Transformer balancing a spring reverb

[Clintcleveland]

Hi all,

I built the Mod Kits "The Wave" spring reverb kit (schematic attached), which ended up being a pretty useful toy.
However, I'd like to transformer balance it, since it's not nearly heavy or expensive enough
I'm thinking Carnhill VTB-2381 (600:15K) for the input and VTB-2290 (9600:600) for the output. Would anyone care to weigh in on whether I'm thinking the right thoughts?

Thanks in advance,
Clint

 

[Tubetec]

Balanced studio line level input via a transformer would most likely overdrive the input stage as its designed for pickup input . Tapping in before the driver circuit might be possible ,while retaining the standard low level jack input .
The tank output transducer can be wired for balanced connection by adding a TRS jack instead of the phono , a 300-600 ohm output transducer works well enough into a standard mic input .
You would probably need to redesign the output circuit for use with the carnhill transformer , a plus is you have a spare 12at7 section you could use .

 

[Clintcleveland]

Thanks for the advice, Tubetec! That also reminds me I need to get rid of those front panel jacks before someone plugs a guitar into it and goes on a 20 minute surf noodle. I think the spare 12at7 section is the way to go

 

[Tubetec]

Id consider keeping the front panel low level pickup input , it might come in handy ,
something like a 10k:10k transformer just before the tank drive circuit might be about right for line level balanced input , a switch might allow either low level pickup input or line level from a mixer Aux send
Using the spare 12at7 section as a cathode follower to drive an output transformer might be worth looking at .

 

[iampoor1]

You can put a 1:1 transformer on the input and add a u pad to get whatever level your happy driving it with in the line level range. On quick glance it doesnt look like that output stage has much ooomf to drive a transformer tho. Is there a reason you want to add transformers other than because they are transformers? Why not try running it unbalanced and add a transformer only if its needed?

 

[Clintcleveland]

Id consider keeping the front panel low level pickup input , it might come in handy ,
something like a 10k:10k transformer just before the tank drive circuit might be about right for line level balanced input , a switch might allow either low level pickup input or line level from a mixer Aux send
Using the spare 12at7 section as a cathode follower to drive an output transformer might be worth looking at .

True. I've never regretted having an extra input around. I'll mostly be using it on a send, but it couldn't hurt to have the low level jack just in case

 

[Clintcleveland]

You can put a 1:1 transformer on the input and add a u pad to get whatever level your happy driving it with in the line level range. On quick glance it doesnt look like that output stage has much ooomf to drive a transformer tho. Is there a reason you want to add transformers other than because they are transformers? Why not try running it unbalanced and add a transformer only if its needed?

That makes sense, thanks. I guess the main figuring I need to do is on the output, but I hadn't noticed the unused section Tubetec mentioned. My area is electromagnetically unsanitary, and transformers seem to help quite a bit.

 

[iampoor1]

Yeah that makes sense. Using the 12at7 as a cathode follower and driving your suggested Carnhill transformer should work alright And hey, not that much additional work!

 

[1000tinyempires]

I have found that reverb circuits designed for guitar or other "medium" level signals can't handle line level. You may actually be able to get away with an interstage transformer wired backwards. That's more expensive for most projects than just using a pad and a 1:1 transformer, but the magic of reverb is that it loves middling frequency response, so this is where you can use up all those $10 transformers that say "300-3k" that nobody wants. I would buy a lot of mixed undesirable transformers and see what works.

 

[Brian Roth]

Edcor xfmrs would also be a suitable choice at a low price point.

Bri