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PostPosted: Fri May 25, 2007 7:31 pm 
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Here we go. I finally got my arse in gear and did it. The version posted may not be too easy to read so i have a BMP file saved on my PC but it runs at 6.5Mb. I need some where to host it or i can e-mail it to interested parties...

Image

If theres any error, please let me know and i'll update the layout.




Hosted Layut:

Tiny_Terror_Layout_v.1.11.jpg

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PostPosted: Sat May 26, 2007 6:46 am 
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I'll host it if you send it. Also, do you have a schematic?

For those who want to know, the Tiny Terror is a Class A tube head amp useing EL84 valves, switchable power output of 15 or 7-watts mean full crunched tube tone is available regardless of the output volume.

Class A circuitry means the Tiny Terror output tubes are producing both positive and negative halfs of the output signal. Class A creates an output signal rich in even order harmonics for a full and complex tones.

(2) EL84 Power Tubes
(2) 12AX7 Preamp Tubes
Switchable output 15 or 7-watts.
1-Channel with Gain, Tone, and Volume controls.

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PostPosted: Sat May 26, 2007 7:03 am 
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Cheers! The bitmap file is rathe rlarge but it retains its detail and colours better than JPGs. Its 6.5 Mb so if your e-mail account doesnt mind :wink:

PM me your address and i'll e-mail it to you.

Cheers!

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PostPosted: Sat May 26, 2007 12:01 pm 
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Wow,
Heres my email:
jerryrigstudio@gmail.com.
My computer can handle well... no problem :D
Thank you Wicksy.
And thank you Coco for the explanation. That's great. Wonderful.
Later
(edit)
Thanks coco for hosting, very interesting design, eh :D


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PostPosted: Sat May 26, 2007 12:52 pm 
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Hey Wicksy!
Great Job! Thanks man! Do you know a link to any sound clips for that little devil?
Stew


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PostPosted: Sat May 26, 2007 12:59 pm 
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I reckon theres a good few on the Orange Amp forum. Everyone over there got obsessed with the thing a while back. Basically half a tone of newbies turn up posting their love for the TT. It pissed off a few of the old crowd.

I'm in the process of building a chassis for this. Its going to be made from the remains of an old PC case (to keep things cheap). I have the turret boards (robbed from a SC PA chassis) and the iron i'll temporarily pilfer from my Ampmaker 18watter until Barry gets better and i can get some more. I have most of the other stuff so i can get it put together soon. I'm just loathe to take the trannies off my 18watter! I love it too much.

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PostPosted: Sat May 26, 2007 3:57 pm 
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Wicksy,

Thank you so much.I have to make 5 turret boards, what fun :D :D :D
As soon as I finish my current amps. She's next on the list. :D
Later,
Jac
(edit)
I'd love to see the chassis layout, once your done.


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PostPosted: Sun May 27, 2007 8:00 am 
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Wicksy that looks like a nice layout.Could you please send me a copy of your layout.I need a layout with LARGE LETTERS AND NUMBERS it is hell getting old :)

lheil@uiuc.edu

Keep us informed on your build.Are any of Phils mods incorporated into this layout? It will be in interesting to see your opinion on the 7/15 switching to see if it is worth doing.Will you be doing the AD15 in the future?

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Straycat


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PostPosted: Sun May 27, 2007 8:49 am 
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Quote:
Wicksy that looks like a nice layout.Could you please send me a copy of your layout.I need a layout with LARGE LETTERS AND NUMBERS it is hell getting old :)

lheil@uiuc.edu

Keep us informed on your build.Are any of Phils mods incorporated into this layout? It will be in interesting to see your opinion on the 7/15 switching to see if it is worth doing.Will you be doing the AD15 in the future?

Thanks
Straycat

Hey man, good to see you here! The layout as it stands has no mods to it at the moment. This is the stock layout. For my build i will be implementing the half power switch. Its simple enough with the PT i have since it has 0 - 190 - 275 taps on the secondary side. I will also try the mod with the cathode resistor using a DP switch on the power selector.

I'll get you the bmp file sent to you. Its 6.5Mb so i warn you it'll be big :wink: Coco said he'd host it though so i'll get it sent over to him aswell then everyone can download it.

Oh and i'll get to work on the AD15. The schem is a bit difficult to read so i'll see about copying it out into a more readable form then work a layout around it.

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PostPosted: Sun May 27, 2007 10:28 am 
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Quote:
For those who want to know, the Tiny Terror is a Class A tube head amp useing EL84 valves, switchable power output of 15 or 7-watts mean full crunched tube tone is available regardless of the output volume.

FYI any amp that produces 15W from a pair of EL84s is *not* Class A, despite what the marketing guys may try to tell us. A cathode-biased Class A amp with a pair of EL84s will produce around 10W. The Tiny Terror is therefore a Class AB amp, same as the AC15, Spitfire, Lightning and Marshall 18W. Maybe when it's running in reduced power mode, The Tiny Terror might be operating in true Class A - but only then.

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PostPosted: Sun May 27, 2007 10:37 am 
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Hosted Layout. Right click to download large size bmp drawing format.

http://www.trinityamps.com/ForumGallery ... v.1.11.jpg

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Last edited by coco on Mon May 28, 2007 9:57 am, edited 1 time in total.

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PostPosted: Sun May 27, 2007 10:51 am 
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Phil is right. Aiken also discusses this. [www.aikenamps.com]

"Picture a sine wave going positive above zero volts and then negative below zero volts. The way the tube is biased and the circuit is set up determines when the tube (or tubes) is on. It gets a bit shaky when you are dealing with push-pull, which uses tubes in pairs (or quartets, or more, always in multiples of two), or single-ended, which uses one tube (or more, but they are in parallel with the first one, not in push-pull).

Class A: All tubes are "on" for the entire sine wave, in either single-ended or push-pull. In single-ended class A, one tube (or two or more in parallel) amplifies the whole sine wave. In class A push-pull, one tube is "pushing", while the other tube is "pulling", but they are both on for the entire waveform. In push-pull class A, one tube amplifies the sine wave, the other amplifies an upside-down version of it (180 degrees out of phase), and the two complete signals are added together in the output transformer to produce a new sine wave of higher power than you could get with a single tube in the single-ended configuration. This class of operation is characterized by high-linearity and low distortion, which makes it ideal for audiophile-type gear, and very low efficiency (DC power in vs. AC signal out), which means you don't get a lot of watts for your money. All single-ended output stage guitar amps operate in class A mode.

Class B: This class is usually used for push-pull only, although you could have a single-ended class B amp, but it wouldn't sound very good for audio. In class B push-pull, on the top half of the sine wave, one tube is on ("pushing"), while the other tube is off ("idle"). Then, on the bottom half of the sine wave, the other tube is on ("pulling") while the first tube is off ("idle"). Essentially, one tube amplifies the top portion of the sine wave, while the other tube amplifies the bottom portion. The two "halves" are added together in the output transformer to make a new, completely-whole sine wave, so there is no clipping caused by the amplification of only half the wave by each tube. This mode is characterized by very high efficiency, so you get more power than you can in class A, and a type of distortion known as "crossover distortion", which is caused by the non-linear overlapping of the turn-off and turn-on times of the tubes.

Class AB: This class is sort of in-between class A and class B, where the tubes are biased higher than class B, but not as high as class A, so one tube still turns off at some point in the sine wave, but not at the exact zero crossing. This allows more "overlap" in the two halves, so there is little or no crossover distortion, but the efficiency is still much higher than class A, so you get more watts for your buck. Most push-pull guitar amps operate in class AB mode."


He also discusses this in more detail in his on-line article "Is the Vox AC-30 Really Class A?"

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PostPosted: Sun May 27, 2007 1:18 pm 
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The TT is just getting started and Phil's got mods already :shock: . Your quick Phil.
Could you please post them or direct me where they are.
:D
Thanks,
Jac


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PostPosted: Sun May 27, 2007 4:04 pm 
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Here are some mods fron the 18watt forum and the gearpage. Phils suggestions are in the middle starting with several cap values and end with taste.

I'm really not qualified to answer but just for the sake of my own education, I'll offer up my suggestions:

1. Move the "top" end of the .0001 cap between the first and second gain stages from the top of the volume pot to the more upstream end of that 68K resistor - this may only give a very marginal increase in brightness/

2. reduce the value of, or remove the .0047uf cap on the anode of the second gain stage.

You could also reduce the values of the cathode bypass caps in the preamp from 22uf down to 1uf or .68 but that's not more treble so much as less bass. Same goes for reducing those big .047 or .1uf coupling caps.

Unbeleivable what a better design that is than some of the modern epi or even some modern Marshall and Fender schems floating around, not sure I get why they put that .22uf cap on the grid of V1 though.

Simplest thing might be to just experiment with some different tubes or
speakers.

EDIT: by the way, that tone knob, if I'm looking at it correctly, doesn't actually give you
any treble boost, it only cuts treble out.


Several cap values need to be reduced. Change the cathode bypass caps in the preamp to around 1uF or 2.2uF. You could also experiment with lifting the 2nd preamp stage's bypass cap for some NFB. Change the two 0.047uF coupling caps between the preamp and PI to 0.022uF or maybe 0.01uF. The two 0.1uF caps going to the grids of the EL84s also need to be reduced to 0.022uF or even 0.01uF.

A couple of resistor values could also do with being changed. The 1.2k resistor on the PI cathodes will tend to make the PI distort in a fizzy way, and needs to be reduced to 820 ohms (like an 18W) or 470 ohms for a bit more crunch. I would also suggest reducing the 2nd preamp stage's cathode resistor to something between 620 and 1k ohms. 820 ohms might be a good value to start with. Lower values will give earlier distortion, and vice versa.

These are just some fairly obvious fixes that need doing, with some room for tweaking to taste.



It's an AC15, with an extra gain stage cascaded on the front end. PI and power amp are 100% AC15. The gain pot is a dual 500K that serves as simultaneous voltage dividers after each gain stage.


The amp is actually biased at over 15W per tube static. It's insane. I swapped the 100 ohm cathode resistor for a 180 ohm, made no difference in the sound but made the tubes a lot happier.

It selects a different HV tap on the PT secondary. One leg remains tied to one side of the bridge rectifier, the other side has two taps and the switch selects between them. The result is something like 250VDC rather than about 325VDC.

It affects the entire amp, not just the power tubes, and it does NOT do anything to the bias state - so, in stock form the amp is severely (IMO) underbiased in 15W mode, and just about right in 7W. But I think the low voltages affect the feel in a negative way.

I replaced the power switch with a DPDT and also switched a second cathode resistor in parallel when I selected 7W. That made both modes idle happily.
You're right, I omitted the master from my drawing. It's a 500K dual-pot post-PI master with an extra set of .1uF caps.

The power switch is on my drawing, it's on the HV secondary. It selects between two 'ends' of the winding - HV winds up with about 325V and LV about 250V.
I don't know how you'd affect only the voltage in the power amp since the switch selects a different HV tap on the power transformer.

180 ohms is a good choice at 15W power; I replaced the power select switch in mine with a DPDT (Mouser sells the same switch brand and family) and used the other pole to place a 100 ohm resistor in parallel with the 180 when I went down in power. Worked great.

I don't think there's much to gain with cap swaps, myself. And both of my transformers were crooked too!







....this time about the half power switch. I know how it works an all as i've read the schematic but has anyone with the amp noticed a discernable change in tone and gain when switching between half power and full power?

I ask this as theres a rather interesting mod someone has suggested which allows you to change the bias of the Tiny Terror when switching between the power levels.

Basically you change out the current cathode resistor (120 ohms) to a 180 ohms cathode resistor which runs the EL84s less hot on full power mode and change the power swtich to a double pole version. One pole handles the power switch while the other pole can bring in a 100Ohm resistor in parallel with the 180ohm cathode resistor. That way you have a consistent bias level between the different power levels. That mod would be simple for a tech to fit.


Several months back when I joined this forum, I posted a link for mods to the tiny terror, which included these above, since then they've posted a lot more.... Yes you do get a discernable change in tone ,switching from 7 to 15, and the bias voltage is the reason.

it's at the music electronics forum:-
http://music-electronics-forum.com/show ... php?t=1477

that's if the link still works...TTFN


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PostPosted: Sun May 27, 2007 5:24 pm 
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This is great thank you very much straycat,
How much fun is it to take a small great commercial amp and make iut better.
Love it.
Later,
Jac


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PostPosted: Sun May 27, 2007 6:16 pm 
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Cheers Stray cat. I've begun construction of the clone. I've already assembled the chassis from an old PC case. I just need to clean it up and drill out the holes and then spray it. I'm going to put up a build log here and probably over at the Plexi Palace. I doubt Orange would appreciate one on their forums :wink:

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PostPosted: Sun May 27, 2007 6:17 pm 
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Quote:
Hosted Layout. Right click to download large size bmp drawing format.

http://www.trinityamps.com/ForumGallery ... v.1.11.jpg

Thanks for hosting the layout Stephen!

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PostPosted: Sun May 27, 2007 6:46 pm 
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+1 for hosting, Thanks


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PostPosted: Sun May 27, 2007 7:00 pm 
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I figure the more people involved the better.Looking forward to seeing your build and hearing your comments on it. This is only being done for entertainment purposes only. The results might help orange like what happened with the valve junior.Good Luck!!


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PostPosted: Mon May 28, 2007 9:53 am 
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Thanks Straycat for finding my list of suggested mods. :lol: I couldn't find them myself, since I had posted them on 18watt.com, which is still locked while they fix some stuff there.

BTW I agree with the suggestion to use a 180 ohm cathode resistor on the EL84s. It still beats me how this amp has so many obvious mistakes in its design. Without those cap value reductions, it's going to mush up and get farty when cranked.

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