Q & A. Will it drive headphones etc?

[@MichaelBeeny]

MAKE MY DAY AND WATCH TO THE END OF THE VIDEO. IF YOU "LIKE" IT ALSO, MY LIFE WILL BE COMPLETE.

[@cschis]

I am so glad you are still posting videos. Your understanding and ability to explain things without any BS are very refreshing and enjoyable.

[@MichaelBeeny]

Thank you, that's very kind of you so say. I really appreciate it.

[@cschis]

@@MichaelBeeny@MichaelBeeny Sir, I usually don't comment, but you deserve some recognition, and I would be remiss if I didn't compliment you. Please keep up the channel and your efforts.

[@MichaelBeeny]

@@cschis I'm always very pleased to hear from my viewers, so do comment, it's the only way I know if people like that I do.

[@lamalandy]

Thanks for the interesting and instructive videos. I've never understood how back to back capacitors are equivalent to bipolar ones, could you share your understanding please? Perhaps it's because they leak when reversed, I don't know how each gets the correct polarity applied.

[@MichaelBeeny]

@@lamalandy I don't really know the theory, but it works. I must have been absent from collage when that was explained. I'm sure someone smarter than me will answer your question.

[@cobar5342]

The capacitor tip is great

[@el_arte]

Brilliant, Michael. Thank you for the update!

[@Qualitaetspruefer]

Thank you for all the details about this nice preamp!

[@ProtoDAC]

Your channel is great, Michael! Another spot on recommendation. diyAudio thread titled Clon C-3850 shows "at RMS -11.5 dBV THD is 0.0026% and THD+N is 0.015%". Mostly H2. Golden ears Beeny. Thank you so much.

[@MichaelBeeny]

I told you it was good, lol. Sadly, I cannot measure such low THD. Maybe if a rich uncle leaves me all his money, I can buy one! One reason I use high frequency square waves, the two tend to follow quite well. Ears, even older ones, are also great confirmation of the tests.

[@ProtoDAC]

These days it is not expensive at all. PC software called REW along with a USB interface (I have a secondhand Steinberg UR12) and decent signal generator is all that is needed.

[@Rowuk2024]

Well, mine is now breadboarded and I spent the first hour listening with my AKG-701. The "sound", well there is none! It is as neutral as can be. The bass is deep and extended with no bloom. Voices are very transparent and there is no sibilance added. The only issue is the high gain that you have addressed. I bought the assembled version so I have no parts layout and will have to search for resistor 11 to change it to around 1K.

[@MichaelBeeny]

I did tell you; it was a bit on the good side lol

[@marknielsen8977]

As always, great information. Thanks Michael.

[@terriludolf6101]

yeah, comments are open :-) Great Channel

[@pauldorman]

Thanks, Michael!

[@MichaelBeeny]

Good to see you here Paul.

[@pauldorman]

@@MichaelBeeny Wonderful to be learning from a fellow Kiwi! I really appreciate your pragmatic approach to picking the right components for the job. Few people can afford to go top-shelf every time, so it's great to see someone demonstrate that more affordable components can deliver excellent results, if you take the time to test as you go. In these challenging economic times it's reassuring that you can still get into electronics without breaking the bank!

[@MichaelBeeny]

@@pauldorman Thank you Paul, it's good to know at least a few Kiwis watch my channel. I hope you won't be devastated if I tell you, I'm not a real Kiwi. I've been in NZ 22 years now but I'm from UK. I'm still in training to be a real Kiwi. lol

[@pauldorman]

@@MichaelBeeny Oh that is a shame. I heard a rumour that you must have lived in New Zealand for twenty _three_ years before you're considered a real Kiwi 😆

[@sonhouse9636]

Hi and thanks, I tend to watch all your videos, they are very useful and nice to watch because you have a nice soul.

[@MichaelBeeny]

Thank you for your kind words. I don't know what to say!!

[@TRONMAGNUM2099]

Excellent video. Looking forward to the next video!

[@MichaelBeeny]

I'm working on it right now.

[@huntuscreation2904]

Very informative and useful video. Looking forward for the next video. Regards.

[@MichaelBeeny]

I'm also looking forward to my next video. I must get around to making it ASAP. lol

[@Jumoana]

You're goated content creator, please show more devices and tips especially for headphones

[@Peter_S_]

I love your videos and I really appreciate the engineering data you present. I was thinking of valve sound spectral envelopes as you muttered the word valve, but I was wondering more from the standpoint of driving a small output transformer of a few hundred ohms to make life easier on the output transistors and for the electric guitar world, driving an undersized transformer into saturation to intentionally distort. A lot of that "valve tonality" comes from parts beyond the actual valves. In the guitar case, playing with C5 is certainly in order; I plan to use a 12 position rotary switch there. Now to buy one of these kits. Cheers from Colorado, USA!

[@AA-pb2rz]

Thank you! We need more people like you.

[@MichaelBeeny]

I do hope not, one of me is enough for this world. Ask my wife. lol

[@AA-pb2rz]

@@MichaelBeeny 😄😄😄

[@bobbysparky4299]

Thank you for your time, effort and explanations. Well done young man!!!

[@MichaelBeeny]

Thank you, Bobby, been many years since I was called a YOUNG MAN. lol

[@olebjrklund8648]

Thank you for another great and educational video michael. Just love the way you present this and how you explain everything. Also a great pluss that you point out that good audio, does not have to come from equipment, you would need a big bank loan to be able to afford. Have a great weekend and coming week, and best regards to you and your loved ones.

[@MichaelBeeny]

Hi Ole, looks like you are working your way through my catalogue. Your always most welcome, it's good to see you still with me. Mike

[@Douglas_Blake_579]

Nicely done. A friend of mine used to refer to DC output on equipment as "Death Current". I think he was right.

[@MichaelBeeny]

Hi Douglas, good to see you here again. I have, so far never had an issue with DC. Maybe because I know the products I am connecting together.

[@Douglas_Blake_579]

@@MichaelBeeny Yep, one of the big advantages of DIY is that we know exactly what we're connecting together. Not always possible with consumer products. Good to see you posting new videos.

[@ryanchappell5962]

I love your humor so much. Talking about getting a bank loan to by an expensive capacitor 😅

[@MichaelBeeny]

It's sadly my British sense of humor Ryan I can see something funny in all aspects of life. Often gets me into trouble.

[@ryanchappell5962]

@@MichaelBeeny works for me! I laugh out loud when I watch your videos. Who would have thought I could learn about electrical engineering and laugh about it?

[@HiFiGardener]

Great video. I’m curious, have you ever added a source selector to this preamp to allow for multiple selectable inputs?

[@MichaelBeeny]

For my set up, no! Everything goes via my DAC and PC. So, I have no use for such a switch. It would be extra simple to add a 3 way double pole switch, it's as simple as that. A ready-made solution is available. Slightly different circuit but based on the same design. I made a video on it some 3/4 years ago. See it here. kzbin.info/www/bejne/jX3JZpRtp8aDgNEsi=qJrNQkMGEdvgaJsI

[@cobar5342]

Thank you Michael. I really appreciate your videos

[@MichaelBeeny]

Thankyou Cobar, good to see you here again, much appreciated.

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

really nice i would like to see next video ! 😅

[@MichaelBeeny]

I can't wait to see it either. I must get on with it. lol

[@Чемы]

Спасибо вам что Вы делитесь с нами своим опытом и знанием ! У Вас интересный канал , всего Вам доброго!

[@MichaelBeeny]

Thank you for your kind comments, they are really appreciated.

[@stevesmyth4982]

The low output impedance of the preamp is the reason why I didn't use screened wire between the PCB and the phono sockets.

[@ScottGrammer]

Great video!

[@MichaelBeeny]

Thankyou Scott, most appreciated.

[@garethbryneithin]

Thank you for your very informative videos. Have you made the video telling us how to make use of TEC 2-4823WI?

[@MichaelBeeny]

Not yet, still in the testing phase. So much going on at present. Preamp design, testing, more testing. getting old lol. I'm refurbishing a pair of KEF 104/2 speakers.

[@oguzaydin7482]

Hi Michael, thank you for these excellent videos, I have learned a lot from you. I still have some questions for this preamp, I hope you can make a technical video to share your comments: 1. As far as I can see, this preamp is just an opamp (gain) with a discrete buffer stage. While most of the power amplifiers have already had internal input buffers, a simple opamp should be enough to drive any power amplifier. Why do you need such buffer stage? 2. If you really need a buffer, there are good buffer ICs like LME49600,etc. Why not simply put such buffer IC in opamp's feedback loop? 3. Caps, especially large bipolar electrolytic caps decrease the detail in the sound. I tried some BP caps including MUSE, I really don't like them and I finally decided to use film caps. If you show us a good preamplifier with DC servo circuit, it would be great.

[@mfr58]

The O/P buffer is to drive cables without loss.....on the way to the power amp....

[@oguzaydin7482]

@@mfr58 Okay, let's assume you are right, what about the cables between preamplifier and different sources (DAC,CD player,etc) Won't they need such buffer? The audio passes through the cable to reach the preamplifier before going to the power amplifier, right? Normally, the distance between the preamplifier and power amplifier is short, my cable is just 30 cm. Opamps, even good old 5532 is capable of driving capacitive loads especially if there is gain. There are also methods of isolating the opamps from the capacitive loads like putting a small resistor in serial. The purpose of this buffer is just sinking high current into low impedance load (like an headphone). You can prefer an buffer, okay, I respect your idea but it comes to my next question: What is so special of this circuit so that it is better than buffer ICs? LME49600 is just 6.5 USD, BUF 634 is even cheaper. Both are excellent buffers and cheap enough. You really don't need to deal with this circuit unless it is better than these ICs. That was what I was asking Micheal to advise us.

[@KGrasso89]

Hi Michael, whats the line output voltage of this preamp?

[@SteveMarr-oe4dr]

Hi Michael, good to see you looking full of beans again. You have inspired me to build an integrated amplifier using this pre amp and the TDA7293 amplifier modules. I am also adding a phono RIAA stage. I am pretty handy with a soldering iron and am learning the theory. A couple of questions / suggestions. What gain would you use on the pre amp in this combination, I will use line level and the phono input? Is there any advantage in thermally coupling the pairs of transistors on the pre amp? A tutorial on the use, installation and termination of screened cables inside the amplifier, would be useful. All the best.

[@MichaelBeeny]

Hi Steve, don't bother messing with the transistors, it won't make any difference. They don't even get warm. As for the gain setting, I cannot really answer that simply because I don't know the sensitivities of your proposed connected products. The amp and preamp work very well together. Ron and I do use this combo, we love it. From the list, try the mid gain setting as a start point.

[@SteveMarr-oe4dr]

Thanks Michael I'll start with 390ohm and see how it goes. I've ordered most of the parts apart from the transformer, I'm repurposing a cabinet and size is coming into play.

[@yellow_noise3]

Hi Michael. I love your videos. I bought already 2 kits to DIY. And I have a question. Transistors provided in the kit bc550c and bc 560c have significant differet hfe. About 100 difference. I saw in schematic that design should compensate such a discrepancy but wanted to be sure, so please tell us - does it really matter? It is problem because bc550/560 series are obsolete and (especially 560c) hard to find, thus I wanted to know if using transistors supplied in the kit with such large hfe discrepancy is not making sound deterioration....

[@MichaelBeeny]

The gains on NPN and PNP are often different. So far, nobody has reported any issues. Test for DC offset before use. Should be around the 1-3mV.

[@ruyborborema3813]

Thak you Mr Michael. I appreciate yours videos so much, all of them. I would like know your opinion about shunt sttepers attenuators as a pot? who´s the more usefull?

[@MichaelBeeny]

While they are possibly more accurate in comparisons to a standard pot, personally I don't like the step action of such a switch. I prefer a smooth rotation. Clearly, they cannot sound any better because at the end of the day they are still resistors. Watch this space. We are working on an active volume control and preamp. Loosely based on circuits from Cambridge Audio and Mr. Baxandall.

[@MichaelBeeny]

Like at bit of fun?? kzbin.info/www/bejne/qJe6oYuMiKybpZYsi=jVH5wPRMMfNtr5X0 Hope you get it!

[@antonioandres25]

Hi, Mr Michael. My DC offset, i think, is a little high, 4 y 4.5 mv. How can i down it ??? THANKS

[@robh9079]

Regarding bass roll off for DC blocking output cap - would the cut-off freq depend on the power amp inZ? and if this is high could a lower value cap be used? (e.g. quite a few of the class Ds are inZ c. 100k...)

[@MichaelBeeny]

Yes robh, that's 100%. I suggested that value because I have no idea which amplifier or other equipment someone might connect this too. Secondly, few people would be able to work these things out. I thought it better to be safe than someone feel disappointed by having no bass.

[@suncani]

Dear Mr. Michael, kindly would you share a link of that 15 V AC power transformer. I do not know which one to choose , because some of them have only two output wires. So I am kind of lost. Aliexpress and Ebay have bunch of them, but I don't know which one to pick. Thank you very much dear Mr. Michael. God bless. Best regards from Bosnia. Sani

[@MichaelBeeny]

The transformer I used was one I had in my parts box. If you buy from E Bay try this link. Note I have not used this place personally, use as a guild only. www.ebay.com/itm/393536038579?_skw=transformer&itmmeta=01J7S5A34TM1MF1YBZWT5QQNBB&hash=item5ba09366b3:g:--kAAOSwRn1hQq94 The spec is Primary to suit YOUR mains voltage. Secondary is 2 watts @15/0/15volts Must be a 3 wire connection, cannot be 2 wire. These are very low cost but good. A wide choice to choose from. Buy local if you can.

[@suncani]

I can not thank you enough Mr. Michael. I will give it a try. God bless. Sani ❤

[@antoniojoseandreomartinez9710]

👍♥️🫂

[@AntonioRuiz-ji9yj]

Hola , por favor podria enseñar como conectar cableado de potenciometro ? Gracias

[@sulochanas5453]

best sound quality audio ic can u tel me sir

[@MichaelBeeny]

It depends on the application. The NE5532 is a good low cost ic The LM4562 (LME4970) has a faster rise time.

[@gamiwv]

I had to go to the first video of the "series" to see again the schema for understand what about you are talking to. Please put the schema of the preamplifier in the video

[@MichaelBeeny]

Good point, but each time you view and see the adverts I make 0.001 cent. I'm saving up for a cup of coffee lol

[@ryanchappell5962]

I know you don’t recommend using this to drive a loudspeaker for one millisecond but it seems like it would be just fine if I do it for only one millisecond.

[@MichaelBeeny]

Hi Ryan, maybe it would be OK for a little longer than 1millisecond. For some reason I found the test really funny, I could not stop laughing! I had to edit out my hysterics. Must be an age thing, little things amuse me!

[@ryanchappell5962]

@@MichaelBeeny I think it’s pretty funny too! You were being very naughty with those transistors! It sounded surprisingly good too.

[@jarlesagheim9710]

Hello. I really like your videos. Can you do an 30 watt ish class an amplifier?

[@MichaelBeeny]

I'm very pleased you like my channel. Sadly, I cannot help you. I don't see the point of class A. Afterall, the only real difference is high bias to get rid of crossover distortion. These days crossover is not an issue, on suitably biased class AB. If you cannot see it on a distortion trace, you certainly cannot hear it. You are just spending money on very large heatsinks, big transformers and a high electricity bill. You are better off with a more powerful amplifier that will offer better dynamic range.

[@yellow_noise3]

Hello. There is Musical Fidelity A1 clone on ali, nice build with enclosure for little $, if you need more power, consider Dartzeel 108NHB clone for ca 400$, super power 150W amp which delivers first watts in pure class A. If you are DIY guy, will never go wrong with JLH 1969 pure class A clone, available ther for ridiculous little money. Not 30W though, but ca 10W. Should be good for most speakers... I bought this kit (come also as soldered one), and will be matching it with this preamp. Interesting what comes out....

[@MichaelBeeny]

@@yellow_noise3 I don't see the point of class A. Afterall, the only real difference is high bias to get rid of crossover distortion. These days crossover is not an issue, on suitably biased class AB. If you cannot see it on a distortion trace, you certainly cannot hear it. You are just spending money on very large heatsinks, big transformers and a high electricity bill. You are better off with a more powerful amplifier that will offer better dynamic range. I would love to test all the amplifiers you suggested but sadly I'm just a pensioner. These amplifiers cost money which I don't have. I have enough amplifiers to use in every room in the house. Maybe someone rich will die and leave me all their money. I won't hold my breath waiting lol. Thanks for writing.

[@jarlesagheim9710]

@@MichaelBeeny hello. Yes, very good channel. Please make more videos. Class an amplifier, yes, they are now kind of redundant, and yes, you can’t hear crossover distortion. Is just nostalgic reasons for me liking them. But in the future, if you make a video of a cool “” amplifier, I would definitely watch it, and make the amplifier. I made the accuphase preamplifier you made some videos about, and it’s great. Great explanation, and it’s really helpful and really cool of you to make videos like this. So thank you for an excellent video.

[@jarlesagheim9710]

@@yellow_noise3thank you for the tips. I will look at the Ali products you mentioned. 👍

[@phdoumeng]

Use Muse BP 100uF 50v ans you're ok

[@a-job7276]

Hi, for the DC issue, a Servo-DC could be implemented to remove the AC coupling capacitors. You could also use a composite headphone amp (I think that's what it's called) A preamp and a buffer, OPA1602 & TPA6120A. You also have to take into account the balanced topology and that it has double the THD because each "side" works at half the load impedance (headphone). Another important point is to make an impedance adapter / attenuator, to be able to lower the background noise and be able to increase the input volume more, it is very typical not to be able to increase more than 15% in the amp, it depends on the sensitivity of the headphone or IEM. There are online calculators for balanced H-bridge attenuators.

[@MichaelBeeny]

We have no audible noise on this preamp. Even at maximum gain. Regarding DC offset. It's typically 1-3mV and that's with unmatched transistors.

[@a-job7276]

@@MichaelBeeny I imagine the price of matched transistors or ICs that come with multiple transistors is higher, but how much? Wouldn't it be worth it?

[@MichaelBeeny]

@@a-job7276 I have to ask the question Why bother? You have seen the results without matching, how much better could it get?