Class D amplifier with TPA 3250 board

News update: I got the amplifier back. It still has a hiss. But it disappears when music plays. It's still a little bit louder than I'd like and you can still hear that hiss on very quiet tracks. It's way more manageable now.

I'll buy an A/B amplifier some day. Nothing too fancy. Or a good class D if the price is right. 

I have Bluesound Node + Ogy speakers + hissy tube amplifier 

News update: I brought the amplifier back to the artisan.I told him about the annoying hum.

He told me that he thought I would never notice. He told me that the issue is due to the AC current feeding the circuit. He said that he could make the amp quiet by using diodes to turn the AC current into DC. That should eliminate the 100 Hz hum.

I’m like whatever dude! I also said that I’m not driving back to his house (60km south of Paris) again. It’s so far away and the traffic jams are killing me. He said that he will show up to my house next Sunday.

And I’m like "k fine".

In summary, yeah. I would gladly spend 500€ or 1000€ on a good class A/B amplifier afterwards. Something without surprises. But the situation is hairy. This guy doesn't want to back down. He's insistent on his abilities which I don't care for anymore. Looking closely at the innards of the amplifier, his soldering is sloppy. Some tin was floating around in the casing. And I was driving as gently as possible with the anxiety that vibrations and bumps would desoldure components.

The artisan has a well equipped workshop and a great listening room. He has everything to succeed. That's why I stuck around for so long. I doubt that I'll ever get my money back. I don't want to deal with him anymore. The anxiety and amount of hours spent on driving is a burden on my life. But he'll be back next Sunday. 

Presently, the amplifier displays an audible "100 Hz hum". There was hiss prior to that, it is now resolved. 

Yeah the situation sucks but I'm in good health and my financials have never been better. I can afford to lose some cash (just not every month during the year like that). Heck! If only we lived in a world where we could mass produce good amplifiers for a few hundred bucks LOL 

The amplifier was tested at the artisan's shop with an old CD player and older speakers for testing. It was still hissing but less. I previously had a Yamaha RN402 with the OGY and no problems. The RN402 is run of the mill class A/B from Yamaha. 

How do you know if an amplifier has a low damping factor? 

@rolox This is music to my ears! Where do you buy these amplifiers? I live in France. 

You're talking about cars? Ha! no. Unfortunately I drive a company car for work. It's a Renault Kangoo diesel 85hp. It gets me all around Paris. And I don't pay for fuel (which costs 2.20€/litre BTW). 

Sure, but if you have a subwoofer already it might compensate right?

Thanks. I'll retrieve the tube amplifier this weekend. I'm praying that it won't hiss. If all goes well I'll stay put. No need to spend more money on audio haha. 

I'm still curious about other people's opinions on cheap class D amps compared to costlier class D amps (NAD, Hypex...), class A/B and tubes. Is the difference noticeable on efficient bookshelf speakers?

The OGY are 8 Ohm 15W. 

I heard the Unison Research Simply Italy in a shop and it was perfect. I was blown away.  I wanted to save money by having the artisan build a clone. Now I feel like an idiot. Another shop recommends Fez Audio but I didn't have a chance to go there and audition. I'm trying to prioritize Euro brands over Chinese.  

The amp was clearly defective at the analog inputs. They were all noisy. So when I plugged the speakers in, the noise gradually built up over 10 seconds and reached about 40db. It didn't matter which input was selected or if music was playing.

Today the amp is (supposedly) fixed. I have to drive over to the artisan and retrieve it. 

Thanks for the kind replies. It's funny how you guessed ASR instantly. Yeah I'm not too stubborn on getting a class D amplifier or tubes. I just drank the cool aid wanting to believe that a 60€ amplifier with a TPA 3255 would satisfy my needs. I like Atoll because they're easy to find on the used market around 500€. I am more familiar with class A/B and know it's just fine. Class D is more expensive for some reason, unless you go for the really cheap TPA boards. 

Yeah I just think that the amp isn’t built very well and that it’s crazy noisy. It doesn’t seem to bother the artisan. I essentially flushed 1800€ down the toilet. The tubes are JJ and new. I don’t want to go down a rabbit hole of spending more money to fix a lemon. I’ll return the unit tomorrow. I don’t expect a refund. I just don’t want to create more landfill.

Two amps caught my attention:

- Yamaha A 670 (brand new) 330€. It’s a 20W class D amplifier with PWM tech. It should sound very clean/neutral.

- Atoll IN30 (used, like new) 250€. Your typical A/B amplifier. Plenty of power. Shouldn’t have much noise because A/B.

My dad told me to get a power conditioner etc... But that’s just throwing more money at the problem and I don’t have much confidence in the craftsmanship. I also forgot to mention that I have a REL T5X never unboxed. So bass shouldn't be an issue.

I understand what you're saying. You went to a reputable company, not some guy. Some guy convinced me that he could build a wonderful amplifier for me and that I could see him anytime if I have issues. In essence I paid for the same things you paid for. But the difference between you and I is the reputation and quality. 

In hindsight, I was lured by the prospect of finally experiencing tubes. My experience couldn't be worse and it's hilarious. I notice that my OGY speakers have more bass and fuller midrange with tubes compared to the Yamaha RN402 I regrettably sold. From memory, the differences are subtle but still there. It's like 20% better with tubes (listening to busy tracks where the hum disappears), and that's a huge improvement in audiophile terms. But the quality of the recording and my mood play a bigger part (IMHO).

Perhaps if I use the powered sub, the quality of the amplifier should matter less.

I researched low damping factor amplifiers briefly. It looks like today's transistor amplifiers are built for high damping factor by default. Low damping factor amplifiers are most commonly tubes. A high damping factor doesn't allow a woofer cone to vibrate much. So you get harder upper midrange and less bass with fullrange drivers. That's all theoretical and I'm probably out to lunch on the understanding. 

@dekay You’ll laugh but the artisan’s workshop had a bunch of noisy neon lights. The artisan told me that he couldn’t hear them anymore.

Thanks for the advice. Musical Fidelity sells the V90 amp new for 350€. The reviews seem kinda mixed. Everyone treats it like a cheap amp. Someone even says that it has a noise floor. 

There's no mention of low damping. I guess I'll give it a pass. I have to wait until Sunday anyways.

Alright, so I do not have the amplifier with me.

The amplifier always made that hum, even on the shorted inputs. I only use 1 out of 4 inputs so it's quick to find out. The hiss is gone. 

But the amplifier is currently in repair. The artisan told me that he was gonna add diodes to convert the AC current into DC and that should kill the hum. He told me the hum was 100 Hz. 

From memory, the hum was just annoying enough to ruin quieter songs and unnoticeable on busy songs. But I love Billie Eilish and her tracks are equal parts quiet and loud, so you notice the hum. So I really hope it's the AC current killing the vibe with the hum. 

Anyways I can't do anything until Sunday. 

@rolox My curiosity peaked and I bought the Sure amplifier with the Tripath TA2024 chip. Some reviewer online compared the Sure amplifier with the Amptastic and the Trends and stated that the differences were pretty negligible. Since the Sure is 60€ (total 80,8€ with power supply and shipping) on sound imports VS 280€ for the Trends, the choice was easy. 

I am more worried about the noise floor at this point. And 80€ is the price of drinking/dining/clubbing for night in Paris anyways. 

My OGY speakers are very efficient at 91db SPL. I only need a few watts. The manufacturer rates the OGY at 15W 8ohm max. If I get 4W out of the amp it should be enough to annoy the neighbors. 

My #1 priority is noise floor, since my speakers are quite sensitive. But even my Yamaha RN402 had a small tiny noise floor which was only noticeable when you stood very closely to the tweeter. So I'm not very fussy I suppose. My tube amplifier was just that bad. 

My other big concern is that people seem too kind with these chip amplifiers online. The rock bottom price plays a huge part in that. I say this because there's no shortage of branded A/B amplifiers on the used market between 80€ and 400€. If this T amplifier can't compete with 150€  used Yamaha A/B amplifier then it's not worth my time. 

So I'm crossing my fingers. I'll keep you updated on Sunday. 

@atmasphere 50W is a lot! My terrible tube amp doesn’t even go to 20W and I have the volume set to minimum.

My room is about 24m^2, maybe less. My speakers are rated at 15W max. I am also listening from a distance of 1~3m.

Yeah the artisan sucks. Tell me something new. I’m gonna be using my Sure amplifier for the time being (when it arrives home). You know the cheap T amp.

At this point my expectations have been lowered so far down that any amplifier which doesn’t exhibit a loud noise floor will sound like angels singing from the sky.

Hey, if it sounds loud to me I ain't bothered! 

Speaker specs are intentionally confusing anyways. The OGY are so easy to drive because they're just 4" paper drivers with a 1/4 transmission line inside a 30x30x15 cm box. 

@rolox So I came back from an 8h train ride and finally had a chance to try the Sure amplifier. I hooked it up to the Node in a jiffy and listened to a bunch of tracks with Deezer/BluOS (subwoofer still in box). Yo be fair, I was in a cranky mood and I was also in the mood for finding flaws. 

First impressions: ??? I was impressed at first then I ended on a meh.

So there is a noise floor but you have to stand like 30cm from the drivers to hear it. So it gets a pass. 

I can't figure the volume knob, it spins freely over 360° and doesn't seem to go very loud. But volume is sufficient for my appartment use. I'll just play music moderately loud. Fine. 

Bass just doesn't slap like on the tube amplifier. It's kinda there but not really, like the orange flavor in Fanta. 

Midrange and Treble are remarkably clear. And that's a bit terrifying in a good way. I heard stuff on the Sure that I didn't hear on the tube amplifier. 

Buuuut I have to get used to the Sure's kind of dry presentation. It's CLEAR, almost to a fault. But you just don't feel much of the instrument decay/reverberation in the recording. Fleet Foxes Sunblind sounded like (really good) elevator music, because the Sure lacked some punch. 

I think I can get used to the Sure, and then the tube amplifier will sound woolly in comparison. I'm hoping the subwoofer will help. I could use more bass. Maybe the dinky power supply I ordered really doesn't help. It's 3A 12V 36W "laptop brick". 

I'm probably the only idiot pairing a set of $2k speakers with a 40€ amp. And the results are just fine. 

News update: The tube amplifier is still under repair. The artisan is struggling to fix the problem. 

I added the REL T5X subwoofer just now. And it FIXED everything! Now I have an excellent setup, even at low volumes. I am very happy right now! Yay! 

Now that I think about, the Sure T amplifier is the cheapest component in my setup. Even the cables cost more. To summarize:

Speakers: Closer Acoustics Ogy

Subwoofer: REL T5x

DAC/Streamer: Bluesound Node (2021)

Amplifier: Sure AA-AS32157

Cables: Adeqwat brand (from Boulanger). 

I'm done! Finally.

@atmasphere Looking at those specs the TA2024 looks like junk haha. Who on Earth wants just 10W at 10% distortion LOL?

@dekay It looks like I have been pissing off the neighbors this past week. I'm still rocking that puny little Sure amp. It's really cheap junk amp. The volume knob spins around freely and the volume adjustment doesn't seem to do much. But I couldn't care less because it sounds so good! And the Bluesound Node has basic volume adjustment from the phone. 

Oh yeah, the tube amplifier is still at the workshop. The poor artisan is struggling to tame down the noise floor. I kinda forgot about him. I'm having too much fun. 

I never thought that my audio journey would end with a 40€ amp the size of a matchbox... Everything about it screams "cheap junk". It's like the Toyota Echo of amplifiers. 

@rolox Thanks. I have to stress that the class D cheapie doesn't impress without a sub! This amp is all about the mids and highs. It's hard for me to recommend the Sure amp in absolute terms. You get 0 versatility. No bass. Only 10W of power. And the volume knob sucks. The Bluesound Node makes this thing usable. 

The Sure amp just happens to sound great with the OGY. I think I lucked out. 

@rolox The Amptastic vanished from existence. This amp was my first choice, the price was very reasonable at around 100€. And the design was perfect.

The Trends was 200€ and with the same on paper specs as the Sure. I read a review somewhere comparing the Trends with the Sure and the conclusion was that differences were negligible.

Granted, the Sure amp is a bit of a false bargain because the price hikes to 80€ with external power supply + shipping.

On a side note I’m shocked how much the REL T5x improves the sound. It makes me wonder how the far cheaper but still delightful Q Acoustics 2020 sounds like with the REL.

Do I really need such bespoke speakers (OGY) if I have a REL?

Answering that question would require spending more money and time. So I won't bother to find out.