Jeb's Build

[adydula]

Yes the caps will bend right over so the board can mount on the standoffs, they touch the bottom of the board somewhat but no issues there.

I had my crack running for a few weeks before I decided to do the speedball, the price was right and hey soldering is always fun to me! LOL.

I think the low bass notes, kick drums, bass and tympani are just so superb now....who knows....the idea behind a constant current source has its benefits, sonically oeprating in the linear range and power supply isolation should be a better all around technical scenario...it sure doesnt hurt the crack in anyway IMO. I dont think anything has gone negative at all.

Cosmetically it starts to get crowded inside...more stuff and wires!!

Enjoy your crack for awhile and then you will have a good comparison to the sound quality etc.

oh...no we stayed and watched the floor guys OMG it was noisy!! Its done!!

Alex

 

[Jeb Jeb]

Excellent!

I am awaiting a speedball kit & will enjoy the stock Crack in the meantime.  Pretty excited.  Excited about the bottlehead baseball cap I ordered too.  I heard it improves the soundstage - but that's unconfirmed 

Have fun with your new kit.

Jeb.

 

[adydula]

Thanks!

I have been swapping tubes in and out and having some fun with that, the tubes I got are really good to me, but I found several fairly inexpensive tubes to play within my budget...and most of them sound just as good!!

Let us know when your ready to Speedball!!

Alex

 

[Jeb Jeb]

Will do - I think it may be a little while before I receive my kit.  I totally agree about tubes - I've done a bit of rolling in other amps (12AU7s mainly) and although some of the *best* (whatever that means) tubes can command quite high prices,  inexpensive tubes that really deliver and offer great bang for buck have always given me the most satisfaction. 

One thing I'm finding with the Crack is how little I need to turn the volume knob to get to my ideal listening level - if 0 is at about 7 O'clock, I only need to go to just between 8 O'clock and 9 O'clock.  I'm using a player on my computer that fixes the volume sent to the DAC  (Rega DAC) and it seems to do this at max or near max (80%) - It was my understanding that this was the "correct" thing to do.  Are there any benefits/disadvantages to changing things so I can reduce the computer volume and so have the volume pot on the Crack in a more open position?  To be clear, despite not really having anything to play with with the volume pot - I don't have a problem with the sound I'm getting - i'm not hearing any imbalance and everything seems dead-quiet, but then I don't know any different at this point. 

I see in the Crack FAQ it suggest adding some 75K resistors for both the red and white wires where they enter the volume pot, and a 33K resistor between each of the outer lugs - but I just wondered what the benefits were to a more open volume position and if i'd just be trying to solve something that isn't a problem anyway.  I also see lots of people upgrade their volume pots.  I'm open to doing that but probably somewhat nervous to go "off-piste" from the manual at this point!


Jeb.

 

[adydula]

Ha...funny I just posted a new thread on this topic.

I had the same experience and added the voltage divider network of the two 75K/33K resisitors etc and it works well to allow more adjustment on the volume control...

With speedball I am back to noticing the volume is now at a lower mechanical postion 9 o'clock or there abouts..

So I think the gain with the speedball might have increased, I think that PB or Doc will respond with a change in the resistor values...I would be afraid to add these etc....no real issue that I can see..maybe some "johnson noise" added etc...

I agree on the price of tubes, some are absolutely out of this world....its more important to me to know the circuitry and what effect it has on the audio signal and circuits have more of a pronounced affect of things than changing tubes to me.

I have 7 power tubes and they all work well, spend too much time rolling to find that thing that eludes us!!! LOL. I have my wife change tubes on me and not tell me whats installed and I have tried to pick one over the other!!! I could not!!!

Time for more coffee and just enjoy the music!!

Alex

 

[Jeb Jeb]

Great - yes enjoy!

I'll wait and see what recommendation you are given and maybe I can skip straight to that solution at the same time that I install the Speedball. 

 

[Grainger49]

Jeb, your volume control action is Crack FAQ #3.  Check the sticky.  I prefer to use a greater range on the volume control as it allows me to set a more precise volume level.

 

[Jeb Jeb]

Thank you Grainger - that makes sense and it sounds good to me to have more range.  I'll look into getting those resistors.  I've been looking on the forums but I guess I do have a quick questions:

- I'm not sure I will but If I did fancy replacing the volume pot while I'm at it does a pot with a different impedance effect the resistors needed as per Crack FAQ 3 ?


Thank you in advance.  Really enjoying the Crack and the hd650 clamping force is indeed letting-up with use! 

Jeb.

 

[JamieMcC]

I went down the resistor route with my Crack and it works well. A little later on I decided to try fitting a stepped attenuator (100k valab ladder type) after a little use the range seemed greater and decided I didn't need the resistors any more and later removed them. They are easy to fit and try and just as quick and easy to remove.

 

[adydula]

Hi Jamie...

I got a reply from PB to add 33K's in parallel with the 33Ks already installed.

I listened for several hours yesterday and for some reason it seems back to ok for me??? Strange...

I know source material hasa a replay gain factor and if I listen to stuff with a lower or positve replay gain I have more than enough volume control rotation...as the gain goes high in the negative direction I dont have to turn up the volume much like not past 9oclock...

So maybe after this I will just leave it as is for a few weeks and listen and then decide to leave it as is, add or pull out what I already have.

Alex

 

[Jeb Jeb]

Cool - Jamie, Alex -  i'll look to adding some of those resistors at the same time as speed ball and maybe a different volume pot down the line! 

Since I'm so new to this going to keep it stock + speedball first and make sure I can get all of that working first as suggested.

But...having said that I do like to plan ahead so if I did want to try cap upgrades down the line will I curse myself later on if I don't think about it now  by figuring out some mounting options + holes and putting the stock output capacitors on fly leads to make it easier for myself later, or is it all easily do-able later on?  It looks like some of those terminals might be difficult to get to post speedball. 

Also Jamie - would you have any personal recommendations for caps that are not overly big, easy to fit, available in the UK and you feel offer a nice improvement?.  I don't mind spending a bit - I think the Crack will take pride of place for the foreseeable!

 

[JamieMcC]

Cool - Jamie, Alex -  i'll look to adding some of those resistors at the same time as speed ball and maybe a different volume pot down the line! 

Since I'm so new to this going to keep it stock + speedball first and make sure I can get all of that working first as suggested.

But...having said that I do like to plan ahead so if I did want to try cap upgrades down the line will I curse myself later on if I don't think about it now  by figuring out some mounting options + holes and putting the stock output capacitors on fly leads to make it easier for myself later, or is it all easily do-able later on?  It looks like some of those terminals might be difficult to get to post speedball. 

Also Jamie - would you have any personal recommendations for caps that are not overly big, easy to fit, available in the UK and you feel offer a nice improvement?.  I don't mind spending a bit - I think the Crack will take pride of place for the foreseeable!

PMed you

 

[Jeb Jeb]

Hi guys - bear with me - need to ask a couple of real noob questions about doing the Crack FAQ No.3 resistance modification:

1) never bought resistors before , so many types, prices etc -  just these ones will be okay and consistent with the quality of everything else? - http://www.maplin.co.uk/p/metal-film-06w-33k-ohm-resistor-m33k

2) so looking at the sketch of the pot I attached I understand I attach 1 x 75k resistor between the red wire and pot lug A  and  1 x 75k resistor between the white wire and pot lug B.  But I'm confused about which lugs the 33k resistors go between? One between lugs A and E,  one between lugs B and F ?


Sorry this is probably quite lame but I guess I'm not very good without pictures.  :-\  Thanks! 

Jeb

 

[Chris65]

Those resistors are fine (if a bit expensive, normally you can get them for very little).

Not sure which way you've drawn the pot, but if that's looking at it from the RCA jack side, then yes that's correct.

Just to confirm: the 75k resistors go between the wires that come from the RCA jacks & go to the outer lugs of the volume pot: one for red, one for white. You can add these at the RCA jack end or at the volume pot end.

The 33k resistors go between the outer lugs of the volume (not the centre lugs), top & bottom. That is, the lugs where the red & white wires from the RCA jacks connect & ground, the 2 lugs with the black wires attached (closest to the 12AU7).

 

[Grainger49]

I'm not sure I got the Mouser UK site, although I clicked on that link.  Here is my search.  I believe you have the right type and power rating (very low) you need.

http://www.mouser.com/Passive-Components/Resistors/Film-Resistors/_/N-7gz3w?P=1yzekiaZ1z0z819Z1yzaok0

 

[Jeb Jeb]

Thanks Chris - I should have just used a photo! I have attached one to this message just to be a bit clearer but I think I have understood you correctly. 

1 x 75K between Red RCA wire and A
1 X 75K between White RCA wire and B

1 x 33k between A & E 
1 x 33k between B and F.


when I first read the FAQ somehow I got confused.  I am still learning my way as to the "why" of everything. 

May I ask in very basic terms why it is necessary to have these 33K resistors going to ground as well as the 75k ones on the red and white cables?


PS. Grainger thanks for info about resistors I'll grab a few.  When I first did an online search some exotic ones were going for 4 or £5 each or more...  Some metal film, some carbon.  I guess these are "audiophile" resistors? the descriptions often talked about them having a certain "sound" be it warm or transparent or "dry".  I guess things like this are considered pretty dubious or else just not critical in this application.

 

[adydula]

Jeb......I asked the same question in another thread here are the resistors I used...very cheap and metal film from www.mouser.com

http://bottlehead.com/smf/index.php?topic=8151.0

Mouser #: 71-RL20S-G-33K
Mfr. #: RL20S333GB14
Desc.: Metal Film Resistors - Through Hole1/2watt 33Kohms 2%
2 $0.32 $0.64


Mouser #: 594-SFR16S0007502FR5
Mfr. #: SFR16S0007502FR500
Desc.: Metal Film Resistors - Through Hole1/2watt 75Kohms 1%

Here is a pix of them before I cleaned them up to test:

Alex

 

[Jeb Jeb]

Cheers - thanks for the thread link -  I didn't realise all this had already happened in a parallel universe...  I need to be better with the search function!  in your pic Is there a reason why the resistors going across the middles are much bigger than the other ones even though they are 33k and the others are 75k ?

Alex You build looks nice and shiny and clean!!!... and with the speedball just tempting coming into view in the corner!

It's great to see a picture, it really helps - that's why the bottlehead manual is so good I think.  While I wait for things to arrive I was watching some vids on soldering and I was wondering about what is the accepted method of joining a resistor to a piece of wire  - from your pic it looks like you create a loop or hook on the wire end and then you can wrap the resistor lead around it as if it were a terminal, then just join to the volume terminal as normal.

the heatshrink suggested on your thread is a good idea too - I will get some.

 

[adydula]

Hi Jeb...

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

That said, both are rated at 1/2 watt more than whats needed and I chose tolerances of 1% and 2%, I couldnt find both at the same tolerance.
This may be why they are different physical sizes.

You can tack solder them on the pot terminals or try to wrap them around the terminals and solder but the joint is getting large here...

I have no issues with "tack" soldering if done well....there isnt any movement or strain on them.

One side of the pot outer terminals are already joined together so you could twist the 33ks together and solder to the inner most top terminal then each of the other leads of them
to the top and bottom outer pot terminal.

I elected to put the smaller 75 K resistors near the pot and away from the RCA jacks...read somewhere that this was the preferred method.

To neaten it up you can use heatshrink, solder the leads inline with the wire and attach and solder to a terminal and then slide the heatshrink over once cooled and shrink to make a
nice neat installation.

If u do use heatshrink, remember to put it on before you solder!!! LOL done that before....

I have done a lot of listening.....my wife thinks way too much!! Ha!!

The speedball kit makes things just a little nicer...

I dont think I am going to add the other resistors now as PB indicated I think that most of what I listen to is allowing me to go from 9 o'clock to 1 o'clock with plenty of enough
drive and volume...

So we are now a happy camper!!

Alex

 

[Jeb Jeb]

A happy camper, pleased to hear it!  Those are great and welcome soldering tips, as ever, thank you. 

I know what you mean about logging some serious listening time.  It's like I heard Doc say, it really does sound better when you build it yourself!