Anyone know what the "tiny terror" circuit is?

[Blue Rock]

TT valve change

Hi, I´m new here and think this forum is very interesting.

I changed valves on the TT to get the sound I wanted and finally came up with this: gain 12AU7 (Sino), PI 12AT7 (Sino). This combination took away the gain I never use anyway, I max out the gain knob and get a much smoother overdrive.
Now I can also max out the tone knob without sounding harsh. The amp reacts much better to SC and sounds great with HB. I also use an EQ to take away some bass and a booster to crank it some more if I want to, and it still sounds smooth. My TT is Korean made and hooked up to the Orange 1x12 that came with it. A great little amp/cabinet combo!

[Blue Rock]

Further...

With 12AX7 at PI it's even better, less compression and more attack, still with smooth overdrive. Gain at 2-3 o'clock, tone at max, volume 10 o'clock (15 W setting).
This is a Terror I like!

[strangebru]

can the TT tone be brightened?

so, has anyone tried to mod the tone circuit to brighten the mid/hi response? great amp, but a really foggy tone and not much authority in the tone circuit
Cheers
mak

I was wondering the same thing, but I didn't see an answer here. Can the TT tone be permanently brightened without adding a full tone circuit. I am assuming that the tone circuit passes all high freq when full up, but is there a cap that can be changed somewhere that would help?

[John G]

Hi,
Try removing the cap off the second gain stage or reducing its value. The schem shows it as a 4.7nF cap which will bypass alot of the highs.
Try also shifting the position of the tone cut control from the wipers of the master volume control to the input side of the control, much more activity.
I can send you a schem of my TT clone and modifications if you want, just PM me.
Cheers,
John G

[Thomeeque]

The schem shows it as a 4.7nF cap

Which schem? AdmiralB's OTT.pdf shows 470pF..

[John G]

Hi,
The value I got was from a pdf circuit that was based on the Admrial's and is definetly a .0047uF. (C6)
I agree it should be a 470pF or none at all.
In looking at the whole schem I can't help wonder as to the acuracy of some of the component values given ?? As to the tone cut control in its present state it will only come into effect when the master control is used past about two thirds CW rotation.........I would think it was designed to work this way.
John G

[Thomeeque]

Hi,
The value I got was from a pdf circuit that was based on the Admrial's and is definetly a .0047uF. (C6)

There is probably more Admiral's TT schematics traveling around "Mine" does not contain part numbering (aka C6):
http://r.clear.home.insightbb.com/OTT.pdf Could you link "yours" pdf, please?

I agree it should be a 470pF or none at all.

I'll try both variants in my clone (when it's ready) - I'd expect this cap significantly influences final sound..

In looking at the whole schem I can't help wonder as to the acuracy of some of the component values given ?? As to the tone cut control in its present state it will only come into effect when the master control is used past about two thirds CW rotation.........I would think it was designed to work this way.
John G

I've seen already this setup in some other schematics (some old Marshall?), but I don't remember details..

T.

[strangebru]

confused

There is probably more Admiral's TT schematics traveling around "Mine" does not contain part numbering (aka C6):
http://r.clear.home.insightbb.com/OTT.pdf Could you link "yours" pdf, please?

Because of the confusion on the value of this cap (and my nubeeness), I'm not sure which one we're talking about. On the, "Mine" schematic, can you describe where it is located. I see the 470pF cap (that T. mentioned) in parallel with a 100k resistor and both next to the D branch. Is that it?

[Thomeeque]

Because of the confusion on the value of this cap (and my nubeeness), I'm not sure which one we're talking about. On the, "Mine" schematic, can you describe where it is located. I see the 470pF cap (that T. mentioned) in parallel with a 100k resistor and both next to the D branch. Is that it?

Yes (or at least I am talking about this cap )

[sjwebb90]

Re:Admirals posting earlier on in the thread about bias.

I have measured the bias values on the EL84's of the Tiny Terror and it is indeed has a Plate dissipation of 15 Watts when in the 15W mode and is about 8Watts when in the 7Watt mode. Nominal Plate voltage for EL84's should be 12Watts.

Also to my ears the TT does sound a bit fizzy when distorted and the remedy appears to be, lower the 1.5 ohm resistor to 820 Ohms on the Phase Invertor, which I have done. For a more plexi crunch you could lower the value further to 470 Ohms. After trying both I stuck with the 820 Ohms. The fix also opens the amplifier up offering more clarity.

Cheers
SJ

[John G]

SJ,
In the schem I sent Thomas I have incorporated a DPDT toggle switch so that I can select the standard splitter tail resistor values and have these option of throwing the switch to shunt the tail resistors and lowering the resistor values to that of a Marshall ie 470 ohm, and 15K ( there is no feedback connection so no 10K,4K7 split) Makes a bit of a "plop" when you throw it on the fly but is not a Major.
You are right if you want better head room at this point then Marshall values are the way to go.
If you think the O/P tubes are over dissapated then up the cathode resistor in the Hi power mode and take it down(via the power select switch DPDT) for the lower power option as has been suggested in the thread ealier.
Cheers,
John

[sjwebb90]

John thanks for your reply.

Strangely, I was looking at the Cathode bias resistor "verses" plate discipation earlier in the day.

EL Teye observations on an earlier thread appear to have some foundation when "he" changed the Bias resistor to 180 Ohm
Quote "My amp lost punch, bite, and some volume in the 15Watt setting.

My test on 15W setting :
I placed a Rheostat in line with the 120ohm resistor so I could heard any difference on the fly. The amp was set to a clean sound.

With bias resistor set at 180 Ohm and the plate discipation measuring the nominal 12 Watts, there was definitley a lack of sparkle and the strings seemed a bit muted. Moving the rheostat back and forth between the setting
180ohm and 120 ohm you could hear a audible difference.

I am a bit puzzled with that at the moment, because if everything is running at optimum you would expect to get a better tone. Also with the Plate running at 15 watts in the 15W mode the valve life will be reduced which is a distinct negative.

Luckily at the moment I use it soley as a practice amp at the 7W setting.

Out of curiousity, has anyone else done any direct A/B testing on the fly of 120 verses 180 and detected any difference?

[Thomeeque]

As to the tone cut control in its present state it will only come into effect when the master control is used past about two thirds CW rotation.........I would think it was designed to work this way.
John G

Yesterday I've seen other OTT schematic, where "tone cut" control was first on signal path before "master volume" pots. I don't know if AdmiralB made mistake when drawing his schematics or if this is difference between OTT revisions.

[stavo]

Cheers thom for the info, i have just repaired i think? the pot but we have another problem now, i think one of the el84's has gone but i cant work out which one? if i put only one in nothing happens but when i change it to the other (also on its own) it starts to smoke one of the 470 ohm 5 watt resistors i think these two (one for each valve) connected in series are the screen? one tests now only 360 ohms could this be the cause for the smoking of this resistor? or is the valve gone? and the other valve which does nothing is good or what? i dunno i am confused? help!!!! please or anyone, cheers stavo.

No worry's guys i have fixed the little bastard!!! Now to build my own 20 watter!

[Blue Rock]

Tried pulling the bright cap, to cut some of the high end (so subjective, and other people want MORE upper mids?!?!?)

Hi! Where do you mean "the bright cap" is located?