Trinity 18 Watt Kit Build

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mkel2010
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Trinity 18 Watt Kit Build

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I've been lurking here for a while but this is my first post.

I spent a few months researching 18 watt builds and decided the a kit was the best way to go for me. I chose the Trinity Amps 18 Watt siii kit, which I received a few weeks ago. I've built a few guitar pedals, but this will be a much bigger undertaking for me.

Once the amp is completed, I will be building the head cabinet and a 2x12 extension cabinet from Cherry. The speakers, from Warehouse Guitar Speakers - an ET-90 and a Retro 30 - arrive today.

So far, I've gotten to the point of wiring the power and output transformers, the heaters and completed the first power up. I got an indicator light and didn't have any sparks or smoke. All the voltages were correct, too. The photos below show my progress to this point. I built the amp cradle before the kit arrived. I will update the thread as I make progress in the build.
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Bieworm
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Re: Trinity 18 Watt Kit Build

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Exciting!!! I'm jealous... wish I was doing my first build. Now I'm just an addict πŸ˜ƒ
Going to confirm my shopping basket toninght for the next build.. and then tell my wife, when there's no way backπŸ˜„πŸ˜„πŸ˜„
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JMPGuitars
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Re: Trinity 18 Watt Kit Build

Post by JMPGuitars »

Welcome to the addiction! ;)

Do yourself a big favor, and read the ground and solder technique threads in my signature. They'll save you a lot of headaches.

Thanks,
Josh
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Re: Trinity 18 Watt Kit Build

Post by zaphod_phil »

mkel2010 wrote: ↑
Wed 03/17/21 11:25 am
I've been lurking here for a while but this is my first post.

I spent a few months researching 18 watt builds and decided the a kit was the best way to go for me. I chose the Trinity Amps 18 Watt siii kit, which I received a few weeks ago. I've built a few guitar pedals, but this will be a much bigger undertaking for me.

Once the amp is completed, I will be building the head cabinet and a 2x12 extension cabinet from Cherry. The speakers, from Warehouse Guitar Speakers - an ET-90 and a Retro 30 - arrive today.

So far, I've gotten to the point of wiring the power and output transformers, the heaters and completed the first power up. I got an indicator light and didn't have any sparks or smoke. All the voltages were correct, too. The photos below show my progress to this point. I built the amp cradle before the kit arrived. I will update the thread as I make progress in the build.
That looks like a really nice build coming along there! :)

Just one comment. As you may know, I was working in the Trinity Amps team up until they moved base out of Toronto to Eastern Ontario (although Stephen and I are still in touch). So I hope you'll allow me to share an opinion. IMHO the SIII lacks gain balls! I would recommend you build the same kit as a regular Trinity TMB or Trinity Plexi instead.Only some very small component changes required.Then you'll really be cooking with gas, as they say! :D
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mkel2010
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Re: Trinity 18 Watt Kit Build

Post by mkel2010 »

zaphod_phil wrote: ↑
Mon 03/22/21 12:17 pm

That looks like a really nice build coming along there! :)

Just one comment. As you may know, I was working in the Trinity Amps team up until they moved base out of Toronto to Eastern Ontario (although Stephen and I are still in touch). So I hope you'll allow me to share an opinion. IMHO the SIII lacks gain balls! I would recommend you build the same kit as a regular Trinity TMB or Trinity Plexi instead.Only some very small component changes required.Then you'll really be cooking with gas, as they say! :D
Thank you and thanks for the suggestion. This will be the first tube amp I've ever used so I'm not sure what I want at this point as far as gain goes. I did note that there are several options in the build docs for increasing gain on both of the channels and they do indeed look to be minor changes. I will take a look at it once again after I finish the build.
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Re: Trinity 18 Watt Kit Build

Post by mkel2010 »

I am slowly making progress on the build. I completed installing components on the turret board yesterday and today I installed it in the chassis and began the wiring.
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mkel2010
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Re: Trinity 18 Watt Kit Build

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I was finally able to finish the amp head a few days ago. Everything worked the first time I fired it up, but I did have some pretty significant hiss at higher gain and volume settings. I've been able to eliminate most of it by swapping pre-amp tubes to different positions. The issue seems to be in V1 and I may end up changing to some metal film resistors after I get the cabinet built and shielded to see if that has any effect on things.

The next step is building the head and speaker cabinets. That might take me a few weeks but I will post pictures in this thread when it's done.
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Re: Trinity 18 Watt Kit Build

Post by Bieworm »

It's hard to make a perfect first build. The hiss is possibly due to overheated components or dubious solder joints. You also have the board crowded with CC resistors.. so that might be a likely cause of extra noise.

Not the source of any problem, but you better put in a bigger cathode bypass cap. The 2200uf is recommended. It tightens up the low end, which is a nice side effect on a gainy amp.

And remember, higher gain and higher volume is always more noisy in simple designs with minimal filtering. The 3D harmonic sound of a hot 18W is achieved by the purity of the least possible component line up. Great amps with great overdrive are hissy more often than not. Imho...
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Re: Trinity 18 Watt Kit Build

Post by JMPGuitars »

To avoid hiss coming from the preamp, one of the most important resistors to use MF with is the 1M input resistor(s).

Thanks,
Josh
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mkel2010
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Re: Trinity 18 Watt Kit Build

Post by mkel2010 »

Bieworm wrote: ↑
Thu 04/08/21 4:33 pm

Not the source of any problem, but you better put in a bigger cathode bypass cap. The 2200uf is recommended. It tightens up the low end, which is a nice side effect on a gainy amp.
Bieworm,

After reading the part of your post above, I did some research trying to understand what you were talking about. I think I understand but I have a few questions to confirm:

1. In the attached schematic, I'm assuming you mean to replace C-10 (currently 50uf 50v) with the 2200uf capacitor. Would that also be a 50 volt capacitor? Would leaving R-20 (150 5W) be acceptable or would that need to change as well?

2. You mention "tighten up the low end." I think I know what that means, but could you be kind enough to explain it for me?

3. Does making this change have any negative effects on the amp?

Thanks,

Mark
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Re: Trinity 18 Watt Kit Build

Post by Bieworm »

Mark

The cathode bypass cap is indeed the 50uf 50V cap. When changing it to 2200uf it will still have to be 50V rated. Mine are 63V, but that don't matter. When you look at the cathode voltage it should be anywhere between 10.5 and 12V (aproximately).. so 50V rating is surely enough.
Tightening the low end means that there will be less tendency to get loose bass when playing louder. It's not a wonder cure but it seems to help with that phenomenon. Surely there are more pronounced changes for ghat in the preamp, but it helps anyway.

The 150R cathode resistor should not be changed.. IF the voltages are ok. The cap won't change them though.
Post your voltages .
Thx
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mkel2010
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Re: Trinity 18 Watt Kit Build

Post by mkel2010 »

Bieworm wrote: ↑
Fri 04/09/21 3:02 am
Mark

The cathode bypass cap is indeed the 50uf 50V cap. When changing it to 2200uf it will still have to be 50V rated. Mine are 63V, but that don't matter. When you look at the cathode voltage it should be anywhere between 10.5 and 12V (aproximately).. so 50V rating is surely enough.
Tightening the low end means that there will be less tendency to get loose bass when playing louder. It's not a wonder cure but it seems to help with that phenomenon. Surely there are more pronounced changes for ghat in the preamp, but it helps anyway.

The 150R cathode resistor should not be changed.. IF the voltages are ok. The cap won't change them though.
Post your voltages .
Thx
Thank you for the explanations. Here are the voltages taken when I completed the build:

AC Mains: 121 VAC
B+ - No Tubes: 419 VDC
B+ - With Tubes: 361 VDC

V1: Pin 1: 156
Pin 3: .934
Pin 6: 155
Pin 8: .917

V2: Pin 1: 161.6
Pin 3: 1.12
Pin 6: 262
Pin 8: 161.6

V3: Pin 1: 213
Pin 2: 50.9
Pin 3: 74.2
Pin 6: 212
Pin 7: 51.6
Pin 8: 74.3

V4: Pin 3: 11.3
Pin 7: 350
Pin 9: 337

V5: Pin 3: 11.3
Pin 7: 350
Pin 9: 337

V6: Pin 1: 301
Pin 3: 360
Pin 7: 301

Mark
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Re: Trinity 18 Watt Kit Build

Post by Bieworm »

You're a little over 100% tube dissipation. That's ok, but still high. You should aim for 85%. Better try 180R cathode resistor...
And maybe drop your B+ too first. It's 10 to 15V too high. Again, that's ok, but not recommended and deviates from the 18W vibe. This gives the amp a little higher headroom and thus later breakup. An 18W sounds better around 345V B+.
Last edited by Bieworm on Fri 04/09/21 10:04 am, edited 1 time in total.
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mkel2010
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Re: Trinity 18 Watt Kit Build

Post by mkel2010 »

Bieworm wrote: ↑
Fri 04/09/21 9:58 am
You're a little over 100% tube dissipation. That's ok, but still high. You should aim for 85%. Better try 180R cathode resistor...
Is that based on the V4 and V5 Pin 7 voltages?
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Re: Trinity 18 Watt Kit Build

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Yes
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Re: Trinity 18 Watt Kit Build

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You can calculate the bias at rob robinette tube bias calculator.
Select 6BQ5 tube
You have to extract the cathode voltage (11.3V) from the plate voltage (350V). This means 339.7V
Then all you need is the cathode resistor value and your cathode voltage and fill them in
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Re: Trinity 18 Watt Kit Build

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Wow.. the amp has a cathode follower.. how does it sound? This is probably a gainy little animal..Can you post a clip?
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Re: Trinity 18 Watt Kit Build

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Bieworm wrote: ↑
Fri 04/09/21 10:10 am
Wow.. the amp has a cathode follower.. how does it sound? This is probably a gainy little animal..Can you post a clip?
For my own edification, can you tell me what part(s) in the schematic that is?

As for your question, this is the first tube amp I've had so I don't have much for a frame of reference. It sounds fine to me, but again, little frame of reference. From what I understand, the Trinity siii version (this amp) is the least gainy of the 18 watt kits Trinity sells. I haven't gotten a lot of gain out of it at this point, but I also haven't cranked it up. Trinity has a voltage regulation module (VRM) which I have but haven't yet built or installed since the recommendation from Trinity is to build the amp stock first and make sure everything works. Since it does work, that's one of the things I will be doing next. At that point, I should be able to crank it up without complaints from the neighbors. :D

I will be glad to try and get a clip, but I'm not that great a player. It might take me a few weeks, so bear with me.

M.
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Re: Trinity 18 Watt Kit Build

Post by Bieworm »

The cathode follower is the 2nd half of V2. It drives the tone stack. A normal TMB tone stack will take a substantial part of the built up gain, but the cathode follower won't.
Usually the tone stack would come after the plate output of V2b ( pin 6).
But with a cathode follower the tone stack connects to the cathode side. This results in a higher gain preamp... to not get too technically...
But you can read about it here:
http://www.valvewizard.co.uk/accf.html
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Re: Trinity 18 Watt Kit Build

Post by zaphod_phil »

The DC-coupled cathode follower actually does two things:
1 - Yes, it acts as an impedance buffer, to match the high impedance of the output of the preceding preamp stage to the low impedance input of the TMB tone stack, thus reducing the insertion loss of the tone stack.
2- It asymmetrically "soft clips" the signal, for a warm, thick distortion. This is an important part of the "Marshall sound" of JTM45 and Plexi amps, carried over from the F*nder Tweed Bassman.
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