BC109C headache
- Thread starter thekid777
- Start date
Help Support GroupDIY Audio Forum:
Without a circuit description, it's only speculation.thekid777 said:
A well designed circuit should not register significant differences when swapping transistors.
It can happen if the closed-loop stability is marginal, or the DC operating point is not well stabilized against hfe (beta) variations.
BC109 existed in 3 grades, A, B and C. Are you sure you used the correct grade?
Do you have objective measurements to qualify your assessment?
Bo Deadly
Well-known member
Did you use solder from the 70's?thekid777 said:
Are you using tropical fish capacitors?
If you're listening to Abbey Road through them, that was actually released in 69. Try Dark Side of the Moon.
squarewave! ;D
To answer abbey road d'enfer, yes all is fine with the technical side of things,
it is just obvious to me something is different with the tr.
These kind of questions seems like a taboo on this forum, where most prefer to talk numbers only.
Ok! I'll pass and do my own!
Thanks
To answer abbey road d'enfer, yes all is fine with the technical side of things,
it is just obvious to me something is different with the tr.
These kind of questions seems like a taboo on this forum, where most prefer to talk numbers only.
Ok! I'll pass and do my own!
Thanks
RuudNL
Well-known member
Difficult to judge without knowing the circuit or having heard the difference.
But, how good the ears may be, they are never very reliable measuring instruments...
A difference in distortion between 0.01% and 0.02% may not immediately be audible, but I can surely measure it!
It might be a good idea to publish (part of) the schematic you are using these transistors in.
But, how good the ears may be, they are never very reliable measuring instruments...
A difference in distortion between 0.01% and 0.02% may not immediately be audible, but I can surely measure it!
It might be a good idea to publish (part of) the schematic you are using these transistors in.
ruffrecords
Well-known member
These questions are not taboo but in the absence of any real information it is very hard to provide a sensible and useful answer. There are many designs where differences in active components like transistors can be heard and also many designs where it cannot be heard. Unless we know which design you are talking to it is not really possible to make suggestions. If you can post a schematic then it may be possible to help you but saying 'all is technically correct' is not really much help.thekid777 said:To answer abbey road d'enfer, yes all is fine with the technical side of things,
it is just obvious to me something is different with the tr.
These kind of questions seems like a taboo on this forum, where most prefer to talk numbers only.
Ok! I'll pass and do my own!
Thanks
Cheers
Ian
They are not "taboo". The point is, if you want help, we must be on the same level of understanding.thekid777 said:
"Bad tone, less density, strange...", only you know what it means, we all have different understandings of it.
Subjective judgements don't carry well over the internet. Actually, figures are pretty good in that respect.
There are sites where subjective is the norm; it ends up being everyone blowing their own trumpet (or lyra, or bazooka), with their own unique receipe for good sound. Is it what you want? Or simple, well-meaning help?
Bo Deadly
Well-known member
There could be any number of reasons for the circuit sounding different other than the transistor. You don't have to post THD, SNR and hard numbers to characterize a circuit objectively.
For example, you could setup your 70's transistor circuit, send it some previously recorded audio track like a flute or guitar or whatever and listen. Then, without touching any knobs and without changing send / return levels, change only the one transistor. Then listen again. Is it different? Record both tracks and concatenate them and then listen to them back to back.
The point is that to really compare just the transistor change, everything else has to be the same. A lot of old discrete circuits that would use a transistor like BC109 might sound ok a little overdriven (the fuzz face circuit is not terribly different from the Neve BA283 or circuits you'll find in lots of gear like ReVox reproduce amplifiers). But if you change the level of signal going in even slightly, that distortion will sound different. So everything has to be identical except the one part that you want to test.
Another problem with subjective listening tests is listener fatigue. If you listen to the same thing over and over for even a few minutes, it starts to sound annoying. So when you're doing your listening comparison, you should take a break in between. Better still, create recordings of before and after changing the one parameter / part and then concatenate them into one file, then go do laundry or eat dinner or ride your bike and then sit down and carefully listen. Play it on a loop and close your eyes and when you think you've figured out which is which, hit the space bar and then look at the loop position to see if you guessed correctly.
But I can tell you right now that a BC109 transistor is not going to sound different (unless maybe it's the wrong grade or it's broken).
For example, you could setup your 70's transistor circuit, send it some previously recorded audio track like a flute or guitar or whatever and listen. Then, without touching any knobs and without changing send / return levels, change only the one transistor. Then listen again. Is it different? Record both tracks and concatenate them and then listen to them back to back.
The point is that to really compare just the transistor change, everything else has to be the same. A lot of old discrete circuits that would use a transistor like BC109 might sound ok a little overdriven (the fuzz face circuit is not terribly different from the Neve BA283 or circuits you'll find in lots of gear like ReVox reproduce amplifiers). But if you change the level of signal going in even slightly, that distortion will sound different. So everything has to be identical except the one part that you want to test.
Another problem with subjective listening tests is listener fatigue. If you listen to the same thing over and over for even a few minutes, it starts to sound annoying. So when you're doing your listening comparison, you should take a break in between. Better still, create recordings of before and after changing the one parameter / part and then concatenate them into one file, then go do laundry or eat dinner or ride your bike and then sit down and carefully listen. Play it on a loop and close your eyes and when you think you've figured out which is which, hit the space bar and then look at the loop position to see if you guessed correctly.
But I can tell you right now that a BC109 transistor is not going to sound different (unless maybe it's the wrong grade or it's broken).
+1 on Squarewave’s A/B testing recommendation.
The only thing other thing there is to ask where you sourced the transistors from. Fake BC109’s, like any popular but increasingly hard to find obsolete transistor, exist. I bought a couple of different pre-built Hood 1969 clone amplifiers a while back off of eBay because they were unbelievably cheap. In both cases, distortion was terrible. In both amps, testing of the 3055 outputs showed anomalies. Once replaced with old Mouser-sourced parts, everything worked as it should. And don’t get me started on fake JFETs!
The only thing other thing there is to ask where you sourced the transistors from. Fake BC109’s, like any popular but increasingly hard to find obsolete transistor, exist. I bought a couple of different pre-built Hood 1969 clone amplifiers a while back off of eBay because they were unbelievably cheap. In both cases, distortion was terrible. In both amps, testing of the 3055 outputs showed anomalies. Once replaced with old Mouser-sourced parts, everything worked as it should. And don’t get me started on fake JFETs!
ruffrecords
Well-known member
Is this a guitar circuit then? Many of those have characteristics that depend strongly on the components used. Why don't you just post a schematic?thekid777 said:
Cheers
Ian
thekid777 said:
Hi,
much better than any "numbers" please post some sound files of the OLD VS NEW so we can have a listem
cheers
living sounds
Well-known member
You can send some examples of old and new transistors to this guy and he will make a photographic analysis:
https://groupdiy.com/index.php?topic=76526.0
Probably much more useful for ICs than transitors though.
https://groupdiy.com/index.php?topic=76526.0
Probably much more useful for ICs than transitors though.
In my judgement I would not expect much luck speculating about how a semiconductor would "sound" from looking at it even with a microscope. Back in the 60s as a technician I would routinely grind the top cover off of metal power transistor to do failure analysis. Melted base leads or collector-emitter voltage punch throughs could be visible.living sounds said:
I have never had much luck opening up plastic transistor packaging without destroying the device. About the only thing you might determine visually is that the transistor die is the correct one. Back in the day, semiconductor makers would document the different transistor families and expected performance.
JR
living sounds
Well-known member
JohnRoberts said:
He's pretty good at opening stuff without destroying it though, it's all documented on the website.
