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How can I lower the output of channel one significantly it has much more gain than channel 2 witch is because of the tone stack on channel 2 , I've tried a bigger resistor on the input to the plate but its still not enough I've even gone 4 times bigger with the resistor what can I do please help ?
Follow Ups:
Channel 1 will have inverted phase
compared with the other channels.The only option is the common cathode.
Drawing is the closest I could find.
Basically a cathode follower
driving a grounded grid.
Volume pot from input to Pin 7
Short cathodes (No Bypass Caps !!!)
(Need AC signal there to drive 2nd stage)
1uFd cap from Pin 6 to ground
(Provides DC voltage for CF and
keeps the same operating point)
Ground Pin 3DanL
Edits: 07/22/15 07/22/15
I'm not running the two halves in parallel any more I have one stage of channel one going into channel 2 the other stage of channel one is completely disconnected. Is this still needed then?
No worries with bass guitar amp. You can put a phase invert switch into the unit, but my bet you won't hear too much difference. Esp when mixed with other instruments.
It is sounding amazing now the overdrive is nice warm and crisp no distortion, I almost don't want to change anything now its sounding so good where should I put this phase invert switch because it needs to work in studio as well and there that is going to make a difference
Most instruments amps/guitars/bass/etc are out-of-phase with each other, anyway. The most I'd do is maybe reverse the speaker(s) phase, once you are playing in a group. See if that makes a difference.
If not... let sleeping dogs lie.
8^)
Just had band practice and I'm definitely gona leave this dog sleeping its sounding amazing nothing like real tube tone. It doesn't seem to be out of phase with anything its sounds almost exactly like a bass mann but just with the nice over drive the tubes just just breaking up perfect bass tone
First try removing the 16uFd bypass caps.
If that is not enough reduction -
Connect the input to the volume pot
(Bypassing the 1st tube stage -
FenderLover's suggestion)
DanL
If I remove the bypass caps should I leave the 2.2k resistor still connected?
This completes the circuit, through the tube.
FWIW... you can bypass either half of that input tube.
Can I maybe run the 2 halves in parallel? And what should I do with the 0.1uF cap if I bypass one of the gain stages. Thank you so much for the help
Simple ...
Remove 68K and .1uFd cap on first tube
Remove both 16uFd bypass caps
Short pins 2&8, 3&7 and 4&6
Connect input to 100K Volume Pot
DanL
Thanx so much for the advice should I swap out the 50k volume pot for a 100k then as well? I'm first going to try lowering the size of those caps because they are at 32uF at the moment, if not enough bypass them and then bypass one of the gain stages or run them in parallel. If its still not enough
Correction -
Connect input to 50K Pot
Changing the 50K pot does NOTHING.
Don't bother.
What caps are 32uFd?
The cap only determines F3 not gain.
(F3 is the low frequency roll-off)
DanL
The 16uf 25v caps on the cathode's, they are 32uf so I'm going to lower them to 16uf 25v and lower,to see if that helps, else I'm going to run the 2 gain stages in parallel
I don't think changing the bypass caps from 32 to 16mfd will do too much to the overall gain of that stage. This bypass mostly effect bass quality --- not gain.Why are you thinking about strapping the two triode halves together? This only increases the current gain. Something, I think you do not need. Just bypass one or the other triode and see if that solves the original problem.
If it does, then think about how to utilize that unused half. Or just cut the power to that half's anode plate. IOW, electrically remove it from the stage.
Or you can use it for a reverb or vibrato/tremolo stage... if you are talking DIY bass guitar amp.
Edits: 07/21/15
Thank you so much for explaining it to me in "noob" terms I understand completely now so I can just cut the power to one of the anode plates the sound will still go trough it even tho it has no power? Maybe then just put a little toggle switch on its power input so I can still have that insane distortion if a want to or just flick it off if I don't? Will that work?
No, you need to jumper between pin 3 and pin 4 connections. Disconnect the lead from B+ and pin 4. This bypasses the second half of that 5670.
Awesome thanx so much for the help this is basically a fender or alembic F-2B that uses 5670 tubes without a tone stack on channel one
I know of no 5670 compatible substitute, which has lower mu. Prolly wouldn't work anyway --- to compensate for lack of stack in one channel. Think bypassing one half of the 5670, in that stage, is the best option to try.
Changing or removing the cathode bypass cap will definitely change the tone of that channel. Can't you just set the volume control in the stack-less channel, to lower setting to compensate?
Yes it is I built it myself from a schematic I got from the net. I have bypassed the one half of the channel one gain stage. it is sounding pretty good especially with the 2 channels in series, I have perfect overdrive for bass. I'm not running them in parallel any more only clean channel with tone stack and then channel 2 over drive with one of the channel one gain stages in series in front of channel 2 with the 50k volume pot in between them. So the bypass caps does affect the tone a lot what will be best then for bass?
You'll need to experiment with the value. This depends a lot on how each stage is setup. Don't go crazy (like 250mfd) --- or you might get "farting" bad blocking distortion. That's a sign the bypass mfd value is too high.
I'd limit it to 100mfd/50VDC tops. See how the tone is like. 25mfd/50VDC maybe good, if you feel the very low notes are a bit muddy. IOW, you wish to get a cleaner bottom end.
Try to stay with 50VDC or higher voltage rated electrolytic caps.
Good luck! Tells us what bypass works the best.
I think I'm going to stay with 25v on the caps because all the original schematics on the web for a alembic F-2B is running 50uF 25v on the bypass caps I could only find 47uF 25v at our local electronics store I'll keep you guys posted on how its sounding
Most older amps and DIY kits were based on 112-118VAC outlet voltages. Today's outlet being ~125VAC can increase B+ significantly more (like 25-50VDC on the plates).
This leads to much greater voltage drawn across the cathode. Pushing the voltage near 25VDC, in some cases. 50VDC rated caps gives you a better range of safety.
I am from south africa our AC outlets are 250-260V some times at night it even goes as high as 280V I've even seen it go as high as 300V tested with my multi meter so I must try 25uF 50v for the bypass caps I have a few 100uF 50v caps will it be safe to try them?
If you tied two 100mfd/50VDC cap in SERIES --- (+) end of one to (-) of other --- you'll get resultant capacitance = 50mfd rated at 100VDC. This might be better for your application.
Like C1 and C2 in diagram.
I went and I got some 47uf 50v caps from the store it definitely improved on the low end a lot its sounding even better think I'm gona keep it just like this we tune down to drop A in my band so my bass has a lot of low end and this made a big difference thanks so much
Sounds good. You can try 100mfd/50VDC or 100/100 caps, but you may get blocking distortion.
Just use the 47mfd/50VDC for now.
BTW... what 5670 tubes are you using? GE black plate JAN-5670W or JG-5670 are nice and available.
I'm using the black plate GE JAN-5670W I'm thinking of experimenting and getting a pair of russian 6N3P's and maybe a pair of 2C51's and experimenting with different combinations of them. I was wondering If it might be possible using that other gain stage in channel the one that is un used to make an effects loop circuit with that has an effects blend as well?
if you might have a schematic of something like that?
You'd need a reverb driver tube. Fender amps usually use a 12AT7, both sections strapped together.-----
Not sure if the second half of that 5670 will have enough gain for the reverb unit.
Edits: 07/24/15
I don't really have any use for reverb I play bass I think I might build myself a effects loop pedal with a effects blend so I can use my tube screamer as well because I need it in a effects loop with a blend pot
But, this and other EFX can be emulated just fine with pedals.
Just disconnect the anode to the unused half.
is it a must to disconnect the anode to the unused halve? Because everything is put back together now
Disconnection just saves that one-half of the duo-triode. Don't worry about it. I'd get a few of those mil-spec GE 5670W tubes, for backup.Then, play the heck out of the amp. Enjoy!
Edit: meant "slap-back." But, you knew that.
8^)
Edits: 07/25/15
I wish I could get a couple of them for backup but its basically impossible finding them locally in south africa I have to get them shipped from the U.S and u.p.s shipping is about $150-$200 and using our local post service is useless it can take up to 6 months IF they arrive its a 50/50% chance the will arive or not.
Those bypass caps how exactly does it work? higer uF means more lows and lower uF means more highs? because those 47uf 50v caps I have in now has perfect low end but the high mids and high's are muddy now and I need them to be clear can I have different uF caps at different gain stages as long as the voltage stay the same?
Lower the 220k plate resistors to 150k. Just check that you don't exceed the tube's plate voltage. Remove the 16ufd cathode bypass caps.
Dan Santoni
How do I check that I don't exceed the plate voltage I only have a multi meter? And wouldn't it damage the tubes if I remove the cathode bypass caps wil that lower the biasing? Sorry but my knowledge with electronics are very little I'm only starting out
Tried bypassing the second half of the 5670 gain stage, in channel one?
How do I bypass the second gain stage on channel one sorry for the stupid question my knowledge is very limited
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