I'm starting to
I'll try both ways. Thanks!
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Moved to Instrument & Amps per forum policy - lots of help here for building guitar amplifiers.
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Thanks Kevin
I'll try both ways. Thanks!
I think I'm starting to understand. I already ordered the transformer without 5V taper so I'll go ahead with the plan. I can always use most parts for another build. Thanks
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Moved to Instrument & Amps per forum policy - lots of help here for building guitar amplifiers."
Thanks Kevin
It's easy to buy parts that are almost right when you are new to the hobby. I once built an amp and the b+ was much too high, red plating the 6v6s, and I tried this and that for a while, before I just bought the correct power transformer for the project. Now I got an amp that works correctly, and another PT for another project.
Have you actually built both? In my experience I have not found the above to be true.
2nd thread where you've come across as difficult. most of us are here to learn. maybe you should try twitter.
You know the common wisdom that says tube amps have rounded clipping and solid states hard clipping? Mainly by people that read stuff on the web but have not sat in front of an amp with an oscilloscope. When people post this I respond as I would rather they know what is real and what is fanciful. I read your post and thought to myself this is not my experience with a Champ styled amp with SS rectifiers. If not agreeing with you on this is being difficult then I guess I am. But I do not do it for fun, I have better things to do. I only commented as people do come here to learn and I think your version of single ended amps is wrong and that they are not boring if built with minimal filtering (yummy, more hum) or a stiff supply. That they do not need a tube rectifier to sound like a Champ.
"The 6V6GT is only rated for a maximum of 315v on the plate." Maybe, but many many guitar amps have gone way over this limit, do not worry about it. 350-360-370v is fine.
"This is partly due to the sag of the 5Y3 rectifier and the high B+ voltage applied to the 6V6" SE cathode bias amps have no sag, current draw is almost constant. 5Y3 will give a voltage drop where diodes will not.
"This is partly due to the sag of the 5Y3 rectifier and the high B+ voltage applied to the 6V6" SE cathode bias amps have no sag, current draw is almost constant. 5Y3 will give a voltage drop where diodes will not.
I'm waiting for the components to arrive. I'll go whit the plan and see how I like it. A sort of Champ between 5F1 and aa764. Solid stated diodes with Hammond 269EX. A bit more filtering but not much to start.
I'm not sure about diode configuration. The Fender Twin has six diodes in a configuration I'm not familiar with. Is the classic four diode bridge good for this?
I'm not sure about diode configuration. The Fender Twin has six diodes in a configuration I'm not familiar with. Is the classic four diode bridge good for this?
No, the transformer is a center tap which needs a full wave configuration same as the Twin. The Twin just has three diodes in series to give the rectifier a greater voltage capability.
https://www.electronics-tutorials.ws/diode/diode_6.html
https://www.electronics-tutorials.ws/diode/diode_6.html
I see. Also the voltage would be too high with the bridge. I'm using a choke, and some extra capacitance. I'll use 40-20-20. You seem to have experience with this setup. How does it look to you? Thanks in advance!
Manel
I have bought output transformers but not power transformers so I can not give experience with the 269EX. But looking at the datasheet for the transformer I would think it would work well enough with SS diodes.
https://www.hammfg.com/files/parts/pdf/269EX.pdf?v=1697661948
The open circuit voltage is 215.7 on one side, multiply that by 1.414 gives 304V. The dc resistance from red to red is 272.5 ohms, half that to the center tap, 136R. So say the amp draws 40 mA at idle, the secondary loss does not follow Ohm's Law as the current flows for a shorter period of time but it does give our minimum loss. 136R x 0.040A = 5.5V, So say the amp will run 290-300V. This is lower that the Blackface voltages, a little low for a 5F1 which has 340V on the schematic. You could still run a 6V6 with it as the datasheet shows it will make 5W. An alternative would be to run an EL84. Both cases should have a 5k output transformer.
https://www.hammfg.com/files/parts/pdf/269EX.pdf?v=1697661948
The open circuit voltage is 215.7 on one side, multiply that by 1.414 gives 304V. The dc resistance from red to red is 272.5 ohms, half that to the center tap, 136R. So say the amp draws 40 mA at idle, the secondary loss does not follow Ohm's Law as the current flows for a shorter period of time but it does give our minimum loss. 136R x 0.040A = 5.5V, So say the amp will run 290-300V. This is lower that the Blackface voltages, a little low for a 5F1 which has 340V on the schematic. You could still run a 6V6 with it as the datasheet shows it will make 5W. An alternative would be to run an EL84. Both cases should have a 5k output transformer.
I appreciate you help, but that confuses me. In your setup calculations are you using only one side of the high output ? Why?
I'm just learning the difference between "full wave rectifier" and "full wave bridge rectifier". With the first I can use both sides and the center tap of the high voltage output. With the second option (I think, and that's why I'm asking for help) I could use either side or both without the center tap. Ultimately I'm going to try all options until I find the one gives me what I need. Which is around 300V. I prever using whole transformer instead of one side. I started this thread asking about using the 5E3 transformer for the 5F1 and I'm deviating quite a bit, so thanks for your patience.
Manel
I'm just learning the difference between "full wave rectifier" and "full wave bridge rectifier". With the first I can use both sides and the center tap of the high voltage output. With the second option (I think, and that's why I'm asking for help) I could use either side or both without the center tap. Ultimately I'm going to try all options until I find the one gives me what I need. Which is around 300V. I prever using whole transformer instead of one side. I started this thread asking about using the 5E3 transformer for the 5F1 and I'm deviating quite a bit, so thanks for your patience.
Manel
It does not matter if it is half wave, full wave or bridge rectifier, the theoretical peak voltage is the same (ignoring rectifier losses). In half wave you have one diode and a single secondary winding. It only passes one half of the sine wave.
To use the bottom half of the wave we can use full wave rectification which basically flips the bottom half of the waveform. During the top half of the waveform the bottom diode isolates the bottom half of the winding.
So how do we calculate the voltage? The theoretical peak voltage of a sine wave is the RMS value times 1.414. The same is for the negative side but the voltage is - (RMS x 1.414). The load sees the two halves of the current going through the load in the same direction, so we have full wave pulsating dc. Both halves of the waveform puts out the same peak voltage. To make things easy we just calculate the one half of the voltage as the other half comes out to be the same value.
When you get further along (I am assuming you want to know more), we calculate the Push - Pull output of an amp in the same way. Since the two halves are doing the same job, just one inverted, we do our calculations for one half of the circuit as the other half would be the same. But that is getting ahead of ourselves. You get the same voltage with one half the transformer as with both halves. But you get double the voltage using the two halves when operating in full wave. We calculate the current for the one winding (half wave) and just double the result for both windings (full wave).
So you want to use the full wave circuit with two diodes.
Thanks Printer. I just got together a temporary setup to test voltages and I'm getting 380V with the bridge, choke and 6V6 and OT. I'll put together the whole thing this way before building the final project. I might want to go down to 350V or so with the MOSFET circuit. Then I'll check the sound and I might try the tube rectifier too if I'm not pleased with the end result. Thanks
Either I'm not understanding correctly or the above statement is not true:It does not matter if it is half wave, full wave or bridge rectifier, the theoretical peak voltage is the same (ignoring rectifier losses). In half wave you have one diode and a single secondary winding. It only passes one half of the sine wave.
"it does not matter if it is half wave, full wave or bridge rectifier,"
I tried both ways and the voltage with the layout shown above is 192V under load. The "bridge" layout gives me 380V
I just don't want to mislead anyone reading the above.
You have to keep in mind the transformer with a center tap is used with a full wave circuit using two diodes. If you ignore one half of the winding and only use one diode you will get the same peak voltage, you just get one pulse per one cycle of the sine wave rather than two. Using one side of the center tapped transformer you can also hook up a bridge rectifier to it and get the same peak voltage as the half wave circuit or the full wave circuit (other than an added 0.7V diode drop). You do get the same resultant waveform as the above although the current is reduced as having two windings means that the wire will be thinner and each winding provides less current. You can not connect the bridge rectifier across the center tapped transformer outer terminals and get the same voltage as from one terminal to the center tap. If you do use a bridge rectifier across the outer terminals you will get roughly double the voltage as the other connection schemes, as you found out. The center tapped transformer is not meant to be used with a bridge rectifier. But it can be used if you want double the voltage and roughly half the current compared to using the transformer in full wave operation.
Not true. There are two ways to use a center tapped xfmr with a bridge. One way is to ground the center tap to give a balanced +/- PS, as many solid state designs that use the OTL, SEPP topology require.
The other is to ground the (-) end of the bridge. You will then get two (+) voltages, with the center tap being at ~0.5Vbridge that's useful for providing a lower voltage for low level stages and screen supplies. The 814, for example, has operating points with VPP= 1250VDC and V22= 400VDC. Better to use the two voltage (also called "economy") PS and derive V22 from the 625V side.