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Good morning chaps.

I had a bit of time last night, so I pulled out the tank and moved it around a bit.
The hum wasn't too bad, and it was evident that a previous owner had already done some work to reduce feedback etc.

It's encased in a pretty stiff tolex bag and the output coil was already oriented away from the transformer (which is unshielded).

To satisfy my curiosity I moved the tank about and managed to make the hum waaaaaayyyyy worse. My experimenting came quickly to an end when I got too close to the speaker and the magnet grabbed it out of my hands and made a heck of a noise, of which my wife was none to enthusiastic to hear again.

I am going to try the matchstick thing when I have the house to myself.

After doing a bunch more reading and the evidence that the tank can output super wet clangs, I think the driver circuit is the section where the lack of power is coming from.
According to http://www.tubesandmore.com/scripts/foxweb.dll/extpage@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?page=TECH_REVERB the input coil needs to be driven close to saturation in order to get the most out of the reverb pan.

This has implications for my stereo spring tank project which I've been tinkering with for two years (hey I'm easily distracted by electronics, so many unfinished circuits, so little time.).

I forgot to mention in my last post that my flat has a massive problem with EMI.
The source of the interference is unknown, but it's not generated in the bit of the building that I rent.

I have to face my single coil guitars a certain way, otherwise it's hum city.

There is one spot in the lounge where it isn't too bad, so I mostly play between the two couches.

Hi gang, I'm revisiting my desire for big splashy reverb in this amp.
Looking at the official schematic and re-reading opamp theory, it seems to me that R26 could be tweaked to increase the gain factor.

Basically its a non-inverting opamp which has gain controlled by a pir of resistors.

R26 is 22k and is placed between pin 1(out) and pin 2(-in).
R34 is 22r and placed between pin 2 and ground.

The math for the gain factor is (R26/R34) +1 or (R26 + R34) / R34 in either case, the gain appears to be 1001.

So by increasing R26 to 30k, the gain factor should increase by 364 points. Am I right?

Thinking further about this, would that then cause the opamp input to begin to clip wityh no real increase in the output to the driver coil?

It's been a long time since I studied op amp design, so I'll have to look it up before I can answer correctly, but the reverb tank is not connected as a normal load at the output of the chip. It is part of the feedback loop paralleled with R26, which I think makes it a constant current design. If you have the textbook, look it up and see if I'm right here or not.

Mr. Bill wrote:It's been a long time since I studied op amp design, so I'll have to look it up before I can answer correctly, but the reverb tank is not connected as a normal load at the output of the chip. It is part of the feedback loop paralleled with R26, which I think makes it a constant current design. If you have the textbook, look it up and see if I'm right here or not.

Oh that makes sense, I forgot about the coil I was trying to drive, as a factor in my equation.

Even assuming that the load is a perfect 600r in the inductor, that means the gain is somewhere around 27 in a conventional design.
I'm no engineer, so I've only got enough information to make guesses. I've worked on lots of pedals where my idea would have been ok.
I think might've worked on an inductor once before. Not counting my string of reverb failures.

Well I've decided to sell the Peavey Delta Blues.
It's a sweet amp, but not a surfing amp, at lease not with the reverb the way it is.

This week I've played with reissues of the Fender 63 tank and the 65 Deluxe Reverb.
I like the Tank and would consider buying it, but not in my home country. I can get one 50% cheaper from USA including shipping!
The 65 however really knocked my socks off.

That's the reverb and gritty drive I've been craving for all of these years.

So... now I've just got to shift some gear on that infamous Auction site and get myself a sonic super soaker.

MissionBrown wrote:I can get one 50% cheaper from USA including shipping!
The 65 however really knocked my socks off.

That's the reverb and gritty drive I've been craving for all of these years.

+1 on the 65 reissue Deluxe Reverb. I had a hard time choosing between a 65 DRRI and a Custom Vibrolux Reverb RI but ended up buying the latter (for more watts; 44W instead of 22W). They're both very fine- and desirable amps but the tone and the reverb in the 65 DRRI is arguably way better (different circuit). I'm not over it yet and I know that I shall one day trade my CVR in for a 65 Deluxe Reverb RI

If you're planning to snag a tank from the USA, bear in mind that the mains voltage over there is 120V

Veenture wrote:

MissionBrown wrote:I can get one 50% cheaper from USA including shipping!
The 65 however really knocked my socks off.

That's the reverb and gritty drive I've been craving for all of these years.

+1 on the 65 reissue Deluxe Reverb. I had a hard time choosing between a 65 DRRI and a Custom Vibrolux Reverb RI but ended up buying the latter (for more watts; 44W instead of 22W). They're both very fine- and desirable amps but the tone and the reverb in the 65 DRRI is arguably way better (different circuit). I'm not over it yet and I know that I shall one day trade my CVR in for a 65 Deluxe Reverb RI

If you're planning to snag a tank from the USA, bear in mind that the mains voltage over there is 120V

I can change a transformer over no problem, or buy an adapter.
Either option still leaves me with a few hundred clams in the pocket.

Have played a Princeton today, the volume is more suitable to home, but I like the Deluxe better.
Weather permitting, I'll scoot up to another store and see if they have both in stock tomorrow.