Looking for feedback on Transformer Saturation Box schematic

[Brian Roth]

Using your diagram in post 76, do basically the same wiring "again" between the secondary and output jack as part of a 4PDT switch. When the switch is in the "out/bypass" position, pins 2 and 3 of input and output jacks are directly connected and the xfmr. just takes a nap <g>.

I am not making any suggestions re. pin 1 of the in and out jacks....just recommending a flow into the xfmr...or bypass of audio around the xfmr....

Bri

 

[JohnX]

I totally get it now.
Thank you.
It’s after midnight over here and I don’t think I’ve got the bandwidth to start another wiring diagram. Hopefully, I can shoot one out in the morning.

 

[ccaudle]

In post #76 the secondary of the xfmr. is "always" connected to the output jack.

I didn't catch that. I think he was trying to follow my suggestion, but my post had the output connector connected to the switch, so the primary was always driven and a parallel connection to the switch, with the switch for the output connector selecting either transformer secondary or the input signal.

 

[JohnX]

I didn't catch that. I think he was trying to follow my suggestion, but my post had the output connector connected to the switch, so the primary was always driven and a parallel connection to the switch, with the switch for the output connector selecting either transformer secondary or the input signal.

For you & Brian -
When I had made the wiring diagram in number #76, I had actually misread Brian‘s suggestion to put the switch on the output, so I put it on the input instead - so that when the switch is bypassed, nothing at all goes into the transformer.

Just out of curiosity, what would be the performance difference of placing it afterwards on the secondary as you both seem to be suggesting? I am far too much of an amateur to be able to second-guess any sort of design theory.

I am guessing that by leaving the secondary wires connected to the output that it could be causing some sort of loading. Is that correct?

 

[Brian Roth]

Put 2 poles between the input jack and primary as drawn in post 76. Put two more poles between the secondary and the output jack. Hence my suggestion of a 4PDT switch. That will completely eliminate the transformer when in "bypass mode."

Bri

 

[JohnX]

Got it!
Thanks

 

[JohnX]

Put 2 poles between the input jack and primary as drawn in post 76. Put two more poles between the secondary and the output jack. Hence my suggestion of a 4PDT switch. That will completely eliminate the transformer when in "bypass mode."

Bri

OK. I think I did it.
Upward switch position goes directly to the output XLR. Downward switch position goes through the transformer.

 

[Brian Roth]

Not precisely what I had in my mind, but it looks like your solution will work!

Bri

 

[Graham Nystrom]

Thanks, Graham

Would you have an answer for my switch question?

Sorry I didn't see your response sooner. Here is a decent quality and affordable 4PDT switch for you to try.

https://www.newark.com/multicomp-pro/1m41t6b11m1qe/switch-toggle-4pdt-5a-250v/dp/98K4993
And here is a nicer switch for twice the price:

https://www.mouser.com/ProductDetai...=sGAEpiMZZMsqIr59i2oRciiAWmYizrls3VOlrkzF4cM=

 

[JohnX]

Sorry I didn't see your response sooner. Here is a decent quality and affordable 4PDT switch for you to try.

https://www.newark.com/multicomp-pro/1m41t6b11m1qe/switch-toggle-4pdt-5a-250v/dp/98K4993
And here is a nicer switch for twice the price:

https://www.mouser.com/ProductDetai...=sGAEpiMZZMsqIr59i2oRciiAWmYizrls3VOlrkzF4cM=

Thanks so much -
It’s OK. Others have responded as well.

I had been thinking that I could just use an on/on.
But I noticed that both of your suggestions are on/off/on. Is there any benefit to that?

 

[JohnX]

To my knowledge and experience, the ones I ordered and sent you links to are both On-(None)-On

Yes, I just checked the links, no middle position in either switch. Most switches are available in all sorts of configurations, as I'm sure you know, so check the datasheet to be sure.

I think I read on/none/on and my brain turned that into on/off/on. I think you may want to forget that I ever mentioned that.
I know that I do.

Just to be clear, this switch refers to a conversation that we were having about the (single channel) schematic that I have attached below using a DPDT.
A 4PDT switch will be used to bypass 2 channels simultaneously.
Later on is this thread, other alterations/suggestions were made, but I still like the simplicity of this one.

 

[JohnX]

I didn't catch that. I think he was trying to follow my suggestion, but my post had the output connector connected to the switch, so the primary was always driven and a parallel connection to the switch, with the switch for the output connector selecting either transformer secondary or the input signal.

I think I have almost caught up with this thread in terms of diagrams. I have just tried to re-create your suggestion… Correctly this time.

 

[Graham Nystrom]

I've also used those 4PDT switches to access different transformer ratios. (1:1, 1:2, 2:1) In most cases with line output transformers your impedence winding choices will be 150 or 600 ohm. So when you hear 1:2 thats 150:600.

Remember the Impedence ratio is the square of the turns ratio. 1 squared is 1, 2 squared is 4. 150 x 4 = 600.
That said, you can achieve a 1:1 at 150 ohms or at 600 ohms. To each their own sonic signature and effect (on low frequencies esp).

Some like/want/need a little free gain (1:2), some want/need to step down hot mic preamp outputs to a more manageable level for A-D converters (2:1).

Having those impedence ratio options switchable is fun and very useful.

Hope that helps. Every little bit helps me, and I've learned so much from this forum and the fine folks on it.

Cheers,
Graham

 

[JohnX]

I've also used those 4PDT switches to access different transformer ratios. (1:1, 1:2, 2:1) In most cases with line output transformers your impedence winding choices will be 150 or 600 ohm. So when you hear 1:2 thats 150:600.

Remember the Impedence ratio is the square of the turns ratio. 1 squared is 1, 2 squared is 4. 150 x 4 = 600.
That said, you can achieve a 1:1 at 150 ohms or at 600 ohms. To each their own sonic signature and effect (on low frequencies esp).

Some like/want/need a little free gain (1:2), some want/need to step down hot mic preamp outputs to a more manageable level for A-D converters (2:1).

Having those impedence ratio options switchable is fun and very useful.

Hope that helps. Every little bit helps me, and I've learned so much from this forum and the fine folks on it.

Cheers,
Graham

So far, I am focusing on doing very simple Lofi color boxes. I don’t even want to spend money on enclosures. I’m sticking them in candy tins. Since my goal for the lowfi boxes is that they be a little bit more aggressive/assertive, the switching you mention would make sense in that context

However, I also plan to create at least really nice one with a pair of sweet transformers inside of it. For that one, I will definitely implement the multiple switching as you have suggested. I have had the opportunity to try that out in the studio, and I loved the effect that it had on the tracks that we were running through the box.

 

[JohnX]

I didn't catch that. I think he was trying to follow my suggestion, but my post had the output connector connected to the switch, so the primary was always driven and a parallel connection to the switch, with the switch for the output connector selecting either transformer secondary or the input signal.

Hi
I wanted to share with you the finished box. I used your suggestion of driving the primaries at all times and putting the switch on the output of the transformers. This one is a tiny, Lofi box with TRW/UTC SO-15P transformers. I actually just used it on a mix and it sounds really cool. It’s nasty when it distorts but right below that it sounds great.

It was fun making it but in the future, I think I will go for a slightly larger enclosure - it was really a squeeze.

Thanks for all of your help.

 

[JohnX]

I am starting another color box - this one will be utilizing an OpAmp Labs T25

On breadboard, it works perfectly with just input TRS pins 2 and 3 going to trans pin 1 & 8 - trans pins 4 & 5 out to TRS 2 & 3. TRS Input Pin 1 has a direct connection straight to TRS output pin 1 - since I am just breadboarding, there is no enclosure.

My question relates to pin 6 of the transformer, which is marked as “case shield”. Is there any need to connect that to the aluminum enclosure? Again- there was no issue with no pin 6 connection on the breadboard.

should I also connect the pin 1 group to the enclosure? (I have not been doing it on previous builds and it doesn’t seem to be any problem.)

 

[ccaudle]

Is there any need to connect that to the aluminum enclosure?

In this application with no power supply in the enclosure it likely won't be critical either way.

should I also connect the pin 1 group to the enclosure?

Connector pin 1 and not transformer pin 1? The appropriate connector cable shield connection is always to the enclosure.

 

[JohnX]

In this application with no power supply in the enclosure it likely won't be critical either way.



Connector pin 1 and not transformer pin 1? The appropriate connector cable shield connection is always to the enclosure.

Yes - please forgive if I was not clear. Yes, it would be the TRS pin ones (for in & out) which I usually just connect to each other and don’t even bother with the enclosure. I will do it this time.
As always, thanks for both replies

 

[ccaudle]

TRS pin ones (for in & out) which I usually just connect to each other and don’t even bother with the enclosure.

You can get away with quite a lot if there is no active circuitry in the box. Once you start adding circuitry and power supplies you have to think more carefully about those things.

And are you sure you aren't connecting to the enclosure? The picture you showed looked like there was a toothed washer where the connector was screwed into the enclosure, doesn't that make contact between the sleeve contact and the enclosure?

 

[JohnX]

You can get away with quite a lot if there is no active circuitry in the box. Once you start adding circuitry and power supplies you have to think more carefully about those things.

And are you sure you aren't connecting to the enclosure? The picture you showed looked like there was a toothed washer where the connector was screwed into the enclosure, doesn't that make contact between the sleeve contact and the enclosure?

The picture you showed looked like there was a toothed washer where the connector was screwed into the enclosure, doesn't that make contact between the sleeve contact and the enclosure?

You’re absolutely right.
For the last two of these builds, I actually thought that I was ignoring the enclosure and didn’t even realize that the connection was being made anyway (I forgot that I was not using the plastic 1/4” TRS terminals)