Weekend Project Thread

[earwaxxer]

coming in late on this but I also have aspirations to read a schematic and build a kit from scratch! I find that very cool. I give credit to Bottlehead for the intro. Before that I didnt know a triode from pentode. I know it will probably happen at some stage, but for now, I'm a practical audiophile, and if it aint broken I'm not fixing it!

[Alonzo]

Jim, what's an X1 rating?  I looked up the data sheet for the cap I'm using and it states the cap is good up to 250v AC at 60Hz.  It's a Vishay MKP 1840.  Yes, I'm using the EXO-45 I got from you, they aren't broken in yet but will be soon.

While I was under checking the cap, swapped out the Sprague and changed out some resistors.  Trying to decide whether to connect the heater center taps to ground, if it'll make a difference in the hum.

Grainger, thanks for the link.  I ordered a bottlehead cord kit to try.

New pics...

[Grainger49]

Alonzo,

OOoooo  Lots of caps and iron.  Makes for a sweet sounding amp.

Do I see a FP 2 in the background, upper left, in the background of the second picture?

[Alonzo]

Grainger,
Good eye!! That Foreplay wasn't getting any use since I put Quickies in my system.  It is now the sacrificial lamb for an idea for a Foreplay with switchable inputs and outputs, I want something I can switch between my 3 sources and 3 amps and 3 sets of speakers plus a sub to each when needed.  I used the Foreplay chassis to get a copper top made, the base to house one of my Quickies.  So far that's as far as I've got, I keep thinking adding tubes to a switch box would be overkill since I already have preamps in the setup.  But I've got to do something with all the 12AU7's I have!!!!!

[Alonzo]

Hey Grainger,
What do you know about Grid chokes?  I did a search but the info was confusing, cycling between different amps, different values, etc. so I thought I'd ask.  Did you ever put grid chokes on your paramours?  If so where?  What kind of improvement did you get?
Thanks!!!

[johnsonad]

hmmm, I don't know Jim, I've used a 600v 2uF Auricap across the main of my Mac C22 with great sucess.  And it was the designer of the capacitor and engineer for Auricap that suggested it.  Years later there has been no problems.

Aaron

[Grainger49]

Alonzo,

I know only one thing about a grid choke.  It replaces a resistor from grid (or outer lead of grid stopper resistor) to ground.  I never put them in my Paramours.  It is pretty full already.  Take a look:

http://www.bottlehead.com/smf/index.php/topic,1185.0.html

I pretty much got nothing!

[Doc B.]

Grid chokes are a double edged sword. They can give a really great improvement in the sense of dynamics, but they are susceptible to hum pickup. So they don't work in every setup. I would suggest connecting them and rotating and otherwise moving them around for lowest noise pickup before committing to a location on the chassis.

[Alonzo]

Thanks Doc,
Is this a spot where higher value is better?  Mike's BCP-16's or equivalent?  I have some room to the front of my chassis, will long leads also pick up hum or is it a function of the windings in a magnetic field?

Grainger, that definitely is a blivit.  You do need a taller base, there's always more iron, bigger caps....

[Jim R.]

Sorry folks -- still in the midst of a sea of boxes, unpacking and dealing with a wrenched back on top of it all.

Here's a pretty basic primer on line rated caps that hits most of the high points:

http://www.justradios.com/safetytips.html

I hope that gives folks enough info to make a decision on whether they want to continue with their current caps or switch to something a bit more safe.  It's not that your typical poly film cap won't work across the line, it is a question of when and how it will fail -- especially those of you who live in places where electrical storms are frequent and intense, or nearer to power plants and large substations where large voltage spikes can happen.

Me, I'd just do it for peace of mind.

Thanks, and happy reading,

Jim

[Alonzo]

Thanks Jim, interesting read.  Even though I'm not the safest person in the world, I wouldn't want to start any fires.  I took a couple of pages of reading to find my caps weren't recommended for "across the line" applications, they really should put the safety information in the front.  Luckily Vishay makes other caps that will fit my situation.

[Jim R.]

Alonzo,

No problem -- it's just one of those things not many folks know or talk about but it is good practice especially for us diy types.

I will probably try this on whatever amp ends up at my bedside table as the only nearby electrical outlet also has hardwired into it, the two dimmable halogen reading lights my wife had installed on each side of the bed.  I have very little room to work with here so I'm going to have to come up with a very clever, compact outlet strip and filter setup for my headphone rig.  I've got some ideas but no shop in place to make it happen yet.

-- Jim

[earwaxxer]

Alonzo - count me as a grid choke fan! I have them in my Quickie now. Been back and forth between Paul's very well designed CCS and the chokes, and I think the chokes will stay in this time. I think it may because I listen to digital. If you are analog then the CCS may be 'cleaner' and better.

[2wo]

I have a pair of BCP-16's in my SR-45. I like them a lot in this amp. added a good bit of Dynamics...John

[Doc B.]

The chokes used in a Quickie would be plate chokes, not grid chokes.