Yeah, switched q3 around. I just checked again on the data sheet and it has the same pinout as a bd130 ECB, I am using 2sc3423. For some reason I marked it as BCE, I have 2sc1819 listed as such and I placed 2sc3423 right in the same category on my schematic print out.
After switching Q3 around, Vbe is now .588 and .612 for Q2.
Your logic was correct!
Thanks
After switching Q3 around, Vbe is now .588 and .612 for Q2.
Your logic was correct!
Thanks
Hello Greg
In your B-AKSA 55 web page you wrote:
"Voltage amplifier (Q3) can not inform, a lot of them works there (I used a KSA3505)"
Maby there is a little typo error, I presume you was meaning KSC3503 and not KSA3505 ?
If so, it may need a little correction, in case some guys would want to use the same VAS transistor than you.
The KSC3503 are a very good and easy to find VAS transistor, I use it for all my amps. It's the Fairchild Semi version of the 2SC3503.
Bye
Gaetan
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Great Wendell 😀
Yeah, the differing pinouts of the TO-92 and TO-126 transistors are a pain. I put this page together because I was always referencing the datasheets.
http://users.tpg.com.au/gerskine/greg/vas%20transistors.htm
I think that means you can set the Vbias, double check the DC out, monitor transistor temps, then test with some old speakers.
You might want to think about a inductor on the output. Rabbitz has supplied me with some details that I will put on the web site. (That's OK Rabbitz?)
regards
Thanks Gaetan,
I appreciate the feedback. I like to be accurate, and even a missing full stop or comma is important to me.
regards
No problem Greg.
Wendell C
I couldn't quite see the orientation of Q3 in the pic and as Greg said, if not using the BD139 then you need to have the data sheet beside you to make sure the pinout is correct to suit the PCB. I had a similar issue and voltages on my first ever AKSA when it was about 1 year old where I destroyed Q3 by doing something stupid.
P1 should be 100ohm not 1k
Hi all,
I just noticed what I think is a "minor" error in my schematic of the BAKSA. P1, the pot that's adjust Vbias, has the value of 1k on the schematics and BOM. Checking the original schematic (posted by Carlos many years ago) shows it should be 100ohm and a quick look at Hugh's original AKSA 55 schematic shows it is 100ohm as well.
I can't see any major problem though, other than the Vbias will be way, way under to start with, you will need to turn the pot many times before it gets close to the correct setting (roughly 60ohms), the sensitivity of the pot adjustment is effectively 10x greater.
If anyone can see a potential problem I would be grateful for the feedback.
regards
Hi all,
I just noticed what I think is a "minor" error in my schematic of the BAKSA. P1, the pot that's adjust Vbias, has the value of 1k on the schematics and BOM. Checking the original schematic (posted by Carlos many years ago) shows it should be 100ohm and a quick look at Hugh's original AKSA 55 schematic shows it is 100ohm as well.
I can't see any major problem though, other than the Vbias will be way, way under to start with, you will need to turn the pot many times before it gets close to the correct setting (roughly 60ohms), the sensitivity of the pot adjustment is effectively 10x greater.
If anyone can see a potential problem I would be grateful for the feedback.
regards
I had no problem with 1K at P1 and still allowed plenty of fine adjustment as the voltage didn't rush in.
Member
Joined 2009
Paid Member
same story with me: my AKSA clone used at least 512R pot for adjustment (but later versions used 1k)
Hooray last CPA exam finished. been at new job for three weeks. Now it's time to sort out this build for christmas holiday break.!!!
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Rabbitz\Greg\Hugh,
Thanks for your support with this project.
I have some questions:
What parts are the optimal devices to use from WES rather than the more common BD1xx . I can also source from Mouser if there is an extra special device.
How do i match for the LTP? Not having done this before, what am i matching. How many devices will i need to buy to get a good match? I'll be building 4 channels.
Cheers
Craig
Thanks for your support with this project.
I have some questions:
What parts are the optimal devices to use from WES rather than the more common BD1xx . I can also source from Mouser if there is an extra special device.
How do i match for the LTP? Not having done this before, what am i matching. How many devices will i need to buy to get a good match? I'll be building 4 channels.
Cheers
Craig
Hi Craig,
I recommend the components in the optional column of the BOM:
Bill of materials
For the LTP I just match for hfe using a multimeter. I usually buy small signal transistors in batches of a hundred or two, if I can find a good source, usually in the range of 6 or 8 cents each.
Alternative transistors:
Small Signal Transistors
regards
I also recommend checking out RS before Mouser, as they have a reasonably wide catalogue of parts and are a little bit better in terms of shipping costs, so long the 1wk wait for internationally stocked parts is no problem.
ED- for aussies
is this a bit rich?
I sent off a request to WES. I haven't yet checked elswhere but it's a bit more than i expected. Do i have unreasonable expectations?😱
I sent off a request to WES. I haven't yet checked elswhere but it's a bit more than i expected. Do i have unreasonable expectations?😱
Thanks Greg. Mouser is the go. RS didn't have much and charge way too much for metal film resistors. I think i can negotiate the postage down to a USPS small flat rate parcel which is around $13.
When choosing the semis, should I use low med or high grading? Or does it matter at all?.. I imagine the different gain figures must have some impact somewhere.
When choosing the semis, should I use low med or high grading? Or does it matter at all?.. I imagine the different gain figures must have some impact somewhere.
Greg,
I've build the old aksa using rod elliot pcb
I'm wondering if you can tell me
how does the BAKSA sound?
is it as good as ( or better than) the original ?
many thanks
I've build the old aksa using rod elliot pcb
I'm wondering if you can tell me
how does the BAKSA sound?
is it as good as ( or better than) the original ?
many thanks
Wouldn't one expect the Vbe measurements for any of Q1 - Q8 to be normally in the range 0.57 - 0.62 V, or even a bit higher? Its good that the LTPs are very close.
Hi dexter,
I have not done a direct comparison, so I could only guess at the moment.
Rabbitz has reported good results and he does have a lot of experience with the AKSA 55's (although he did do a few mods to the published BAKSA). I would hope the BAKSA would slot in between the AKSA 55 and AKSA 55N+.
What would you classify as the original?
I have an AKSA 55 V1.6 and AKSA 55N+ V2.0 and I know of the even earlier ESP AKSA/P61 and I guess there are a lot of other versions with different components and values.
With the "real" AKSA 55 you get quality control provided by Hugh and I would imagine the sound would be very close between different builds. I would expect different BAKSAs to sound a bit difference because everyone would use different components.
regards
Yes. A value out of that range indicates something bad, like a reversed transistor.