GK-1 Stepped Attenuator

0 Members and 1 Guest are viewing this topic. Read 28511 times.

kyrill

Re: GK-1 Stepped Attenuator
« Reply #20 on: 12 May 2008, 11:22 am »
this is also not an expensive alternative from a well known source


RCA1 Remote Control Option 1 Kit              $159.00



http://www.welbornelabs.com/remote.htm

Seano

Re: GK-1 Stepped Attenuator
« Reply #21 on: 12 May 2008, 11:01 pm »
.....this is the option that I'm considering as part of my repackaging of my GK-1. Though only as volume control as I suspect that the source control part could be a tad fiddly to implement on the GK-1 output board..........maybe?

gerado

  • Jr. Member
  • Posts: 123
Re: GK-1 Stepped Attenuator
« Reply #22 on: 12 May 2008, 11:38 pm »
Mmmm..

How do these compare soundwise to stepped attenuators. I assume they do not have a mechanical resistor step and work by electronic wizardry therefore would they degrade the sound in comparison?

Theo

TomW16

Re: GK-1 Stepped Attenuator
« Reply #23 on: 13 May 2008, 01:07 am »
I went from a old passive pre with an Electroswitch ladder attenuator (offered by Sonic Frontiers years ago) to the Welborne passive with no sonic degradation that I could perceive.  I switched passives because the Welborne has a remote control volume control  :thumb:.

Cheers,
Tom

AKSA

Re: GK-1 Stepped Attenuator
« Reply #24 on: 13 May 2008, 01:11 am »
Hi Theo,

No, premium quality resistors, with gold plated relay switching.  The digital circuits you see are for the remote control function.

Strongly recommended.  I deeply respect Ron Wellborne, and also Jim Hagerman, both incredibly good production engineers.

Cheers,

Hugh

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #25 on: 13 May 2008, 11:59 pm »
Thanks Kyrill,

Darn it. :duh:  Just when I was thinking it was as simple as buying a DACT or similar high quality simple replacement item and that I’m quite prepared to give up a remote and couch potato status, you go and provide a further decision point.  Sarcasm aside, thanks – more food for thought though. :thumb:

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #26 on: 19 May 2008, 11:09 am »
Just to keep the stepped attenuator discussion on this thread.

I have researched as best I can, the bulk of the Stepped Attenuator options available to me.  The overall prices for good quality switches seem to range from about $150 to $250 landed in Oz  (TDK a bit more) so for convenience, perhaps the 20kOhm DACT at $195 sourced from an Oz distributor is reasonable.  I must admit that I agree with Hugh and Theo here, not cheap so I hope, well worth it.  Makes cap upgrades other than the Platinum seem a positive bargain.

My only remaining concern is that even with my relatively inefficient Vanderstein’s at moderate to high volume, I rarely have the original volume control pot turned beyond about 90deg from ‘off’ out of the approximate 280deg rotation available.  In fact, that’s only with the phono selected and it’s rarely beyond about 45deg with CD selected, such is the gain and grunt of the Soraya.  I’m just a bit concerned that after looking at the DACT specs, I’ll be in the courser 4db or more per stop attenuation area for common listening levels.  What do those who have fitted a DACT or other SA say?  Am I concerned over nothing or should I look at other options?


andyr

Re: GK-1 Stepped Attenuator
« Reply #27 on: 19 May 2008, 11:18 am »

Just to keep the stepped attenuator discussion on this thread.

I have researched as best I can, the bulk of the Stepped Attenuator options available to me.  The overall prices for good quality switches seem to range from about $150 to $250 landed in Oz  (TDK a bit more) ...


You get what you pay for, Laurie.

The TDK is a lot more ... when I bought it in late 2006, it was USD250 then there were the 4 Vishay S102 bypass resistors at USD30 each.  I suggest if you don't go for the "ultimate" (TKD plus Bob Crump's S102 bypasses) then you may as well go for a non-TKD attenuator ... which will be much cheaper.

If you want your GK-1 to remain in your system for a very long time (ie. so it can't be bested under $10K!  :D ) ... go for the TKD/Vishay combo.

Regards,

Andy

DSK

Re: GK-1 Stepped Attenuator
« Reply #28 on: 19 May 2008, 01:15 pm »
One of the other benefits of the TKD is that it has 40 steps of 0.5 to 1dB.

In late 2002 I was trying to figure out whether to go with DACT, a Goldpoint ladder or something else in my GK-1. I exchanged a number of emails with the late, great Bob Crump on the matter. He had spent some years evaluating just about every attenuator under the sun, including pots, shunts, series and ladders with a variety of resistors and bypasses etc etc. In the end, the TKD with S102 bypasses was the best he found and it became the attenuator of choice for the cost no object CTC BlowTorch pre-amp (~US$15k). I believe it was also used in the $$$$ LAMM Reference 2 (I think that was the model). Bob's advice was that if I was considering an attenuator solution anywhere the cost of the TKD/S102 combo, I may as well spend the bit extra and get the best. He also advised that he had tried a large number of different bypass resistors but none approached the Vishay S102 on the TKD. After a series of emails with Bob through 2003 I eventually pulled the trigger in March 2004 and did just that.

A word of warning though, it does need a fair bit of space to mount and it mounts with 3 machine screws through the front panel (hidden behind the volume knob). It also has a fairly lengthy break-in period to sound its best, though Hugh and I thought it sounded excellent from new. I heard a while back that the price had gone up even further and Michael Percy wasn't going to stock them any more as a result. However, last I heard they were still available from Japan where they are made.

How much better does it sound than the likes of the DACT or GoldPoint ladders etc? I have no idea. I didn't have the time, money or energy to repeat for myself the evaluation studies performed by Bob. I trusted Bob and have never regretted it.

« Last Edit: 19 May 2008, 01:26 pm by DSK »

AKSAphile

  • Jr. Member
  • Posts: 128
Re: GK-1 Stepped Attenuator
« Reply #29 on: 19 May 2008, 01:31 pm »


Found on web: http://electronics.dantimax.dk/Kits/Selectors_-_attenuators/index.html


A lot of different options available and prices are very good too :D

andyr

Re: GK-1 Stepped Attenuator
« Reply #30 on: 19 May 2008, 10:30 pm »


Found on web: http://electronics.dantimax.dk/Kits/Selectors_-_attenuators/index.html


A lot of different options available and prices are very good too :D

If the prices are attractive, why not just take the cheapest?  At least there's some logic behind that decision!  :o

Oh, wait - why not keep Hugh's volume pot and not spend anything!  :D

The problem with the ones listed is that no-one has compared them in an exhaustive shoot-out ... so it's a crap shoot as to whether they will actually make your GK-1 sound better.  With the TKD (yes, unfortunately the most expensive option!), we are taking advantage of Bob Crump's work in finding the best-sounding attenuator for his very expensive preamp.

Regards,

Andy

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #31 on: 19 May 2008, 10:53 pm »
Quote
Oh, wait - why not keep Hugh's volume pot and not spend anything!


No Andy  :nono:, I didn't want to hear such good advice though I suspect Hugh and my wife would agree.

The TDK is still $249 (US) in the current catalogue though with no 20KOhm option (10 though) so theoretically available but if you will forgive my ignorance, exactly why are the bypass resistors needed?

andyr

Re: GK-1 Stepped Attenuator
« Reply #32 on: 19 May 2008, 10:57 pm »
Quote

The TDK is still $249 (US) in the current catalogue though with no 20KOhm option (10 though) so theoretically available but if you will forgive my ignorance, exactly why are the bypass resistors needed?

Because Bob Crump told DSK that using them improved the sound, over a "bare" TDK.  :D

Regards,

Andy

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #33 on: 19 May 2008, 11:59 pm »
Hi Andy,

I got the ‘best sounding’ bit but my question as a non-engineer (and general ignoramus) was that I didn’t understand what needed to be bypassed.  Is the TDK not a good enough SA in its own right?  Would bypassing apply to other SAs?

curly joe

  • Jr. Member
  • Posts: 10
Re: GK-1 Stepped Attenuator
« Reply #34 on: 20 May 2008, 12:47 am »
Just to keep the stepped attenuator discussion on this thread.

I have researched as best I can, the bulk of the Stepped Attenuator options available to me.  The overall prices for good quality switches seem to range from about $150 to $250 landed in Oz  (TDK a bit more) so for convenience, perhaps the 20kOhm DACT at $195 sourced from an Oz distributor is reasonable.  I must admit that I agree with Hugh and Theo here, not cheap so I hope, well worth it.  Makes cap upgrades other than the Platinum seem a positive bargain.

My only remaining concern is that even with my relatively inefficient Vanderstein’s at moderate to high volume, I rarely have the original volume control pot turned beyond about 90deg from ‘off’ out of the approximate 280deg rotation available.  In fact, that’s only with the phono selected and it’s rarely beyond about 45deg with CD selected, such is the gain and grunt of the Soraya.  I’m just a bit concerned that after looking at the DACT specs, I’ll be in the courser 4db or more per stop attenuation area for common listening levels.  What do those who have fitted a DACT or other SA say?  Am I concerned over nothing or should I look at other options?



Hi LM,

In my system I only had Hughs  Alps pot at around the 9 o'clock position at my normal listening level. In other words hardly off the stop. With the DACT it's up around the 11 o'clock position. I seem to recall Hugh saying he'd changed the pot he supplied in the kit so yours might not be the same as mine though.

Cheers
CJ

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #35 on: 20 May 2008, 01:08 am »
Thanks CJ,

Yes, often mine is hardly off the stop (many of the latest compressed CDs) so that sounds promising.  I was hoping the finer steps would be in my normal listening range.  Cheers

andyr

Re: GK-1 Stepped Attenuator
« Reply #36 on: 20 May 2008, 02:21 am »
Hi Andy,

I got the ‘best sounding’ bit but my question as a non-engineer (and general ignoramus) was that I didn’t understand what needed to be bypassed.  Is the TDK not a good enough SA in its own right?  Would bypassing apply to other SAs?


Hi Laurie,

Bob C thought, yes, the TKD is an extremely good-sounding SA.  However, by playing around (as he certainly knew what he was doing!) he was able to make it sound better.  :D  I believe (DSK might be able to confirm?) that these bypass resistors act to almost take the attenuator out-of-circuit.  In which case, you might well ask ... why bother to use an expensive TKD attenuator!!??  :D

I would suspect that "the bypass trick" would make any other attenuator sound better ... but Bob found the TKD sounded the best out of the ones he tested.

By all means buy half a dozen SAs and experiment for 2 months each (as Bob did).  After all, there are probably some SAs available now which weren't around when Bob did his tests.  I didn't have the time to do this - so I went "Bob's route"!  :thumb:

Regards,

Andy

DSK

Re: GK-1 Stepped Attenuator
« Reply #37 on: 20 May 2008, 02:27 am »
Hi Andy,

I got the ‘best sounding’ bit but my question as a non-engineer (and general ignoramus) was that I didn’t understand what needed to be bypassed.  Is the TDK not a good enough SA in its own right?  Would bypassing apply to other SAs?


Hi Lyn,

The TKD is fine on its own (it likely would not have survived as a product at that price otherwise) but in his never ending quest for "the best" Bob tried every mod he could think of. Primarily, he found that these bypass resistors improved dynamics.

Yes, the bypass mod could also be applied to other 'series' type stepped attenuators too, but you would need to experiment with various resistors to see which sounded best (to you). Originally I considered using some Caddocks (not cheap but much cheaper than the S102's) but Bob had tried them on the TKD and felt they sounded "crap".


EDIT: For those not aware, CTC was the team of Curl/Thompson/Crump. In this team, Bob Crump was the "parts guy" who scoured the world for the best sounding parts for their cost no object designs. The TKD/S102 setup was the closest thing to a totally transparent attenuator he could find. Theory may suggest that a 'ladder' type attenuator should be more transparent than a 'series' type, but this is not what Bob's testing found. As AndyR said, the bypass resistors effectively "bypass" the resistors in the attenuator to a large degree, thus improving dynamics and transparency.



« Last Edit: 20 May 2008, 02:40 am by DSK »

LM

  • Jr. Member
  • Posts: 250
  • Lyn
Re: GK-1 Stepped Attenuator
« Reply #38 on: 20 May 2008, 03:52 am »
Thanks all, my previous lack of knowledge has been successfully redressed. :thumb:

MikeC

  • Jr. Member
  • Posts: 66
Re: GK-1 Stepped Attenuator
« Reply #39 on: 20 May 2008, 08:21 pm »
Regarding the Welborne attenuator.

I have one installed in my GK-1, and I can confirm that it does work. however, there is a subliminal feeling that if anything in the preamp is to be improved, this is it. It is a shunt attenuator, i.e. it shunts the signal through the IC to ground. The series resistor is a Vishay/Dale metal film of good quality. I haven't compared it directly to anything else, as the GK-1 was built with this from scratch. I previously ran a pre-amp with a passive line stake with a switched attenuator which was a significant improvement over a log-faked Sfernice cermet pot.

There are some idiosyncrasies with the operation, but these may have been sorted out with later revisions. I also couldn't get one channel to work initially and had to send it back to Welborne. I never got an explanation of why it didn't work, but it came back with an additional cap inexpertly soldered across two legs on one of the IC's; I had to resolder it as it had come loose in transit.

I have bought from Welborne several times, with very little hassle. However, support is cursory at best (the antithesis of Hugh) and several people on AA have reported non delivery of orders in recent times. This is something any potential purchaser needs to be aware of.

I have recently looked at the relay switched attenuator kits from Bent Audio and Twisted Pear as alternatives, but haven't progressed beyond this yet. They may be worth investigating as well as alternatives to the TKD and others, particularly if remote operation is required.

Regards

Mike