The Citation 16A resurrection project

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taj

diyAudio Member
Joined 2005
I've inherited a great project. I was given a Harman Kardon Citation 16 chassis including power transformers; heatsinks with output devices and emitter resistors; and the protection relay PCB.

What I didn't get was the main "driver" PCBs -- the main amplifier circuit itself. And the amplifier was a plain-faced version which didn't come with those trademark V shaped LED arrays.

So my project will be to re-create the missing parts for this puppy based on the information contained in the service manual for the Citation 16A, the discrete version of this amplifier. I will create all the missing circuit boards and add the LED arrays for fun.

But I'm going to need help since I'm just learning electronics. Especially given the age of this circuit and its parts list. Hence the thread.


..Todd
 

taj

diyAudio Member
Joined 2005
The first question that comes to mind is regarding some nomenclature in the parts list...

Many of the small signal transistors are labeled PNP GP or NPN GP. Does the GP just mean "general purpose" so that my pile of 2n5551/5401's will fit the bill?

And for the input differential pair (a nameless dual NPN job), will a pair of matched, thermally coupled 2SC2240's be adequate? They are low noise, linear...

..Todd
 

taj

diyAudio Member
Joined 2005
By the way, I've created drawings for all of the PCB's for DIY board etching. They are PDF files meant for printing out and home etching, not Gerber files for professional manufacturing. All the boards are single sided.

I don't know how to use any of those PCB CAD programs. But I am a technical [computer] illustrator, so the drawings are quite satisfactory, and accurate since I traced the parts layout from the service manual (with a few minor tweaks here and there).

Anyone wanting the drawings is welcome to them. Just send me an email.

..Todd
 

taj

diyAudio Member
Joined 2005
I intend to set up a web page eventually for this project with photos of the progress (or lack thereof) but it's not a priority, so email contact will have to suffice until then. If I do that, I will post a link. :dead:

The email button in DIYAudio should work. Or you can use...

100 amps at g mail dot com (with spaces removed and at/dot replaced appropriately).

..Todd
 
OK, you might notice that everything to the left of Q12 and Q13 operate at a reduced supply voltage of +/- 10V. This is not commonly done, and you might notice the unusual 2 stage VAS employed to get from the lower front end voltage to the full output voltage. Interesting that it is similar to the Tiger output stage that I have commented on in other threads.

They're running the front end at a reduced supply so that they can use lower voltage/power transistors better suited to the job.
My guess would be BC547C and BC557C for all in the front end.

Duals are discussed in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12870&highlight=

The fact that the emitters share a common pin should be a hint as to the correct device. This is a disadvantage since no emitter degeneration can be used. I prefer the LM394 but it is not what was used since the emitters do not share a common pin.

Pete B.
 

taj

diyAudio Member
Joined 2005
Hi PB2,

Interesting comments. Thanks.

I certainly have no concerns regarding the reliability of Citation 16's.

The stability of Citation 16's is, however, is a subject I'm not qualified to comment on, though I haven't heard of any oscillation issues with these. Anyone?

I haven't looked closely at my output devices or drivers yet, but they are easily substituted/replaced if need be, albeit in an all-or-nothing ($$) manner.

These amps have proven themselves to my satisfaction. They certainly aren't at Pass or Kress level, but they are a well-respected classic amp, and I'd love to rebuild this puppy for the nostalgia & fun of doing so.

We used to torture these things in our 70's garage band. I don't recall what they sounded like, but it wouldn't have been relevant anyway, since I believe it was driving old JBL phenolic diaphragm hi-mid horns and 15-inch low-mid cabinets. All fed horrid cover music by a bunch of 14-16 year olds, through $25 microphones and $150 mixers. I think the 'torture' applied to the drummer's parents upstairs too, who probably wanted their prized Citation 16 back in the Hi Fi cabinet where we borrowed it from.

..Todd
 
Yeah, that's fine, if you have hands on experience then go for it. I was just being cautious.

I only just took a closer look at the output stage, didn't notice earlier that it is Quasi-complementary and uses RCA outputs.

It's older than I originally estimated so the input transistors would more likely be 2n5210 and the complement. I suggest you try to find out what the correct devices were and if they were matched.

It's fine if you want an authentic restoration, go ahead enjoy!

Pete B.
 

taj

diyAudio Member
Joined 2005
Hi Pete,

You meant RCA inputs I hope. It uses normal binding posts for outputs. Yes, it's a QC output section with TO-3 drivers sharing space on the heatsinks.

Oh wait. You mean RCA output devices. Doh. I'm a little slow. Okay a lot slow.

You're absolutely right. I should find out what the original input section transistors were, and go from there. I've been searching and looking but I can't find that information.

Does anyone with a Cit. 16 know? Are the devices marked?

Thanks,

..Todd
 

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taj

diyAudio Member
Joined 2005
Hi EchoWars,

I'm not so sure you used the 15004s unless you de-Quasi'ed the output section. :D

I also recall DJK recommend using 15024s I think. So the output section isn't a problem to re-construct. The input section has me a bit frustrated though.

It looks to me the like the input section transistors need to be rated about 30v/30mA, but other than that I don't know what I'd be looking for. Can anyone tell me which parameters would be significant when trying to match a device to a circuit (in this case the current mirrors and the diff. amp)?

BC550/560 look good to me based on electrical tolerance and noise.

..Todd
 
taj said:
Hi EchoWars,

I'm not so sure you used the 15004s unless you de-Quasi'ed the output section. :D
My bad...just used to listing both NPN and PNP.
I also recall DJK recommend using 15024s I think. So the output section isn't a problem to re-construct.
No indeed. There's lots of suitable transistors for the output.
The input section has me a bit frustrated though.

It looks to me the like the input section transistors need to be rated about 30v/30mA, but other than that I don't know what I'd be looking for. Can anyone tell me which parameters would be significant when trying to match a device to a circuit (in this case the current mirrors and the diff. amp)?

BC550/560 look good to me based on electrical tolerance and noise.

..Todd
Looks like an LS313 would do for the dual NPN input, but since the board has all six pads available, you can match your own.

What you decide in is really a matter of preference, as there are tons of devices that would do the job well. I would not get to hung up on noise specs. Since it 'appears' that the small signal devices are all EBC layout, the BC parts might be a good way to go. Zetex transistors, which I am fond of, are also EBC layout, so that's another possibility...using something like ZTX694B and ZTX795A. I'd match a couple of ZTX694B's with gains over 1000 for the input pairs and the Q8 current source, and use the BC devices for the rest.

Is there something funky with the input impedance that I don't see that makes the use of a huge 100µf input cap necessary?
 
If you like Krell, the KSA-50 is a simpler design than this HK, and could be scaled up for voltage/power:
http://www.diyaudio.com/forums/showthread.php?postid=490398#post490398

The builders here may have already done this, have not read the thread carefully. I'd reduce the output bias to perhaps 20W/ch at idle.

Not saying that this is the best design, just better than the HK.

Pete B.
 

taj

diyAudio Member
Joined 2005
EchoWars said:
Zetex transistors, which I am fond of, ...

That's great info. I've steered clear of Zetex just because of unfamiliarity, and a general lack of mention in these forums. So your suggestions will probably be of interest to a few others as well (assuming others read this).

Just curious, why is high hFE important for the diff amp?

..Todd
 
I also recall DJK recommend using 15024s I think. So the output section isn't a problem to re-construct. The input section has me a bit frustrated though.

Use the MJ15024's like DJK suggested.

And for the input differential pair (a nameless dual NPN job), will a pair of matched, thermally coupled 2SC2240's be adequate? They are low noise, linear...

Just match a pair of 2n5551's for the front end.
 
Just curious, why is high hFE important for the diff amp?
The higher the gain of the input pair, the better. This sets the input impedance of the amp, and the 'inner' transistor accepts the feedback from the amp output. Sloppiness here from low hfe will show in the final product.

Zetex makes a lot of transistors which are quite nice for audio use...I use a lot of the ZTX694B, ZTX795A, and the ZTX1056A.
 
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