is it easy to add reverb to an existing rocket?

[norburybrook]

Hello all, hope everyone is safe and healthy.

With this enforced layoff and zero income I have time yet no funds, so with that in mind modification is probably the only way I'm gong to get the soldering iron out is to modify something.

How easy is it to add reverb to an already build rocket? chassis wise I can step drill a hole for another 12A*7 and add a hole for a reverb pot. Can I point to point the additional components to make this work? I have a tank so that's what made me think about this. I also have plywood/tolex etc so might be tempted to make it into a combo.


M

[martin manning]

You're thinking a one-tube reverb, I assume? http://ampgarage.com/forum/viewtopic.php?p=9999#9999

[10thTx]

Lots of "one tube reverb" examples & schematics here also

http://el34world.com/Forum/index.php?topic=7957.0

[norburybrook]

thanks guys I'll delve into this.

Looks like a good project to learn something new. I really love the reverb on my princeton with the extra 'dwell' pot on the back so I'm hoping I can add reverb to the rocket maybe , or perhaps a different amp and achieve the same result.

Where is the 'normal'/best place to insert reverb , I presume you have to add it before the P.I. unless it was the SE amp the you could adds it at the end of the chain for best results no?


M

[martin manning]

Wherever you put it, you have to mix the wet back with the dry, and then amplify the mix back to a level that is sufficient t drive the output tubes. Generally that means at least one gain stage after mixing, for which a LTP PI can serve. In an SE, I think you would want want to put it before the last gain stage. A dwell control is typically a drive control for the stage driving the tank, and that implies that you have an abundance of drive signal available. That may not be the case with just one 12AX7 triode supplying the tank drive.

[10thTx]

Marcus,

I added a number of one tube reverb to a variety of different amps. They have all been successful & ended up being something I've been happy with.

I am NOT saying you should do it this way, but this is how I personally would approach it. I have not specifically done a Trainwreck.

I have found that I prefer a 12DW7 where pins 1,2 & 3 are more like a 12AU7 and pins 6,7 & 8 are more like 12AX7. I have seen where others weren't too keen on the 12DW7.

You can change the values on the components to suit your taste. I like a .001 dwell cap, you might like 500p. I prefer a 1M reverb pot, you may prefer 2.2M and so on...….
Depending on the voltage on the B+ nodes, you can select node B, node C, node D for the reverb send or the reverb return.

I have one amp that has a paralleled 12AT7 send stage similar to a Fender. I have one amp that has a 12DW7 one tube reverb. I actually prefer the one tube reverb but then I like
a more subtle reverb.

I have found a 1MA dwell pot useful even with one tube reverbs, but again I like a subtle reverb and not something cavernous. I typically put dwell pots on back of the amp as they are a set and forget item for me.

with respect, 10thtx

[M Fowler]

matchless_lightning_reverb_schematic_119.pdf

This Rocket Reverb is very subtle unlike a swampy Twin Reverb but I like it.

Mark

RocketReverbLayoutFinal.jpg

[didit]

Hello -

Reluctance posting just a concept, without proof with tested builds. However, I am finally started my long deferred build based on Blackface Vibrato channel (Deluxe/Pro) tweaked somewhat and stuffed in a Princeton chassis. In interest of socket conservation going with one-tube reverb. There are several triode+pentode tubes in the catalogue. My planned design is based around 6CX8. Pentode in this tube was used in Fender's late '70s Super Twin Reverb, with relevant schematic clip below along with link to full schematic --
====

Super Twin Reverb.jpg

full schematic
====
You can see it fits in the role of classic BF paired 12AT7 driver. The triode can readily be used for recovery.

I have a few Accutronics 4FB2B1A reverb tanks pulled from Peavey '70s era amps that have higher impedance input, and so using capacitor-coupled constant current drive borrowing heavily if not ~100% from --http://www.channelroadamps.com/articles/reverb_driver/.

Build goal is a ~16W grab-&-go with all the features and more of my 1964 BFDR, but not necessarily a perfect sonic clone. It will have dwell control for reverb, a "brite" switch and a "mid" control, and LDR "bug" tremolo. And I expect it'll take me most of the COVID lock-down to finish so cannot promise results proving how well it works for a few months at least. Hope is simply offering some alternatives, and at least ones that have worked for others.

Best .. Ian

[norburybrook]

Ian,

Thanks. I had a peavey USA acusonics tank and stupidly threw it away when I realised it wasn't the correct type to go with my Princeton build. I didn't know enough at the time (still don't ) to work out how to make it work.

It seems there are many ways to skin this cat as we say in the UK so this is all good reading/studying and will make a good project as a single tube verb addition to anyamp would for me be a great addition. I'm even thinking of any of my ODS amps too if it works out.



thanks for all the suggestions. I'm going to mull over this over a beer or 2 tonight. I found out this morning that a friend of mine died from the virus over the weekend, age 64 , I'd known him for over 30 years , came as a real shock

Life goes on though. Stay safe people

M

[martin manning]

Sorry to hear that, Marcus. People in their 60's are most likely to have complications based on the data I've been looking at. I'll raise a glass in requiem here too.

Ian, that 6GH8 pentode triode reverb looks and sounds great. I went to file that away and found that I had already done so, six years ago! If you have a 600Ω tank that is by far the easiest way to add some echo that I've seen. The triode is pretty low mu, but evidently it works just fine.

[Colossal]

This Rocket Reverb is very subtle unlike a swampy Twin Reverb but I like it

Mark,

I like a subtle and usable Reverb circuit. I want a natural decay and the knob to have a good range to it. Fender reverbs, IME and IMO, are almost useless above 2 or 3, unless you are going for Dick Dale. I don't like to hear the crash of the springs, just natural reverb. These days I am of the Robben Ford school and use a Hall of Fame in front of the amp for a little ambience and that's pretty much it. I heard a one-tube reverb circuit in a 36W Marshall TMB type amp and it was very good.

[didit]

Sorry to hear that, Marcus. People in their 60's are most likely to have complications based on the data I've been looking at. I'll raise a glass in requiem here too.

Ian, that 6GH8 pentode triode reverb looks and sounds great. I went to file that away and found that I had already done so, six years ago! If you have a 600Ω tank that is by far the easiest way to add some echo that I've seen. The triode is pretty low mu, but evidently it works just fine.

Hello -

Thanks Martin. Yep, the 6GH8 would certainly be OK. Believe 6CX8 will be as good or better. Check its pentode's transconductance and other parameters, and the triode also has better specs roughly equal to 12AT7. Will require attention adjusting to get the voltages and current correct. My two tanks are both 4FB2B1A with 1475Ω input, so already going to be tweaking. Confident it's all going to be feasible. And can readily switch to transformer coupled should I ultimately find the hifi sonics unappealing. Suggest the 6GH8 would struggle in that circuit design.

Should note well all these pentode+triode tubes are out of production, so only NOS. However, I have pack of 10 6CX8s on the way and cost only ~$25. They were common, as I understand, in high volume TV designs into the '80s.

Best .. Ian

[didit]

Ian,

Thanks. I had a peavey USA acusonics tank and stupidly threw it away when I realised it wasn't the correct type to go with my Princeton build. I didn't know enough at the time (still don't ) to work out how to make it work.

It seems there are many ways to skin this cat as we say in the UK so this is all good reading/studying and will make a good project as a single tube verb addition to anyamp would for me be a great addition. I'm even thinking of any of my ODS amps too if it works out.



thanks for all the suggestions. I'm going to mull over this over a beer or 2 tonight. I found out this morning that a friend of mine died from the virus over the weekend, age 64 , I'd known him for over 30 years , came as a real shock

Life goes on though. Stay safe people

M

Hello Marcus -

Shame about premature disposal of your tank, as recalled it was something you'd had at one point. Do see them offered cheap regularly along with other similar "solid state" tanks pulled from organs and other. kit. That Fender circuit from late '70s Twin should be viable with stock transformer as almost "paint by number" option. I'm sure with the TAG full gang we could get through a prototype to finished design.

I have longer term plans for an off-board reverb+vibrato that can be run off an ODS loop. Perhaps for you that's a way forward before a more ambitious retrofit?

(another poor though thankfully virtual skinless cat limps away)

Condolences on the loss of a friend. Too common these days. Enjoy your mulling over pints.

Best .. Ian