Decade box

[p2pAmps]

Do you guys ever use a decade box for either resistance or capacitance when tuning an amp?  If so which one do you like?

[eleventeen]

I myself don't use them, but if I had one, I would. This is only because I am remarkably insensitive to the holy grail tone.


It's absolutely the the thing to have if you wish to futz with values. What kind? Makes no difference, really, it's just a rotary switch in a little box with 2 binding posts. Heathkit made them, EICO made them. General Radio (GR) also made them, far more rugged and usually more expensive. You want this kind of thing because you are trying out the sound with a .022 and want to change to a .05 and to make the good comparison, you don't want to unhitch yourself from your guitar, put it down, turn off the amp, unsolder or unclip test leads, reclip, turn power back on, pick up guitar. By the time you've done that your memory fades. Plus you want to go back & forth a few times. You can make one or more yourself if you want, of course. They are on ebay all the time but they seldom go for much less than $20-$25. People buy 'em.


To distinguish & clarify a bit: It is not so much a "decade" box, more useful would possibly be a "substitution" box. You are not going to hear much difference between a .001 and a .002 and a .003 uf unless your ears are true precision instruments.

[Willabe]

Do you guys ever use a decade box for either resistance or capacitance when tuning an amp?  If so which one do you like?

Our friend Ed C. does all the time, he likes them a lot for tweaking amps.

IIRC he makes his own. 

[p2pAmps]

Do you guys ever use a decade box for either resistance or capacitance when tuning an amp?  If so which one do you like?

Our friend Ed C. does all the time, he likes them a lot for tweaking amps.

IIRC he makes his own. 

I thought about making one but I can but one for less that the parts cost really

[tubenit]

Yes,  I have a decade boxes that I use to help design and tweak amps.  HotBluePlates gave them to me.

Since I have never built a single clone of a manufactured amp, they have been very useful to me trying out stuff.

With respect, Tubenit

[p2pAmps]

Yes,  I have a decade boxes that I use to help design and tweak amps.  HotBluePlates gave them to me.

With respect, Tubenit

So would I need one that would handle 630v like the coupling caps I might test?

[SILVERGUN]

Yes,  I have a decade boxes that I use to help design and tweak amps.  HotBluePlates gave them to me.

With respect, Tubenit

So would I need one that would handle 630v like the coupling caps I might test?

Yes
 
Here's what I did...it has come in handy on a number of occasions.
I made it a combined box and made some of the switch settings useable for low voltage cathode bypass caps...but I also made them on a separate rail so I would never make the mistake of inserting a low voltage cap into a high voltage test spot.
I have to move my test lead over to do the low volt test.
 
Plastic box from Radio Shack, switches from Newark, boards from AES
 

[p2pAmps]

Yes,  I have a decade boxes that I use to help design and tweak amps.  HotBluePlates gave them to me.

With respect, Tubenit

So would I need one that would handle 630v like the coupling caps I might test?

Yes
 
Here's what I did...it has come in handy on a number of occasions.
I made it a combined box and made some of the switch settings useable for low voltage cathode bypass caps...but I also made them on a separate rail so I would never make the mistake of inserting a low voltage cap into a high voltage test spot.
I have to move my test lead over to do the low volt test.
 
Plastic box from Radio Shack, switches from Newark, boards from AES

That looks great...  Thanks.  I think I will make one

[SILVERGUN]

That looks great...  Thanks.  I think I will make one

Ok...just don't embarrass me toooo bad..
 
I've seen your work.

[p2pAmps]

That looks great...  Thanks.  I think I will make one

Ok...just don't embarrass me toooo bad..
 
I've seen your work.

Ha!

[Fresh_Start]

Mike - the rotary switches in a true decade box would cost you much more than an eBay score. I bought one for resistors and one for caps. Had to replace a fair number of the resistors since the old ones had drifted a LOT, but still cheaper than trying to buy the rotary switches and enclosure.

HBP or Sluckey helped me find good deals - thanks guys!

Chip

[Ed_Chambley]

I made mine after Silvergun made his.  I used to use the ones you can buy, but they do not have the caps we use in amps.  I now have 3.  Orange Drops 715 in one, Philips Mustards NOS in another and one with Silver Mica and Ceramics.  This is actually how I found out I like ceramics is lost of locations.

I made a rather large one with Caps and Resistors together.  The resistor portion is nothing but 2 pots so I can dial in preamp tube bypass combinations.  One pot is 2M and the other is a 25K with a switch to select the pot and rotary for electrolytic caps from 2.2uf up to 10uf.  I find I cant really hear much difference in a guitar amp above 10uf.

Keeps the build clean by not tacking in different values and much easier that clipping them in.

[HotBluePlates]

Do you guys ever use a decade box for either resistance or capacitance when tuning an amp?  If so which one do you like?

Use whichever one you get for the price you're willing to pay. 

For the non-lab-grade variety, the thing to watch for is that Resistance sub boxes will likely use carbon comp resistors (may be noisy or drifted), and Capacitor sub boxes may have leaky caps. You never really know until you have the box in-hand and check it out. Some are also a small form-factor, which may be an issue if you want to swap out caps for some exotic variety (polypropylene, large-value polystyrene, large-value mica, or teflon).

For the lab-variety sub boxes (like the General Radio versions), you'll need to have a firm grasp of what resistance ranges you require. Up to 1kΩ (in steps as small as 1Ω)? Up to 1MΩ (in steps as small as 10Ω)? GR had various models with different numbers of knobs and different resistance steps. These things have resistance wire wound on phenolic or mica cards rather than your typical molded film or composition resistors. This is great from a noise perspective (WW will be lowest-noise), but you have to consider the maximum current allowed through each decade (too-high current will cause the resistor card to perform out of spec or burn it open) and whether the resulting inductance is a problem. A single burned-open card on one of those decades will take it and any higher-resistance step in that decade out of operation.

The GR resistance sub boxes may also require cleaning & lubrication of the switch & shaft. I've done that & made a seemingly unusable sub box work like new; if you get that far with a GR box let me know and I'll guide you through it.

The lab-grade GR cap decade boxes generally use polystyrene caps (1419-A?) in a metal enclosure. That's probably the nice one to get. There are some versions with mica caps instead (1419-K?), as well as earlier models in a walnut case with full copper shielding and either mica or paper caps. None of the caps are really "user-replaceable" because they're special caps in a special form-factor for that piece of gear. So you kind of take a gamble on getting a unit that's working properly. If you do (and buy cheap), you have an extremely overbuilt piece of gear that will likely outlive you.

Oh... if you buy off ebay (like I did), wait around for a good deal. Some people will ask crazy prices for old equipment, some will ask extremely-high but valid prices on new gear suitable for a standards/calibration lab, while opther sell at $30-50 for something that's perfectly-good but hasn't had calibration verified since the 70's. My experience has been that the last category is still tight enough tolerance to be better than what my Fluke can resolve (and better than I'd ever really need for a sub box).

[p2pAmps]

I have decided to build my own guys.  Why not, it will be fun and I might learn something along the way which is what I enjoy most.  I ordered stuff from Doug to make my own turret board for the inside etc.  Here we go...

[jojokeo]

Good luck Mike, they won't help with the restorations much rather it's when coloring outside the lines that I find they are close to indispensable. I find I use the cap boxes much more than the resistor ones. They've saved me many many hours and are worth every penny.

[Paul1453]

They can be had quite cheaply on Ebay, if you're willing to wait.

Of course they will not be built as nicely as one you make, Mike.

And the cheapo's will likely have some rust and corrosion to deal with.
Maybe some out of tolerance components too.