all this toroid talk...I grabbed some popcorn
Electrostatic Headphone Amplifier & IMC for 300B
about halfway down
"One toroid sits physically atop the other. Both are wired in phase, but the top transformer has been physically flipped so the two AC fields about the transformers will cancel, as the two fields are in anti-phase in this arrangement. In the past, I tried running backwards a 60Vac toroid with two 120Vac primaries, wherein the 120Vac wall voltage entered the 60Vac winding and the two 120Vac windings became a 480Vac center-tap secondary. It mechanically hummed like crazy, alas. The two stacked toroids are quiet. Perhaps, mechanical vibration also cancels, much like the AC fields or like the two anti-phase air pumps in the more expensive quiet aquarium air pumps."
Electrostatic Headphone Amplifier & IMC for 300B
about halfway down
"One toroid sits physically atop the other. Both are wired in phase, but the top transformer has been physically flipped so the two AC fields about the transformers will cancel, as the two fields are in anti-phase in this arrangement. In the past, I tried running backwards a 60Vac toroid with two 120Vac primaries, wherein the 120Vac wall voltage entered the 60Vac winding and the two 120Vac windings became a 480Vac center-tap secondary. It mechanically hummed like crazy, alas. The two stacked toroids are quiet. Perhaps, mechanical vibration also cancels, much like the AC fields or like the two anti-phase air pumps in the more expensive quiet aquarium air pumps."
A violation in this manner usually summons up a visit from the fire gods and the smoke monster!
OK, after reading Broskie's whole story he is feeding two 60 volt windings that are wired in series with 120 volts.....this makes more sense, and can be done if both transformers are equally loaded under all operating conditions. I personally would NOT do this because the possibility for a smoky result is real.
The humming and buzzing occurred when he tried to put a can over it all. A can with a bolt through the center that passes through the center of the toroids WILL create a SHORTED TURN unless there is a break in the path somewhere. This is also true for a single (not stacked) toroid. A single shorted turn made from a fat bolt and a metal can could draw enough current to create buzzing, humming, and maybe smoke and fire!
Sorry My friend
Just by accident I do not Build tube Amps. But I do design Class A Transistor Amps.. For a long time..What's about 30 years, do you think this is enough for someone to understand electronics?
And I Stack Transformers for more than 20 years already. Toroid are more easy to stack then C-Core or EI
With Toroid you have the possiblilty to find minimum of Magnetic Field..
Nowdays Magnetic Field measurement are easy, we are in the Digital Age, for everthing you can buy a Testunit..
Anyway, I invite you to make a short trip to Swiss, borders are open again..
Comon, take a look and see for yourself, that not everything what you read is the thruth.. Paper takes everything.. the truth as well as lies..same with youtube and F***ingbook.And all what you dont like.. I think you must be a nice guy, but sure to closed up, life is to short to take it too serious. Or shall I come to you.. send me your Address..
If you want to come then just PM me, or if you want that I come to you I will send you my Address. OH BTW I'm almost 70.
Schönes Wochenende
Gruss Chris
Just by accident I do not Build tube Amps. But I do design Class A Transistor Amps.. For a long time..What's about 30 years, do you think this is enough for someone to understand electronics?
And I Stack Transformers for more than 20 years already. Toroid are more easy to stack then C-Core or EI
With Toroid you have the possiblilty to find minimum of Magnetic Field..
Nowdays Magnetic Field measurement are easy, we are in the Digital Age, for everthing you can buy a Testunit..
Anyway, I invite you to make a short trip to Swiss, borders are open again..
Comon, take a look and see for yourself, that not everything what you read is the thruth.. Paper takes everything.. the truth as well as lies..same with youtube and F***ingbook.And all what you dont like.. I think you must be a nice guy, but sure to closed up, life is to short to take it too serious. Or shall I come to you.. send me your Address..
If you want to come then just PM me, or if you want that I come to you I will send you my Address. OH BTW I'm almost 70.
Schönes Wochenende
Gruss Chris
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I thought the series connected interleaved primary solution was a clever way to squeeze more low frequency juice from some cheap line frequency power toroids. I may use this solution in conjunction with a new driver board that includes autobalancing for the P-P output stage. I may also try the autobalancing scheme with some Amplimo toroids I have hanging around that are explicitly designed as OPTs for a tube P-P stage.
There has been a lot of discussion here about toroids and printed circuit boards but little about amplifier circuits. I wouldn't be surprised if the original poster gave up on this thread and went elsewhere for help.
Fabei, if you are still around, I think George's (Tubelab's) suggestion to provide a little more information about what you are trying to do would be helpful. But in the interest of trying to get back to the original question, here is a classic collection of RCA circuits from the late 1950s that might give you a few ideas.
http://www.tubebooks.org/file_downloads/RCA_HiFi.pdf
The "15-Watt High Fidelity Audio Amplifier" on page 10 might be a good start. The 7199 tube is out of production and hard to get but the 6GH8 is a good substitute and reasonably inexpensive. It has a different pin-out from the 7199 but that is of little consequence if you are going to use point-to-point wiring. The 6973 output tube is in current production so the circuit could actually be built pretty much as shown here.
TubeDepot.com | Electro-Harmonix 6973 EH Power Vacuum Tube
This is just the power amplifier, so if you need a preamp to go with it you could look at some of the other circuits in the collection.
There are countless other circuits that you could build, depending on your objectives. Good luck!
Fabei, if you are still around, I think George's (Tubelab's) suggestion to provide a little more information about what you are trying to do would be helpful. But in the interest of trying to get back to the original question, here is a classic collection of RCA circuits from the late 1950s that might give you a few ideas.
http://www.tubebooks.org/file_downloads/RCA_HiFi.pdf
The "15-Watt High Fidelity Audio Amplifier" on page 10 might be a good start. The 7199 tube is out of production and hard to get but the 6GH8 is a good substitute and reasonably inexpensive. It has a different pin-out from the 7199 but that is of little consequence if you are going to use point-to-point wiring. The 6973 output tube is in current production so the circuit could actually be built pretty much as shown here.
TubeDepot.com | Electro-Harmonix 6973 EH Power Vacuum Tube
This is just the power amplifier, so if you need a preamp to go with it you could look at some of the other circuits in the collection.
There are countless other circuits that you could build, depending on your objectives. Good luck!
Sorry about that - back on topic. Since the original intent was a bedroom amp, ~15W per channel or thereabouts would be totally adequate. An SE circuit with even lower output would also be sufficient, given efficient speakers. The SE solution would have the advantage of lower parts count, at the expense of somewhat beefier output iron. The "El Cheapo" P-P amplifier might be a good start for a P-P solution. A variant of the "Champ" SE amplifier (originally for guitar) with better output iron may be an option for a low power SE solution using a 6V6 output.
For a bedroom amp. P_P with EL84/6BQ5 or 6AQ5 outputs would be totally adequate. A single ended solution could use anything from an EL84 or 6V6 (couple of watts) to a 6L6GC (5-8W)
Another option would be to round up an old console amplifier chassis, and either tart it up or strip out the the iron and build it fresh on a new chassis. The ones I have seen commonly use P-P EL84 or also SE 6V6. The circuits for the various chassis types can be found online, or also in Sam's Photofacts. Old Magnavox console chassis abound on E-prey...
For a bedroom amp. P_P with EL84/6BQ5 or 6AQ5 outputs would be totally adequate. A single ended solution could use anything from an EL84 or 6V6 (couple of watts) to a 6L6GC (5-8W)
Another option would be to round up an old console amplifier chassis, and either tart it up or strip out the the iron and build it fresh on a new chassis. The ones I have seen commonly use P-P EL84 or also SE 6V6. The circuits for the various chassis types can be found online, or also in Sam's Photofacts. Old Magnavox console chassis abound on E-prey...
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Other options - "Baby Huey" P-P amp detailed right on Diyaudio. Another source of chassis to modify would be old organ amplifiers. You might need two to make a stereo amp, since a lot of them are mono.
I also use a Bedroom amp..15Watts are overpowered..unless someone is deaf,,, I use may .002watts...while listening in the bedroom at nigth,. the amp is connected to a timer, so it will switch off after 90 minutes by itself..it will also be turned on in the morning by the timer, with a Rock Radio Station playing its music.. BTW the Station is from Germany as our stations heere in swiss palying everday the same music, depends who selects the songs and who pays for it.. just disgusting.,. So german stations are better in this point of view, even also there it happens sometimes.. OH and yeah since its on the internet you can listen to them search for Antenne Bayern, or Rock Antenne.. on the Internet..
Guys have a nice weekend..
Regards hopefully Fabei gets a AMP for his Father..
Guys have a nice weekend..
Regards hopefully Fabei gets a AMP for his Father..
this thread turned out full of great tips and unexpected things to learn!
I agree that 15W for a bedroom amp is LOUD but I have to say that older people tend to be more on the deaf side and my father likes to share unsolicited music with his neighbours!
Ray Waters thanks for all the input!
I had some very intense shift a work and plus the thread was quite silent in the first days so I thought it was dead!
The stacked toroidals are quite a nifty idea imho. Not a fan of the look but I like the 'science' behind it!
So please if you have more ideas keep posting here, it's becoming more of a collection of nifty amps to make!
I agree that 15W for a bedroom amp is LOUD but I have to say that older people tend to be more on the deaf side and my father likes to share unsolicited music with his neighbours!
Ray Waters thanks for all the input!
I had some very intense shift a work and plus the thread was quite silent in the first days so I thought it was dead!
The stacked toroidals are quite a nifty idea imho. Not a fan of the look but I like the 'science' behind it!
So please if you have more ideas keep posting here, it's becoming more of a collection of nifty amps to make!
Happy to see you.. thought you dropped that thead because of drift away fromt eh center question..
Stacking Toroids can be done that it looks good..
In your humble opininion that might be a nifty idea. But in reality no pro designer does it this way. Must be a reason for...
Either they never though of it, or they are making a large run of products where it would be cheaper to have a custom coil made. If I had potted them in epoxy in a nice can with nice leads and mounting, you wouldn't have even said anything of it which makes it more about aesthetics than functionality. That entire amp cost me about 150$ to build, roughly the cost of potting the coils in nice cans, or the cost of a single Hammond OPT... 🙄
I'm still waiting for you to post pictures of your craftsmanship, but I'm starting to think you don't actually DIY anything.
I'm still waiting for you to post pictures of your craftsmanship, but I'm starting to think you don't actually DIY anything.
This is a DIY audio forum, not a professional audio forum. What a "pro designer" would or would not do is not particularly relevant here.
The original poster wants to build a small bedroom amp for his father. If you have a circuit that you feel meets that need then please share it. Otherwise, most of what you have posted is not helpful. Can we get back on topic here?
Without the presence of interacting electromagnetic fields, amplification would not occur and the Universe would not even exist. Signal integrity requires high intensity, tightly coupled electric and magnetic fields in a proper ratio. Tubes possess those characteristics which is the main reason for their excellence and inefficiency. The weak magnetic field around the toroid is not a feat, but it reduces the need for shielding. The magnetic field distribution can be described in terms like phase angle, magnitude, direction, velocity, spatial extension, shape and is specific to device topology.
Hysteresis and saturation are chronic diseases of magnetism, primarily because the driving fields are much faster than any conductive medium. Leakage flux is largely a symptom of overload (abuse). The "linear operating region", whatever it means, is just a small fraction of "maximum power rating" generously defined by manufacturers.
I have been advocating an enhanced transformer core resistivity (equivalent series resistance). The lower the resistivity, the higher the magnetic moment, the higher the saturation, the more random the polarization and the lower the bandwidth.
The quantification of bandwidth has usefulness in marketing. Performance under real load that matters and that is tricky to predict (immeasurable).
The purpose of toroidal transformers is to save manufacturing effort, material cost, weight and space. High quality (output) transformers cannot be manufactured inexpensively and do not have mass market appeal.
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The "El Cheapo" is based on a very old and innovative English design from the single-ended directly heated triode era (early 1930thies). I would make some modifications...
Hysteresis and saturation are chronic diseases of magnetism, primarily because the driving fields are much faster than any conductive medium. Leakage flux is largely a symptom of overload (abuse). The "linear operating region", whatever it means, is just a small fraction of "maximum power rating" generously defined by manufacturers.
I have been advocating an enhanced transformer core resistivity (equivalent series resistance). The lower the resistivity, the higher the magnetic moment, the higher the saturation, the more random the polarization and the lower the bandwidth.
The quantification of bandwidth has usefulness in marketing. Performance under real load that matters and that is tricky to predict (immeasurable).
The purpose of toroidal transformers is to save manufacturing effort, material cost, weight and space. High quality (output) transformers cannot be manufactured inexpensively and do not have mass market appeal.
¤¤¤
The "El Cheapo" is based on a very old and innovative English design from the single-ended directly heated triode era (early 1930thies). I would make some modifications...
In case someone, against all probability, would want to reduce distortion in the "El Cheapo", getting rid of the differential amplifier by referring the cathodes to ground, would be a good starting point. kodabmx, could you please draw a revised diagram of this most applicable topology?
"El Cheapo" is just fine, thank you. Distortion is low, given a GNFB loop around only 2 stages and the O/P "iron". The CCS in the LTP tail forces symmetry between the 2 sides and coupling at those cathodes is close to ideal. Unlike most LTP situations, the non-inverting grid is driven, not AC grounded. That non-inverting grid is the point at which NFB is applied.
Reports from the field suggest that the performance limiting factor for the design is in the quality of O/P "iron" used. "The better the "iron", the better the amp." Absolutely nothing new about that. The "Gold Standard" O/P "iron" for "El Cheapo" builders is the "Dynaclone" Z565, but its cost exceeds very low budget constraints.
Years ago, "El Cheapo" was a reaction to a request for a decent amp, whose budget ceiling was ridiculously low. The schematic shows guitar amp O/P "iron" that no longer meets the needs of economy. We were able to come up with a 200+ mA. B+ supply that is low cost and high performance. 😀 A good PSU is essential for performance. The logic "lingo" is necessary, but not sufficient.
Reports from the field suggest that the performance limiting factor for the design is in the quality of O/P "iron" used. "The better the "iron", the better the amp." Absolutely nothing new about that. The "Gold Standard" O/P "iron" for "El Cheapo" builders is the "Dynaclone" Z565, but its cost exceeds very low budget constraints.
Years ago, "El Cheapo" was a reaction to a request for a decent amp, whose budget ceiling was ridiculously low. The schematic shows guitar amp O/P "iron" that no longer meets the needs of economy. We were able to come up with a 200+ mA. B+ supply that is low cost and high performance. 😀 A good PSU is essential for performance. The logic "lingo" is necessary, but not sufficient.
