Anyone know what the "tiny terror" circuit is?

[iWishmaster]

Allright, it seems to be working, I did some basic research on the net and found what was wrong. Guess I really should use google before asking stupid questions.

I use 1 tungsoll tube (for the preamp) and 1 jj tube for the PI. The jj light's up (a little) when I flip the switch for the heaters (no high voltage yet), but the tunsgsoll remains dark. I swapped the tubes, same problem. However, I cannot see the actual heater connections inside the tube on the tungsoll, since the plate surrounds it completely. On the jj I can see some glowing pins. Is the tungsoll dead or could this be normal?

Tube was dead -> replaced with a new one/

Second, the EL84's (also jj) become so hot I nearly burn myself when touching them. There's still no high voltage (standy switch is off and wired properly). I measured the heater voltage and it's 6.8V under load, 7.3 without load (when no tubes are inserted). I know they're supposed to be quite warm, but not painfully hot, right?

Normal behaviour for power tubes, first hit on google had the answer.

edit: When rechecking some connections, I notice a pin had broken off on the PI resistors, I happen not to have any left, off to the shop agan tomorrow...

Fixed.

The amp works, though I only have a small 3W speaker to test it on, there's definately some sound. Since the volume is about the same as whispering and the fact that there is some 50Hz noise (hopefully it won't be as bad with real speakers) there's no telling if it actually sounds good, but hey, it works, I'm happy for now
Now to buy a nice little cab and start tweaking! Thanks for the help!

[Thomeeque]

Allright, I finished all the resoldering, finally! I couldn't have build this thing without all the help I got here so far! But, it's just 'finished', not quite working yet...

The problems:

I use 1 tungsoll tube (for the preamp) and 1 jj tube for the PI. The jj light's up (a little) when I flip the switch for the heaters (no high voltage yet), but the tunsgsoll remains dark. I swapped the tubes, same problem. However, I cannot see the actual heater connections inside the tube on the tungsoll, since the plate surrounds it completely. On the jj I can see some glowing pins. Is the tungsoll dead or could this be normal?

You can try to measure tungsoll's filament by ohm-meter, if it's conducting or burned.. Second check could be if it remains cold or gets warm (compare with JJ)

Second, the EL84's (also jj) become so hot I nearly burn myself when touching them. There's still no high voltage (standy switch is off and wired properly). I measured the heater voltage and it's 6.8V under load, 7.3 without load (when no tubes are inserted). I know they're supposed to be quite warm, but not painfully hot, right?

EL84 gets very hot even for specified voltage (6.3V), there's more current going thru compared to pre-amp tubes (see spec), almost 5 Watts (6.3 x 0.76) are turned to heat there (it's under 2 Watts for ECC83).. So you can probably stay calm for now (after you make it work completely, you should measure it under full load again and try to lower voltage (by adding some "ballast") to 6.3 Volts - it's not very healthy for tubes to run filament on higher voltage then specified).

I figured I'd try it real quickly before turning of the amp completely: I connected the guitar, but no sound, just a light humm coming from the speaker.
edit: When rechecking some connections, I notice a pin had broken off on the PI resistors, I happen not to have any left, off to the shop agan tomorrow...

Any thoughts?

Did you fixed it already? What happened?

T.

[Thomeeque]

Cool, telepathy definitely works

[iWishmaster]

Cool, telepathy definitely works

Haha, apparently it does!

Thanks for the tip on the filament voltage though. I'll add some extra resistance later on.

Btw, shouldn't all (older) amps suffer from increased filament voltage? Plexi's for instace were made for 110V, but since then the mains voltage in the UK has gone up to about 115V. This should result in a filament voltage of 115/110 * 6.3 = ~6.6
It's not much, but it'll hurt the tubes at least a little bit, and the B+ also goes up by a little. I doubt it'll hurt the sound much, but it might change a little since the tubes run hotter.
But that's just thinking out loud and it's about time to hush those 'thinking sounds' with some good ol' guitar roaring!

[iWishmaster]

Back again ...

I finished building the amp and tested it on a 1x12" cab. The sound was good, but there was a _lot_ of hum and shortly after building it, it broke down as a result of poor internal design. So I decided redesign the internal layout and redo all the soldering work. I finished all the work, but now, the amp doesn't produce any sound and can't seem to find the problem. Here's what I tried / concluded sofar:

-The tube filaments glow as they should
-The internal DC voltages (power supply) are correct (though somewhat lower with load, which is to be expected)
-There is a very mild hum coming from the speaker. Turning the gain knob clockwise makes the humm slightly louder (expected behaviour). Turning the tone knob clockwise decreases the humm slightly. Turning the volume knob does absolutely nothing.
-Plugging in the guitar decreases the humm slightly.
-Tested the guitar / cable on a different amp: works.
-I don't have access to another speaker cab, so I can't test it, but the cab is brand new, so I doubt it's broken.

As far as I can tell all the connections are correct (I haven't finished checking the entire signal path though, only the preamp, which seems to be correct, I plan on doing the power amp tonight). Any thoughts on what the problem could be? The tubes have taken quite a hit due to some design faults earlier (see previous posts), can I measure somehow whether they are dead or not? Any clues on what the problem could be, or where I can start looking?

Thanks in advance!

Roy

[Yvoshkiro]

does anyone have the spec's for the power transformer needed for this amp?
(incl 7/15 switch?)
,
tnxz

[gtrbryan]

Tiny Terror Tone Control

I've been following this thread, looking at the schematics. The tone control on this is something I havent' seen before. I can't tell from the schematics how you sould wire this. Should you ground pin 3 of the pot as in the gain and volume controls? Should you just use pins 1 and 2 and leave off 3 entirely?

Also, I assume that both #3 pins of the volume pots(s) go to ground. Am I correct? Thanks.

[Thomeeque]

Hi!

I've been following this thread, looking at the schematics. The tone control on this is something I havent' seen before. I can't tell from the schematics how you sould wire this. Should you ground pin 3 of the pot as in the gain and volume controls?

No

Should you just use pins 1 and 2 and leave off 3 entirely?

Yes (or you can connect pin 3 with pin 2)

Also, I assume that both #3 pins of the volume pots(s) go to ground. Am I correct?

Yes

Thanks.

You're welcome! Good luck with your build, T.

[calis]

Less compression, more bightness and clarity

Hey guys.

This is my frist time to post on this forum. I just received my Tiny Terror and it's a great little amp. However, it is lacking for me in a few areas.

As others have complained about, the clean sound is too muffled for me. I own a Vox AC30 and really like the cleans that I get outta that amp: really clean and clear. If the TT is based off the AC15, it seems like I should be able to get similar cleans, right? I am wondering what everyone thinks about the mods they have tried thus far to brighten up the amplifier when clean.

Also, I really enjoy how responsive the AC30 is to my playing style. I feel like the TT is a bit flat and compressed feeling. So, I wonder if there is any way to get it to be less compressed and more responsive.

I should also mention that the amp has way more gain than I need. The MAX amount of gain I would use is right around 1 or 2 o'clock when I have my Gibson SG with P-90s plugged into it. So, I would be totally open to using lower gain tubes if that will help me to get a bright, clearer, less compressed, more AC15/AC30 kinda feel outta the amp.

So, what do you think will be my best bet? Should I change the bright cap? Or is a tube change in order? Or both maybe? Please let me know what you guys think. I really appreciate any input you have to offer. Thanks very much.

Justin

[gtrbryan]

A couple more Tiny Terror Questions

Has anyone looked at an actual TT Power Transformer and determined what the secondaries are for the 15 and 7 Watt? I would assume that the 15 Watt is 250 ac which would give you roughly 325 dc at B+, but what lower value is used for the 7 watt?

Also, what is the primary value of the Output transformer? I have a OT for an 18 Watt Marshall with 8000 primary. I assume this would work?

Finally, I've seen posts for 100k audio and 500k audio dual pots for the master volume control. Has anyone tried both? Which works better?

[Oscar]

Hi there, this is my first post here, and lately in my spare time i have been attampting to build a tiny terror as a first project. However, my main concern is my PT; I have a 290-215-0-215-290 PT, and was wondering if it was suitable for this amp, if i used a DPDT switch with an off selector as my standby switch, with the like wires of the PT on the same side of the switch, and then the middle two poles of the switch going to opposite sides of the rectifier, and the CT grounded? Any help would be much appreciated, thanks in advance

[Thomeeque]

Hey guys.

This is my frist time to post on this forum. I just received my Tiny Terror and it's a great little amp. However, it is lacking for me in a few areas.

As others have complained about, the clean sound is too muffled for me. I own a Vox AC30 and really like the cleans that I get outta that amp: really clean and clear. If the TT is based off the AC15, it seems like I should be able to get similar cleans, right? I am wondering what everyone thinks about the mods they have tried thus far to brighten up the amplifier when clean.

Also, I really enjoy how responsive the AC30 is to my playing style. I feel like the TT is a bit flat and compressed feeling. So, I wonder if there is any way to get it to be less compressed and more responsive.

I should also mention that the amp has way more gain than I need. The MAX amount of gain I would use is right around 1 or 2 o'clock when I have my Gibson SG with P-90s plugged into it. So, I would be totally open to using lower gain tubes if that will help me to get a bright, clearer, less compressed, more AC15/AC30 kinda feel outta the amp.

So, what do you think will be my best bet? Should I change the bright cap? Or is a tube change in order? Or both maybe? Please let me know what you guys think. I really appreciate any input you have to offer. Thanks very much.

Justin

Hi! What exact AC30 model and what of it's inputs (normal/bright/tremolo) are you referring to?

[Thomeeque]

Has anyone looked at an actual TT Power Transformer and determined what the secondaries are for the 15 and 7 Watt? I would assume that the 15 Watt is 250 ac which would give you roughly 325 dc at B+, but what lower value is used for the 7 watt?

Unfortunately I don't know exact OTT values, but I believe you should have 250V/150mA secondary with 175V branch (it should give around 245VDC, what is approximately value which somebody here measured for 7Watt mode).

Also, what is the primary value of the Output transformer? I have a OT for an 18 Watt Marshall with 8000 primary. I assume this would work?

No idea, maybe somebody else?

Finally, I've seen posts for 100k audio and 500k audio dual pots for the master volume control. Has anyone tried both? Which works better?

I did not, but maaaaaybe 500K should allow slightly more gain (less load resistance) and 100K slightly more heights (less input capacitance) on PI stage, but it would need some deeper study (start here )

[Thomeeque]

I've seen real OTT today (bought by my friend yesterday), label on PT states 250VAC secondary with 185VAC tap (unfortunately nothing about current). Thmq

[Thomeeque]

Hi there, this is my first post here, and lately in my spare time i have been attampting to build a tiny terror as a first project. However, my main concern is my PT; I have a 290-215-0-215-290 PT, and was wondering if it was suitable for this amp, if i used a DPDT switch with an off selector as my standby switch, with the like wires of the PT on the same side of the switch, and then the middle two poles of the switch going to opposite sides of the rectifier, and the CT grounded? Any help would be much appreciated, thanks in advance

Hi! I'm not sure if I understand your description, but I see two ways how to do "15W/St.By/7W" switch with your PT (I'd prefer second):



But you have bigger problem: voltage of your PT is too high (on first filtering cap you would get approx. 407/301VDC instead of OTT's 350/259VDC*), you'd need to drop it somehow by cca 50-60 Volts (you probably do not have to be absolutely accurate here, depends on how much you want to get close to master and/or on circuitry limits, which I don't know)**. I'm not sure what would be the best way, maybe some (Zener) diode(s)..? Current there is around 100-200mA..

Good luck, T.

*VDC = Sqrt(2) * (VAC-2)

** If you want to be accurate, you can tweak voltage drop for each mode individually (2nd circuit allows it better)..