BA-3000 upgrades?

[Kale]

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

Warren, I am sure that we will have very interesting discussion about that topic if I will know speaking English language better than now, but unfortunately I dont know speak English very good, just only good...
You know, that music is very complex signal, music is not sine wave from 20 Hz to 20 kHz, so because of that is very good to have high speed semiconductor, that it can transfer that complex signal with less damage of signal (music) structure...
At the end, is it important, if you for any reason change some transistor in some circuit, replace that transistor in some vintage audio circuit with one, which has the same technical characteristic as that old one, not better, not worse, just only the same (or so close to the same).

 

[xoaphexox]

If I understand what you are saying, Kale - changing out for a slower ft transistor will change the slew rate and rise time? So you could make a fast accurate amp "slow" and "warm" this way? (not that I would want to - just theorizing)

 

[dr*audio]

I think that 30MHz is more than fast enough to provide fast enough slew rate. I do admit that it is possible that it could affect the stability of the amp, if it lowers one of the poles (-3dB open loop frequency response) but I think the 30MHz pushes the pole out far enough that it shouldn't be a problem.
On the other hand, if the Fairchild parts are better, there is no reason not to use them.

 

[EchoWars]

Personally, I think having the pre-drivers slower than the drivers is not a great thing...bandwidth of devices should descrease as you approach the output stage. But while I doubt it would be a problem replacing the original TO-202 devices with TO-220's, I still think that the linearity & bandwidth of the Fairchild KSA1142 and KSC2682 makes them a superior choice for the job in this amp.

Digikey simply doesn't have what I consider to be a decent substitute since the 2SA0914 and 2SC1953 were dropped by Panasonic. Their loss is a real bummer, as they were excellent transistors.

B&D also carries the Sanyo 2SA1210 and 2SC2912, which are also a decent choice.

 

[Tichu]

I follow this thread with pleasure, and I must add a comment about Ft:

Ft found in a datasheet of a transistor is the "unity gain cutoff Frequency", also called "gain-bandwidth product".

At this frequency, the maximum voltage gain achievable with a linear stage using this transistor will be 1, so no gain.
If the predriver transistors are used with a voltage gain of 10, then the frequency has to be "derated" to 3MHz instead of 30MHz.

You get the picture.

 

[Nakdoc]

Just a comment. The 4 meter diodes D01, D02 look like two black beads with a green dot denoting cathode. These dual diodes open intermittently. Each black diode was replaced with a pair of series connected 1S119 diodes. It requires 8- 1S119 diodes to replace all four black diodes in a BA-3000.

 

[dr*audio]

Well, guys, the KSC2682 has been discontinued. The KSC1142 is still available, but not much sense in that. It's probably soon to follow. I am going to try to make a large buy of KSC2682 if I can find them. If not, I am going to the OnSemi parts. The Sanyo parts, at $2.60 each, are relatively expensive to buy a lot at one time. Even the OnSemi's are $1.05 each but that's not too bad. I will report on how they work.

 

[dr*audio]

I did a bit of research on Fairchild's website, and I found KSA1381 and KSD3503 seem to be nearly the same transistors, but with a VCBO of 300V. Mouser doesn't have the higher hfe parts, but they do have hfe = 100 and they are $.27 each, so I bought 50 each.

 

[xoaphexox]

Was looking up info on the BA-3000 and came across this thread - just wanted to drop a line and say my BA-3000 is still in daily rotation and going strong. I can't see myself ever parting with it

 

[Duffinator]

Unfortunately I no longer have mine but it was a terrific sounding amp and had killer looks to go with the sound.