Looking for feedback on Transformer Saturation Box schematic

[Sam0311]

Haha I think it’s probably more of an if than a when

 

[Gavin Pursinger]

SIDEBAR...I have a very beatup Sunn 4424 console for parts. It has 24 shielded mic input xformers that deliver to 5532 op amps. These xformers sound great...ballistic and fat that I like. Can I pull those and use them to feed tube pres I build ? Favorites are 5879. 6sn7 ac pairs of 6c5 I love the old octals...paired 6L7s for comp duties.. I don't know much about 5532 or 34 but a blurb sheet said input impedance was 30k to 300k ?
WILL THESE XFPRMERS WORK ???

THX

 

[ruffrecords]

SIDEBAR...I have a very beatup Sunn 4424 console for parts. It has 24 shielded mic input xformers that deliver to 5532 op amps. These xformers sound great...ballistic and fat that I like. Can I pull those and use them to feed tube pres I build ? Favorites are 5879. 6sn7 ac pairs of 6c5 I love the old octals...paired 6L7s for comp duties.. I don't know much about 5532 or 34 but a blurb sheet said input impedance was 30k to 300k ?
WILL THESE XFPRMERS WORK ???

THX

They will work but how well they will work depends almost entirely on their turns ratio. This is fairly easy to check. Feed the input with a low level 1KHz signal (say in the 10mV to 50mV region) and measure the output level on a scope (you need to use a scope for its high input impedance). The ratio of the output voltage to the input voltage is the turns ratio. So long as this is at least 5:1 then it will be OK for a tube mic pre. Anything less risks being noisy but up to 10:1 is fine.

Cheers

ian

 

[Gavin Pursinger]

Thx Ian, a-guttin' I will go...Great news... these trannies are downright ballistic sounding...low end drums, bass and manly men vocals

 

[JohnX]

I hope it is OK that I posted this here in this thread. It seemed more sensible than starting a new thread.

I recently ordered a beautiful color box from Volker, but I got impatient waiting for delivery and decided to make one myself - since I never made one before, I went super cheap with my transformers and got some EDCOR WSM600’s. The version that I made is balanced.

I just tried it out on a track that I was working on and I really love what it’s doing. I ran some fake drums and fake guitars through it, and it really brought them to life. I know that is not particularly scientific terminology, but I only had about an hour in the studio and that’s about as deep as I was able to get. There are two others here made by other people that I had to compare it to and I really liked what this one was doing. I have to be honest that I really didn’t know what to expect from the Edcors but I was very pleasantly surprised.

I have two questions before I begin my next build:

1 - The one thing that I am missing on mine is a bypass switch. Most of the color boxes that I see do not have them and I’m guessing there might be a simple reason…

but IF I wanted to put a bypass switch, would I need a 3PDT (or 4PDT) for each side (box is balanced) for a 2 channel Color box? (A 6PDT for both channels simultaneously?) I don’t think that I can do this with a single 4PDT, but I may also be getting confused.


Because I have to buss out of ProTools into two separate tracks, it’s difficult for me to compare the color box to “uncolored”, per se.

2 - Additionally, I would also like to make a few super cheap versions using even lower quality transformers than the ones that I am using now. Things that will radically alter frequency response, etc. - so that I would be entering deeply into the LoFi zone.

Instead of purchasing enclosures for these cheaper boxes, is it OK if I just use small cookie tins? The only reason I’m asking because I’m not sure if I need the shielding that comes with an aluminum enclosure or if I can get away with using these tin boxes.

 

[jokeramik]

Thanks for this Ian. I think the idea of the resistor was to block any DC going to the transformer, would I be safe to remove the RC filters at the op amp outputs?



Would you mind elaborating on this a little please? What makes this work? Is the idea that putting a resistor with significantly more resistance than the transformers primary adds colour?

Cheers

Why should a resistor block DC?
Best regards!

 

[jokeramik]

The main problem for coupling capacitors in circuits with symmetrical supply voltage is, that you need enough dc across the coupling capacitor. If there is enough dc to blocking, the loss of ac due the coupling capacitor returns against 0. The effect on low-frequencies depends on the capacity. Doulas Self shows the effects in his books.

The better way is to use unsymmetrical supply voltages.

Best regards!

 

[Graham Nystrom]

I hope it is OK that I posted this here in this thread. It seemed more sensible than starting a new thread.

I recently ordered a beautiful color box from Volker, but I got impatient waiting for delivery and decided to make one myself - since I never made one before, I went super cheap with my transformers and got some EDCOR WSM600’s. The version that I made is balanced.

I just tried it out on a track that I was working on and I really love what it’s doing. I ran some fake drums and fake guitars through it, and it really brought them to life. I know that is not particularly scientific terminology, but I only had about an hour in the studio and that’s about as deep as I was able to get. There are two others here made by other people that I had to compare it to and I really liked what this one was doing. I have to be honest that I really didn’t know what to expect from the Edcors but I was very pleasantly surprised.

I have two questions before I begin my next build:

1 - The one thing that I am missing on mine is a bypass switch. Most of the color boxes that I see do not have them and I’m guessing there might be a simple reason…

but IF I wanted to put a bypass switch, would I need a 3PDT (or 4PDT) for each side (box is balanced) for a 2 channel Color box? (A 6PDT for both channels simultaneously?) I don’t think that I can do this with a single 4PDT, but I may also be getting confused.


Because I have to buss out of ProTools into two separate tracks, it’s difficult for me to compare the color box to “uncolored”, per se.

2 - Additionally, I would also like to make a few super cheap versions using even lower quality transformers than the ones that I am using now. Things that will radically alter frequency response, etc. - so that I would be entering deeply into the LoFi zone.

Instead of purchasing enclosures for these cheaper boxes, is it OK if I just use small cookie tins? The only reason I’m asking because I’m not sure if I need the shielding that comes with an aluminum enclosure or if I can get away with using these tin boxes.

You only need more shielding if you need more shielding.

Aluminum and other non-ferrous metals block electro-static while steel and mu-metals block electro-magnetic. So ask yourself first, do you need shielding? And then ask from what kind of noise/interference source? My guess is your cookie tin will work just fine. Keep us "posted"!

 

[JohnX]

You only need more shielding if you need more shielding.

Aluminum and other non-ferrous metals block electro-static while steel and mu-metals block electro-magnetic. So ask yourself first, do you need shielding? And then ask from what kind of noise/interference source? My guess is your cookie tin will work just fine. Keep us "posted"!

Thanks, Graham

Would you have an answer for my switch question?

 

[ccaudle]

IF I wanted to put a bypass switch, would I need a 3PDT (or 4PDT) for each side

You should be able to use a 2P2T for each side. Input signal pair to the transformer and two poles on the switch, output of the transformer to the other two poles of the switch, and output pair from the box to the common terminals of the switch.

 

[MidnightArrakis]

It has 24 shielded mic input xformers that deliver to 5532 op amps.

[It has 24 shielded mic input xformers that deliver to 5532 op amps] -- Are these PCB-mounted transformers, or are they "hard-wired" transformers? Inquiring minds want to know!!!

/

 

[JohnX]

You should be able to use a 2P2T for each side. Input signal pair to the transformer and two poles on the switch, output of the transformer to the other two poles of the switch, and output pair from the box to the common terminals of the switch.

Thanks -
So… In theory, I could actually use a 4PDT switch to bypass both sides simultaneously. Is that correct?
I will try to draw up a wiring diagram in the next day or two.

 

[ccaudle]

In theory, I could actually use a 4PDT switch to bypass both sides simultaneously.

Or even in practice.

 

[JohnX]

Thanks!
I have attempted a crude wiring diagram on my phone for just one side, utilizing a DPDT switch - I used different colors to come out of the switched/bypass side to the output, XLR - (because I wasn’t exactly sure what the symbol for crossing a wire was).
Does this look like it will work?

 

[ccaudle]

Does this look like it will work?

Yes, exactly. The line you drew between the 1 pins of the connectors is just the metal of the cookie tin, not a separate wire.

 

[JohnX]

Yes, exactly. The line you drew between the 1 pins of the connectors is just the metal of the cookie tin, not a separate wire.

Wow! Thank you. I had actually copied that part from someone else’s diagram, and that is actually the way I wired the first box that I made. I will utilize your approach in box number 2.

Maybe this diagram looks more accurate?

 

[Brian Roth]

@JohnX ....in my opinion you need a 4PDT switch so you also disconnect from the secondary of the xfmr.

Bri

 

[JohnX]

@JohnX ....in my opinion you need a 4PDT switch so you also disconnect from the secondary of the xfmr.

Bri

if I read your statement correctly, I think I may be getting somewhat confused about how the secondary would be going back through the same switch.

 

[Brian Roth]

In post #76 the secondary of the xfmr. is "always" connected to the output jack. All I was proposing is to use two additional poles (ie, a 4PDT switch) and do a complete bypass around the xfmr. Maybe I'm missing something buried in all the postings...<g>.

Bri

 

[JohnX]

Aah. I understand now - this would completely bypass the transformer circuit, with a second run from the secondary to output XLR per channel.

And for this method, I would use a single 4PDT for each channel.