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Author Topic: Crack Upgrade Path?  (Read 62220 times)

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Offline tubeglow

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Re: Crack Upgrade Path?
« Reply #60 on: May 01, 2011, 10:55:44 AM »
I'm relatively new to the DIY stuff (I assembeled a PCB-based portable amp) so some of the lingo is pretty foreign to me. "Getter", "heater", and "cathode/anode" to name three. I've since done a little reading and now know what those things are, but when I read here about installing different potentiometers, do all stereo ones have the same connection points? Will a TKD, or ALPS, or PEC be soldered in the same as the stock one? Same for the headphone jack? From what I've seen, it seems Neutrik is easily the most popular but is it the only choice as an upgrade? Hope to get a "it's shipped" e-mail soon so I can get my hands on it and visualize some of these things.

Offline Grainger49

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Re: Crack Upgrade Path?
« Reply #61 on: May 01, 2011, 11:45:18 AM »
While you are waiting for the kit to arrive you should read this thread:

http://www.bottlehead.com/smf/index.php/topic,173.0.html

The first item is the meter you must have to verify your kit is put together properly.  It can be used to verify how a pot is wired.  The fact is that Alps often have 4 lugs per channel.  The placement of the input, ground and wiper lugs is not a standard thing so to be sure you should measure the pot to make the determination.

The same thing for different headphone jacks.  But they most often come with instructions that indicate the right, left and common leads.  Shoot, you will want to familiarize yourself with the meter anyway before starting on the kit.

Offline tubeglow

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Re: Crack Upgrade Path?
« Reply #62 on: May 01, 2011, 12:30:29 PM »
Thanks Grainger. I already have a nice Craftsman meter and have used it on other projects (interconnects, power cables, etc) so that isn't an issue and I've read the thread you linked me to. I have all the "necessary" tools, and many of the "nice to have tools" so I think I'm covered there (I hope so anyway).

I read about octal sockets, the various voltages for tubes, and different capacitors and it seems many folks here have a good deal of knowledge about electronics, or at least tubes, and how everything works together. I am ashamed to say I don't even know how to read a schematic. I know some of the symbols but that's about it.  Hopefully over the summer when I'm not in school I can get that taken care of.

Offline Grainger49

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Re: Crack Upgrade Path?
« Reply #63 on: May 01, 2011, 02:35:45 PM »
Somewhere I posted how to figure out how a pot should be wired.  I should save it in a file and cut and paste it when the subject comes up.

BTW, the Alps pots I am familiar with have a fourth lug, per channel, for adjusting the loudness compensation.  It isn't used for our applications here.
« Last Edit: May 02, 2011, 03:11:20 PM by Grainger49 »

Offline Billyk

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Re: Crack Upgrade Path?
« Reply #64 on: May 02, 2011, 02:59:47 PM »
I used a PEC pot as my pot upgrade and it wired in exactly the same as the stock one. I just needed to enlarge the hole a bit; oh and the shaft is a bit longer too so the knob does not set all the way dow.
Don't let the glasses fool ya, Stand beside me when you measure my size. Don't let false estimations overrule you, soon even you might come to realize. I've been a wizard since my childhood....

Offline sharpi31

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Re: Crack Upgrade Path?
« Reply #65 on: May 12, 2011, 11:21:30 PM »
I can heartily recommend these miniature stepped attenuators sold on Ebay:

http://cgi.ebay.co.uk/DACT-Type-21-Stepped-Attenuator-Potentiometer-100K-2A3-/120474000457?pt=LH_DefaultDomain_0&hash=item1c0ccf5c49

I've tried PEC & Alps pots, plus more expensive chunkier stepped attenuators, and now use these for every project. I can't hear any colouration and the signal path will be shorter than many larger attenuators (including ladder type).

No brainer!

Offline Laudanum

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Re: Crack Upgrade Path?
« Reply #66 on: May 13, 2011, 12:40:27 AM »
I saw those and they look to be pretty decent for the price.  I think one of the biggest things with stepped attenuators is the quality of the mechanical switch that they use and that makes sense.  But the same can be said for the quality of the cheaper potentiometers.   Then there is the fact that 21 or 24 steps is often said to not be enough, and depending on the source and the way the pots were built in terms of taper, especially not enough near the lowest end of the range (low volume/gets too loud too soon).  Ive been obsessing over the volume pot thing since I first decided to build the amp.  I was considering one of those pots or possible the Valab 24 step (series) attenuator.  But I have a feeling I would had to use resistors on signal inputs to tame the volume at the lowest settings.   I have a cheap wirewound alps in another amp and it tracks surprisingly well at the low end of the volume range and throughout and sounds fine but being a small board based amp, doesnt leave much room for mods for comparison.
I've prewired an Alps Blue Velvet pot for the Crack and may use it or I still may go ahead and use the stock alpha pot in the initial build and swap the Blue Velvet in later to see for myself if I really hear a difference.

I can obsess on end about little things and drive myself crazy eventhough I full well realize that I wont really know how anything behaves until it's up and running.  I probably didnt inspire much confidence in Tubeglow.  But I can offer this.  You arent alone, Tubeglow.  Well, I can generally follow the schematic but dont know what everything means/does.  But I do know, that after looking over the instructions, this is an easy build as long as you can solder.  Ive asked plenty of basic (some dumb) questions on this board in preperation for building the amp, and everyone has been helpful and friendly.  Im sure some were gritting their teeth with some of my questions but all patient and helpful nonetheless.  This is a safe place :-)
Desmond G.

Offline Grainger49

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Re: Crack Upgrade Path?
« Reply #67 on: May 13, 2011, 02:21:00 AM »
Laudanum,

Have you read this page from Bottlehead VoltSecond?  

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

He gives you a number of ways to set your volume range.  About 1/2 of the way down the page, look at figure 2.2.1, there are several options for trimming attenuators.  The one with a switch allows for having very small steps then at the flip of the switch you get full range.
« Last Edit: May 13, 2011, 02:29:43 AM by Grainger49 »

Offline Billyk

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Re: Crack Upgrade Path?
« Reply #68 on: May 13, 2011, 11:36:37 AM »
I have used the stepped attenuators from gigworks in several projects and am quite happy with them; I have a B1 and a little buffer/amp I built for my car. Somehow though the PEC carbon pot seemed more a appropriate choice for the crack. Just my 0.02!
Don't let the glasses fool ya, Stand beside me when you measure my size. Don't let false estimations overrule you, soon even you might come to realize. I've been a wizard since my childhood....

Offline Laudanum

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Re: Crack Upgrade Path?
« Reply #69 on: May 13, 2011, 12:37:22 PM »
Laudanum,

Have you read this page from Bottlehead VoltSecond?  

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

He gives you a number of ways to set your volume range.  About 1/2 of the way down the page, look at figure 2.2.1, there are several options for trimming attenuators.  The one with a switch allows for having very small steps then at the flip of the switch you get full range.

Ive seen the page but didnt get that far down.  Not sure I want to get that "fancy" with but I may down the road if needed. Thanks for the switch info, didnt even know it was there. 
To keep it simple, again, if needed (I dont even know yet)  I was looking at the Goldpoint site and the resistor values for L-pad attenuation that Paul helped me with.  I have the resistors if needed.  I figure, if it gets too loud right off the floor then I'd probably have more than enough max volume that I could afford some fixed attenuation.  But, I havent built it yet.  Painted the tranny bell end black. Just finished the cabinet this afternoon, poly is drying.  I was going to paint the chassis plate black but I decided to leave it as is with the brushed aluminum.  I think I like the contrast better with the black jacks, knob and tranny.  I needed to make a 3.5mm to RCA input cable and did that this afternoon.  Think Im going to make a shortish 1/4" male to 3.5mm female output cable (two pairs of headphones have 3.5mm plugs so I would need to use the adapters anyway).  Just been doing the prep stuff that I needed to do to get it all out of the way.

Thanks 
Desmond G.

Offline levlhed

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Re: Crack Upgrade Path?
« Reply #70 on: September 13, 2011, 05:37:52 AM »
Up from the depths....

I've been getting interested in upgrading the volume pot, got some good leads here.

I'm wondering if we shouldn't start a new thread dedicated to upgrade potentiometers/attenuators?

I'm trying to figure out that balance between something really good without going overboard that also is as close as possible to "drop-in" without serious mods....
Technics SL-1200 "MKE" ~> DL103r w/Ruby Cantilever & Contact Line Stylus ~> Audioquest PT-9 ~> Bobs Devices Cinemag SUT ~> Vista Audio PHOHO-1+ ACLE ~> Bottlehead Crack w. Speedball ~> Beyerdynamic T1

Offline Jim R.

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Re: Crack Upgrade Path?
« Reply #71 on: September 13, 2011, 06:01:19 AM »
In my experience, both the goldpoint and the PEC pots fit easily with just a bit of filing to open the mounting hole a tiny bit.  They both clear the inside of the box and other components too.

HTH,

Jim
Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline levlhed

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Re: Crack Upgrade Path?
« Reply #72 on: September 13, 2011, 06:28:18 AM »
Cool, thanks for the info.
Now, seeing the PEC for maybe $30 vs the Goldpoint (Mini-V?) for $150+ begs the question: Is the Goldpoint *really* that much better?
Technics SL-1200 "MKE" ~> DL103r w/Ruby Cantilever & Contact Line Stylus ~> Audioquest PT-9 ~> Bobs Devices Cinemag SUT ~> Vista Audio PHOHO-1+ ACLE ~> Bottlehead Crack w. Speedball ~> Beyerdynamic T1

Offline Jim R.

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Re: Crack Upgrade Path?
« Reply #73 on: September 13, 2011, 06:32:24 AM »
I haven't done any a/b comparisons, but I do believe the goldpoint is more transparent, but that said, the PEC is quite decent (I have one in my SE el84 amp), but I personally don't like stepped attenuators on headphone amps -- just not fine volume control.  Yes, it's the mini-v I was talking about.

-- Jim
Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline levlhed

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Re: Crack Upgrade Path?
« Reply #74 on: September 13, 2011, 06:44:00 AM »
I can see how a stepped atten could be annoying, I'm gonna go for a PEC.....
Technics SL-1200 "MKE" ~> DL103r w/Ruby Cantilever & Contact Line Stylus ~> Audioquest PT-9 ~> Bobs Devices Cinemag SUT ~> Vista Audio PHOHO-1+ ACLE ~> Bottlehead Crack w. Speedball ~> Beyerdynamic T1