Stand alone reverb unit with a high impedance tank

[Draal]

Hi, first post although I've been a lurker for a while. I have a MOD 4EB3C1B 600 ohm tank and wanted to know if it's possible to utilize it in a 6g15 circuit? Is there even a 600 ohm transformer available for such a silly idea? Are my only options a transformer less drive setup or obviously getting an 8 ohm tank?

[sluckey]

A 600Ω tank will not work in the 6G15 circuit and you already stated your options. If you want to build a standalone reverb unit based on that tank, you should study some old Ampeg circuits (I suggest Gemini II) or some Magnatone circuits. Like these...

https://el34world.com/charts/Schematics ... ini_ii.pdf
http://sluckeyamps.com/magnatone/Magnatone_M10A.pdf

[Draal]

Gotcha - cap coupled is the way to go with these Hi Z tanks. Much appreciated!

[mikeywoll]

Another cap coupled version, single tube... From the Benson monarch. Uses an 800 ohm tank, but folks have reported good results with 600ohm tanks as well.

Screenshot_20210920-223945.png

[didit]

Hello --

You may find this article below on a constant-current capacitive-coupled reverb design to be helpful:

http://www.channelroadamps.com/articles/reverb_driver/

Best .. Ian

[Draal]

Hello --

You may find this article below on a constant-current capacitive-coupled reverb design to be helpful:

http://www.channelroadamps.com/articles/reverb_driver/

Best .. Ian

Definitely looks interesting! I know I have a small stash of those old tv tubes in my man-cave.

[jabguit]

dead link - site closed

[sluckey]

dead link - site closed

Looks fine to me.

[Phil_S]

Great article!

[pdf64]

It’s weird how the Monarch reverb driver takes the totally opposite approach by using a CF stage (which more closely approximates a constant voltage output), yet all reports are that it gives great results.
I suppose that the lowish value of the coupling cap acts to provide an approximation of the response that a constant current output stage would have.

[jabguit]

dead link - site closed

Looks fine to me.

Well, you're just Luckey, I guess........

Dead link for me. maybe you've got it cached in your browser.

[sluckey]

Well, you're just Luckey, I guess........

Dead link for me. maybe you've got it cached in your browser.

Haha, you're right. I am luckey. Maybe you are not so lucky. But the link is not dead and I had never been to the site until you said it was dead, so not cached. What message do you get that tells you it is dead?

Here's what you're missing in case you still cannot reach the link...

[Phil_S]

dead link - site closed

Looks fine to me.

Strange. Opened for me without trouble, first time there. Maybe you need to whitelist it for whatever computer defenses you have running? Try a different browser?

[pompeiisneaks]

dead link - site closed

Looks fine to me.

Strange. Opened for me without trouble, first time there. Maybe you need to whitelist it for whatever computer defenses you have running? Try a different browser?

Agreed, I've never been there before and it loaded perfectly fine for me as well.

~Phil

[Ten Over]

It’s weird how the Monarch reverb driver takes the totally opposite approach by using a CF stage (which more closely approximates a constant voltage output), yet all reports are that it gives great results.
I suppose that the lowish value of the coupling cap acts to provide an approximation of the response that a constant current output stage would have.

I'm not so sure that all reports claim great results. Some people have posted threads about cloning this thing and being somewhat dissatisfied with it. At least one report, which I shall submit right now, claims very poor results: It sounds terrible and it's impotent.

There's trouble right out of the gate when the CF is idling at 1.86mA and the nominal drive current is 4.3mA (and you would want to drive the tank with at least twice that nominal current). Because of this operating point, the CF clips on the negative side giving the reverb a sound that I consider terrible. The clipping is worst when the 0.1uF cap and the 95mH coil are near their resonant frequency of 1.63kHz and the impedance of the combination approaches the dc resistance of the coil. This is also the region where the CF delivers the most current on the positive side giving the reverb a shrill sound.

The way that the current on the negative side stops at 1.86mA when the CF clips does reduce the variation in current with frequency, but what a lousy way to do it. It probably wasn't even the designer's intent.

Here is another way to employ a 12DW7

12DW7 Transformerless Reverb 8E.png