Anyone know what the "tiny terror" circuit is?

[shinybulldozer]

Hey guys. ive been looking at this thread for a while and noticed the weird way the ott uses to switch power. its been said many times that flipping around voltages would mess with the bias of the pre and power stages. since ive got so much information about the ott (namely schematic) ive decided its my turn to contribute.

this amp is using el84s in a push pull configuration, a very good way of just lowering the power of the tubes without effecting the bias of the rest of the amp would be to put a switch that ties the screen and the anode together. this converts the pentode to a triode effectively halving the power output.

ill include an example schematic if anyone needs any help.

[ciambom]

Fx-loop issues

Before in this thread someone spoke about a passive fx-loop.
I put it in my clone and it doesn't work perfectly..
If I put an Od box (MXR Dist+) in the loop, the volume lows and the compression rises a lot.
This can be due to the high signal voltage level that enters in the pedal.
Unfortunately I don't have an oscilloscope at home. Can anyone measure the voltage level before the PI with the gain at max??
The only way to make a good fx-loop is to attenuate the signal before the Send and to amplify it after the Return.
I would make it by using power mosfets.

Someone has already tried that?

[ciambom]

Some fixies

First: I fitted a Mosfet fx-loop, it seems to work properly, it's clear and there is no difference between the active and bypassed status

Second: previously in this thread someone was speaking about the bright cap.
I'm referring to the Thom schematics:
http://thmq.mysteria.cz/diystompboxe...w_PNs_1024.gif

the cap is C4: 100pF, by rising up its value - i tried 390pF - the amp becomes much more bright, this is good for low gain settings, but turning up the gain pot the amp sounds very bad. Too many high frequencies make the sound too sharp.
I suggest to put a bright switch to change that cap value only when the clean tone is used.

[Thomeeque]

First: I fitted a Mosfet fx-loop, it seems to work properly, it's clear and there is no difference between the active and bypassed status

Hi! Cool, which Mosfet fx-loop did you fitted in?

Second: previously in this thread someone was speaking about the bright cap.
I'm referring to the Thom schematics:
http://thmq.mysteria.cz/diystompboxe...w_PNs_1024.gif

the cap is C4: 100pF, by rising up its value - i tried 390pF - the amp becomes much more bright, this is good for low gain settings, but turning up the gain pot the amp sounds very bad. Too many high frequencies make the sound too sharp.
I suggest to put a bright switch to change that cap value only when the clean tone is used.

Yep, and why not to use on-off-on toggle to switch 100p/none/390p

Other possibility is to have two gain pots instead dual one, then you can dial more gain with bright boost or without..

Or both of them

Cheers, T.

[ciambom]

Hi! Cool, which Mosfet fx-loop did you fitted in?



Yep, and why not to use on-off-on toggle to switch 100p/none/390p

Other possibility is to have two gain pots instead dual one, then you can dial more gain with bright boost or without..

Or both of them

Cheers, T.

1) I put a self designed fx-loop. I posted it in another forum and I can't post it here.
As soon as I will draw the schematic I will sent you by mail.


2) I can't put a switch because now I can't drill the chassis again..

And now..
Since you built a versatile and configurable amp, you can answer to a pair of questions:

- leaving your second gain pot at max and only turning the first gain pot, is it possible to have clean tones?? What about the amp behaviour with this conf?

- now I'm using the PI with the cathode resistor at 820 ohm instead of 1.2K. Do you think that is it better to lower this value to 470 ohm?

Thanks,

[Thomeeque]

And now..
Since you built a versatile and configurable amp, you can answer to a pair of questions:

- leaving your second gain pot at max and only turning the first gain pot, is it possible to have clean tones??

Yes, when you set G1 really really low..

What about the amp behaviour with this conf?

Well, I'm not sure - behaves normally, sounds little different than clean set by lowering both gains of course.. but I did just quick check, I'll try again and let you know..

Why do you ask about this configuration?

- now I'm using the PI with the cathode resistor at 820 ohm instead of 1.2K. Do you think that is it better to lower this value to 470 ohm?

Hmm, define "better" With lower value PI has more headroom but less distortion - I assume that original OTT aims for more distortion (to be able to get heavy enough distortion without need of two lamps in the preamp) and that's why there is 1k2. I switch from 1k2 to 487R (1k2 and 820R in parallel) and I'm glad I have both options there. With 820R you are somewhere in the middle which may be perfect for you, depends really on your preferencies.

Thanks,

You're welcome! T.

[kg6epv]

Beautiful!

That is a beautiful amp, Thomeeque... all the best! Bob, Transformer Design and Supply
www.transformerdesignandsupply.com

[Luqqas]

Hi there Thomeeque! I've started to build this clone and although I've read this entire thread and all the questions and answers, still I have some misplaced points:

1. MFTech posted a schem (this http://thmq.mysteria.cz/diystompboxes.com/OTT/TT15.jpg) which have the voltage values of capacitors at in power section (C15, C16, C17, C18). But what I don't have is the voltage values of the rest of caps (from C1 to C13) and C14 in between the rectifier diodes doesn't have his value too.

2. Same issue with the Watts of resistance. In the schem that you made so neat http://thmq.mysteria.cz/diystompboxe...w_PNs_1024.gif, the only resistor with Watts value is R27. Wich will be the Watts range for the others ones (pre amp included)?

Thanks a lot and I promise pics from my work.
Greetings!

[Jazz P Bass]

Resistors unless noted are 1/4 watt.
The cathode bypass caps (C9 & 11) can be 25volt.
The coupling caps have to resist the dc plate voltage.
So the minimum rating should be the able to handle the full B+ voltage.
400v or 600v will work.

[Luqqas]

Thanks for the answer Jazz P Bass.

Resistors unless noted are 1/4 watt.
The cathode bypass caps (C9 & 11) can be 25volt.
The coupling caps have to resist the dc plate voltage.
So the minimum rating should be the able to handle the full B+ voltage.
400v or 600v will work.

By C9 you mean 0.47 uF and C11 .1uF? Those are the cathode bypass caps? I'm a little confused.

With resistors I'm more confuse now, because in the pics posted in page 5 of this thread, there was 470 Ohm 5W from the EL84 (shown as R22 and R23). Also,
theres was 100 Ohm 3W resistors, which I deduce are from the filaments. Here the pics:

Made In Korea Tiny Terror Circuit With Bias Mod. (150 Ohm since replaced with a 160 Ohm resistor) | Flickr - Photo Sharing!

Cathode Bias Resistor 150 Ohms (Now 160 Ohm) | Flickr - Photo Sharing!

DPDT Switch & 100 Ohm Resistor (Now 68 Ohm) | Flickr - Photo Sharing!

[I know that I know that there is a mod in those pics, but still help as a guide]

Hope you can help to make this thread more complete!!

[Jazz P Bass]

Are we using the same schematic?
The one that you posted lists C9 as a 22uf bypass capacitor of the first triode.
the second triode lists the bypass cap as C11, also 22uf.
25 volts is fine.
The 220uf bypass cap across the output tube cathode resistor should be 50 volt.
The cathode resistor wattage is not marked.
Depending on the current draw you may need a 25 watt resistor.
And yes the screen resistors should be 5 watts.

[martin.sadler]

Has anyone tried a single 1 Meg pot in place of Master Volume (P3a+b)

I've just spent a very enjoyable couple of days reading through this thread - some very useful stuff here. I've seen no mention of this but I'm curious - has anyone tried replacing the dual 500kA P3 with a single 1MegA wired as a rheostat across the to PI outputs with no connection to ground? I've seen this in one of Kevin O'Connor's TUT books and IIRC it was used by Marshall on the 18w "Studio" 4001. I know that it probably won't give a true zero due to slight differences in the amplitude of the two PI outputs but I don't consider this important - it'll be quiet enough for most practical purposes.

From what I can see (I'll do some simulation when I get chance) it shouldn't have any effect on the tonal quality as it's essentially presenting the same load conditions to the PI as in the stock configuration - or is it?

Just a thought....

[The Red Terror]

Nice thread, Planning Tiny Terror Clone Build

I'm a student of Electronics Technology, and I'm planning a Tiny Terror clone build, despite the fact that I already own one and Tiny Terror clones have been beaten to death. I just find there's much to be desired in the Chinese PCB version, and I know coz I've tried earlier productions which were much tighter and far more impressive than the example I have at home. I'm hoping I can build a really tight handwired clone with really nice quality components, like hand wound dry caps, as opposed to cheap Chinese made electrolytics, as found in my PCB Tiny Terror.

I come here with some questions. I've found plenty of schematics, but no parts lists. The components are on the schematics, of course, but I'm still fairly new to electronics, and fresher yet to tube amp building, and there are a number of different types of components that can satisfy the values on the schematic. I'm gonna use SoZo mustard caps, as they're very highly regarded and very popular for Tiny Terror clones. But they don't come in all the values required for this build, so clearly more than one type will be necessary. The same can be said for resistors, diodes, potentiometers, etc. I was just wondering what different builders here have used, what works well, and what comes most highly recommended.

Still thinking things out and searching for parts, prices and tools. I plan on getting Mercury Magnetics' Tiny Terror upgrade kit for my transformers. Looking into solid silver 22 AWG conductor wire. Stranded copper's cheaper and more durable, of course, but I feel solidcore is superior for a number of reasons. Kind of unsure of which solder I should use. To be perfectly honest, I've never actually successfully soldered a complete circuit, but I'll go for broke. Any recommendations, resources, and tips are welcome, even just general tube amp basics and resources.

Thanks in advance,
The Red Terror

[J M Fahey]

Hi Red Terror.
Welcome to a nice Hobby.
Please do not get carried away by salesmen babble.
Use good, regular parts which you can source at any recognized supplier such as Mouser and others like it.
Today "generic" means very good, monster Companies have concentrated manufacturing under one roof, so to speak, parts are made by the billions, it does not pay for them to make unreliable parts which bring sales cancelations, their best business is to make them good, cash them and concentrate on the next batch.
A, say, $1.25 capacitor (sourced there) will be better than a rock bottom priced 25 cent "Saturday Special" one, no doubt, but a $60 one, same specs but labelled "Vintage" or painted in some "magic" color wonīt be any better.
For Godīs sake, forget about hand wound caps and stuff like that, itīs not 1914 !!!
Solid silver wonīt sound better than regular copper wire.
Same with "Mojo" solder.
After all, itīs a guitar amp.
And the Tiny Terrors you liked were certainly built at the Factory using good but regular parts.
Sound is much more in the project itself than on individual parts (provided they are adequate, of course).
Good luck.

[The Red Terror]

Hi Red Terror.
Welcome to a nice Hobby.
Please do not get carried away by salesmen babble.
Use good, regular parts which you can source at any recognized supplier such as Mouser and others like it.
Today "generic" means very good, monster Companies have concentrated manufacturing under one roof, so to speak, parts are made by the billions, it does not pay for them to make unreliable parts which bring sales cancelations, their best business is to make them good, cash them and concentrate on the next batch.
A, say, $1.25 capacitor (sourced there) will be better than a rock bottom priced 25 cent "Saturday Special" one, no doubt, but a $60 one, same specs but labelled "Vintage" or painted in some "magic" color wonīt be any better.
For Godīs sake, forget about hand wound caps and stuff like that, itīs not 1914 !!!
Solid silver wonīt sound better than regular copper wire.
Same with "Mojo" solder.
After all, itīs a guitar amp.
And the Tiny Terrors you liked were certainly built at the Factory using good but regular parts.
Sound is much more in the project itself than on individual parts (provided they are adequate, of course).
Good luck.

Hiya! Thanks for the speedy reply. I didn't mean to be so rough on my li'l Tiny Terror, there's a lot of awesome coming out of it, and believe me, I'm grateful for that; there's a reason I bought it. And I'm quite certain the difference between copper and silver is microscopically marginal, but I have really good ears and am ready, willing and able to spend a little extra at the very least on silver-plated copper solidcore conductors to achieve a really awesome point-to-point connection. I know that must sound absurd to any hobbyist on a budget, but I just want extremely great-sounding and lasting equipment, and I'm going out of my way to learn an art form with the noblest of intentions. :B

That said, I'm definitely not gonna pay more than two or three bucks for common components, depending. I really ask simply because I know nothing of the typical when it comes to components and their manufacture, so forgive me if my freshness to it all is indiscreetly apparent. Money will be saved where possible. I already came to the conclusion that good solder and a good soldering iron, for that matter, don't have to run up the tab, for example. I don't doubt that there are lots of modestly priced components which act and sound great, but there are so many different kinds, I kinda don't know where to begin in a lot of ways, and I mostly wonder if there are certain caps and resistors that are better suited to this design?

Your reply was most informative and helpful in a lot of ways, but quite vague for my needs at present. I dunno if you could relate to me ones that you use and like in specific schematical situations? Or perhaps builds of your own, generally? I have a pretty good understanding of the relationship of forces and components in circuits, but I don't know much about them themselves, and feel confidant in my abilities, but not in my sensibilities, yadidi?

Thanks again,
The Red Terror :B