Reverb tank impedance

[gtomax]

I'm going to build a Selmer Thunderbird 30 as a fun project to kick off the new year. Since I'm doing it from scratch I have some liberties as I'll be making my own chassis, etc.

For the reverb section: is the impedance of the tank determined by the driver transformer used? Example: if I use a Fender spec reverb transformer should I pair a Fender style reverb tank with the amp? Or is it determined by the driver/recovery circuits?

I'd like it to be as close to an original Selmer reverb as possible but specs on the transformer and tank are hard to come by.

I'll be building it with a Heyboer 8087 spec power transformer since B+ is about the same range and it's got plenty of current capability on 6.3 and 5v circuits plus it comes with the nifty 50v bias tap. Output transformer is going to be an old Stancor A-8056 for 6k6 primary to fit 2xKT66s or EL34s and I'm going to include a cathode/fixed bias switch to have the amp be selectable between the twin 30 or twin 50 style.

[thetragichero]

yes, you would use a low impedance tank (quick google of deluxe reverb has 8 ohm) based on your transformer impedance. i have no idea what transformer selmer used since 4FB3A1B comes up as a replacement tank (for the 50, at least) and that has a high (1475 ohm) input impedance. if you don't mind using fender-type, those transformers and tanks are available pretty much everywhere
this came from a couple quick google searches so by all means wait for confirmation before ordering

[gtomax]

If input impedance can be determined by the driver transformer (in this case if using a fender driver xformer something like an 8 ohm sounds right), what determines output impedance? The recovery stage circuit?

I've seen some posts for the thunderbird saying an 8 / 2250 tank could be correct but there's not a lot of reliable info out there. I do have the thunderbird 30/50 schematic which if the recovery stage determines optimal tank output impedance seems like the best way to deduce it.

Anyone savvy know how to calculate it given the schem?

[Stevem]

To start off with you should go to the tech info section on the Tubes & More web site.

Since your starting with a clean sheet of paper in terms of the tank, then if the amps cabinet is tall enough get a tank who's 7th diget is a E or F.

These tanks mount vertical and are way less likely to bust the springs out at there ends when traveling due to the fine hard wire these supports are made from on all tanks!

[turbofeedus]

Wow I just looked up the price on vintage Selmers, crazy money!
Following this build, looks like a good investment.
Also, I did a cathode/fixed bias switch on my 7591 bassman build, and I love it.