Amp Design Becomes Amp Building | A Lot of Factors to Take into Consideration but also Cool Goodies

[@PsionicAudio]

Before anyone does the "well, actually..." thing about the current rating of the choke, yes, I simplified that. And I think I oversimplified that. I just didn't want to get sidetracked into a big discussion of the role of a choke in an AC15 style circuit where the choke is feeding the output tube plates. In theory a more perfect solution would be one choke on the DC positive and one on the DC negative, allowing two smaller chokes. But there is a risk of "improving" the AC15 to the point where it doesn't sound like an AC15. So I'm pondering. I think I can fit the big one in, just got to experiment with output transformer placement/orientation first.

[@notfeelintoogoodmyself2697]

Now you're talking. The looks are important, but not so much that it makes up for losing the magic touch.Too many guys shoot for perfection and then wake up to CBS style "improvements" that nobody wants. Maybe there are alternative ways to remove feline dermis, but you will never know, for instance, if sticking out your tongue will make your concentration better, unless you try it yourself. I have heard that transformers have a lot of voodoo in them, and you shouldn't worry with global sales until you can make yourself completely happy with the basic package. Can you make the whole amp circuit work together in balance from input to output and have a strong, musical voice that makes players lose track of time in the zone? I know you're good, but I also hope that you're lucky. Build it from your heart and the players will bless you. I've got a good feeling.

[@chipsterb4946]

You’re talking about a reservoir capacitor before the plate node with a choke on both the negative and positive ends of the reservoir cap?

[@stubbyfex]

Hello from a fellow amp tech and builder! Good job on the videos! I just retired after 36 years in business. My biggest advise to someone starting out: buy a Metcal soldering iron! I got one only a year or so ago and it even solders the ground wires onto a Fender chassis. Oh, perhaps one other thought: Save one dollar from every repair. I did over 16,500 repairs over the years, so it would be a nice nest egg by now! Thank you for sharing your wisdom with us and Blessings!

[@jasonstone1046]

Gotta love when you come home to new toys. Happy days!!

[@efsglass]

Oh man, I cant wait to see what you do with my 68 custom deluxe reverb!! That board looks insane and I love mercury transformers! My local buddy who owns New Vintage Amps, uses Mercury exclusively! Very cool stuff lyle, keep these vids coming!

[@richclayton5785]

I lost track of this series…you’ve made some great progress.

[@shanedolman1368]

Oooooh I always get all excited when the new bits arrive😁. Those boards look great and very solid. Hope you had a great trip Lyle and good to see you back👍

[@hkguitar1984]

Back in the early 1980s I helped maintained an Air Force F-4 Phantom Flight Simulator. The primary computer for that Simulator was built in the '50s with technology they knew would work, as such it was an analog tube computer the size of a house (a big house). My point being, the turret circuit boards used in all the amplifiers reminded me very much of the new turret boards shown in this video. Super heavy duty is the way to go if possible.

[@SkyscraperGuitars]

All of this is interesting information. If it were me, I'd file out the hole for the IEC... I've filed a lot of aluminum in my day, so I don't look at it as too big of a job, but it does add time... As far as the oversized holes, that's a huge bummer. I love hearing about the circuit design. I still don't know nearly enough about all the bits and pieces of the circuits, so it's good to hear about transformer specs and what they do to the sound. Thanks for bringing us along with you.

[@dan_perry]

It's always a wonderful day when parts come in.

[@jancreighton]

think I mighta drooled whilst watching this - things are shaping up

[@russellhltn1396]

Looking forward to your discussion of a loading resistor to keep the amp from blowing up without a load.

[@williambock1821]

And good god an IEC makes the chassis easy to maneuver. That Alpha impedance switch made me nervous too but Hammond sells them specifically for their 1600 series transformers which go up to a fairly high wattage and makes them a lot easier to be wire. Those things are a puzzle to figure out when you’ve never wired them before!

[@edwardhannigan6324]

Serious looking hardware..! Look forward to the build..Ed..uk..😀

[@Rufko]

I'm maybe large but I'm working on it...nice one Lyle :-)

[@alexwoolridge94aw]

I added an iec that I was able to screw in to my mojotone 18w tmb without having to rout the aluminum chassis. It was small enough it fit right in their routing. However the iec outer lip didn't hide the gap. It doesn't look amazing but not terrible either and no wiggle

[@matthewf1979]

I think the Hoffman Stout chassis takes the screw in IEC type. There’s room for a choke too. Unfortunately it has 3 octal socket holes. Otherwise it would be a ringer.

[@goodun2974]

Another possible design consideration for snap-in vs. screwed-in IEC socket: the screw-in type can be obtained with built-in fuse-holder tray that also holds a spare fuse, but I don't think any of the snap-in IEC sockets have a fuse-holder built-in. Are you planning on using 3AG, or F-size fuses? Not really a consideration for a tube amp build, but IEC sockets can also be had with built-in RF filtering....

[@dennisflock3958]

I'd love to send you my 65 Deluxe Reverb reissue to quiet the noise floor and hum I am getting. I am sure it needs biasing as well. It is factory stock except the 7025s in V1 and V2.

[@bryantcoleman5619]

Check out his video on the ‘yet Deluxe Reverb. He shows the fixes for those issues.

[@dennisflock3958]

I've seen those, thanks. Just not an amp tech

[@stevencancel1727]

Always wondered if it was feasible or practical to utilize and incorporate tone controls that are designed like the ones in the best studio or concert mixers where they have high mid and low mid sweeps for frequency adjustment, thanks for your tutorial

[@PsionicAudio]

People have tried putting active parametric EQs in guitar amps. Historically, guitarists have not embraced them. It’s a lot of work to put in an option few know how to use.

[@stevencancel1727]

@@PsionicAudio as a professional sound engineer and performing musician that works with countless local and national amp builders, (Guy Hedrick Bad Cat Guytron, Bruce Egnater, George Metropolis, Chris Andrews, most have a cold response to the idea, I like the way the sweeps work with the sound and may have to develop the circuit my self with the help of an open minded tech trick is to find a tech willing to design such a circuit, many think less is more better sound with less knobs in the circuit, again enjoy your tutorials as if I ever had your amp building skills with my hearing I could build and design some really good amps

[@kbkman7742]

Just listening to your discussion of trans placement... have you worked on an orange ad30? They have the ot and pt over on the far side together, away from the inputs and have a normal flat chassis like that.

[@richclayton5785]

Would a shoulder washer work to adapt your preferred rotary impedance switch into the hole that’s too large?

[@PsionicAudio]

I don't like kludges in new amps. I decided to use a standard two position switch giving 8 and 16 ohm options. No 4 but that's ok.

[@bryantcoleman5619]

Informative and entertaining as always.

[@lonniezamarripa959]

Ahhh, progress 👍

[@ampyamps]

What’s the issue with putting the choke 3rd in line again? I understand keeping AC currents away from the inputs, but chokes are DC. There’s high voltage DC running all over that circuit anyway.

[@PsionicAudio]

Nothing huge* (see the next video in this series). Just a general preference for keeping the big power stuff away from the inputs. *PS the DC on the choke still has ripple on it, so it can be an issue but I have steered things just so.

[@DonaldVanHall]

Did you consider the output transformer on the left, farthest from the input? If so then what would you put closest to the input, the choke or the power transformer?

[@PsionicAudio]

No, the PT should be farthest, and the chassis holes fit this PT perfectly. As to the rest, stay tuned.

[@grif900]

I do hope all that will power was found at the bottom of the cup.

[@timmooney7528]

Couldn't a spacer or proper diameter washer be used to reduce the diameter of the 1/2 hole to allow the use of a 3/8" impedance selector?

[@PsionicAudio]

The really good impedance selector switch is no longer made, and 6A rotary switches are really expensive. This will be good at a lower cost.

[@sevenity2677]

Are you selling those amps or is it personal build?

[@PsionicAudio]

For sale.

[@duncan.5228]

Similar mistake people make on crossovers. Mounting the chokes in the same orientation.

[@jimmyjoefine]

I think I'm understanding you correctly about transformer orientation, but the takeaway seems to be that this is a problem that might become exacerbated as the overall power of the amp is increased. Is that a correct take on what you are saying, or is that too overly simplistic? Just wondering as I have amps that have all the transformers (choke, output and power) oriented in the same direction with no issues that I can discern. Thank you and thanks for what you are doing, your explanations of things are the reason I've started to watch your channel more than the other amp repair video channels.

[@PsionicAudio]

Thanks! Not really correlated to power, as I've had 100W amps that hummed because of this and 5W amps that hummed worse. Sometimes you can get away with it, most of the time you can't. Always check.

[@jimmyjoefine]

@@PsionicAudio Will do, and thanks again. I really appreciate your generosity to share your knowledge on such a wide range of amplifier topics. I'm learning a lot!

[@jimmyjoefine]

@@PsionicAudio And one additional thought, I wonder if it's simpler for Mojotone to supply the chassis with the rectangular IEC jack. I recently did a conversion to an old amp where I installed a screw-in IEC jack and it was the most work I had to do on the entire amp to cut the properly shaped (trapezoidal) opening. But then again, I did all that by hand, it wasn't die stamped.

[@scottdunn2178]

I knew Ken Fischer since 1988, and one thing we never talked enough about was chokes. I play power metal (Accept/Loudness, etc.) and I was under the impression that a 3 henry would be best to mod my JCM 2000 DSL100, but I want that "bloom" and "swell" on sustained chords (listen to any track on Accept - Balls To The Wall) but you're saying a 10 henry would be better for that. Can you elaborate further? Edit: Accept were using 2204 MV (with I assume 3 henry chokes?) so maybe I just answered my own question. Regards 🎸

[@PsionicAudio]

I think the sound you're hearing on those chords on the album is studio compression. Ducking the attack with the drum buss trigger with a long decay envelope gave big '80s sound with a tight band downbeat and huge chords. Check out Pyromania for that. I meant more for extremely fast alternate picking styles or "djent" with seven strings or extreme detunings. It's a complex subject, and you have to differentiate between what an amp sounds/feels like versus a studio recording. Especially with glossy '80s hard rock.

[@scottdunn2178]

@@PsionicAudio So a 3 or 10 henry choke?

[@PsionicAudio]

The guys in Accept would most likely have had 3H-5H chokes.

[@scottdunn2178]

@@PsionicAudio Was thinking that too. Thanks 👍

[@halhawkins7641]

Excalibre!!!!

[@markarita3]

Solid stuff. Now math away :-)

[@barneycartwright4107]

I would use a good quality flat file to open that hole up.

[@PsionicAudio]

The issue becomes on how many chassis? How much time/cost does that add? I'm pondering some things.

[@markarita3]

@@PsionicAudio Yeah, not alot to take off, plus it's aluminum, that'll shave off like buttah! But if you have many to do, then, yes, I would make some kind of production router jig like you mentioned.

[@waynegram8907]

When using Choke a 10H at 100mA compared to using 20H at 100mA, what does this do to the sag/compression by adding or subtracting the inductance of the choke? I'm not sure what the inductance rating of the choke does to the amplifiers design and theory behind that

[@PsionicAudio]

To extremely simplify, assuming DC resistance stays the same, the choke with more inductance filters more ripple from the DC. As does increasing filter capacitance. At that point it gets really complicated. Put it this way - a lot of classic guitar amplifiers are under filtered from a theoretical perspective. This was done because guitar amps back in the day were designed with low production costs foremost in mind. And musicians tend to love those "classic" amps, including the behavior that an underfiltered amp exhibits. About the only classic guitar amp that is more or less "correctly filtered" from a theoretical perspective is the HiWatt DR103 and similar models. And that is a very different sounding/feeling amp then a Fender, Marshall, or Vox. Maybe the Marshall Major approaches it, but again, a very different sounding/feeling amp.

[@waynegram8907]

@@PsionicAudio The Laney 70's amps that black Sabbath used had some sorta of weird filteration section because the 60hz doesn't filtered out by the choke so the 60hz would merge/bleed into the power tubes giving subharmonic frequencies like an octave pedal. I'm not sure if they used chokes or what.

[@PsionicAudio]

@@waynegram8907 they used chokes. Laney was just making bad copies of Marshalls and those amps had bad ghosting due to multiple mistakes in the "design."

[@waynegram8907]

@@PsionicAudio But the Ghosting was due I thought from the AC ripple merging bleeding in with the DC bias voltages to the power tubes. I'm not sure if the Ghosting is considered audio crosstalking or consided AC ripple bleeding in with AC inputs of the Power tubes and DC biasing but the ghosting creates subharmonics like an octave pedal

[@PsionicAudio]

I know what ghosting is, and it has nothing to do with bias. But I can't get into the causes right now. See if Uncle Doug has a video on ghost notes and filtering.

[@goodun2974]

The most important question ---- what kinda dog you got?

[@bryantcoleman5619]

And is his name Rusty?

[@PsionicAudio]

Black lab. Her name is Bella Bambina Uh-huh.

[@goodun2974]

@@PsionicAudio , I have an Anatolian Shepherd, a Humane Society rescue from Kentucky, 120 lbs, a true gentle giant; and a 25 pound Cairn Terrier, a local rescue.

[@alexkay1874]

the choke is ugly you should put it on the underside

[@PsionicAudio]

Won't fit, sadly.