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The older Clarus amps are not Class D. If you open one up, you'll see the reason they're so heavy. Mine mostly sits on the shelf, because the Quilter SBUS is so much smaller, lighter, and lively sounding. But the Clarus does amplify with very little coloration, and works well enough as just a power amp. I tend to prefer using it by connecting via the effects loop input rather than the standard input, whether or not I add a preamp pedal.
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06-09-2025 03:20 PM
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I'm pretty sure that they've always had class D output stages, since the original Model 1 was described as being class D. But they're spec'ed to drive loads as low as 2 Ohms, so they must have very robust power supplies, wiring, and cooling. It takes a serious power supply to pump 300W RMS into a 2 Ohm load, even in class D. Class D is primarily a voltage amplifier all the way from preamp through power amp. But a conventional amp (whether tube or SS) uses voltage gain in the preamp stages and current gain at a fixed voltage in the power output stage. This is part of why AI amps were expensive.
Originally Posted by Cunamara
Class D power supplies use pulse width modulation to modulate conditioned and rectified line power. So basically, they turn line AC into pure DC, modulate it back to audio frequency AC with the signal from the guitar so that it's an amplified replica of the input waveform, and pump that amplified signal into the speaker. Line power is 120 volts coming from at least a 15 amp circuit in US households and businesses. So there's plenty of current available to heat up and fry the transistors etc through which it's pushed. It takes robust design, layout, wiring, components, heat dissipation / cooling, and construction for an amp to withstand 300W coursing through its veins whether it's being generated by 3 amps at 100V or 1 amp at 300V. And the lower the load impedance, the harder it is for the amp to maintain a steady supply of electrons with that level of elecrical pressure (which is what volts measure). That's why class D amps that can power 2 Ohm loads have to be built much stronger and heavier than the ones that struggle to keep up with a 4 Ohm load.
Think of speaker impedance as a pipe through which electrical power is flowing into the speaker. The wider the pipe, the lower the resistance to flow. It takes a lot more pressure to push water through a big pipe than a small one. It's Ohm's law again: voltage = current times resistance. Electrical pressure = current flow x the resistance through which it passes. Drop the resistance and you have to increase the current flow to maintain the same pressure or increase the pressure to maintain the same current flow.
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A true update, not a bump. I was supposed to receive a fresh load of 200 mm pipe for Metros this week. Pipe supplier Uponor just told me they have postponed the batch until some time after the summer break. This means I'm unable to supply more than a handful of Metros anytime soon.
If that's the bad news, the good news is that the market appears dead - a new situation and no doubt a reflection of worldwide uncertainty and anxiety. With no order backlog, I can do chores around the country home and spend vacation time with the family without bad conscience.
Midsummer is a big feast in Scandinavia. A joyous one to all who celebrate it!
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AllClarus amps are AI, but not all AI amps are Clarus models. It just occurred to me that there were Acoustic Image amps before the Clarus series. They were rectangular heads about twice the size of the Clarus and much heavier. These were not class D. IIRC, there was an 800, a 1200, and at least one or two others. I think they were marketed as bass heads. Originally Posted by sgosnell
But AFAIK, the Clarus series were D from the first 1. Is your amp a Clarus 1?
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Mine is one of the original Series 1, with a lifetime warranty. I'm not positive, but internally it certainly doesn't look like any Class D amp I've seen. I could be wrong, because I was wrong once before.
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I wouldn’t know how to tell by looking at the power amp; when I had the casing off of my Clarus 2r to clean the pots, I noticed at least that it had toroidal transformers. But maybe you can have those in something other than a class D amp.
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And there you have it - they’re all class D and have always been class D. The heavy toroidal tranny is there to provide the juice needed to push out the high wattage. Remember how class D works. It uses a switching power supply to modulate the DC (ie rectified AC from the power line) coming out of the power supply. There are no big storage capacitors in the PS. All the power delivered to the speakers is coming directly from the outlet into which it’s plugged. Originally Posted by Danny W.
Class D is very efficient - most are over 90%, so there’s very little heat generated because 90+% of the power coming in is going right into the speaker(s). Line power is 120V (in the US) and will pass 15 Amperes over the lowest power household circuits. That’s 1800 Watts, and there’s basically a straight line between the outlet and the speaker terminals. So getting 1000W from a class D amp is a no brainer, as long as the rectifier, power transformer, and wiring can handle it.
The reason little class D amps like the BAM have very little headroom is that they don’t have big power transformers, heavy gauge wiring, etc. They’re designed to put out exactly what they say they put out and to crap out if pushed beyond that. Well designed and built class D amp like the AI can push transient peaks well above their continuous RMS because the transformer and the power supply built around it can deliver high peak power for milliseconds without overheating or otherwise self destructing. Ask them to do it continuously and you can kiss them goodbye and grab your fire extinguisher. But they do have the headroom. None of the sub $500 class Ds can do this, but they’re much smaller, lighter, and cheaper than AI, Quilter Tone Block, etc.
You get what you pay for.
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A lot has happened since the start of this thread in early April. Trump this, Trump that, Trump TACO etc. Two things worth pointing out.
1) USA has allowed a generous $800 duty-free limit for parcels to individuals, known as de minimis. Over 4 million parcels per day, mostly from China and HK. Those two sources were exempted in April. My deliveries to the US have continued without hiccups. The Big Beatiful Bill contains language promising to terminate the de minimis privilege in 2027. I will be 80 then and most likely no longer in business. If someone wants to take over and produce Toobs and Metros in the USA, I'm game. Plenty of time for the transition.
2) Acute shortage of black body material for Metros. Only a dozen Cinnamon-colored Metros can be made until a new batch of black plastic pipe gets produced by my supplier Uponor. That was supposed to happen in late June but didn't. No new production date has been announced. I won't do any major component restocking until the pipe is on hand.
10"-12" Toobs, guitar, bass and FR, available immediately or on short notice.
The first half of the summer in Finland was horrendous, but we now have +30C temperatures for a big change. The lake is warming up by the minute. No particular rush back to the workshop.
Cheers,
Markku
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Some nights don't get below 30C here, and it has been that way since May. Any day below 32C is unusually cool. But at least it's a moist heat. Haven't seen a day below 50% humidity since so long ago I can't even recall it. Good luck with the Toob business, I hope you get very rich with it. I was somewhat skeptical when I saw your initial posts announcing the line, but I've since been sold.
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Sorry to be back. The past couple of days have brought some bad news, especially to my American followers. Their great leader has changed his mind again, and the $800 de minimis "loophole" will be abolished at the end of August, instead of two years from now. I think this is a major setback for American consumers, and another challenge for the administrators who were letting through millions of parcels per day before China and Hong Kong were excluded.
The EU tariff is set at 15%, exactly the discount I offer to Forum members. The offer still applies. My lean margins don't allow for a further price reduction. A grassroots proof that American consumers will pay the tariff, not the EU or any other trading partner.
My second chagrin is the workshop building. It's slated for demolition, but a deep construction industry slump has postponed decision-making. There's some fresh info to digest. Whether I'll have to leave on a month's notice or some time in the not so distant future, is nevertheless open.
Finally, I'm totally out of black Metro shells until further notice. Up to a dozen of Cinnamon-colored Metros can be produced in a hurry to meet the August 31 de minimis deadline, but there's no time to waste. Hardly any time for Tolex or Tweed wrapped Customs either.
10"-12" Toobs, both guitar and bass, available immediately or on very short notice.
USA is my main market. If I lose it because of Trump, that might be the end of the TOOB saga.
Regards (not cheers),
Markku
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I'm sorry to hear of your troubles. The insanity continues apace here. It's possible there is only one person on the planet Earth who doesn't know who pays tariffs, but that person's backers are terrified to argue with him. And tariffs are among the least of our problems.
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Before declaring “insanity” and dismiss the views of the backers who are “terrified to argue with him”, I’d wait and see how it goes. It’s a complex topic with plenty of arguments on both sides. For example, the higher tariffs are still not linked to increased inflation in the US, contrary to virtually all the critics’ predictions. Originally Posted by sgosnell
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Inflation is igniting again, while the economy slows and jobs disappear (see today's report and revisions to the last 2 months), but sure go on pretending that we don't know with absolute certainty that tariffs are making things more expensive even as growth slows.... HELLO STAGLFLATION! But there will always be some cultist who watches Newsmax all day and cannot see (or deal with) reality.
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It’s alright they fired the guy who said it was bad so everything is good now. Originally Posted by DjangoWinebar
Sent from my iPhone using Tapatalk
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Yep, problem solved. Kill the bearer of bad news.
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Increasingly sorry to hear that the tariff lunacy has put friends in a tight spot. Hope you can hang on, Markku.
But hey! At least Lesotho didn't get away with taking advantage of the U.S.A.
And also, at least all the other countries are now increasing their dependency on China. What could go wrong?
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An update on my use of my TOOB Metro BG+ and DV Mark EG250. it has become my most commonly used setup, my poor old 5E3 sitting neglected next to my armchair. I've used it with duos, trios and quintets in very small to medium-ish rooms. But yesterday I played an outdoor gig with it with no other sound enforcement for the guitar and was very pleased. I could be heard clearly up to 50 yards/45 meters away and did not have the volume knob above noon on the amp. The acoustics were surprisingly good for outdoors, but still I was very pleased with the results.
I also used a wireless setup and liked that I could put the amp towards the back of the stage so the drummer could also hear and that I had a better sense of what the audience was hearing compared to having it 4 feet away from me. I really like wireless.
After the gig one of the audience members- not a guitarist but I don't recall what his instrument was- came up to talk to me about my guitar and told me that he thought I sounded like Kenny Burrell. I don't know why he would think that, I wouldn't be qualified to tote KB's gig bag from the taxi up to the stage, but I appreciated the compliment nonetheless. It's cool if anybody thinks you play well.
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Thanks, Cunamara, for inviting a further update! I'm happy to report that sales to the US have resumed. Our 1,000th cab will see daylight during the summer. (I thought I'd be well off on reaching that milestone. Little did I know...) Anyway, crazy enough to have just ordered 70 SICA speakers for Metros, both BG and FR II. This despite the fact that, over the past couple of months, Metros have seen a slowdown while the demand for 10"-12" guitar and bass TOOBs has resurrected. I can now say "our" and "we" with good conscience, as my son Tuomas, pro bassist Jukka Nuuttila and electronics wizard Dr. Jussi Säily are now very much part of the team. In the works: active (200W) version of the 12F full-range cab, and an omnidirectional multi-speaker sound system for a noted US guitarist. You'll hear more if it works out.
Last edited by Gitterbug; 05-30-2026 at 05:03 PM.
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