GK-1 Stepped Attenuator

andyr · « **Reply #60 on:** 25 May 2008, 05:42 am »

Quote from: LM on 25 May 2008, 05:35 am

Thanks also Darren.

Guess from looking at the TKD pdf, a 2P65CS20KOhm would be the complete description. Interestingly, the S (or blank) is for 'click' or not and it seems to me a click would be useful. Just wondering what you had Darren. No price list at those sites so an enquiry is will be needed to ascertain the damage.

Yes, Darren and I have the "click-stop" version (an excellent feature BTW).

We bought the 25K version (stereo) but maybe this is no longer available?

Regards,

Andy

whubbard · « **Reply #61 on:** 25 May 2008, 06:04 am »

I asked THL about their prices before going with the 10k TKD from Michael Percy.
They charge 17500NT (they say NT, but its the same as TWD) which is about $575. Michael Percy is $250, and the price doubled on him, so he is selling them to us at a GREAT deal right now. If you want a TKD...now is the time to buy. I asked if he could get a 25k TKD, and he explained it would really cost around $500+, which is why I just stuck with the 10k.
They were also out of stock on the Vishay S102 250kOhm. Michael Percy is again, in stock, and also if you go with the 10k TKD you only need to use 120kOhm Vishays, which are once again, cheaper.

Hope this helps.
-West

LM · « **Reply #62 on:** 25 May 2008, 06:34 am »

I've emailed TKD so we'll see if direct is an option and at what price.

Funny how good my original pot is sounding right now compared to a $500 option. I'm sure 10KOhm is a good option.

DSK · « **Reply #63 on:** 25 May 2008, 06:59 am »

Yes, as AndyR said, we have the 25K version with the clicks (Steps). It is quite useful in returning to the same volume level (eg. when A/B'ing etc).

THL never listed the 25K version, even back when I was buying mine. I did approach TKD directly (http://www.tkd-corp.com/02_products/p_04variable_a.html) and received prompt and courteous responses. IIRC their pricing was similar to Percy and I think I may have gone with Percy as he could also supply the S102's.

LM · « **Reply #64 on:** 2 Jun 2008, 10:42 pm »

West,

Wondering if you have received and fitted the10KOhm TKD and bypass resistors yet and if so, what you think.

I still have the same dilemma as before. TKD got back to me and the cost of their attenuator ex factory is about 30% higher than the M Percy ‘old stock’ price. Not unreasonable if I ‘must have’ the 20KOhm version however the other bad news is that the manufacturing lead-time (at least for the 20KOhm version) is a month and a half. Hugh says that whilst the 20KOhm is ideal, a 10KOhm would be OK and it certainly is cheaper. My budget covers a DACT (or similar) right now but could stretch to the 10KOhm TKD now to use ‘as is’. However, this allows the possibility of the Crump/Vishay upgrade later as I know that you, Andy and Darren recommend.

So what I would like to understand, given my lack of electrical knowledge, is that given that 20Kohm is ideal but a 10KOhm perfectly OK, is the 20 worth the solid price premium that would largely pay for the bypass resistors if I ever go that way? Clearly, Andy and Darren bought 25KOhm versions, not 10. Secondly, might the careful choice of bypass resistors in the future restore optimal 20/25KOhm matching or am I really showing my ignorance here? Note: M Percy will be on holidays soon so ideally would like to make my mind up quickly.

whubbard · « **Reply #65 on:** 2 Jun 2008, 10:54 pm »

I'll leave it to Hugh to explain the sonic differnce between 20k and 10k, but I doubt its very noticable at all. Doubt its worth the 30%.

I have recieved TKD and resistors but haven't yet been able to hear it. My GK-1 is sitting on my desk and I've just gotten it built today (the board that is). I've still got to fit all the components (amps/asp/gk-1) into cases and wire them...oh and build the orions...before I get to actually hear the system.

Hopefully that will be sometime soon. I'm going to post a build thread in a bit.

Also the mod didn't have to do with the fact it was 20/250, it had to do with the resistor being 10x to 12x the TKD value.

Hope this helps!
-West

LM · « **Reply #66 on:** 2 Jun 2008, 11:52 pm »

Quote

Also the mod didn't have to do with the fact it was 20/250, it had to do with the resistor being 10x to 12x the TKD value.

West,

Hugh has said 'not much difference' to me. He may care to elaborate but essentially said this at a very early post

It does help but perhaps pretty clumsy wording from me for the 20 to 25K Ohm bit. I suppose to put it another way, I simply want to be sure that accepting the 10K option now won’t be any cause for regret later that I should have paid the premium for the 20K version. Clearly, you have decided it will be OK.

Also, I haven’t seen any diagrams on what is involved with the bypass upgrade so I have no clue as to what change if any they would make to the overall volume control impedance. I have looked at cct diagrams on the Goldpoint site about applying resistors at varying points to the input and output sides to change the SA response to better suit high or low gain amp situations and I wasn't sure if there would be any such considerations to look for in selecting resistors. Its just another reason why an SA alone for me is such a simple start point.

whubbard · « **Reply #67 on:** 8 Jun 2008, 02:45 pm »

LM,

I too asked Hugh about the difference between 10k vs. 20k and he said it wasn't much at all. So I wen't ahead I got the 10k, as I think it was worth the 30% discount.

Hugh,

Would you mind explaining the exact difference of 10k vs. 20k? How will the sonics be changed?

-West

AKSA · « **Reply #68 on:** 8 Jun 2008, 11:58 pm »

West,

No difference at all - the Zout of the SS section is just 32 ohms, so 10K, 15K, 20K, it's mere bagatelle for the driving circuit.

Cheers,

Hugh

LM · « **Reply #69 on:** 21 Jun 2008, 05:20 am »

Well I went ahead and ordered a 10KOhm TKD from Michael Percy last Friday week and received it on Wednesday. Also ordered some Solens Caps as well though that’s a matter for another thread. Had all the new components fitted on Thursday and wired back in to my set-up on Friday night. Overall sound I’ll discuss in the GK1 thread but the TKD is certainly a beautiful instrument; I see now what Hugh and others have been commenting about so thanks to all that suggested it.

The taper is absolutely fabulous and with 40 positions, no problem whatsoever in finding a suitable volume position. The feel is precise and sound as clean as a whistle. I’ll keep the advice about Bob Crumps improvements in mind but at least for the time being, I am perfectly satisfied with using the attenuator stock or as is. Couldn’t recommend it more highly even though it has a bare 5 hours bedding in and I suspect there is much subtle improvement to come over the next few hundred hours or so.

DSK · « **Reply #70 on:** 21 Jun 2008, 07:21 am »

Quote from: LM on 21 Jun 2008, 05:20 am

... Couldn’t recommend it more highly even though it has a bare 5 hours bedding in and I suspect there is much subtle improvement to come over the next few hundred hours or so.

Bob Crump's words were "... approx 45 days of 24/7 ..." to fully break in! I didn't bother keeping track of hours. Like you, we heard an instant improvement from the TKD alone (then another smaller but worthwhile improvement when we added the S102's shortly after). I must say that with no other changes, the GK-1 sounded a little better (to a degree that only an owner would probably notice) a few months later ...my system gets nowhere near 24/7 play time. Bob felt that the S102's improved dynamics and transparency.

LM · « **Reply #71 on:** 21 Jun 2008, 09:24 am »

Quote

Bob Crump's words were "... approx 45 days of 24/7 ..." to fully break in!

That's both horrible news in the sense of ' I hope I can control my impatience' and great news in that 'you mean it gets better than WOW!'

Grumpy_Git · « **Reply #72 on:** 21 Jun 2008, 09:46 am »

Is that at each output step?

Nick

DSK · « **Reply #73 on:** 21 Jun 2008, 03:44 pm »

Quote from: Grumpy_Git on 21 Jun 2008, 09:46 am

Is that at each output step?

Nick

No, it is not a ladder.

LM · « **Reply #74 on:** 10 Jul 2008, 10:02 pm »

RonR,

I like all the others around here have really appreciated your efforts on another thread to test the various Cap options at C4/C7 etc but I was wondering if you had any worthwhile observations about the TKD you fitted that you could add here.

I ask because you say you repeated the tests after replacing your original Vishay stepped attenuator and I would love some clue as to nature of the TKD changes.

I know it was not what you tested for but I’m curious because I changed both the caps and attenuator at the same time and unless you can shed some light, will always be wondering what contributed what to the improved sound.

RonR · « **Reply #75 on:** 14 Jul 2008, 07:30 pm »

Lyn,

After putting the TKD attenuator in circuit I found precision / detail improvements, and also a better frequency balance, as though the response was "flatter" somehow.

My naked Vishays have now arrived, so I'm about to embark on the Bob Crump mod.

Question: Have any of you guys opened the TKD metal case and fitted the resistors inside? Those naked Vishays look very delicate, and I'd hate to trash one while fitting the attenuator in a case!

Cheers,

Ron.

whubbard · « **Reply #76 on:** 27 Jul 2008, 03:29 pm »

Inside? I thought they went on the outside.

-West

AKSA · « **Reply #77 on:** 27 Jul 2008, 11:06 pm »

Hi Ron,

My suggestion: put 'em on the outside of the case; you probably need three company certificates and a nice white coat to open the case on a TKD. Scientific Instrument, y'know!!

Hugh

ginger · « **Reply #78 on:** 30 Jul 2008, 04:45 am »

Just to throw an additional cat amongst the pigeons.

For a manual stepped attenuator I would consider this one from John Broskie.

http://glass-ware.stores.yahoo.net/tcj-stepped-attenuator.html

Its a little weird in that it has a central switch which switches left and right channels in 11 "coarse" 6dB increments and then the left and right switches give 6 1dB increment "fine" adjust for left and right channels respectively - thus you also get a "balance" option for free.

The net result is 66 attenuation levels in 1 dB steps.

Its a combination series and ladder attenuator. Basically the coase adjustment is done using the series resistors and the fine adjusts are ladder style.

$US160 PLUS resistor cost (you can fit what you like).

Using JB's "standard" resistor value options the Zin is 50K BUT you can scale up or down easily.

The series resistors will be more important than the ladder resistors to sonic results so you can even target the audio jewelry components to these positions.

Cheers,
Ian

RonR · « **Reply #79 on:** 4 Sep 2008, 12:26 pm »

Hi All,

The Crump mod finally made it into my GK-1. I used 120k Naked Vishay resistors on the outside of the metal case of my 10K attenuator.
TBH I did don my white coat and take a look inside the case, but I wasn't comfortable with shoe-horning the resistors in there.
After a couple of days I can say that the transparency has increased.

Cheers,

Ron