First sounds of the 18W TMB tremolo build

[Bieworm]

by the way.. in your revised layout I noticed you didn't add the 10k resistor fom V3 pin 2 to the board.
I don't know it was intentionally, but in case you forgot..

+ in my case I now have a 5.6k resistor from C to D

apart from all that..I really like your layouts Josh! They're clear to read and completed with the addition of measuring points A, B, C and D. That's very useful info

[JMPGuitars]

I left that out because I don't know if it's necessary. It doesn't hurt to have it though. (If you wanted to experiment with and without it, and see how it affects the noise, then we might be able to make that choice.)

Thanks, I'm glad you like them.

[Bieworm]

I left that out because I don't know if it's necessary. It doesn't hurt to have it though. (If you wanted to experiment with and without it, and see how it affects the noise, then we might be able to make that choice.)

Thanks, I'm glad you like them.

Now I'm only really anxious about that tremolo to operate...sigh
Need I worry about them cathode currents on V1?
Any suggestions on the high cathode voltages of the powertubes? Did the robrob bias calc.. tubes operate at 102.5% ...jikes!!!???
13.02V on the cathode of V4 and 5. With a 180R 5W resistor. According to Ohms law that means .0723 Amps. If there was a resistor of 170R in there I would have 12.29V.. is that correct? Ideally would be 165 Ohms...

Ofcourse I don't have that one here... But what if I connect a parallel resistor of 1k5 (5W) across the 180R ? Would make a total of approx. 161 Ohms...

[JMPGuitars]

Now I'm only really anxious about that tremolo to operate...sigh
Need I worry about them cathode currents on V1?
Any suggestions on the high cathode voltages of the powertubes? Did the robrob bias calc.. tubes operate at 102.5% ...jikes!!!???
13.02V on the cathode of V4 and 5. With a 180R 5W resistor. According to Ohms law that means .0723 Amps. If there was a resistor of 170R in there I would have 12.29V.. is that correct? Ideally would be 165 Ohms...

You're looking at the wrong calculation. https://robrobinette.com/Tube_Bias_Calculator.htm - select the EL84 and do the top calc before the cathode bias calc.

EL84s are pentodes, not triodes. If you enter it correctly, you're at 99% dissipation, and 11.9 watts. But as I said, ignore this until you drop your B+.

Your voltages look fine on V1, and I'm not sure why you're worried about the cathode current? I would triple verify the wiring of V1 regardless.

[Bieworm]

Now I'm only really anxious about that tremolo to operate...sigh
Need I worry about them cathode currents on V1?
Any suggestions on the high cathode voltages of the powertubes? Did the robrob bias calc.. tubes operate at 102.5% ...jikes!!!???
13.02V on the cathode of V4 and 5. With a 180R 5W resistor. According to Ohms law that means .0723 Amps. If there was a resistor of 170R in there I would have 12.29V.. is that correct? Ideally would be 165 Ohms...

You're looking at the wrong calculation. https://robrobinette.com/Tube_Bias_Calculator.htm - select the EL84 and do the top calc before the cathode bias calc.

EL84s are pentodes, not triodes. If you enter it correctly, you're at 99% dissipation, and 11.9 watts. But as I said, ignore this until you drop your B+.

Your voltages look fine on V1, and I'm not sure why you're worried about the cathode current? I would triple verify the wiring of V1 regardless.

I am going to try something..
Remove the shielded wires from V1 pin 1 and 7 and hook some regular wires on it. Then I can rule out of the shielding isn't touching anything it shouldn't. I don't think it does, but hey..
BTW I connected both shields to the ground at the tube area, not at the board area... is that ok?

[JMPGuitars]

I am going to the something..
Remove the shielded wires from V1 pin 1 and 7 and hook some regular wires on it. Then I can rule out of the shielding isn't touching anything it shouldn't. I don't think it does, but hey..
BTW I connected both shields to the ground at the tube area, not at the board area... is that ok?

That's fine. Shielded wire is always connected only on one end, and that's what's important. It also might not be completely necessary there, I copied the suggestion from a different layout. If it gets noisier without it, obviously it was helpful. But either way, you'll need to be careful of the positions of the wires, as they can cause squeal if in a bad position.

Verify the components and values and connections, and make sure nothing is connecting that shouldn't be.

You can also try different tubes there. In the past people have mentioned getting tremolo working specifically based on tube swapping.

[Bieworm]

I am going to the something..
Remove the shielded wires from V1 pin 1 and 7 and hook some regular wires on it. Then I can rule out of the shielding isn't touching anything it shouldn't. I don't think it does, but hey..
BTW I connected both shields to the ground at the tube area, not at the board area... is that ok?

That's fine. Shielded wire is always connected only on one end, and that's what's important. It also might not be completely necessary there, I copied the suggestion from a different layout. If it gets noisier without it, obviously it was helpful. But either way, you'll need to be careful of the positions of the wires, as they can cause squeal if in a bad position.

Verify the components and values and connections, and make sure nothing is connecting that shouldn't be.

You can also try different tubes there. In the past people have mentioned getting tremolo working specifically based on tube swapping.

Josh, the tremolo design was incorrect. I copied the design from the ceriatone classic 18 watt. I will draw it for you in a moment. It's a few tweaks and moving connections. I am gonna measure the voltages first. But I rewired it and BAM!!! Tremolo!!!

15857622781673709113844528969912.jpg

Look at that!!! Voltages are nice IMHO

Listen:
https://www.dropbox.com/s/yp2gp6khutfph ... g.m4a?dl=0

[JMPGuitars]

Voltages are MUCH better! Post another sample of the tremolo with the gain up (no pedals).

I'll review the changes.

Thanks,
Josh

[Bieworm]

Voltages are MUCH better! Post another sample of the tremolo with the gain up (no pedals).

I'll review the changes.

Thanks,
Josh

Voila!
https://www.dropbox.com/s/fp1oirkkkxaw0 ... e.m4a?dl=0

[Bieworm]

Oh damn... I was playing with the lightbulb limiter in the powerchain. Voltages are a little higher...

2nd readings:

1585767372463190337033392033956.jpg

[JMPGuitars]

Your voltages are definitely better than what they were. Though I'm not surprised that you should still drop your B+.

Thanks for finding those errors! I've updated the docs, and they should be all good now. Please verify.

It's funny, there was only 1 real error in the schematic, but it was an easy one to make (the missing jumper). That stupid backwards pot is because the schematic I referenced didn't label the pin numbers in their schematic. They're totally ambiguous otherwise.

Thanks,
Josh

PS. Post more demos! I want to hear the trem with different levels of gain.

[JMPGuitars]

Side note: you should always reference both the schematic and layout. If you highlighter tested against both, you would have found my mistakes faster.

[Bieworm]

Side note: you should always reference both the schematic and layout. If you highlighter tested against both, you would have found my mistakes faster.

I find schematics very confusing. Layouts are as-built plans. Much easier for a novice like me

Will make some more recordings tomorrow. It's late over here...

But I'm glad it's sorted out now with the trem. Stuff like that eats my nights rest...

The good part of these errors help me to understand that system. I previously did a trem conversion on my vibro king. From **** opto to bias vary...I learned a lot during that nightmare and got a little into amps that way

[JMPGuitars]

I find schematics very confusing. Layouts are as-built plans. Much easier for a novice like me

Will make some more recordings tomorrow. It's late over here...

The good part of these errors help me to understand that system.

Yeah, mistakes are usually the best teachers. Unfortunately...and I've learned a LOT.

Print both the schematic and layout. Highlight each part / connection as you match them up together. Start at the input and work from there. It will help you understand the docs and circuit better.

If you get comfortable reading the schematic, it's actually a lot easier to understand what you're looking at than the layouts. Layouts are just as you said, a guide for where to put stuff.

Thanks,
Josh

[crgfrench]

Sorry to jump in after the fact, I just wanted to say that tremolo sounds great!

[Bieworm]

Sorry to jump in after the fact, I just wanted to say that tremolo sounds great!

That is correct!!! There are only some little tweaks left to get this amp in pole position and you can start building your own clone

[Bieworm]

Your voltages are definitely better than what they were. Though I'm not surprised that you should still drop your B+.

--> you think it's necessary? I've read that these higher B+'es are no problem.. what is the downside of this? Why is it so important? I'm a novice

Thanks for finding those errors! I've updated the docs, and they should be all good now. Please verify.

--> Verified and qualified!!!

It's funny, there was only 1 real error in the schematic, but it was an easy one to make (the missing jumper). That stupid backwards pot is because the schematic I referenced didn't label the pin numbers in their schematic. They're totally ambiguous otherwise.

--> in f*nders they are often in the form of reversed audio pots (for the powertube bias vary that is...)

Thanks,
Josh

PS. Post more demos! I want to hear the trem with different levels of gain.

[JMPGuitars]

--> you think it's necessary? I've read that these higher B+'es are no problem.. what is the downside of this? Why is it so important? I'm a novice

They're not a problem in that range. Especially not if you're running a solid state rectifier. However, the ideal B+ of 345VDC (+/- 5V) is based on the characteristics of the 18 watt amp. Too high a B+ gives more headroom, and a less gain. Too low a B+ gives more gain (but likely muddy), and less headroom.

If 361VDC is your B+, it's really a question of whether or not you like the sound. It sounds great in your demo to me. If you want a hair more dirt, then drop it. If you like it, keep it as it is.

I have an amp I recently finished that has a switchable rectifier between solid state and tube. The Tube rec's B+ is 345. The SS rec B+ is 365. Both sound great, but there is a difference. I decided in that case not to match them, because the switch is useless if they both sound exactly the same. I'll probably post a demo comparing them at some point.

Thanks,
Josh

[Bieworm]

--> you think it's necessary? I've read that these higher B+'es are no problem.. what is the downside of this? Why is it so important? I'm a novice

They're not a problem in that range. Especially not if you're running a solid state rectifier. However, the ideal B+ of 345VDC (+/- 5V) is based on the characteristics of the 18 watt amp. Too high a B+ gives more headroom, and a less gain. Too low a B+ gives more gain (but likely muddy), and less headroom.

If 361VDC is your B+, it's really a question of whether or not you like the sound. It sounds great in your demo to me. If you want a hair more dirt, then drop it. If you like it, keep it as it is.

--) that's the "problem" ... Even though I have max headroom with that B+ value, I would like the grind to start a little later. Now the grind starts immediatly. Is there a way that I would be able to
- controll the amount of early preamp drive with a pot?
Or
- tweak the gain in an early stage on component value area.
I don't know if the grind is there before the PI.. otherwise MV post PI would be a solution. But that's adding various components with the risk of adding noisy stuff. A resistor or cap tweak would be less risky IMHO

Anyway, it's dat from doubt this amp has the potential to be a very versatile yet simple amp with all the necessaries such as TMB and Trem. A reverb is going to be the next journey. I have a sockethole spare since it's SS rectified + there are 3 unused inputs where there's the option to put controllpots . So a reverbtranny ,a pan and some wiring...

I have an amp I recently finished that has a switchable rectifier between solid state and tube. The Tube rec's B+ is 345. The SS rec B+ is 365. Both sound great, but there is a difference. I decided in that case not to match them, because the switch is useless if they both sound exactly the same. I'll probably post a demo comparing them at some point.

Thanks,
Josh

[JMPGuitars]

--) that's the "problem" ... Even though I have max headroom with that B+ value, I would like the grind to start a little later. Now the grind starts immediatly. Is there a way that I would be able to

You can try replacing the Volume pot with an A1M pot instead of the A500K. I dunno if that would make much difference, but it might give you some more play before all the dirt kicks in.

You can also reduce the preamp gain. You could try dropping the V2 plate resistor from 100K to 82K and see where that puts your voltage and sound.

Two things:
1. This is not a F*nder, and it's not supposed to be that clean. Your demos started off sounding very clean to me, with excellent tone. I wouldn't change it personally.
2. This is a touch-sensitive amp. You can play lighter, or roll off the guitar volume a little bit to clean up the amp. And you can turn up the guitar volume or play harder to get more dirt. I'd experiment with this before you do anything else. And post a demo of doing this. - no pedals, no touching the amp, just adjust the guitar volume knob and see what happens.

Thanks,
Josh