Stock Crack vs. Modded Crack

[ALL212]

I picked up Crack #2 during the recent sale and now have a 100% stock Crack to compare to my modded Crack.  The modded Crack was my 1st BH kit and this new one is kit #7 so I've had some experience working under the hood and my wiring is much nicer.  Senn HD650's are used for listening tests.

Modded crack changes:
Wiring - I like cloth wrapped solid core.  Only on and directly around the transformer did I use original wire.
Attenuator is an Alps Blue
Input RCA's are Vampire
Input wiring from RCA's to attenuator is Cardas 2x24
2 of the PS caps are Rubicons, 1 is Nichicon
Last cap (Nichcon) is tipped with a 1uf Clarity PX cap
230 ohm resistor is replaced with C-7x choke
PS diodes replaced with Cree Shotkey diodes (not pictured)
Output caps are Clarity Cap PX
Speedball is installed
5998 tube in place of the 6080
5963 Rca long black plate in the 12AU7 spot


Stock:


I'm hoping to put the o'scope to these and see if I can spot waveform (AC and output) differences.  Most immediate apparent difference is bass.  The stock unit is very nice to listen to but the bass just jumps out at you on the modded one.

 

[grausch]

I am very interested to see how they will measure on the o'scope. Would also be very interested to see how both measure with the same tubes, i.e. 6080 and 12AU7 in both.

Once I get some time, I plan to spend some time listening to my Crack to get used to the sound signature again. Once that is done, I plan to start upgrading quite a few parts (err..more than quite a few actually). It would be great to see actual evidence that these do positively impact the performance of the amp.

Cheers,

Gunter

 

[Doc B]

atomicbob has some measurements with different output caps in the Crack thread over on Head Fi.

https://www.head-fi.org/t/476650/crack-bottlehead-otl/6795#post_11509819

I will add my usual comment that there is a law of diminishing returns on the addition of boutique parts. It would be wiser to spend $1200 on an amp kit with a more refined circuit design like Mainline than $1200 on gigantic caps from Ukrainian missile cruisers, spider silk insulated wire that has been passed over the thighs of 14 year old virgins and unobtainable tubes of questionable background for a Crack. However I also support the notion of one doing the experiments for their own edification. I waste money on stuff that doesn't improve things as much as the cost would imply as much as the next guy, though not so much in my audio gear these days as my other hobbies. My suggestion is to keep the spirit of the Crack in mind and make sure the mods you do are great bang for the buck.

 

[grausch]

Hi DocB,

Thank you for the link - do you think I should install some 470uf Rubycon caps in my Crack?  Even though I am kidding, part of me is seriously considering it.

Point taken on the diminishing returns and I agree with you on the Mainline. I should note that I really don't expect that much of an audible difference and I am usually quite sceptical that any upgrades will make much of a change in sound. However, as an electronics noob, I have learnt a great deal tinkering on the Crack and planning & researching future upgrades. My dad sure as hell never suspected that I would one day explain to him how a rectifier bridge works! I also have to note that the more I modify my Crack, the more I start to appreciate the original design. Everything is much better thought out than I originally suspected and to my ears the stock Crack sounded fantastic.

Still looking forward to see the results of the o'scope though...

 

[Natural Sound]

gigantic caps from Ukrainian missile cruisers, spider silk insulated wire that has been passed over the thighs of 14 year old virgins

You owe me a keyboard.  ;D

 

[Alonzo]

For a lot of us it's all about the chase.  Actually doing hands on work is part of the fun and once the build is done you want to do more.  Also it's easier to pay for a upgrade here and there than to kill the beer budget for a large purchase.  Having a scope does well to track changes, some of the upgrades I've done really didn't show audible improvements (to me) but it's become a fun hobby (cough "obsession" cough).

 

[Paul Birkeland]

Thank you for the link - do you think I should install some 470uf Rubycon caps in my Crack?  Even though I am kidding, part of me is seriously considering it.

There are some operational/safety concerns with putting more than 100uF per channel of coupling capacitors into the Crack, therefore we don't recommend it. 

 

[grausch]

PB,

Thanks for the warning. I was considering them in the PS as per this thread (http://bottlehead.com/smf/index.php?topic=7950.0) and not as output caps.

 

[ALL212]

I will add my usual comment that there is a law of diminishing returns on the addition of boutique parts. It would be wiser to spend $1200 on an amp kit with a more refined circuit design like Mainline than $1200 on gigantic caps from Ukrainian missile cruisers, spider silk insulated wire that has been passed over the thighs of 14 year old virgins and unobtainable tubes of questionable background for a Crack. However I also support the notion of one doing the experiments for their own edification. I waste money on stuff that doesn't improve things as much as the cost would imply as much as the next guy, though not so much in my audio gear these days as my other hobbies. My suggestion is to keep the spirit of the Crack in mind and make sure the mods you do are great bang for the buck.

I find it much easier on my mental circuits and current budget to blow up my Crack and have to repair it than blow up a Mainline whilst playing with updates and wonder "how much to fix this"?  As far as wisdom goes...discuss that with my wife, she has made observations over the years that may put any wisdom I might think I have in serious question. 

I've built some kits and the directions are fantastic but I find myself wondering at the end of the build why does all this work.  If I piece out a bit of it (power supply) I can work my way back into the circuit and have some understanding of what goes on in there as I do updates and mods. This power supply filtering is a great learning experience for me.

I also would want to buy a pair of expensive headphones to match the Mainline.  I would always wonder if my HD650's would sound as good as HD800's so my budget feels safer at the Crack + updates level.

Might I also start a new thread with a "Doc Says" title and put your requirements for a good upgrade in there?
Doc says, "...gigantic caps from Ukrainian missile cruisers, spider silk insulated wire that has been passed over the thighs of 14 year old virgins and unobtainable tubes of questionable background..." would be a great upgrade to your Bottlehead Crack kits. 
OK...maybe a bit out of context...  :

 

[Doc B]

Well I could probably be making a lot more money if I just put my scruples in the cabinet in the lab. Maybe our next product will be the audiophile grade clip leads we have been talking about for years. I have also wanted to make paper and wax capacitors with ear wax from mastering engineers. And I lose the argument to make a tube powered solder station every design meeting.

Maybe instead we will start a service of replacing the vacuum in your vacuum tubes with fresh vacuum every year. I've got bottles full of the stuff in my basement, some of it rare vintages. We could maybe even do transplants, like put 300B vacuum in EL34s.

"I started out with nothin', and I still got most of it left" -Seasick Steve​

 

[ZacharyP]

Maybe instead we will start a service of replacing the vacuum in your vacuum tubes with fresh vacuum every year. I've got bottles full of the stuff in my basement, some of it rare vintages. We could maybe even do transplants, like put 300B vacuum in EL34s.

"I started out with nothin', and I still got most of it left" -Seasick Steve​

Best post all year

First bottlehead to build a tube powered soldering station wins...Doc's heart?

 

[Strikkflypilot]

Wouldn't recommend ear wax, Doc.
It's full of hair and epithelial surface cells.
Of course, there might be genres that would profit from it

 

[Alonzo]

Or a Jacob's Ladder power indicator, would put those wimpy vintage lights to shame...

 

[ALL212]

And I lose the argument to make a tube powered solder station every design meeting.

Maybe instead we will start a service of replacing the vacuum in your vacuum tubes with fresh vacuum every year. I've got bottles full of the stuff in my basement, some of it rare vintages. We could maybe even do transplants, like put 300B vacuum in EL34s.

"I started out with nothin', and I still got most of it left" -Seasick Steve​

Not embarrassed or shy to say that I would pony up for a vacuum tube solder station right now!  As long as I could upgrade the caps in it...

Vacuum tube vacuum replacement....I like that!  ;D ;D ;D

 

[SCompRacer]

I'd be interested in a warmer summer sounding vacuum instead of a cold winter sounding vacuum.

Nice Crack builds Aaron!

 

[Paul Birkeland]

First bottlehead to build a tube powered soldering station wins...Doc's heart?

If you could build an all-tube soldering station with tube based temperature control, I'm quite confident that Doc B. would come up with some kind of ridiculous award.

 

[2wo]

He threw that some years ago, don't think anyone bit...John

 

[Doc B]

Actually one guy did. I think we worked out that the thyratron chosen might have been a little underpowered. Plus the guys all thought the thyratron control was useless without temp sensing and nobody wanted to work out that part of it.

This would be similar to my talking to John Swenson about an all tube DAC many years ago. Not tubes tacked onto a DAC chip, a real honest tube demux with tube flip flops running into a resistor ladder. John kinda won the argument against when we calculated something like 50 amps required just for all of the tube heaters and a full size equipment rack or two to hold all the parts.

 

[ALL212]

Request for guidance:

I've got a Hitachi V222 20Mhz o'scope.  I think what I'm looking for is possible differences in post power supply noise of the stock vs. modified Crack and then also any noise or "disturbances in the force" at the headphone outputs (I've no clue what to expect - maybe nothing...).  I plan to use an app on my iPhone to generate wave forms to look at on the output.

What spots should I be poking the lead of the o'scope into to find such fun stuff.  The output is obvious - I can handle that one  :! 

I think: 
1)  The 270k resistor in the PS as one spot.
2)  Heaters come straight from the transformer so I wouldn't expect differences here.
3)  At the headphone outputs.

Should power supply checks be done with a load or should that be part of my experience here?  I can rig a resistor across the headphone jack to simulate that.

Any other places?

 

[Paul Birkeland]

I think what I'm looking for is possible differences in post power supply noise of the stock vs. modified Crack

A lot of multimeters will measure AC voltage in the presence of DC, so you may not need the scope for that.  Otherwise, you could measure across the 270K resistor.

Should power supply checks be done with a load or should that be part of my experience here?  I can rig a resistor across the rca terminals to simulate that.

You can do it with both, but I wouldn't expect too much difference at the power supply with loads.  Since the headphone jack is the output, that is where you'll want to apply your loads.