Tweed Tremolux in the making

[tubeswell]

Had a couple of days to catch up with some cab building.

This one's out made from 3/4" white pine again, but this time I've built the cab so I can use my new plunge router on all the edges. Then I'll give it a wee sanding and then me thinks I'll glue some more of that Gingham Tweed on it. I've got some metal corner brackets.

I've done a slightly oversized cab and I'm trying to decide whether to put a 12" or a 15" speaker in there. Dunno how a 5G9 goes pushing a 15" speaker tho' - might be a bit too much.

[tubeswell]

Tried out my new router today. Then since I was on a roll, I got the chassis mounted in the cab, and ploughed on with starting to wire up the PT, mains and stby switches, fuse, Heater circuit, Recto, mains grounding (see other post), and backside of the chassis wired up, (minus the filter caps). Too tired now. I'll think about the rest tomorrow.

[Paul P]

Originally Posted by tubeswell

Tried out my new router today.

Makes a mess, doesn't it . Do you have a model that you can hook up
a 'Shopvac' to ? I don't so the chips just fly everywhere.

Your amp is coming along nicely. How did you engrave your panel ? looks
really nice. Are you planning to fill the grooves with paint or something ?

Paul P

[tubeswell]

Originally Posted by Paul P

Makes a mess, doesn't it . Do you have a model that you can hook up
a 'Shopvac' to ? I don't so the chips just fly everywhere.

Your amp is coming along nicely. How did you engrave your panel ? looks
really nice. Are you planning to fill the grooves with paint or something ?

Paul P

Hi Paul P

yep my router came with a plastic gadget, but the vaccum adjustment that I prefer to use is a wooden pole about 1.5M long with a daft bit of brush on the end :-)

After pricing a proper laser engraver, (who hummed and hahhed and said it would take a couple of hours to draw up a computer file to accurately plot everything out etc for about $200, but that he couldn't do it today and I would need to bring it back in a week and leave it with him for a few days). So fortuitously, being the man I am who can't wait a couple of weeks for $200, I took the chassis to a Mr Minute down at the local Mall and said, "how good is your hand engraving?" and he said, "pretty good", so I said "can you do this, this and that?" and drew him a picture and asked "how much?" and he counted up all the letters and said "Yep that' be $42.50", then I said "fine, when will it be ready?" and he said "15 mins" and I said "can I watch?" and he said "Better not", so I left and came back in 15 mins and he only charged me $26! Well its not really top notch, but it'll do. Not sure about whether to paint it or not.

[Bruce / Mission Amps]

Originally Posted by tubeswell

Hi Paul P

yep my router came with a plastic gadget, but the vaccum adjustment that I prefer to use is a wooden pole about 1.5M long with a daft bit of brush on the end :-)

After pricing a proper laser engraver, (who hummed and hahhed and said it would take a couple of hours to draw up a computer file to accurately plot everything out etc for about $200, but that he couldn't do it today and I would need to bring it back in a week and leave it with him for a few days). So fortuitously, being the man I am who can't wait a couple of weeks for $200, I took the chassis to a Mr Minute down at the local Mall and said, "how good is your hand engraving?" and he said, "pretty good", so I said "can you do this, this and that?" and drew him a picture and asked "how much?" and he counted up all the letters and said "Yep that' be $42.50", then I said "fine, when will it be ready?" and he said "15 mins" and I said "can I watch?" and he said "Better not", so I left and came back in 15 mins and he only charged me $26! Well its not really top notch, but it'll do. Not sure about whether to paint it or not.

I think it is stellar and CLASSIC homebrew!!

[tubeswell]

Not making exactly the same cracking pace as my first build. Neverthless yesterday I did manage to get the main tag board and the bias board wired up and the control pot shafts cut to the right length.

Starting to ressemble what I thought it should look like.

Not sure about how these inputs should be wired. - I am currently thinking split ground, with all the pre-amp grounds and pre-filter cap ground going to an input ground lug, but which input ground lug should that be? In theory there are two input ground lugs, but I don't want a nasty ground loop if I can avoid it. Can I run all four input socket grounds to just one input ground lug?

[tubeswell]

Did the last of the wiring today and gave it a test run

Mostly okay except for a blown fuse incident after one-too-many switch on and offs (See debugging forum if you want to go there). I got an EH 5U4GB in there. Maybe I should swap the recto tube and see if that makes any diff? (I've got a Sovtek "5U4G"). When I have peace of mind about the blown fuse maybe I'll relax a little bit more.

Meanwhile it has a nice quiet hiss when dimed - no hums that I can detect (which I am quite pleased with touch wood). I haven't plugged my geetar into it yet, so I don't know how loud it is.

The screen and plate voltages are 370V and 371V respectively and the current measured from cathode to ground (with 1R resistors on each cathode) is about 31mA per tube (at least I reckon that's what it is - I used 2 x 1% 2R in parallel for each cathode to try and get as close to 1R as possible). It has a little choke for the screen supply and 470R 3W sreen grid resistors on each tube.

Going by the speaker hiss, the trem goes a little too fast overall - It seems to go a little faster than I would expect when cut, and wayyyy to fast (like a motorboat) when dimed - don't know how good that is for the 6V6s (as that is what the trem feeds directly into). There must surely be something I can tweek to change the trem speed. I have a 2m5 antilog pot (2 x 5M dual-gang pot wired in parallel) for the Speed control with a 100k wiper to ground (different wiper maybe?- bigger or smaller value?). The depth control works fine and totally cuts out the trem when cut.

Here are some chassis pics

[Paul P]

Good to hear about your build. I was going to ask since I've been needing
a shot of build news and it's been pretty quiet around here. I've been lost
in woodwork but I should finish that part later today.

Originally Posted by tubeswell

There must surely be something I can tweek to change the trem speed.
I have a 2m5 antilog pot (2 x 5M dual-gang pot wired in parallel) for the
Speed control with a 100k wiper to ground (different wiper maybe?-
bigger or smaller value?).

Have you measured the resistance range of your parallel pots ? I have some
10M pots that don't read much over 8M. If I understand your layout properly
you should have 100K to ground at maximum speed and 2M to ground at 0,
so if you're pots are accurate you should be even slower than the original
at 0 and the same at max.

What are your voltages around the tremolo triode ?

Paul P

[tubeswell]

Originally Posted by Paul P

Have you measured the resistance range of your parallel pots ? I have some
10M pots that don't read much over 8M. If I understand your layout properly
you should have 100K to ground at maximum speed and 2M to ground at 0,
so if you're pots are accurate you should be even slower than the original
at 0 and the same at max.

What are your voltages around the tremolo triode ?

Paul P

The paralleled pot measured upto about 2M when it was 2/3 of the way around. (My meter only goes up to 2M). The pot has 5M stamped on the back of it. The guy I brought it off (who I trust) assured me it was a 2 x 5M pot.

I think the whole trem speed range needs slowing down.

I'll check the trem voltages and get back.

[tubeswell]

Okay voltages are:

(Incidentally -72V bias supply, -28-29V going to the output tube grid load resistors. Grid load for each 6V6 is -23V BTW - Fender Schem suggests -27.5V, am I biased wrong? The phase splitter only measures 200V on the plate that the fender schem suggests should be 210V, and I get 189V on the plate that the schem suggests should be 200V - so maybe that's the reason? I dunno)

Anyhow the trem voltages.

364V at the first plate (260V at that tridoe's cathode)
All over the place on the second triode, but the highest voltage I saw on my meter was 250V on the plate and 2.2V on the cathode

[tubeswell]

Okay it sounds different when I plug my geetar in. Hmm maybe the genral trem range of the speed isn't so bad after all - quite hypnotic - I hope the guys in the band can keep better time than I did this first time trying to dub myself with it - it threw me out completely! (Please excuse the playing). I didn't take the trem right up on this sample, and I didn't record the overdriven sound (which I think is superb BTW). (you need iTunes to play this file). I did notice that I labelled the speed and depth contrls the wrong way round on ther dashboard. Oh well, I'll swap the pots another time - or maybe I won't (tee hee).

[tubeswell]

Okay - Did the baffle and grille cloth this afternoon - its starting to look a bit like my 5F2A. I'll take it to practice tomorrow night and test drive it with the band :-0

[Satamax]

Hi everybody!

Tubeswell, is that recording suposed to be MP3 4 or what? Doesn't work for me! But it's a way cool an amp!

[tubeswell]

Originally Posted by Satamax

Hi everybody!

Tubeswell, is that recording suposed to be MP3 4 or what? Doesn't work for me! But it's a way cool an amp!

Thanks Satamax - I think so too.

.m4a plays in iTunes (which is free from teh Apple website). Don't know what else it plays in

[Satamax]

Okay thanks, it reads now. Well, problem with me being kind of anti mac

[tubeswell]

Don't let that worry you. iTunes for pC is also downloadable from the Apple website. It works almost as well on a pC as it does on a mac ;-)

[Paul P]

To slow your trem down (should you still want to) I'd replace the 100K
resistor with something bigger, maybe 1M ? My speed pot is 4M (well
it's supposed to be).

Any chance of posting your clip in some form I can read, like mp3 ?

Paul P

[tubeswell]

.mp3? shouldn't be a problem. I'll get a man on it right away (might be tomorrow tho' - gotta go back to work today)

[tubeswell]

I shortened the clip to take out the bit which was a really embarrasing lack of co-ordination

[Paul P]

Hey, your tremolo sounds really nice.

(I guess it should coming from something called a Tremolux ).

Was that the slowest setting ? Certainly a useable speed.

Paul P

[tubeswell]

If I could get it slower still overall, so that it slowed down a bit more on the slowest setting and on the fastest setting, that would be good. At the moment it is wayyy to fast on the fastest setting

[tubeswell]

Originally Posted by Paul P

To slow your trem down (should you still want to) I'd replace the 100K
resistor with something bigger, maybe 1M ? My speed pot is 4M (well
it's supposed to be).

Any chance of posting your clip in some form I can read, like mp3 ?

Paul P

Thanks Paul P I've just clicked! Of course! Its so obvious to me now that the range of the trem speed is dependent on the range of the speed pot! :-0 Duh - Why didn't I think of that before? (Takes me a while but I get there). So I will fiddle around with the tapering resistor.

I think I'll start with a small change tho'. I'm thinking that whereas the circuit calls for a 2M pot with 100k taper resistor, since I have the pot wired as 2M5, then I should try maybe 120k-130k taper resistor to keep the change in proportion.

[Satamax]

Tubes, in an oscilator, you can change the speed with several parameters, the cap can be changed too.

[tubeswell]

Originally Posted by Satamax

Tubes, in an oscilator, you can change the speed with several parameters, the cap can be changed too.

Oh Okay - which cap would that be? There is a .03uF coupling cap from the plate of one of the triodes, and .01uF cap in series with this leading to a 1M to the cathode of that same triode, and then another .01uF cap after that leading into the grid of that same triode and a .1uF cap in series with a 1M resistor going to the depth pot. Oops, I think I've just spotted an error in something I did.

[Satamax]

The two .01/400 or .03/400 are both in the local negative feedback loop, and both can change your speed. Changing the 1meg should also change things.

[tubeswell]

Thanks again Satamax

I just realised before that I hadn't installed the 1M in series with the depth pot input (- dunno how I missed that? probably where its kind of hidden next to the 0.1uF in the layout digram - pays to double check the schematic aye?), so I fixed it and at the same time changed the taper resistor on the speed pot to 120k. Now the trem does not race away on me. I'll bear those other tweeks in mind.

On another note (s to speak) at the moment the output tubes are biased to deliver 22.5mA, which is probably about ballpark. I have a few unwanted vibrations to sort out in the chassis/cab, some of which should go when I cover the cab with tweedy fabric (wrap-around between the chassis and cab).

I did another .mp3 file to see how the trem sound had progressed. Excuse the lack of inspired playing - still suffering the after effects of last night's encounter with too many volts. I did the 'lead' with a 'shorting lead' across the inputs of the two input stages, which makes it slightly thicker sounding I think. I still don't quite know how to set up the output stage for better saturation without overbiasing it. Any ideas?

Cheers

[tubeswell]

Okay - was bored this afternoon and chucked in an Alnico Speaker out of one of my other amps and a 12AX7 in V1 just for the hell of it. This is the 'nother soundbyte attached.

I like the way the Alnico enriches the sound and gives a slightly better freq response than the (Greenback wannabe clone) thingy (that just doesn't make the grade) that I had in there before. I also like the slightly thicker timbre from the 12AX7 in V1, but I might hunt around for a better-yet NOS specimen. This offers the potential for increased voltage leading through to the output tube grids. I tried a NOS 5751 in V1 and that was also good - a bit creamier and more quack and nearly as much gain to the average non-discerning ear.

[richon]

sounds awesome...

wish i builded the REVIBE instead of the Reverb Unit to have this nice waving tremolo.

but, well, guess i'll have to build a tremolux now :mrgreen:

[Paul P]

Sounds great tubeswell.

You wrote :

Originally Posted by tubeswell

I did the 'lead' with a 'shorting lead' across the inputs of the two
input stages, which makes it slightly thicker sounding I think.

I could kiss you . I decided a while back, mostly for technical reasons,
to put my reverb on the 'normal' channel, leaving the tremolo on the
'vibrato' channel. Sort of a trade off, maybe not the greatest, but I was
pretty happy with the options. Then I read your bit about putting a lead
across the inputs and wondered, what if I jumpered my two channels
together, could I get reverb on channel two ?

Yes !!

With the guitar plugged into the 'high' jack of the vibrato channel I ran a
jumper from the 'low' jack of the vibrato channel into the 'high' jack of the
normal channel and I have both tremolo and reverb ! This is fantastic !

Thanks tubeswell !

Paul P