Looknig for suggestions for amplfiers.
3/5/2006 8:48:52 PMJK(37492:0)
Does anyone have any good sites for schematics for HI fidelity amps. I'm looking for something easy to build, with decent sound, and about 10-20 watts of power. Doesn't have to be fancy, but want some thing with good sound, like a triode or pentode push pull. Thanks for any suggestions. JK
3/5/2006 9:06:00 PMTerry Judkins(37493:37492)
Not to blow my own horn but here http://home.comcast.net/~suptjud/HomemadeHiFi.htm is one that I threw together from accumulated junk box parts. Cost was low because of the recycled parts and it has very low distortion and about 18 watts sine wave 1000hz into an 8 ohm resistor. Further specs in the writeup.
:Does anyone have any good sites for schematics for HI fidelity amps. I'm looking for something easy to build, with decent sound, and about 10-20 watts of power. Doesn't have to be fancy, but want some thing with good sound, like a triode or pentode push pull. Thanks for any suggestions. JK
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3/5/2006 9:08:50 PMThomas Dermody(37494:37492)
www.tubesandmore.com sells very nice mono and stereo push-pull amplifiers. They put out about 8 watts per channel, which is really fine for home listening. You can get a lot more listenable distorted output from a tube, so actual output can go above 8 watts without too much loss of pleasure (tubes distort nicely).
You can make an AC-DC mono or stereo amplifier for less money because it will lack a power transformer. Still, the kits found at the above web site are really nice.
Thomas Dermody
3/6/2006 9:36:28 AMChuck(37502:37492)
:Does anyone have any good sites for schematics for HI fidelity amps. I'm looking for something easy to build, with decent sound, and about 10-20 watts of power. Doesn't have to be fancy, but want some thing with good sound, like a triode or pentode push pull. Thanks for any suggestions. JK
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http://www.ceriatone.com/productSubPages/Kitfiles/fender5e3Kits.htm
3/6/2006 10:59:39 AMThomas Dermody(37506:37502)
Fender amplifiers are wonderful amplifiers, but I wanted to point out to everyone that they aren't designed for high fidelity reproduction. They are designed specifically for the instrument that plugs into them. This also has to do with the speakers that are often used in Fender (and other) instrument amplifiers. The speakers are often very harsh in reproduction. The amplifiers, too, though, are designed to pass most efficiently the notes which are produced by a guitar. Speech comes through forcefully and quite well, but not at all naturally. If you ever play a violin through a guitar amplifier, it'll have a terrible grunt to it. In order for an amplifier to be high fidelity, it must reproduce all notes equally, without peaks or troughs. Of course if you're really up on amplifier technicals, you can always modify a fine Fender amplifier so that it is musically balanced (I do this to amplifiers all the time).
Thomas
3/6/2006 1:46:41 PMRMeyer(37510:37506)
Check out the HOW TO section at http://www.angela.com/
if you want to built ultra linear, or want to design your own check out http://funwithtubes.com/
For the best in single end Triode design look at http://members.myactv.net/~je2a3/shoptalk.htm
3/6/2006 5:25:40 PMThomas Dermody(37519:37510)
One of my favorite triode output amplifiers to build was this one: http://www.nostalgiaair.org/PagesByModel/292/M0010292.pdf
It was one of the first amplifiers that I ever built. I built it when I was 15 from the schematic of an empty phonograph cabinet. I still have this amplifier and the cabinet. I wish I could find pictures of the inner workings so that I could refurbish it. I have yet to see another one like it. The amplifier is superb, though, with plenty of power. A transformer can be found at www.tubesandmore.com. The volume control network is for a high output crystal cartridge. A conventional 1 to 3 meg volume control will work fine (eliminate all the parts given in the original network, save the tone control, though I think a 1 meg would be better for the tone control..experiment with condenser values from .002 MFD to .01 MFD), with a .02 MFD condenser going to the grid of the #57. In mine I eliminated part #11. You can play around with the #3 value as well as the #2 value. I left #2 alone with a .01 MFD for #3. This produced some very pleasing negative feedback, but come to think of it, #2 is a rather high value. With such a high value for #3, #3 was acting more like a tone muting condenser by passing through #2. Anyway, experiment with those values if you ever build this amplifier. The 2A3 has become quite expensive. The dual plate type is what I used, though, with much success. This amplifier has amazing power and tonal quality.
Thomas
3/6/2006 7:07:04 PMDoug Criner(37524:37519)
You know those <8W amps that Thomas referenced from www.tubesandmore.com should have plenty of power. You might need a preamp for a phono input?
A thing to keep in mind is that modern, high-efficiency speakers could drive you (and the neighbors) out of house and home with just a few watts.
You'll get more bang for your buck by spending as much on speakers as on the amp.
I have an integrated tube-type Decware amp that puts out 3.4W per channel. (Actually, it can put out 7W per channel, but the way I've got the four output tubes switched around, it only puts out 3.4W.) With my full-range Fostex speakers, I never have the volume control turned up more than about 1/3.
3/6/2006 8:00:06 PMJK(37526:37519)
Thanks for the suggestions everyone. I might try this design, i want to expirement with it a little. But i also have close to every thing i need for it, i have a 350-0-350 x-former, and the 57 tube, i might try to use the 47 tube from the chasis, and triode conect it, be cause i have the field coil speaker for it. The parts came from an old wood radio that literaly fell apart, it had been wet a few too many times. So this seems like a good option to use parts from my junk box. Thanks for all of the suggestions, i might have to try some other designs to hear the differences.
JK
:One of my favorite triode output amplifiers to build was this one: http://www.nostalgiaair.org/PagesByModel/292/M0010292.pdf
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:It was one of the first amplifiers that I ever built. I built it when I was 15 from the schematic of an empty phonograph cabinet. I still have this amplifier and the cabinet. I wish I could find pictures of the inner workings so that I could refurbish it. I have yet to see another one like it. The amplifier is superb, though, with plenty of power. A transformer can be found at www.tubesandmore.com. The volume control network is for a high output crystal cartridge. A conventional 1 to 3 meg volume control will work fine (eliminate all the parts given in the original network, save the tone control, though I think a 1 meg would be better for the tone control..experiment with condenser values from .002 MFD to .01 MFD), with a .02 MFD condenser going to the grid of the #57. In mine I eliminated part #11. You can play around with the #3 value as well as the #2 value. I left #2 alone with a .01 MFD for #3. This produced some very pleasing negative feedback, but come to think of it, #2 is a rather high value. With such a high value for #3, #3 was acting more like a tone muting condenser by passing through #2. Anyway, experiment with those values if you ever build this amplifier. The 2A3 has become quite expensive. The dual plate type is what I used, though, with much success. This amplifier has amazing power and tonal quality.
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:Thomas
3/6/2006 8:28:32 PMThomas Dermody(37529:37526)
If you're going to use a #47 tube, you might as well pentode connect it. This will give you more power. If you want a negative feedback circuit that I think works really well, let me know. Remember to connect B- through a bias resistor to the center tap of the 2.5 volt supply. If you don't connect to the center tap with a filamentary type tube, you'll have lots of hum with the AC filament supply. If wired properly, the amplifier will be dead silent. My 2A3 amplifier was dead silent except when I fed some good music through it. I used a 1,750 ohm resistor in place of the original 1,800 ohm field coil. Also be sure to use the cathode bias resistor from your radio. The 2A3 resistor's value is probably different, and will produce distorted audio if not the correct value. You can use the 2700 ohm value for the #57 cathode bias resistor, as shown in my schematic, though, because you'd be using the same tube for your amplifier. My schematic is a bit confusing. That weird grid thingie that surrounds the plate is actually the 2nd grid, not the 3rd. The 3rd should be connected with the cathode. The 2nd should be connected to B+ through the resistor as shown in the diagram.
Thomas
3/7/2006 10:05:53 AMRMeyer(37551:37519)
Change 14 to the recomended 800, increase 8 to 100mfd and consider placing a humbucking pot across 1 and 4 on the 2A3, see the schmatic at angela.com SE2a3
Slip in a good choke for the field coil, Hammond 12H@150 ( $35), a Hifi out put Edcor CXSE25-8-2.5K ($79)(its made in the USA!) , use a good speaker, Sica or Jensen Sensitivity@1W, 1m 98dB ($55) and this amp will exceed your wildest expectations. 2A3s are getting up there $45+ for NOS, you can use a 6a3 and they are cheap, until the audio nuts all figure it out. These are new prices all this stuff is out there used for a fraction.
3/7/2006 10:36:54 AMThomas Dermody(37552:37551)
6A3 would probably be a better idea, too, since 6.3 volt center tapped transformers are readily available.
Thomas
3/7/2006 10:46:53 AMThomas Dermody(37553:37552)
You do not need a hum bucking pot for the 2A3 (or 6A3), though. If you use a center tapped filament transformer, connecting B- to the center tap through the cathode bias resistor works well. My amplifier is dead silent. Also, though 800 ohms and 100 MFD may work better, I used 750, as per the schematic, and as per most tube manuals of the period, and it really kicks butt. Experimentation may prove that 800 is better, though. I don't know as I haven't tried it. All I know is that my amplifier could easily come close to one 20 watt channel of my dad's SX-440 Pioneer stereo. I know that my amplifier isn't putting out 20 watts, but whatever it is putting out is very strong. It is an amazing amplifier.
For the #57 tube, if you wish to use a 6.3 volt set-up, the 6U7G (octal), or the 78 or 6D6 (6 pin standard) will work well in place of the #57. Angela's schematic looks interesting, though. Perhaps those two driver triodes would work better. Not sure. I'm partial to my #57 tube simply because it looks and sounds so great, but there are always other options.
Thomas
3/7/2006 2:29:51 PMRMeyer(37563:37553)
2.5v trannys, used anyway, are getting harder to find.Hammond still sells them but there goes the budget, 6.3v trannys with 5v for the rectifier are all over the place on ebay. That design on the Magnavox A-501B is very versatile. You could build it for under $75 with odds and ends or take it all the way to Hifi for under $200. Start with a strong tranny, built a pair on the one power supply, plug a cd player into it and be prepared to be impressed.
3/7/2006 3:18:38 PMThomas Dermody(37564:37563)
You can find a power transformer with two 2.5 volt windings at www.tubesandmore.com. Has a 350 volt B winding. However, I do agree that it might be better to build with a 6.3 volt filament supply (use a 6A3, a 6D6, and a #80). This gives you much more flexibility. I, too, use a CD player to feed my amplifier since I don't have the original phonograph guts. It has a ton of bass. Really smooth sound, too.
Thomas
3/7/2006 5:11:21 PMJK(37573:37564)
I have all of the stuff for this radio, The chasis i have was from a silver marshall radio, this belmont was close though, i couldn't find my model under silver marshall. I couldn't repair the damage on the old raio, it had been wet from being stored in a shed, and it had some thing dropped on it, the rf, if X-formers had opens, so i figure i might have to do a little rewiring and just use the the 57, and 47 part of the circuit next to the power supply. It might be simple, and maybe later try a triode amp, and build it from scratch. Otherwise i have everything, i think, to build just the output section of this radio, or maybe one like it. I don't have any other power tubes except for the 47 and a 12V6gt. Now the only problem is finding time between school and work.
Thanks for all of the suggestions. Your help with my questions about tube circuits is very helpful. Thanks again. JK
3/7/2006 5:12:55 PMJK(37574:37573)
forgot the schematic:
http://www.nostalgiaair.org/Resources/091/M0002091.htm
3/8/2006 11:18:20 AMThomas Dermody(37597:37574)
In my opinion, 2A3s are much more powerful than 47s (possibly due to some of them having a dual-triode parallel assembly in place of the original single triode). They also are a bit smoother sounding than 47s. If you're going to use #47 tubes, I strongly suggest that you build for push-pull. Then purchase a universal push-pull output transformer that is capable of 10 watts. For phase inversion you can either purchase another #57, or you can simply tap the phase inverted signal off of the screen grid of the 47 that's fed from the original 57. If you want details on this, ask. You can also take a look at Crosley's model 1117. Works very well if balanced correctly. I've used this method many times. Some will claim that it isn't quite real push-pull. It sounds much better than single ended output. What it is capable of doing is having two tubes out of phase with eachother, which cancels distortion. Even though the second #47 is taking its signal from the first, which might be distorted, since they are both out of phase with eachother, the sound balances.
Also, a negative feedback system (easy to construct) will add to the listening pleasure. You can call this a mid-range control. For the treble control you can use a .0005 MFD(or there-abouts) condenser on the plate of the #57 with a 1 meg potentiometer. For bass there are active filters which you can design. Perhaps someone can point you in the right direction for one of these. A passive control that works well, though perhaps not as well as an active one, simply uses a 3 meg potentiometer in series with a 470K resistor. The 470K resistor is connected to the 1st grid of the #57. The other ends of both of the mentioned potentiometers are connected to B-.
Thomas
3/8/2006 12:25:40 PMRMeyer(37598:37597)
:In my opinion, 2A3s are much more powerful than 47s (possibly due to some of them having a dual-triode parallel assembly in place of the original single triode). They also are a bit smoother sounding than 47s. If you're going to use #47 tubes, I strongly suggest that you build for push-pull. Then purchase a universal push-pull output transformer that is capable of 10 watts. For phase inversion you can either purchase another #57, or you can simply tap the phase inverted signal off of the screen grid of the 47 that's fed from the original 57. If you want details on this, ask. You can also take a look at Crosley's model 1117. Works very well if balanced correctly. I've used this method many times. Some will claim that it isn't quite real push-pull. It sounds much better than single ended output. What it is capable of doing is having two tubes out of phase with eachother, which cancels distortion. Even though the second #47 is taking its signal from the first, which might be distorted, since they are both out of phase with eachother, the sound balances.
:
:Also, a negative feedback system (easy to construct) will add to the listening pleasure. You can call this a mid-range control. For the treble control you can use a .0005 MFD(or there-abouts) condenser on the plate of the #57 with a 1 meg potentiometer. For bass there are active filters which you can design. Perhaps someone can point you in the right direction for one of these. A passive control that works well, though perhaps not as well as an active one, simply uses a 3 meg potentiometer in series with a 470K resistor. The 470K resistor is connected to the 1st grid of the #57. The other ends of both of the mentioned potentiometers are connected to B-.
:
:Thomas
3/8/2006 12:25:44 PMRMeyer(37599:37597)
:In my opinion, 2A3s are much more powerful than 47s (possibly due to some of them having a dual-triode parallel assembly in place of the original single triode). They also are a bit smoother sounding than 47s. If you're going to use #47 tubes, I strongly suggest that you build for push-pull. Then purchase a universal push-pull output transformer that is capable of 10 watts. For phase inversion you can either purchase another #57, or you can simply tap the phase inverted signal off of the screen grid of the 47 that's fed from the original 57. If you want details on this, ask. You can also take a look at Crosley's model 1117. Works very well if balanced correctly. I've used this method many times. Some will claim that it isn't quite real push-pull. It sounds much better than single ended output. What it is capable of doing is having two tubes out of phase with eachother, which cancels distortion. Even though the second #47 is taking its signal from the first, which might be distorted, since they are both out of phase with eachother, the sound balances.
:
:Also, a negative feedback system (easy to construct) will add to the listening pleasure. You can call this a mid-range control. For the treble control you can use a .0005 MFD(or there-abouts) condenser on the plate of the #57 with a 1 meg potentiometer. For bass there are active filters which you can design. Perhaps someone can point you in the right direction for one of these. A passive control that works well, though perhaps not as well as an active one, simply uses a 3 meg potentiometer in series with a 470K resistor. The 470K resistor is connected to the 1st grid of the #57. The other ends of both of the mentioned potentiometers are connected to B-.
:
:Thomas