Cheap amp without load dependency.

[badspeakerdesigner]

Ive toyed with vcad in an attempt to flatten the impedance but living up to my name, passive filters are a mystery to me. lacking impedance measurement rig doesn't help.

 

[Mnyb]

What's load dependancy issuse?

Class D amps needs an output filter to remove the carrier frequency from the switching, this output filter has a rising impedance with frequency thus treble response can vary depending on speakers .

Better class D amps has the filter inside the feedback loop and this solves the problem.

But on a tight budget a used old AB amp in good condition is also a possibility.

 

[jhaider]

I was wondering if anyone knew of any Class D that don't exhibit the issue and are under say $200.

Look for something with Hypex UcD (there was a Niles model tested here; ProJect Amp Box SE/DS are also UcD180), Icepower ASX2 (but make sure it’s properly buffered!), or Anaview (Parasound Zonemaster 250/450).

That said, at relatively low power I’m not sure D saves much over a small AB amp (e.g. Parasound Zamp) and the latter can be found at great prices.

 

[Sokel]

Third vote for a nice used AB one,like yamaha,etc.

 

[DanielT]

Choose a current strong amp. For example, a HK 670 or 675 can be had for around $70-160. BUT 670/675, amplifiers around twenty years old, almost vintage nowadays. Anything can, of course, if you're unlucky, happen to them. Probably not, but you never know. BUT if they work as they should, they are good amplifiers. Affordable used amplifier models.

Harman Kardon HK675 Stereo Integrated Amplifier Manual | HiFi Engine

www.hifiengine.com

Edit:
Basically a new thread, what to consider when buying X year old amp.

 

[Joe Smith]

Below is the impedance curve of OP's speakers (C-Note). The impedance magnitude of his speaker is 15 - 36 ohms from ~6 to 17 kHz, which is much higher than the 8 ohm dummy load Amir used. This will raise the response at the higher frequencies more than what is shown in the 8 ohm graph.

Interesting - so just to see if I understand this - for instance, the ELAC Debut 6.2 speakers have their high impedance mark about 2kHz and have a minimum impedance of 5 ohms. So should they fare better or worse in terms of frequency curve normalcy with an Aiyima A07 amp? Better because they would present the highest demand in the mid-range band and NOT in higher frequencies?

 

[pjug]

Maybe the Emotiva A2M, if $279 is not over budget.

BasX A2m Stereo Flex Amplifier

The BasX A2m is a flexible stereo amplifier that combines excellent audio performance with several unique and extremely useful features for both big and small systems.

emotiva.com

Or if a basic power amp works for you the Niles one is cheap used and reviews here pretty well

Niles SI-275 Amplifier Review

This is a review and detailed measurements of the Niles SI-275 stereo power amplifier. It is on kind loan from a member. The SI-275 is discontinued. But since it is sold to the custom integration channel, they come up used and in working orders (companies pull out gear wholesale to redo...

www.audiosciencereview.com

 

[NTK]

Interesting - so just to see if I understand this - for instance, the ELAC Debut 6.2 speakers have their high impedance mark about 2kHz and have a minimum impedance of 5 ohms. So should they fare better or worse in terms of frequency curve normalcy with an Aiyima A07 amp? Better because they would present the highest demand in the mid-range band and NOT in higher frequencies?

Here is the simplest model of the amplifier output filter (figure from source.) It is a LC low pass filter with a nominal cutoff frequency of 1/sqrt(L*C) in rad/s.

As an example I use L = 20 μH and C = 0.5 μF, which gives a cutoff frequency of 316 228 rad/s = 50.3 kHz. These are the frequency response plots with 2, 4, 8, 16, 32 Ω speaker impedance. You can see that the speaker load impedance, if it is purely resistive, affects only the Q of the filter. The higher the impedance, the higher the Q. Therefore, a resistive speaker impedance only affects the top end of the frequency range, and has negligible effects at < 5 kHz.

However, the speaker impedance can be inductive or capacitive in addition to being resistive. Below are plots again with 2, 4, 8, 16, 32 Ω but with an additional -45° and +45° phase angles. You can see that the speaker impedance phase can also have significant effects on the resulting frequency response.

 

[JSmith]

Class D amps needs an output filter to remove the carrier frequency from the switching

https://www.ti.com/lit/an/sloa145/sloa145.pdf

JSmith

 

[Mnyb]

https://www.ti.com/lit/an/sloa145/sloa145.pdf

JSmith

Are these TI chip always implemented filter free ? Most applications ? The carrier frequency is still there with the TI solution but reduced depending on load ? Interesting wonder if they developed this to reduce load dependency or cost of building the amp thanks for the information.

 

[pjug]

Ive toyed with vcad in an attempt to flatten the impedance but living up to my name, passive filters are a mystery to me. lacking impedance measurement rig doesn't help.

Did you try the simple shunt network like the one shown in post #217 in your other thread? I tried this with a similar amp/speaker with the issue and it works. I just don't know if it is a good idea or worth the trouble compared to freeing yourself of this by using Class AB with your speaker.

Parts Express DIY C-Note Speaker Review

What amplifier you're feeding them with? It doesn't look like HF shelf/mistuned tweeter level - that curve shape tells me that some EQ or rather tone control (treble boost) is applied. Check amp and source:)

audiosciencereview.com

 

[badspeakerdesigner]

Did you try the simple shunt network like the one shown in post #217 in your other thread? I tried this with a similar amp/speaker with the issue and it works. I just don't know if it is a good idea or worth the trouble compared to freeing yourself of this by using Class AB with your speaker.

Parts Express DIY C-Note Speaker Review

What amplifier you're feeding them with? It doesn't look like HF shelf/mistuned tweeter level - that curve shape tells me that some EQ or rather tone control (treble boost) is applied. Check amp and source:)

audiosciencereview.com

I haven't, I might have the parts to try this but I'm also just really burnt out on this problem in general. Taking the speakers apart if getting a little tiring.

 

[pjug]

I haven't, I might have the parts to try this but I'm also just really burnt out on this problem in general. Taking the speakers apart if getting a little tiring.

You dont have to take the speakers apart. The shunt is between speaker or amplifier tetminals, so external.

 

[badspeakerdesigner]

You dont have to take the speakers apart. The shunt is between speaker or amplifier tetminals, so external.

Ah gotcha. Would it just be the cap and resistor?

 

[pjug]

Ah gotcha. Would it just be the cap and resistor?

Yes. For my amp and speakers 10uF and 8 ohms worked. Vcad seemed to show 10uF and 6 ohms might work for you. Although I am just guessing about the amp's output filter so you might have to do some trial and error.

 

[TonyJZX]

yeah i cant imagine any CHEAP digital amp is going to satisfy the OPs lust for Krell like drive ability (!!!)

i dont know how it is in the US and EU but over here we have a few retailers who maintain nos type units that just dont shift

something like this or its little brother is still available

Harman Kardon HK 3770 2-Channel Stereo Receiver with Network Connectivity and Bluetooth • Symphony Hifi

Harman Kardon HK 3770 2-Channel Stereo Receiver with Network Connectivity and Bluetooth, Harman Kardon’s reputation for excellence.

symphonyhifi.com

how well does the typical yamaha 501/701/801 fare?

but again you may not like 19" conventional a/b units

 

[staticV3]

3e Audio has an inexpensive Amp board with post filter feedback, which should reduce load dependency: https://www.aliexpress.com/item/1005004784269635.html

 

[badspeakerdesigner]

I guess I don't have the parts to try the circuit mentioned above. I don't feel like ordering them or taking a trip to PE.

Not much luck with my local used market. The audiosource amp100vs is a no go as the reported failure rate is just way too high. There's a crown xli800 nearby but that seems to not do so well in sinad, although the perhaps I'm reading things wrong but it looks better than the A07? Unsure of this amps load dependency. Big box stores have the Yamaha RS202BL available. Heck at this point I'm wondering if it'd be better to grab a wondom board and turn my cnotes into active speakers.

 

[badspeakerdesigner]

Hey good news, I went and grabbed that crown XLI800 for sale locally. It was in immaculate condition, apparently used for only a few hours. I was concerned about noise/hiss but I hear none at my listening position. The fans are nearly dead silent thankfully.

But here's the final result, no load dependency issues! Look at that lovely normal top end. I'm so relieved that my problems are over. Time to enjoy the speakers.

 

[dlaloum]

My suggestions...

• A Used Crown XLS1500 / 2000 / 2500 - I picked up a 2500 for US$250 some years back - they are plentiful in North America, and often to be found at heavily discounted prices... (esp used) - these are Class D (the current models are 2nd Generation... XLS 1502/2002/2502... but you are more likely to find a bargain among the older 1st generation ones)
• A robust Class AB amp - I still keep my Quad 606 & 707 as my backup amps.... released in the 1980's, they still give current amps a serious run for their money... not likely to be as cheap as the Crowns (although you never know), and at their age, if not refurbished in the last 10 to 15 years, they may need some work. - Plenty of options in this category from different brands/manufacturers... Adcom, NAD, Rotel - as well as the chinese newcomers -