Hybrid Amp Question

Tube or solid-state, this section goes to eleven!

Hybrid Amp Question

Postby armkon » 17 Jun 2017, 06:32

As we all know there are more and more new amps that are using hybrid tube+ss PA. We have orange micro series, joyo bantamp series amp and some other amps that share this technology.

I'm searching for some good chip power amp and buffer section that will work good with tubes and jfets for testing purposes and playing at home, 20W will be ok.

I have see pictures of the orange pcb and it use sta540, but cant find any guts of joyo bantamp pcb.
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Re: Hybrid Amp Question

Postby Manfred » 17 Jun 2017, 08:38

I attach the Marshall Valvestate 8020 schematic.
The power stage is a so-called current feedback amp.
This means that the output current through the speakers is part of the feedback.
That current generates a feedback voltage by means the 0.33 Ohms resistor in series with the speaker.
The current feedback increases the output resistance of the power amp just as a tube power amp has.
The higher output resistance, that is, a smaller damping, makes that the speaker has a longer decay,
which gives an tonal colouration.
IMO, the power amp is easy to build.

Marshall-Valvestate20-20W-8020-Schematic.pdf
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Re: Hybrid Amp Question

Postby armkon » 17 Jun 2017, 12:30

Yes but what is the best power amp in a chip for this kind of things like a hybrid amp?
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Re: Hybrid Amp Question

Postby phatt » 18 Jun 2017, 09:28

When it comes to guitar amplification,,, it's anything that works (within reason) :wink:
Chip amps are just a building block.. "it's the way you design and build the surrounding circuitry that makes any mojo happen" :secret:
Which is what *Manfred* just explained.

LM1875 or similar will work but remember that the power supply plays a big part and some of those little practice amps use only a small power supply which limits clean head room and hence most clap out badly when trying to run at louder volumes. Which is not the fault of the Chip,, just the pathetic transformer they use.
Phil.

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Re: Hybrid Amp Question

Postby bool » 18 Jun 2017, 15:00

Back in 70s and 80s in Europe, the TBA810 was a popular chip-amp.

TDA2030, TDA2040 and TDA2050 seem like usable workhorses that have been around like forever.

TDA7294 could be a valid candidate for some abuse.


The quote of the day: "With greater power comes greater responsibility".


But if you are THAT kind of guy, there's something to be said about addictive qualities of the smell of burned silicon ... resistors do have a sweet smell to them too ...
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Re: Hybrid Amp Question

Postby Manfred » 19 Jun 2017, 08:46

TDA2030, TDA2040 and TDA2050 seem like usable workhorses that have been around like forever.


On this I am in complete agreement with you.

The TDA2050 is applied in the current feedback circuit of the Marshall Valvestate VS30 and VS230 poweramp.

vs30-60-02.pdf


v230-61-02.pdf
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Re: Hybrid Amp Question

Postby bool » 19 Jun 2017, 11:35

Yeah, these TDAs are quite sturdy --when applied properly-- ... but man, if you screw up the circuit somehow and --only whisper-- a wrong word when they're powered up; up in smoke they go.

To the OP; so take care with PSU decoupling and grounding and layout in general. Special care should be taken to cool these chips properly; afterall these chips are the same tiny thermal contact size as the usual TO220 packs.

Much of the practical advice and wisdom could be taken straight from "gainclone" DIY-ers with some google-fu.
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Re: Hybrid Amp Question

Postby lakesidepark » 18 Sep 2017, 19:58

Did you search for marshall mercury, hybrid preamp is solid state, power is EL84. Interesting amp.

https://www.zikinf.com/_gfx/annonces/dy ... 1491118406
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