Become a Creator today!Start creating today - Share your story with the world!
Start for free
00:00:00
00:00:01
Episode 17: Single-Ended Amps and Non-Musical Noises
268 Plays1 month ago
Charles talks about a quick trip to South Korea. Chris talks about fixing a unique piece of gear. Bryan wonders if there are any great-sounding spring reverb units from a specific country. The three take calls about single-ended amplifiers and non-musical noises.
If you'd like Bryan, Charles, and Chris to answer your question on an episode of Amplified Nonsense, call (513) 334-3803 and leave a voicemail.
Recommended
Transcript
Podcast Introduction
00:00:08
Speaker
Welcome to Amplified Nonsense, a podcast that is largely about amplifiers, but is also driven by your random voicemail questions. Your hosts are Charles Henry of Silktone, Chris Benson of Benson Amps, and Brian Sowers of Sour Sound Transformers.
Listener Interaction Instructions
00:00:22
Speaker
I'm Emily, I'm the producer of this podcast, and before I get too far into the episode, you can call into 3 3 4 3 8 0 3 and leave your own voicemail questions for our hosts. That's 5 1 3 3 3 4 3 8 0 3. How are you all doing
Personal Updates
00:00:39
Speaker
this week?
00:00:39
Speaker
Pretty good. I'm feeling great. I haven't drank for like seven days, so I'm feeling real good. I'm glad you took our intervention to heart. Yeah, yeah, totally did. I thought you were going to fight it a lot more. It's so easy to drink out here because it's like at any time of the night, I can go to next door and just get like a dollar beer and everyone drinks and goes to bars and it's so much fun. So I love doing it, but I told myself like, ah okay, I got stop for a while. I got to focus on work and do all this. shit And I actually stopped and didn't realize how i so until it had been like a week. And I'm like, oh damn, I actually feel good now.
00:01:15
Speaker
They have dollar beers in Sacramento. I don't think they sell beer in Sacramento. Isn't it? It's in Tri-County. Aren't you in Sacramento? Can't you go to the store and get a beer? I walk right now. Oh yeah. It's a new week.
Travel Experiences in Asia
00:01:29
Speaker
Where are you this week, Charles? Dude, you actually, we, we missed me last week in South Korea. So I'm, I'm actually back in Japan. Oh, you're in Japan. Oh, I had no idea. None whatsoever. Shut up.
00:01:47
Speaker
South Korea was wild though. Have you guys been to Seoul? I mean, I have Seoul. Do you? No. I've been to my own Seoul. You've searched for a Seoul. I searched for it and I found it. it Wasn't that your your your initial review of Soursound Transformers? was like, love the product, but but the soulless man behind it is a troll or something like that. oh Dude, if I could still find that...
00:02:13
Speaker
Oh, man. Yeah, it's pretty funny. Yeah, so it was interesting. It actually reminded me a lot more of Los Angeles than an Asian country that I was expecting. It seemed like it was built for cars more than people just like total opposite of Tokyo here where everyone's walking and stuff. Or maybe it's just the area I was in. But like six lane streets with cars everywhere. Hardly any people. Everything is brand new. was a beautiful city, like so many cool buildings. And so you went to Florida.
00:02:43
Speaker
wendy Pretty much, it looked like I was in downtown Los Angeles. Like it was really interesting. It was like I was in downtown Los Angeles, but everyone was Korean and I couldn't understand anything.
00:02:55
Speaker
this It was really interesting. me Dude, there were like, there were Five Guys burgers and Subways everywhere. And like, I was like, where the f*** am I? That's awful. It was really weird. Did Subway sell like kimchi on the subs and stuff? Yeah. Or was it just straight up like a, you know, pizza, pizza sub? No, they did. They all have these unique, like out here, they have the Shilgun Burger at McDonald's where it's like two patties and ah and an onion ring or something. Yeah, it was weird. So like you're in the downtown area and it looks gorgeous and brand new. And then you walk down an alley and it's like everyone's smoking, crammed in. Every alley we would walk down, it was like the same type of food shop. There were like eight hot pot restaurants, like all next to each other. But there was this one that like 40 people were lined up for. So we were like, oh, I guess. Did you wait in the line? We did. Yeah. It took like 20 minutes and there were three floors and they stuck us on the third floor, which apparently was the foreigner floor. It was like two white people, me and i don't know if it was an American too far away. And then the rest were just all Japanese. And Mayu was like, what the hell? Why is everyone speaking Japanese up here? So it was just like, oh yeah, okay, that's the the Japanese tourist floor. you Remember that episode of Curb Your Enthusiasm when he gets seated in the ugly part of the restaurant? It was kind of like that. It's It's all...
00:04:19
Speaker
That was funny. Man, they dogged you. Are you going to take that? Yeah.
Amplifier Repair Challenges
00:04:23
Speaker
ah It was good, though. It was like a whole ass boiled chicken. And they come and cut it up for you and boil it. And then you put in whatever toppings. And it was like, I don't know, 15 bucks or something for the for the whole thing. Anyway, what have you guys been up to? Just farting around.
00:04:39
Speaker
Farting around?
00:04:42
Speaker
Just, you know, farting around with work. So much work. So much to do. Yeah, finally got over the Babylon and Redland releases and can actually do work now, which is really nice.
00:04:55
Speaker
Oh, yeah. Like back to developing stuff and fixing stuff for buddies and the good stuff, the stuff that I like. That's cool. I don't like fixing stuff anymore. I really enjoy it. Just a change from what you normally do. Yeah. No, I mean, I just like fixing stuff in general.
00:05:11
Speaker
I just like actually fixing stuff. So what's the what's the weirdest thing that you've been working on lately for a repair job? I've been working on this like Marshall, they call it a Marshall Fuzz Echo, which is a spring reverb and a fuzz in one head that looks like a really cool you know Marshall head from the late 60s, I believe. And it's basically got like a Marshall Super Fuzz for the fuzz. It's like a three transistor Mark II tonebender kind of thing. Oh, sweet. And then the reverb is germanium transistor reverb that looks like it was... I had to trace the whole thing, there's no schematics. So i actually had to like make a schematic before even did anything.
00:05:50
Speaker
And then once I saw the circuit, I started laughing. This is the one you sent me, right? Yeah, it looked like ah a fuzz pedal designer designed a reverb pedal. Or a reverb circuit. Yeah. The one with base voltage on the reverb output transformer. or There's just so much. Oh my god. They could have got someone who is like an engineer to easily make it, but I think they just tapped like the youngest fuzz puddle obsessed burnout at the Marshall shop. Yeah.
00:06:22
Speaker
And then I put it together and it's just like, it is heinous. It does make reverb now. I had to repair the tank and stuff um and replace a bunch of like caps that were short or open. It oscillated like crazy. They sound like the signal through the foot switch cord, which was unshielded.
00:06:39
Speaker
Like all the fuzz went, they sent it from the head to the foot switch back to the head in an unshielded cable and it was signal. Jeez. Which is, so of course it was like howling with oscillation once I got everything else working. So I i installed like a relay switch.
00:06:57
Speaker
on the inside to bypass all that nonsense. Do you think it was stable back in the day when they were using all those high capacitance coil cables and stuff? No, because it's this it's the original cable.
00:07:07
Speaker
No, I meant going into it. Oh, no, it wasn't like unstable from the guitar side at all. Oh, okay, on the output side. It was just the ah the fuzz was self-oscillating all by itself without any help.
00:07:22
Speaker
Do you know what year this thing
Amplifier Design Deep Dive
00:07:24
Speaker
was? I think it was 1969. Cool. but so you're next Like, hey, kid, you like Hendrix? Put this together. That's exactly what it was. It's like, oh, Jimi Hendrix, he uses fuzz and reverb and he's getting pretty big. Obviously, there's a reason they didn't make a lot of them and they've been forgotten by history.
00:07:45
Speaker
What did it sound like if you had to compare it to something? Well, you know, the Marshall Superfuzz side of it sounds great. Yeah, course. Once they got that to stop oscillating, it's got all the right, you know, vintage components, like...
00:07:59
Speaker
the OC71 transistors and the the blue electrolytics, and all of those were good. Man, the fuzz sound is is awesome at the right temperature. And then the reverb was designed by crazy person, and i don't think it ever sounded awesome, but it sounds like the way you're a spring reverb tank sounds when you're driving around in your car and there's an amp in the back.
00:08:27
Speaker
i know that sound damn it's it's like an acoustic reverb tech oh that's annoying i mean has it was there ever any good british reverbs i mean like vintage like i've i've tried to think about this i've never heard one Yeah, because, you know, Vox did their add-on reverbs. And then, I mean, there was like the AC-10 SRT reverb, which I think that was an American amp, actually. But you mean standalone or like in any amp?
00:08:56
Speaker
Well, Vox did add-on reverbs for AC-30s. Is that the one they use for dub reggae? Like, what is it? Oh, yeah, Grampian. Yeah, okay, good call. Yeah, Grampian. That's supposed to be a great reverb. Yeah, those are fantastic, and they are germanium as well. They do not have DC current on the output transformer secondary of the reverb tank, though. Not like your Marshall. But, ah yeah, Grampians are awesome. Make a great fuzz box, but they're also just a cool-sounding reverb. Good call, because i was I was convinced there wasn't any good British reverb tanks. but that's the one That's the one that I can think of. Yeah, exactly.
00:09:32
Speaker
like the reverb in the AC30, not the add-on, but just the when they have reverb in them. What year? Grid reverb. Oh, it's probably, and i don't know. When did they start adding reverb?
00:09:45
Speaker
Reissue. Reissue CC2 or something. Really? Yeah, the original's never had reverb. our Originals don't have reverb? Am I tripping? Yeah, you are. I guess I am true. It's all that kimchi, man. I know. Hot air. worry Isn't there like a little Vox that has reverb, like the AC-10? Well, there's AC-10 SRT, but like I said, that's the dug at Doug and Pat one.
00:10:06
Speaker
Right. That's Doug's amp, which, well, his reverb doesn't work, I know, because I rebuilt that amp, and we we took we took out the reverb, because that's the one where the reverb tanks use those. They're like phono cartridges.
00:10:17
Speaker
yeah they wired a spring into so it's literally a record player cartridge vibrating a spring it's so ridiculous yeah i was surprised at this marshall tank because it actually had a legit like accutronix style um it wasn't an accutronix tanker doesn't look like it but it looked like it had active elements from an accutronix wedged into a piece of bent metal that it looked like someone hammered with a brick so So it was a Zildjian reverb tank. Yeah. Yeah.
00:10:45
Speaker
Reverb by Zildjian. That's awesome. Reverb by Zildjian probably sounds really good. But yeah, like I said, ah the the Vox reverb, the add-on ones, they were, ooh, this is not good. it was They did it on the AC30s like they did the the top boost.
00:11:02
Speaker
So it was like a cutout in the back panel. And then they just like slapped this this little... I mean, literally slapped together circuit on a piece of bent metal and stuck it into the back panel.
00:11:15
Speaker
Yep. i've i've so I've heard them, and they're not good. Nope. Mm-mm. Reverb? I mean, reverb's hard. Yeah. Reverb is hard. Yeah. But then again, i mean, most of the American amps that had reverb, the reverb was pretty cool. I mean, some of the Gibson reverb...
00:11:32
Speaker
it's hit or miss when it hits i think it's an incredible ampeg reverb like the v series recovery amp in the reverb circuit i love the way that sounds i love apeg stuff that was a big inspiration for the first tall bird actually was it is capacitor coupled yeah tall bird yep okay i think the gemini 2 has some of the best like trim and reverb i've i've heard still that's that's another cap coupled one yeah cap coupled similar recovery circuit Yeah, CG7 to drive the tank is really cool. those are Yeah, they drive the cathode of the ah of the driver, from what I remember. It's cathode-driven. Like, the the coupling.
00:12:11
Speaker
the The dry path is is capul is ah coupled to a cathode. It's the only place I've ever seen it. Wait, what? it Say it again? In the Reverberocket, the actually signal is driven to a cathode. Like, the dry signal. To the cathode. Like, instead of a grid, it's a cathode.
00:12:28
Speaker
ah I'll try to find it. I'll put it in the chat. Are we ready for a question? Oh, yeah.
00:12:37
Speaker
What's up, guys? Your number is now saved in my phone, in my contacts.
Single-Ended vs Push-Pull Amps
00:12:42
Speaker
Congratulations. I wanted to ask about the Decilia 25 watt single-ended jobbers these amplifiers they're apparently the world's most powerful single-ended amp my question is what's a single-ended amp this might be a more of a question for charles also i don't know if i asked this question before i might have i don't know i don't remember anything
00:13:08
Speaker
ah he's He's got a point, man, Charles. You're the single-ended king around here. Ryan and I don't know anything about single-ended. Not a damn thing. i know. Learn how to design, guys. So easy. Everyone does it.
00:13:22
Speaker
um That thing's cool. It it does 25 watts out of a single tube. Arnaud is super nice guy. I've talked to him a few times. What was the question? What's single-ended? So the main difference is...
00:13:34
Speaker
The, you know, in the power, I keep getting in my head because I'm like, well, single ended is every other stage in your amp. You know, all the preamp stages are single ended. Yeah, they are. When someone's talking about single ended versus push pull, it's usually in the power section. So a push pull amp, you split the phase going into the power amplification section. So at the driver stage, which is typically the phase inverter, you split it off to two tubes or two sections and one half is the positive swing of the ac and the other half is the negative and that way when it hits the power tubes the whole amplification potential of the power tube only sees one half of the potential so it can amplify a lot more and then it sums those signals back together in the output transformer so
00:14:24
Speaker
For a tube that can handle you know power dissipation of, or a power amplification of, what is it, 35 watts in a 6L6 or something, you get close to that whole capacity because it doesn't have to split its load. In a single-ended amp, one tube handles the whole signal. So you get typically like, if you're lucky, a quarter of the power that it can dissipate. So if it can dissipate 40 watts, you can get about 10 watts out of it typically um when you're using like off the shelf transformers because the transformer design is a ah lot more rigid, not rigid.
00:15:04
Speaker
What word do I want to use? i don't know, is it more difficult? I guess I don't build the Transformers. it It seems more difficult because you have to deal with more impedance issues and you need a much larger core for the same amount of current, right? Is that right in the Transformers?
00:15:19
Speaker
Yeah, yeah, but no. No, but yeah. No, but yeah. It's more yeah, but no. Yeah, it's a lot more expensive to design, that's for sure, because the transformers have to be a lot larger. Why do the transformers have to be larger? Because you have DC current in the primary, which generates a certain amount of DC flux, which is ah happening at the same time as the AC flux. and you only have enough headroom in the core for a certain amount of flux before saturation occurs. Saturation is relatively soft in silicon steel, but still, you want to avoid it to a certain extent. so You have to account for that DC current and the DC flux that it generates.
00:15:57
Speaker
Furthermore, in order to account for that so the transformer doesn't go into saturation just from the DC current alone, basically, you have to shim the core. and What that means is that you put in an EI core transformer, you put all these one way and all the I's the other way, and you stick some sort of non-magnetic material. For us, it's generally craft paper. Sometimes, it's fish paper. For other companies, they'll maybe use like plastic tape, which is kind of a cheap way to do it. But you stick something in there in order to increase the magnetic like ah path length and decrease the inductance that's there and reduce the core flux that's generated, specifically the DC flux that's generated in the core. the problem is is that you need a fair amount of inductance, especially in you know high primary impedance circuits. you know when When you're driving just one tube and you need 5K or 8K for it, you need a lot of inductance and in order to get decent low end. So, you have to use a bigger core because you're going to lose a bunch of that inductance just to deal with the DC current. So, it's just kind of a compromise. You add the current, and then you start subtracting the inductance. Then you start bringing the core size a bit bigger in order to get the inductance back.
00:17:05
Speaker
Right. And the reason I deal with all of that is because I think they sound a lot more musical for distortion and cleans because I really like second harmonic distortion. And that's the main difference with push pull versus single ended is push pull stuff, all of the second harmonics cancel out. you you lose all the second harmonic because of a phase cancellation. So in single-ended, you get all of the harmonics, kind of the same as the preamp stages. And I find it a lot more pleasing to do gain staging and just you know finding the harmonic palette that way. From the transformer side of things, the single-ended operation produces asymmetrical flux, which produces asymmetrical flux density saturation, which creates mostly even-ordered harmonic distortion, versus push-pull operation, which creates symmetrical flux, which creates symmetrical flux density saturation, which creates predominantly odd-ordered harmonics. But then again, you've got the tube running in class A single-ended mode, which on its own produces more even ordered harmonics as well.
00:18:11
Speaker
Yeah. and And then you've got a preamp behind it that's all single-ended producing mostly even ordered harmonics. So what you're saying is you really love even ordered harmonics. A lot of even ordered harmonics. But it sounds, in you know, the third the third order stuff is what makes stuff sound interesting and layered. A lot of second harmonic, you're just, you know, hitting octaves. Yeah, I just like the balance of everything. i don't like cutting second harmonic or even order harmonics in the in the power stage. i like I like that really pushed single-ended sound where you get a nice balance of of all of it. You're forgetting crossover distortion as well. Yeah.
00:18:48
Speaker
yeah Chris, take it. Take it away. Yeah, there you go. Okay. Sorry. it's I just like watching Charles fight for his life. That was my turn.
00:18:59
Speaker
Charles, I know you know how single-ended stuff works. It's like asking a NASA engineer how a toaster works or something. Right. It's how do limit this to...
00:19:11
Speaker
it's It's always the hardest thing, you know, just, just to, to pause you for a second, Chris, sorry. It's always the hardest thing. And I struggle with this too. When I talk about transformers, it's always the hardest thing that like the stuff that you've learned from like an intuitive perspective, you know, things that you've learned with your ability to be intuitive, you know, and apply knowledge of other things to something new and you learn from. It's always hard when you have that ability and you learn in that method to describe the things that you've learned. Because at the end of the day, I've read a lot of books, but I mean, I don't feel like my knowledge base comes from books. And I know the two of you are the same way. You know, you know your s***.
00:19:47
Speaker
We all know our s*** here. But at the same time, sitting down and explaining it, it's freaking hard. It's really hard. I know i expect relationship questions on this podcast, not amplifier questions. Jesus. It's I've had so many people ask me like, oh how do you make amps? I'm like, huh?
00:20:03
Speaker
What are you serious? You want an answer? What Chris is going to tell us all about crossover distortion now. Yeah. And the the only possible answer is you're not allowed to ask me that. Yeah. Yeah. Um,
00:20:21
Speaker
No, so crossover distortion, the single end of stuff doesn't have it because this is one tube that's going between being fully on and fully off and is pumping current through an output transformer. It's like a valve.
00:20:34
Speaker
The push-pull, you've got one of those pushing, one of them pulling current through that output transformer. And so one one is well one's pulling current through, the other is not pulling as much current. So it's like a seesaw thing through the power section. And the way you can make those more efficient is class AB b or class B, but when no one does class B. is one of the tubes handles one side of the waveform and then a little bit, so maybe you know sixty seventy percent of the waveform. The other is handling the other side, and when it's not handling the waveform, it's shut off, it's not it's not passing any current. so There is distortion that happens when one when that tube shuts off, because that tube, when it shuts off, has a pretty nonlinear characteristic, and it's not like a linear thing. it just
00:21:24
Speaker
goes Brian probably can speak to that more because I'm not entirely sure why crosshairs and the immersion let let let Let me try to finish. Yeah, please, please do.
00:21:34
Speaker
Okay. So that region, there's a region where both of the tubes are conducting. And when you leave that region on both sides of the waveform, that's if you look, you can see it on a scope. You can actually see a little kink in the waveform where there is crossover distortion and that that is not pleasing distortion that sounds bad it's not the good sounder sounding distortion so when you're setting the bias of an amp you're trying to dial out that crossover distortion and there's a region between having bad crossover distortion and pulling too much current through the tube in which case it you know melts down red plates and And what you're trying to do is find somewhere in that region that makes sense to ah to bias the amp so you're you're not getting crazy distortion and you're not over-dissipating the tubes.
00:22:23
Speaker
Yeah, I find the crossover distortion in the KT bottles is a lot easier to manage. I run from my push-pull amps. Well, I don't have any out yet, but the Supernaut's going to be push-pull. And um I run them super hot.
00:22:40
Speaker
So there's... You're a cathode biased as well. Yeah, they're cathode biased. and so you have like inherent current limiting happening in there because of the cathode resistance. So it's, yeah, I like it. It sounds, it's been fun playing with push pull and trying to find something that I like when I'm so used to playing with single ended, you know, up up till now I've done, I've all my amps I've designed for guitar have been single ended, you know, pulling a hundred Watts out of four KT 66's wasn't easy, but ah we managed it and it sounds pretty rad.
Push-Pull Amps and Sound Quality
00:23:16
Speaker
That's the beauty of being able to shift around the plate load. Yeah, it's so cool. And those, man, that's going to be cool. That's going to be fun. Back to the single-ended thing though, the way the Decelia does it, they use those KT150s, those gigantic Russian tubes, which I like, I've never heard the amp. I hear it sounds great, but I typically, with my experience with those tubes, I don't, I don't much like the KT150 or the KT120. I think they sound, at least when I use them in hi-fi and...
00:23:43
Speaker
i I did a single-ended amp one time as a prototype with the KT120, and I liked the sounds I got with the KT66s a lot more. So i I went down that route. But I think someone, I forget the name of it, but someone did a 40-watt single-ended thing, I think with like four 6550s or something like that.
00:24:03
Speaker
I don't think it's available anymore, but it was for a while. So there's there's always been like high wattage offerings available. My parallel does the two KT60 stitches for 25 watts, and that was fun to design. so I'm working on like a 35 watt single bottle single ended design right now for someone.
00:24:22
Speaker
Oh, nice. Yeah. yeah It actually, Chris, it's actually uses your, uh, voltage scaling concept. Dang it. I mean, you know who it is as far as ah it's with permission. So yeah, yeah, yeah. i't I know who it is. You said, you sent this dramatic to me and I know a bunch of other people and said, you should use this. I'm feigning
00:24:48
Speaker
No, I'm kidding. If anyone wants to know, i will literally send you the schematic and I encourage you to use it. It's a cool system. You just have to call in with a question for the podcast. Oh, yeah, yeah. that's You got to pay the troll toll. There it is. you have to call 513-334-3803. That's And we'll respond with it via text.
00:25:18
Speaker
The other fun thing with, I know this is a question about single-ended stuff and not push-pull, but I've been on a push-pull design kick and everything. And the other fun thing, and the cool thing about your amps, Chris, is the you get so much character out of the different phase inverter circuits. And you you don't have that on the on a single-ended amp. So it's a little bit less fun to mess with because you can get so so many different sounds out of changing the phase splitter or arrangement. Oh, yeah. Man, phase splitter sounds so different one to the next. It's insane. So different, yeah. What's stopping you from putting ah ah a differential amp like a phase splitter in a single-ended amp?
00:25:56
Speaker
And then if you use negative feedback, you can use the second grid and the differential for your negative feedback return. Yeah, I know someone who aligned the transformer for that. Yeah, it seems like over engineering at that point. It's like, what if you put four transformers in there? The Supernaut, though, we ended up using an interstage transformer, and that's been really cool to mess with the sounds of, because we're using a really cool driver tube. So the Supernaut's basically, because I still love even order distortion and and single-ended amplification, We designed the driver stage to basically be a small single-ended power amp. So it's like a small single-ended power amp into a phase inverter, it will into a interstage transformer. And we're getting a really, really low impedance out of it to drive a really nice master volume. Well, we did the the voltage secondary separate from the current secondary. So basically, you had a speaker load that was a secondary. And then remember, we did the by-file secondary on top of that.
00:26:55
Speaker
Yeah, so... Which is so ridiculous design. Yeah. It's stupid. Why did you make me do that? yeah Yeah, that's been really, really fun to mess with. But it's the first master volume that I've ever... that hasn't like bothered me.
00:27:09
Speaker
So that's been really
Technical Stories and Challenges
00:27:11
Speaker
cool. I want to say something about the Babylon, since we haven't spoken about it in almost one and a half episodes. Well, Charles has been in Japan the whole time.
00:27:20
Speaker
So the really interesting thing about the Babylon was we used 6L6 single-ended stage to drive the entire power section. Oh, cool. And it used a transformer phase splitter, which is cool. And we were running into this issue so in certain modes that ah the amplitude of the ah phase inverter wasn't quite making it. And you were able to actually see the asymmetry in the ah single-ended stage on the output of the Babylon, because obviously it's just making copies.
00:27:48
Speaker
Right. Of whatever it's seeing. So we had to work pretty hard to balance, both balance that a single-ended stage within reason, because you can never totally balance a single-ended stage. That's why it's got the second order harmonics. But the trick is, if you get the amplitude out far enough, especially in the transformer, the interstage transformer, you don't actually see that asymmetry until well after the power tubes are being driven. Mm-hmm.
00:28:13
Speaker
So you can actually have a very symmetrical single-ended amp driving the power tubes because the ah you know the very tip of it where so stuff gets squirrely, you never see that. The power tubes never see it. You're you're right blowing the doors off the place before it even becomes an issue.
00:28:30
Speaker
yeah the trick The trick with it was, it was very high-grid drive. so the The secondary winding, that that one was by Phylar as well, that was used to drive each side. you You have a really high turns ratio, so you've got plenty of voltage on there. so As Chris said, you like drive the power tubes harder in a way where those tubes would already you know be in clip and you know go to crap long before the single-ended stage exhibits asymmetry. But I also want to point out that one of the things that we struggled with, and i full transparency, I made a mistake. Oh, come on. Don't tell them that.
00:29:05
Speaker
I made a mistake. It happens. I'm human. I swear I'm human. I'm not a robot. where i put the second and When I was doing the the design for that and the resistors I put in to act as the secondary load for the interstage transformer, I just did my math incorrectly, and so they were twice as big as what they should be resistance-wise, which presented a higher primary load back to the fixed bias 6L6 for that stage. so we We had symmetry issues where we saw some clipping happen in the interstage, and we didn't know what it was. and we We figured out not long after that, that was the problem.
00:29:41
Speaker
But the distortion characteristic of the interstage, we actually played that amp at at full volume with that misloaded interstage, with that incorrect load value there.
00:29:52
Speaker
and That was one of the things that we found was that was what was making people, well at least that contributed, besides the volume itself, to making people feel ill when they were playing it, was that the harmonic characteristics of the interstage section and the distortion that was being generated, which was probably just like, what, a shitload of odd distortion, I would assume? What it looked like on the scope was basically a way steeper, narrower waveform.
00:30:18
Speaker
At the top, if I remember correctly. which means the transient is kind of reverse compressed. it's almost It literally looks like it was expanded. so The quick changes were 25% faster than they would normally not way faster twenty five percent faster than they would normally be and Once we got it right, you know it started looking more like ah at a real sine wave. But yeah, it was a lot more pleasant to play after.
00:30:42
Speaker
Yes, extremely. It still did make me sick. What was the step was the step down ratio of the interstates that used? It must have been a pretty steep step down. That's a lot of grid capacitance. You have, what, seven KT88s in parallel on each side? So that's ah that's a heavy grid load.
00:31:02
Speaker
Yep. ah That being said, the geometry of the output transformer combined with the winding design for the bifilar secondary minimized capacitance per side, and then there was series resistance to buffer out grid capacitance.
00:31:16
Speaker
And the thing had enough current drive. I mean, it's, it's impedance was really low. So obviously the capacitance is going to be less of an issue with a lower source impedance. Obviously. i mean, it'll sound sweet anyway. You don't, you don't get natural, natural high end roll off. So that's, I mean, the other thing too, was that like a, it's a guitar amp. I know some people argued with Chris on Instagram that it was a bass amp. And I swear, as the you know the two people who designed it, it was a guitar amp, not a bass amp. But you did prove that it works well for bass, granted. Yes, I did. My point with this is that the also the output transformer, i i was forced to do this, it requires so much secondary current.
00:31:55
Speaker
to drive the 800-plus watts that the damn thing does, it requires so much secondary current that there's no way to wind even a handful of secondary windings with wire big enough to handle that current load. so there are seven no sorry There are five secondary sections all put in parallel, each of them 15- 17-gauge have wire ah thick enough to handle that amount of current. so Because of that, it necessitated an output transformer design that was nine sections ah interleaved. so You have this huge reduction and in leak ah leakage inductance because of the the geometry and because of the balance and the capacitive balance was really low. so The point is, extremely high frequency capable. right
00:32:46
Speaker
so you know Grid capacitance, you know granted, it was buffered out with series resistance, but it actually kind of helps it you know it. It adds stability. We didn't have to do any capacitive shunts into the negative feedback. like It actually offered stability when you had an output transformer that has you know a high frequency response Well past anything we want to deal with. so But that actually helped everything because if you think about it, it having better high frequency response like that means that the negative feedback high frequency is going to be more in line phase-wise. So it it just makes everything more stable. Did you, did the 606, did you try running it in triode mode? And if not, why? Oh, it was in triode. Yeah, we did it in triode. We actually tried it in pentode once. Triode mode is so much easier with interstage transformers. There's, yeah, the the output impedance is so, so, so much lower. If you were saying it was in pentode mode, I was going say, how the did you make that transformer? Yeah, we actually, we did we did try to run it in Pentode when we were kind of troubleshooting it, and it was so microphonic with the Babylon, no matter what power two we used. I mean, I used EL34, just, you know, trying different, you know, play impedances, play resistances, sorry. Man, it was so microphonic in Pentode. You must have lost a ton of low end too. No.
00:34:12
Speaker
I didn't even to listen to it because I was like, there's no way this isn't going to just feed back on a stage. That interstage transformer was the size of a tweed basement output transformer.
00:34:23
Speaker
yeah Oh, wow. With M6. It had a stupid amount of inductance. that Oh, nice. Yeah. I mean, raising the source impedance like that by going to Pento, no. Low frequency was never a problem.
00:34:34
Speaker
Oh, interesting. The problem with the thing was like ringing like the Liberty Bell. I mean, it was insane. Yeah. Yeah. I really like the triode for a driver stage. That's what we did with our inner stage to the we're using the ECC 99. So super low impedance triode tube. It allowed for a lot, a lot less impedance.
00:34:54
Speaker
All right. Well, i have one other kind of fun question for you all. Ready? okay everyone.
Favorite Non-Musical Sounds
00:35:01
Speaker
Long time listener. What's your favorite non-musical sound?
00:35:09
Speaker
What?
00:35:13
Speaker
What's your favorite non-musical sound? Like a sound that isn't related to music or like? Yeah. yeah I just assumed Charles going say fart in Japanese. I thought it was in my head. I'm not going to lie. What was it? Onara? Onara.
00:35:26
Speaker
Onara. well not should I really actually really like the accordion. like wind chimes. I like wind chimes a lot. That's a musical sound. Wind chimes? No, the accord, well, both, that and the accordion.
00:35:40
Speaker
That's what the joke is. Yeah, yeah. Because it's not musical. Geyser falls asleep so fast like he'll get on my lap and like he'll be out in and like 90 seconds and he snores and never fails I mean he's what 11 or 12 we've had him since he was three and that snoring still to this day makes me smile so much it makes me so happy I like rain I like raindrops on raindrops on rooftops
00:36:12
Speaker
which Are you serious? Yeah, love it. What, are you looking for a date? yeah It's so romantic. yeah Charles, not here. Yeah, dude.
00:36:23
Speaker
I like pina coladas, too. I was muted, but I laughed really hard at that one. I like ah the sound of an engine revving.
00:36:35
Speaker
Yeah. I like it when I'm expecting it. I hate it when it's just like random on the street. If I'm walking by and there's some loud ass motorcycles or, or cars revving engines, it's like, it's like that South Park episode.
00:36:49
Speaker
ah Oh No, no. Who wants to say it? no, nope no. no Nope.
00:37:01
Speaker
Thank you for listening to this episode of Amplified Nonsense. Our goal is to release a new episode every other week, so please subscribe wherever you listen. If you have a question for Brian, Charles, and Chris about amps, pop culture, or relationships, please call 513-334-3803 three three four three eight zero three and leave a voicemail. If you enjoyed this episode of Amplified Nonsense, please leave a rating and review.
00:37:29
Speaker
Thanks again, and we'll see you soon.