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Anyone come across a full schematic for this thing yet? I cannot seem to find one. I have a tiny terror schematic so I know the preamp layout, but I am curious as to the SS power amp. I saw a video that said they are using a JFET based power amp that simulates the 'tube sound'.

Power amp is Class-D.

I'm not sure about class D, PA looks like TDA or LM based

http://www.squier-talk.com/forum/amp-ri ... error.html

more pics from that thread...

Looks like the STA540



Interesting IC/choice (esp for a mono guitar amp): http://www.st.com/web/en/resource/techn ... 171346.pdf

I have one of these if anyone wants better pics of the guts.

I've tried to improve the visibility of the chip designations
it surly looks like STA540

Cant see anything that looks like a SMPS. So what B+ is the tube using?

bato001 wrote:I have one of these if anyone wants better pics of the guts.

That'd be nice if you have the time and don't mind opening yours up to look inside.

What do you think of it? I've been tempted to buy one myself, thinking it may give a good overdrive/distortion sound at lower/house volume?

I've come to wonder if a solid state amp (or power amp section) is the best option for that...and I've also come to think solid state guitar amps should/could sound a lot better than I've personally encountered up to now (from reading bits on Rod Elliot's site and bits on Lenard audio and having started building a couple of audio/hifi amps).

Some of the online demos I've listened to of the Micro Terror have sounded pretty good to me... but others haven't so I've been undecided about it (why I was nosing about to see what's inside).

johnnyg wrote:

bato001 wrote:I have one of these if anyone wants better pics of the guts.

That'd be nice if you have the time and don't mind opening yours up to look inside.

What do you think of it? I've been tempted to buy one myself, thinking it may give a good overdrive/distortion sound at lower/house volume?

I've come to wonder if a solid state amp (or power amp section) is the best option for that...and I've also come to think solid state guitar amps should/could sound a lot better than I've personally encountered up to now (from reading bits on Rod Elliot's site and bits on Lenard audio and having started building a couple of audio/hifi amps).

Some of the online demos I've listened to of the Micro Terror have sounded pretty good to me... but others haven't so I've been undecided about it (why I was nosing about to see what's inside).

I like the Micro Terror. It gives a good classic crunch at bedroom volumes and at higher volumes does an excellent job of giving a classic rock growl. It lacks low end and no matter what you do with the tone it has alot of mids, but that is what gives it that classic rock Orange tone. As always, the better the speaker cabinet, the better the sound. I have a Vox AC4 cab and an Egnator Tweaker 15 cab and the amp sounds better through the Egnator with the G12H-30 speaker. Though I always run it through both mini-stack style.

For gigging or playing with a full band I still prefer my Custom Blues 30, but the Micro Terror is cheap and has that classic Orange tone and doesn't need to be cranked like the Custom Blues 30 to get good tone.

I will get some gut shots over the next few days and post them here.

tonyharker wrote:Cant see anything that looks like a SMPS. So what B+ is the tube using?

SMPS is a seperate psu. Prob just a brick like supplied with laptops. Says 15v dc on rear of amp I think.

Sta540 looks like it runs off a single DC supply, anywhere between 8 to 22v(?). Can only see a single voltage reg in micro terror... No neg rail it seems. Other chip amps, tda2030 lm3886 yadda yadda, require dual / split rail supplies. Wld seem logical that sta540 was used, in part at least, 'cos of simple power supply.

The chip amps (gainclones etc), are just amazing things (cost/time/reward equation).

Don't know if dc is raised with a charge pump for valve... never run a valve at puny voltages myself but others use them in stompboxes

bato001 wrote: I like the Micro Terror. It gives a good classic crunch at bedroom volumes and at higher volumes does an excellent job of giving a classic rock growl. It lacks low end and no matter what you do with the tone it has alot of mids, but that is what gives it that classic rock Orange tone. As always, the better the speaker cabinet, the better the sound. I have a Vox AC4 cab and an Egnator Tweaker 15 cab and the amp sounds better through the Egnator with the G12H-30 speaker. Though I always run it through both mini-stack style.

For gigging or playing with a full band I still prefer my Custom Blues 30, but the Micro Terror is cheap and has that classic Orange tone and doesn't need to be cranked like the Custom Blues 30 to get good tone.

I will get some gut shots over the next few days and post them here.

Sounds tempting, appreciate your thoughts. Undecided whether the blackstar 1watt /12at7 thing could be a better option for what I'm after. Will have to try em out.

Well, I was sure they're using these fancy combined valves - you know triode/pentode in one glass. I'm kind of disappointed from designing point of view

sinner wrote:Well, I was sure they're using these fancy combined valves - you know triode/pentode in one glass. I'm kind of disappointed from designing point of view

Bland mass production, established formulae or expectations and marketing yadda yadda

I may be wrong, but I don't think the combined valves like the ecl86 are back in production (seems highly unlikely they ever will be either .

One could make one's own amp using such a valve though

http://www.r-type.org/articles/art-007.htm
An OT source:
http://www.vvttransformers.co.uk/output_se_tx.htm

Seems like a good design to me.

STA540 is not an ordinary chip amp. It has a built-in soft limiter, which is really needed for SS guitar amplification.

Took mine apart last night to get pics and could not do any better than what is currently posted here without removing the board. At some point I may get ambitious and take the board out, but I have not been too lucky in the past messing around inside my amplifiers so I am keeping my curiosity in check for now.

Checked it out online based on the pix. The STA540 is a class AB with four amps rated at 13 watts into 2 ohms with a 15 volt supply.

Assuming they are bridging, calling it 20 watts at 4 ohms is probably right. I also assume they are ignoring the second amp.

I just got one for Christmas, but I haven't had the cover off, yet. When I do, I'll take some measurements and try to satisfy some of the open questions posted.

If it is truly only using one bridged pair of amps, I'll give thought to making it 'stereo' once the warranty is out. It's a bummer to wait a whole year for that...

teecee

Googled for micro terror schematics and stumbled upon this thread.
I took a look in my Micro Terror and did a little live probing .
The solid state power stage is indeed a STA540.
There is also a 7812 voltage regulator.
The 3 op amps (JRC45XX) run off the full 15 volts, so does the STA540.

The interesting thing is the valve plate voltages measured in the 9v-10v range which is a little disappointing .
I tried a 19V laptop supply but the tube plate voltages barely changed by maybe .1 or .2 volts, which leads me to suspect the anode resistors take power off the 12v regulated line. The regulator would probably benefit from a small heat sink with that much overvoltage but other than giving the op amps some extra headroom and running the risk of running an overvoltage in a circuit designed for 15v, I can't see the purpose of this quasi popular "hack."

But I can see why so many people swap the 12ax7 tube out for a 5751 or 12ay7. The lower u factors will result in a more useful gain range for anyone who finds the micro terror gets harsh at high gain+volume. I would bet a dollar to a doughnut at least one op amp hard clips at high gain + volume levels.

9 volts....? Couldn't they buck the 15v up to 30v at least?

I'd like to get this amp to have a lot less gain with out losing volume; all while retaining the great tube feeling I'm getting right now.

Here are some more pics...