Question about, Reverb Fet Switching (DeadAstronaut Chasm/TimeStream)

[ShadSunsCrash]

If you want to skip the explanation and get to the questions youll find them numbered "1,2 and 3" below.


Let me start by saying ive already driven Rob of DeadAstronaut thoroughly crazy with my questions. All of which he was more than happy to help with which is all the more reason id prefer to stop badgering him and start badgering my brothers and sisters on the forums lol!

With that out of the way heres the problem at hand. I love both of Robs Reverb designs (The Chasm and the Timestream). Each of which are similar but the schematics differ enough that while being similar they are far from the same pedal, circuit-wise and tone-wise. The Chasm has Fet switching which allows for reverb tails which is a major plus since I was looking for a buffered Reverb anyways. And a buffer is important to me since my reverbs go at the very end of my signal chain in the fx loop after a rather large pedal board. In fact I saw where Rob said that he intentionally thought of that (how most people use Reverb last in their signal chain) and it was one of the reasons he went with a buffered/fet switching design.

The TimeStream on the other hand is True Bypass so it obviously does not have tails. Another difference is that the Chasm has a Damp control thats after the BTDR-2H in the circuit whereas the TimeStream has a "Tone" control that is placed just before the BTDR-2H input, among other differences. Ill eventually build both but for now im really leaning towards the Timestream with the intent to add my own buffer at the very least if i do build it first. The main reason being that the TimeStream seems more versatile and allows for more control over the oscillations. The Chasm is a beautiful sounding reverb that im honestly already beaming with ideas for how id use it and how ill do up the enclosure lol. It just seems to me, in my opinion, as if Rob learned a good deal through the process of making the Chasm and it shows in his follow up which is the TimeStream. Specifically he was able to reduce the component count and still end up with a wonderful sounding reverb. So here are the real questions.


1. If i decided to use Fet switching for the TimeStream instead of just adding my own JFET buffer would having Fet switching automatically enable tails? Im almost certain it wouldnt. So on to question 2.



2. If there is more involved to allow for reverb tails other than just utilizing Fet switching could anyone please explain it me or point me in the direction of the info so i could teach myself? (Ive looked and keep hitting a brick wall).


3. On the earlier iterations of the Chasm reverb (known as the Flying Saucer) there was a bright switch that i would like to implement in my build. Does anyone know the component values and where in the circuit this would have gone? All of the old files with this earlier schematic are no longer being hosted so i have no way of finding out myself unless i can find someone with this early schematic. The Chasm is based on the box of hall which is rather bright and i wouldnt be surprised if the bright switch was removing the filtering added to the Flying Saucer (Chasm early iteration) but again, i have no way of knowing without an early schematic. Worst case i can come up with my own bright switch but id still like to know how Rob was accomplishing it since he put a lot of time and effort into getting it just right.


Thank you to anyone who is able to help, its much appreciated!

[stallik]

I’m a little confused (not hard) but curious.

You say that you like the sound of the Chasm and that it has the tails feature that you want. But, Rob created a later circuit that lacked that feature and is described as a simple build on his website so you’d prefer to use that circuit and modify it to behave like the Chasm which you already have and like?

My Chasm is the most satisfying reverb I have - for guitar and vocals so, I’ll watch this thread with interest in case I’ve missed a trick

[ShadSunsCrash]

I’m a little confused (not hard) but curious.

You say that you like the sound of the Chasm and that it has the tails feature that you want. But, Rob created a later circuit that lacked that feature and is described as a simple build on his website so you’d prefer to use that circuit and modify it to behave like the Chasm which you already have and like?

My Chasm is the most satisfying reverb I have - for guitar and vocals so, I’ll watch this thread with interest in case I’ve missed a trick

You are absolutely correct to question and i understand how ridiculous it sounds. I didnt want to flat out say this but i just like the way the "TimeStream" sounds better at lower settings and for the other reasons i stated above. And its not in my head because since posting this i found out that the "Flying Saucer" reverb was actually TRUE BYPASS lol so its possible it became the TimeStream! I had previously thought it was an early version of the Chasm but to me it sounded better and i couldnt figure out why.

Theres a video from DIYPEDALs on youtube labeled Prismatic reverb which is actually a "Flying Sacuer" which before my first post i thought was a early version of the Chasm and i liked it more than the actual Chasm so i wanted to know what the differences were. But i just found a post from Rob saying the Flying sacucer was True Bypass so no tails (so its just like the TimeStream). So i imagine the reason i prefered the TimeStream and Flying Saucer more is because they are a different circuit (not massively different) but enough to make them different pedals tonally. So my ears were validated once I found that out.

I still love the Chasm but for an all around reverb to supplement my amps reverb I prefer the TimeStream for what im after right now. I just want it to be buffered (which is no problem as i can easily add a buffer). But it would also be great to make it so that it had tails also. That would kinda be the best of both worlds. Anyways i hope im being clear. When i get into this kind of stuff my thoughts are all over the place but i assure you it makes sense to me lol!

So how does the Chasm do at lower levels in your opinion? As I said before i love they way it sounds and plan on building one specifically for its higher settings.

Thanks for the reply btw!!! Im glad you asked what you did so i could clarify.

[stallik]

Hmm. Ok, you think the timestream sounds better? I know that these things are very subjective and what you prefer may not be my cup of tea but maybe it’s  time for me to build something else just to try it out.

As for the Chasm, I’m currently using a multi amp setup with the reverb only going to one amp. I tend to use a low to moderate reverb setting and leave it on all the time just to give a bit of ambiance so the tails feature rarely comes into play.

I’ve also used the chasm instead of my PA reverb and my valve driven amp reverbs and in each case, I prefer the Chasm at low/medium and especially full on settings. As I say, everyone has their own preferences but I’ve not looked back since building  mine perhaps 4 years ago? Maybe longer

[ShadSunsCrash]

Thats actually good to hear. The reason i wanted to build the TimeStream over the Chasm is because ive only heard demos of the Chasm at higher settings. And the demos of the TimeStream have shown it works well at all settings. But maybe they both do and i just havent had a chance to hear the Chasm at lower settings.

Im certain i would be happy with either one. And I tend to seriously overthink these things lol. But your comments have certainly been helpful, its good to know that there are Chasm owners out there using it at lower settings successfully! Thanks again!

[antonis]

Let me start by saying ive already driven Rob of DeadAstronaut thoroughly crazy with my questions. All of which he was more than happy to help with which is all the more reason id prefer to stop badgering him and start badgering my brothers and sisters on the forums

In a nutshell, you want us to become Rob's beasts of burden..

[ElectricDruid]

W.r.t questions 1 + 2:

No, FET switching doesn't automatically give you reverb tails.

A non-tails reverb usually turns off the wet *output* from the the reverb, unless it's fully true bypass, in which case it switches the whole reverb out of circuit.

A reverb-with-tails switches off the dry *input* to the reverb not the output, so any signal still in the reverb delayline is allowed to continue until it dies away. This type of circuit *cannot* be true-bypassed (since that would kill the tails) which is where the confusion comes from.

HTH

[ShadSunsCrash]

W.r.t questions 1 + 2:

No, FET switching doesn't automatically give you reverb tails.

A non-tails reverb usually turns off the wet *output* from the the reverb, unless it's fully true bypass, in which case it switches the whole reverb out of circuit.

A reverb-with-tails switches off the dry *input* to the reverb not the output, so any signal still in the reverb delayline is allowed to continue until it dies away. This type of circuit *cannot* be true-bypassed (since that would kill the tails) which is where the confusion comes from.

HTH

That makes perfect sense and in retrospect seems almost comically obvious. Thank you for your answer! So maybe you can also help me track down what Rob was using as a bright switch in the earlier Chasm Reverb designs? Even with the Damp control id still like the option to quickly change from a brighter to a darker reverb. I can certainly think of a couple rudimentary ways of accomplishing this but id like to know how someone more skilled than i went about it lol.

[ShadSunsCrash]

Let me start by saying ive already driven Rob of DeadAstronaut thoroughly crazy with my questions. All of which he was more than happy to help with which is all the more reason id prefer to stop badgering him and start badgering my brothers and sisters on the forums

In a nutshell, you want us to become Rob's beasts of burden..

Couldn't have said it better myself!

[ElectricDruid]

That makes perfect sense and in retrospect seems almost comically obvious.

Glad it helped the light come on. Lots of stuff is obvious once you've seen it, but can be basically impossible to spot beforehand!

So maybe you can also help me track down what Rob was using as a bright switch in the earlier Chasm Reverb designs? Even with the Damp control id still like the option to quickly change from a brighter to a darker reverb.

Switching between a big and a small cap value on that Damp control would be one way. A really small cap (<1n or so) would basically disable the control. This could be done with just an SPST since the two caps could be in parallel and you'd just switch the larger one in for the darker mode.

HTH