Small cheap pre amp card/ boards , sound quality?

[DanielT]

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.

Well then it is undeniably completely useless. What are they doing? Can they not count on the values of the capacitors? How difficult is it?

In other words, a complete lottery to buy these cheap pre amp board from China.

Edit:
Aha, he has tested several. His conclusion,: It's a gamble to buy these cheap pre amp board.

One more:

 

[antcollinet]

Aha, he has tested several. His conclusion,: It's a gamble to buy these cheap pre amp board.

Well, yes it is - but worst case you have a PCB which is relatively easy to mod (as he did) to a working version with a small bit of understanding of OP AMP circuits.

 

[Draki]

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.

But...removing the two 330 pF caps (as he did) cured the anomaly! Obviously the board was mis-populated (they used a wrong cap value), and he claims that in fact no cap is needed at that position. So with this mod, the board still has some use. As he said, measuring "flat as a pancake up to 80 Khz".

 

[DanielT]

Well, yes it is - but worst case you have a PCB which is relatively easy to mod (as he did) to a working version with a small bit of understanding of OP AMP circuits.

Sure, but if so, it's better to have complete control yourself and see post # 10 in in this thread.
It does not get cheaper, that DIY. On the contrary more expensive (maybe with import from China, shipping cost, tax, customs and so on, it rolls on with money). But so much more fun. In addition, it is not directly the large wallet you open up.

Okay, it is probably mostly for testing, which is mentioned in the Youtube video (post # 10), so you need to count on, if you are going to use it for a long time, how long the batteries last (you can have rechargeable). Flexible with batteries per se:

Ampere-hour - Wikipedia

en.wikipedia.org

 

[antcollinet]

But...removing the two 330 pF caps (as he did) cured the anomaly! Obviously the board was mis-populated (they used a wrong cap value), and he claims that in fact no cap is needed at that position. So with this mod, the board still has some use. As he said, measuring "flat as a pancake up to 80 Khz".

As I say above. But you really shouldn't have to fix this sort of basic mistake.

 

[antcollinet]

Sure, but if so, it's better to have complete control yourself and see post # 10 in in this thread

It does not get cheaper. On the contrary more expensive but so much more fun. In addition, it is not directly the large wallet you open up.

It is much easier to make reliable circuits with a pcb.

 

[Wirrunna]

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.

I put 6 of these Sparkfun 1646 modules in a box with RCA plugs and a 15-0-15 power supply board powered by a wall wart. Gives the option of balanced output from my two miniDSP 2X4 HDs. Swapped my Topping PA5 onto balanced from the RCA to TRS cable. I couldn't hear any induced noise but I reckon the PA5 sounds better now than when it was using the RCA to TRS cable.
Required a bit of measuring and resetting of levels in the miniDSP, not just dropping the channel through the 1646 by 6db.

 

[babadono]

I used both the SparkFun 1646 BOB and the 1206 BOB in my TPA3255 amp. Brought the signal in differential converted to single ended to a pot then back out to differential to feed the inputs of the 3255. I wanted the pot to be able to adjust the overall gain. I switched the device on the input board from a 1206 to 1200 so would not lose the 6dB. So basically the input level can be adj from minus infinity to +6dB. Also got rid of their funky TRS jacks and went XLR. It was a fun little project, works great. I use the amp on my bass bins in a bi amp set up without the output from a Xilica active crossover.

 

[DanielT]

I put 6 of these Sparkfun 1646 modules in a box with RCA plugs and a 15-0-15 power supply board powered by a wall wart. Gives the option of balanced output from my two miniDSP 2X4 HDs. Swapped my Topping PA5 onto balanced from the RCA to TRS cable. I couldn't hear any induced noise but I reckon the PA5 sounds better now than when it was using the RCA to TRS cable.
Required a bit of measuring and resetting of levels in the miniDSP, not just dropping the channel through the 1646 by 6db.

I used both the SparkFun 1646 BOB and the 1206 BOB in my TPA3255 amp. Brought the signal in differential converted to single ended to a pot then back out to differential to feed the inputs of the 3255. I wanted the pot to be able to adjust the overall gain. I switched the device on the input board from a 1206 to 1200 so would not lose the 6dB. So basically the input level can be adj from minus infinity to +6dB. Also got rid of their funky TRS jacks and went XLR. It was a fun little project, works great. I use the amp on my bass bins in a bi amp set up without the output from a Xilica active crossover.

Sparkfun...Interesting. I remember that. Thanks for the information and pictures.

 

[babadono]

The guys at THAT Corp know their stuff. Their InGenius and OutSmarts ICs are great. I used their VCAs and RMS level detectors when I re built/re furb'd a couple DBX 4BX dynamic range expanders also. Great people to work with. They helped me find schematics for the 4BXs and were genuinely interested that someone wanted to go through the effort. Some of them came from DBX originally.