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Post by dougwendal on Feb 6, 2021 5:00:35 GMT -6
Great CA-70 info thehightenor.
I know what mean, I have a CA-70S and want to add a CA-286S.
I recommend experimenting with running your solid state pre-amps into the CA-70s. It doesn't always work, but sometimes it's great.
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Post by thehightenor on Feb 6, 2021 5:47:16 GMT -6
Great CA-70 info thehightenor. I know what mean, I have a CA-70S and want to add a CA-286S. I recommend experimenting with running your solid state pre-amps into the CA-70s. It doesn't always work, but sometimes it's great. Doug, I still have the chance to switch to the PS6 rack and start with a CA-70 module instead of the stand alone and then add a 286 module. I'm balanced between the pro's and con's Pros, I get the extra Hi Frequency roll off knob (at the top of the modules) for the NF circuit (not included on the stand alone) and the ability to swop out transformers - though I have no idea how valuable that is. Con's - over and above the extra cost, I'm concerned that the modules are individually switchable and when I'm using the CA70 for an all day vocal tracking session the 286 is just sat their cooking away but doing nothing. Unless those Mod 1-3 Mod 4-6 switches on the PS6 allow you to turn off the modules in banks of three - it isn't clear on the Coil website if that's how it works with the PS6. Currently I'm only tracking one source at a time - unfortunately I have no space for real drums or piano -so probably the rack is a bit OTT I'm just stuck between the pro's and con's list. I'm so taken with the CA-70 I've got serious GAS for the 286!
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Post by adamjbrass on Feb 6, 2021 7:12:12 GMT -6
I’ve used them all quite a bit. The M72 is much softer sounding then either, and it has a really full sound, but far more polite sounding overall. It only gets kinda “squashed” when signal is pummeling it. Very deep low end and gives the treble a polish. Things that previously sounded harsh sound creamier.
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Post by thehightenor on Feb 6, 2021 7:36:09 GMT -6
I’ve used them all quite a bit. The M72 is much softer sounding then either, and it has a really full sound, but far more polite sounding overall. It only gets kinda “squashed” when signal is pummeling it. Very deep low end and gives the treble a polish. Things that previously sounded harsh sound creamier. Interesting, though I cannot imagine anything software and creamier than a Coil CA-70 epically with some negative feedback dialled in I'm still going to get a demo of the M72 as the Coil 286 crosses paths with it - with them both being EF86 based circuit topology. I always hear people saying the EF86 based pre's have an edgier rock and roll mid forward tone - but your feeback is somewhat the opposite - which I find intriguing.
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Post by Coil Audio on Feb 9, 2021 0:19:19 GMT -6
Hi Everyone. Jim Here from Coil Audio. A friend of mine saw this thread and said it would probably be cool if I popped over here to chime in. I don’t get a chance to hop on here very often, so I figured I’d try and squeeze it all in in one giant long winded breath……. As far as circuit design, we’re using a very simple, two stage, single ended design. Input transformer->tube->cap->tube->cap->output transformer. Western Electric developed it right after they bought the patent for the Audion (1st vacuum tube) from De Forrest in 1912. Between 1913-15 they developed a big pile of what would become the basic form of pretty much every audio circuit, one of which was the two stage single ended east west repeater amp designed for boosting telephone lines from coast to coast. Like Doug mentioned, our CA70 is based on Gates Radio’s 1940-50s version of that circuit as they implemented it in their SA consoles as booster/mic amps. We use big octal tubes, a 6J7 into a 6C5 just like gates did. RCA and Langevin used almost identical circuits, but had a different tube for the output, a 6J7 into a second 6J7. These were the RCA BA11, RCA BA1A, and Langevin 116. The RCA ba11 and Langevin 117 spec out at about 1% distortion at +18 out, depending on the B+ voltage. The RCA BA1A specs at 1% distortion at various B+ voltages. +12 @ 280v, +10 @250v, +8 @180v. The OG gates SA70 is conservatively rated in their docs at 1% distortion at +6.5 with 180V b+, which is how they lived in the SA consoles. We do a bunch of tricks that increase the gain and headroom in our CA70. We hit both tubes with much higher plate voltages, which pushes them more into the sweet spot of their curves. This increases gain, headroom before distortion, and drive capability. We also spent a lot of time on transformer design to maximize the coupling that happens between the transformers and tubes. No poopy zobel networks on the input transformers like most modern stuff. We use variable negative feedback to not only tweak gain and timbre, but to also tweak the drive and reflected impedance of the output stage. Our output transformer was also specifically designed to just start to go into the onset of saturation at around +18, which is right at the top of most modern digital recording devices. Also, we labored over the three input pad positions to really be able to utilize that first stage saturation, a fixed single pad wouldn’t cover it. Now don’t get me wrong, if you cram a square wave into a coil CA70, it will not come out the other end looking like a perfect square wave. But when gently crammed in, that’s when all the yummy harmonics(aka distortion) happen, especially in the low end. A lot of classic preamps are like this, especially the American made stuff. It’s their imperfections, and sometimes “misuse” that we love the sound of. As far as overall all use and sonics, the CA70’s can be very clean, open, and hifi, and can have a huge soundstage. They can also be wooly AF and burly as all get out if you want. The CA70s in particular were voiced to sound like a properly calibrated 2” 16trk at 15ips. When in the stock Low Freq and Neg Feedback setting, they have a built in bump at around 60hz, some subtle saturation, and a gentle softening of the top end without the loss of detail you normally get from tape. Add more NF and you get more of the “Gaussian Blur”/tape effect. When you roll back the negative feedback, you get more harmonics, which add a forward presence to the sound, as well as a gentle hi end slope/boost that starts at about 9K and rises to about 3db up at 20K. They can also have the same instantaneous limiting characteristic of tape when you get the gain staging right. Like Doug mentioned, they can act like a gentle (or not so gentle) limiter. Just like a guitar amp, It’s all how about how you do your gain structure, and how dynamic the player/guitar is. Years ago, before Coil Audio, I drug a big pile of my modified vintage pres out to Sonic Ranch in El Paso for a session. All the house engineers thought I was crazy for not wanting to use their beautiful pile of Neve pres, and were assuming I was trying to make some type of vintage throw back sounding record. They were immediately surprised and impressed with how “loud”, in your face, and intimate everything sounded, like what happens when you compress stuff, but that it was still very dynamic and detailed, and didn’t sound ”compressed” or "vintage". They were looking at my waveforms and asking me what limiter/compressor I was using on the kick and snare, to which I replied, “none, it’s my gain structure”. I showed them how if you reduce the attenuation on the input, and start to pump signal into the first stage, you can get a “transparent-ish” limiting on the transients, much like tape. Set the input wide open and cram the signal into the first stage and you get a cool soft distortion on the transients similar to banging on a tape machine /transformer/limiter/etc. Then I showed them how when you increase the attenuation/padding on the input, and turn up the output, you loose that 1st stage saturation, all the original dynamics come back, and you still had the yummy harmonics and big sound stage from the tubes. Very few solid state preamps react this way, and give such large apparent volume and soundstage by very subtly limiting the dynamic range. See attached short paper “Tubes Versus Transistors- Is There an Audible Difference?” By Russel O. Hamm. It’s a brilliant read, only a few pages long, and only gets heady in parts. Russel worked at Fine Sound NY and was part of the super smart guy lab coat crew with Walter Sear and Bob Moog at Sear Sound in NY.These older, simpler tube circuits like we use at Coil definitely have a small bit of learning curve. It takes a minute to get your head wrapped around how they react with particular mics, on different sources, and with different dynamic ranges. When I started recording more and more to digital 10/15 years ago, switching to all tube pres made it a lot easier for me to not miss the tape machine. I found that I could get better transient control with tube gain staging than I ever could with tape saturation or solid state pres. Plus it sounded better and didn’t crunch the transients unless I wanted it to. I also found I didn’t feel the need to compress as much, and in general, stopped using compression on stuff I had almost always traditionally compressed…Hmmm… Any who, I digress… I’m assuming the mercury and weight tank are both based on the V72 circuit. This is also a two stage, single ended design with some fancy euro power distribution for the B+ due to the enclosed power supply and space considerations. The B+ is choke loaded, which can be a cool thing (think early fender champ power supply variations you guitar guys). Our CA286 is closer sonically and circuit wise to these guys, but without the choke loaded power stuff, and not nearly as much negative feedback (unless you dial it in). However, ours is a little more akin to the Langevin 5116, or a V72a with a few tricks and tweaks added in to make them more useful and dynamic. The smaller noval tubes we use in the CA286, the ef86s, are what give it its sparkly harmonics and saturation, and give it’s own special character when compared to the CA70.
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Post by thehightenor on Feb 9, 2021 3:10:59 GMT -6
I'd like to say I completely understood that amazing explanation.
But what I do understand is you guys at Coil have some serious knowledge and passion!
The CA-70s is the best pre-amp I've ever owned and my audio life will not be complete until I own a Coil CA286s to keep it company.
Between a CA-70 and a CA-286 the tonal possibilities are going to be seemingly endless!
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Post by dreamsambas on Feb 9, 2021 9:13:45 GMT -6
Hi Everyone. Jim Here from Coil Audio. And the award for greatest post of all time goes to.... Seriously, what a great, informative post. Love learning about the origins of tubes and preamplifier circuits. This De Forrest dude seems pretty cool. Check out that tube. I'm curious about the Coil 286 circuit. What preamps is it based on / inspired by? I have some Collins 356a pres (purchased from EMRR/Doug) that I love to death. How similar is the 286? I think there might be a Coil CA70 or two in my future...
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Post by drbill on Feb 9, 2021 10:38:07 GMT -6
Hi Everyone. Jim Here from Coil Audio. Thx Jim!! Nice post!! Loving the CA70S's here along with the usual suspects!
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Post by Coil Audio on Feb 9, 2021 11:55:15 GMT -6
Great CA-70 info thehightenor. I know what mean, I have a CA-70S and want to add a CA-286S. I recommend experimenting with running your solid state pre-amps into the CA-70s. It doesn't always work, but sometimes it's great. Doug, I still have the chance to switch to the PS6 rack and start with a CA-70 module instead of the stand alone and then add a 286 module. I'm balanced between the pro's and con's Pros, I get the extra Hi Frequency roll off knob (at the top of the modules) for the NF circuit (not included on the stand alone) and the ability to swop out transformers - though I have no idea how valuable that is. Con's - over and above the extra cost, I'm concerned that the modules are individually switchable and when I'm using the CA70 for an all day vocal tracking session the 286 is just sat their cooking away but doing nothing. Unless those Mod 1-3 Mod 4-6 switches on the PS6 allow you to turn off the modules in banks of three - it isn't clear on the Coil website if that's how it works with the PS6. Currently I'm only tracking one source at a time - unfortunately I have no space for real drums or piano -so probably the rack is a bit OTT I'm just stuck between the pro's and con's list. I'm so taken with the CA-70 I've got serious GAS for the 286! @hightenor - the "Mod 1-3 and Mod 4-6" switch is for how many modules are in the PS6 rack tray (its a filament regulator for the amount of modules in the rack - to preserve tube life etc). In the scenario you are describing - If you wanted to not power unused modules in the tray you would simply pull out the module an inch or 2 thus removing it from its power/signal connections. Hope that makes sense.
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Post by Coil Audio on Feb 9, 2021 12:56:02 GMT -6
Seriously, what a great, informative post. Love learning about the origins ofI'm curious about the Coil 286 circuit. What preamps is it based on / inspired by? I have some Collins 356a pres (purchased from EMRR/Doug) that I love to death. How similar is the 286? I think there might be a Coil CA70 or two in my future... Thanks for the kind words! The Collins 356a is almost identical to the Langevin 5116, which are both excellent and punchy sounding amplifiers. When I was still mostly recording to 2" 16trk, a rack of 6x 5116s was my go to for drum close mics. Both the 356a and 5116 have a very complex negative feedback circuit using a special separate "tertiary" winding on the output transformer. It was designed to cancel out as much circuit distortion (harmonics) as possible. By adding the output transformer into the NF mix, you not only get the standard cancelation of any tube "distortion" in the circuit, you also cancel out the non-linearities of the output transformer. This is why those amps sound so clean and hifi without a lot of harmonics, and look amazing on the scopes and distortion meters. It's also why they're incredibly tight and punchy for a tube amp. Having that much "full circuit" neg feedback really helps the drive of the output, which gives it that very solid/dense sound like a v72(which also lots of neg feedback). Our CA286 is VERY close to these circuits, but without the tertiary Neg Feedback arrangement like the 356a/5116. Our NF comes from right before the output transformer (same with V72), so you can still get the good output saturation when and if you want it. You can also steer it into a tight output like all of the above with increased NF and get it to sound VERY similar to a V72. Only other real difference is we use EF86s instead of 5879s, which can be a little too clean and hi-fi in my opinion. We love the ef86s, they're electronically identical to the ef804 in the v72. They're loaded with lovely rich harmonics, pretty much the french food of vacuum tubes. Think butter, pork fat, duck confit, etc...
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Post by EmRR on Feb 9, 2021 13:25:51 GMT -6
The 286 is based on the late 50’s-60’s Gates console preamps, no? Made with both 5879’s then ef86’s later. Tiny transformers on the Gates, bigger upgrades on the Coil. Those things needed improving! It was always claimed that EF86's had a noise advantage over 5879's, I can't corroborate that, never had a problem with a 5879 circuit. I put negative feedback gain control in the Collins rack dreamsambas now owns, so they’ll go softer too. groupdiy.com/index.php?topic=66891.0farm5.staticflickr.com/4367/36436009350_092d07318e_b.jpg
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Post by dougwendal on Feb 9, 2021 13:30:26 GMT -6
Seriously, what a great, informative post. Love learning about the origins ofI'm curious about the Coil 286 circuit. What preamps is it based on / inspired by? I have some Collins 356a pres (purchased from EMRR/Doug) that I love to death. How similar is the 286? I think there might be a Coil CA70 or two in my future... Thanks for the kind words! The Collins 356a is almost identical to the Langevin 5116, which are both excellent and punchy sounding amplifiers. When I was still mostly recording to 2" 16trk, a rack of 6x 5116s was my go to for drum close mics. Both the 356a and 5116 have a very complex negative feedback circuit using a special separate "tertiary" winding on the output transformer. It was designed to cancel out as much circuit distortion (harmonics) as possible. By adding the output transformer into the NF mix, you not only get the standard cancelation of any tube "distortion" in the circuit, you also cancel out the non-linearities of the output transformer. This is why those amps sound so clean and hifi without a lot of harmonics, and look amazing on the scopes and distortion meters. It's also why they're incredibly tight and punchy for a tube amp. Having that much "full circuit" neg feedback really helps the drive of the output, which gives it that very solid/dense sound like a v72(which also lots of neg feedback). Our CA286 is VERY close to these circuits, but without the tertiary Neg Feedback arrangement like the 356a/5116. Our NF comes from right before the output transformer (same with V72), so you can still get the good output saturation when and if you want it. You can also steer it into a tight output like all of the above with increased NF and get it to sound VERY similar to a V72. Only other real difference is we use EF86s instead of 5879s, which can be a little too clean and hi-fi in my opinion. We love the ef86s, they're electronically identical to the ef804 in the v72. They're loaded with lovely rich harmonics, pretty much the french food of vacuum tubes. Think butter, pork fat, duck confit, etc... Great info Jim! Thanks for the detailed post.
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Post by Coil Audio on Feb 9, 2021 13:53:51 GMT -6
The 286 is based on the late 50’s-60’s Gates console preamps, no? Made with both 5879’s then ef86’s later. Tiny transformers on the Gates, bigger upgrades on the Coil. Those things needed improving! It was always claimed that EF86's had a noise advantage over 5879's, I can't corroborate that, never had a problem with a 5879 circuit. I put negative feedback gain control in the Collins rack dreamsambas now owns, so they’ll go softer too. Oh Yeah. Those are hot Doug, and WAY cheaper than langevins, and sound just as good in my opinion. My buddy Jack at Texas Treefort racked a bunch of those with the NF tweak also. He called it his "soul knob" mod. We did indeed start with something very similar to those gates booster amps. We initially were going for a 5879 pre that used a combination of elements from the 5117/356, the V72, and the gates unimote era of 50-60s. The gates circuit is what gave us the idea to use the ef86 instead of the 5879. And yeah, those tiny outputs on the gates were pretty poopy. The mic inputs on the other hand were quite good, like an vastly improved utc 0-1(not that they're that great). We actually tracked down the maker of those inputs (and lot of other gates custom transformers), and tried to get them to make them for us again. Unfortunately, they make lighting ballasts now and weren't interested in dealing with audio transformers anymore. We did procure some interesting documents though...
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Post by dreamsambas on Feb 9, 2021 14:01:27 GMT -6
This is why those amps sound so clean and hifi without a lot of harmonics, and look amazing on the scopes and distortion meters. It's also why they're incredibly tight and punchy for a tube amp. Having that much "full circuit" neg feedback really helps the drive of the output, which gives it that very solid/dense sound like a v72(which also lots of neg feedback)... When I was still mostly recording to 2" 16trk, a rack of 6x 5116s was my go to for drum close mics. Thanks for the info! That’s an excellent description of what the circuit sounds like to me. Punchy. Clean. Kind of like a silverface twin versus a tweed. Also very cool to hear too about the real studio experience that led you to bring back these preamps.
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Post by thehightenor on Feb 9, 2021 15:56:37 GMT -6
Doug, I still have the chance to switch to the PS6 rack and start with a CA-70 module instead of the stand alone and then add a 286 module. I'm balanced between the pro's and con's Pros, I get the extra Hi Frequency roll off knob (at the top of the modules) for the NF circuit (not included on the stand alone) and the ability to swop out transformers - though I have no idea how valuable that is. Con's - over and above the extra cost, I'm concerned that the modules are individually switchable and when I'm using the CA70 for an all day vocal tracking session the 286 is just sat their cooking away but doing nothing. Unless those Mod 1-3 Mod 4-6 switches on the PS6 allow you to turn off the modules in banks of three - it isn't clear on the Coil website if that's how it works with the PS6. Currently I'm only tracking one source at a time - unfortunately I have no space for real drums or piano -so probably the rack is a bit OTT I'm just stuck between the pro's and con's list. I'm so taken with the CA-70 I've got serious GAS for the 286! @hightenor - the "Mod 1-3 and Mod 4-6" switch is for how many modules are in the PS6 rack tray (its a filament regulator for the amount of modules in the rack - to preserve tube life etc). In the scenario you are describing - If you wanted to not power unused modules in the tray you would simply pull out the module an inch or 2 thus removing it from its power/signal connections. Hope that makes sense. Thanks for that info. In the end I went for a stand alone CA-70s and I'll add a CA-286s hopefully by the summer.
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Post by srb on Feb 27, 2021 18:30:40 GMT -6
Can anyone tell me if the Coil CA70S has a vented bottom chassis plate?
I'm having to leave some space in my 'vocal' sidecar for it...the unit probably won't be here for another month...so, if it's vented on the bottom or not, will influence where I put it in the rack.
If it doesn't run too terribly hot, maybe it actually won't matter as much. Heat still remains equipment's insidious enemy...
Thanks!
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Post by dougwendal on Feb 27, 2021 19:15:32 GMT -6
Can anyone tell me if the Coil CA70S has a vented bottom chassis plate? I'm having to leave some space in my 'vocal' sidecar for it...the unit probably won't be here for another month...so, if it's vented on the bottom or not, will influence where I put it in the rack. If it doesn't run too terribly hot, maybe it actually won't matter as much. Heat still remains equipment's insidious enemy... Thanks! The bottom doesn't have a vented plate. I haven't noticed any heat issues, but I have open rack space above and below it.
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Post by EmRR on Feb 27, 2021 19:30:02 GMT -6
Shouldn't run too hot, what does the online manual recommend? I can put my hand on the tubes in original Gates SA-70's and pull them the second they power off, no problem.
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Post by srb on Feb 27, 2021 21:27:52 GMT -6
Can anyone tell me if the Coil CA70S has a vented bottom chassis plate? I'm having to leave some space in my 'vocal' sidecar for it...the unit probably won't be here for another month...so, if it's vented on the bottom or not, will influence where I put it in the rack. If it doesn't run too terribly hot, maybe it actually won't matter as much. Heat still remains equipment's insidious enemy... Thanks! The bottom doesn't have a vented plate. I haven't noticed any heat issues, but I have open rack space above and below it. Thanks, Doug. I'm going to have an open space above (as it stands now), so that's ok. I was going to have a Locomotive WT-72 below it, no space between. Back is open, though. So that will help some with cooling. Wish I had just one more space available, though. I really need to check the operating temp on the WT-72 just to be on the safe side. I was thinking if the Coil was open on the bottom,too, that would allow more consistent flow.
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Post by srb on Feb 27, 2021 21:37:45 GMT -6
Shouldn't run too hot, what does the online manual recommend? I can put my hand on the tubes in original Gates SA-70's and pull them the second they power off, no problem. That's good to know. Could be the deciding factor right there. Thanks, Doug. As it turns out, there is no manual per se for the single channel model on their website. I really need to fire the piece up that would be under it (Locomotive WT-72) to see how it's going to behave. Just now pulling this new rack of stuff together, so still some arrangement questions. I may wind up having to swap positions on these last two pieces. I'll get it figured out, I reckon. Just want to do right by the new tools. The Coil chassis may be deeper, so that may figure in here, too.
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Post by daniel on Dec 13, 2021 12:25:24 GMT -6
Hi!,
Has anyone compared COIL CA70 to Locomotive WT-72?.
Best regards, Daniel.
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Post by drbill on Dec 13, 2021 14:34:23 GMT -6
Hi!, Has anyone compared COIL CA70 to Locomotive WT-72?. Best regards, Daniel. Yes. Very different sounding units.
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Post by plinker on Dec 13, 2021 20:43:25 GMT -6
Hi!, Has anyone compared COIL CA70 to Locomotive WT-72?. Best regards, Daniel. Check Dr. Bill's first post on the first page -- he gives a good comparison of them.
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Post by daniel on Dec 13, 2021 23:49:58 GMT -6
OK, thank you!
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Post by bricejchandler on Dec 14, 2021 3:17:05 GMT -6
Hi!, Has anyone compared COIL CA70 to Locomotive WT-72?. Best regards, Daniel. I have! I just tried the 72 this week end. I have the Coils. The 72 is brighter, faster. It has a very noticeable upper mid bump that gives sources a nice tube sheen and it's a little more in your face, it's not a thick preamp. The freq response reminded me of what a Daking would sound like if it were a tube preamp. It's definitely about as different from the Coil as can be. It piqued my interest and I may get one in the future. What it isn't is a V72. I use V72s ( and V76s ) all the time and the WT is quite a bit brighter compared to the 72 and doesn't have the thick mids. The Mercury I used to own is closer to the V sound, but still not quite there. The Coils are definitely not voiced for ultra modern synth based productions. The WT would fit much better. One thing I'll add is that I don't find the Coils to be that vintagey sounding if gain staged right. They can sound very open. I've noticed on forums that people associate Hifi with brighter, I don't really hear things that way and the CA70 circuit captures sounds in a way that sounds much closer to what my ear hears when I'm standing in the middle of the room with the instruments.
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