HK Citation I is now McShaned

[dshoaf]

Here's a project that's been on-again-off-again for a couple of years. This Citation I came to me as one of a group of pieces bought from a vintage SS receiver guy. He had little use for tube gear and didn't seem to know much about them outside of that they took tubes. For me, this and the Citation III tuner - without any tubes - came along with a group of older Dynaco pre/tuner stuff.

For me, the Citation gear rounded out the collection and I set to work rebuilding the Citation I's line stage with Jim McShane's power supply and coupling caps to see if the all the fuss was really there.

The Trough of Dis(re)pair....

Upon that stage of the project completed, I sat back to listen a bit only to find that there was far more channel imbalance than I could accept. Going back into the preamp's innards, I finally discovered that the culprit was the volume control itself.

Disassembly of this part showed that one of the wipers had pretty much torn itself up and had gouged a large chunk of carbon off of the pot. This caused the tracking of the dual-potted volume control to be waaaay off on one channel and was worse right in the middle of the normal listening range. Since the control itself was no longer linear in its tracking, no amount of using the balance control to offset the effects would work.

Further, I quickly discovered that there are no known replacements for this rather quirky 500K dual pot that has 2 separate taps on it: one for the Loudness function and the other connected to a resistor to 'linearize' it when set over 2 o'clock on the rotation. Jim and others sympathasized with me but offered no real alternative solution.

The Elusive Pot.....

The first attempt at a replacement pot was an ALPS 500K dual pot purchased from an Asian vendor via eBay. It installed in the correct position and worked quite well with one problem: It didn't have the knurled/split shaft to use the original knob with. That is, the ALPS shaft was solid and designed for a knob using a set screw arrangement on the knob. The old HK devices used a split shaft along with ribbed shafts so that the knobs just slipped on and were held in place by friction. Bummed again, I put the project away and went on with some others.

But the Sun Shines Again.....

This summer, I spotted another eBay seller offering a Stepped Attenuator and the auction picture showed a split/splined shaft that looked like the right length. When I received the package (received in 5 days from Hong Kong!), the shaft turned out to be solid just like the ALPS. It turns out, though, that the seller sent the wrong one and quickly made it right.

Success At Last......

The first picture shows the results of the installation of this stepped attenuator. It fits quite nicely and the shaft turned out to be the right length - well almost. The splines of the new shaft don't quite line up with the slots in the control knob but they do well enough that I only had to leave a bit of clearance on the volume control knob, as you can see from the second picture.

Looking from the front, you have to look closely to see that the volume control knob sticks out a bit more than the others. Given the effort to find a replacement for an NLA part, I'm happy with it.

Once the volume control was installed and confirmed to work properly, I finished out the recapping of the phono preamp as you can see from the next picture. While others say this is a difficult piece to work on, I found it has plenty of space to move around and replace the caps - there are a lot of them, for sure!

Lastly, you can see the Dynamic Duo Citation I and II in full heat-generating glory. Yes, I can confirm that these two amps sing exceedingly well with each other. Both have been fully McShaned (full power supply and coupling caps replaced).

Now, on to the Citation III tuner......

Cheers,

David

[NYListens]

Neat work. It looks great and I'll bet it sounds even better than it looks. Congrats!

[himm37]

Very nice work, I love the Stepped Attenuator install, has Jim seen that? I run my Citation II with a passive pre, but would love to find a Citation I. Two things about that shelf, it MUST be stronger then it looks:scratch2: and I know heat rises, but are you sure too much isn't radiating down into your vinyl?

[Bluelobster]

A couple questions: Have/Can you shim the volume control on the back side so that it isn't out as much?
It doesn't look bad at all where it is, probably really only noticeable to you. Can you give some particulars as to where and what you got so the rest of us don't have to suffer the misery of failure or the joy of discovery?
What are the coupling caps your using? The rectangular ones on top of the boards. Silver Mica?

[dshoaf]

A couple questions: Have/Can you shim the volume control on the back side so that it isn't out as much?
It doesn't look bad at all where it is, probably really only noticeable to you. Can you give some particulars as to where and what you got so the rest of us don't have to suffer the misery of failure or the joy of discovery?
What are the coupling caps your using? The rectangular ones on top of the boards. Silver Mica?

Good idea on the shimming to pull the knob back into place. The issue is that the shaft is tight enough that I cannot push the knob all the way onto it. I thought about shimming the attenuator but then the locating pin will not hold it in place outside of using a big-time star washer to lock things in place. My logic is that the knob in its normal position causes rather a bit of wear on the faceplate - you see a number of these that have that problem, mine included. Why not just have it further out anyway to slow that wear?

The part came from an eBay vendor, Parts and Audio (http://stores.ebay.com/Parts-and-Audio). Apologies for not sharing that to begin with. I don't think Jim has seen this but I'll send a note over to him with this thread.

The LP racks came from Tony's Woodshop (www.tonyswoodshop.com) in Pennsylvania. Nice guy and I've used those same frames to ship the LPs cross country when I moved last year. I do have a top and bottom for them, too, but they're not out of the boxes - yet.

I agree that they do generate some intense heat and I'll be putting a fan on the assembly very soon for that reason. They're not radiating down as much as I thought they might. I do appreciate the concern, too.

On the coupling caps, the rectangular ones are the polypro caps that Jim supplies in his kits. There's a logo that looks like this :N: on them but I have no idea who the supplier is. The smaller ones of nearly the same color are silver/micas.

Cheers,

David

[sloober]

I love that volume control. Looking on the parts and audio site it says 24 step. Does that mean there are 24 steps of level? Seems like it should have more by looking at all the resistors. I have heard these are the best type of level control. Not sure it would fit into many units because of it's size.
On the knob sticking out, try making a small felt washer behind the knob.

[spartanmanor]

Beautiful! I am/was 95% done with a full restoration on mine. It has been lost in the mail for almost 3 weeks as I shipped it off to be finished up. It was going out of country so I just hope it was held up in customs. I am starting to bum a little though. I had replaced almost everything it it as well and I cannot tell you the amount of time I have wrapped up in this project.

[spaceman]

Nice work, dshoaf! :thmbsp: I just ordered the kits & knobs last week for mine, so it'll be awhile till I can catch up. ;) I got a good start on refinishing the wood case, but that front moulding/trim is gonna take some time. :yes:

[dshoaf]

Good on ya, Spaceman. I hope you'll enjoy it. I don't have a cabinet and probably wouldn't want one considering how hot the preamp gets. I'm working on that part next.

I do recommend making a place to work on it where you don't have to put it all away after each session. And allocate time to work on it in pieces. I really needed to step away after about 4 or 5 caps replaced. And start with the power supply first.

BTW, I don't wish the volume pot replacement on anyone. I spent quite a bit of time trying to repair the old one, then fit the ALPS, then search around for the stepped attenuator.


Cheers,

David

[Bill H]

Just curious, what output tubes are you using in the Cit II?

[Freo-1]

Just curious, what output tubes are you using in the Cit II?


Well, I've got a modified Citation II, and I'm using NOS Tung Sol 6550's. They sound the best of all the 6550/KT88 types I've used.

[dshoaf]

Just curious, what output tubes are you using in the Cit II?

I've got the EH KT-88s in it now but also have run the EI KT-90 Type IIs in it as well. Both are excellent. That's them in the picture, too. Generally I'll run the EH's mainly because the others are so hard to find - I've got 2 sets of the EIs.

The newest KT-88s, though, are getting me interested in trying them at some point. The thing is that I'm quite happy with the EHs to the point where I really don't want to mess with anything else for now.

Too many other projects.....

Cheers,

David

[Bill H]

Currently, I use winged C KT-88. I do have a set of Tung-sol Reissue 6550 but was afraid that the Cit II would have been too much for them. I REALLY want to give the Reissue Gold Lions a shot but am looking for anyone else who has guinea pig them........

[Ciscokid]

Nice work on the Cit I volume control. Was the POT swap straight forward? Did the new POT have all the necessary connectors or did you have to improvise?

ck

[WopOnTour]

Currently, I use winged C KT-88. I do have a set of Tung-sol Reissue 6550 but was afraid that the Cit II would have been too much for them. I REALLY want to give the Reissue Gold Lions a shot but am looking for anyone else who has guinea pig them........I am currently at over 11 months of DD (driven daily) Gold Lions (carefully matched and provided by Jim McShane) and I absolutely LOVE them in my Deuce.
I'll be ordering a backup set or two from Jim. After trying everything from vintage 6550 Tung-sols to Shuguangs, EH and yes, even the Ei KT90 (also from Jim) I have yet to hear another tube deliver the musicality of the reissue Gold Lion in my Citation. To be fair I've never heard the "original" Gold Lions either but if Jim teels me these are "as good or better" sounding- that's good enough for me.

Apparenly there has been a handful of early failures and a couple of "run aways" with this tube in certain amplifiers.
But I've never heard anyone using these in the Citation II encounter anything but musical bliss.:thmbsp:
WopOnTour

[dshoaf]

Nice work on the Cit I volume control. Was the POT swap straight forward? Did the new POT have all the necessary connectors or did you have to improvise?

ck

Thanks to all who have commented on this little project.

This pot has all of the laddered resistor pairs exposed so its easy to get the thing installed electrically. The challenges have been in the physical aspects of the 1) splined and split shaft, 2) the proper length of the shaft and 3) the depth of the attenuator that would not cause other interference in the chassis.

I only had to solder the original 3 leads to the old pot onto the proper terminals of the stepped attenuator. The pot itself doesn't have documentation with it so I had to figure out with an ohm meter what was what.

I have not - yet - hooked up the Loudness tap mainly because I haven't taken the time to figure out where along the stepped attenuator tabs I need to connect it. Frankly, I don't use it anyway. On the original, there is also a separate tap that, I believe, is used for linearizing the pot's taper. Its not hooked back up either as I don't believe I'll be needing it. Certainly doesn't need it according to my ears.

Cheers,

David

[Freo-1]

I am currently on approx 11 months of DD (driven daily) on my Golden Lions (carefully matched and provided by Jim McShane) and I absolutely LOVE them in my Deuce.
I'll be ordering a backup set or two from Jim. After trying everything from vintage 6550 Tung-sols to EH and yes, even the Ei (also from Jim) I have yet to hear another tube deliver the musicallity of the reissue Gold Lion. To be fair I've never heard the "original" Gold Lions either but if Jim teels me these are "as good or better" sounding- that's good enough for me.

Apparenly there has been a handful of early failures and a couple of "run aways" with this tube in certain amplifiers.
But I've never heard anyone using these in the Citation II encounter anything but musical bliss.:thmbsp:
WopOnTour

I have used the GL KT88's in my Mod Citation II, and they do sound excellent. I have to say though that the NOS Tung Sol sounds better then the GL KT88 in mine. It should be noted that the front end in my amp uses 5687 triode as opposed to pentode, and the bias setup is more robust/stable than a standard citation II. The triode front end is more open and detailed sounding, so that perhaps makes a difference.

I have had reliability issues with the GL KT88, but may have come up with a work around to the issue, which involves tightening the socket pins, and ensuring the centering pins are true.

[Jim McShane]

What are the coupling caps your using? The rectangular ones on top of the boards. Silver Mica?

The reddish brown caps are Matsushita/Panasonic film/foil polypropylene with OF copper leads.

Sadly they are now NOS, they have been discontinued... :sigh:

[Jim McShane]

Currently, I use winged C KT-88. I do have a set of Tung-sol Reissue 6550 but was afraid that the Cit II would have been too much for them. I REALLY want to give the Reissue Gold Lions a shot but am looking for anyone else who has guinea pig them........

Hi Bill!

The reissue T-Sols aren't stout enough, don't use them. And regarding the SEDs - let me just say there are much better choices.

The reissue Gold Lions work really well.

Note: I am only posting because I came here to see David's pics, I don't read this forum anymore. I'll catch you all elsewhere around the web (I hope)!

[WopOnTour]

I have used the GL KT88's in my Mod Citation II, and they do sound excellent. I have to say though that the NOS Tung Sol sounds better then the GL KT88 in mine. It should be noted that the front end in my amp uses 5687 triode as opposed to pentode, and the bias setup is more robust/stable than a standard citation II. The triode front end is more open and detailed sounding, so that perhaps makes a difference.I have had reliability issues with the GL KT88, but may have come up with a work around to the issue, which involves tightening the socket pins, and ensuring the centering pins are true. Yea yea, I remember you talking about your "top secret" front end before. But I don't buy it. If I recall you were not able or willing to post full details of the so-called enhancement or the operating points. Until such time...
WOT

[Freo-1]

Yea yea, I remember you talking about your "front end" before. But I don't buy it. If I recall you were not able or willing to post full details of the so-called enhancement or the operating points. Until such time...
WOT


Don't knock what you have not heard. It's not exactly a Soviet state secret that triodes offer advantages over pentodes, mate!

But, just do not take may word for it. Read for yourself:

http://www.spectrum.ieee.org/print/1640


Go to the last section that talks to distortion.

PS: I will post the schematic if I ever get time. Who knows, you may even do this yourself? :scratch2:

[WopOnTour]

LOL
Barbour's 10-year old article? You're kidding right?

A few months back you were on here making a big deal over your supposed early and repeated failures of the Gold Lion's (and taking Jim to task on them) and now apparently the "workaround" is merely fixing up your bad socketing?
OMG that's Chapter One- "Why tubes run away..."

So I'm not saying it's impossible but I highly doubt you've stumbled on significant improvments to the Citation II front-end after many dozen respected EEs and tube scientists have attempted the same and failed. So put up or shut up.
WopOnTour

[Freo-1]

LOL
Barbour's 10-year old article? You're kidding right?

A few months back you were on here making a big deal over your supposed early and repeated failures of the Gold Lion's (and taking Jim to task on them) and now apparently the "workaround" is merely fixing up your bad socketing?
OMG that's Chapter One- "Why tubes run away..."

So I'm not saying it's impossible but I highly doubt you've stumbled on significant improvments to the Citation II front-end after many dozen respected EEs and tube scientists have attempted the same and failed. So put up or shut up.
WopOnTour


I hate to tell you this, but this is simply not accurate. Ever hear of Music Reference? Their position (and you can review the data on Audio Circle) is that there are a number of issues with the Citation II design (including amp osscillations ) that are part of the original design that are considered shortfalls. It's more than a opinion.

The article in reference is a valid today as it was when it was written. There is no time limit on physics.

The issue with the tube runaways is valid, and people have had them. My buddy was the one who worked out the issues with the pin sizing and centering. I'm just passing the data along. The blue light shows are tube problems, period.

I'll look around and post the the schematic when I find it and get a chance. Don''t get me wrong, I love the Citation II. However, The original design can indeed be improved, and one needs to keep an open mind.

[dshoaf]

Gentlemen, please take this off topic discussion to another thread or, better yet, PM each other.

I started this thread here for others to know that there is a replacement option for the Citation I's volume pot - a NLA part. Let's keep it that way.

Cheers,

David

[Freo-1]

Gentlemen, please take this off topic discussion to another thread or, better yet, PM each other.

I started this thread here for others to know that there is a replacement option for the Citation I's volume pot - a NLA part. Let's keep it that way.

Cheers,

David

You are right, and we drifted off topic (Sorry about that).

We shall take this up in a new thread after I post the schematic.

By the way, very nice work on the Citation I. I wish I could hear it. :thmbsp:

[WopOnTour]

Yes, sorry David
We went a bit astray there...

One question I had for you regarding your addition of the stepped attenuator into the Cit 1 (I have done the same on a few HK integrated tube-amps amps, however never a Citation preamp)

Where exactly did you "tap off" the stepped unit for the contour switch circuit and the 100k pull-up resistor? FYI I have found it neccessary to play around with this a bit moving these taps one resistor up or down often with noticable improvement in the loudness control linearity and contour switch behavior.

Nice job
Regards
WopOnTour

Thanks
WopOnTour

[EasyRiderNYC]

Is that a step up transformer on top?

[dshoaf]

Where exactly did you "tap off" the stepped unit for the contour switch circuit and the 100k pull-up resistor? FYI I have found it neccessary to play around with this a bit moving these taps one resistor up or down often with noticable improvement in the loudness control linearity and contour switch behavior.

WopOnTour

Well, that's the next step, actually. Right now, I've got both the 100K tap and the Loudness function disabled. The 'selling feature' with the stepped attenuator is that only 2 resistors are switched in at any one time. This means that the continuous resistive effect of a standard pot isn't available and, so, the Loudness contour feature can't be implemented the same way. For me, this isn't a real issue but others will want all the functions on the usable. I'm sure some of us here can figure out an alternative but, for now, I'm really enjoying the real improvements from the new volume control.

As for the 100K tap, this will not be needed even if I used an Alps pot or a stepped attenuator in there.

Thanks for the compliments, too. It really is a nice preamp and the phono section is, indeed, almost dead quiet.

Cheers,

David

[dshoaf]

Is that a step up transformer on top?

Yep, it 'tiz. Sorry I didn't clean up for the picture.

That's one of those Hammond aluminium boxes with a set of Lundahl step up transformers inside. I've got it set up for the Denon DL-103R I use occasionally. By having it in its own separate box, I can pull it out quickly when I use a MM cartridge. The loading resistors for the Denon are inside so I don't have to dink with any of that stuff when moving back and forth between MC and MM carts....I'm lazy....

Cheers,

David

[Jim McShane]

David,

Thanks so much for the hard work, and for sharing it with everyone.

Regarding the knob... it may be the solution is to get some knobs specially machined to accept either the attenuator you used or another widely available high quality piece. The problem is that in small quantities they'd be pretty darn expensive.

The other problem is that the balance pot is subject to the same deterioration as the volume pot - and it's really difficult to find any balance pots that could fit. Here again, I've toyed with the idea of a "balance trim" switch instead of a pot. More details on that soon (hopefully).

Just so everyone knows, I've approached a couple makers of good quality pots about reproducing the Cit I volume pot. They obviously didn't want to do it. One sent me my sample back with a note that just said "no way". The other said if I bought 1,000 they might consider it. Obviously that's way more than I can use.

It is also possible I can get a pot maker just to make replacement carbon elements, but I've got no progress to report right now.

So David's solution is absolutely the best there is.

Please - if you have a bad control - volume or balance - DON'T THROW IT AWAY! There may be salvageable parts - i.e., one good carbon element and one bad, etc. Let me know if you do, maybe it'll help someone else get theirs going.

[targeteye]

Is this the pot you purchased?

http://cgi.ebay.com/24-Step-Volume-Control-500K-A-Dale-resistor-Stereo_W0QQitemZ220236497301QQihZ012

I haven't even started on my Citation II restoration yet and Don't have a Citation I yet (to be my next major purchase). However, if its that hard to find a replacement Volume control I might go ahead and pick this one up while they are available.

Steve

[dshoaf]

That's the one, Targeteye. I'm much like you in that I'll pick something like this up when they're available rather when it is needed.

Cheers,

David

[WopOnTour]

The 'selling feature' with the stepped attenuator is that only 2 resistors are switched in at any one time. This means that the continuous resistive effect of a standard pot isn't available and, so, the Loudness contour feature can't be implemented the same way.That's a "ladder" type stepped control, but you can also purchase a "series" type which uses the same resistor value throughout (typically 22K for a 500K 23-step unit)
This is what I used and then was able to tap off for the contour switch and pull-up.While generally emulating the original linear volume control the disadvantage of this type is an increase in the input impedance as the volume is turned down, which is eliminated with the ladder type stepper.
I like the contour setting on most of the HK amps as it seems to widen the sound stage, for me at least.
WOT