Trinity TC-15 rookie build

[alathIN]

Excited about this build - I love Vox-ish tones and I've never had a hand-wired amp before. By no means an electronics expert but lots of experience taking on complex projects I'm not really qualified for 
Grew up in an engineering family and I'm an inveterate tinkerer.

I'm always telling my kids to set up their workspace before starting a job. For this project my gun bench, wood bench, and bike bench we're all wrong - so I set up in the grandiosely named Music Room - a former porch that's also kind of a home office. They keyboards are played by my 13 year old son.


Got started installing the hardware. It's good to have the computer right there so I can look up pictures of other people's builds, look at the schematic and layout and builder's guide.


Playing in this size space in an open floor plan home, volume control is a key goal for this build. Trinity sells a Voltage Regulation Module - a voltage based attenuator either as an option with their amps and kits, or as a standalone product. Instead of an power switch, you have a click-on voltage knob. I'd wodered whether to include this from the beginning or build it with the regular switch and then install the VRM later. I decided to go ahead and install it now, which is good, because it's a tight fit by the power transformer. If I'd built the amp with the regular switch, it would have required some awkward re-dos later. In addition to the pot/switch and the circuit board, there's also a mosfet that has to mount to the chassis nearby. At this point, my plan is to use spacers to raise the PT up about 3/8 inch to make room. From the perspective of this picture, it would move the PT down.


I've already gotten tons of good information, encouragment, and advice on this forum. If you see me about to blow myself up, don't be afraid to redirect me. I am in no way too proud to listen to advice.

[nandrewjackson]

Best of luck to ya'   


Looks like a nice project

[alathIN]

Not a lot to report today - did the usual two trips to the hardware store, once to buy the wrong size and then back to buy the right size, Eventually found the right spacers to raise the PT up a skosche and get some breathing room for the VRM circuit board. Also located where the VRM's mosfet will go, drilled the hole for its screw, and soldered on the leads to connect it to the circuit board.


Then I started working on the tone contour switch - which has to be seen to be believed - but came up short a cap I needed... which motivated something I should have already done - check the BOM.

Came up two caps short - both the same value. So the tone contour switch will have to wait. Just barely got started on the heater wiring, but should have more time for that tomorrow. 'Til then...

[alathIN]

Heater wiring.

[alerich]

I like the styrofoam component holder. Make sure you still check each component with a DVM before you install it just to be sure. The days I spent finding that 2K2 resistor where a 220K should have been in a Vibro Champ I rebuilt over fifteen years ago still haunt me.

[alathIN]

Got more done on the power side today.

Do you have any tips or a favorite website for how to place resistors/caps when the space between the lugs is shorter than the semiconductor? I can't get the leads to bend back in on themselves neatly.

[alathIN]

I like the styrofoam component holder. Make sure you still check each component with a DVM before you install it just to be sure. The days I spent finding that 2K2 resistor where a 220K should have been in a Vibro Champ I rebuilt over fifteen years ago still haunt me.

Rookie admission: it's easier for me to put a multimeter on it than memorize the codes.

If I have five from the same source with the same code, should I check all of them before I install? Because I didn't check the ones that were twins (or quads or quints).

[alerich]

If I have five from the same source with the same code, should I check all of them before I install? Because I didn't check the ones that were twins (or quads or quints).

I would. I check every component right before I install and solder. I have a Greenlee DVM that does resistance and capacitance. If I buy a bag of ten components I check each one before I install it. It only takes a few seconds and can save you untold hours of grief during debugging. I checked every component on my scratch JCM 800 50W build (no kit) as I went and it fired up first time.

[alathIN]

The power side is (I think) done - next step plug it in and test.

Wish me luck ;-)



Overall pretty happy with this build so far.
It gets a little crowded around the power switch and the standby switch due to the Voltage Regulation Module which takes up a lot more space and requires a lot more wiring than a standard on/off switch.

Only one thing nagging at me: look at the big can cap - black and round with three lugs, near the top middle of the picture.
It is supposed to ground from the center lug.
There's another ground wire coming in from the left. That's the ground for the VRM. I initially cut that lead longer, intending to run it straight to the grounding lug, but had a space cadet moment and thought "Why did I cut this so long?" cut it shorter and soldered it to the ground lug of the can cap. Is that OK or should I re-do it?

Let me know if there's anything else that ought to be nagging at me.

[PRR]

The green off the VRM is un-important. Land it anywhere.

Since you ask: _I_ would obsessively take the Red/Yellow HV CT directly TO the main filter cap leg, not round-about through a chassis lug. There are BIG current spikes in here. This makes voltage spikes in the jumper, appearing between cap and all your chassis. Stray buzz.

In THIS case I admit that your short jumper is NOT any real problem. I am not saying "change it".

Sometimes we find the HV CT (which is part of the rectifier, even if it looks like the other side) path runs hither and yon, inducing more spike-voltage and infesting much more of the chassis. I think it best, when planning, to assume the groundy side of the rectifier will land AT the first cap, *before* it goes anywhere else, so I don't have to nag myself later.

[alathIN]

Since you ask: _I_ would obsessively take the Red/Yellow HV CT directly TO the main filter cap leg, not round-about through a chassis lug. There are BIG current spikes in here. This makes voltage spikes in the jumper, appearing between cap and all your chassis. Stray buzz.

In THIS case I admit that your short jumper is NOT any real problem. I am not saying "change it".

Sometimes we find the HV CT (which is part of the rectifier, even if it looks like the other side) path runs hither and yon, inducing more spike-voltage and infesting much more of the chassis. I think it best, when planning, to assume the groundy side of the rectifier will land AT the first cap, *before* it goes anywhere else, so I don't have to nag myself later.

OK, that is a three-star reply.
1. good advice
2. well explained
3. easy to implement

 

[alathIN]

Speaking of the Voltage Regulation Module

I had convinced myself I'd messed it up somehow. Took it all apart trying to figure out what the problem was. Tried to do a confusing mosfet test.

Then called Trinity and spoke to Mr Cohrs. He suggested the following test procedure: hook up a 9 volt battery to the VRM's B+ in, and put the red multimeter probe on the VRM's B+out. Twist the dial up and down, see what happens.

Voila. I can dial up to about 5.9 volts and down to 0 volts.
If you try this at home, note, it doesn't work normally right at first. There must be something in the mosfet that has to charge up, because when you first hook this up, the voltmeter changes vveerrryyy sslloowwllyy when you twist the VRM dial. When whatever it is gets charged, you start getting an immediate change in volts when you change the VRM dial.

It turns out the problem I was experiencing was in my own head, not in the VRM 





I have nothing but good things to say about Trinity customer service.

PS - obviously that multimeter is not reflective of my skill as an electrical engineer. It was a hand-me-down from my genius little brother. I don't understand half the functions on that thing.

[alathIN]

The green off the VRM is un-important. Land it anywhere.

Since you ask: _I_ would obsessively take the Red/Yellow HV CT directly TO the main filter cap leg, not round-about through a chassis lug. There are BIG current spikes in here. This makes voltage spikes in the jumper, appearing between cap and all your chassis. Stray buzz.

In THIS case I admit that your short jumper is NOT any real problem. I am not saying "change it".

Sometimes we find the HV CT (which is part of the rectifier, even if it looks like the other side) path runs hither and yon, inducing more spike-voltage and infesting much more of the chassis. I think it best, when planning, to assume the groundy side of the rectifier will land AT the first cap, *before* it goes anywhere else, so I don't have to nag myself later.

OK, so here's my application to the no self-nagging club.


Given that the ability to get tone without too much loud is probably my #1 priority for this or any amp, I still think the VRM will probably turn out to be a good idea.
But it does crowd a bunch of stuff into a space that would ordinarily accommodate nothing larger or more complex than an on-off switch. To me, it's the least asthetically appealing corner of this build.

[alathIN]

Turret boarding.



If you look at the space between the .01uF mallory cap and the 220k carbon comp resistor, I added an extra turret. Somehow I ordered turrets that are shorter than the ones that came on the turret board from Trinity, so it looks a little odd. The reason I did that is between these two components is where the effects loop takes off and comes back. Without the extra turret, one of the components would have been "hanging in space." This will make it easy to come back and put in the effects loop.



Why not just put the effects loop in now? one would reasonably wonder.
I got one of these:

and installing it correctly requires a functioning amplifier. Or very nearly so. You have to take voltage readings with all of the tubes in place and working for this installation.

Sluckey and Tubenit here advised me NOT to try to cram a reverb circuit into this amp, which I believe was wise advice. Getting the VRM installed, versus every other component of this amp so far, was a telling comparison of how much nicer and more aesthetically pleasing it is to work when there's plenty of space around all your bits and pieces.
Since this head will have an active effects loop, I can basically make the same reverb circuit and use it as a stand-alone effect. Which will be a nice project to have on tap when the amp is done.

[alathIN]

PS - I know it's weird to have all the big caps pushed to one side like that.
One of them has to be like that, and my OCD couldn't let me put the others in a different alignment.

[PRR]

Your huge images are not showing for me.

Is it just me?? Or do you have Google User permissions set private (you only)?

[alathIN]

Your huge images are not showing for me.

Is it just me?? Or do you have Google User permissions set private (you only)?

It's possible I have them set wrong. I went to Google photos to find how to change the privacy settings and couldn't find it.
They do seem to be showing for other people (at least some?)

[VMS]

i see pictures, last picture that i see is on reply #8

[alathIN]

OK, I'll share them from a different site (not google). I think it makes them smaller too.

[sluckey]

I saw them earlier but they are gone now. Maybe google only lets you see them once?

[alathIN]

Is this better?

Shared from the meijer site rather than Google. It's what's been working up to now.

[VMS]

Is this better?

Yes, i see more pictures now.

[alathIN]

Had some busy work days and no time to work on my amp. Today got back to it, so it's a good day.
Tube circuitry is addictive. I'm already planning my next project. (Gear Building Syndrome?)

Spent the most time attaching leads to the turret board. I know there are different ways to do this. With the idea it would help me keep things neat, I decided to solder my connecting leads to the bottoms of the turrets. I'm not sure I'd do it again this way, but no major problems. It was an opportunity to double-check the turret board wiring (found two errors - misplaced jumpers). Then installed the turret board. With all those leads connected to the turret board, the satisfying neatness feeling is long gone. Should get better as I start connecting things.


Then had some time for a few odd tasks.

One of the oddest is the Tone Contour Switch. It's a six-position rotary switch for tone control on the EF-86 channel, which is supposedly modeled after an older era AC-15. I have never heard of an old Vox with this tone control, but I don't know much about old Voxes. I did see a YouTube demo of the tones from this channel when I was deciding what to build, and it sounded really good clean, crunchy, and in-between. That - plus the outright bizarreness of how this switch is wired - helped convince me to try building a TC-15. I've seen pictures of them that came out more neatly than this, but I think it will be functional (cross fingers)



Last was making the Hi - Lo input jacks - one set for each channel.
I imagine probably everyone knows about this already - I'm new, and happened to see it on a video from Boot Hills amplifiers - but I really like this idea of making a chassis face template for wiring things that would be a hassle to wire inside the chassis. My kids had left a piece of poster board on the laundry room floor, despite numerous requests to pick it up, so I decided it was fair game to borrow a chunk off the corner.

[sluckey]

That looks good! Won't be long now.

I decided to solder my connecting leads to the bottoms of the turrets. I'm not sure I'd do it again this way, but no major problems.

Are the wires secure such that they will not come loose or fall off if you need to solder on the turret later? I only use stranded wire for interconnects and always wrap the wire around the turret for a secure connection. I do use underboard jumpers using 22AWG solid wire. I push the wire all the way through the turret and bend it back down on the outside of the turret. No way to accidentally fall out of the turret.

     http://sluckeyamps.com/VAC15/underboard_jumper.jpg

One of the oddest is the Tone Contour Switch. It's a six-position rotary switch for tone control on the EF-86 channel, which is supposedly modeled after an older era AC-15. I have never heard of an old Vox with this tone control, but I don't know much about old Voxes.

None of the AC-15s ever had that rotary switch. Some AC-15s had a simple two position (ON-OFF) tone switch called Brilliance. The 6 position rotary came from the Matchless DC-30 amp. It's a good improvement to the AC-15. BTW, if you use a Make-Before-Break (MBB) switch you don't need the 5M resistors.

     http://sluckeyamps.com/VAC15/Vox_AC15_mods.pdf

I really like this idea of making a chassis face template for wiring things that would be a hassle to wire inside the chassis.

I sometimes temporarily mount the pots and jacks upside down on the outside of the chassis for easy wiring. When done simply flip the entire assembly over and permanently mount to the inside. The holes always line up perfectly.

     http://sluckeyamps.com/revibe/revibe_07.jpg

[tubenit]

That's looking mighty good!     

Sluckey always has good advice.

With respect, Tubenit

[alathIN]

That looks good! Won't be long now.

I decided to solder my connecting leads to the bottoms of the turrets. I'm not sure I'd do it again this way, but no major problems.

Are the wires secure such that they will not come loose or fall off if you need to solder on the turret later? I only use stranded wire for interconnects and always wrap the wire around the turret for a secure connection. I do use underboard jumpers using 22AWG solid wire. I push the wire all the way through the turret and bend it back down on the outside of the turret. No way to accidentally fall out of the turret.

     http://sluckeyamps.com/VAC15/underboard_jumper.jpg

One of the oddest is the Tone Contour Switch. It's a six-position rotary switch for tone control on the EF-86 channel, which is supposedly modeled after an older era AC-15. I have never heard of an old Vox with this tone control, but I don't know much about old Voxes.

None of the AC-15s ever had that rotary switch. Some AC-15s had a simple two position (ON-OFF) tone switch called Brilliance. The 6 position rotary came from the Matchless DC-30 amp. It's a good improvement to the AC-15. BTW, if you use a Make-Before-Break (MBB) switch you don't need the 5M resistors.

     http://sluckeyamps.com/VAC15/Vox_AC15_mods.pdf

I really like this idea of making a chassis face template for wiring things that would be a hassle to wire inside the chassis.

I sometimes temporarily mount the pots and jacks upside down on the outside of the chassis for easy wiring. When done simply flip the entire assembly over and permanently mount to the inside. The holes always line up perfectly.

     http://sluckeyamps.com/revibe/revibe_07.jpg

Man, you are making me want to build a more straight-up Vox amp next time around.
Although I'm intrigued by Trinity's versions of Hiwatt and Dumble, too.

Re Vox vs. Matchless (we had discussed previously) there's a switch on the T15 that is supposed to toggle between more Vox-ish vs Matchless-ish tones. What it does schematically is flip between 5k and 8k primary winding on the OT. But I have no idea how that would translate into what it sounds like. Do you know anything about this?

[sluckey]

That switch does about the same as running a mismatched speaker impedance. It will chane the tone. I don't know how that relates to Vox vs. Matchless

[alathIN]

UPDATE

I don't remember what site I saw this, but dude had a different way of doing his shielded jumpers. I thought I'd give it a try and I like how it turned out. Start out the usual way, then solder a short lead on to the shielding.

Bend the lead around and throw some heat shrink on it.

So I installed the jumpers and, in theory, the amp is done.

Face plate, channel 2, master, and power. Channel 2 is modeled after the classic Vox Top Boost.


Channel 1 - EF86 preamp and 6 position tone switch. Apparently this is typical of an earlier generation Vox AC15.



The whole shebang



Power section



Output section: phase inverter tube socket, power tube sockets, impedance selector, output jacks.



Preamp and phase inverter tube sockets. Installing the Voltage Regulation Module (attenuator) added some complexity to the tube sockets for V1 and V2 (bottom right).

There were a couple of areas that I felt got a little ragged on this build. Don't much care for the way the leads between the turret board and tube sockets turned out. Much neater on the volume and tone side.

[alathIN]

Channel 1 volume and tone



Channel 2 volume, bass, treble



So, I said it's done in theory.

Next time I get back to this, it will be time to double-check the circuit paths, power up, and test voltages.

[alathIN]

OK, going through the power up procedure as outlined in the Trinity documentation.

Mr Cohrs suggested wiring a light bulb in series on the power cord.

All the steps went fine until I installed all the tubes and started checking voltages.

The light bulb started to glow, which I'm not sure it is supposed to do. It never got bright - just a dim brownish-red.

All my voltages are low - in the correct order of magnitude, but low - V1p1 supposed to be 85, I get 57. V1P3 supposed to be 1.9, I get 1.4

I'm going to take a wild guess and hypothesize that I need to get the light bulb out of the power loop and just use a regular power cord... and my voltages will come up some...?

However I'm a bit afraid to power up again ever since the light bulb started to glow. It had that ominous foreboding Stephen King movie feel about it.
Should I go ahead and plug in with a regular power cord, or is something wrong?

[shooter]

It had that ominous foreboding

that's the good glow, If it resembled a landing light, that's the bad glow

[sluckey]

Plug directly into the wall, no light bulb. Turn the amp on and set the VRM control to max CW. Compare your measured voltages to the table on page 71 of the instructions.

[alathIN]

OK, so I trusted the Good Glow and the helpful advice on EL34world and here are my voltage numbers.
Once I replaced the light bulb thing with a normal power cord, they all fell pretty closely in line with what Trinity says is correct.

measured number (Trinity's spec)
V1
p1 72 (85)
p3 2.0 (1.9)
p6 109 (131)
p8 2.0 (1.9)

V2
p1 145 (137)
p3 1.36 (1.46)
p6 145 (137)
p8 1.36 (1.46)

V3
p1 174 (169)
p3 1.2 (1.3)
p6 275 (279)
p8 173 (160)

V4 (PI)
p1 260 (256)
p2 46 (47)
p3 69.6 (69)
p6 256 (254)
p7 47 (47)
p8 69 (69.7)

V5 EL 84 1
p3 8.4 (8.3)
p7 381 (384)
p9 219 (242)

V6 EL 84 2
p3 84 (8.2)
p7 381 (384)
p9 218 (242)

V7 5AR4
P8 391 (380)

Next step in the procedure was plug in and play.
First impressions:
the EF86 channel is LOUD and has a really nice crunch
the Top Boost channel isn't shrill at all - I actually had to turn up the treble to 6ish and the master cut to zero to get in the right range
Both channels: the low end is punchy as all get out. Reminiscent of a Fender Twin (one of the speakers in my 2x12 cabinet is a Weber reproduction of a vintage Fender speaker; that might be part of it).
I play fingerstyle and this amp is very touch sensitive. I felt like I could hear my fingerprints.

Too late to play much or really get into it, lest I wake all the kids instead of just one ;-)

More detailed report to come.
But initial impression is extremely pleased.

[alathIN]

Question about installing Metropolous Zero Loss Effects Loop:
The ZLFXL wants a B+ supply of 290-310 volts. The instructions say to pick up this supply at the phase inverter. Whatever power you measure at this node, you are supposed to put a decoupling resistor in front of the ZLFL to get the power down to the 290-310 range.

However, with the VRM installed on this amp, B+ at any of the tubes will vary, usually lower than the "normal" value.
So it looks like I need to pick up B+ for this "upstream" of the VRM.

It looks to me like the only place for me to pick up "unmodified B+" is at the standby switch.
I measured this at 390V. Metropolous says the ZLFXL draws .0017 amps.
So I want a 90V drop
V = IR
90 = .0017 * R
52.9 K ohms = desired resistor value
I have a 56K 1/2 watt metal film resistor on hand.
That would give me a voltage drop of
V = .0017 * 56K
V = 95.2
supplying 295 volts to the ZLFXL

I also calculate .5015 watts for this circuit, which makes me want to think twice about the 1/2 watt resistor. Is it OK to use resistors right at their nominal capacity? Or should I get a 1watt resistor for some "headroom?"

So, my plan is to solder an additional 600v wire on the supply side of the standby switch. Leave everything else alone - ie, I am not putting the ZLFXL in series with the rest of the amp.
Then put a 56K resistor in series between the 390 volt B+ and the ZLFXL.

In the metropolous instructions, they say you have to swap out the resistor at the node where you drew the power supply from, to restore that node to its previous voltage (accounting for the draw of the ZLFXL). I don't think this applies to me, correct?

One thing I am a little leery of; this puts the ZLFXL right off the first half of the 32/32 can cap, so it would only get one pass of filtering before going to the ZLFXL.
Which would obviously be a much noisier signal than at the phase inverter node, where it's been through all the filters.
But I don't see any way around that....?

Would appreciate if anyone cares to follow through my thought process here and see if I'm wrong about anything that's significant.

[sluckey]

 P = I²R, so .0017A flowing through a 56K resistor will produce .16W dissipation in the resistor. So a 1/2W resistor will be fine. However, Metro suggests 2 watt resistor. Looks like the kit comes with a 56K/2W. The instruction pdf has a table for correct resistor size based on B+. I would use a 1/2 watt resistor for testing but would plan to replace with a 2 watt.

Since power supply ripple will be very high at the STBY switch you need to put a 47µF filter cap between that 56K resistor and the ZLFXL board.
 

[alathIN]

P = I²R, so .0017A flowing through a 56K resistor will produce .16W dissipation in the resistor. So a 1/2W resistor will be fine. However, Metro suggests 2 watt resistor. Looks like the kit comes with a 56K/2W. The instruction pdf has a table for correct resistor size based on B+. I would use a 1/2 watt resistor for testing but would plan to replace with a 2 watt.

Since power supply ripple will be very high at the STBY switch you need to put a 47µF filter cap between that 56K resistor and the ZLFXL board.

Thanks, that's very helpful.

For whatever reason, my kit didn't come with any resistors.

[alathIN]

P = I²R, so .0017A flowing through a 56K resistor will produce .16W dissipation in the resistor. So a 1/2W resistor will be fine. However, Metro suggests 2 watt resistor. Looks like the kit comes with a 56K/2W. The instruction pdf has a table for correct resistor size based on B+. I would use a 1/2 watt resistor for testing but would plan to replace with a 2 watt.

Since power supply ripple will be very high at the STBY switch you need to put a 47µF filter cap between that 56K resistor and the ZLFXL board.

I followed your suggestion and the install went great. I'll post details and pictures elsewhere.

[alathIN]

Just wanted to finish this off - finally got around to building a cabinet for the TC 15.

I've been very pleased with this amp so far. It does a variety of clean tones and mild to moderate crunch very nicely - definitely has a few different flavors of Vox chime.
I did not anticipate using the cut control as much as I have. I like stuff pretty bright, so I figured why would I want a special brightness-destroying control?
But turns out the cut is brightness' best friend - setting the amp to where the treble is a bit ice-picky, then give it a touch of cut to round off the tip of the ice pick.
I never realized that cut was a post-phase inverter control until I built this. I'd be tempted to add one to any bright-toned amp I build in the future if it's not already in the plan.





Very grateful to the help I have gotten from online tube amp gurus including here.

This is really fun stuff to get in to, but the learning curve is steep for a rookie. Veteran advice is invaluable.

[Toxophilite]

Nicely done!

[sluckey]

Sharp looking amp! 

[mresistor]

Wow,  very nice work and a really nice looking amplifier.  :-)




I hope you don't mind me asking..  for the cabinet what is the radius of the edges?  Or what size router bit did you use ?