anyone have experience with the 5f1 circuit and noise/hum?

[M Fowler]

Well since your rebuilding it ceriatone's is the easiest to follow for layout but Fender's layout is good as well.

[rockstah]

Well since your rebuilding it ceriatone's is the easiest to follow for layout but Fender's layout is good as well.

yeah so maybe i will put some of the wires underneath the board like it shows to do as well.

[M Fowler]

And use different colors to keep track easier, repairs easier and looks nice too. Should be a fun project.

[rockstah]

And use different colors to keep track easier, repairs easier and looks nice too. Should be a fun project.

[rockstah]

interesting... after complete going through the amp and rewiring it, cleaning it up the wiring up it no longer goes into freak out mode but still noisy - not as noisy but still noisy...
[IMG:800:600]http://i24.photobucket.com/albums/c44/m ... C00559.gif[/img]
[IMG:800:600]http://i24.photobucket.com/albums/c44/m ... C00560.gif[/img]
[IMG:800:600]http://i24.photobucket.com/albums/c44/m ... C00561.gif[/img]

[tubeswell]

That kind of hum (that you get whether or not something is plugged into the amp) could be filtering, lead dress, tranny orientation (no pun intended) or shielding, but it could also be grounding.

Try the grounding first. What I would do is try a split ground system, where all the 'low current' pre-amp ground returns (including the pre-amp filter/decoupling cap ground, the vol pot ground, the pre amp tube cathode resistor grounds, and the grid leak resistor grounds) go each by their own separate wires to a common point on the chassis (at the input socket ground lug). Then have all the other grounds for the output stage (including both of the other filter cap grounds, the 6V6 cathode resistor ground, and the grid leak resistor ground, and the heater CT and the PT HT CT going each via their own separate wires to another common grounding point on one of the PT bolts (at the other end of the chassis). This should stop micro-rises in ground potential from the hi-current ground returns, getting into and interfering with the low-current ground returns. It only takes a few microvolts to upset the apple cart.

For lead dress, keep all AC pairs twisted together and keep them away from sensitive signal wires as much as possible to prevent unwanted EM coupling. Where it is necessary to have wires crossing, have them cross at right angles to each other. Keep signal wires and AC pairs close to the chassis. The chassis potential helps 'eat-up' stray EMR around the wires. And shield the sensitive signal wires from the input jacks to the grid pins of V1 (with the shields grounded at the input jack end only). Keep signal wires as short as possible.

For Transformer orientation, try rotating the OT through 90 degrees to the Pt and see it that helps. Do the transformers have steel end covers? These can help stop stray EMF coupling between the transformers.

For filtering, try increasing the size of the reservoir cap to 40uF (if it isn't there already). Also you could try a choke filter (with a 50mA 150R choke) in between the rectifier and the nominal '1st' filter cap. SE amps can generally noticeably benefit from choke filtering.

[labb]

A couple of suggestions from a rookie..First you are going to have to determine where the hum is coming from..Try this if you would...Disconnect the heater wiring from the transformer and instead power them with a large (lantern type) 6 VDC battery. If the hum goes away then it is in your heater wiring. If so try DC elevating the heaters.(connect the filament ground to the top of the 6V6 cathode resistor. Between the tube and the resistor). If this does not cure it then most probably you have a grounding issue. If it is grounding then try the split ground as the other poster recommended..Ground the 6V6, the HT ground, the speaker and the screen cap at the 1st filter cap ground. Then ground all of the pre amp and tone ground on a lug right at the input jack..I have a 5F2-A that has the DC elevation and a grounding scheme much like that that is described and it is very quiet.. Remember that some don't expect that amp to be perfectly quiet. They did hum straight from the factory and some expect that. Remember to do all of your checks for hum without any thing plugged into the amp. The input should be shorted. Good luck and don't give up. This is part of the fun in building your own amp. Also, make sure you are not picking up the noise from some external source ie: computer,lights etc.

[rockstah]

That kind of hum (that you get whether or not something is plugged into the amp) could be filtering, lead dress, tranny orientation (no pun intended) or shielding, but it could also be grounding.

Try the grounding first. What I would do is try a split ground system, where all the 'low current' pre-amp ground returns (including the pre-amp filter/decoupling cap ground, the vol pot ground, the pre amp tube cathode resistor grounds, and the grid leak resistor grounds) go each by their own separate wires to a common point on the chassis (at the input socket ground lug). Then have all the other grounds for the output stage (including both of the other filter cap grounds, the 6V6 cathode resistor ground, and the grid leak resistor ground, and the heater CT and the PT HT CT going each via their own separate wires to another common grounding point on one of the PT bolts (at the other end of the chassis). This should stop micro-rises in ground potential from the hi-current ground returns, getting into and interfering with the low-current ground returns. It only takes a few microvolts to upset the apple cart.

For lead dress, keep all AC pairs twisted together and keep them away from sensitive signal wires as much as possible to prevent unwanted EM coupling. Where it is necessary to have wires crossing, have them cross at right angles to each other. Keep signal wires and AC pairs close to the chassis. The chassis potential helps 'eat-up' stray EMR around the wires. And shield the sensitive signal wires from the input jacks to the grid pins of V1 (with the shields grounded at the input jack end only). Keep signal wires as short as possible.

For Transformer orientation, try rotating the OT through 90 degrees to the Pt and see it that helps. Do the transformers have steel end covers? These can help stop stray EMF coupling between the transformers.

For filtering, try increasing the size of the reservoir cap to 40uF (if it isn't there already). Also you could try a choke filter (with a 50mA 150R choke) in between the rectifier and the nominal '1st' filter cap. SE amps can generally noticeably benefit from choke filtering.

can u see the pics i posted?
ill check out the ground scheme but as i go through this amp it doesn't seem it would be making this much noise... seems like something more serious is wrong than grounding to me or caps i just keep going through it though.
i look at other 5f1 chassis shots with the lead dress not as good as mine is currently and wonder if they make as much noise as mine does.

[rockstah]

A couple of suggestions from a rookie..First you are going to have to determine where the hum is coming from..Try this if you would...Disconnect the heater wiring from the transformer and instead power them with a large (lantern type) 6 VDC battery. If the hum goes away then it is in your heater wiring. If so try DC elevating the heaters.(connect the filament ground to the top of the 6V6 cathode resistor. Between the tube and the resistor). If this does not cure it then most probably you have a grounding issue. If it is grounding then try the split ground as the other poster recommended..Ground the 6V6, the HT ground, the speaker and the screen cap at the 1st filter cap ground. Then ground all of the pre amp and tone ground on a lug right at the input jack..I have a 5F2-A that has the DC elevation and a grounding scheme much like that that is described and it is very quiet.. Remember that some don't expect that amp to be perfectly quiet. They did hum straight from the factory and some expect that. Remember to do all of your checks for hum without any thing plugged into the amp. The input should be shorted. Good luck and don't give up. This is part of the fun in building your own amp. Also, make sure you are not picking up the noise from some external source ie: computer,lights etc.

i have built many plexi style amps so this little simple circuit is kicking my ass... but i dont give up. thanks for the reply ill see what i can apply.
u heard the clip i posted? this is normal hum from the factory?

Code: Select all

ttp://www.soundclick.com/bands/page_songInfo.cfm?bandID=699407&songID=8269709

[Structo]

At the end of your sound clip is that nasty buzz from diming the volume?

At first I thought, it's not that bad especially if you are using single coils but then the BLAHZZZzzzz, at the end is really bad.

Try what was suggested, get a 6v battery to run the heaters and if that cures it, you know it is the heater wiring causing the buzz.

[rockstah]

At the end of your sound clip is that nasty buzz from diming the volume?

At first I thought, it's not that bad especially if you are using single coils but then the BLAHZZZzzzz, at the end is really bad.

Try what was suggested, get a 6v battery to run the heaters and if that cures it, you know it is the heater wiring causing the buzz.

plan on buying one of those batteries today and trying it.
humbucker pickup was used in the clip. the volume was at 9 o'clock, 12 and then 3 o'clock when u hear it freak out.

after redoing the whole amp it doesnt do that freak out anymore but still makes huge hummmm noise.

[labb]

Just listened to the sound track. At first it sounds like 60 cycle hum but not that buzz at the end. A couple of things to try: disconnect the NFB and see if anything changes. Also check and see if you have DC on the vol. pot. (possibly bad coupling cap). I would almost bet you that when you find it it will be something really simple..At least that is what always happens to me.

[rockstah]

Just listened to the sound track. At first it sounds like 60 cycle hum but not that buzz at the end. A couple of things to try: disconnect the NFB and see if anything changes. Also check and see if you have DC on the vol. pot. (possibly bad coupling cap). I would almost bet you that when you find it it will be something really simple..At least that is what always happens to me.

yes 60 cycle for sure - nothing happens when i remove the NFB wire - same noise.

no dc on the volume pot.

[tubeswell]

If its 60 cycle hum, then you probably need better filtering. Look at the 5e1 schematic for what I mean, and think about adding a small 50mA 150R HT choke between the rectifier and the OT primary filter cap. You will need 450V 10uF-20uF input cap in front of the choke (like what is in the 5e1). The rest of the circuit would be the same as the bog standard 5F1 (i.e. only you'd have 4 x filter caps).

[rockstah]

does it sound like 60 cycle hum?

Code: Select all

http://www.soundclick.com/bands/page_songInfo.cfm?bandID=699407&songID=8269709

i just cant get my head around that this is the way the amp is supposed to sound??... it seems it should be quieter than this stock...?