Selmer Zodiac Twin 30 Tone Control - are this circuit the same ??

[kagliostro]

I've intention to experiment with the Tone Control of Channel 2 of the Selmer Zodiac Twin 30

the original amp uses a Push Button Control where I think each button is mutually exlusive

instead of the use of the push button I've think to use a more common rotary switch with 2 way 6 positions

and I've draw this version of the circuit




are the two circuits the same ?




Complete Channel 2 Selmer Zodiac Twin 30 schematic

Many Thanks

Kagliostro

p.s.: To mee seems that 9.5H is a very large inductor does someone can confirm that 9.5H is the right value ?

[kagliostro]

Hi Drgonzonm Thanks for revising

There seems to be a mislabel high Bass instead of High Treble

Now that is fixed (in the first message)

the jsch does not show an off position

Do you think there is an off position ?

for the other warnings I'll try to understand and to fix (than I'll post the correction)

EDIT:

The pdf shows the 420pF-1m resistor series only in play when when the high treble is selected

Assuming that the push buttons used by Selmer are mutually exclusive:

.when the button corresponding to the High Treble (S2-A / S2-B) is pushed the 420pf + 1M aren't engaged - the signal go directly to the Volume 1MA pot (on the right of schematic)

. when the button corresponding to the High Treble (S2-A / S2-B) is NOT pushed  the 420pf || 1M are in series to the signal going to the 2100pf + 1MA (Rotary Tone Control)

The jsch has this occurring on an unlabeled tab

I don't see ulabeled tabs

Could the difficulty be as result of double contacts on the pdf nodes rather than the single contacts shown in jsch?

the original uses 6 push buttons (that I think are mutually exclusive)

my version for easy availability try to use a 2 way 6 position rotary switch

here is an original schematic (not one redraw)



Kagliostro

[kagliostro]

The is an off position, all push switches up.

unfortunately that is useless, no connection no signal to the next tube

The series CR, tied into the NO side of the treble goes nowhere until the high treble is pressed, then the series CR  becomes part of the circuit, it is fed in series from the treble NO contact.

I emulated that with the 2 x 6 Rotary Switch

when in position corresponding to High Treble, the signal go between the 420pf || 1M and the 2100pf + 1MApot but the extemity of this are disconnected, so the signal go direct to the Volume pot with in parallel the inductor

Kagliostro

[kagliostro]

I got some interesting info at AGGH from Peter and I post here for those who can be interested

There are a number of Selmer amps that use a similar push button tone selector, the Selectortone Twin, Selectortone Auto and Rotary Selectortone. You can find the schematics at Schematic Heaven.

http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin.html

so I verified that the 9.5H value of the inductor is confirmed

I suspect that selector switch in the re-drawn schematic is incorrectly labelled.  I suggest that S2 is Low Bass and that S6 is High Treble.  I expect that Roly will double check my thoughts on this.  S2 gives a shelving cut, bleeding low frequencies to ground.  S3, S4 and S5 perform switching for band cut (or band stop) filters.  The combination of the .033µF capacitor with the 9.5H inductor will have low impedance at 284Hz (for the pedants, it calculates to 284.25Hz), creating a cut which is centred at that frequency.  Similarly, the combination of the inductor with the .01µF cap will give a cut centred around 516Hz and, with the .0033µF, 898Hz.  IMO, the two latter figures are a little low to be called mid and treble, but that's the way they have done it.

Note that the impedance of the preceding high pass filter will not be constant, and it will affect the overall response of the various tone switch settings.

The schematic will work as you have drawn it, bearing in mind that the designations (Low Bass, Bass, Medium, Treble, High Treble) will be reversed.  On the input side, there does not appear to be any need for the connection between the point that you have labelled "High Treble" and the junction of the 420pF and 2100pF caps, even though it is there on the original schematic.

here the original schematic of the Selmer Rotary Selector

http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin/selmer_rotary_selectortone_15w.pdf

Kagliostro

[HotBluePlates]

so I verified that the 9.5H value of the inductor is confirmed

Just remember that inductor only needs to be rated for a milliamp or two; don't get a 9.5H choke for a power supply!

[kagliostro]

Just remember that inductor only needs to be rated for a milliamp or two; don't get a 9.5H choke for a power supply!

Hi HBP thanks for the advice, I know that, only I'm not able to find a little 9.5H inductor (till now)

till now I've find only inductors like this

http://www.tube-town.net/ttstore/product_info.php/info/p1648_Hammond-Choke-154G.html

Thanks

Kagliostro

[kagliostro]

Hi Drgonzonm

Yes, you are right, the circuits aren't exactly the same

Kagliostro

[Katie 77]

equivalent circuits of each pushbutton

[kagliostro]

Hi Katie 77

thanks for posting the pdf file

---

Here some simulation by courtesy of Roly member at AGGH Forum

















those simulation where done as to investigate about the specs of the 9.5H inductor about which nothing is known if not the impedance

Kagliostro