Switching the dual voltage PT taps

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BashCoder

Post by BashCoder » Thu Nov 02, 2006 2:24 pm

Or put it on the top of the chassis, next to the other 10-turn Bournes bias pot. :wink:

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mightymike
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Post by mightymike » Thu Nov 02, 2006 3:05 pm

I hear ya on the filterboard Mark, both our 12000s have that 27k right in the corner of the tone board, so we don't have much choice, but on his handwired 1969 era with chassis mounted filter caps, he has a nice unused perf hole right next to the turret where his 27k meets the white wire. If it was me, I would install a turret in that unused hole right next to it on the edge, then move the white wire to that turret you just installed, now put the bias pot from that new turret to the turret where the white wire was. Then still put the break in the white wire at the switch the same, but now you have pot on the toneboard and clean looking.

Almost like it was meant to be.


There is only one thing missing though. :cry:
How can I make my screen filtering increase when I'm on the high taps, without adding another switch....
might need a 4 gang version of this dual tap switch George.

Then replace my 2 BC 33uf Axials, with 2 Dual Section 32x2 F&Ts for the screens, and put the switch on the jumpers that make the caps single or jumpered across the positives. It's not quite double jumpered 50s, but with the added plate voltage, the added filtering will enhance the effect.
Last edited by mightymike on Thu Nov 02, 2006 3:08 pm, edited 1 time in total.

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Post by rockstah » Thu Nov 02, 2006 3:08 pm

mightymike wrote:I hear ya on the filterboard Mark, both our 12000s have that 27k right in the corner of the tone board, so we don't have much choice, but on his handwired 1969 era with chassis mounted filter caps, he has a nice unused perf hole right next to the turret where his 27k meets the white wire. If it was me, I would install a turret in that unused hole right next to it on the edge, then move the white wire to that turret you just installed, now put the bias pot from that new turret to the turret where the white wire was. Then still put the break in the white wire at the switch the same, but now you have pot on the toneboard and clean looking.

Almost like it was meant to be.


There is only one thing missing though. :cry:
How can I make my screen filtering increase when I'm on the high taps.
might need a 4 gang version of this dual tap switch George.

Then replace my 2 BC 33uf Axials, with 2 Dual Section 32x2 F&Ts for the screens, and put the switch on the jumpers that make the caps single or jumpered across the positives. It's not quite double jumpered 50s, but with the added late voltage the added filtering will enhance the effect.
i hear ya there Mike!

the screen idea is kewl - does it/ will it work?

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Post by mightymike » Thu Nov 02, 2006 3:15 pm

I haven't tried it yet..but it makes sense on paper :P

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Post by mightymike » Thu Nov 02, 2006 3:47 pm

If you weren't using that side of the dual tap switch for bias tracking, then it could be used to add capactance in paralell with either screen, but not both, and change taps.

This switch would have to be 2 more poles (5 total), to add cacitance to both screen caps at the same time if using dual 32ufs, and still switch the bias tracking, and the dual taps. That thing is already 3wide.

You could get away with a switch with only one more pole, if that one switch added a double jumpered 50uf to either screen, but I don't know if a mismatch on the screen that great is such a good idea . I know George wasn't wild about me having a mismatch of 47uf and a 33uf for screens, so adding 100uf in paralell with only one of the screens might be pushing a mismatch. So if I did it, I would have to be a 5 pole, and I would still wait a couple seconds the middle position when changing taps, just to give the river a chance to adjust to the new rules with out any drop D power chords hitting at 10. :wink:

Or just put it on a separate switch. Get another dual tap switch and call it Plexi /Metal Face and have it change 2 of the screens and one other thing of your choice, beit the V3 or Preamp cap values, or even the tone stack.
Hopefully it doesn't get too noisy with all the extra wiring. Might have to use a lot of Beldon for that amp.

I used to be good at figuring out switching with TTL, but my my guess it would take about a 10 pole switch to do a true Plexi - Another era switch, where it switched everything with the flip of one switch.
Taps --- 2 poles
Bias --- 1 pole
Screens- -- 2 poles
Slope ---- 1 pole
V3-----1 pole
Preamp cap---- 1 pole

That's 8 and we haven't go into changing treble caps, couplings cap

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Post by rockstah » Thu Nov 02, 2006 3:49 pm

very interesting Mike. :D

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Post by mightymike » Thu Nov 02, 2006 3:55 pm

8)

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Post by 45auto » Fri Nov 03, 2006 11:13 am

just pour concrete over it...cheap!
http://www.soundclick.com/bands/default ... dID=559714" onclick="window.open(this.href);return false;
http://s62.photobucket.com/albums/h119/ ... t=1980.flv" onclick="window.open(this.href);return false;

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Post by mightymike » Sat Nov 04, 2006 6:08 am

I just listened to your clips
We can do better than this rocks. Phycotic duck cracks me up, but I like it in a weird way. The beats in both these songs remind me of David Girabaldi of Tower of Power. Especially Phycotic duck, which is similiar to the beat in Squib Cakes.

Good stuff :D

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Post by 45auto » Tue Nov 07, 2006 1:56 pm

thanks, means alot coming from you. maybe it's the wacky (quacky) horn section that does it. hehe
http://www.soundclick.com/bands/default ... dID=559714" onclick="window.open(this.href);return false;
http://s62.photobucket.com/albums/h119/ ... t=1980.flv" onclick="window.open(this.href);return false;

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Post by Souelle » Sun Dec 03, 2006 1:39 pm

Hello,

Since i'm not very good in english and want to make sure that I understand it well, I have made a layout...

On My PT the standard voltage is blue, and the low one is red.

I have to remove the bias tap that goes to the board (27k) and put it on the switch, right ? (i have put it pink on my layout to make it visible)

The resistor on the switch is there to balance the bias for the low voltage option, is that right ? So I need to try different value between 22k - 33k to make it right.

Can you let me know if I got it right on the layout :
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Post by novosibir » Sun Dec 03, 2006 2:04 pm

You've got it!

Larry
The fault almost always is sitting in front of the amp :wink:

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Post by antosimoni » Mon Dec 04, 2006 3:59 am

mightymike wrote:I hear ya on the filterboard Mark, both our 12000s have that 27k right in the corner of the tone board, so we don't have much choice, but on his handwired 1969 era with chassis mounted filter caps, he has a nice unused perf hole right next to the turret where his 27k meets the white wire. If it was me, I would install a turret in that unused hole right next to it on the edge, then move the white wire to that turret you just installed, now put the bias pot from that new turret to the turret where the white wire was. Then still put the break in the white wire at the switch the same, but now you have pot on the toneboard and clean looking.
....
sorry Mike what do you mean for "the break" my apologies for my poor english :oops:
in loudspeakers we trust

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Post by mightymike » Mon Dec 04, 2006 6:36 am

Don't feel bad, English is my primary language and I'm not so good either.

The switch on the bias creates a "break" or open in the white bias wire that goes from PT to the 27k on the tone board. when it's in the open position, there a resistor across it, it becomes the value of the resistor

(We were talking about putting the extra bias pot or resistor on the Filter board, because my first attempt at dual Tap bias pot looked kinda ugly on the first install. since then I solder them up in a much better way, so I'm leaving them on the switch) I'll try to get a pic so you can see. It's looks a lot better. I use the later style 25k bias pot to do this, like George uses on his 69 kit. The one with the 3 terminals. I cut off the third.

Here's how the switch works: When you're on the high taps, that bias switch is closed. Not doing anything.

when you're on the low taps, the bias switch is open, but there's a resistor across that open switch(in my case a 25k bias Pot) that the bias supply is then forced to go through to get to the 27k

So basicly the switch adds resistance in series to the 27k on the board when the lower taps are selected. Since the switch is really only changing anything when it's in the open position, it needs to be on the same side as the high taps, but it's actually only adding resistance when the lower taps are selected. Just remember to wire it to the high side to `control the low side.

If you were looking at the bias part of the switch by itself, it's just a switch with a resistor in parralel. Closed - the resistor is bypassed, open - it adds the resistor to the circuit., by puting it on the third gang of that dual tap switch you're just making it work in congunction with another switch, almost like a relay or logic circuit in it's simplest form.

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Post by antosimoni » Mon Dec 04, 2006 8:27 am

thanks Mike !!!!! :wink:
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