My Crack Build

L

lior.amsalem

New member
Hi all,
Ordered my kit yesterday and I'll keep this post updated with my progress and stuff.
This kit build will be my first serious one (beside some PCBs kits). It's also my first serious lesson into electronics of audio tube amps.

I will also try to add comments and question I encounter to help any new DIY down the road.

I little on my setup:
Mac mini -> AIFF/Apple Loseless -> iTunes -> BitPerfect -> Belkin PRO USB -> HRT MSII -> two of those nice male to male RCA adapters -> currently Harman Kardon HK3250 -> 650 cable -> HD600 HP

I'll be dividing my build into 3:
1. Crack kit alone with wood and plate work. I'll listen to the stock Crack for a week or so.
2. Speedball upgrade, probably a week of listening.
3. Other upgrade.

I already stocking up with parts and update as they arrive and picture all, trying to find the best parts for the money.
Upgrades I'll be doing, except SB:
1. Axon 91uF output caps.
2. ALPS blue velvet 100K pot.
3. Neutrik/Connex RCA jacks.
4. Neutrik locking jack.
5. Cloth wires (20ga)
6. Belton tube sockets.
7. Some tubes for rolling.

 
Do a forum search on "stepped attenuator" or just "attenuator."  There are many out there that folks like.

Of course Bottlehead sells the Sweetest Whispers, 11 steps and easy to build.  (I can't find them on the parts page or the general Products page."
 
Hi Grainger49,
I'm not looking for stepped attenuator, too expensive. Just looking for maybe a better potentiometer like the ALPS.
 
lior.amsalem said:
Hi Grainger49,
I'm not looking for stepped attenuator, too expensive. Just looking for maybe a better potentiometer like the ALPS.
Click to expand...

The Alps blue tracks very well at low volumes.  I also think they sound perfectly fine.  They are available for 15 bucks (usa anyway) give or take if you can find them at electronics suppliers.  Audio specialty dealers want more for them, in the $25 range.  At $15 or even $25 they are a good potentiometer IMO.  The only downside is that the have PCB pins which make it a little trickier to solder wires to but not a big deal at all, really.  Probably best to stick with 100K .
 
Lior,

As Desmond said, stick with a 100k pot, and personally, I try to avoid stepped attenuators on headphone amps as they always seem to have stops that are a bit too low or too high for where I want to listen, but others love them, so YMMV.

The Cardas Quad is a fantastic, easy to use solder, so go for it!

Looking forward to hearing about your progress, and especially what you think once you hear it.

-- Jim
 
Here is what the Foreplay and the Paramount manuals say:

"Solder - we recommend standard 60/40 or 63/37 tin/lead solder as the easiest to work with. 2% silver solder is OK, but stay away from 4% silver solder. It does not flow well. If you are using an adjustable solder station you will want to set the temperature to about 650-700 degrees."

Cardas Quad Eutectic solder contains around 4% silver.

In my experience, it is great for point-to-point wiring (metal to metal), but not for connexions on printed circuit boards (PCBs) as it does not flow well especially in smaller holes, even with more heat, with possible cold joints as a result. This is what I have, and I recently bought some 60/40 solder for work on PCBs.

The thing I like better with Cardas' is that the solder is a smaller gage, so handling is more precise.

If I had to start over again, I would not use Cardas Quad Eutectic. I had bought it before I received my kits and manuals, so I used it anyway. Others may like it. YMMV.

Richard
 
I have used these and they are excellent!  Many knobs will fit on the smooth shaft even if it isn't perfect because of the set screw.  I'd consider these easier to work with.
 
Hi there guys,
Few more questions.
As for the output caps what's your recommendations, looking for one under 20$ each?
Saw the Axon 91uF 250v for 15$ each, anyone uses it?

As for the headphone jack, looked at the Neutrik locking one.
There are two types:
NJ3FP6C-B: Locking 1/4" phone jack, D-size shell, black metal housing and gold contacts.
NJ3FP6P-BAG: Locking 1/4" phone jack, D-size shell, black plastic housing and silver contacts.
So, it there any relevance to the metal VS plastic housing in term of insulation from the aluminum plate?
Another Q, I remember to came across a post recommending not to keep the HP plugged while powering up, anyone can clarify? if so, I guess a locking jack will just make life harder for "replug" each time.
 
The only thing I can help with is keeping the HP plugged in.  When the amp starts up the output caps have to charge before blocking DC.  Not much DC leaks through and the resistor at the output jack sends it to ground. 

But if you have your headphones plugged in they take the DC directly across the drivers.  Doc is just being safe.  It might not hurt the drivers but it could.  So the safest thing is to unplug them. 

The same thing goes with a full Bottlehead system.  We turn on our preamps first, wait a few seconds for the DC pop to go away and then turn on the amps.
 
There is atleast one member here using the Axon 91uF caps.  Do a search, it should come up.  The Solens can be found for not a whole lot more in 100uF but you probably wont hear much difference between 91uF and 100uF.  Also, there is some debate as to whether the Solens and Axons sound the same.  I would think that in the least, very similiar.  I think it has been established that Solen makes the Axons.  Erse is another possibility for a low cost 100uF film cap.  The standard Mundorf MKP's are a little bit more expensive but still affordable.  I believe that Dayton also has a 100uf close in cost to the Axons, or atleast less money than the Solens.  I think Bennic makes the Daytons.  Ive used much smaller value Daytons in crossover networks.  They arent bad.  Im using the Mundorfs as are atleast a couple other members.  I like them. 
 
Hi Desmond,
Thanks, I guess that due to the prices and my will to make this build as cheap as I can while still upgrade whatever I can. I'll go with the Axon 91uF caps.

Anyone has got a good recommendation for cheap first tubes? (don't want to buy something expensive, just want to have another tubes while building to avoid bad tube problems)
Looking for one power and one input tubes, saw some in the tube rolling thread but I want to know which one is cheap and great :)
What I'm looking for is a match between the power and input that maybe someone can recommend, but on the cheap side.

Found at home some Kester 63/37 solder I'll probably use.
Still waiting for some info regrading the Neutrik locking housing...
P.S. I've updated the main thread with some more info...
Regards,
LA
 
I like the RCA 6AS7 (ST shape) and they are often inexpensive on ebay.  I've picked them up for under $15 (and even one or two under $10).  Of course you take your chances on that site but Ive had good luck buying from sellers with perfect or near perfect feedback. 
 
Despite fair warning, I used WBT solder (4% silver). This was my first kit but I found it fine to work with and was a good match for the wiring I chose...which was harder to work with than the solder for sure.
 
jrihs said:
Despite fair warning, I used WBT solder (4% silver). This was my first kit but I found it fine to work with and was a good match for the wiring I chose...which was harder to work with than the solder for sure.
Click to expand...

If your soldering iron heats quickly and you don't leave it on the joint too long, I count to three so everything is the same temperature, and remove the iron, you are fine.  Somewhere in this thread Richard says the solder I have been using for the last few years, 4% silver.  I didn't know.  But I'm pretty experienced with soldering.  Poster Paully, Paul H, comes over for a build about once a year and he uses it without any problems.  But I have seen some solder from Radio Shack that was horribly hard to melt that is 4% silver.
 
Few more details on the build :)
Wood color will be Wenge, to match my home office furnitures.
the plate will probably be matte grey.

Placed orders for all the upgrades I wanted: RCAs, POT, HP Jack, Axon 91uF caps, ...
 
Hi all,
Next topic, wires.
Well, I really wanna go with vintage cloth wires (mainly for that vintage look I love) but hope it's the correct decision sound wise...
Can anyone help with the current wire gauge?
What length supplied in each color in the kit? Any benefits of going with lower gauge wires for the filaments?

Regards,
LA
 
It's solid core and Im pretty sure that it's all 20 AWG.  It was atleast in mine.  The wire included with speedball was teflon insulated and I think 22 awg.  Im sure others will correct me if im wrong.  Cant help with the total length or the filament wire gauge question.
 
The heaters would be fine with a 24 AWG shielded.  The current is low and using a shield would keep the noise even lower than a stock build. 

Sorry I can't help with what wire is supplied with the current Crack kit.
 
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