Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: worth on May 28, 2011, 09:12:43 am
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Just built a parallel 6L6 5F2-A with trem for a friend. Sounds really nice , but he'd like just a bit more volume when playing with a drummer. Would bypassing the tone control produce any noticable boost ? BTW... he's using a 1 -12 cab with it.
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Since there is only a simple tone control the removal of it will not increase the volume IMO.
Use the preamp calculator to set more gain in first amplification stage:
http://ampbooks.com/home/amplifier-calculators/cathode-capacitor/ (http://ampbooks.com/home/amplifier-calculators/cathode-capacitor/)
/Leevi
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I'll try 220K for the plate load resistors.
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Why not try putting the NFB on a switch. That should increase the gain.
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Those amps have there limits, a little more volume.... :BangHead:
Have him use a speaker with 100DB SPL and he'll get his little more volume.
Some people don't understand it's the speaker most times. Using a 97db speaker as opposed to a 100db speaker means a lot of volume change and it's exponential.
Ask him what speaker he is using and whether it's an open back or closed back cab. A closed back cab will have a perceived lose of volume until you stand further away, it will beam the sound more directionally. Off axis there will be a big loss of sound.
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Why not try putting the NFB on a switch. That should increase the gain.
Good point! And you'll get a more fat sound.
/Leevi
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Right !! NFB switch!! I forgot about that option.
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Those amps have there limits, a little more volume.... :BangHead:
Have him use a speaker with 100DB SPL and he'll get his little more volume.
Some people don't understand it's the speaker most times. Using a 97db speaker as opposed to a 100db speaker means a lot of volume change and it's exponential.
Ask him what speaker he is using and whether it's an open back or closed back cab. A closed back cab will have a perceived lose of volume until you stand further away, it will beam the sound more directionally. Off axis there will be a big loss of sound.
That, or switch to a 2X12.
Gabriel
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Put a switchable 25uf cathode bypass cap on the 1.5k cathode resistor on second stage of the 12ax7.
Cheap and effective boost.
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Hi worth, This is what i did to my TOS and Champ/Princeton amps. Its the fun switch,flickit and the volume/gain goes up and you let RIP. :guitar1
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but he'd like just a bit more volume when playing with a drummer. Would bypassing the tone control produce any noticable boost ?
Hell yes there's a definite noticeable boost! Any time a tone control and/or stack & vol control are bypassed, you will notice a fairly large boost in signal drive/output.
Now, you also need to know this - w/out any filtration w/ the lower mids and bass frequencies you'll get muddiness at higher volume levels. All you need to do is find your happy spot w/ the coupling cap and/or cathode bypass cap to address this and you'll be fine. I recommend a .002uF coupling cap and a 2.2uF cathode bypass cap as a starting point. These may very well be perfect as I use them many times.
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If you turn the tone pot to the other end you'll have a 1M resistor towards the ground
which is almost the same thing if you remove the tone pot. I don't think you'll boost
anything but try I can be wrong.
http://www.kbapps.com/audio/schematics/tubeamps/fender/princeton5f2a.html (http://www.kbapps.com/audio/schematics/tubeamps/fender/princeton5f2a.html)
/Leevi
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Another thing you could try but I'm not sure if it will have any effect.
Change the 220k resistor from the power tube grid to 1M.
/Leevi
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Have him use a speaker with 100DB SPL and he'll get his little more volume.
Some people don't understand it's the speaker most times. Using a 97db speaker as opposed to a 100db speaker means a lot of volume change and it's exponential.
Yep! Yep! Yep! Speaker makes a HUGE difference IMO. My last (5F2a) build was mated to a 15" Legend 1518 with a 102+ db sensitivity, and it had lots of volume.
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Put a switchable 25uf cathode bypass cap on the 1.5k cathode resistor on second stage of the 12ax7.
Cheap and effective boost.
Doesn't that boost the gain of the second stage AND effectively ground the NFB at the same time?
I'm not criticizing the idea - just want to make sure I understand all of the effects.
Chip
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> parallel 6L6 5F2-A
5F2-A tone control has very little effect in the center.
Killing the NFB will get the same Power with softer fingering, but he can probably SLAM the final stage now, it won't get more Power.
I would not expect a 5F2-A, even dual-6L6, to compete with a drummer unless very well optimized for Power and used with a BIG LOUD speaker such as a hot 4x10". If you can't get a less-loud drummer, then drop in another small tube and wire the two 6L6 in push-pull.
What is the voltage, current, and load on the two 6L6?
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Plate V is around 450.. SS rectified , cathode biased at around 90% plate dissipation , and I'm using the 2.5K tap on the Hammond 125ESE. Dropping resistor values are the same as the stock 5F2-A. I WILL try the NFB switch to give him a bit more "perceived" volume. BTW , he tried my 5E3 for a while , but decided it had TOO much power , hence the parallel 5F2-A.
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I've built parallel 6L6 single ended amps and they have no trouble competing with a drummer.You do have to use multiple speakers or a very efficient 12".
I used three 10's in a Tweed Bandmaster cabinet.The output transformer size is pretty important.I used a Hammond 125FSE for a BIG tone and it still has nice breakup.Loud amp for what it was.GZ34 rectifier with big bottles and 5Y3 with 6V6's.
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I've always used beefier iron in my SE amps. It seems to me that tube recto's and modest iron belongs more to the PP family from my experiences so far. :dontknow: