsink. It would work better if it was contacting the heatsink. On the AU-9900 and AU-11000, and on Xophexox's BA-3000, there is a bias transistor (not a diode as I said, sorry I was at work, without the schematic) but the bias transistor is mounted on the driver transistor heatsink.

 

[Kale]

They put the transistor on the board, not on the heatsink. It would work better if it was contacting the heatsink. On the AU-9900 and AU-11000, and on Xophexox's BA-3000, there is a bias transistor (not a diode as I said, sorry I was at work, without the schematic) but the bias transistor is mounted on the driver transistor heatsink.

When you put back that board on its place, that transistor has contact with heatsink of power transistors, now I dont have the picture, but that is true.

 

[dr*audio]

When you put back that board on its place, that transistor has contact with heatsink of power transistors, now I dont have the picture, but that is true.

Ok, I'll take your word for it!:thmbsp:

 

[Duffinator]

B, we need an update on what you did to your amp and how it sounds.

 

[BHamm]

Well, the BA-3000 has logged about 20 hours now since its been home. Tech said allow at least 50 before its broken in. This was not a go-for-broke upgrade, instead we focused on the best return for my investment.

All the old caps were replaced with Blackgate, power supply upgraded and RCA jacks replaced. Parts came to $226.00 plus 3 hours labor. Tech measured 36 volts across 6-ohms = 216 Wpc. Distortion at 37.5 watts was less than 0.012% for both channels.

After hearing the amp again compared to the stock Sansui amp I was listening to, there was a noticable improvement in sound quality. The first thing I keyed in on was the bass. Most of my music is classic rock with some Jazz sprinkled in, so I have a good idea how the bass sounds through my equipment. This time it was tighter and more extended. There was more openness between the instruments and a richer, darker background. I think I even detected better imaging, although I have been playing with speaker placement and angle so this may have an effect too.

Overall I am quite pleased with the results and consider it a worthwhile investment. I appreciate all the responses and ideas others added to this post.

BHamm

 

[xoaphexox]

Awesome!

 

[dr*audio]

Use the Fairchild transistors that Kale talked about. I just bought the 2SA914, maybe they have a no lead version now...:scratch2:

I found a good sub for the 2SA914 and the 2SC1953. Use OnSemi MJE15034G for the 2SC1953, and MJE15035G for the 2SA914. They are higher current, power and voltage, and about the same hfe.

 

[Kale]

I found a good sub for the 2SA914 and the 2SC1953. Use OnSemi MJE15034G for the 2SC1953, and MJE15035G for the 2SA914. They are higher current, power and voltage, and about the same hfe.

But Warren, OnSemi MJE15034G / MJE15035G has fT only 30MHz and I cant find cob data for that transistor, but, in other hand 2SC1953 has fT 70 MHz (min) and cob only 3pF (Max!). I still think that Panasonic 2SC1953 / 2SA0914 and Fairchild KSA1142 / KSC2682 are better solution as pre-driver transistors.

 

[dr*audio]

But Warren, OnSemi MJE15034G / MJE15035G has fT only 30MHz and I cant find cob data for that transistor, but, in other hand 2SC1953 has fT 70 MHz (min) and cob only 3pF (Max!). I still think that Panasonic 2SC1953 / 2SA0914 and Fairchild KSA1142 / KSC2682 are better solution as pre-driver transistors.

Kale, can you hear 30MHz? I sure can't...