I just finished to build a Fender Tweed Deluxe Clone. Everything went ok, except for a strange noise. First I thought that could be the solid state rectifier, immediately I put snubbers in parallel. When I turn the volume up, that how it sounds like.
https://drive.google.com/file/d/0B9G9pBksxKNzdW83WlRkakZ5N1k/edit?usp=sharing
https://drive.google.com/file/d/0B9G9pBksxKNzdW83WlRkakZ5N1k/edit?usp=sharing
layout
do you have a schematic, and most important, a picture of your layout. It can help diag. Where the humming noise comes from.
do you have a schematic, and most important, a picture of your layout. It can help diag. Where the humming noise comes from.
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I had a similar problem and traced it to switching noise from the solid state rectifier coupling into the heater winding. The heater winding had spikes that were then coupling into the grids of the input tubes. I tried everything I (and folks here) could think of to make the rectifier quiet but nothing helped. In the end I went with a separate transformer (tiny one) for the heaters on the preamp tubes.
So take a look at your heater supply with an oscilloscope and see if it has noise spikes at the peaks of the sine wave.
So take a look at your heater supply with an oscilloscope and see if it has noise spikes at the peaks of the sine wave.
I built several guitar amps of my own design, and I always use solid state diodes for power supply rectification. I use DC for the filiments of the front end tubes, and elevate the filiment supply to about 90 volts (relative to circuit ground) so as to not exceed the heater to cathode max rating (especially an issue with cathode follower topologies). I also use only metal film resistors for minimal hiss noise (especially in the front end). And of coarse star grounding technique, with a separate ground wire for each section of circuitry. The star center makes the single circuit connection to the chassis. The ground wire of the AC line cord connects to the chassis in a separate location, right where it comes into the chassis. My amps are very quiet.
I'm done with this damn noise. My layout is kinda messy, I'm about to change some wires, I'll use shielded wires, and make a nice regulated DC source for the heaters. (After I fix my solder, that got burned.)
The most interesting fact is that the noise pratically go away, when I turn the tone pot all way down. There is no 60 Hz humm pratically, the noise seems to be more like 120 Hz, could be the filter caps? I heard someone say that with diodes you need to use larger capacitors, I don't know why, dosen't make much sense, but anyway..
The most interesting fact is that the noise pratically go away, when I turn the tone pot all way down. There is no 60 Hz humm pratically, the noise seems to be more like 120 Hz, could be the filter caps? I heard someone say that with diodes you need to use larger capacitors, I don't know why, dosen't make much sense, but anyway..
What I said about spikes at the peaks of the sine wave, I guess I should have been more specific, causes 120Hz noise since you get a spike at each peak, positive and negative. Bob's wiring techniques are also a good guide (my amps follow the same rules, except for the DC filaments).
I know it's really frustrating to have a noise problem after an exciting build, but try to stay calm. 🙂 If you have a spare transformer, just try isolating the filaments on the preamp tubes with a dedicated transformer. If the noise goes away, you've found the problem. Then you can fully assess the amp for other issues before embarking on a rewiring saga.
I know it's really frustrating to have a noise problem after an exciting build, but try to stay calm. 🙂 If you have a spare transformer, just try isolating the filaments on the preamp tubes with a dedicated transformer. If the noise goes away, you've found the problem. Then you can fully assess the amp for other issues before embarking on a rewiring saga.
That is how looks the output of the amplifier without load, the blue trace is the heater signal and the yellow one is the output. I built the amplifier in my university time ago, at home I don't have osciloscope to do tests, unfortunately.
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Heater supply looks clean, but that output is strange. What was the input signal, sine wave from a signal generator?
Maybe you do have a grounding problem (as Bob alluded to) and are picking up noise from the rectifier. Difficult to diagnose if you don't have access to an oscilloscope.
Maybe you do have a grounding problem (as Bob alluded to) and are picking up noise from the rectifier. Difficult to diagnose if you don't have access to an oscilloscope.
Valve amps are notorious for hum problems.
Heater layout and routing. Heater needs to be a t approx. 50 volts DC.
Layout, keep tracks/wires short and away from heater wires/transformers.
Star grounding is recommended. Especially those associated with charging pulses into smoothing capacitors.
Heater layout and routing. Heater needs to be a t approx. 50 volts DC.
Layout, keep tracks/wires short and away from heater wires/transformers.
Star grounding is recommended. Especially those associated with charging pulses into smoothing capacitors.
Any amp that has a transformer coupled output must never be run without a load, or the output transformer turns into a spark coil and can damage the transformer, the output tubes and even blow apart the output tube sockets.
I don't know where nigelwrite7557 got the idea that heaters (filiments) are supposed to run on 50 volts. If I remember correctly all heaters in that amp are 6.3V.
All wiring for the heaters must be twisted and solid core, and routed away from other wiring. Solid core (single strand) is best because it stays where you put it (18AWG is recommended - most hardware stores have it). The twisting is so the electromagnetic field that one wire emits will be largely cancelled by the opposite polarity field produced by the other wire. Any high impedance points in the circuit should have short connections and be physically away from any power supply or output wiring. All grid circuits are high impedance.
If you try to create a 6.3V DC supply for the front end (input) tube, the power transformer may not have a winding you can use for that. If you use the existing 6.3VAC winding, you may overload the transformer and burn it out. This is because after rectifying the 6.3VAC, you have to filter it with large capacitors (thousands of uF), which constitute a load by themselves. It's typical that the loading of the filter caps will be about the same as the filament load, which means the transformer sees a doubling of that load. In the amps I built, I ordered power transformers that had an additional 5VAC winding which could be used for the DC filament supply for the front end tube(s). Another problem with trying to use the 6.3VAC winding for a DC filament supply is that the rectifier diodes might put noise on the filaments of the middle stage tubes, which are very close to the grids of those tubes. There could be a noise problem from that. It might make better sense to add a separate power transformer just for the 6.3VDC for the front end tube, but keep that transformer far away from the input section, and ground one side of its heater connection. Tubes have specs on how far apart in voltage the various elements can be. You always want that to be defined and within the spec limits.
You might be able to learn something from my guitar amp projects on my website: Bob's Website
I don't know where nigelwrite7557 got the idea that heaters (filiments) are supposed to run on 50 volts. If I remember correctly all heaters in that amp are 6.3V.
All wiring for the heaters must be twisted and solid core, and routed away from other wiring. Solid core (single strand) is best because it stays where you put it (18AWG is recommended - most hardware stores have it). The twisting is so the electromagnetic field that one wire emits will be largely cancelled by the opposite polarity field produced by the other wire. Any high impedance points in the circuit should have short connections and be physically away from any power supply or output wiring. All grid circuits are high impedance.
If you try to create a 6.3V DC supply for the front end (input) tube, the power transformer may not have a winding you can use for that. If you use the existing 6.3VAC winding, you may overload the transformer and burn it out. This is because after rectifying the 6.3VAC, you have to filter it with large capacitors (thousands of uF), which constitute a load by themselves. It's typical that the loading of the filter caps will be about the same as the filament load, which means the transformer sees a doubling of that load. In the amps I built, I ordered power transformers that had an additional 5VAC winding which could be used for the DC filament supply for the front end tube(s). Another problem with trying to use the 6.3VAC winding for a DC filament supply is that the rectifier diodes might put noise on the filaments of the middle stage tubes, which are very close to the grids of those tubes. There could be a noise problem from that. It might make better sense to add a separate power transformer just for the 6.3VDC for the front end tube, but keep that transformer far away from the input section, and ground one side of its heater connection. Tubes have specs on how far apart in voltage the various elements can be. You always want that to be defined and within the spec limits.
You might be able to learn something from my guitar amp projects on my website: Bob's Website
I have built several Tweed Deluxe clones and not once had to resort to DC for the front end filaments, I don't even elevate them. I find that neat and tight twisting and proper routing is sufficient for guitar use. At full volume (how I play it) there is very minimal hum, pretty much have to stick your ear to the speaker to hear it. So I wouldn't go to crazy with changing the circuit just recheck everything you did and maybe just rewire the heater supply.
Make sure if your PT doesn't have a center tap then use two 100 ohm resistors to create an artificial one.
Make sure that all the heater wiring is twisted up tightly a neatly.
Make sure that you run your heater wiring to the larger currents (power tubes) first and then on to the preamp tubes.
Make sure that you don't switch phase of the heater wire connections to the sockets, by that I mean wire A goes to pins 2 on power tubes only and say pins 4 & 5 only of preamp tubes, and wire B goes to pins 7 on power tubes only and pins 9 only of preamp tubes only.
Try these steps first.
Also where are you grounding your input? With nothing plugged in the shorting jack should ground it anyway. But this could be the problem, maybe the shorting jack has a bad connection?
Make sure if your PT doesn't have a center tap then use two 100 ohm resistors to create an artificial one.
Make sure that all the heater wiring is twisted up tightly a neatly.
Make sure that you run your heater wiring to the larger currents (power tubes) first and then on to the preamp tubes.
Make sure that you don't switch phase of the heater wire connections to the sockets, by that I mean wire A goes to pins 2 on power tubes only and say pins 4 & 5 only of preamp tubes, and wire B goes to pins 7 on power tubes only and pins 9 only of preamp tubes only.
Try these steps first.
Also where are you grounding your input? With nothing plugged in the shorting jack should ground it anyway. But this could be the problem, maybe the shorting jack has a bad connection?
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The heaters run off 6VAC but the heater level is elevated to 50 VDC to help stop hum. Look it up if you don't believe me
I did it with my last design (100watt el34 based amplifier) and it worked a treat with very little hum.
Yes I'm aware of the concept of heater elevation. It works because it raises the ac heater above the cathode, making use of the fact the coupling path between heater-cathode is mono directional.
But Bob Richards was under the impression you ran you heaters at 50V instead of 6.3V.
But Bob Richards was under the impression you ran you heaters at 50V instead of 6.3V.
earth hum?
last deluxe clone i built, i got lazy and joined all the earths in a rail and had a bad earth hum, cut the earth wire between first and second filter caps and stared em (to the same place anyway) and hum is gone. I'm not sure how adding in an extra 2 inchs of wire prevents an earth loop but it did.
I've built 4 deluxe's now and that was my only noise fault they do hiss abit when turned all the way up but no hum, all standard fender power supply's no raised voltages or dc on heaters.
so I'd check your earths.
last deluxe clone i built, i got lazy and joined all the earths in a rail and had a bad earth hum, cut the earth wire between first and second filter caps and stared em (to the same place anyway) and hum is gone. I'm not sure how adding in an extra 2 inchs of wire prevents an earth loop but it did.
I've built 4 deluxe's now and that was my only noise fault they do hiss abit when turned all the way up but no hum, all standard fender power supply's no raised voltages or dc on heaters.
so I'd check your earths.
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