NTBT - a few quick questions

[Vic Winters]

I purchased a NTBT-918 (2 band) used from these boards and it only came with the preamp with wires, push/pull volume and blend pots. I've looked at the wiring diagram from Bartolini.net, but I have a few questions.

1. If I were to install this on a bass with only 1 pickup, I wouldn't need the Blend pot. How much would I have to alter the wiring if I wanted to disconnect the Blend?

2. It says I need a stereo jack, is that only if I want to utilize both active and passive? If I only had a mono jack, I assume I'm stuck with only active or passive depending on how I wire it, correct?

3. The wiring diagram has some weird pot values:

Vol: 25K Audio
Blend: 250K
Bass: 50K Linear
Treble: 50K Linear

The volume pot that came with the preamp is stamped A250K. I've never even heard of 25K and 50K pots, is it a typo in the diagram that should be 250K and 500K?

[napalmito]

1. With one pickup forget about the blend, wire the hot of the pickup where the hot of the blend is.

2. The stereo jack is not for going from passive to active, not at all. It's stereo because when the jack is plugged in, the battery is activated (closing the battery's circuit with the sleeve and "non tip" contacts). The tip remains the hot wire.
Without stereo there's no way you can use your preamp, although if you use it with a mono jack, the battery is always in line and therefore decharging all the time.

3. The wiring diagram is perfectly right. Preamps have some "weird pot values" anyway. Don't change the values and find 50kΩ linear and 25kΩ audio pots.
For example, on my American Deluxe Precision preamp, all pots (vol, balance, treb/high, bass) were 100kΩ.

[Vic Winters]

The volume pot that came attached is 250K instead of 25K, so I'm a bit confused.

[Phil Mailloux]

Originally Posted by napalmito

For example, on my American Deluxe Precision preamp, all pots (vol, balance, treb/high, bass) were 100kΩ.

What the heck do you type on your keyboard to get the Ohm sign????!!!

[napalmito]

There's the key on my french keyboard


Seriously, it's a trick I found on a wiki page sometime. Very simple: type & then # then 8486, all these 6 characters attached, show preview of the message you should see the Ω, then post for real. The wiki page is here : http://en.wikipedia.org/wiki/Windows_Alt_keycodes

For the pot, I remember on my NTBT (I had on my Moscato Legend 5) that the pot was a high one, 250KΩ seems appropriate to be able to switch from passive to active.

[Vic Winters]

First is the stock image from Bartolini.



Second is my untested, modified version without a blend and with a push/pull volume pot. Can someone tell me if it will work?

[napalmito]

I think it's good to go, but I see too that the push-pull won't have any effect wired like this.
What do you intend to do with your push-pull ?

[Rano Bass]

Originally Posted by Vic Winters

Second is my untested, modified version without a blend and with a push/pull volume pot. Can someone tell me if it will work?

The red from the pup goes to the center of the volume pot.
Wire the preamp like on this pic, it's a vol-vol example but just ignore the first volume pot and you'll be fine

http://i93.photobucket.com/albums/l4...vol-vol-tb.jpg

[Vic Winters]

Originally Posted by napalmito

I think it's good to go, but I see too that the push-pull won't have any effect wired like this.
What do you intend to do with your push-pull ?

I was hoping to use it for active/passive.

[napalmito]

Like this the push-pull works in passive when these pins are connected :

0 0
| |
0 0

0 0

: the HB+ is wired on the vol pot and the battery is offline



and in active when

0 0

0 0
| |
0 0

: the NTBT is wired and the battery online.

[Vic Winters]

Awesome, thanks a ton.

[BobXboB]

The original 25k volume is coming after the pre and will work on the buffered signal the pre sends. If you want to use a 250k you can move the volume to the other side of the pre in the circuit so it works with the hiZ from the pickup before hitting a buffer in the pre and controls the volume of the signal going into the pre. Effectively changing from an active to passive volume. It will work fine but the original way can be quieter.

[BobXboB]

Also, all the tone caps are missing from those diagrams. Don't want to leave those out

[napalmito]

All the tone controls are active, so there's no capacitor involved ?

[BobXboB]

There's caps in all the preamps I know. I think I confused the NTBT with the older TBT which has many of the caps outside the preamp

[Vic Winters]

A few more questions:

What would be the effect of using 500K pots for the Bass and Treble? The only 50K pots I've found locally aren't of the mini variety and take up too much space. I found a few places online that sell mini 50K pots, but I have a set of 500K pots lying around without a purpose and I'm just curious what the different results would be.

What are the dimensions for routing a battery box?

[cofibreyk]

&#8486

[napalmito]

Originally Posted by Vic Winters

What would be the effect of using 500K pots for the Bass and Treble? The only 50K pots I've found locally aren't of the mini variety and take up too much space. I found a few places online that sell mini 50K pots, but I have a set of 500K pots lying around without a purpose and I'm just curious what the different results would be.

Can't say but I think the tone will be changed on the 0 to 50kΩ range and then the 50kΩ to 500kΩ will be useless. Therefore I don't recommend you to use these.

Originally Posted by Vic Winters

What are the dimensions for routing a battery box?

Buy one and figure out the dimensions then. It's not a good idea to rout without the box in hand. All battery boxes aren't the same and you could have a bad surprise.

Originally Posted by cofibreyk

&#8486

Try a preview or two until it appears right.