CA 340A SE LM3886 based amp - Upgrade advice please.

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#421
measure the DC at the output of the buffer opamps.

I see from post417 that the SE has no DC blocking at the input.
But has retained DC blocking at the buffer.
Removal of the power amp DC blocking will allow buffer offset to enter the power amp.
Removal of the NFB DC blocking will allow the power amp to multiply any offset presented to it's input, plus/minus it's own offset.
 
#422
There are DC blocking caps at each input RCA. At preamp 'buffer' input. Between preamp buffer and pots. Before powerchips (LM3886). and of course there is a cap to ground in the feedback.

I have measured DC offset at the output of the preamp buffer (with LM4562) and it was very low. I cant remember the exact figure but it was mentioned earlier.
 
#423
Just leave the one before power chips and get rid of the rest.

My system has coupling/blocking caps in these places:
* each source (otherwise you get noisy volume pot)
* none in preamp needed
* each power amp

This seems like as low as you can practically go without some kind of trade-off or problem.

Simon

Alternatively none in sources but one in the preamp would be fine I think.
 
#426
Airlink transformers have quoted me £63.83 .(inc shipping) for a custom trafo.

300VA 22-0-22 (ct) with dual secondaries 17-0-17, potted. Thats a drop-in replacement for the stock 340A trafo. Dimensions are 60*110mm.

Its a bit pricey but its bespoke for the 340A, should I go for it?

Mike.
 
#428
I would like to see (hear) what the SQ is like with the input switching ic bypassed first. If this and the other component swaps are giving me really good sound then I'd say its worth going for the trafo.

Theres also the super quiet PFM teddyregs to build and install on the preamp section.

My TDL's like good power and while I understand a bigger trafo wont give me more watts, it should enable the chips to deliver more current, no? Also the added headroom is supposed to improve the bass. The 840A I tried has a massive trafo and that sounded very smooth and effortless (4 Sanken chips per channel).
 
#431
AndrewT said:

2pair of Sankens is a completely different amplifier from the chipamp.
It's only guessing where the improved SQ came from.
Click to expand...


Of course.

4 Sanken's (might be 5 IIRC) per channel is a different beast alltogether, not to mention the guarded 'Claass XD' technology.

I liked it but for the lack of dynamics. Apparently the 840A V2 is better.
 
#432
I don't know if you know Lee/Thomo very will Mike, but I know he once made an LM3886 chip amp and experimented with double transformers. He said he got much better bass from doing it. Brent/Rowey also doubled up in his Marantz PM66KI and I know well what that sounds like - impressive!!! He suspects the output power of his amp went up quite a lot (also due to smoothing caps) because the rail voltage rose by a few volts and the current available obviously shot up. But then he also upgraded the transistors and heatsinking lol
 
#433
Hi
What can You say about using these Caps as decoup. ?

NICHICON MUSE KZ Audio Grade 10uF 100V
4db9_1.JPG


NICHICON MUSE FW Audio Grade 10uF 63V
45be_1.JPG


I'm planning to stay only two caps - before the op.amp and before the LM. Other will be shorted. Of cource it better to use some film caps, as Mundorf, but they are so big, and if i solder them, there will be long legs, which isn't good for SQ as i know...
 
#434
These might also be worth considering.

As far as I know, Bg N are the best lytic caps and come very close to polypropylene. I dont know this from experience, its just what I have heard.

The Nichicon will definately sound better than the cheap caps allready there, and having less caps in the signal path is good too.
 
#435
SimontY said:
I don't know if you know Lee/Thomo very will Mike, but I know he once made an LM3886 chip amp and experimented with double transformers. He said he got much better bass from doing it. Brent/Rowey also doubled up in his Marantz PM66KI and I know well what that sounds like - impressive!!! He suspects the output power of his amp went up quite a lot (also due to smoothing caps) because the rail voltage rose by a few volts and the current available obviously shot up. But then he also upgraded the transistors and heatsinking lol
Click to expand...


Yeah I know Lee. Hes been in touch to give advice on this project. Im also familliar with Brent. Super bloke, he's given me a lot of free advice too. I'd love to hear his system, bet it sound's 'the dogs' 😀
 
#438
I've never heard those but I think the general audiophile consensus is that Nichicon MUSE are good caps. BG standard, Elna Cerafine, Rubycon ZL and ZA are all ones I've enjoyed personally as bypass caps. Panasonic FC seem to sound a bit harsh, so I couldn't fully recommend those ones, popular as they seem.

Simon
 
#439
Hey Stream.

I dont mind helping. Let me know what you need, I'll see how much it is in the UK, tell you the price in EUR, and post it to you recorded delivery. It might work out cheaper? Theres also group buys which can save you money.

I would suggest trying Wima MKS2-XL. They are radial lead polycarbonate film caps and sound quite good I think. Theyre also really cheap. I reckon for the money they will work really well and should sound much better than the cheap Lytics. Another option is to use some decent lytic caps, nothing too expensive, and bypass them with a small value polycarbonate film cap, or even a small polyproplyle.

My girlfreind is from Latvia so she knows all about the post in the Baltic states. She posted your caps and Diodes today, by Royal Mail recorded delivery.

Mike.
 
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