Advice for amp board with 4ohm max 150W 88dB speakers

[atamgp]

Hi All.

I need some advice for the best stereo amp board around $100 budget (excl PSU) for my situation, can be A/B or D.
For me it is important that I reach max potential of my speakers in a 7m x 7m room.
I will connect my high-grade stage piano and mic's for vocal and a digital guitar thru an external sound module. Sound quality is more important then max watts.

sound module: focusrite scarlett 18i8
inputs: 20 Hz - 20 kHz +0.5/-1.5 dB, 109 dB (A-Weighted) , THD+N <0.002%
outputs: 20 Hz - 20 kHz ±0.5 dB, 108 dB (A-Weighted), THD+N
<0.001% , Maximum Output Level (0 dBFS) +16 dBu, 94 Ω (Balanced)
I will be connecting the TSR outputs to the amp.

speakers: 2 x audioengine HDP6 passive
2-way passive, rear ported design
88dB (2.83v@1m)
50Hz-22kHz ±1.5dB
4 Ohms
CROSSOVER FREQUENCY : 2.8 kHz
10-150W per channel
5.5″ Kevlar woofers
1″ silk dome tweeters

aluminum amplifier chassis with cooling fins I already bought is here.
Internal dimensions: width= 161mm , Height= 84mm , Depth = 246mm

ALPS27 50k potentiometer soldered I already bought.

Power supply:
I like the idea of using 1 toroidal transformer (even If i go monoblock). Can get my hands on a good priced, good quality 2x 25V 225VA which should be more then enough (will give around 35V DC rails )
I would use this in combination with a IEC Emi/rfi Filter 250V (Europe) 1 or 3 Amps.
SMPS is also a possibility only if needed and would be a beter option than the toroidal.

So am I a bit technical and handy (Computer Science) but have no clue what the best amps are in end 2018 and prefer not to solder
I had a couple of lm3886 servo boards in mind which seem good quality. Is max 78W@4ohm too low for my speakers potential?

LM3886 boards:
1.Shareconn LM3886

2.Kaisaya LM3886

3.DC-servo-circuit-LM317-LM337-C1237-LM3886-JRC5534DD-OP07

4.DC servo version LM3886 power amplifier board kit /finished board 68W+68W

5. 120W+120W LM3886 dual parallel multicenter amplifier board ref Jeff Rowland
No opamp? no servo, but dual lm3886 per channel

6. LM3886 2 x Mono + Big *** Rectifier
Cons: missing some stuff the intgrated options above have like opamp, servo...
Pros: 4 nice big NOVER caps
https://www.aliexpress.com/item/Fre...d-Board-with-ERO-capacitance/32857150165.html
https://www.aliexpress.com/item/New...und-quality-high-quality-DIY/32859955860.html
https://www.aliexpress.com/item/Aiy...er-Filter-Power-Supply-Board/32831781359.html

Other non-LM3886 options are:
ICE125ASX2 (most expensive option)

TA2022
Seems interessting if 4 ohms is supported, unclear, but 2 interesting boards:
https://www.parts-express.com/yuan-jing-ta2022-2-x-180w-audio-power-amplifier-board--320-6512
https://www.audiophonics.fr/en/ampl...e-amplificateur-tripath-2x90watts-p-4604.html

TA3020
Better then TA2022?
Can find comparable boards, this onse seems modest
https://www.ebay.com/itm/TA3020-Aud...onics-tripath-T-amp-ship-from-US/132601087850

Monoblock with 2x irs2092-iraudamp7d + Power Supply board for Amplifier 6x10000µF 80V
Unclear if 4 ohms is supported and suggested...
https://www.audiophonics.fr/en/ampl...damp7d-amplificateur-class-2x250w-p-7037.html
https://www.audiophonics.fr/en/non-...board-for-amplifier-6x10000f-80v-p-10216.html

IRS2092 2 X 125 Watt
https://www.ebay.com/itm/2-X-125-Wa...-Board-IRS2092-WONDOM-Stereo-Amp/110932804216
sure-electronics also has this. Seems to be for 8 ohms...
2 x 200W Seems to support 4 ohms
https://www.yuan-jing.com/irs2092-class-d-stereo-amplifier-board-200w-200w

sure-electronics board t-amp based 100W@4ohm 30V DC THD+N 1%
http://store3.sure-electronics.com/2-x-100-watt-class-d-audio-amplifier-board-t-amp

TDA7294
Als AB based like LM3886, is it beter?
"TDA7294 with inverting in and separate supplies: TDA sounds softer, the base is soft, the mids and highs are more natural... in terms of sounding it sounds more detail, it has less "sand" in high freq range."
"I cycled the power on/off 3 times in 5 seconds. The TDA7294 was blown instantly "
source
Mono based
here and here
2x85W
2*150W Dual chip per channel

sure-electronics TDA7498E 2 x 160W
better then TDA7294 and LM3886?
Wonder how the dual TDA7294 (yuan-jing) compares to the TDA7498E 160W.....
111W@4Ohm 36V DC THD+N 1%
clone here?

TDA8950

TAS5613
WONDOM 2 X 150W

Hifimediy TK2050 amplifiers
I think lm3886 is better...

TPA3255?
Seems to be beter then tp3116 but limited to 8 ohms? Also not sure how it compares to lm3886...

NJW0302 and NJW0281 based options?
I don't even know what these are, but the mono boards are small and can connect a toroidal to them, done.
Are also marketed as A3, A4, A5...
Has anyone compared / tried these?
https://www.aliexpress.com/item/AM-...-class-AB-ON-NJW0302-NJW0281/32797498389.html
https://www.aliexpress.com/item/201...air-tube-NJW0302-and-NJW0281/32898875557.html
https://www.aliexpress.com/item/201...air-tube-NJW0302-and-NJW0281/32898875557.html
https://www.aliexpress.com/item/A5-...ifier-DIY-kit-finished-board/32861089836.html


Sooooo many choices. So a lot of you guys have played with multiple of these. I have not.
I wonder what end 2018 the best boards are around given budget. Personal to my situatio is the 4 ohms speakers I think. Most
people tend to use 8 ohms.

Who can please shed some wisdom, greatly appreciated!

 

[sgrossklass]

Amplifier board choice might not even be your biggest problem. The whole system design has issues.

That's not a very big case there. I might still trust that with something like a 2x 25 W (FTC) AB amp if the finals are spread across both sides, but that would require squeezing two boards and the toroidal + PSU components in there. A Class D option would go easier on thermals at least, in fact they often come in cases like these, but may not be all that great in sound quality. (The Sure TDA7498 boards employ some rather nonlinear ceramic caps in the output filter, for example, which worsens high-frequency distortion by about an order of magnitude if memory serves.)

You already have an interface with a balanced output. Why do you intend to go with unbalanced connections then, especially since the amp seems to be shaping up as an IEC Class I device (really no way around it with a SMPS, in a linear supply you'd need a transformer with a shield winding to be able to go Class II)? This is spelling trouble from the get-go. (Unbalanced --> go Class II a.k.a. double insulated. Balanced --> go Class I a.k.a. mains earthed. Unbalanced + Class I is a recipe for guaranteed ground loop trouble.) Using an external balanced line receiver gets pretty messy.

I would definitely want to integrate balanced inputs if possible. You probably didn't plan on hacking up the case though, I guess? One would want to integrate some XLR input jacks, with pin 1 wired up straight to chassis as per AES48-2005. Some 1/4" TRS jacks may fit more easily and can be used just the same though, the handling just isn't as nice. (I would try it if you have some floating about, maybe they'll even fit in the RCA connectors' holes as-is, or minimum drilling action gets things sorted.)
Not sure what's available in terms of line receivers boards either. It wouldn't have to be anything outlandish, a one-opamp job with a decently low-noise chip would be quite adequate (maybe a tad better than a TL07x), though something better won't hurt. You'd want an input gain of about -12 dB for a good level match (e.g. 22k / 4k7 x2). After all, your power amp is likely to require about 1.5 Vrms (+6 dBu) or less at clipping level. There are some balanced receiver ICs that can't do negative gain, so beware and check the datasheet.
Oh yeah, and obviously the whole shebang also needs power, with +/-35ish V not being an option. You could regulate those down (should be able to find some boards with an 78M15/79M15 combo or an LM317/337 combo with ADJ pin capacitor fitted, best use extra dropper resistors), feeding the regs using a small aux transformer (3 VA, 2x 15V~) would be more efficient though.

After all of that is out of the way, only then there's the question of what amplifier board to choose. I wouldn't trust Class D chipamps that much with 4 ohm loads, on the other hand neither TDA7294 nor LM3886 datasheet suggest supplies higher than +/-27-29 V for 4 ohm operation due to current / dissipation limits. 100-ish W into 4 ohms just isn't traditional chipamp terrain, I'm afraid.
(At least lowish supplies would mean that you shouldn't have much trouble finding some nice Schottky rectifier diodes.)

 

[atamgp]

Hi sgrossklas, firstly thanks a lot for your input. Its greatly appreciated.

Man, you have brought up a lot of points I did not think of. I clearly don't know a lot and try to use the knowledge on this forum to build with existing components a great amp for my situation.

I was hoping not to hack in the case. The amp case will be on my studio desk that's why I was limited by size. If I look at lm3886 amps ready made they usually have a smaller case, so I though I was safe here...

Let go through your points:
- IEC Class
What is the class of the lm3886 amps boards and amps being sold? They all are unbalanced.... Are usualy based on a toroidal + the amp board only, don't see any double insulation. If easily realized I want to try the balanced/Class 1 suggestion.

- Balanced/Unbalanced
Ok, good point. The main use case is using audio interfaces which usually have balanced outputs. So I need a balanced input solution, I agree.

- From your statements I read that you tend to advice AB above D. Especially for my 4 ohms speakers. Am I right? If so, which AB would you advice in a balanced solution?
Also, do you think the power output @ 4 ohms of lm3886 is more then enough for my speakers? I see the in some boards the double the chips per channel (parallel) but usually the supplier is not clear on 4 ohms support in that case... From the text below it looks that parallel lm3886 is best when using 4 ohms But I would only go that route if lm3886 can be used for balanced config and if the normal power of lm3886 (or other ab class) is not enough for my speakers....

"Parallel allows lower impedance"
"With parallel 4ohm, you will get about 3dB, so it can be good, but to 8ohm it is really questionable."
source

- Class D
There are some class D amps where it is stated to work good with 4 ohms.... :
ta2022 : "90W 4 Ohm (@ THD+N
0.1%)" This one even has a switch for choosing balanced inputs!!!!! What do you think?

T2-Jantzen : "This amp can drive any speaker from 4-8 ohm. It is recommended for speakers in the 4 ohm range. For 8 ohm speakers, we recommend the T1 amp. 2*100W@4ohm"

If going the TDA7294 or LM3886 route it indeed seems that for 4 ohms i would need lower voltage toroidal e.g. 20-0-20 here.

So to sum up I need a balanced input solution. I could only find 1 class D ta2022 based amp board which supports balanced inputs directly.
You suggested a opamp receiverboard to convert balanced to unbalanced in order to use any mentioned unbalanced amp board?
It it normal to do that or do balanced amp processing boards not exist?
If I can find a fitting receiver board for the conversion next question becomes class D vs AB en if AB parallel or normal stereo based....

 

[atamgp]

Small update:

- I am not going to do mono. Will use reusable components: toroidal, Balanced-conversion board, stereo-amp board. With this setup I can always upgrade the am board to a newer/beter one and keep the rest. I tend to go for lm3886, 2xlm3886 or LM4780 as those boards just seem more advanced then available class d boards.
2xlm3886 or LM4780 seems might be beter for 4ohm loads.... source and here
Still not sure about that. dual config (parallel, not bridging/BTL) would make the chips see my 4 ohms speakers as 8 ohms..
If I go dual, I need the 25v toroidal I think at 300va.

- Balanced conversion is solved, found a board doing just that:
Balanced to Unbalanced XLR to RCA Stereo Preamplifier Board ultra low distortion | eBay
or
SSM2141 Balanced input and unbalanced output Dual Channel Preamplifier Board 4857664135595 | eBay
Hoping that the gain is enough for the LM chip, see discussion here
Another possibility is using a transformer, 1:1 or something....
The above board does need to be powered ± 5V ~ ± 15V, so need a solution for that as the toroidal below is going to be connected to the amp board directly.
This is 78mm on 1 side and can be fixed at any side of the case which is 80mm in height
Will drill existing rca holes to fit XLR inputs which will be connected directly to this board.
I can also upgrade the 4xNE5532 opamps when/if needed.

usefull information on balanced signals:
https://www.eeweb.com/extreme-circuits/balanced-unbalanced-converter-for-audio-work
https://www.bhphotovideo.com/explor...humored-attempt-demystifying-10-dbv-and-4-dbu
http://www.jensen-transformers.com/schematics/
http://www.jensen-transformers.com/wp-content/uploads/2014/08/as089.pdf
http://www.jensen-transformers.com/wp-content/uploads/2014/08/an003.pdf

- Power using toroidal 225va 18-0-18
https://www.ringkerntrafo.nl/shop/ringkerntrafo/225va/182/2x-18v-ringkerntransformator-225va.html
I might go with a 20v version one can be found for a good price.

 

[atamgp]

To power the Balanced -> unbalanced boards with +-12v i found these options:

- AC-DC 15V 3A Switching Power Supply Circuit Module 3000MA Original Bare Board For LED Monitor 100-240v 50/60HZ Power Board SMPS - EUR 2,65
Quality seems ok, and cheap.. read somewhere that the efficiency is around 80%...
Connect together with toroidal to 220v
6.5*4.5*2.6cm

- 220v -> 12V + 12V -> -12V to get both will cost around EUR5,25. The first gives 12v and the second uses that to give -12v, then use the first and the second to get 12v and -12v. Not use this is technically the best solution. Parts seem beter quality, max efficiency 88%..

- 220v -> 12V +
TPS5430 - total around EUR 11
First makes 12V from 220V and second takes that and gives 12v and -12v. Athough the seconds board states input range is 5.5-36V, I read somewhere else can't find it anymore) that there is a change this is a step-down product needing at least 1v more as input. So might need a 15V input like this which is bigger.

I think that I will try the last option, small components, beter efficiency and use the 12V supply, not the bigger 15V. Even if the output is less then 12v the balanced board takes ± 5V ~ ± 15V, as long as it is stable.

 

[JMFahey]

You ask too many questions and we must read A TON of data to answer you, then you cap it with a meager $100 budget , to boot stuff must fit inside a barely adequate case.

You are asking us to read 54 (fifty-four) links to answer, are you out of your mind?

Do your own homework first, reduce it to 2 or 3 options you can´t decide between and ask again.

 

[atamgp]

You ask too many questions and we must read A TON of data to answer you, then you cap it with a meager $100 budget , to boot stuff must fit inside a barely adequate case.

You are asking us to read 54 (fifty-four) links to answer, are you out of your mind?

Do your own homework first, reduce it to 2 or 3 options you can´t decide between and ask again.

Relax man.... It's not mandatory to read if you don't want to. I think a lot of people are in the same boat. How to go form many possibilities to something to work with. I am sharing my journey here for those who are also new to this. If you are not interested to read, please move on. Others are welcome, and "if" they have suggestions then I am very happy to hear them...

sgrossklass suggested to consider balanced and had a good point which I am going with.
Also I look for a board around 100, total amp will cost around 250 I suspect, which is not nothing.

What I miss most in other threads is how they made a lot of other choices..

 

[phuqit]

For what it's worth, I used 3eaudio class-D amps here:
TPA3255-2CH-260W | 3e Audio

They accept balanced signal, and are absolutely awesome.

 

[atamgp]

For what it's worth, I used 3eaudio class-D amps here:
TPA3255-2CH-260W | 3e Audio

They accept balanced signal, and are absolutely awesome.

Wow, that is a really nice amp. Reading the forum here the sound seems very good, around top of class D and it has integrated fully differential inputs....

Shame the seller has no available units left. Will keep an eye on his eBay account. Thank's for the info