Those will be some WARM resistors. I mean really HOT resistors. Probably looking at dissing 20-25Watts of heat that way. You want the power supply to have the lowest impedance (resistance) possible.
If you need a lower voltage, I would reccommend using a lower voltage tranny, less resistance (or a choke) and larger caps. This way you have good ripple control, some extra power reserve, and low impedance. For the driver stages you can use a larger resistor after the take off for the output tubes to drop the voltage since they don't draw as much current.
If you need a lower voltage, I would reccommend using a lower voltage tranny, less resistance (or a choke) and larger caps. This way you have good ripple control, some extra power reserve, and low impedance. For the driver stages you can use a larger resistor after the take off for the output tubes to drop the voltage since they don't draw as much current.
Lingwendil - sorry no updates yet - I'm still burying myself in the theory 
! Once I return to my home state where all my tools and electronic goodies are I will begin benchtop testing! I will be sure to post in detail as I'm sure I'll need as much help as I can get!
SGregory - thats what I was fearing while conversing with stalker earlier in the thread, he recommended using a transformer with at least 100 mA on the secondary and I am having a very hard time finding a transformer with that current rating and a low enough voltage. Very frustrating. The power supply design aspect is causing me the most trouble and dumb me thought it'd be the easiest part! How do i go about selecting the proper choke though?
Thanks!
! Once I return to my home state where all my tools and electronic goodies are I will begin benchtop testing! I will be sure to post in detail as I'm sure I'll need as much help as I can get!SGregory - thats what I was fearing
while conversing with stalker earlier in the thread, he recommended using a transformer with at least 100 mA on the secondary and I am having a very hard time finding a transformer with that current rating and a low enough voltage. Very frustrating. The power supply design aspect is causing me the most trouble and dumb me thought it'd be the easiest part! How do i go about selecting the proper choke though? Thanks!
I posted the 5F1 schematic as an example of a great power supply for SE guitar amps. Look at it, no resistor before B+ hits the OT and the tube's anode. There's a reason for this - great dynamics and "livelier" sound, but there's also a price to pay - a slight hum . With a proper layout it's not a big deal, I only hear it when the house is really quiet (at night). Anyway, I'm not a noise freak with guitar amps. I love making noises.
You'll want 250-315 volts at the first cap, so I'm afraid you'll have to look for another transformer. Another option is to use a tube rectifier, a 5Y3 will lower the B+ around 50 volts.
I have no problems answering your questions, I work at home so I take a lot of breaks.
EDIT: I've found this: Hammond 269 AX and BX.
Hammond Mfg. - "Classic" Power Transformer - (263-282 Series)
You'll want 250-315 volts at the first cap, so I'm afraid you'll have to look for another transformer. Another option is to use a tube rectifier, a 5Y3 will lower the B+ around 50 volts.
I have no problems answering your questions, I work at home so I take a lot of breaks.
EDIT: I've found this: Hammond 269 AX and BX.
Hammond Mfg. - "Classic" Power Transformer - (263-282 Series)
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SGregory-thanks for the suggestion, ill be sure to check them out
Stalker, that transformer looks pretty ideal, though I think I am a little confused on the concept of the center tap. I know that this will be connected to ground and that if I probe from the center tap to either of the HV leads, i should get around 125 volts (for the hammond transformer you posted). So does that mean I will have 125 volts going into the two diodes of the full wave rectifier I want to use or will i have 250?
Thanks!
Stalker, that transformer looks pretty ideal, though I think I am a little confused on the concept of the center tap. I know that this will be connected to ground and that if I probe from the center tap to either of the HV leads, i should get around 125 volts (for the hammond transformer you posted). So does that mean I will have 125 volts going into the two diodes of the full wave rectifier I want to use or will i have 250?
Thanks!
125-0-125V. But it won't work, voltage too high, sorry for that.
Tomorrow I will do a better search, I am a little busy right now.
An externally hosted image should be here but it was not working when we last tested it.
Tomorrow I will do a better search, I am a little busy right now.
There were actually two very different ideas using paralleled EL84 and 6v6 that were going on simultaneously. The original was a SE design using just 2 tubes in the final. This was going to be used as guitar amp that exploited the idea of (possibly) using switched pentode/triode modes.
I also introduced the idea of creating a paralleled EL84/6V6 PP design for audio reproduction. You may have seen the schematic I posted that was far from being a final design. I only put it up because Stalker requested I post my schematic. I don't think a schematic of the original SE guitar amp, (not PS), has ever been posted. I could be wrong.
It seemed to be the consensus that I should take my PP ball and go home because guitar amp enthusiasts already get too little attention.
I also introduced the idea of creating a paralleled EL84/6V6 PP design for audio reproduction. You may have seen the schematic I posted that was far from being a final design. I only put it up because Stalker requested I post my schematic. I don't think a schematic of the original SE guitar amp, (not PS), has ever been posted. I could be wrong.
It seemed to be the consensus that I should take my PP ball and go home because guitar amp enthusiasts already get too little attention.
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There are enough people here that can help with both amps. The key is to build the power supply around what is required by the amplifier. So that is where the discussion should focus on. The basic quesions are What Voltages are needed, what currents are needed, what impedance is needed (based on amp topology), and then finally what kind of ripple is acceptable.
It seemed to be the consensus that I should take my PP ball and go home because guitar amp enthusiasts already get too little attention.
Youngb4 started this thread. He wanted to build a guitar amp blending two different output tubes. You came up saying this was already done in hifi. Good to know.The idea is too weird for most people here. They have no way of knowing how that amp might sound and if it's worth the effort to buy the parts, study the schematic, etc. No wonder the lack of interest. Plus this thread is filled with newbie (Zzzzz) questions, so this wasn't the right place to post your schematic.
I have to say that I have a SE EL84 amp, a SE 6V6 amp and a 6V6/EL84 SE amp in one chassis. You only have to change the impedance of the OT with a switch and unplugged one tube or none. How does it sound? I like best the el84/6v6 combo. Maybe it's the novelty. It sounds a bit like you said your amp sounded: mixed sonic qualities of both tubes.
SGregory, youngb4 needs 250-315 volts after rectifying the PT secondary voltage, 100mA of current and a 2A 6,3 winding.
125-0-125V. But it won't work, voltage too high, sorry for that.
An externally hosted image should be here but it was not working when we last tested it.
Tomorrow I will do a better search, I am a little busy right now.
250*1.414 = 353.5V
If the only load is 27mA on the output of the filter, and there is 1K5 ohms in series, you will drop 40.5V through them.
353.5-40.5 = 313V
313V B+ - 14VBias = 299V. Looks pretty good to me as both the 6V6 and EL84 data sheets show bias with 300V B+.
If it is an SE design I can see 27mA being ok.
If it is PP, you need twice 27mA, but you could use a second 500R/cap output to drive the second tube and avoid a some additional voltage drop. Changing the first resistor to 500R also keep you at the same B+.
Your 6V filament supply will however be high as you will have :
6.3*1.414=8.9V
Minus two diode drops in the bridge will leave you with around 7.4V which is way too high for 6.3V filaments.
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Edcor XPWR104 <$50.00 ea. 250Vct at 125mA with 6.3V at 2A. Use a CLC. The first cap being set to hit voltage. The second cap then could be 100uF motor run or a combo motor run electrolytic to get higher resivour values. If we need to drop the voltage lower then some resistance can be added before the first cap. 100R for 10V (100mA makes the math easy ;-) )
The choke can be a Hammond or Allied in the neighborhood of 5H or more. I usually have Jack at electraprint wind my chokes as the price is competative and he can make anything you want with or without bellends. Just DON'T ask him what the final DCR will be.
Set PSUDII up to use full wave rectification with an RCLC filter and a CCS load. Initially set the R to 0.1Ohm. The DCR of the choke should be 150Ohm as an initial estimate. Then play with the first cap to get the required voltage at the current source. Let me know if you want me to model it.
The choke can be a Hammond or Allied in the neighborhood of 5H or more. I usually have Jack at electraprint wind my chokes as the price is competative and he can make anything you want with or without bellends. Just DON'T ask him what the final DCR will be.
Set PSUDII up to use full wave rectification with an RCLC filter and a CCS load. Initially set the R to 0.1Ohm. The DCR of the choke should be 150Ohm as an initial estimate. Then play with the first cap to get the required voltage at the current source. Let me know if you want me to model it.
Gimp,
Remember you will have loss across the choke, or if you omit the choke and use a RCRC filter wyou will have voltage drop across the second R. Vct * 1.4 is for a full CLC. you can set it for any value from 1 to 1.4 depending on how big the first C is.
6.3V is reported as Vrms. You won't rectify that, unless you want to heat DC, then a simple regulator will bring voltage in check.
Remember you will have loss across the choke, or if you omit the choke and use a RCRC filter wyou will have voltage drop across the second R. Vct * 1.4 is for a full CLC. you can set it for any value from 1 to 1.4 depending on how big the first C is.
6.3V is reported as Vrms. You won't rectify that, unless you want to heat DC, then a simple regulator will bring voltage in check.
The schematic I posted was just an example of what B+ voltage he might get out of a Hammond 269AX considering he was taking the B+ at the FIRST cap.
Guitar amp here. The amp will draw around 85mA. The easiest way is to do a CRC filter and drop around 40 volts so the EL84 gets 310 volts.
Go for the Hammond's or Edcor's. Good el84's can take 340 volts anyway, I just wanted to stay in the safe side, but with good tubes there will be no problem.
Guitar amp here. The amp will draw around 85mA. The easiest way is to do a CRC filter and drop around 40 volts so the EL84 gets 310 volts.
Go for the Hammond's or Edcor's. Good el84's can take 340 volts anyway, I just wanted to stay in the safe side, but with good tubes there will be no problem.
WOW so much to respond to so soon! Thank you for all your input! (esp. stalker and Sgregory for the power supply and transformer recommendations)
Just to clear a few things up for all newcomers to the thread (and to refresh some memories!) This will be a single ended guitar amp that features a 6v6 and el84 paralleled for the power amp. I'm thinking the preamp will consist of at least one 12ax7 with the triodes paralleled ( i posted a new thread about how i am thinking about doing this so check that out too if you want!) possibly two 12ax7s (each with paralleled triode stages) I don't really know the exact voltages that I want at the preamp and power amp since I am new to tube audio design I was thinking around 275 to 315 on the power tubes and 210-250 on the 12ax7s, but thats why I wanted to post so you guys could help me get this figured out! I am working on drawing up a detailed schematic and hopefully will be able to post it soon so you all can look over it and make some comments and recommendations! Like I have said before - I am learning a great amount of information from everyone that posts and I greatly appreciate it!
Just to clear a few things up for all newcomers to the thread (and to refresh some memories!) This will be a single ended guitar amp that features a 6v6 and el84 paralleled for the power amp. I'm thinking the preamp will consist of at least one 12ax7 with the triodes paralleled ( i posted a new thread about how i am thinking about doing this so check that out too if you want!) possibly two 12ax7s (each with paralleled triode stages) I don't really know the exact voltages that I want at the preamp and power amp since I am new to tube audio design I was thinking around 275 to 315 on the power tubes and 210-250 on the 12ax7s, but thats why I wanted to post so you guys could help me get this figured out!
I am working on drawing up a detailed schematic and hopefully will be able to post it soon so you all can look over it and make some comments and recommendations! Like I have said before - I am learning a great amount of information from everyone that posts and I greatly appreciate it!man this is making me tear my hair out! I'm about ready to start ordering parts for benchtop testing and the only thing holding me back is the dang power supply. I've been fooling around with psudII for days and just getting more and more frustrated. Stalker and SGregory, you both have been tremendously helpful and I don't want you to think that I haven't been paying attention. The hammond 269AX or edcore xpwr104 will def. be my best options as days of searching hasn't turned up anything else. I'm just going to list the voltages that I think I need and hope someone can guide me in the design of the power supply so I can do this on my own in the future.
The transformers are each 250V secondaries (or 125-0-125) and have a current rating of atleast 115 mA (my amp will use atleast 85 mA (thanks stalker))
B+1 (voltage to 6v6 and el84 plates) = 300v
B+2 (screen grid voltage for 6v6 and el84) = 250 (tho ive been told they can handle more)
B+3 (voltage to 12ax7 plates) = 200 to 220
When I try and achieve this in psudII using a CRCRCRC filter, my voltages come out to about where I want them, but my resistors seem to be passing large amounts of current which means they'll have to have extraordinarily high power ratings (around 15 to 20 watts) I mean I have poured over tons of schematics of similar amps and all seem to accomplish what I want using resistors rated no higher than 5 watts and with only 3 RC filters. So there is clearly something I am doing wrong here because I don't think it should be this complicated.
Can anyone point me to or show me a simple way to walk through the design of one of these things?
Thanks to all very much in advance
The transformers are each 250V secondaries (or 125-0-125) and have a current rating of atleast 115 mA (my amp will use atleast 85 mA (thanks stalker))
B+1 (voltage to 6v6 and el84 plates) = 300v
B+2 (screen grid voltage for 6v6 and el84) = 250 (tho ive been told they can handle more)
B+3 (voltage to 12ax7 plates) = 200 to 220
When I try and achieve this in psudII using a CRCRCRC filter, my voltages come out to about where I want them, but my resistors seem to be passing large amounts of current which means they'll have to have extraordinarily high power ratings (around 15 to 20 watts) I mean I have poured over tons of schematics of similar amps and all seem to accomplish what I want using resistors rated no higher than 5 watts and with only 3 RC filters. So there is clearly something I am doing wrong here because I don't think it should be this complicated.
Can anyone point me to or show me a simple way to walk through the design of one of these things?
Thanks to all very much in advance
Forget about psudII, use Ohm's law. This program will do all the calculations for you:
Electronics 2000 | Downloads - FREE Software
Electronics 2000 | Downloads - FREE Software
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