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.
Crack Upgrade Path?
- Thread starter dumbo
- Start date
Grainger49
New member
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.
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.
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.
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.
Grainger49
New member
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.
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.
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!
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!
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
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
Grainger49
New member
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.
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.
Grainger49 said:
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
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....
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....
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
Noskipallwd
New member
I installed a Goldpoint 'Mini-V' in my Crack, but only because I had it around from a project I wasn't satisfied with and tore down for parts. I don't think I would have spent the $140 just for this amp. It does sound great, much better than the Alps blue I originally installed. I don't have any experience with the PEC so I can't compare the Goldpoint with it.
Shawn P.
Shawn P.
Alps Blue Velvet is similar in price to the PEC. I wonder who would win in a shootout? I ordered the PEC already, just wondering if I shouldn't have waited for more info.
Can you explain the output caps upgrade you did? What did you use? Did it require much shoe-horning or any serious modification?
Can you explain the output caps upgrade you did? What did you use? Did it require much shoe-horning or any serious modification?
Actually, the Alps Blue velvet pots can be had for a little less than 1/2 the price of the PEC from what I have seen. About 12 - 14 dollars at Mouser. Twice that through audio parts suppliers. I think they are great value for the money ... especially in terms of tracking at low volume but I think it sounds just fine. The PEC is supposed to be a nice pot and only in the 30 dollar range so not super expensive. I'll probably give one a try after a while just to see if I can hear a difference. If I had to pay $25 or so for the ALPS, I probably would have spend the extra 10 bucks on the PEC.
Outputs caps fit will depend on what caps you decide on. Something smaller, relatively speaking, like the Solen, Axon, Erse, Mundorf MKP etc. is actually a pretty easy fit. I went with the Mundorf MKP's. They sound nice in Crack, I think. I dont detect the "glare" that the Solens can sometimes impart. It's an upgrade from the stock electrolytics that isnt difficult to detect but the stock caps dont sound bad at all. The film caps are a bit smoother sounding and a bit more detailed and treble seems just a bit more extended as well. I know that one Bottlehead reported a little lighter bass from whatever film cap they used (may have been solen or axon). I havent noticed any less bass with the Mundorfs. I think it was definitely a worthwhile upgrade, eventhough the Mundorf mkps arent considered high end or boutique caps.
Outputs caps fit will depend on what caps you decide on. Something smaller, relatively speaking, like the Solen, Axon, Erse, Mundorf MKP etc. is actually a pretty easy fit. I went with the Mundorf MKP's. They sound nice in Crack, I think. I dont detect the "glare" that the Solens can sometimes impart. It's an upgrade from the stock electrolytics that isnt difficult to detect but the stock caps dont sound bad at all. The film caps are a bit smoother sounding and a bit more detailed and treble seems just a bit more extended as well. I know that one Bottlehead reported a little lighter bass from whatever film cap they used (may have been solen or axon). I havent noticed any less bass with the Mundorfs. I think it was definitely a worthwhile upgrade, eventhough the Mundorf mkps arent considered high end or boutique caps.
Just another opinion about output caps for the Crack: they do make a difference, but not as big of one as some may think. Tube rolling and the Speedball upgrade definitely changed the character of the amp; the 100uF Solens I put in there simply gave a bit of refinement. (I detect no glare in this particular application, FWIW). The stock electrolytics are surprisingly good, with solid bass and crisp (if somewhat "zingy") highs. The film caps sound smoother and less edgy in the treble, without losing detail. Bass seems to be about the same. I normally feel that output caps contribute a lot to an amp's sound, but the upgrade is surprisingly subtle in comparison to the plate loads and swapping out the 6AS7 for a 5998 (which IMO was the single biggest contributor to a change in sound quality). The only difficulty with the huge film caps is how to mount them securely. The small stock capacitors are much easier to deal with in that regard!
I also changed out the pot, and that made a small difference in clarity, in addition to better tracking/balance between channels. I used a cheapo stepped attenuator from Hong Kong, and it's holding up great so far.
I also changed out the pot, and that made a small difference in clarity, in addition to better tracking/balance between channels. I used a cheapo stepped attenuator from Hong Kong, and it's holding up great so far.
