Small cheap pre amp card/ boards , sound quality?

[DanielT]

Has anyone tried any of these small cheap pre amp cards, with OP amp NE5532, from China? They hardly cost any money at all but are they ok? Attach some pictures of what it looks like (took some at random)

pre amp ne5532 for sale | eBay

Get the best deals for pre amp ne5532 at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

Anyone measured any of them?

I became a little curious about these because I wrote in the thread (post # 2811):

Topping PA5 Review (Amplifier)

Just tested, both signals on each XLR generates 2.065V (expected) and obviously 4.13V if you compare them to each other using a 1kHz sine wave input. The TRS to RCA cable is also outputting perfect 2.065V on the same wave. I tested again with a louder white noise source and still, on the same...

audiosciencereview.com

Edit:
I can buy such a cheap one and send it to Amir. He can keep it. If he feels like testing one.

 

[antcollinet]

I'd be interested in any measurements on one of those for similar reasons (Assuming Topping PA9/PA7 arrives with balanced inputs only)

Though I'd possibly be more interested in this:

KMTech 2-Channel DRV134 based Differential Balanced Line Driver converter | eBay

Manufacturer: KMTech Design (UK). A high performance, stereo, low noise unbalanced-to-balanced adapter by KMTech Design. However if your priority is sound quality and value for money, then look no further!

www.ebay.co.uk

 

[DanielT]

I'd be interested in any measurements on one of those for similar reasons (Assuming Topping PA9/PA7 arrives with balanced inputs only)

Though I'd possibly be more interested in this:

KMTech 2-Channel DRV134 based Differential Balanced Line Driver converter | eBay

Manufacturer: KMTech Design (UK). A high performance, stereo, low noise unbalanced-to-balanced adapter by KMTech Design. However if your priority is sound quality and value for money, then look no further!

www.ebay.co.uk

It was also interesting.

I wonder, what could go wrong? High performance OP amp with low distortion some resistors and capacitors. It should be fundamental and easy for any EE to construct a sensible one? Though I do not know.

 

[KSTR]

Those boards don't look to be very well designed (neither schematic nor layout), notably the small $2.11 one is weird (inverting circuit).

The $3.44 one is a bit better -- standard non-inverting circuit but it is single-supply, with the I/O's AC-coupled. Single supply could actually be an advantage in some cases. I'd go with this board as it much more modding-friendly than the other (covert to split-supply and remove the AC-coupling, and of course setting the gain exactly.

I would suspect measurements will not completly bad but not stellar either. We have very basic quality level of everything here.

I might volunteer to measure these as I don't think we need Amir to waste his precious time on gadgets like this.

 

[DanielT]

Those boards don't look to be very well designed (neither schematic nor layout), notably the small $2.11 one is weird (inverting circuit).

The $3.44 one is a bit better -- standard non-inverting circuit but it is single-supply, with the I/O's AC-coupled. Single supply could actually be an advantage in some cases. I'd go with this board as it much more modding-friendly than the other (covert to split-supply and remove the AC-coupling, and of course setting the gain exactly.

I would supect measurements will not completly bad but not stellar either. We have very basic quality level of everything here.

I might volunteer to measure these as I don't think we need Amir to waste his precious time on gadgets like this.

Great if you want to test! But you have to set aside some test time yourself for that. Is it OK?
I can pay for one. Unless you want one yourself? We solve the practical via PM.

Now I'm most curious but tonycollinet seems to be in need of one, as he mentions. Maybe more rewarding if it is tested? Then you two get to solve the practical details around it.

Exciting.

 

[Wirrunna]

Here is another one based on the That Corp 1606/1646

SparkFun THAT 1646 OutSmarts Breakout - BOB-14003 - SparkFun Electronics

The THAT 1646 OutSmarts Breakout Board offers an easy solution to adding a balanced audio output to your circuits. The THAT OutSmarts technology has been d

www.sparkfun.com

THAT Corporation 1606/1646 OutSmarts Balanced Line Driver ICs

The THAT 1606 and 1646 are a new generation of monolithic differential line drivers offering improved performance over conventional cross-coupled designs. Based on a high-performance, fully differential op amp and laser-trimmed thin-film resistors, both exhibit low noise and distortion, high...

www.thatcorp.com

I have these on order in case the RCA output from my miniDSP 2X4 HD is too low for the PA5 that is due in a week or two.

 

[KSTR]

Now I'm most curious but tonycollinet seems to be in need of one, as he mentions.

The DRV134-based boards are also very bare-bone, plus the chip is not exactly state-of-the-art anymore (it's a bit noisy).

I have these on order in case the RCA output from my miniDSP 2X4 HD is too low for the PA5 that is due in a week or two.

The Sparkfun PCB looks great and those 1646 line drivers from THATcorp are a known-good solution. That's the one I'd probably go for to facilitate balanced output and a 6dB gain boost, nice find! Comprehensive docs also stand out here.

 

[antcollinet]

The DRV134-based boards are also very bare-bone, plus the chip is not exactly state-of-the-art anymore (it's a bit noisy).

A device based on the DRV134 is measured here, with 122dB sinad - so noise can't be that bad if the test is accurate:

Measurements of TransAudio（China）DRV134 RCA To XLR Adaptor Converter

www.audiosciencereview.com

 

[antcollinet]

Having said that, I've just found the sparkfun gadgets at a UK distributor - and they look small enough to almost make an 'inline cable" type adapter (With copious amounts of heatshrink - or a small plastic box.

 

[DanielT]

For those who want to try DIY. Even those who do not feel like doing that pre amp can learn a little about how it works with OP amps.Basic for you EE, but for others who are a little curious.

I'm not an EE but I will try building one. Mostly because it seems fun.

I attach some screenshots from the video.

Edit:
Note. I try to DIY it because it's fun. I have no idea about its performance. That in itself is of secondary importance, to me in this case. However, he tests to measure the distortion and it is (with his measuring equipment) so low that it is not measurable.

 

[Draki]

As it happens ... just finishing a 4 channel line (pre)amp with THAT 1646 modules.

 

[bsas]

As it happens ... just finishing a 4 channel line (pre)amp with THAT 1646 modules.

Ah! I am very curious about that

I recently got one of those DRV134 from AliExpress just to test some stuff, this one to be precise:

125.0US $ |Finished Precision Dual Channel Single-ended To Balance Audio Converter Rca To Xlr Drv134 Converter - Home Theater Amplifiers - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

So, in my case I can use a SE (RCA) preamp to boost a signal and then convert to balanced since I think those can take upto 5V or 10V if I am not mistaken.

But, like other people already said, I don't believe the noise and the precision on those converters is super top notch. It would be great to be able to make my own with better circuit and better parts

 

[antcollinet]

Ah! I am very curious about that

I recently got one of those DRV134 from AliExpress just to test some stuff, this one to be precise:

125.0US $ |Finished Precision Dual Channel Single-ended To Balance Audio Converter Rca To Xlr Drv134 Converter - Home Theater Amplifiers - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

So, in my case I can use a SE (RCA) preamp to boost a signal and then convert to balanced since I think those can take upto 5V or 10V if I am not mistaken.

But, like other people already said, I don't believe the noise and the precision on those converters is super top notch. It would be great to be able to make my own with better circuit and better parts

I think that is the one tested with 122 dB sinad. Why do you think it is poor?

 

[bsas]

I think that is the one tested with 122 dB sinad. Why do you think it is poor?

Don’t know, just out of multiple comments that the DRV134 chip is noisy.

I have zero complaints on it and sounds exactly the way I wanted it to, but, I don’t have fancy measurement tools or electronics background to be sure (one of the reasons I am here at ASR, to learn more ).

 

[antcollinet]

Don’t know, just out of multiple comments that the DRV134 chip is noisy.

I have zero complaints on it and sounds exactly the way I wanted it to, but, I don’t have fancy measurement tools or electronics background to be sure (one of the reasons I am here at ASR, to learn more ).

This is why I like people to back up their comments with measurements. Doesn't have to be their own measuremnets, but if they say "that is excellent" or "that is lousy" without being able to point at somthing to back it up, I pay little attention.

As far as I can tell that device measures well, and you say it gives you what you want. I don't think you need to try and make a better one - in fact it will be difficult to do so - unless you want to as a learning project.

 

[DanielT]

As it happens ... just finishing a 4 channel line (pre)amp with THAT 1646 modules.

Feel free to tell us more. How do you think it turned out? It looks nice.

 

[DanielT]

Don’t know, just out of multiple comments that the DRV134 chip is noisy.

I have zero complaints on it and sounds exactly the way I wanted it to, but, I don’t have fancy measurement tools or electronics background to be sure (one of the reasons I am here at ASR, to learn more ).

I also do not know what the performance on these small boards is, so I'm curious.

Here about OP amp. They can be used for many things:

An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.[1] In this configuration, an op amp produces an output potential (relative to circuit ground) that is typically 100,000 times larger than the potential difference between its input terminals. Operational amplifiers had their origins in analog computers, where they were used to perform mathematical operations in linear, non-linear, and frequency-dependent circuits.

Operational amplifier - Wikipedia

en.wikipedia.org

 

[DanielT]

Here is a test of such a small pre amp board.Is not the same as the pre amp board I took as an example my first post in this thread?

Video, measurements with ocilloscope.Not straight FR, despite low gain, but he fixes it so it becomes "flat as a pancake"

Too high a value of a capacitor is the reason why the FR is not straight. He wonders if this has to do with statability but thinks that the value of the capacitor that causes the problems (330 pF) is too high. It should be around 33 pF.But what does he do, he just removes it completely. Do not insert another capacitor. Eh, okay...It seems to have to do with negative feedback, from what I can see. Maybe I'm wrong. I'm not an EE.

But is there such a big discrepancy in FR? What is this in dB?

I do not know if he in the video is right in fixing that board. It is up to you who are doing electronics to decide.

 

[Draki]

Feel free to tell us more. How do you think it turned out? It looks nice.

Work in progress. Will take another couple of weekends, time permitting.

EDIT: here is DRV134/135 done right - https://sjostromaudio.com/pages/index.php/hifi-projects/148-ubc01-audio-balanced-driver

 

[antcollinet]

...

But is there such a big discrepancy in FR? What is this in dB?...

Voltage roughly halves from low frequency to high frequency - so around 6dB. Put into a power amp, this would sound wooly and muffled.

As he said - not hifi.