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 Post subject: El-Cheapo class D amps?
PostPosted: Nov Wed 14, 2018 6:12 pm 
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Joined: Apr Sun 23, 2017 11:22 pm
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Location: 44035 (Near Cleveland Ohio)
I have several '70's and '80's receivers that are pretty much salvage items - missing parts, etc. I was thinking of retrofitting a couple with class D linear amps, especially since they're so inexpensive. Any thoughts on the sound quality? I'm familiar with how they work, but was wondering how they actually sound. Any comments appreciated.

Dan


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Wed 14, 2018 8:15 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4278
Location: Boston, MA USA
I have a Pyle PTAU45 class-D stereo amplifier, and I think it sounds excellent. Every bit as good as the large linear solid-state amplifier there before. The stereos in both my newer cars have class D amplifiers and I think they sound excellent as well.

It is very important to get a class-D amplifier with enough power so that it will never clip. No solid-state amplifier handles clipping gracefully but class-D is particularly terrible when it clips.

-David


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Thu 15, 2018 12:21 am 
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Joined: Nov Fri 10, 2006 12:24 am
Posts: 2528
Location: Thornhill, Ontario, Canada
This article is in the November 2018 IEEE Spectrum magazine:

https://spectrum.ieee.org/consumer-elec ... t-of-cheap

Looks like an amazing development... a major challenge to high-end audio amplifiers. It is based on the TPA3250 chip... here's the spec sheet:

http://www.ti.com/document-viewer/TPA32 ... LASE992849

Enjoy!
Cheers,
Roger

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Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Thu 15, 2018 12:30 am 
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Joined: Oct Wed 25, 2017 12:10 am
Posts: 233
Location: Idaho / Colorado
I have one of these el-cheapo amps.

The one I have is one of the ubiquitous ones you can find on Amazon for $30-ish, using a Texas Instruments chip.

It clips pretty easily. You can fill a room with acceptable sound easily enough (e.g. for a movie), but just barely, and no more.

The quality is OK. Obviously not the best. Does not sound as good as, for example, a good Yamaha receiver from the 80's. And definitely does not sound as good as a tube amplifier. But it sounds good enough for most practical purposes, and you will only hear the difference if you don't have crappy speakers.

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I flermmed the plootash just like you asked.


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Thu 15, 2018 1:00 pm 
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Joined: Nov Sun 11, 2018 12:32 am
Posts: 30
JohnAudioTech is a YouTube channel where a guy tests and reviews tons of those cheap-o Chinese amps, talks about voltage needed for full power, and does a brief discussion of how they sound. As I recall he's done dozens of different models. It's probably a good starting point to get a feel for which chips will be the best performers.

https://www.youtube.com/channel/UC8SPQG ... z4E8xvFEtw


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Sat 17, 2018 3:35 am 
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Some of the cheapest class D amplifiers really sounds terrible, even if not driven into the clipping region. Whatever technology you use you can't get anything (good) for nothing.
Good quality vintage receivers from the 70ies by the biggest names like Marantz, Sansui, Pioneer, Yamaha, Kenwood, etc... are still in demand and some of them are now (expensive) collectibles. Retrofitting any of these with modern class D amp modules will only depreciate their value (actually bringing them close to zero) without (in most cases) adding any sonic benefits.
Old Hi-Fi gear using standard (through hole, discrete parts) technology can allways be fixed faster and for less money than adding (good quality) class D amp modules and implementing all the needed circuit changes (power supply, signal routing, etc...)
I would only consider the class D retrofit option in cheaper units using hybrid amp modules (STK, Sanken or similar) which are no longer available and/or too expensive (like some Technics power amp modules). But usually these low-end amps doesn't worth all the efforts and expenses needed to bring them back to life.


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 Post subject: Re: El-Cheapo class D amps?
PostPosted: Nov Wed 21, 2018 5:06 pm 
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Joined: Jan Mon 12, 2009 7:38 am
Posts: 1211
Location: homestead, fl
sparkydan,

i did what you're pondering for a friend that had an old receiver he wanted to keep using. here's the write up.

https://www.instructables.com/id/Bringi ... tz-stereo/


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