New Tremolux 5G9 build --> input welcome!

[loudthud]

The change I would make is this: Remove X to 4 and 3 to 4. Connect X to 3 and 4 to 2. It won't make a huge difference.

[klooon]

The change I would make is this: Remove X to 4 and 3 to 4. Connect X to 3 and 4 to 2. It won't make a huge difference.

Thanks. And the wire of pin 8 of the left 6V6 should go to (2) or is there a better point that could be used?

[loudthud]

Thanks. And the wire of pin 8 of the left 6V6 should go to (2) or is there a better point that could be used?

2 is the best place for the cathodes. Go all the parts yet? Time to get this thing built !!!

[klooon]

2 is the best place for the cathodes. Go all the parts yet? Time to get this thing built !!!

Only the chassis has to arrive. Hopefully this weekend or early next week. Can't wait!

In the meantime, maybe let me understand the grounding scheme a bit better.
- I removed the wire between pin 8 6V6 and point (4), is this still okay keeping the original grounding design in mind?
- The ground is 'floating' up to the point where jack ('B') is grounded to the chassis. Isn't this dangerous to be dependent on this single jack for the connection to the chassis ground? What happens if I would not use the wire between points (x) and (11)? Usually I don't mind and will try, but keeping safety in mind I rather check!

Here is the updated layout (version 13):

[loudthud]

In the meantime, maybe let me understand the grounding scheme a bit better.

- I removed the wire between pin 8 6V6 and point (4), is this still okay keeping the original grounding design in mind?

Yes. The idea is this: Currents flow in loops from the transformer to the filter caps and from the filter caps to the circuits that need DC to operate. The guitar signal is also an AC current when it flows through ground and back to the filter cap for that circuit. These currents in ground create small voltages because the wire has finite resistance (Ohm's law). When these small voltages get amplified, they contaminate (usually with hum or buzz) the signal we want to amplify.

The choke and the 10K 1W resistor isolate the currents flowing from the transformer so that only much smaller and quieter currents flow in the ground to the down stream circuits. There is a small current that flows through the bias supply back to the transformer CT. It's not as big of a current as what flows through the 5U4 and the parallel pair of 20uF caps, but it's better if it doesn't contaminate the ground of the 20uF cap (point 3) between the choke and the 10K 1W resistor. You can make the arguement that point 4 should actually go to point 1.

- The ground is 'floating' up to the point where jack ('B') is grounded to the chassis. Isn't this dangerous to be dependent on this single jack for the connection to the chassis ground? What happens if I would not use the wire between points (x) and (11)? Usually I don't mind and will try, but keeping safety in mind I rather check!

Leave that wire off and the amp won't work. Yes, the single point ground can be a problem. It won't hurt to connect the ground of the four jacks together with wires. Use star washers and make sure the nuts are well tightened. The biggest safety concern is that the daisy chain of ground wires must carry any fault currents in the amp. You should use a nice fat wire, #18 USWG or 1mm.

[klooon]

Yes. The idea is this: Currents flow in loops from the transformer to the filter caps and from the filter caps to the circuits that need DC to operate. The guitar signal is also an AC current when it flows through ground and back to the filter cap for that circuit. These currents in ground create small voltages because the wire has finite resistance (Ohm's law). When these small voltages get amplified, they contaminate (usually with hum or buzz) the signal we want to amplify.

The choke and the 10K 1W resistor isolate the currents flowing from the transformer so that only much smaller and quieter currents flow in the ground to the down stream circuits. There is a small current that flows through the bias supply back to the transformer CT. It's not as big of a current as what flows through the 5U4 and the parallel pair of 20uF caps, but it's better if it doesn't contaminate the ground of the 20uF cap (point 3) between the choke and the 10K 1W resistor. You can make the arguement that point 4 should actually go to point 1.


Leave that wire off and the amp won't work. Yes, the single point ground can be a problem. It won't hurt to connect the ground of the four jacks together with wires. Use star washers and make sure the nuts are well tightened. The biggest safety concern is that the daisy chain of ground wires must carry any fault currents in the amp. You should use a nice fat wire, #18 USWG or 1mm.

Thanks a lot for the excellent explanation!!

Below is the updated version of the layout (hopefully the final one)! I have put the extra ground wires for the four jacks and I will use the star washers.

[klooon]

Further, I have had quite some problems with vibrations in tweed combos, causing the tubes to rattle. Therefore, I will use grommets to attach the tube sockets as a sort of shock mount. Hopefully this works.

Also I have revised the layout when it comes to the orientation of the caps. I opened a K40y-9 PIO cap and looked for the outside foil (took some effort as they are built like a tank!). It appears that the 'arrow' inside the C-sign is pointing to the outside foil.


Comparing it to the original Fender 5G9, you can see that the outside foil side (marked by a band) is located towards the tubes. I have reoriented my caps according to this. More interesting info is given here:
Capacitor Be Quiet! | Sound Garage Tales
Where to connect outside foil on capacitors

[klooon]

5G9 Finished!!

Finally, all parts are in and I spent the last two weekends building the amp! Now it's finished. First some pics:

[klooon]

And how does it sound?

Hardly any hum and the sound is excellent. Very impressed and happy!! Lots of nice upper harmonics, very dynamic response to your attack and the guitar volume knob. Further, it distorts nicely and the tremolo is deep and lush!

The attenuator works great; it just knocks off a few decibels (half and quarter power) and the sound doesn't deteriorate at all.

Here is the final layout that I used, together with some voltage readings:



Many thanks to you all for your great contributions!!

[tubeswell]

Very tidy looking build there klooon! Soundbytes?

[klooon]

Very tidy looking build there klooon! Soundbytes?

Thanks! I will try to organise some soundbytes later.

I must say that the B+ and plates are running higher than I posted above. I saw that the 6V6 were initially running close to 100%. After checking the bias carefully, now at around 60-70%, the B+ is around 390VDC and plate voltage (pin 3 6V6) is around 376 VDC. (Remember my PT is 320-0-320). I think you got similar values???

Do you still have the TS 6v6s inside?

[tubeswell]

Yep very similar voltages. I went to JJ6V6S, they gave much better reliability than the New Sensor TungSols, (and methinks are sonically better as well)

[klooon]

Yep very similar voltages. I went to JJ6V6S, they gave much better reliability than the New Sensor TungSols, (and methinks are sonically better as well)

Thanks. What happened to the TungSols? Rattle, microphonic or maybe even blown? The TS 5881 in my 5F4 are rattling like hell by the way...

Related to this? tung sol 6V6 reissue reliability - The Gear Page (although we are not at 400+VDC...)

[tubeswell]

Thanks. What happened to the TungSols? Rattle, microphonic or maybe even blown?

IIRC they started making funny low freq intermittent 'background' buzzing noises within a few weeks use.

The TS 5881 in my 5F4 are rattling like hell by the way...

I use Russian 6P3Se (with the wafer-think black base) instead nowadays and have found them pretty reliable as a '5881' substitute. They're a military grade 20W tube (but reportedly take up to 30W) and can easily handle 460V. Designed for use with Soviet-era ICBMs I believe.

[klooon]

I use Russian 6P3Se (with the wafer-think black base) instead nowadays and have found them pretty reliable as a '5881' substitute. They're a military grade 20W tube (but reportedly take up to 30W) and can easily handle 460V. Designed for use with Soviet-era ICBMs I believe.

That's a good suggestion! I've just seen more good reviews, though will be hard to find them here in the Netherlands (maybe somewhere else in Europe??). First I will try a pair of TAD 6L6WGC STR that I ordered a while ago, but I had problem with biasing as they were way out of the biasing range of my 5F4 (too cold: 35%), need to fix that first with another pot and series resistor.

IIRC they started making funny low freq intermittent 'background' buzzing noises within a few weeks use.

OK, I will stay away from TS. Next to the JJ's, maybe I will give the TAD6V6GT a try. I see some good reports on them as well now.

BTW Did the JJ 6V6S give you some increased headroom over the TS?