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chip amps: Almost everything you ever wanted to know


DizRotus

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Actually, the mising parts are Evox blue box-type film capacitors. It's quote possible that the missing capacitors are used as bypass capacitors to the primary capacitors. This is widely done with audio circuits for various reasons that would take a long time to explain. Some circuits benefit from bypass aps, and some do not. It definitely is different than what is pictured in the eBay ad from seller smsl-china. Below is a photo of my SA-S1 amp.

post-40256-13819859034536_thumb.jpg

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Actually, the mising parts are Evox blue box-type film capacitors. It's quote possible that the missing capacitors are used as bypass capacitors to the primary capacitors. This is widely done with audio circuits for various reasons that would take a long time to explain. Some circuits benefit from bypass aps, and some do not. It definitely is different than what is pictured in the eBay ad from seller smsl-china. Below is a photo of my SA-S1 amp.

I'm sure you're correct about those being capacitors. What is the larger component near the power switch in your amp and missing from these? Would it make any sense to install the deleted components?

I suspect the SMSL-China sales department misunderstood the engineering department when they sent the following:

"Dear dizrotus,

Engineering Department has just answered me: This is the four auxiliary resistors.

They just only for aesthetic add. AMP no any impact for structure and quality.

I intend to suspend sale S1. Until update photos (as your photo). To avoid future similar questions.

R & D department have interpreted power. But we not, for customers.

- smsl-china"

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And most of these chip amps can be made to sound even better if one carefully implements different parts. In my SA-50 I use new coils, different input caps and all the caps between chip out and speaker terminals. It took me some time to find the 'correct' parts (in terms of tonality), but I am pretty happy with the amp right now. Oh, and removing the volume pot didn't do any harm either....Big Smile.

Wolfram

I, and possibly others, would be interested in photos and details regarding the modifications described above. I plan to purchase an SMSL SA-50 as soon as SMSL-China send the "all clear."

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Actually, the mising parts are Evox blue box-type film capacitors. It's quote possible that the missing capacitors are used as bypass capacitors to the primary capacitors. This is widely done with audio circuits for various reasons that would take a long time to explain. Some circuits benefit from bypass aps, and some do not. It definitely is different than what is pictured in the eBay ad from seller smsl-china. Below is a photo of my SA-S1 amp.

I'm sure you're correct about those being capacitors. What is the larger component near the power switch in your amp and missing from these? Would it make any sense to install the deleted components?

I suspect the SMSL-China sales department misunderstood the engineering department when they sent the following:

"Dear dizrotus,

Engineering Department has just answered me: This is the four auxiliary resistors.

They just only for aesthetic add. AMP no any impact for structure and quality.

I intend to suspend sale S1. Until update photos (as your photo). To avoid future similar questions.

R & D department have interpreted power. But we not, for customers.

- smsl-china"

I'm not sure why SMSL would install capacitors that they consider unnecessary. However, it is possible that those missing bypass film capacitors (all really low capacitance values) have no genuine impact on the sound quality. The larger component near the power switch is just a larger--but still a small value--blue box film cap from Evox-Rifa. I haven't followed the PCB traces, but I suspect it is a bypass cap for the two Nichicon power supply caps connected to the Tripath TA2020 chip.

I've added a Bill of Materials for replacing some components in the SMSL SA-S1 T-amp. The upgraded components are based on the Tripath TA2020 recommended circuit design that is featured in the Tripath TA2020 specification paper. Most of these components like the Wima film capacitors and Panasonic electrolytic capacitors come from Mouser Electronics, an online catalog-based distributor of many electronic components. The exception are the Mundorf M-cap film capacitors that are available from Part Connexion.

I might buy an extra SA-S1 and upgrade these components. To be honest though, I'm so pleased with the SA-S1 in stock form that I may move onto other DIY audio projects. The stock components are actually good-high quality. Making changes may or may not make a big difference. For me, touching up the solder joints betwen the speaker binding post and RCA connectors and the main PCB made a significant improvement in sound quality. A friend of mine who also has an SMSL SA-S1 amp did the same and heard the improvements. I use Cardas Quad Eutectic Solder for all my audio projects.

As for the SMSL SA-50, I've read mixed reviews about STM TDA7492-based Class D amps. It is not a Tripath-based amp, so it cannot be called a T-amp. For my 98dB efficient Klipsch Forte II's, I'm satisfied with the power output of the SA-S1.

S.M.S.L. SA-S1 Bill of Materials.pdf

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One important matter to address is the DC bias or offset, which can be adjusted as follows:

1. Power off the SMSL SA-S1 amp

2. Remove the top cover and locate the two trim pots on the PCB next to the volume pot.

3. You must use a DMM and connect the leads to the speaker outputs (Red-to-Red, and Black-to-Black) for each channel. Avoid contact between the Red and Black test leads as they are connected to the speaker outputs, or a short circuit at the output will occur and result in possible permanent damage.

4. Insure that your DMM is reading DC voltage in the mV range (i.e., 200 mV).

5. Power on the amp with the volume pot turned down and with no input signal coming through the RCA input connectors.

6. Using a small screwdriver, adjust the pot corresponding to the measured channel to achieve a voltage as close to 0 mV as possible. Don't be too concerned with the slight fluctuations in voltage while making the adjustment. Just try to get an average hovering around 0 mV.

7. Power off the amp, remove the test leads, and repeat again for the other channel.

This will optimize the amp's output and help prevent any possible damage of your speakers. The result is lower distortion. In my amp, the factory settings were within +/- 50mV. My buddy's SA-S1 measured around +/- 150mV!

One reason why I like the SMSL SA-S1 is that the amp has the adjustable DC bias pots installed on the board. The Lepai TA-2020 and other T-amps do not have this feature, and you have to figure out how to add them into the input circuitry.

My vintage Sony TA-3060 SS power amp has similar DC bias and offset pots for this type of adjustment. Many of the low cost Chinese T-amps do not.

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The SA-50 does not offer the chance to adjust DC offset.....but still it sounds really very good [:)].

What I did to mine was removing the volume pot, next I located the two input caps and replaced them with Siemens MKL and added two Siemens KS on top (those orange thingies).

The coils I chose are made by Bourns, additionally there are for capsbtweens thos and the rca output. Replaced those as well with the same combo as above (the KS only one the caps in the sugnal path). Then I bought a Meanwell PS that has a swithing frequency of 96Khz. Oh and I also installed different input jacks.

post-5631-13819859199818_thumb.jpg

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The SA-50 does not offer the chance to adjust DC offset.....but still it sounds really very good Smile.

What I did to mine was removing the volume pot, next I located the two input caps and replaced them with Siemens MKL and added two Siemens KS on top (those orange thingies).

The coils I chose are made by Bourns, additionally there are for capsbtweens thos and the rca output. Replaced those as well with the same combo as above (the KS only one the caps in the sugnal path). Then I bought a Meanwell PS that has a swithing frequency of 96Khz. Oh and I also installed different input jacks.

Siemens MKL = metallized lacquer film

Siemens KS = Polystyrene film

Very nice indeed. I haven't read too much about these Siemens caps on the American audio forums, but your choices make a lot of sense. I may have to check out eBay and search some of these out, especially the Siemens KS Polystyrene caps. Next to Teflon, Polystyrene is a good cap material choice for audio, especially in cool running Class D amps where there is no problem with heat affecting the Polystyrene caps.

The BHC slit foil electrolytic cap is very high end too. These caps are used in vintage Naim and Rotel amp power supplies.

When you removed the volume pot, did you replace the pot with 10k or 20k resistors?

Thank you very much for sharing your upgrades on the SMSL SA-50 amp.

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And - looking at the pic I forgot something: I replaced the three PS caps with one BHC Slit-Foil cap.

Wolfram

Which is as big as the whole amp. Love it!

I read that one guy was using one of these in his T-amp power supply and getting much improved bass.

http://www.monstercable.com/mpc/productPageMPC.asp?pin=2950&section=two

Maybe the car audio guys are onto something.

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Rich,

no resistor instead of the volume pot. I actually wired the input signal directly to the input caps using a kind of litzwire - and yes, even that wire makes a difference.

No idea about that cap mentioned in the link - but 1uF at that price......[:o].

Wolfram

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Rich,

no resistor instead of the volume pot. I actually wired the input signal directly to the input caps using a kind of litzwire - and yes, even that wire makes a difference.

No idea about that cap mentioned in the link - but 1uF at that price......Surprise.

Wolfram

Compared to some of the cheap wire and thin PCB traces, good wire can make a noticeable improvement.

The cap in the link is 1F = 1,000,000uF. That would explain part of the price. The rest is just profit margin based on marketing hype.

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Rich,

no resistor instead of the volume pot. I actually wired the input signal directly to the input caps using a kind of litzwire - and yes, even that wire makes a difference.

No idea about that cap mentioned in the link - but 1uF at that price......Surprise.

Wolfram

Compared to some of the cheap wire and thin PCB traces, good wire can make a noticeable improvement.

The cap in the link is 1F = 1,000,000uF. That would explain part of the price. The rest is just profit margin based on marketing hype.

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  • 3 weeks later...

I'm enjoying the newly arrived SMSL SA-50. So far it sounds good. I've not noticed a difference from the SA-S1 in quality.

On the other hand, I replaced the Lepai TA2020 with the SA-S1 in the boombox and noticed a large difference. The Lepai plays much louder than the SA-S1 from the same sources. The sound quality of the SA-S1 is better than the Lepai, but it runs out of gas a bit soon.

The SA-50 also plays considerably louder than the SA-S1 in the same system.

Now that I have 2 TA202s, a SA-S1 and a SA-50, I'll start tinkering. First to go under the soldering iron will be one of the Lepais.

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I'm enjoying the newly arrived SMSL SA-50. So far it sounds good. I've not noticed a difference from the SA-S1 in quality.

The SA-50 also plays considerably louder than the SA-S1 in the same system.

Now that I have 2 TA202s, a SA-S1 and a SA-50, I'll start tinkering. First to go under the soldering iron will be one of the Lepais.

Hi Neil,

That's interesting that you don't hear a difference between the SMSL SA-50 and SA-S1 amps in terms of sound quality except volume. With the mods you have planned for the Lepai amps, do you expect the results to sound better than the SMSL SA-S1?

With these amps or the Lepai TA2020 amps, I believe improvements can be made with using better power supplies. I'm looking into the Paul Hynes power supply regulator module from DIYParadise or the regulated power supply kit from Welborne Labs. The Paul Hynes solution is more expensive since I would need to get a power transformer and enclosure, but I have read positive reviews with using his module with Tripath TA-2020 amps. The Welborne Labs offering looks attractive, but I've read some spotty reviews about Welborne Labs' service.

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Rich-

The SA-50 just arrived and I've not listened carefully fo any extended time. These almost Medicare eligible ears think they both sound very good.

That doesn't mean there isn't a sound quality difference or that they won't get tweaked.

Please share your results. I'll keep haunting DIY forums for possible tweaks.

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