Hello,
I would like to to turn a AA764 Fender Champ Amp, into a stereo one, by simply doubling the circuit, but keeping only one power supply.
Since it is a single ended, it gives with 2 6V6 with 14W power something around 40mA per tube, and 8 mA more for the screens if we consider 10% dissipation. For the triodes it would be a 1ma for each, so a total of 4ma.
It will be a total of 92mA and if we take in consideration rectification and filtering losses it will be 20% more, something arround 110mA where a 5Y3-GT can handle 125mA.
Question, since the current will double, the intended voltage are not the same, as I tried to simulate the PSU with PSU2 tool (PSUD2)
What would you do and which resistor values would you use?
Thank you 🙂
I would like to to turn a AA764 Fender Champ Amp, into a stereo one, by simply doubling the circuit, but keeping only one power supply.
Since it is a single ended, it gives with 2 6V6 with 14W power something around 40mA per tube, and 8 mA more for the screens if we consider 10% dissipation. For the triodes it would be a 1ma for each, so a total of 4ma.
It will be a total of 92mA and if we take in consideration rectification and filtering losses it will be 20% more, something arround 110mA where a 5Y3-GT can handle 125mA.
Question, since the current will double, the intended voltage are not the same, as I tried to simulate the PSU with PSU2 tool (PSUD2)
What would you do and which resistor values would you use?
Thank you 🙂
Doubling the amp circuitry will also double the total power consumption. You'll need either a second PSU of the same kind or a beefier one.
Best regards!
Best regards!
You will need another chassis large enough to hold two sets of components and stereo connectors/pots etc.
You cannot just turn a mono guitar amplifier into a stereo one.
You cannot just turn a mono guitar amplifier into a stereo one.
Hello,
-My transformer can handle 120mA so it should me ok
-I start project from scratch so i will use a princeton or deluxe chassis
-My transformer can handle 120mA so it should me ok
-I start project from scratch so i will use a princeton or deluxe chassis
One question. Why do you want to do this? 2) Shouldn't this be in Instruments and Amps?
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Hello,
I Want to do this to use my stereo effect pedal board. I ask the question in psu subject because it is all about feeding the amp. Am i wrong?
I Want to do this to use my stereo effect pedal board. I ask the question in psu subject because it is all about feeding the amp. Am i wrong?
True, but you might find more people who know guitar amps in the instruments and amps section.
If you play the guitar anything like I do, that poor Champ is pushed well out of class A as soon as you set the pedal board on KILL and dime the volume control. The peak currents are a bit beyond what's published in the data sheets. It also depends a lot on what your speaker is doing too. An 8 ohm speaker is not 8 ohms at all frequencies or operating conditions. Look for a transformer that's good for 150 mA at around 310 - 320 volts and has a 3 amp 5 volt winding. 2 amps or more on the 6.3 volt winding s OK.
There are two ways to do this, each result in the same problem, too much capacitance for a 5Y3 to absorb, it may spark out on power up.
All the resistors in the amp circuit itself will not change, copy what's in the schematic. There are two resistors that need to change, the 1K 1 watt and the 10K 1watt that are connected between the filter caps. To make the supply feed two channels, these resistors would need to be divided by two, so you would need a 510 ohm 2 watt, and a 5100 ohm 2 watt. The capacitor values need to be doubled, so they would all become 40 uF. The maximum value for the input cap on a 5Y3 is 20 uF.
The other way, which I prefer is to build two identical circuits including these power supply resistors and caps, joining them at the 5Y3, so one transformer and rectifier feed two of everything else. This also puts 40 uf on the 5Y3 tube which is twice the recommended value.
There are several ways to make these choices work. The simplest, which would only be valid if your power transformer can handle 3 amps on the 5 volt winding is to use a 5U4 rectifier. A 5AR4 can also be used, but these have a lower voltage drop and a different sound.
It is possible that the amp could work with only 20 uF for the input filter cap, but hum may be an issue.
You might get by with a 30 uF or so cap for the input filter if other measures are used to prevent arc over on power up. Adding a CL140 inrush current limiter in series with the HV CT on the power transformer, and maybe a CL90 in series with the primary and a silicon diode in series with each plate are known methods for improving the life of rectifier tubes that are somewhat overstressed.
If you find a suitable power transformer with a 4 amp or more 5 volt winding (rare) simply build two amps just like the schematic shows with two 5Y3's and feed them from one power transformer.
WOW Tubelab! Thank you for such detailed information.
I effectively read that 5Y3 rectifier would be not the good choice as the maximum cap is 20uF.
What if I choose the 5U4GB, i can go up to 40uF? JJ Electronic - 5U4GB
5U4GB can handle up to 3 amps.
What about the following transformer? It looks to be ok?
I effectively read that 5Y3 rectifier would be not the good choice as the maximum cap is 20uF.
What if I choose the 5U4GB, i can go up to 40uF? JJ Electronic - 5U4GB
5U4GB can handle up to 3 amps.
What about the following transformer? It looks to be ok?
Moving to Instruments & Amps..
If you set the pedal board on kill and dime the Champ volume, why not stereo effect after the existing single channel Champ does its thing to the guitar's sound?
You could boost the SPL to live club performance levels at the same time, very cheaply for clean amplification (these days) and put the remainder into the stereo speaker setup. Like adding a PA onto your Champ, through your existing stereo effects. Build an instrument level tap off the Champ's speaker terminals.
You could boost the SPL to live club performance levels at the same time, very cheaply for clean amplification (these days) and put the remainder into the stereo speaker setup. Like adding a PA onto your Champ, through your existing stereo effects. Build an instrument level tap off the Champ's speaker terminals.
May just be semantics -- or I didn't read it correctly 😱 -- the 5U4GB doesn't *handle* 3 amps, I believe that's what the filament requires.
Cheers
Cheers
Uh .. your mileage may vary, jjasniew, but I've had very little joy, if any at all, trying to take a direct out of a guitar amp -- over a number of different players and amps. Couple of times I was just SURE I had it all figured out, too.
Liked the other part of your tips, though.
Best Regards
Liked the other part of your tips, though.
Best Regards
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Thanks Rick and Jjasniew for your advices
Rick, yes I said handle but It is not correct. I was meaning, that it needs 5V, 3Amp. So I mean the transformer I choose seems to be ok.
Jjasniew, I am not sure to understand all your advices so let me reformulate:
-Make one mono stage, then a send return loop in stereo stage, to prevent "kill and dime" what does it mean? I understand that the pedal board level is to high so i would have a crap sound? Clean sound is very important for me as I always play clean, maybe sometime with a little crunch
-Better to keep the champ as it, and invest in a sound system for live performance? is that what you mean? Sorry my english is not enough english 😉
I want to build this amp for my living room. I will never play live performance as I don't practice out of my home.
Rick, yes I said handle but It is not correct. I was meaning, that it needs 5V, 3Amp. So I mean the transformer I choose seems to be ok.
Jjasniew, I am not sure to understand all your advices so let me reformulate:
-Make one mono stage, then a send return loop in stereo stage, to prevent "kill and dime" what does it mean? I understand that the pedal board level is to high so i would have a crap sound? Clean sound is very important for me as I always play clean, maybe sometime with a little crunch
-Better to keep the champ as it, and invest in a sound system for live performance? is that what you mean? Sorry my english is not enough english 😉
I want to build this amp for my living room. I will never play live performance as I don't practice out of my home.
>I want to build this amp for my living room. I will never play live performance as I don't practice out of my home.
OK, that changes things a bit. My suggestion was to move the stereo effect behind the single amp (guitar => mono amp => stereo processor => stereo amp/speakers), instead of in front of two Champs (guitar => stereo processor => two mono Champ amps) - regarding your sound architecture.
That may not sound best, as was pointed out, compared to two separate Champ amps.
Particularly for personal entertainment in your living room. I'd assumed you'd want / like to gain some power along with the stereo effect, to cut it playing in a club with a Champ; fit in sound level wise next to an acoustic drum kit - and other amplified instruments
Unsure why taking a attenuated signal off the speaker of some little warm tube amp doesnt work OK, maybe there's no way to do it (besides a mike) where you keep the speaker's sound character as well.
OK, that changes things a bit. My suggestion was to move the stereo effect behind the single amp (guitar => mono amp => stereo processor => stereo amp/speakers), instead of in front of two Champs (guitar => stereo processor => two mono Champ amps) - regarding your sound architecture.
That may not sound best, as was pointed out, compared to two separate Champ amps.
Particularly for personal entertainment in your living room. I'd assumed you'd want / like to gain some power along with the stereo effect, to cut it playing in a club with a Champ; fit in sound level wise next to an acoustic drum kit - and other amplified instruments
Unsure why taking a attenuated signal off the speaker of some little warm tube amp doesnt work OK, maybe there's no way to do it (besides a mike) where you keep the speaker's sound character as well.
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Many players, including myself sometimes prefer a dirty distorted sound for lead guitar. "kill" refers to setting everything on the pedal board for maximum boost, gain, or distortion. "Dime" refers to a US 10 cent coin, in this case it means to set all the knobs on "10." Playing this way will overdrive any amp by 10 to 20 dB in which case it is not a class A amp any longer, and the nice curves and math used to design the amp no longer apply.
In this case your amp will probably stay in or near class A most of the time so that the numbers in the tube manual can be used for estimating current demands.
The sound of the speaker, and even it's dynamic electrical characteristics reflected to the amp when it's cone is moving affect the overall "tone" of a guitar amp. There are resistive load boxes with some sort of "speaker emulation circuit" inside so that an amp can be cranked up full, then attenuated to a level for the house PA or a direct connection to a mixing board. These are all different and regarded as less than optimum by many guitar players.
Many years ago I spent some time trying to record the sound of a little 4 watt amp I made that used an open back 8 inch speaker. The best results were obtained with the amp and a mic in a closet that was stuffed with blankets and towels. Direct connection across the speaker was less than optimum, but deemed acceptable. Then I tried to quiet down the amp's sound by enclosing the speaker. Any attempt to make the amp mute also destroyed a lot of the amp's dynamic character. I wound up ripping all the paper off the speaker so that only the voice coil assembly remained. That was the worse possible combination.
Would it not be cheaper, and give you more flexibility, if you just build a second Champ? If you still have to buy a suitable chassis and power transformer, this could make sense. But ofcourse I don't know why you plan it like you do.
Tubelab, thanks for your add on. Effectively i play soul/jazz most of the time. (some kind of that, it is not me playing 1970s Silverface Fender Vibro Champ 1x10 Demo | Clean Tones, Jazz Tones, and Vibrato | Gibson Gits - YouTube)
I don't need recording, so the final output must be the amplifier for my use. I will certainly mount a 8ohm output transformer and a 10 inches speaker on each channel to get more presence.
I don't need recording, so the final output must be the amplifier for my use. I will certainly mount a 8ohm output transformer and a 10 inches speaker on each channel to get more presence.