Dual TDA7293. Full circuit diagram, modifications.

[@ronschauer839]

Hi Mike. You are *most welcome* and "thanks for the thanks". 🙂 We are certainly enjoying a pair of these dual 7293 boards in our den AV amplifier. They are being driven by a low impedance preamp. I cannot describe how very much of an improvement these boards are over the NAP250 (clone) boards that it was using before. Night and day better..! I should add add that you might consider reducing the 7293 board's gain slightly by changing the R4 value to something more like 470 ohms. This will have the effect of boosting bass response because of the way the C2/C3/C4 combination interacts with R4. *Thank you* for finding these boards and your kind efforts and patience as well. 👍👍

[@ericmacey1026]

I do enjoy listening to your talks on audio projects, I'm like you, building and redesigning electronic stuff and keeping out of mischief and driving the missus up the wall. I'm really glad you are well enough to carry on (regardless) and we look forward to any projects you deem fit to show us. Thank You.

[@MichaelBeeny]

Thankyou Eric.

[@iourzzz]

Thank you very much for all the information and the inspiration! Can not stop watching your videos!

[@MichaelBeeny]

Thank you Roman for your kind words, most appreciated.

[@darrellphillips8361]

Always enjoy your videos regardless if your channel is open or closed or somewhere in between.

[@MichaelBeeny]

I wish I knew Darrell. When I feel unwell, I really want to close the channel. Then I get, to my surprise and delight, so many kind and wonderful, comments, letters and e mails. I am inspired to carry on. I find it hard to believe people are talking about me.

[@ryansupak3639]

Hear hear. I love your demeanor and I always learn something from your videos. I hope this note finds you in good health and good spirits.

[@bertstraathof2315]

Thank you mr. Beeny for a fine update on the dual TDA7293. Fine to hear from you again.

[@SaratogaNovaScotia]

I very much enjoy your videos (especially this one 😊). Thanks for the great detail and walkthrough

[@MichaelBeeny]

Thank you for your kind words, much appreciated.

[@michaellundsrensen2292]

Thanks Michael, you are just the best amp teacher!

[@KP-nd3bx]

Nice to see you in good condition. Keep on teaching.

[@michaelspafford5936]

Im glad to see you back Michael. Just watched a vid from Michael dranfield about these fake chips. Maybe worth a look. The tell tale sign is if your meter is in continuity mode. You should get OL from tab to last pin. Fake chips could read anything from nearly nothing to a few hundred K. Also re printed. Thanks

[@MichaelBeeny]

Alot of Michaels here lol. Yes, I do watch Michael Dranfield. I'm quite sure these are real. Performance and price suggest that. You do see them on E Bay for a couple of $$. People are fooling themselves at this price.

[@billkalina3089]

Thank you for that info Mike! You know, I just may order these and do the mods. If it sounds as good as you claim, I may just make it my new centrepiece, coupled with a wicked pair of bookshelf speakers. And all of the others can be conversation pieces. Be well my friend!

[@MichaelBeeny]

Hi Bill, as supplied it's very good but the mods just add the cream to the project. Let, me know what you think! I'm sure you will love them. I've not received ANY negative comments so far.

[@billkalina3089]

I will let you know. Hmmmm, which amplifier case to cannibalize?

[@MichaelBeeny]

lol. That is always a hard decision.@@billkalina3089

[@nakfan]

Great 👍 Thanks for the tips and tricks.

[@garygranato9164]

thanks for the vid , nice to see your looking well

[@TT-it9gg]

Love to see your video. Thank you!

[@ford1546]

A big problem I have experienced with all op amp ic. is that they ruin the sound. There is always less detail in bright frequencies and the sound becomes less detailed. I use Alps potentiometer and different pre-amplifier pcb with and without capacitor on input and output. The sound always gets worse! with the preamplifier in the chain!

[@MichaelBeeny]

I will be looking at 2 preamps in a few weeks' time. As they say...STAY TUNED. Re chip amps, I promise you will NOT be disappointed with this one. It's now in use daily. I love it.

[@ford1546]

@@MichaelBeeny I think that it is the same which preamplifier card you buy from ebay or aliexpress that is based on one or more op amp ic. will have the same problem since most are made pretty much the same. It is not difficult to hear the problem but not easy either, somewhere in between. I tried my NAIM NAP250 clone card from ebay which doesn't have the best sound quality, together with my preamplifier and the sound was a little lacking in detail and a little darker in the brighter treble. A bit of the problem was the preamplifier i have. I tried another preamplifier card without a capacitor in the sound way with the same result. Without a preamplifier but only with a potentiometer, the problem was gone. I use 50k blue alps potetiometer from ebay and input relay card. Now I have ordered the OPA1612 op amp ic. which is mounted on the pcb. card adapter since you only get this ic. in surface-mounted version. What is your opinion on this?

[@DustinWatts]

We should make/design our own board with all the modifications, and make it Open Source! I'm in :)

[@MichaelBeeny]

Hi Dustin, a few years ago that could well be a great idea. The thought of dealing with the tax office, postal system, fills my brain with horror. Been there, done that. Sadly, all I think of these days is I'm I warm, is it time for a cuppa T. Nothing to stop you doing something like it yourself of course.

[@andymouse]

Definitely !

[@DustinWatts]

@@MichaelBeeny No nothing stops me off course :) Although things might get delayed because off lack of time.

[@360MIX]

okay... channel is not closed.... so let's change it to OPEN... as videos are popping up since closed.. and makes no reason so say CLOSED when its still active.... and WE LOVE your videos mr. beeny....

[@MichaelBeeny]

It's become a bit of an in joke really. I really did not think I would ever make videos again. My health, heart disease, has put a great strain on my life. However, I do have a few good days now and again and do my best to make the odd video. How long this will last, I really don't know.

[@zoelong6021]

Technically, the channel closes until it opens again

[@MichaelBeeny]

A good answer Zoe. Technically you are 100% correct.@@zoelong6021

[@alunroberts1439]

Brilliant presentation from UK 2E1GZQ

[@MichaelBeeny]

Thankyou Alun.

[@Bengal20]

Mr Beeny, I have another question, hope that I don't bother you too much: Can I use speaker amp like the one in the video to power low impedance planar magnetic headphone like Hifiman Edition XS - 18 Ohm or Verum One - 8 Ohm? The power of these speaker amp is very big for headphone, expecially at low impedance load, but it's not a big problem because we can use them with small volume. But as I know, the output impedance of speaker amps is much higher than typical headphone amps. It will cause noise for headphone. Am I right? Is there any solution to use speaker amp to power headphone without hearing noise?

[@MichaelBeeny]

Most integrated amplifiers that have a headphone socket are fed from the speaker feed via a resistor network to limit power which could damage both the headphones and you're hearing. Some special headphones that require a higher output would be fed directly from the speaker outputs. I don't know these headphones so you might need to experiment with different values. Use 1-watt resistors.

[@Bengal20]

@@MichaelBeeny thank you very much, Mr Beeny! 😁👍

[@ronschauer839]

I would think that these boards would work extremely well for driving low impedance headphones. However, as Mike said, you really should have a resistor in series with each output. Something in the range of 16 to 47 ohms per channel perhaps (as he also said- you'll need to experiment a bit). They should of course be power resistors (such as 1 watt to 3 watts). There is something else I might suggest doing that I have done on mine- .Change the value of R4 from its 150 ohm as-shipped value to something like 470 ohms. This will reduce the gain and also will increase the bass response significantly because of the way R4 interacts with the C2,3,4 combination. Don't forget to change C12 (bootstrap capacitor) to at least 47uF, or even 100uF. Otherwise the bootstrap rails will run out of voltage and sag at lower frequencies. Again, I think that these should make great low-impedance headphone amplifiers because they should easily drive any headphones including rather low impedance ones such as you mentioned.

[@Bengal20]

@@ronschauer839 the details that you've written is very useful! Thank you very much! 😁👍 I'll give feedback after finishing this project

[@PaulMorganRyder]

Can I ask you where I can find the circuit diagram? I Love your videos.

[@MichaelBeeny]

My friend Ron reverse engineered it. It is not published anywhere else to my knowledge. Feel free to copy it from my video if you wish.

[@zoelong6021]

Am a keen follower of the channel and have built most of the recommendations - so naturally did this one too. Power was as demonstrated 85W - flat response curve as well. But that's how good it gets. The noise was a good 0.005% at 1W but got worse to 0.012% as full power. I still challenge Michael to build the symasym 5-3. +90W at 0.007% thd+n for cheaper. In actual fact - give me an address and i will post the board to you for testing - that's how sure I am?

[@MichaelBeeny]

Hi Zoe, at present I am not looking for extra projects to build (health issues etc) but does look good on paper. How does it sound in comparison to the 7293 which is currently my favorite.

[@zoelong6021]

Take it easy - everyday is a gift. I am by no means an audiophile buff...which is why your valued opinion on what sounds better would be welcome. @@MichaelBeeny

[@billkalina3089]

I have constructed the Symasym 5.3., the LJM12, the LM3886 and the TDA7294. If you asked me be honest, which sounds best, I would say TDA7294 by a nose. More experimentation is needed however.

[@zoenagy9458]

please check out LM1875 cascading with OPA, 10x better THD figures

[@carlfranz6805]

Anyone able to find this board recently. I'm afraid I cannot. 😢

[@new-kids-on-the-block]

Thanks fore the video Can you make a video from a streamer or dac diy? Im bilding a pi base streamer end tda1541a dac circuit board Like 2 see you bild 1 😁

[@MichaelBeeny]

Sorry, not really into streaming and DACs I don't have much knowledge of such products.

[@grandalexander]

Wrong . Like before watching.

[@MichaelBeeny]

I don't understand your comment. Please explain.

[@grandalexander]

​@@MichaelBeeny It was a compliment that you said in the start of the video abou t to turn of. Sory for the inconvenience .

[@MichaelBeeny]

Thank you, getting old now, I do miss things at times lol@@grandalexander