Stand alone reverbs

[Madison]

There are two in the Library.
One only has three 9 pin tubes.
The other has two 9 pins and a 6V6 output tube.
Why?
What's the difference?

The one with the three 9 pin tubes, is the tank a rare spec?
If I can't get that tank can I change values somewhere to make a different tank work?

[tubeswell]

The one with the 6K6/6V6 is kinda like a fender champ on the wet side (from the input through to the output transformer), and it drives the pan input transducer with more current, so it distorts more easily.

I think it would be fun to do one that was kinda like a firefly self-split 12AU7 PP output stage with an appropriate PP OT on the wet side (instead of the 6K6/6V6 and the SE OT)

[HotBluePlates]

There are two in the Library.
One only has three 9 pin tubes.
The other has two 9 pins and a 6V6 output tube.
Why?
What's the difference?

Provide a link? I don't know which one you're talking about with 3 9-pin tubes.

Unless one of them is an EL84, in which case it is essentially same-as the 6G15 Reverb, but using a different output tube to drive the tank.

[Madison]

This one.
And can I use a different tank?

http://www.el34world.com/Hoffman/images/HRevskem.gif

[sluckey]

That circuit will use the same transformer and reverb tank as Doug's other reverb circuits.

[kagliostro]

Tubenit has build an unusual unit

a standalone unit with FX Loop + Reverb

http://www.el34world.com/Forum/index.php?topic=10624.msg97554#msg97554

May be you're interested to look at it

K

[HotBluePlates]

The one with the three 9 pin tubes, is the tank a rare spec?
If I can't get that tank can I change values somewhere to make a different tank work?

No, same tank as the other (8Ω input impedance).

Like Sluckey said, same operation, but different tube and transformer to drive the tank. The 6G15 basically uses a tweed champ output transformer.

Myself, I like a Type 9 Medium delay tank. I don't play surf, so I don't need crazy drip.

[Geezer]

I think it would be fun to do one that was kinda like a firefly self-split 12AU7 PP output stage with an appropriate PP OT on the wet side (instead of the 6K6/6V6 and the SE OT)

Got any drawings or schemes or such on that?

Might be something worth developing.......

[HotBluePlates]

Kevin O'Connor sells a tiny push-pull transformer for his reverb circuit.

I don't remember if he uses a 12AU7 or 12AT7, but he uses the halves of the tube in push-pull rather than parallel SE to drive the transformer feeding reverb tanks in his amps. It's a custom Hammond unit that he sells for $62. It is smaller than a 12AX7.

[tubeswell]

I think it would be fun to do one that was kinda like a firefly self-split 12AU7 PP output stage with an appropriate PP OT on the wet side (instead of the 6K6/6V6 and the SE OT)

Got any drawings or schemes or such on that?

Might be something worth developing.......

Just for you (come to think of it - you probably wouldn't even need the CLC filter anymore - but on 2nd thoughts, it might pay to keep it handy, just in case - being a sensitive reverb circuit'n'all)

[Madison]

Can this design (or others) be used for other things rather than guitar?

I am looking for something I could loop in/out of a DAW and or mixer.
Line level I suppose would be best.

Peace

[HotBluePlates]

Anything can be used for anything, as long as you get the impedances and levels right.

But that's the big question: what are the impedances and levels of the ins/outs of your DAW or mixer?

[Madison]

Anything can be used for anything, as long as you get the impedances and levels right.

But that's the big question: what are the impedances and levels of the ins/outs of your DAW or mixer?

Yeah, it's the whole impedance/level thing that gets me.(need to read up on it more)
It would be nice to know I wasn't getting any clipping on the return.

Here are the specs on what I have.

Line Inputs
Frequency response: 20 Hz to 22 kHz, +/- 0.3 dB @ 48 kHz sample rate
SNR and Dynamic Range: -103 dB, A-weighted
THD+N: 0.002% @ -1dBFS, 1kHz
Signal Level: +3.4 dBu balanced
+1.2 dBV, unbalanced
Impedance: 20K Ohm balanced
10K Ohm unbalanced
Crosstalk: < -100 dB @ 1 kHz

[HotBluePlates]

+3.4dBu equals 1.14V RMS (from my google search; verify that with a dB formula and the correct reference voltage).

Assume the 10k input impedance for an unbalanced connection, and that you'll need in excess of 1.5v RMS. That's as bigger than the typical signal fed into a phase inverter, so you know you'll need extra stage(s) after the reverb circuit.

And you'll also need some kind of impedance-conversion circuit, probably a cathode follower of some sort. You could use a transformer, but since you'll need a step-down ratio to down-convert the impedance, your signal level will also be reduced, placing greater demands than stated above ahead of the transformer.

It would be nice to know I wasn't getting any clipping on the return.

You either use your ears, or add some tip jacks for voltage test points, and figure an acceptable voltage reading for that point.

[Madison]

>>Assume the 10k input impedance for an unbalanced connection, and that you'll need in excess of 1.5v RMS. That's as bigger than the typical signal fed into a phase inverter, so you know you'll need extra stage(s) after the reverb circuit.

>>And you'll also need some kind of impedance-conversion circuit, probably a cathode follower of some sort. You could use a transformer, but since you'll need a step-down ratio to down-convert the impedance, your signal level will also be reduced, placing greater demands than stated above ahead of the transformer.

Could I use a reverb pan recovery triode, and hook the line out transformer to the plate of it?

ie going back to this layout, could I hook some sort of line out transformer to V3-3?
http://www.el34world.com/Hoffman/images/HRevskem.gif

To get the right transformer-
Could the spec on the output of the tube be found with a multimeter?
Must do the math?
It is found on the spec data sheet?

That is, IF I even need a transformer to accomplish the task..

(Pardon, I am probably confusing myself and you with these questions.)

>>You either use your ears,

I thought that might work too.

>>or add some tip jacks for voltage test points, and figure an acceptable voltage reading for that point.

This is an interesting idea and likely the easiest.
I will try it sometime.

Thanks a lot.

[sluckey]

Here's a schematic for the Hoffman layout. May help to see circuit options more clearly. I would suggest another gain stage/cathode follower. Remember, this circuit is designed for instrument level input/output signals.

[Madison]

WOW!
This is fantastic.
I gots to build one!

Inset the follower after the Mix pot, correct?
I'd need yet another pot after that for "level"?

Also going to want to stick a TMB in there somehow.
More research for me.

Thanks man

[Willabe]

I gots to build one!

Can this design (or others) be used for other things rather than guitar?

I am looking for something I could loop in/out of a DAW and or mixer.

A stand alone verb or? (what's a DAW and or mixer?) I'm confused by what you are trying to build.     :don't know:

This is if your building a stand alone reverb;

Inset the follower after the Mix pot, correct?

Not really "after".

The CF is for the dry signal that is in parallel with the wet/reverb signal. So it's (CF) really before the mix pot and the mix pot does what it is called. Mixes the wet and dry before they go out.

I'd need yet another pot after that for "level"?

For what? The mix pot and dwell are the "level" controls.

Also going to want to stick a TMB in there somehow.

Why, it's got a tone control, well on the wet/verb side.


                           Brad      

 

[Madison]

(what's a DAW and or mixer?) I'm confused by what you are trying to build.     :don't know:
 

http://en.wikipedia.org/wiki/Digital_audio_workstation

This is if your building a stand alone reverb;

Yepper, gonna try.

The CF is for the dry signal that is in parallel with the wet/reverb signal. So it's (CF) really before the mix pot and the mix pot does what it is called. Mixes the wet and dry before they go out.

Just wondering, can/could it be after the mix pot?
Maybe Steve would chime in here and say exactly where he meant.
Takes me forever to understand this stuff!

Peace.

[Willabe]

I would suggest another gain stage/cathode follower. Remember, this circuit is designed for instrument level input/output signals.

Just wondering, can/could it be after the mix pot?
Maybe Steve would chime in here and say exactly where he meant.

I think he was talking about adding "another gain stage/cathode follower" to get line level signals because you posted this;

I am looking for something I could loop in/out of a DAW and or mixer.
Line level I suppose would be best.

But that's different, which is fine, than just a stand alone unit.

This is if your building a stand alone reverb;

Yepper, gonna try.

I'm still confused, do you want to build;

1. Stand alone reverb for guitar?

2. Build it for line level signals to use with the DAW/loop?

3. Build it to use for both?
 
2 an 3 need the extra gain stage/cathode follower. 1 does not.

              

                         Brad      

[Madison]

>>I think he was talking about adding "another gain stage/cathode follower" to get line level signals

That's the only place where I am stumped at this point.

Thanks bro

I should correct that.
It would be cool to have instrument and line in/outs.
But I could make just instrument work I am sure.

[Madison]

I'm still confused, do you want to build;

1. Stand alone reverb for guitar?

2. Build it for line level signals to use with the DAW/loop?

3. Build it to use for both?
 
2 an 3 need the extra gain stage/cathode follower. 1 does not.

              

I think #3 would be best but maybe too complex for me at this point.
Would love to do it though!!!

[HotBluePlates]

Inset the follower after the Mix pot, correct?

Add the new gain stage, then the new cathode follower after the Mix pot. Remember, you're trying to hit line level after all that stuff.

I'd need yet another pot after that for "level"?

Maybe, but we're spending time trying to boost the signal to get your line level, so throwing it away seems like a step back. I'd think you'd want to adjust the signal level before the reverb's input to adjust overall signal level. My concern is that adding another pot may just be adding a new place to misadjust and get more noise. Of course, you could always try adding a level pot then removing it if it doesn't work properly.

Maybe a level pot immediately after the Mix pot and before the new gain stage. Breadboarding this is probably the best way to figure out what will work best, before building a nicely-crafted finished project and then ripping out/moving various bits.

Also going to want to stick a TMB in there somehow.

Are you sure? Have you tried this kind of circuit with the existing tweed-type tone control?

I ask because this is the standard Fender 6G15 Reverb, and the stock tone control does a pretty good job shifting the reverb tone.

Adding the TMB circuit will entail more signal loss, meaning more to make up somewhere, with more opportunity to add noise, etc. Second, this circuit isn't a stand-alone guitar preamp, and still needs a guitar amp's preamp to boost/shape the signal.

And if you're thinking about tonal control for your recordings, isn't that better accomplished through more elaborate EQ's in your DAW?

I'm still confused, do you want to build;

1. Stand alone reverb for guitar?
2. Build it for line level signals to use with the DAW/loop?
3. Build it to use for both?

I think #3 would be best but maybe too complex for me at this point.

No it's not. 

You know the output of the Mix pot is good for guitar-signal output into an amp, as this was designed to do.

Notice the Output jack is drawn as a switched jack, shorting the hot to ground. This is probably silly, because if you unplug from the output jack, you won't hear any noise anyway. So let's re-purpose that switched contact.

Disconnect the switched contact lug from the ground lug. Add a wire from the switched contact lug to the grid circuit of your new gain stage (with the cathode follower after the gain stage, and a line-level output jack).

Now, the jack after the Mix pot is your "guitar-level output" and is normaled to pass signal to the line-level circuit. If you plug into that output, you break the connection to the line level section automatically.

Things will only get complicated if you want to have both guitar-level output and line-level output at the same time. Even that shouldn't be a big deal, but I'd have to think more that 20 seconds to come up with a good solution. 

[Madison]

Breadboarding this is probably the best way to figure out what will work best, before building a nicely-crafted finished project and then ripping out/moving various bits.

I am going to have to.
Agreed.

And if you're thinking about tonal control for your recordings, isn't that better accomplished through more elaborate EQ's in your DAW?

Good point! I was thinking that too

You know the output of the Mix pot is good for guitar-signal output into an amp, as this was designed to do.

Notice the Output jack is drawn as a switched jack, shorting the hot to ground. This is probably silly, because if you unplug from the output jack, you won't hear any noise anyway. So let's re-purpose that switched contact.

Disconnect the switched contact lug from the ground lug. Add a wire from the switched contact lug to the grid circuit of your new gain stage (with the cathode follower after the gain stage, and a line-level output jack).

Now, the jack after the Mix pot is your "guitar-level output" and is norm

I get it!
Makes sense to me explained like that.

I'd have to think more that 20 seconds to come up with a good solution. 

Please be kind to the electronically challenged 

Thanks for everything.

[HotBluePlates]

I'd have to think more that 20 seconds to come up with a good solution. 

Please be kind to the electronically challenged 

Truth be told, I got lucky with an "error" on Sluckey's schematic.

He has a symbol for a Switchcraft 12A jack, which has a switched contact for the hot lug, in his schematic. This is the type of jack typically used for the input jacks and main speaker output of old Fender amps.

But the original Fender 6G15 Reverb uses a non-switched Switchcraft 11 jack for its output.

When you first said you wanted guitar level and line level, I had visions of a lot of thinking to figure how to provide both. When I saw that switched output jack, it gave me the idea to break the signal there for guitar-level output.

So it did take only 20 seconds, but just because someone else inadvertently gave me the idea.

[Madison]

No no , it makes total sense to me...... what ever way it came about.     

I have noted the conversation and will dig in on it as soon as I get this other project off the bench.

[sluckey]

And don't forget... Since you will be using a line level input you don't need V1. Just put the dwell pot on the grid of the 12AT7 and connect the input jack thru a small cap to the top of the pot. Now you can use V1 for the gain/CF you need at the output.

[HotBluePlates]

Ughh... overlooked that.

He wanted to be able to use line- or guitar-level input.

The easiest kludge is to have some control over output level from the DAW to knock the signal down before input to the reverb unit.

The second-easiest is to add a "line in" jack after that first stage, again using the switched contact to allow a normaled connection when no plug is inserted. That gives guitar-level when not plugged into the Line In jack, or line level with first stage disconnected when plugged into the Line In jack.