Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: okguitarman on June 22, 2016, 05:37:29 pm
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What will be the difference in tone if I use 6L6's in output stage? Also, if I use 360-360 power trans. will higher voltage on plates change tone?
I would like to convert this amp to 5E3 but use 6L6's
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You can slap a 6L6GB in there and see what you think? :dontknow:
It will sound different, only you will know if you like the tone better.
It should be cleaner with the 6L6. :icon_biggrin:
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OK thanks
Ill just stick to the 5E3 6V6's and get a trans. love the sound.
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It wouldn't hurt to try the 6L6 to answer your 1st question.
Then you will know for sure.
I'm using these little 6V6 OTs with my metal 6L6s at 250V B+ and liking the cleaner slightly more powerful sound.
I'm even experimenting with an EL34 circuit using my 6V6 SE OTs.
The 6L6 is supposed to give about 6.5W and the EL34 about 9W at 250V.
They would probably sound better with a beefier more expensive OT,
but I've got a number of these little OTs and they seem to be working fine with the bigger tubes. :icon_biggrin:
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You said "5E3" (tweed Deluxe) but I only see one output tube (like a tweed Champ).
Which amp circuit did you want to build?
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Good question HBP. What he has drawn is not a 5E3 or a 5F1
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Like HBP says, your schematic shows more of a SE champ.
You list the voltage as 402 on the schematic, that should produce about the right dc voltage for a 6V6 or 6L6, we have no idea what the PT spec's are...?
My suggestion would be, leave what you have alone, run the either tube you want but keep an eye on the PT, if it gets hot using the 6L6 don't use it, warm is OK, hot no good. The heater current for a 6L6 is about twice what a 6V6 wants.
Raise that cathode bias resistor, to around 750 ohms. That 470 ohm is running the power tube most likely too hot. You can go as high 1K, you may like that sound better. That 6V6 is cooking with the higher wall current these days, keep an eye on the 6V6 plates, if they glow red just raise that resistor. Use 5 a watt for a 6V6 or 10 watt for 6L6.
al
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You said "5E3" (tweed Deluxe) but I only see one output tube (like a tweed Champ).
Which amp circuit did you want to build?
I'm not good with the Fender names and numbers. :w2:
I just took a quick look at the circuit posted, and parroted the you can swap in a 6L6 in that basic 12AX7 6V6 SE circuit.
If you did like the tone better, like dude suggested I'd seek to optimize that sound with a bias resistor change. :icon_biggrin:
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Sorry Guys, I was wanting to convert to 5e3 I'm running one 6L6GC in it now
I wasn't very clear!
5E3 circuit 6v6 vers. running 6l6s
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I Have no info on trans. but it runs very cool with one 6l6GC wondering would it handle two 6l6s or should I go with 6v6s?
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Trans.
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I Have no info on trans. but it runs very cool with one 6l6GC wondering would it handle two 6l6s or should I go with 6v6s?
Plug in the pair of 6L6's, and use a meter with clip-on leads to check for 6.3vac at your heater pins. For simplicity, connect one lead per side of the heater wiring (this will also avoid the "why am I getting 3.15vac" question when you measure from one pin to ground). Switch the amp on.
If you read substantially-near 6.3vac and don't let out any magic smoke, you're probably done.
If you just plug in 6L6's, you may hear a slightly cleaner sound and/or a different break-up from using 6V6's. My opinion is much of this is due to the differences in what bias voltage/idle current the 6L6's will land at, plus some contribution from the slightly-different shape of the 6L6's characteristic curves. I'm betting the 6L6's will idle at a higher current, which you will observe as a higher voltage across the cathode resistor, perhaps something like going from 19v across the cathode resistor to 28v.
That higher bias voltage also means a bigger signal required to drive the 6L6 to full clean output power. You fully drive an output tube when the incoming signal peak equals the bias voltage. So that might be like going from a 19v peak signal to fully-drive 6V6's to a 28v peak signal to fully-drive 6L6's. Since the driving signal voltage needed to be bigger, that probably equates with you having to turn the volume control higher. I think many misinterpret this as "more headroom" because "the amp stays clean to a higher volume knob setting." I'm not sure many/any of them used a SPL meter to see if the limit of clean output with 6L6's actually got more speaker-volume into the room.
Power = Voltage * Current. If you want the amp to kick out more actual power, you need to either raise the supply voltage, or lower the output transformer (OT) primary impedance (which then allows more current for the same voltage swing), or both. Fender often kept supply voltage similar across amp models and halved the primary impedance to double the current. The OT core would need to be bigger to pass the additional power, down to the same low frequency, at the same amount of distortion. However, sometimes the power handling ability of the OT is purposely restricted (http://www.victoriaamp.com/understanding-your-output-transformer-part-one-by-mark-baier/) for sonic effect, which may also explain why some modern clones sound big & bold, but maybe also "too clean" or "too hi-fi". Unfortunately, we often don't know core weight, as well as the stack size to get a good handle on what a given OT will sound like.
And the power transformer would need to be able to supply this additional current. We don't know the capabilities of your power transformer, but it seems sizeable. You might clip meter leads from the high voltage center tap to one side of the high voltage winding, and measure a.c. volts at idle and while you're cranking the amp flat out. If the voltage drops significantly, it could indicate that the amp is attempting to draw more current than the transformer can deliver.
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thank you!
Dang that was so much info and I'll let you know how it goes.
I'
I'll try 6L6's first. in a 5E3 circuit with some tweaking.
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I am probably missing something here but are we not talking about converting a single ended design to a push pull ???
If that is the case then a SE transformer will not work at all. I have the flu and have not read the thread in detail.
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You're not missing anything.