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Unfortunately, it's a lot harder to tell when an audio/log pot isn't working right than when a linear one is.


Yes, that's right. Do the wiper voltage and B+ stay fairly closely in sync.

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I should have added the word "control" - as in VRM control - just as Stephen did above.

I've put the leads back on to the VRM Control and measured the voltages, but I still have the 6L6 in there.
I'm going to swap back to the 6V6 just so my voltage measurements are consistent with what I've posted so far.

See attached for measured voltages.

I measured the voltages at B+, across pins 1 and 2 of the VRM Pot and put them in the graph.
I also measured across pins 2 and 3 while I was there - just because, but since it's pretty much the inverse of the voltages across pins 1 and 2, I didn't bother putting it on the graph.

I also pulled the pot and checked the part number - A1M

That looks correct

Most audio/logarithmic pots these days are just two linear pots spliced together.


Chris...

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It may be a wild@55 shot, but read this post & see if it makes a difference: http://www.trinityamps.com/phpbb/viewtopic.php?f=16&t=2713

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

My layout showed it going to the control side, so that's what I did.

I'll test things out and let you know.

*excited*

No change.

And I'm still getting the VRM control acting as more of a master control - turn it down to near 8 and the amp starts to break up. It sounds cool but I thought the VRM control was more of a presence control rather than what I'm hearing.

Where's the head-scratching smiley?

That's exactly what it's meant to do. It works as a Master, but one which also makes the amp get more "brown" as it's turned down. Just the breakup should be fairly smooth and not farty. If there's any sign of fartyness or intermittent breakup, then you probably need top do the fix that Stephen just posted the link for.


It's absolutely not meant to be anything related to a Presence control, in any shape or form. However, going onto 'Tude mode does open up the amp's presence.

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The top of page 8 in the builder's guide is what got me thinking what I was thinking.

I'm going to go listen to some sample clips - maybe I'm just expecting more out of it - but I think it's fair to expect to not have to crank the Power Level to get anything at all - and that's what's got me stumped. I'd love to hear a "This is what it sounds like with power at X, master at X, gain at X in tweed mode. Then X+1, X+2, etc..." set of samples. I'm thinking of doing that so you all can hear what I'm hearing. I just need to find a way to record. Worst case, I'll go with a computer mic. It won't be great, but it show the relative differences between the settings, I guess.

I did do the fix that Stephen mentioned above - no change.

Just to review where I'm at (to remind myself too)
tweed mode:
1. Power level really needs to be maxed. It breaks up at just below 8 to the point where a little bit less and sound cuts out completely.
2. Gain and master volume need to be above 6. Anything less and I get next to no sound at all and the guitar itself is louder than what's coming out of the speaker.

'tude mode:
1. Power level needs to be up there too, but seems to "hold-on" at the same point where tweed mode starts to cut out
2. There's more usability of the whole range of gain and master volume but only if one is maxed. With both down near 6, I get next to silence from the speaker.

I've tried two different speakers. One is known good and sits in my Jet City Amplification 2112RC where it works great. The other speaker is new to me, but it sounds great connected to the Tramp when things are cranked so I think it's fine.
I've tried two different speaker wires. The first one was a hacked instrument cable. It worked, but I was always looking at it sideways, wondering. The current cable is 14 AWG and is short.

I've tried different tubes in both sections of the amp.

My two cents: if you're expecting a smooth transition with the power level control then you need to swap the audio taper pot with a linear one. The nature of linear pots is that most of the resistance is in the upper half of the pot's travel. Either will work, yes - but personally, I wouldn't want an audio taper pot in that position because it would be harder to dial in an exact setting, IMHO.

I have one of the original Tramps. My normal settings are (6L6):

Tweed/'tude depends on guitar choice
Fat/Thin depends on guitar choice
Volume - Dimed (only use if I put really hot pickups to it, then I run in starved mod with the master dimed.
Bass - 6 and a bit
Treble - 7.5
Master Volume - Dimed

I have the original split shaft pot and I use it as a level control.
With my new toy (FretKing Supermatic auto tuner) my settings are Tweed Fat , sometimes in 'tude mostly tweed though.
Everything else as above.
Guitar controls:
Volume between 3 - 10
Tone dimed
Control pot for the coil tap at 7

The Tramp combo has a 10" alnico with a 15" ceramic in an ext cab.

My level control magic number is 5 and given 5 minutes of so its pretty solid for single notes and starts to break up on chords, very predictable and useable. As you pass 5 it starts to tighten up giving a cleaner tone.
When I get above 6 its starting to get loud and cleaning up on chords. And at these power levels the guitar volume pot becomes effective with out turning the sound flabby.
By 8 its clean and loud
At 9 and above its a maxed out 6L6 Tweed Tramp

I find the more time you leave your Level setting alone the less sag effect you get. My normal playing level is just a touch above 5 if not still touching.
Even when jamming I seldom get above 8 with my normal combo ext cab setup. Drummer can easily hear the guitar.
I like my Tramp so much that my Tweed is gathering dust, my Triwatt is my bass amp. The 18w gets its use and the Tramp head is just waiting for its new cab. Its set up to run EL34 and KT88. The Level/VRM works the same in it as it does in my combo.

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Tele's make the best noise

Have you changed the position of the input 1M resistor yet? Cutting out at reduced VRM settings is usually a symptom of the 1M resistor being in the wrong position.


The problem is that with a linear pot, the change in volume level will appear to be out of proportion to the position of the VRM control and you will find a lot of volume change appearing to be crowded in at one end of the dial. This is due to how we hear relative volume levels in a non-linear way.

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I got Chris from Amp Camp to fix mine up as I blew up a couple of things by accident. He replaced the blown parts and fixed some of my soldering and cleaned up my wiring and it works perfectly now. One of the things that was damaged was the zener diode. Also the big white resistor that we did the VRM bypass from was blown (that was my fault as I remember I wired it wrong at one point and blew the fuse). You might want to check your zener. Also some of my grounds were a bit loose. I have a feeling that perhaps one of my solder joints was the cause of the sputtering though (the signal not being able to travel properly through the solder joint). The VRM now has a smooth taper and no sputtering.

FWIW that's about the results I'm getting. I've fixed the 1M grid-stopper resistor - made no noticeable change.

Ignoring the limited usable range on the volume/VRM pots, the amp sounds good to me.

Do you remember what kind of control the VRM pot was. A knurled shaft or a solid one?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

It is solid shaft 1M audio pot.

The issues of taper and sputtering were because of other various problems.

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Yeah, I guess I don't have a problem with that because I'm thinking in terms of voltage variance more than volume. The level does drop off more significantly on the lower end of the range, but it works OK for me. YMMV.

Yep. I made the change. No difference..

I'm stumped...

Can someone else measure their B+ at the various positions please?

BTW. you can "raise" the lower end of the scale. Use a 200K resistor instead of the 100K to double it.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps