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DIY Stompboxes => Building your own stompbox => Topic started by: Itchy Scratcherson on May 01, 2023, 02:35:12 PM

Title: omit the transformer?
Post by: Itchy Scratcherson on May 01, 2023, 02:35:12 PM
Hi! Can someone help enlighten me and also please recommend a workaround? PCB is defx Shard & out-of-stock is the required Xicon 42TM022 transformer. You can locate the transformer in the busy schematic just to the left of the text/Title. Attached PDF specs for the Xicon 42TM series has what appears to be a very close alternative (highlighted), but that's also AWOL/ backordered.

(1.) Even though the xformer's primary is only used for getting the audio into the xformer, do I assume correctly that, in this circuit, the primary input impedance remains as important as it's secondary impedance?

(2.) If it's job is to simulate the loading of a pickup, how can I do this *without* that component?

(3.) Last, re: the possibility of omitting the transformer, the linked thread below states transformers only work with AC input.
(https://www.diystompboxes.com/smfforum/index.php?topic=73768.msg598559#msg598559:~:text=24%3A39%20AM%20%C2%BB-,Quote,-Check%20out%20some)
Is the Shard circuit working on AC up until the transformer?

Thanks for your help!

(https://i.postimg.cc/jWM07WNc/XICON-TRANSFORMER-XC-600134-1212477.png) (https://postimg.cc/jWM07WNc)

(https://i.postimg.cc/1fGdFn1F/defx-Shard-SCHEMATIC-01sm.jpg) (https://postimg.cc/1fGdFn1F)
Title: Re: omit the transformer?
Post by: antonis on May 01, 2023, 02:52:41 PM
Transformer + diodes work for signal octave up.. :icon_wink:

(https://i.imgur.com/alZMKHu.jpg)

There are many substitutions for that..
Title: Re: omit the transformer?
Post by: idy on May 01, 2023, 03:14:10 PM
The transformer is essential for the octave part of the circuit.

Yes, audio is a type of "AC" in that it swings up and down. So audio signals can be transmitted (induced) between windings of a transformer, but DC would only produce one little "jolt" when it turns on. Or off. The rising and falling of a magnetic field.
Title: Re: omit the transformer?
Post by: theehman on May 01, 2023, 03:14:46 PM
Hey, Itchy, I have a spare TM022 I can send you if want to cover the postage.
Title: Re: omit the transformer?
Post by: PRR on May 01, 2023, 04:38:20 PM
> out-of-stock is the required Xicon 42TM022 transformer. ....that's also AWOL/

The DEFX drawing has an error. If you ground two taps on one winding, it is a short.

In the 1970s, the transformer seemed to be simple and cheap. All you really need is out-of-phase signals, preferably strong. An added op-amp will do it. Someone here must know  a plan like that you can use.

Mouser used to have a lifetime supply of the little transformers. Also the datasheet. Similar impedance at different Max Power will work the same.
Title: Re: omit the transformer?
Post by: Itchy Scratcherson on May 01, 2023, 05:33:02 PM
QuoteYes, audio is a type of "AC" in that it swings up and down. So audio signals can be transmitted (induced) between windings of a transformer, but DC would only produce one little "jolt" when it turns on. Or off. The rising and falling of a magnetic field.
You just blew my fragile eggshell mind. Electrified audio is just magic.