A couple resistor and transistor questions

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abuttino

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Bought a Denon on eBay, looks brand new, major issues on the 5ch amp board.

With the help of the service manual, I've nailed it down to some 22ohm/1W, .47ohm/2W and 3 channels of 2SD2560P/2SB1647P

First, I would like to ask, how important the "P" is on those transistors. The DC current gain is the difference. Encompass seems to be the only way to guarantee the 'P' rank transistors.. Unless that number doesn't mean much.

Also, Encompass seems to be the only company I can find those white/green shielded resistors, I was hoping for ideas that can benefit in a couple ways.. Maybe a different brand would help the wallet AND sound better? $7 per resistor seems a little steep.

I would like to get these parts soon, most of them are on backorder at Encompass... So, any suggestion you have is greatly appreciated
 
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abuttino said:
I understand, this isn't the average amp. Upscale.
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I haven't done much in audio for a while but the receivers using high-gain Darlington output resistors used to be looked down upon as inferior designs ("like a Sony"). The tides seemed to turn in the past 20-years. I guess someone figured out how to make better darlingtons.
 
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Is there a reason to buy these transistors from Denon? Sanken makes them and the only thing I see different is they are bent properly for the board if bought from Denon.
 
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abuttino said:
I understand, this isn't the average amp. Upscale.
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It's a multi-channel surround sound amp, I never find them particularly impressive, too much crap squeezed in to too small a box - you get better quality from a decent stereo amp.

However, the amplifier has relatively little effect on the sound, it's pretty easy to make a decent sounding transistor amp, it's the speakers which make the vast amount of difference.
 
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Nothing wrong with Darlington's, most amps use two discrete transistors as a Darlington anyway.

It's just typical snobbery from the supposed 'Audiophiles' (otherwise known as Audiofools).
 
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abuttino said:
Is there a reason to buy these transistors from Denon? Sanken makes them and the only thing I see different is they are bent properly for the board if bought from Denon.
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No reason at all - however, you need to be VERY, VERY aware that there's an awful lot of fake transistors out there, with audio outputs a common target.
 
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Tony Stewart said:
for a great example of carbon noise, put a 9V or a 1.5V battery across any old speaker !!
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Tony, since you are new around here let me give you a little help. Your comments will draw more favorable responses if you include a schematic drawing to illustrate your ideas.

ak
 
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AnalogKid said:
Tony, since you are new around here let me give you a little help. Your comments will draw more favorable responses if you include a schematic drawing to illustrate your ideas.

ak
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Does that mean you'll post a schematic anytime you give the advice to "put a capacitor across the power rails" or something else as straightforward?

Take his description as it is written. It make not make sense to you before you try but it will make sense once you try.

And, I don't recommend leaving it connected for a minute but the effect will be noticeable after the first two seconds.
 
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Nigel Goodwin said:
I don't quite see what you're on about?, if you do that the cone just deflects, and the speaker makes no noise - and it may very well overheat and burn out.
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Deflection is one effect but, if you open your ears when you do it, you may learn something about noise. It will be apparent long before the speaker burns out.
 
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AnalogKid said:
Tony, since you are new around here let me give you a little help. Your comments will draw more favorable responses if you include a schematic drawing to illustrate your ideas.

ak
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Ha ! Just for a few seconds to avoid overheating to hear the hot electrons jumping out of the battery carbon rod. It's not loud, but you can hear it. An old 12" speaker is louder.
 
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Tony Stewart said:
Ha ! Just for a few seconds to avoid overheating to hear the hot electrons jumping out of the battery carbon rod. It's not loud, but you can hear it. An old 12" speaker is louder.
View attachment 144399
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I think there was an old Microchip application note to use a carbon resistor and a high-gain op amp to make this noise and use whatever ADC value you capture as a seed for a random number.
 
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I'm having an extremely hard time finding the transistors for this project.

Apparently the 2SD2560 and the 2SB1647 (both P Rank) are just hard to find, if not impossible.

What can I do? Use an O or Y or, wait?
 
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abuttino said:
I'm having an extremely hard time finding the transistors for this project.

Apparently the 2SD2560 and the 2SB1647 (both P Rank) are just hard to find, if not impossible.

What can I do? Use an O or Y or, wait?
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I think the P version is in the middle of the overall range of gain and the P-zone overlaps with the zones of the other two sub-versions. I think you'll be pretty safe ordering a random (unspecified) transistor and cross your fingers that it falls in the range. If not, it will be rare occasion that you'll need the exact specified capabilities of the P version - especially since the amplifier circuit has a feedback loop to control the output.

Worst case (if you end up with a "O" version is some clipping of the output signal if you run full volume and there is not enough current to reach the targeted voltage through a low impedance load.

Worst case if you end up with too much gain is that the signal in your preamp circuit will be slightly compressed - that may cause some very minor issues with accurately replicating the signal accurately but this should be a very, very minor issue.

Summary, use any version you can find.
 
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The good thing is, this amp will only be handling 5 channels of the 13 I plan to use, most will go to another amp in the back of the room that handles everything, subs get their own pre-out.

Just want to get this project finished. DigiKey sent me some Y 2560s, so, either I'll match them or order a full group from Japan. Chip one stop is listed on Sanken's site and they have unspecified ones. Or, the P's on backorder forever.
 
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I'm hoping somebody can help me out. I replaced 2 blown transistors (A1695 & A4468) in a Yamaha Rx-v681. I got a lot of 6 pair of them. The other ones in the receiver give a reading of about 130. The blown ones show 1 and there is visible burnt marks by them. All the new ones show 1 also. The only difference in the numbers of the new transistors is the number after the main number is 66P. The old ones have 67P.
I did not power it up yet because I am going to replace the emitter resistor.
Are these transistors the right ones?
 
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What do you mean by 'show 1'?, if that means reads 1 on an ohms test, then the new ones are dead as well - bear in mind there are huge numbers of fake power transistors out there.
 
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