Helo everyone,
I've recently completed Nelson Pass's Citation 12 amplifier. Sounds absolutely wonderful! Thank you so much Nelson pass! I have a few questions, however, the voltage of the speaker output is 0.14v on one side and 0.12v on the other. Some people said that it should not exceed 0.1v, is this normal? Also, when I turn the volume up swiftly without any music on, there's a moderate scratchy sound coming form the speakers. The noise doesn't kill your ears, but it would be great if I could eliminate that problem.
Any help would be appreciated. 🙂
Allen
I've recently completed Nelson Pass's Citation 12 amplifier. Sounds absolutely wonderful! Thank you so much Nelson pass! I have a few questions, however, the voltage of the speaker output is 0.14v on one side and 0.12v on the other. Some people said that it should not exceed 0.1v, is this normal? Also, when I turn the volume up swiftly without any music on, there's a moderate scratchy sound coming form the speakers. The noise doesn't kill your ears, but it would be great if I could eliminate that problem.
Any help would be appreciated. 🙂
Allen
So nice to see older projects still getting built.
The .14V is a bit much, but is not likely to do any damage.
Is it positive or negative?
Is the circuit identical to the published schematic?
As to the scratchy sound, I assume that you are running a
pot right on the input, becuase a scratchy sound during
silence means that their is either some DC on the pot. This is
not much of a problem - if you are directly coupling the input
of the amplifier to the pot, then you are most likely seeing a
smal amount of DC on the input, and this may relate directly
to your offset.
😎
The .14V is a bit much, but is not likely to do any damage.
Is it positive or negative?
Is the circuit identical to the published schematic?
As to the scratchy sound, I assume that you are running a
pot right on the input, becuase a scratchy sound during
silence means that their is either some DC on the pot. This is
not much of a problem - if you are directly coupling the input
of the amplifier to the pot, then you are most likely seeing a
smal amount of DC on the input, and this may relate directly
to your offset.
😎
Hi Nelson,
Hi Allen,
Did you match the input transistors? Q1 and Q2 should be both high gain and the beta should be matched between the to. That is why the original part was a dual part. They should be tied together so they are the same temperature as well. Also check that R1 is the correct value (12K).
-Chris
True. I like to call 50 mV defective though.
No doubt about that! Is the control after C2?
Hi Allen,
Did you match the input transistors? Q1 and Q2 should be both high gain and the beta should be matched between the to. That is why the original part was a dual part. They should be tied together so they are the same temperature as well. Also check that R1 is the correct value (12K).
-Chris
Hi,
Maybe it won't do any damage in like ten minutes but long-term-wise, would it have any affect on my speakers? I didn't exactly build this whole project my self. I'm only 16, so, I don't really have the skill to analyse schematics yet. I often find it hard just to build from certain schematics. And since I'm only a kid, it is also better for me to built it from a kit because it saves money and time.
Yes, I am currently using a pot as volume control. Last time I checked the schematic is almost the same with the power supply being the most different. R1 is 18K though.
Sorry Mr.Pass, I don't quite understand everything you've just said. Do you mean to say that the scratchy noise lead back to the output voltage?
Nope, I did not match the transistors at all and just soldered them on board randomly. Sorry if this is a stupid question but how would I match the input transistors?
I have attached the schematics that I used to build the amplifier. The Q1, Q2 and Q3 have been changed to MPS8599. Output transistors are replaced by IRFP240.
Sorry if I'm not able to understand all your replies, but help is better than no help so I am very gratefull.
Thanks again!
Allen
Maybe it won't do any damage in like ten minutes but long-term-wise, would it have any affect on my speakers? I didn't exactly build this whole project my self. I'm only 16, so, I don't really have the skill to analyse schematics yet. I often find it hard just to build from certain schematics. And since I'm only a kid, it is also better for me to built it from a kit because it saves money and time.
Yes, I am currently using a pot as volume control. Last time I checked the schematic is almost the same with the power supply being the most different. R1 is 18K though.
Sorry Mr.Pass, I don't quite understand everything you've just said. Do you mean to say that the scratchy noise lead back to the output voltage?
Nope, I did not match the transistors at all and just soldered them on board randomly. Sorry if this is a stupid question but how would I match the input transistors?
What do you mean by that? I'm so confused 😕
I have attached the schematics that I used to build the amplifier. The Q1, Q2 and Q3 have been changed to MPS8599. Output transistors are replaced by IRFP240.
Sorry if I'm not able to understand all your replies, but help is better than no help so I am very gratefull.
Thanks again!
Allen
The DC on the output is negative. Why does the output voltage drop from 0.12v to 0.03v when I have the signal cable connected?
Allen
Allen
Hi Allen,
Firstly, please use the built in quote function. It's much easier to read. It's the button above that says "Quote" and looks like
The DC offset drops because your source is providing a resistance to ground. Can you draw by hand how you added your control please?
-Chris
Firstly, please use the built in quote function. It's much easier to read. It's the button above that says "Quote" and looks like
. I had to add the periods, they are not normally there.
The DC offset drops because your source is providing a resistance to ground. Can you draw by hand how you added your control please?
-Chris
Hey Chris & Mr. Pass:
Sorry about the misleading quote thing.
I didn't add a control, my control is the same as a passive preamp so it's in a seperate box. Nothing much to draw about that. I just connect the input of the pot to the input, output to output, and gnd to gnd + box.
Allen
Sorry about the misleading quote thing.
I didn't add a control, my control is the same as a passive preamp so it's in a seperate box. Nothing much to draw about that. I just connect the input of the pot to the input, output to output, and gnd to gnd + box.
Allen
Attachments
Hi Mr.Pass,
Allen
Are you talking about R8? Thats the only resistor that I see connected to the ground from the input ground and it's 10 ohm instead of 10k.
Allen
Mr. Pass is referring to R10, I believe..
Hmm, gotta try one of these some day, thanks for bringing it to the top.
Hmm, gotta try one of these some day, thanks for bringing it to the top.
R10 is also incorporated in the schematic that was used on my amp except it's R12.
I would like to know more about matching the input transistors.
Is there a thread or site that could teach me how to do that? Thanks
Allen
I would like to know more about matching the input transistors.
Is there a thread or site that could teach me how to do that? Thanks
Allen
Hi Allen,
There are some threads. You want to match the beta's, or gain of the transistors and make the bodies touch together so they are close to the same temperature.
The SymAsym threads would be good to go through. I have posted a simple gain matching circuit a couple times around here as well.
-Chris
There are some threads. You want to match the beta's, or gain of the transistors and make the bodies touch together so they are close to the same temperature.
The SymAsym threads would be good to go through. I have posted a simple gain matching circuit a couple times around here as well.
-Chris
You can adjust the value of R1 to get some adjustment of
DC offset, but I suggest that you try some input transistors
with higher current gain. The devices you are using have
betas of about 100, and you might benefit from devices that
have 300 to 500.
😎
DC offset, but I suggest that you try some input transistors
with higher current gain. The devices you are using have
betas of about 100, and you might benefit from devices that
have 300 to 500.
😎
Would 2N5089 work as a good replacement for MPS8599?
Are there any other substitutions that has would work well in my situation?
Also, if I switch from PNP to NPN, I only have to turn the transistor around right?
Thanks!
Allen
Are there any other substitutions that has would work well in my situation?
Also, if I switch from PNP to NPN, I only have to turn the transistor around right?
Thanks!
Allen
Hi Allen,
The 2N5089 is only good for 25 volts, the gain is much better. A 2N5210 is good for 50 volts. A 2SC1815 would be a good choice (50 volt) and a 2SC2240 would be even better (120 volts, gain is 200 to 700 depending on rank). I tend to use these most of the time. The pins need to be rearranged to your board.
I don't know if that's been any help, but if you study the information on these transistor numbers, you may learn something.
Here is a link for the 2SC2240 transistor : http://www.google.ca/search?hl=en&q=2SC2240&btnG=Search&meta=
You can search the other ones out on Google.
-Chris
The 2N5089 is only good for 25 volts, the gain is much better. A 2N5210 is good for 50 volts. A 2SC1815 would be a good choice (50 volt) and a 2SC2240 would be even better (120 volts, gain is 200 to 700 depending on rank). I tend to use these most of the time. The pins need to be rearranged to your board.
No. The entire front end section needs to be flipped over and the rest of the circuit changed to accept this new arrangement. 2SA970 would be good then.
I don't know if that's been any help, but if you study the information on these transistor numbers, you may learn something.
Here is a link for the 2SC2240 transistor : http://www.google.ca/search?hl=en&q=2SC2240&btnG=Search&meta=
You can search the other ones out on Google.
-Chris
Hi There,
for the front I used BC 416...they seemed to work very well on that amp...
may I ad a question to the master on that thread?, the bias seems to be thermically controlled by Q4(MPSL01 on original schematic) , a good thing in AB class maybe(on the original schematic) but I tweaked this amp to run full class A (with less voltage at PSU, around 25V), but as the amps starts to heat , the bias goes down due to this transistor that asts like a thermometer...I isolated it the best I could from the heatsinks, but is there an electronical trick that could be done easily?
ran in class A this design is very attractive..well worth doing it..
Vince
for the front I used BC 416...they seemed to work very well on that amp...
may I ad a question to the master on that thread?, the bias seems to be thermically controlled by Q4(MPSL01 on original schematic) , a good thing in AB class maybe(on the original schematic) but I tweaked this amp to run full class A (with less voltage at PSU, around 25V), but as the amps starts to heat , the bias goes down due to this transistor that asts like a thermometer...I isolated it the best I could from the heatsinks, but is there an electronical trick that could be done easily?
ran in class A this design is very attractive..well worth doing it..
Vince
Helo everyone:
Thanks both for the tips on transistor selection Chris and Vince. I'll look for these parts in a few days cause I gotta get ready for school. Yes, it's finally starting!
Just yesturday, I accidentally turned the bias up to like 1400 for a second. Then I saw this tiny puff of smoke.
Amp still works, but I'm not sure how much damage I did to the amp. If I were to replace whatever that is damaged, what would it be? The IRFP240s?
Class A would be nice, but I'm short of heat sinks and would rather not risk it unless I got some sort of backup. Thanks for the suggestion though!
I had the opportunity to listen to PASS LABS production amps at a High End Show on Sunday. They are truly excellent amplifiers. I might buy one of these when I retire or something. In the meantime, I'll stick to MR. PASS's Citation 12.
Thank-you all for helping me understand the problems that I encoutered while finishing this amplifier. I guess if I have anymore questions, I'll make another post. Lastly, may I suggest a budget-style Pass Lab amplfier for consumers?😀
Allen
Thanks both for the tips on transistor selection Chris and Vince. I'll look for these parts in a few days cause I gotta get ready for school. Yes, it's finally starting!
Just yesturday, I accidentally turned the bias up to like 1400 for a second. Then I saw this tiny puff of smoke.
Amp still works, but I'm not sure how much damage I did to the amp. If I were to replace whatever that is damaged, what would it be? The IRFP240s? Class A would be nice, but I'm short of heat sinks and would rather not risk it unless I got some sort of backup. Thanks for the suggestion though!
I had the opportunity to listen to PASS LABS production amps at a High End Show on Sunday. They are truly excellent amplifiers. I might buy one of these when I retire or something. In the meantime, I'll stick to MR. PASS's Citation 12.
Thank-you all for helping me understand the problems that I encoutered while finishing this amplifier. I guess if I have anymore questions, I'll make another post. Lastly, may I suggest a budget-style Pass Lab amplfier for consumers?😀
Allen
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