TDA7297 - What are you looking to see, for DIY?

Folsom · « **Reply #20 on:** 10 Dec 2014, 05:06 pm »

It could drive two. It's capable of 6,000+ uf. You would need a different transformer however, higher ampere. It's hard to find ready to buy dual bobbin transformers of large sizes. The Hammond 229 is probably the best ready to purchase option.

Folsom · « **Reply #21 on:** 10 Dec 2014, 05:27 pm »

I should say however there's no point in using two for your horns if they're efficient. Well, unless you listen in an airport hanger. In a smaller room 87db efficient speakers get plenty loud enough.

There isn't a lack of bass with this amp, like you'll find with the Chinese version for a couple reasons.

S Clark · « **Reply #22 on:** 10 Dec 2014, 07:30 pm »

Would there be anything different if you were designing it to run off batteries? Much of my gear is Dodd and I've got lots of battery options.

Folsom · « **Reply #23 on:** 10 Dec 2014, 07:45 pm »

You'd only need the amp board. I don't know if the batteries will be as good. The way DC filters it just doesn't seem to give the end result that's as good, and the inductance with batteries is high. Your option is to decouple, but decoupling on DC is somewhat moderate compared to what AC filtration typically does. You could probably improve it some with an inductor. However you start with less of different types of noise. I can't tell you whether or not it was retain the authority it has off of a battery; the special Panasonic caps should help.

~~It'll still have much better output because of the zobel~~ I've found the Zobel isn't correct, and have still found the output to remain better with chosen speaker cable. The capacitors on it are considerably faster than batteries with a combined resistance less than a power cord, but I'd still use a reservoir capacitor. I'm sure Pi audio's uberbuss would work and it helps decouple noise from the batteries. My understanding is that LiFePO4 batteries are better, and the super capacitors Vinnie is getting into are a step above that. I've had very pleasant sound from SLA batteries on smaller devices but I wouldn't claim that they have the vibrancy I like for whatever reason.

ejfud · « **Reply #24 on:** 11 Jan 2015, 08:38 pm »

Any updates?

Folsom · « **Reply #25 on:** 11 Jan 2015, 11:01 pm »

Monday/Tuesday I'm ordering the PCB for demo unit transformer and PSU.

Everything was set back a week or two when the capacitor multiplier was introduced. I'm still hoping for Febuarrary for demo unit. When the demo unit is released the GP for kits starts.

Folsom · « **Reply #26 on:** 20 Jan 2015, 01:28 am »

Sigh...

Apologies for the excitment being a little premature. I haven't stopped on the kits. The opposite really!

The capacitor multiplier has done some special things. I quiet literally am relistening to most of my CD library. I find myself moving my body around, not just toe tapping.

I hope everyone appreciates such a refined kit. The investment on time isn't one that is reflected in price in the least. But I do hope to sell a lot of kits. I hope people that have never built an amp kit are enthused and try it.

Vlad · « **Reply #27 on:** 21 Jan 2015, 03:57 am »

Hi Salis,

Can this amp be used with 4 ohm speakers? What would be the output power in this case?
If it is not a secret, what speakers are you using with this amp?

Thanks,
Vlad

Folsom · « **Reply #28 on:** 21 Jan 2015, 05:17 am »

I've been using X-LS Encores, upgraded similar to the ones in the shootout from awhile back. But I've had it on a few things including Piega Premium 5.2's (4ohm)

The datasheet doesn't clarify differences in power to 4/8ohm. However, it's internal current limit makes it produce probably a max that's the same for both. That's the biggest downfall, that it can't drive efficient speakers as well. At 87db efficiency I can enjoy music, but I get a bigger dynamic range with more efficient speakers playing at higher volumes. It clips so nicely that there isn't really a problem for me with my speakers, but it'd be even funner with say some Omegas or something.

Folsom · « **Reply #29 on:** 23 Jan 2015, 03:38 am »

PCB's for demo were ordered today. About 10-15 days out. The parts are on way, too, that I didn't have. Hopefully this means it'll be touring early February, we'll see, I'm taking time to have it right.

I've decided to go with a bigger brother transformer, dual bobbin, that fills in what the capacitor multiplier takes and then some.

The umph the amp has in its full frequency width is what brought me to it, but now it's under control and extends across the volume spectrum so much better. Yea, I'm advertising, but I want someone to freaking hear it!

Sadly, I need better speakers...

shadowlight · « **Reply #30 on:** 23 Jan 2015, 02:09 pm »

Will the amp have option to mute so it can be left on?

Folsom · « **Reply #31 on:** 23 Jan 2015, 04:25 pm »

I hadn't planned on it, but could. I leave mine on with nothing playing, no mute button.

shadowlight · « **Reply #32 on:** 23 Jan 2015, 04:35 pm »

Quote from: Salis Audio on 23 Jan 2015, 04:25 pm

I hadn't planned on it, but could. I leave mine on with nothing playing, no mute button.

I do not know about anyone else but my preference is to have a mute button in place just in case something comes through.

radolang · « **Reply #33 on:** 27 Jan 2015, 12:16 am »

Hello,

I'd like to test different input coupling caps with TDA7297, and wanted to use 2 pole 5 way switch to switch between the caps to be able to hear them side by side, without having to reconnect/resolder anything. I'd like to know whether Type A or Type B configuration would be preferred - see the diagram below. Or there would be no sonic difference between the two?

Or is this entirely bad idea and there would be too much interaction and interference between the caps in such configuration that it would NOT make a realistic comparison test?

Thank you,
Rado

radolang · « **Reply #34 on:** 27 Jan 2015, 05:53 am »

Quote from: mboxler on 10 Dec 2014, 05:03 pm

I'm currently bi-amping my Klipshorns with a pair of these $6 amps using a 12V brick.

Could your power supply drive two (or more) of your amps, or would you suggest separate power supplies per amp?

Mike

Mike, bi-amping using two chips sounds like a great idea. How are you handling the input on each TDA? Have you just connected the inputs on the chip like Salis shown in this picture? Also, have you removed the capacitor from one signal path?

Thanks,
Rado

Folsom · « **Reply #35 on:** 27 Jan 2015, 03:57 pm »

The PCB board that's part of the kit has holes and a long pad for rolling film caps available from places like Mousse. It's not big enough for teflon caps, but almost nothing made is; they're always mounted a bit funny since they're enormous.

mboxler · « **Reply #36 on:** 28 Jan 2015, 02:37 am »

Quote from: radolang on 27 Jan 2015, 05:53 am

Mike, bi-amping using two chips sounds like a great idea. How are you handling the input on each TDA? Have you just connected the inputs on the chip like Salis shown in this picture? Also, have you removed the capacitor from one signal path?

Thanks,
Rado

Hey Rado

The two amps are pretty much as they came from China. I removed the AC/DC diode and all of the terminal blocks, but that was it.

I'll soon (?) start with new boards, replacing the .22 uf input caps with 1.0 uf ones (WIMA...not the best, but i've noticed
the extended bass with the larger input caps.

So...there will be two input caps per amp. One amp (the one driving the K-22-E woofer) will have no volume control, as it's rated at
104db sensitivity. I'll wire the input signal wires straight to the middle holes where the pot would have been.

The second amp will have a pot, as it will connect to the 109db sensitive tophat. I use the pot to match amplitudes...mostly by ear.

My current setup is Computer-->Schiit Bifrost-->Dodd Audio passive pre-->Marchand XM9-->TDA7297's-->KHorns.

I am considering the Reckhorn DSP-6 to replace the DAC/Preamp/Marchands. $399 on Amazon. We will see

Hope that answers your question.

Salis, I have not removed the 100nf snubber cap, mostly because I got confused as to whether it could be removed.
I don't see it on your prototype board, but I do see a small value resistor. Will that serve the same purpose?

Mike

Folsom · « **Reply #37 on:** 28 Jan 2015, 03:06 am »

The snubbed cap causes a clear ringing.

My favorite input caps right now are .47uf smallest size for some bass. 1-2.2if is fine too. I like Orange drops, but the Wima MKP10 was good too.

The ES caps were pretty good, but have issues with polarising or they more susceptible to some distortion up in the chain.

I have no issues with bass. But I'm not a junky for it.

The resistor dampens the wire resonation from PSU to amp board. My latest, that will be the kit, has a capacitor multiplier so it doesn't seem to need it.

ejfud · « **Reply #38 on:** 28 Jan 2015, 09:18 pm »

I'm getting g excited to hear your amp Salis!

Folsom · « **Reply #39 on:** 29 Jan 2015, 01:09 am »

Would you believe another amp is on the table?