2SA733 "K"

Discuss mods, hacks, tweaks, etc.

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mux
 
Posts: 47
Joined: Sat May 28, 2005 11:28 pm

Post by mux »

braw wrote:Not sure what if anything this will do to the sound, but I'm excited to find out.
You're not the only one! :D I didn't bother testing my 733's when I assembled my x0x, and I've wondered ever since just how much difference it makes.

When I a/b'd with my friend's TB-303, we noticed two differences. The first was that on his cutoff knob, the bottom of the knob range was a cutoff value FAR lower than the bottom of my x0x cutoff knob range. He mentioned that in the 303, there's a trimpot to adjust the cutoff range, is this the case? If so, which resistor in the x0x adjusts this value, 'cause a trimpot should be an easy mod. Secondly, we also both noticed that the x0x square wave had more second and third order harmonics than the 303; you could almost hear a second tone in the x0x squarewave, a fifth above the fundamental. The saw wave was pretty much identical to our ears.

I suspect the square wave harmonics will be affected by the higher-value 733's. I'm really looking forward to hearing before and after WAV files! Please record at the highest quality you can... 24bit/48khz WAV would be awesome. :)

If there's a big difference, I'll definitely mod my x0x. There's a place near my house that apparently stocks almost 7000 different types of rare transistors.

Oh, and FF, that sip strip trick is great, I'm definitely going to do that.

FF
 

Post by FF »

Your friends 303 could have had the cutoff mod done, here's how - remove R47 (10k) and replace with a wire link, adjust the trimpot (TM3 IIRC but check) in your x0x to taste, you can get the widest range of frequencies I think with the trimpot fully cw, but you may find it goes too low so adjust to taste. This will extend the range of the cutoff considerably in the lower region without affecting the top range and is probably one of the best mods IMHO. If you don't like it it's pretty simple to revert back - just put the resistor back and alter the trimpot.

FF

evilxsystems
 
Posts: 406
Joined: Thu Jul 07, 2005 10:23 pm

Post by evilxsystems »

mux wrote:
Oh, and FF, that sip strip trick is great, I'm definitely going to do that.
Seriously...I wish I had done that so I wouldn't be sitting here trying to rip this BANNED up 6110 out...

I just ordered some strips from mouser so I don't have to do this again :)

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subatomic
 
Posts: 523
Joined: Wed May 11, 2005 3:12 pm

Post by subatomic »

evilxsystems wrote:
mux wrote: Oh, and FF, that sip strip trick is great, I'm definitely going to do that.
Seriously...I wish I had done that so I wouldn't be sitting here trying to rip this BANNED up 6110 out...

I just ordered some strips from mouser so I don't have to do this again :)
I created homemade SIP strips from DIP sockets, just cut it apart and shave off the jagged plastic. Works awsome, and cheap since I already had a bunch of DIPs...

FF
 

Post by FF »

@evilxsystems - The easiest way to get the 6110 out is to cut the legs with some small cutters, then simply desolder with a solder sucker it will leave a nice clean hole without damaging the pads on the PCB as it will suck out all the old solder along with the legs.

This is what I always do for removing IC's as I used to mess up tracks before I was told about this method, I would recommend to anyone building a complex kit to use sockets as it makes servicing and faultfinding a lot easier.

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subatomic
 
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Joined: Wed May 11, 2005 3:12 pm

Post by subatomic »

FF wrote:This is what I always do for removing IC's as I used to mess up tracks before I was told about this method, I would recommend to anyone building a complex kit to use sockets as it makes servicing and faultfinding a lot easier.
Would you socket transistors? I only socketed the Q8 Q9 Q10 so I could find better betas... and the 4 transistors with the 6110 chip in case I get the 662... Wondering if I should have socketed all the rest. Seemed like overkill. But for servicing (as you say), maybe it would be good...

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maxtim
 
Posts: 213
Joined: Wed Oct 12, 2005 5:01 pm

Post by maxtim »

I'm Really interested to hear how those k's sound.
I bought 250 of the regular 733 :shock:

I would not socket too many components. I have found that over time the connections are not as reliable as straight soldering and can cause headachs down the road.
The holes on this PCB are huge and the board is a good quality and tough. If you have some skills, desoldering and replacing components is easy.

FF
 

Post by FF »

Nah, I would not worry about socketing all the trannys, just socket the relevant ones to facilitate easy swap outs. I also agree that if you socket everything it can actually make troubleshooting harder later on, my advice is to use decent (not always the most expensive in my experience) sockets. I have always socketed my IC's though and in 10 years have never had a problem with sockets failing.

I did once own an BANNED Oscar that had factory fitted sockets which are notoriously unreliable after a few years, causing lots of weird problems.

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subatomic
 
Posts: 523
Joined: Wed May 11, 2005 3:12 pm

Post by subatomic »

braw wrote:Not sure what if anything this will do to the sound, but I'm excited to find out.
So has anyone done a comparison of what it sounds like with highbeta 733k's and normal low beta 733p's ?
If you drop 3 in an envelope and mail to me, I'd be happy to test them.
I have transistor sockets in the 3 slots that matter. :wink:

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braw
 
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Joined: Fri May 27, 2005 7:59 pm

Post by braw »

I have been way too damn busy to even start building anything yet.

I do have enough extras that I could send. PM me with where to ship them off to. I have a bunch of low 733's too. I wanted and still would like to try sub 300's, 320-350's, and then high 380-400's. What do you have and how many would you need for this? Beter someone that can do it sooner does it as I probably am still a few months away from even getting started.

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etaoin
 
Posts: 66
Joined: Thu Aug 25, 2005 6:08 am

Post by etaoin »

I just scavenged an old Samsung radio for parts for my DIY projects and came across a couple of these:

Image

Assuming this is a 2SA733Y, I can't really find anything on them. And the hFE goes off the scale of my meter (can't quickly find the manual to see what the maximum of my meter is).

Anyone come across a Y-variant before?

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