You can't rectify them anyway, they have so many odd harmonics (square wave output) that as soon as they see a capacitive load (your rectifier/capacitor) they shut down.
I havent' had them make a 10Kp-p 15W transformer yet (I still plan to), but I did get a 8K p-p 15W with 40% UL and multitap output.
Part number is : EM0775-PP, with a unit price of 46.29 last year.
What tubes are you using?
You won't hear the difference between 8K and 10K even in a HiFi amp unless your speaker impedance really changes enough VS frequency to force the amp into distortion on the low impedance parts of the curve. It really doesn't matter in a guitar amp.
The numbers work out. Some power toroids work good as OPT's, some suck. They are all picky about DC balance. I have had good results with some, and not so good with others in HiFi amps. Note, mild transformer saturation is common in guitar amps. It is hard on the output tubes since the current goes way up as the OPT saturates. Excessive OPT saturation sounds really bad and makes amps blow up. Back in the 60's we always heard "never play bass guitar through a Bandmaster". One of my friends found out that this legend was true.
Plain old EI filament transformers are worth trying too. Using a power transformer as an OPT works best when the driving tube is a low impedance source. Triodes and sweep tubes with Schade feedback work best for HiFi, but anything goes here.
I made several guitar amps back in high school using ordinary power transformers taken from TV sets as OPT's. I used the HV winding for the primary and all the heater windings in series for speaker windings. Output tubes were sweep tubes. I really didn't know what I was doing then but some of those amps ROCKED!
Will we see a sweep tube and power transformer OPT based amp in this challenge? I don't know since it isn't finished yet.
Try Antek Antek - Transformers - Grid View They're well built, inexpensive, and have 5, 6, 7, and 9v toroid transformers.
You don't need to rectify anything. You have already 308V DC in 220V inverter.
Ok, since we discussed speakers and their properties that were selected for best sound, what about cabinets? Lots of experiments I am sure were performed to select shape, thickness of material, construction. Where to get some planes for nice sounding cabs for 12" guitar speakers, for example?
You'd think so? But not. The first ones in the 50's were just random size or made small so they could be transported. Later cabs were copies of what sounded good.
Guitar cabs are "dead easy" compared to HiFi. After all there is no signal below 81Hz and the speaker response goes way down after about 5KHz Most of the problems with HiFi speaker design is the bass and highs. Guitars just don't have any of that. The bulk of the sound is all between 100Hz and abbout 1500Hz
The end result is that cabinets have very little effect on the sound. But selecting a driver does matter.
The generic design is a 3/4" pine box with square baffle only about 6" bigger than the speaker maybe 8" to 10" deep and at least one third of the back is open, maybe 2/3 of the back is open. But some people like closed back cabs. You don't design them like HiFi because a guitar will never go low enough to matter, noti if the cab is already large enough to physically house a 12" speaker
The point of the open back is to make the speaker "bi-polar" so the sound interacts with the room and gives a kind of "you are there" presents. The reason you might close the back is to contain the sound, not to tune the cabinit. Some people like the cleaner sound. If you like the closed sound then they sell drivers that "work" for a closed back but most guitar speakers are designed with a Q(t) suitable for open cabs
If you have a bass guitar, different story. Then the goal is to pump out lots of bass down to 40Hz or lower and 1,000W amps are not uncommon. They will use ported cabs
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That's exactly it. Obviously that speaker cabinet is the result of endless hours of computer modeling. Particularly inventive are the horizontal vents in the rear partial cover plate and the way they distribute the sound vertically. Either that or it was simply the smallest box he could fit two speakers and a chassis into and then with tubes inside if there was not a big hole in the back the box would overheat. No. that couldn't be it, must be modeling
Kidding aside. Notice how the sound changes as the amp is handed. And in other You Tube videos watch how the amps are spaced back from walls. Almost everyone uses the back wall as part of the cabinet even if they don't think of it that way. No one places their amp dead center in the room nor do they push it all the way back into the wall.
The cabinet does affect the sound.
BINGO! I made guitar cabinets a lot when I worked at an Olson electronics store and could get 12 inch Olson branded Utah speakers for $15 each. Make two identical cabinets one from plywood (or MDF) and the other from pine. Smack each one with a drum stick and listen to the difference. The MDF or plywood is dead it has no sound of its own. That's what you want for HiFi. A pine box will ring and resonate and yes size matters. Covering the pine box with thick material will deaden the sound. Look at the old Kustom cabinets. They were plywood covered with an inch of foam and a thick piece of Naugahyde. About as dead as a coffin. There is a reason why Tolex is thin.
I made box number 1 last week. As stated above it is about 12 by 14 inches and 9 inches deep. It will use an 8 inch cheap Peavey speaker. I will experiment with the back but unless the cabinet is dead or large you want it partially open with the hole near the center. A flat piece of pine behind the speaker and parallel to the front of the cabinet will send its sound right back through the speaker cone. This can create a uneven frequency response. I may use plywood for the back of my pine boxes. It's been over 40 years since I made guitar cabinets, so I just bought a bunch of cheap speakers and a lot of wood.
I am with you on the cabinets. I prefer 3/4" cedar or if needed to keep price down then pine. MDF, chipboard and plywood do not make good sounding speaker enclosures! Having said that the face can be made of MDF, chipboard or plywood without much change in sound if the box itself is made of cedar or pine.
I also agree on the effect on the sound of the covering materials used. So, choose what suits your preference for sound.
No, obviously it does affect the sound a lot. Back in 1970 when I made cabinets my brother and I tried a lot of stuff that didn't work. Mostly we just copied old amp cabinets. For some players a "dead" cabinet is desired.
Kustom sold a whole lot of amps in the early 70's. They are a big part of the unique sound that put Creedence Clearwater Revival on the top of the charts. Look for the shiny amps behind the lead singer with chrome ports in the cabinets. Note the Les Paul plugged directly into the amp with no processing. I used to have one of the same amps. They are solid state and very clean. Power amp circuit is a HiFi design right out of the 1969 RCA transistor manual.
Creedence Clearwater Revival - Bad Moon Rising (Live) - YouTube
Creedence Clearwater Revival: Green River Live - YouTube
I am sure many of the vintage amps we cherish were either hand tweaked, or "build it and try it". Computer modelling wasn't even a dream yet. Wait Computers weren't even a dream yet.
I started working in the Motorola plant in 1973. There was exactly 1 computer in the building. It was a giant IBM system that did payroll and other general business opreations. ALL engineering in this state of the art facillity was done by hand. PC board layout was tape on mylar and fancy photography. We had a totally awesome darkroom in house. It's a bit different now since my cell phone has more processing power than that IBM system did.
Note that most vintage combo amps were open back (for tube access) and many stand alone speaker cabinets were sealed. There was an Ampeg bass guitar system that used a quasi horn (V4B?). It launched the bass out into the audience. Bass was louder against the back wall of a large room than it was in the first row. The more popular SVT relied on 8 X 10 inch speakers and 400 watts.
Some owners replace the front baffles of newer amps because they were made from MDF and they feel the sound is too dead. Fender used to have their front baffle of their Tweed amps suspended by four screws, the baffle would continue to vibrate after the note started to decay.
On the topic of vibration and resonances, some acoustic feedback made its way back to the tubes in a combo. Depending on the tube there might be a fine line between enough or too much though.
If the back opening of the cabinet is large enough vs it's internal volume to place the Helmholz resonance well below the lowest notes, then the enclosure should act like an open baffle and would be analyzed as such. There can be a lot of coloration depending on the 1/2 wave distance around the edge of the baffle. I would expect that and the driver characteristics to define the basic "sound" of the cabinet.
Hmm. The speaker cab response is not likely to be flat... Where it peaks and dips will create a sound that may or may not work with the instrument, player, and music being played. Sort of like a hollow body guitar. Clearly one doesn't want "wolf tones" or serious muffling of anything, but to some extent it just defines a unique sound, not good or bad.
One thing I have found is I can't predict what I will like from the response plot.