New Tremolux 5G9 build --> input welcome!

[klooon]

Hello, I am new on this forum. I saw some great 5G9 contributions here (e.g. Tubeswell) and got enthousiastic to build my own! Before, I have build 5E3 and 5F1 from kits, now I will try to do it on my own, but hopefully with a bit of help of you!

I will use a 5F4 Super chassis into a custom made 5G9 Tremolux 12" cabinet. I have Mercury Magnetics trannies on order to go into amp.

First I am working on the layout. I used the standard Fender version, because I couldn't find others on the net. I have rearrange the layout a bit, but I am not sure it is right now and some verification is needed! All comments are welcome! I added a standby switch because it can easily be added in the 5F4 chassis and I will try to put the 4x 20uF caps into the chassis as well, instead of a separate box...

[frus]

well the 5f4 chassis already has a standby switch hole
I have a Weber 5F4 chassis, and there is some space between the board and PT, those few extra components worth of board will probably fit

btw, you could put a single 40uF cap instead of two parallel (leftmost) caps on your layout, probably save some space

I just noticed, pins 3 and 8 on 12AY7 should be connected together

[klooon]

well the 5f4 chassis already has a standby switch hole
I have a Weber 5F4 chassis, and there is some space between the board and PT, those few extra components worth of board will probably fit

btw, you could put a single 40uF cap instead of two parallel (leftmost) caps on your layout, probably save some space

Thanks, I hope it will fit with the 4x20uF. After the layout verification, I will start on the dimensional layout of the eyelet board and see if it will fit, otherwise your option comes in handy!

btw, has anybody experience with eyelets on the (turret) board FR4 material? I heard that this material is a bit better (humidity, etc)...

I just noticed, pins 3 and 8 on 12AY7 should be connected together

Thanks, these are the comments I need!

New version (v2) of the layout:



Further, what about the pot layout: are they fine the way I plotted them? Also the values and log/audio? Does the 2M reverse log need a 100k resistor or only with the (possible original) 2M linear one? Further, a 2M reverse log pot is not available, can I just use a (CTS) 3M reverse log instead?

[tubeswell]

Hi klooon

Welcome to the forum and great choice of amp! FWIW Weber has recently bought out a limited edition 5G9 chassis with all the right screening. (Don't know if you have already got your chassis). See the checkbox for '5E7T' under 5E7M on this page Weber Chassis Products

My suggestion is build it stock first before you start tweaking. The stock circuit is fabulous.

Log taper pots are best for vol and tone controls. Use a linear taper for the depth control and RA taper for the speed control. 3MRA will work fine. When I did mine used a NOS 2M5RA and tweeked the tapering resistor to 120k. With 3MRA, you may want to try a 150k tapering resistor (instead of 100k) to get it working closer to the original. But when you get it working we can talk more about adjusting the trem if you want.

[klooon]

Hi klooon

Welcome to the forum and great choice of amp! FWIW Weber has recently bought out a limited edition 5G9 chassis with all the right screening. (Don't know if you have already got your chassis). See the checkbox for '5E7T' under 5E7M on this page Weber Chassis Products

Thanks for your reply! Unfortunately, I will receive soon my Tremolux cabinet with a 5F4 cut-out. The Weber option would have been perfect though!

My suggestion is build it stock first before you start tweaking. The stock circuit is fabulous.

Good suggestion. I will 'only' add a standby switch (because of the 5F4 chassis) and a bias pot for now. (Maybe later, I will add some sort of an attenuator - I am not sure what type is used in the new EC series Tweeds?? Pentode/Triode switch?? Any good??)

OK, but first the stock circuit. Do you think the layout (updated version v3 below) I produced is okay? Any comments/improvements/errors??

Log taper pots are best for vol and tone controls. Use a linear taper for the depth control and RA taper for the speed control. 3MRA will work fine. When I did mine used a NOS 2M5RA and tweeked the tapering resistor to 120k. With 3MRA, you may want to try a 150k tapering resistor (instead of 100k) to get it working closer to the original. But when you get it working we can talk more about adjusting the trem if you want.

Excellent info. Thus:
- Volume 1: 1M log (audio)
- Volume 2: 1M log (audio)
- Tone: 1M log (audio)
- Speed: 3M Reverse log (RA) w/ 150k resistor
- Depth: 250k linear

Below: version 3 of the layout...

[tubeswell]

Stick to the Fender layout and it will be fine.

[klooon]

I tried to ‘convert’ the stock Fender layout almost one-to-one to something that I can understand for wiring it up. The stock layout doesn’t deal with the additional ground wire from mains and the heater wiring from the 50s PT is 6.3V instead of the current PT’s 2 x 3.15V (and some other differences). For the rest the grounding on the original layout is still open for ‘interpretation’ (certainly for a newbie like me, who only built kits before in which the layout was in the form of e.g. Weber/Ceriatone). Also, how to wire the OT and choke is not displayed in too much detail. So for an experienced builder, this might be very trivial but for me, I am still not 100% convinced that it does not contain any errors anymore. I have been building pedals and no problem to fire them up, but with the high voltages and far more costly components I would like to be sure if I am doing it right. So, please let me know if this does or does not represent the stock version or somebody can maybe show how their ‘stock’ version looks like in more detail. ;-)

Thanks!

[loudthud]

Your layout seems to have 0.05uF 600V cap from the fuse holder to ground. This should be removed, it violates current safety standards.

Your grounding scheme will cause nothing but problems. It will have to be substantially changed to get the hum to acceptable levels. Easier to change it now rather than have to tear the amp apart later.

[klooon]

Your layout seems to have 0.05uF 600V cap from the fuse holder to ground. This should be removed, it violates current safety standards.

Thanks! I will remove it (this is the so-called death cap, I figured out...)

Your grounding scheme will cause nothing but problems. It will have to be substantially changed to get the hum to acceptable levels. Easier to change it now rather than have to tear the amp apart later.

Thanks! I did some further reading and saw and earlier post from Tubeswell:
Grounding Qn on 5G9

1) "In the end I have grounded the PI with the preamp and pre-amp filter ground, at one of the input sockets. All the input socket grounds are hooked up together."
---> On the eyelet board, where to locate the PI ground and preamp and preamp filter ground? (are these points 12 and 20 in my layout??)


2) "I grounded the trem cathode grounds and speed grounds at the trem footswitch socket ground"
---> Where to locate the trem cathode ground spot? And the trem footsw. socket ground, is this 'just' the socket ground lug??

3) "I grounded everything else, (Mains AC ground, heater CT, Output cathode ground, High Voltage winding CT, Bias ground) at one of the PT bolts)"
---> OK in my case?

Still have some questions regarding the power tube grounding --> how to do this?

Thanks!
Below, the updated version (v4) of the layout... I rearranged already quite a bit, hopefully for the better???

[loudthud]

Your ground is a little better.

There are a couple of mistakes that you need to fix. One is that the diode for the bias is connected backwards.

There is a wire missing from the Speed pot and an extra wire to the Tone pot.

Another safety issue, may not be a problem. The way the fuse holder is drawn could be a problem depending on exactly what type you use. Since one side is connected directly to one side of the line cord, you must make sure that it is impossible to contact that side when you are installing a fuse. On some holders that were available in the US, the side contact was possible to touch if you touched the end of the fuse as you installed it.

I have draw the ground the way I would do it. I moved one of the filter caps down near the preamp.

[klooon]

Thanks a lot for the updated layout!

There are a couple of mistakes that you need to fix. One is that the diode for the bias is connected backwards.

There is a wire missing from the Speed pot and an extra wire to the Tone pot.

Do you think all mistakes are out now?

Another safety issue, may not be a problem. The way the fuse holder is drawn could be a problem depending on exactly what type you use. Since one side is connected directly to one side of the line cord, you must make sure that it is impossible to contact that side when you are installing a fuse. On some holders that were available in the US, the side contact was possible to touch if you touched the end of the fuse as you installed it.

That makes sense! I will take care!

I have draw the ground the way I would do it. I moved one of the filter caps down near the preamp.

Make sense as well!

Just a few questions for me to understand better (I already learned quite a bit from this thread):
- It seems that there are two wires taking care of the 6V6 grounding (pin 8 at the left 6V6), is this okay?
- When reading the grounding topic that I was referring to above (Tubeswell), they were talking about the separation of the 'high' and 'low' current ground path:

I understand that keeping the 'low current' grounding points together and the 'high current' grounds together but keeping the low current ones away from the high current grounding points is an important ingredient.
Also, the voltage difference between grounding points has an impact on hum

Is this also done here, or maybe it doesn't matter in your opinion??

[tubeswell]

Hi kloon

The topic of grounding makes for interesting discussion. It is true that I built that 5G9 as I described in that thread and it was dead quiet. You might find that your build is different depending on the materials you use. The conductivity of the chassis, the resistance of the wires, the number of ground retrun points and where they are located all affect whether you get hum or not. loudthud is an expert at building amps and everything he has said is wise counsel. You are not going to know for sure how your amp will turn out until you finish building it. Then you may be likely have some questions or even some troubleshooting.

Therefore I suggest that you think about the design of your layout in such a way as to be able to make changes to grounding easily if you need to afterwards. This may mean being able to relocate a ground return wire (like the ground returns for the LFO, or the pre-amp filter stage etc for example) to a range of different points, just in case you need to experiment a bit.

Generally for tweed style amps, I ground all the pre-amp ground returns by their own separate wires to the same point as the pre-amp filter cap ground return and that goes to one of the input jack grounds. Then I do all the output stage ground returns and the reservoir cap ground return and screen node ground return (each by their own separate wires) to another point at the opposite end of the chassis. I could ground the LFO ground here too as it takes its supply from the screen node filter cap. (In the 5G9 I happened to choose to ground it at the footswitch ground and it worked perfectly well).

If you are careful with keeping the ground return points with the respective filter cap ground returns from which those parts of the circuit draw their power supply, then you will minimise the chances of hum from ground returns. Click here to view the article (360kb PDF) from Merlin Blencowe which is handy in this regard.

[loudthud]

The one error I found was a missing wire between 12AY7 pins 3 and 8. You might want to leave room on the eyelet board for a separate cathode resistor and cap for each side of the 12AY7. Plenty of discussion about the tone options this gives you on the 5E3.

One of the wires going to the 6V6 tubes pin 8 is the ground for the bias supply. It makes sense to ground it there because the 6V6 tubes are where it is used even if tremolo is applied.

An extension of the philosophy of separating high current and low current grounds is one where you try to keep currents in each block of circuitry within that block. When currents need to flow between blocks, (Signals and DC) then only those currents should flow between the blocks. This requires you to know where the current flows. The so called star ground supposes that since the grounds all come together at one point, only the ground currents for each circuit or block would flow to the correct circuit. The problem is that a stack of spade lugs on a transformer bolt makes far from a perfect star. It would be better to have a small eyelet board with one eyelet in the center and a circle of eyelets around it. A short wire from each eyelet in the circle would go to the central eyelet. Then a single wire from the central eyelet to the chassis.

One place where ground theory is a little fuzzy has to do with the grounding of the 6.3V center tap. My experience is that it doesn't make a huge difference, but it is probably measureable and opinions will vary on where the best place is. Other ways of reducing hum from the 6.3VAC are using a pot to balance the pickup from each side and applying a positive DC voltage to the center tap.

My profile has links to some threads with more reading on grounds. This thread may make the list.

[klooon]

Hi kloon

The topic of grounding makes for interesting discussion. .....

If you are careful with keeping the ground return points with the respective filter cap ground returns from which those parts of the circuit draw their power supply, then you will minimise the chances of hum from ground returns. Click here to view the article (360kb PDF) from Merlin Blencowe which is handy in this regard.

Thanks a lot for your reply! I think I need some time to digest the info and article now

[klooon]

Again thanks a lot! I have put your version into a my own template again, for future modifications and including Tubeswell's recommendations about the pots. See the layout below v5...

The one error I found was a missing wire between 12AY7 pins 3 and 8. You might want to leave room on the eyelet board for a separate cathode resistor and cap for each side of the 12AY7. Plenty of discussion about the tone options this gives you on the 5E3.

OK! What kind of tone difference is to be expected? 'like a 5E3'?? More raw/earlier break-up???? To be sure, if you put the extra resistor and cap I assume the connection between pin 3 and 8 should be removed again?

One of the wires going to the 6V6 tubes pin 8 is the ground for the bias supply. It makes sense to ground it there because the 6V6 tubes are where it is used even if tremolo is applied.

I am not sure if I understand... You mean that your 6V6 pin 8 is a grounding point now? And that it is used for the bias supply ground and tremolo ground... Maybe you can explain why a pin on a tube can be used as ground? Or should pin 8 be connected to ground?? I feel a bit ignorant.

Further FWIW I will connect all the jacks and pots to the chassis. (I see that some people are isolating them, but I am not intending to)

And I am not intending to isolate the trem jack as well. You indicated that then the extra grounding wire is not necessary, but does it hurt? Or similar to the input jacks: also extra wiring for safety (or noise in case of bad connection)?

An extension of the philosophy of separating high current and low current grounds is one where you try to keep currents in each block of circuitry within that block. When currents need to flow between blocks, (Signals and DC) then only those currents should flow between the blocks. This requires you to know where the current flows. The so called star ground supposes that since the grounds all come together at one point, only the ground currents for each circuit or block would flow to the correct circuit. The problem is that a stack of spade lugs on a transformer bolt makes far from a perfect star. It would be better to have a small eyelet board with one eyelet in the center and a circle of eyelets around it. A short wire from each eyelet in the circle would go to the central eyelet. Then a single wire from the central eyelet to the chassis.

One place where ground theory is a little fuzzy has to do with the grounding of the 6.3V center tap. My experience is that it doesn't make a huge difference, but it is probably measureable and opinions will vary on where the best place is. Other ways of reducing hum from the 6.3VAC are using a pot to balance the pickup from each side and applying a positive DC voltage to the center tap.

My profile has links to some threads with more reading on grounds. This thread may make the list.

I have to digest this a bit more... Sound like some solutions for final tweaking...


What about the diode. For the stock selenium rectifier it goes from + to - . But for the 1N4007 it is the other way around? pnp vs npn?


Updated 5G9 layout v5: