From: Steve A. (steve_ahola@yahoo.com) Date: 10/13/2000 7:22 AM Subject: Anybody added reverb to their D'Clone...? This was brought up in a recent post so I thought I'd ask! The typical Fender reverb circuit squeezing all of the dry sound through the 3M3/10pF splitter would not do justice to the overdrive stages... Several ideas have been suggested but has anybody gotten some good results yet? One scheme suggested tapping the reverb input signal early in the circuit (like right after the volume control before CL2, or after the CL2 coupling cap) and then feeding the reverb signal back in right at the input to the PI. FWIW I don't think that a decent OD section really needs reverb, but mixing in some reverbed clean signal might be interesting... Then again Mesa Boogie seems to be able to "reverberate" their OD signals just fine... (love that Maverick!) --Thanks! Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 295 times From: Matthew Springer (mspringer@comtier.com) Date: 10/13/2000 3:48 PM Subject: Re: Anybody added reverb to their D'Clone...? Yep, I've been wondering about this more than is healthy. (not that being an audiophile/amp nut is exactly a rational/healthy pasttime) I would agree about not needing reverb for the OD mode, but clean, I just need my spring reverb. Deos anybody have any idea how the 2 rocks or fuch audio amps are doing it (Obviuously, I don't want anybody givig away trade secrets, though). -Matthew START NEW THREAD REPLY PREVIOUS LIST Read 287 times From: JaySG Date: 10/13/2000 5:18 PM Subject: Re: Anybody added reverb to their D'Clone...? "The typical Fender reverb circuit squeezing all of the dry sound through the 3M3/10pF splitter would not do justice to the overdrive stages..." hmm, high pass at 5kHz...I don't have a clone, just an ODS channel in a Fender w/Reverb amp. I noticed that the Dumble Overdrive/Reverb amp didn't fare well in Bill Morgan's shootout 2000. In my case, it might be easier to implement reverb in the fx loop. Okay, here's an alternate question which Gil may be able to answer: Does Reverb in the fx loop sound better than the normal Fender paradigm? START NEW THREAD REPLY PREVIOUS LIST Read 282 times From: Gil Ayan (ayan@earthlink.net) Date: 10/14/2000 4:23 PM Subject: Re: Anybody added reverb to their D'Clone...? For what it's worth, the Overdrive Reverb amp does not do the "Fender reverb" thing inside. I can't quite remember the circuit off the top of my head, but it taps the signal right after the tone stack and, with an isolation resistor, sends it to the reverb circuit. On the return side, I think wet and dry signal are mixed using a "Tweed mixer" type of circuit or something like that. This amp uses I believe 3 extra tubes... Never heard one. I do know that the FX loop of the D'clones works very well with a D-lator clone. However, some people use a BOSS RV-3 pedal in the loop, without anything else, and get good results. I have tried using my FX without the D-lator clone and the sound becomes a little chessier. But, the main problem is that you have to watch your master volume level (which is the FX send level from the amp, if you will), or else you may overdrive your FX. And with that comes the following problem: your FX box may not have enough gain to make the signal going back into the power amp strong enough for LOUD playing. People that use the RV-3 reported that the unit has enough dynamic range at the input to where you can make the amp as loud as you want without overdriving the box. I have never confirmed this though. Gil START NEW THREAD REPLY PREVIOUS LIST Read 255 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/14/2000 9:45 PM Subject: Re: Anybody added reverb to their D'Clone...? Gil: By "tweed mixer" you mean like the pair of 270k resistors that sum up the two channels in a 5F6A bassman? The idea of having self-contained reverb in a modern amp... well, you can do so much more with a decent FX loop! Like patch in a nice plate reverb for sounds that you could never get out of a Fender... --Thanks! Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 241 times From: Daver (bluefire@voyager.net) Date: 10/15/2000 1:19 AM Subject: Re: Anybody added reverb to their D'Clone...? Well, on my Dumblesque combo I used a modified Blackface reverb. The Master volumes are before the reverb circuit. I used a 2M7/20pf combination for the reverb mix/split and left the cathode cap off of the reverb driver cathode (12AT7). It seems to work well for me. The drive in mine is a little more attenuated than most, but even with an overdrive pedal driving the overdrive the reverb sound is great. Just my experience. Daver START NEW THREAD REPLY PREVIOUS LIST Read 233 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/15/2000 6:21 AM Subject: Re: Anybody added reverb to their D'Clone...? Daver: Thanks for your post! With the reverb tap after the master volumes, you are dealing with signal levels even hotter than line level (at least when the amp is cranked up). So the 2M7/20pF goes right into the PI or do you use an extra gain stage to bring the signal level back up? Just wondering... Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 233 times From: Daver (bluefire@voyager.net) Date: 10/15/2000 3:36 PM Subject: Re: Anybody added reverb to their D'Clone...? Steve, The signal goes through a mixing stage just like a Blackface reverb circuit. 1/2 a 12AX7 for reverb recovery and 1/2 for mixing. After the mixing stage there is a .1uf cap from the plate, then a series 220k resistor then a series .022uf feeding the phase inverter. I realize either cap and/or the resistor could be eliminated, but this combo sounded best. If the overdrive is too muddy, dropping the .1uf cap to .047uf or so makes an audible difference. Again, mine uses a little more negative feedback in the preamp, so the signal is probably not as hot as some. It works in this amp, YMMV. Daver START NEW THREAD REPLY PREVIOUS LIST Read 225 times From: JaySG (jaysg@xvb.net) Date: 10/16/2000 1:34 AM Subject: Re: Anybody added reverb to their D'Clone...? "Tweed mixer" could be more like the input to a 5E8-A: Parallel triodes with a common plate resistor and separate cathode RC's. Dry input into one grid, and reverb input on the other. START NEW THREAD REPLY PREVIOUS LIST Read 223 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/16/2000 1:59 AM Subject: Re: Anybody added reverb to their D'Clone...? Jay: Thanks! So the two signals (after the twin triodes) are summed up with a pair of 100k resistors going to the .02uF coupling cap. I was wondering about using a single- or dual-ganged linear pot to blend the two signal... but you'd need to add in blocking caps ahead of the pots to keep DC off the pots. So if you didn't want to add any more gain to your amp, I guess you could wire up the two triodes as cathode followers- right? Might be a fun experiment to try... Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 220 times From: JaySG (jaysg@xvb.net) Date: 10/16/2000 2:21 AM Subject: Re: Anybody added reverb to their D'Clone...? If you want gain, you can use one common plate resistor for both. If you want a mixed cathode follower, I suppose one common cathode resistor would mix the signals. I'm reaching here...oh Randall... START NEW THREAD REPLY PREVIOUS LIST Read 225 times From: Bruce (Missionamp@aol.com) Date: 10/16/2000 4:35 AM Subject: Re: Anybody added reverb to their D'Clone...? I think the dry and wet signal is mixed across the single anode resistor and coupled with a single cap to the next stage, Steve. Kevin O'Conner writes about this in one of his books. Bruce START NEW THREAD REPLY PREVIOUS LIST Read 243 times From: Gil Ayan (ayan@earthlink.net) Date: 10/16/2000 3:58 PM Subject: OD Reverb Architecture Gil: By "tweed mixer" you mean like the pair of 270k resistors that sum up the two channels in a 5F6A bassman? No Steve, not at all. This is what the amp basically looks like: after the preamp volume control, the signal is tapped and fed to a completely separate gain stage. At the output of that stage there is a send control which feeds a parallel tube arrangement (just like Fender's), which is the reverb driver. On the output side, there is a recovery stage, pretty much like Fender's as well. The output of that is fed to a "tweed mixer," which is a two-stage arrangement. The two gain stages have a comon cathode resistor but different plate loads. One side gets the dry signal and the other the wet one. If you have been counting tubes thus far, you will have come up with a grand total of 3 extra tubes for the reverb. Gil START NEW THREAD REPLY PREVIOUS LIST Read 206 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/16/2000 5:17 PM Subject: Re: OD Reverb Architecture Gil: Jay had already pointed out the Twin 5E8-A schematic which uses a "tweed mixer" for the inputs of each channel... So the "different plate loads" would be used to adjust the balance between the Dry and Wet signals... the 5E8-A schematic shows a pair of 100k plate resistors— methinks that you would lower the value of one of them to lower the gain (rather than raise the value to boost the gain)... or do I have that backwards? --Thanks! Steve Ahola P.S. So does Randall have an article explaining how the "tweed mixer" works and how to fine tune it? START NEW THREAD REPLY PREVIOUS LIST Read 257 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/16/2000 5:30 PM Subject: Here is a reverb circuit from Scott Schwartz (Thanks!) Scott sent me this circuit he drew up which looks very interesting. http://www.blueguitar.org/rev_cir.gif Steve Ahola P.S. So is a 6K6GT tube an octal power tube? Could this circuit be revised to use an EL84 (or even a 12AT7 wired up in parallel as in a BF Fender)? START NEW THREAD REPLY PREVIOUS LIST Read 228 times From: Jim S. (jsalman@fiam.net) Date: 10/16/2000 5:42 PM Subject: Re: Here is a reverb circuit from Scott Schwartz (Thanks!) 6K6GT is the reverb driver tube used by the original (no reissue) outboard Fender Reverb unit. It is an octal tube that looks very similar to a 6V6GT. The main differences are a much lower power handling capability (you can't sub them for 6V6s in your DR, for example) and they are true power pentodes; 6K6GT has a suppressor grid instead of beam-forming plates. START NEW THREAD REPLY PREVIOUS LIST Read 226 times From: Jim S. (jsalman@fiam.net) Date: 10/16/2000 5:53 PM Subject: Re: Anybody added reverb to their D'Clone...? I know that both Two Rock and Fuchs have the reverb circuit wired as an integral part of the effects loop in their "Dumblalike" amps. The Fuchs "Overdrive Supreme" has reverb and an FX loop available as separate options, but if you order reverb, it also includes the effects loop. I have no idea what these circuits look like, but I would guess they did it this way to reduce parts count (including tubes) and to reduce the number of gain stages the signal needs to go through if reverb and external effects are being used at the same time. If you think about it, a reverb circuit is very much similar to a parallel effects loop. If an amp already features parallel FX loop capability, then the reverb return circuit can be treated as an additional effects sidechain that gets mixed in to the dry signal. START NEW THREAD REPLY PREVIOUS LIST Read 205 times From: Jim S. (jsalman@fiam.net) Date: 10/16/2000 5:58 PM Subject: Re: Anybody added reverb to their D'Clone...? some people use a BOSS RV-3 pedal in the loop, without anything else, and get good results I forget if I read this on your web site, or on Bill Morgans site, but I found it interesting that an outboard tube Fender Reverb unit (this particular one was a reissue retrofitted with a Hoffman tag board) supposedly works well connected to the non-buffered loop in a D-clone. START NEW THREAD REPLY PREVIOUS LIST Read 197 times From: Graydon Stuckey (graydon@apollo.kettering.edu) Date: 10/17/2000 1:11 PM Subject: Re: Anybody added reverb to their D'Clone...? board) supposedly works well connected to the non-buffered loop in a D-clone. I have tried a number of things in the loop of my D-clone. I have found that most units will load down the signal, and cause the volume to drop, and the tone to go away, as expected. However, if the unit you want to use has some sort of isolation transformer or a circuit similar to the Dumblelator, then you might get away with it. For example, the Lexicon MPX-G2 worked fine taking a signal directly from the D-clone pre-output. However, most of my other effects units such as my Alesis Q2, or a borrowed TSR-12 did not work without the D-lator-clone there to buffer the signal. The unit that works the best (besides my D-lator-clone of course) is the unity-gain input buffer in the Ground Control GCX. This unit is very quiet, and works like a charm. The only downside is that it doesn't add any "tone" to the amp like the D-lator does so well. Sincerely, Graydon Stuckey http://elektro.cmhnet.org/~graydon/ START NEW THREAD REPLY PREVIOUS LIST Read 174 times From: JaySG (jaysg@xvb.net) Date: 10/19/2000 5:51 PM Subject: Re: Anybody added reverb to their D'Clone...? sorry about resurrecting this, however...Steve's inbox is too deep to get his notice. My dumbling is in a BF'd '83 Concert OD channel. Last night I jumpered out my FX loop, Reverb circuit, and mixer in an effort to find out where the high end was getting killed. That was it. The standard Fender topology was lopping off the high end. I have to use the bright switch(250pF) to get about the same high end response. Obviously, it isn't the same result because more highs are being OD'd. The shortest path seemed to "breath" better if that makes any sense. As an aside, the ODS Reverb architecture as explained by Gil, reverberates the clean signal, not the clean _or_ overdrive signal. I'm iffy on the idea. An outboard reverb in the FX loop hits both. Hmm. START NEW THREAD REPLY PREVIOUS LIST Read 178 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/19/2000 7:23 PM Subject: Re: Anybody added reverb to their D'Clone...? Jay: The standard Fender topology was lopping off the high end. I had been tearing my hair out trying to get a decent OD sound from the Vibrato channel of my Pro Reverb project amp— the preamps that sounded great in a 5F6A design came out sounding like a tinny transistor radio version of same: So after inhaling a double shot of solder fumes, this idea came to me: "Why not wire the OD channel up like the Normal channel, bypassing all of the reverb BS and running the signal to the PI directly?" Eureka! The tinniness was gone and the OD channel sounded more like it did in my hotrodded 5F6A... From that moment on I decided to skip reverb for the overdrive channels in my homebrew amps... Now I've heard Marshall and Mega Boogie amps that add reverb to their OD channels and and it seems to work pretty good. But the thought in the back of my mind is this: maybe the amp would sound even better if they weren't running the OD Channel through the reverb splitter circuitry... I like the way that they added reverb in the Matchless Chieftain, by mixing in the reverb signal at the normally grounded PI input... but I'm not sure if that is feasible if you are using NFB and a presence control in your output section. I guess that you could add in the 2 stage tweed mixer ahead of the PI to blend the dry and wet signals. Question on the tweed mixer: could you tap the reverb feed right from the dry input to the tweed mixer? That way the OD signal would be reverberated... The tweed mixer would add another stage of gain ahead of the PI... (Can somebody compute the expected gain from the 5E8-A mixer circuit, both with a 12AY7 and a 12AX7???) One thought that just occurred to me would be to replace the 3rd stage in the Express preamp with the tweed mixer and run that into the PI... --Thanks! Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 177 times From: Ray Ivers (RAGEray@aol.com) Date: 10/19/2000 9:09 PM Subject: Re: Anybody added reverb to their D'Clone...? Steve, I don't think you have to forego reverb in your overdrive channels, just the (IMO) inappropriately-transplanted Fender reverb circuit with the 3.3M or 4.7M dry signal dropping resistor bypassed by a 10 pF cap. As you've found, this is a 'tinfoil conversion' circuit when passing a heavily overdriven signal, and while it is undeniably a part of the Fender blackface reverb-amp clean sound, I personally cannot imagine using it in a channel-switching amp. I feel there are so many other, better ways to implement the reverb mixing function in multi-channel amp designs. Ray START NEW THREAD REPLY PREVIOUS LIST Read 176 times From: JaySG (jaysg@xvb.net) Date: 10/19/2000 9:36 PM Subject: Re: Anybody added reverb to their D'Clone...? "Question on the tweed mixer: could you tap the reverb feed right from the dry input to the tweed mixer?" That's what occurred to me, but I may end up with a phase problem after reverb and effects loop. "maybe the amp would sound even better if they weren't running the OD Channel through the reverb splitter circuitry..." Is the problem caused by running through the Reverb mixer circuit, more of a plate loading issue at the splitter point, or both? With my testing, I didn't have time to narrow down on any specific culprit. START NEW THREAD REPLY PREVIOUS LIST Read 180 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/20/2000 2:12 AM Subject: Re: Anybody added reverb to their D'Clone...? Jay: That's what occurred to me, but I may end up with a phase problem after reverb and effects loop. I'm not sure if you can have phase problems with a signal coming back from a reverb tank... although I always wondered about adding a phase switch to a reverb circuit just to see if it does have an effect. With an FX loop you very well could have a phase problem because an FX patch can have a definite phase to it (unlike the signal from a reverb tank, except as noted above). Is the problem caused by running through the Reverb mixer circuit, more of a plate loading issue at the splitter point, or both? The load on the plate from the reverb signal is not much— on the input side of the splitter it is a 500pF cap going to a 1M grid load resistor. And I think that you can ignore the plate load factor from the other side of the 3M3/10pF splitter (the 220k resistor there plus the 470k resistor and 100k intensity pot constitute the grid load for the following stage). So I think that the culprit is the 3M3/10pF splitter... Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 171 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/20/2000 2:20 AM Subject: Re: Anybody added reverb to their D'Clone...? Ray: I don't think you have to forego reverb in your overdrive channels, just the (IMO) inappropriately-transplanted Fender reverb circuit with the 3.3M or 4.7M dry signal dropping resistor bypassed by a 10 pF cap. Well actually since I was referring to my Pro Reverb project amp, the Fender reverb circuit was "native"— it was the OD channel that was the transplant... I feel there are so many other, better ways to implement the reverb mixing function in multi-channel amp designs. Do tell, do tell! (In fact that is why I started this thread... to get different ideas about adding reverb.) --Thanks! Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 172 times From: Ray Ivers (RAGEray@aol.com) Date: 10/20/2000 6:42 PM Subject: Reverb Ramblings Steve, I see your point about the 'transplant' thing - I sould have read your post a little closer. I was sort of fixating on the 'add reverb to D'clone' thing. It seems to me that reverb is simply a form of side-chain time-delay processing. You tap off the dry signal somewhere, run it thru the tank, amplify it back up, and mix it back in. I feel that for best reverb tone in channel-switching designs, both the reverb initial tap-off point and reverb return should be before the master volume (i.e., at a point of relatively fixed signal level). When using a master tone stack for all channels, I think this stack should be positioned after the reverb return so that the entire 'wet-mix' signal is affected by the tone stack. If there are separate post-distortion tone stacks for each channel, usually I've found the tone controls' changes don't affect the reverb tone much, so that the reverb control becomes sort of an unwanted wide-band midrange tone control in addition to a reverb mix knob. This problem is also apparent when connecting the reverb circuit across a tone stack or an effects loop. I know it's tempting to use the existing attenuations of both these circuits when adding reverb, but I've never really liked the results. As I've mentioned in previous posts, it's possible to add a pretty nice reverb to an amp with only one tube; a 12DW7/7247. The 12AU7 half will drive a standard Fender reverb transformer nicely, and the 12AX7 half makes a good return recovery stage. Another option would be a 9-pin triode/pentode tube, which should give enough gain to boost the tank return signal high enough where it could be mixed in at nearly any signal point. If you have enough reverb return signal, it's not necessary to use any dropping resistance/attenuation, which in my opinion has very real sonic advantages. There are also lots of Accutronics pans, with all sorts of impedances/signal levels/grounding schemes/etc., which gives a lot of flexibility in circuit design. I realize this post is a little vague, but to really design a decent reverb, I'd have to know exactly what circuit was being used, whether or not the existing circuit had to be left 'as-is' or could be optimized for the reverb addition, exisiting extra tube stages (if any) to be used for the reverb circuit... all that stuff. But to sum up; if at all possible, I feel the best place to add reverb is before a post-distortion master tone stack, and also before the master volume control. I also feel that effect loop levels should not vary with master-volume control settings, but I guess just about every amp manufacturer disagrees with me on this one. Ray START NEW THREAD REPLY PREVIOUS LIST Read 166 times From: Steve A. (steve_ahola@yahoo.com) Date: 10/20/2000 7:50 PM Subject: Re: Reverb Ramblings Ray: I agree with you about the "ergonomics" of reverb placement, etc. While I wasn't looking for specific reverb circuits what I was mainly wondering about was the general game plan for adding it to an amp such as the D-ODS... like how to tap the signal going into the tank and how to mix it back into the signal chain. Besides the 3M3/10pF splitter, or using the normally grounded input of a long tailed PI. So what are your thoughts on using at least some ss components in the reverb circuitry? While it is nice to be able to brag about "all-tube construction" I think that a few ic's in the reverb and FX loop signal path would not be the end of the world... especially if used to buffer those FX from the dry signal path (which is presumably all-tube). I do think that there should be a tube in there driving a reverb transformer... the all-SS reverb circuits just don't compare to an old Fender! Also, at what point is it "safe" to run the audio signal through an IC mixer (that is, without losing the "tubularity" of the sound)? When it is up to line levels in the vicinity the PI? Or never? At some point it seems like the signal will have acquired enough "tubularity" that it will sound like a tube amp even when recorded and played back on ss equipment. If we can agree on that then we should be able to backtrack through the signal path to some extent and add SS circuitry without ruining the overall sound... Just an idea! --Thanks! Steve Ahola START NEW THREAD REPLY PREVIOUS LIST Read 164 times From: Matthew Springer (mspringer@comtier.com) Date: 10/20/2000 9:47 PM Subject: Paging Andy Fuchs... Andy, Any interest in chiming in as the guy who has actually added reverb to high drive amps. You must have run into this problem yourself. No, I'm not asking for any trade secrets, but what is your general approach. Inquiring minds want to know. -Matthew START NEW THREAD REPLY PREVIOUS LIST Read 165 times From: Ray Ivers (RAGEray@aol.com) Date: 10/20/2000 10:18 PM Subject: Re: Reverb Ramblings Steve, If it were me, I would add the reverb tube(s) and circuit right at the input to the PI, along with a 'master master' following the mixing point, which would probably help with reducing noise a bit. I have no problems at all with SS stuff, used judiciously. The main thing I use tubes for is transitional (clean to dirty) distortion; if a circuit is not distorting, it's fair game in my book for a solid-state device providing the end product sounds good. The exception for me is the power amp - I like the damping and high-frequency performance of a no-negative-feedback tube pentode or UL output stage, and I've only heard one SS output stage that did a credible job with both (the Vanous). For those building amps, of course, there are marketing considerations for choosing all-tube/point-to-point/Class A/etc. constructions that may outweigh other concerns. As far as IC's go, it's true that there are a lot of active devices in the signal chain, but the matched nature of these devices and the near-zero phase shift of DC-coupling, along with a completely-balanced signal path... let's face it, IC's are a fairly high-performance analog circuit design, nearly impossible to reliably implement using tubes. If you're going to run your audio signal through a friggin' spring, I feel it's kind of nit-picky to worry too much about the active devices involved, you know? The reason that a lot of IC and SS circuits 'don't compare' is that they're not done right; you see 741's used as current-drivers or running into a 600 ohm reverb drive transducer, instead of using a 2-watt power IC or small push-pull SS power stage to drive a 10 ohm pan, stuff like that. I personally feel that it's very appropriate to use an FET cascode or SRPP input circuit for a clean channel, and also a cool idea to use a high-voltage FET for the first gain stage of a crunch and/or lead channel; this stage usually doesn't distort at all with most pickups, and the near-elimination of microphonic problems and heater hum and thermal noise are all very good things. And I'm NOT going against practically every famous and smokin' guitarist that ever lived and saying that SS is no good for distortion - I believe a mix of tube and SS distortion is the ultimate. It makes for some complication in the power supply, but the end result is worth it, I feel. I'm also not really talking about 'minimalist' circuits such as the 5F6A; although I still feel this circuit could benefit from an FET first stage for the reasons stated above, I can understand why an all-tube signal path might be chosen instead. But when you start adding reverb/effects loops/channel-switching/multi EQ/etc., an all-tube signal path becomes more and more difficult to achieve, and in my opinion, a less and less desirable design restriction. In a master-volume design, I think at some point in the amp's signal path you have to say, "Hey, here's my sound - all the circuitry following this point exists mainly to make this sound louder". Otherwise, the power amp gets included in the overdrive equation, and you're back to semi-non-master operation Anyway, enough out of me. You get me started on this tube/SS thing, Steve, everybody has to suffer. Ray START NEW THREAD REPLY PREVIOUS LIST Read 133 times From: Marco (pancaldi@supersonica.it) Date: 10/23/2000 1:47 PM Subject: Re: Reverb Ramblings Ray, your ideas about reverb placement are very clear, but "a point of relatively fixed signal level" is not simple to find, for example, in a SLO 100 circuit. If you tap the reverb send after the lead and clean channel masters you can have a near-constant (about 6 dB max. variation) signal level to work. Before the master the range is very variable, due to gain values (I love a very clear AND a very distorted setting all the time for the two channels). I don't understand you on this point: the "midrangish" effect from reverb level is a risk in this case (when you tap the reverb post-tone stack and master)? If you cut heavily the mids, for example, your reverb feed is mid-reduced and the reverb return is then pre-EQd (the springs aren't really linear, but...). This is the same principle of post-send (effect send) on a mixer. A bonus effect: with the post-EQ tap the reverb circuit (tubes, tranny, springs) works only on frequencies you use. But I feel you have another idea about. Can you explain a little better for me? Thanks m. START NEW THREAD REPLY PREVIOUS LIST Read 131 times From: Ray Ivers (RAGEray@aol.com) Date: 10/23/2000 8:14 PM Subject: Re: Reverb Ramblings Marco, I feel an almost-ideal point exists to install reverb in the SLO 100 circuit; between the effects loop return and V4's input. The effects loop has been attenuated to usable levels, so you would not have to boost the tank return signal up too high to compete with the previous signal level going into V4a's grid. And the volume level here does not change too much (obviously, the instantaneous volume level varies all over the place as you play; I mean the 'ballpark' loudness setting). I would think that any post-master reverb tap level would (obviously) vary with the setting of the lead and clean master controls. With the way I play my amps, I can tell you that would be a lot more than a 6 dB variation - more like 60 dB. If you always play your amp at a similar level, this may be less of a problem, but I still would not advise designing a reverb circuit this way, with a master-volume-variable 'dwell' (Fender's term). You might well get very little reverb at low volumes, and possible reverb-driver overload and 'spring crash' at high master settings. A spring reverb is very much a bandpass-filter type of circuit, mainly due to the springs but also to a lesser extent by the electronics (although sometimes an effort is made to widen overall bandwidth by boosting high-end lost in the spring system). You can pre-EQ going into the springs (sometimes a bass-cut is used to reduce muddiness and a treble-cut is used to minimize 'boing'), but I wouldn't expect to hear all that much change in tone at the tank output, especially if the pre-tank EQ change involved deep bass or high treble. If you cut the mids, yes, you will hear that at the output of the tank, but not quite like you would hear it if you did the mid cut post-tank. I'm not sure about the 'bonus effect' you mentioned. I've just found that when the reverb signal is mixed with the straight signal and then EQ'd, I like the resulting sound better. Ray START NEW THREAD REPLY PREVIOUS LIST Read 125 times From: Carl Z (summit@theramp.net) Date: 10/23/2000 10:42 PM Subject: Re: Here is a reverb circuit from Scott Schwartz (Thanks!) Steve; Looks like an interesting circuit. I tried something similar for an effects loop and had big problems with the cathodyne stage. I had serious balance problems when the load off the plate was different than the load off the cathode. Maybe it wouldn't be so severe with an AU7 as it's got a much lower output impedance. Carl Z START NEW THREAD REPLY PREVIOUS LIST Read 115 times From: Marco (pancaldi@supersonica.it) Date: 10/25/2000 2:21 PM Subject: Re: Reverb Ramblings (long and boring) Ray, now your idea is perfectly clear. The problems from the "master-volume-variable 'dwell'" are real but, as I understand right, the classic Fender reverb amps are all built with this design. The Fender idea is: you set the reverb return with the pot, period. When you raise the amp loudness, you send more to springs, you hear more return. The dry/level ratio is quasi-constant, but the springs drive level is VERY variable. Now, I have a Yamaha T100, quasi-SLO clone, and the reverb circuit is factory built-in very close to your idea. The problems are: too much drive on the springs when you use the lead channel (I hear the springs acoustically "scream" in my room when the amp is zeroed) respect to clean (a good idea about attenuation circuit is not simple: it depends from variable preamp levels). Because the master levels are very low for dist channel and way open for clean, and the rev returns are BEFORE the masters, if I play and immediatly I switch the channel from dist to clean I hear a BOOM from the springs return (the drive was high with a low return, now the return is very high...). Sorry for the long story: now I'm searching for a circuit with the returns after the master, to remove the switching problem. The Mesa Tremoverb is a sort of hybrid "dual channel-SLO style with fender type reverb", but I think the 3M3/10pF network is not good for the SLO tone. Can be an option to simply insert a (about) 100K res before the PI and use it as send/return for reverb (raising the reverb circuit resistors values to control the "reverse circuit" problems)? Another issue is to use the PI in-phase input, but I don't know if this is compatible with the neg. feedback-pres-/reson. controls. Any other suggestion is welcome, of course. Thanks in advance m. P.S. about your intresting ideas about mixing tubes and SS: I've found a very intresting article about ic drived spring reverb (constant current circuit) at http://members.tripod.com/~roymal/reverb.htm What you think about? START NEW THREAD REPLY PREVIOUS LIST Read 109 times From: Ray Ivers (RAGEray@aol.com) Date: 10/25/2000 4:12 PM Subject: Re: Reverb Ramblings (long and boring) Marco, The 'boom' problem seems to me to be due to noisy switching, not the circuit topology; if you put the reverb after the master, it may be even noisier than it is now, since there is no master volume control downstream to attenuate the 'boom'. There may also be less gain stages, though, too. I really am not familiar with the T100 circuit. I wouldn't be too concerned about the reverb 'spring scream'; does the reverb sound OK? As far as the questions about adding reverb at the PI and the PI grounded-grid return point, I've never done this so I can't really comment on it. I would think that both phase shift and feedback loop issues would affect such an installation, though. Ray START NEW THREAD REPLY PREVIOUS LIST Read 108 times From: Jim S. (jsalman@fiam.net) Date: 10/25/2000 4:15 PM Subject: Re: Anybody added reverb to their D'Clone...? Have you looked at the schematics for the Mesa/Boogie Mark IIC+ and Mark III amps? These might be helpful. I know the reverb comes before the effects loop; I don't remember where the rhythm and lead masters are placed in these circuits. I think these amps use a much smaller mix resistor (which is unbypassed) than the Fender 3M3 value. The reverb sound is not quite on par with Fenders, but is still reasonably good. START NEW THREAD REPLY PREVIOUS LIST Read 127 times From: Gil Ayan (ayan@earthlink.net) Date: 10/25/2000 5:30 PM Subject: Re: Anybody added reverb to their D'Clone...? Have you looked at the schematics for the Mesa/Boogie Mark IIC+ and Mark III amps? These might be helpful. I know the reverb comes before the effects loop; I don't remember where the rhythm and lead masters are placed in these circuits. I think these amps use a much smaller mix resistor (which is unbypassed) than the Fender 3M3 value. The reverb sound is not quite on par with Fenders, but is still reasonably good. Jim, yes, Boogies use the 2.2Meg 20pF deal (variation of the Fender design), but that comes before the overdrive section and before the reverb. So the circuit is completely different all together, and npt what Steve Ahola was referring to originally. His idea wwas to, after the typical Dumble circuit (whether it be in overdrive or clean mode), to use the 3.3Meg/10pF deal as a reverb mixer. He reported pretty bad results, and I kind of agree. However, I had toyed with that idea a couple of years ago, and the "workaroun"d" was to severly modify the output of the Dumble's overdrive section so as to avoid harnshnesses from developing at the reverb mixer resistor/cap network. I think I got the amp to sound great that way. One of these days I will look for my schematic of that and share it with you guys. Gil START NEW THREAD REPLY PREVIOUS LIST Read 110 times From: Jim S. (jsalman@fiam.net) Date: 10/25/2000 8:54 PM Subject: Re: Anybody added reverb to their D'Clone...? Jim, yes, Boogies use the 2.2Meg 20pF deal (variation of the Fender design), but that comes before the overdrive section and before the reverb Gil, That's not the part of the circuit I was referring to. I seem to remember that the 2M2/20p combo was used mainly for shaping the tone of the rhythm mode; I know it was not used for reverb mixing in Mark IIC and Mark III amps. (In the Mark IIA and IIB series, that network was used to isolate the output of the 3rd stage overdrive section from the output of the 2nd post-EQ stage. The reverb was fed from the clean 2nd stage signal, whether or not lead mode was engaged.) But in the Mark IIC and III, there IS an unbypassed isolation resistor used to prevent the reverb output signal from feeding back into the reverb send. I think its value is somewhere in the 220K to 470K range, or something like that. I just thought this reverb circuit might be a good starting point for implementing a reverb that is fed by a signal where all the EQing and channel switching and overdrive has already occurred. If you look at the schematics you'll see what I mean. START NEW THREAD REPLY PREVIOUS LIST Read 73 times From: Gary J (gary_justus@excite.com) Date: 10/29/2000 9:44 PM Subject: Re: Anybody added reverb to their D'Clone...? Jim, I agree that Mesa had a good idea about where to place the reverb in a channel switching amp.. I bought a MK IIB and converted it to a C+. I like the reverb sound of it MUCH better than any Fender I've ever played through. (This is my own opinion and I'm sure there are many others that may disagree since "Tone" is very subjective). I think the Fender's I used had the 4 springs and also had a more high end "Boing" than the MK IIC+. I think the main difference was the 6 spring reverb tank the C+ used. The reverb in the MK IIC+ circuit has a 150K resistor to isolate the reverb send from the return. It uses 1 12AX7 for both reverb stages. The reverb send is placed at the same point as the lead master, so if the lead channel and clean channel are both set so that the amp is the same volume in both modes, you get the same amount of reverb sent in both cases. In this setup, during the lead mode, the distorted signal is fed to the reverb circuit instead of feeding clean sound to the reverb and trying to mix the clean reverb with the lead channel distortion. With my limited experience, I liked the reverb circuit placed "After" the lead master so the reverb was about the same level in both modes. If you want less reverb during the lead mode, you could always put a relay to lift the cathode bypass cap on the reverb recovery tube at the same time the lead mode is switched in. (I know... Opinions are like assholes... Everyone's got one and most of them stink.) please, no flames on my opinion just because I like Boogies in addition to Fenders. START NEW THREAD REPLY PREVIOUS LIST Read 60 times From: Marco (pancaldi@supersonica.it) Date: 10/30/2000 11:14 AM Subject: Re: Anybody added reverb to their D'Clone...? The "Boogie" option is very intresting. I'll try to insert a 150K res before the PI and use it for reverb tap/return. A possible option is to convert the two return levels in my T100 to have a drive/dwell and a single global rev return level. Tanks to Ray, Jim, Gary and all for suggestions and ideas. m.