Jeb's Build

[Chris65]

Resistors come in all sorts of different sizes, even with the same power rating.

I don't recommend Mouser, you have to order a minimum amount to get free shipping. In the UK, you can use RS Components, free next day delivery whatever amount you order, you just need to create an account (very easy).
Here's a sample of resistors: http://uk.rs-online.com/web/c/passive-components/fixed-resistors/through-hole-fixed-resistors/?applied-dimensions=,4294466702,4294882859

As you can see, just a few pence each, much better than Maplin's price! They do often come in packs, so you have to order a pack of 10 for example, just to get one. Some others don't, like the Vishay RN55 or RN60 which are very good resistors & used by Bottlehead in some kits.

The heat shrink is a good idea, another alternative is teflon (PTFE) tubing slipped over the leads.

 

[Jeb Jeb]

Chris - RS components looks great! Thanks for the tip. 

 

[Paul Birkeland]

There is no apparent reason as to why the resistors are different sizes that are apparent to me.

One resistor is a mil-spec 1/2W and the other is a consumer grade 1/2W.

We find it safer to treat everything like a consumer grade resistor, just to avoid confusion.  In this particular implementation, I might pay a little more for a higher power resistor just to get beefier lead wires.

 

[adydula]

Yup one is a mil spec but both are rated at 1/2 watt power.
I agree getting resistors that are low noise and with larger diameter leads is nice in this application.

Alex

 

[Jeb Jeb]

Hello again guys!

Well 6 months on from finishing my Crack build, I've just started to begin the Speedball installation and am hoping for a bit of help and encouragement again!

I'm doing the main board and It's going OK (I think so far) but definitely finding soldering the PCB challenging because I've never done it before. At first I had trouble getting a nice concave solder joint or creating bridges between the transistor leads.  I've reheated or completely redone almost all of the joints to the best of my ability and wondered if you guys could just take a glance at it to see if I'm doing okay or anything looks suspicious? I'd prefer to get it right or get some pointers before proceeding with the others.

One thing I've found is that even if I get what seems like a nice concave joint on the the bottom of the board, when I flip it over I will sometimes get a little ball or blob on the top side.  I understand from reading around that this would perhaps be caused by too much heat and/or solder.  If nothing is bridged on the top side, is it okay to leave these or do they indicate a bad joint throughout that pad?

Here's a couple of pics of the bottom of the board and one of the top showing a little bit of solder balling on the transistor lead - on close inspection, nothing is bridged.  I have used a bit of cleaner to remove flux residue from the bottom of the PCB so its easier to see.

Any comments or pointers? Much appreciated!

James

 

[Doc B]

Those look just fine. The trick is to make sure the wire and the pad are both in contact with the iron tip, not just the wire.

 

[Jeb Jeb]

Nice-one, thank you for the tip Doc - I will proceed !

Cheers

James 

 

[Jeb Jeb]

Okay maybe I spoke too soon... so I think I have damaged or melted one of the pads on the board.

There was one joint on one of the small resistors where I just couldn't get the solder to stick to anything but the resistor lead.  I reheated and sucked up the solder to see what was going on and there doesn't seem to be a pad any more (see pic). Perhaps it lifted and I sucked it up?  Ugh...

At this point would I need to order a new board?

I'm sure I'll get there in the end! 

 

[Doc B]

Looks like there is just enough plated trace left directly under the lead to be able solder to. You can also take an xacto knife and carefully scrape off the green mask on the trace near where the pad was, to give you a little more surface to solder the end of the lead to.

 

[Jeb Jeb]

Okay Cool, sounds good. I'll give that a go tomorrow.  Thank you once again.

 

[adydula]

Hey Jeb!!

Congrats on working in the speedball upgrade.

Scraping the green stuff off a little to get more area of that trace to solder is a good idea, simple easy does it...

Cant wait to hear your comments about the upgrade!

Alex

 

[Jeb Jeb]

Cheers Alex!

I did just that - it was quite straightforward to expose a little area of the trace with a knife and it seems to have produced a good joint - from what I can tell at least!  I was disappointed to mess up the pad but it's also good to learn a new technique if such a problem arises and to know there are ways around things with PCB work.

I'm quite pressed for time to devote to it at the moment but have finished the main board. Aiming to finish the others and get it wired in next week. I'm probably the slowest bottlehead builder yet... 

One basic question for what's coming up in the manual - After assembly of the PCBs, when actually wiring the boards into the Crack circuit, the hook-up wire is passed through the holes from underneath the boards, so I presume that means you carefully solder the pads on the top of the boards this time- correct? But using the same technique, pass the wire through, then bend it flat to the board to keep it in place, and be extra careful not to melt any nearby components?

I do like the PCB work so far- it's different and does require an extra degree of care and precision with the iron - but definitely satisfying and looks very cool.  I'm sure it's pretty straightforward for you! 

Hope you're still enjoying your amp too!

 

[Chris65]

One basic question for what's coming up in the manual - After assembly of the PCBs, when actually wiring the boards into the Crack circuit, the hook-up wire is passed through the holes from underneath the boards, so I presume that means you carefully solder the pads on the top of the boards this time- correct? But using the same technique, pass the wire through, then bend it flat to the board to keep it in place, and be extra careful not to melt any nearby components?

Yes, that's correct, although don't bend it 'flat' to the board. The wire should pass through the pad, then just bend the exposed end slightly to make a good contact with the pad & it will stay in place for soldering.

 

[Jeb Jeb]

Thanks Chris - will do!

 

[adydula]

Jeb,

Yes thats pretty much it. Fairly easy to solder. If i remember following the wire lengths and being careful to attach the wires in the correct places is important. Check and work carefully.

I am still enjoying the amp. I have been busy and just completed another totally DIY amp, all solid state, came out nice. I will pm you a link to look at.

Alex

 

[Jeb Jeb]

Hi Guys,

Just a quick update:  I just finished the smaller boards and got everything wired in.  Tested well so just fired her up!  Of course I doubted myself at every step of the way..lol.. but so far so good and it sounds really EXCELLENT!

In terms of sound there are quite a few areas of improvements I'm noticing - but in the bigger picture I would liken it to something slightly blurry having been brought into much tighter focus.  I'm not sure if its because the staging has increased in width and depth or if it's just the greater resolution but the whole experience feels grander and more refined to me.  One other area I would mention especially is the bass, which is exhibiting improved depth and definition, which is particularly noticeable vs the stock sound that I've been used to for the last 6 months. 

The build was good fun and nicely challenging.  For a beginner I would say it is really spot-on in terms of the learning curve from the skills I learned from the stock build.  The manual/photos are excellent just as before.  My PCB soldering skills definitely improved by the time I got to the smaller boards and I had bettered my technique and developed a bit more confidence in what I was doing.  I suppose if I were doing it again I might have bought a blank practice board and got my eye in on that with some cheap components first before hitting the main board - but it didn't really matter in the end. 

Once again, a big thank you to everyone here for their help and to also everyone at Bottlehead HQ for doing what they do!

Cheers!

James

 

[adydula]

Hey Jeb!!

Congratulations on your upgrade and I am glad you like the sound. Its hard to tell the differences with all the variables involved. But technically its a better amp with the upgrade which should help.

It would be nice to have two identical amps side by side one with and one without to do a AB listening comparison.

To me it definitely did not hurt the sound quality at all. Its just different to me in a good way.
As you know I really like building stuff as well and cant resist upgrades and fiddling around with the stuff!

Been thinking of getting a fancy volume pot, stepped type to install....

Enjoy!
Alex

 

[Jeb Jeb]

Thanks Alex -

I agree - the tinkering is a lot of fun. I decided to strike while the iron was hot so I've also popped in a new pot (not stepped), power supply choke and film output caps in the last few days.  I also bypassed the last PS cap with a small 2.2uF film cap.  All challenging & a really great experience for me in terms of thinking outside of the manual a little bit.

To be honest I never really had any problem at all with the stock pot, but I do feel the better pot I have (TKD) is somehow a bit cleaner and less rough.  The TKD feels incredibly silky so the user experience is really nice, that's for certain.  Quite ridiculous when you think about the price in relation to the cost of the amp though of course.  I also padded the pot with the resistors, as you did a while ago, which is GREAT as I have much more usable range on the dial now.

Crack is addictive.

Definitely post an update if you go ahead with the stepped attenuator!