Some Frequenty Asked Questions. (actually most of it I thought of myself)

How does it sound?

Oh the sound! It’s very transparent. Doesn’t have a strong character. For those looking for transparency in their system, this is highly recommended! However, if you are looking for a sweet sound, then I recommend the 5965 in a different configuration. Will post this on my Projects page later.

Why does it sound kind of “edgy” in my system?

A friend did describe my preamp as “edgy” too (though my tin ears can’t tell). Solder grid stopper resistor of 120-150 ohm on grid of both channels and it worked great!

I don’t like your power supply filter and would prefer 100H-100uF-100H-100uF.

Of course! This is a DIY project remember? So do it anyway you like. I opt for a low capacitance high inductance power supply filter circuit but you can do it anyway you like. You could build it as capacitor input power supply. No problemo.

I finished building it, and proceeded to power on without tubes…

Oh no! Don’t do that! Without tubes, the transformer is not being “loaded”. The voltage can get very high! If it gets higher than the voltage rating of your capacitor, your electrolytic cap might explode! Always power on with tubes installed.

I hooked it up to the rest of my system but it hums… can play music though.

Hum is good. It means you are almost there. (this doesn’t sound comforting heh?) Write to me and we’ll try to work out how to reduce hum.

I don’t like your choice of parts. I would prefer tantalum resistors, Black Gate capacitors, Jensen copper foil capacitors, silver wire, teflon socket…

Be sensible. Start off with something cheap and move on. The sound you get is a combination of the various “sounds” of all the parts you put in. Splurging on parts without knowing for sure how they will sound TOGETHER in a circuit is not very smart. Get it working first, then (if you wish) break your bank with all the audiophile parts in the world. Don’t be suprised if some of the expensive ones don’t suit your taste.

Your ground wire looks so puny. You are not macho at all.

Yikes! You are right. Definitely not macho at all. I was lazy. You could use a thicker gauge wire, or parallel a few strands to get a lower impedance ground.

Are you offering a kit?

I prefer to concentrate on just parts. Look, I have given the transformer winder info. (so no middle man charge here!) I have even given the wiring diagram, step-by-step. The rest is up to you. You can find someone in your area to do your chassis, to my (oops, your) liking. Time is scarce and for all my trouble asking someone to do the chassis etc, I will need to charge you. Definitely no more “value for money”.

I heard that running one tube for each channel sounds better than utilizing both triodes in one tube.

I haven’t tried this as the other tubes I have been familiar with are all run both channels in one glass but if you DIY it, you can do it any way you like. Do let me know how it sounds. If it really sounds better this way, everyone should know. On an unrelated note, thank God I’m not offering kits. Otherwise, can you imagine how much work I have to bear to have all chassis reworked?

I actually prefer integrated amps. Never like the idea of preamp-power amp.

Ditto here. But then everyone has his/her own opinion. And my way is no superior to your way, vice versa. If you use power hungry speakers, solid state power amps is a must without breaking the bank. Tube preamps offer the opportunity to get tube sound at a lower cost. Alternatively, use this preamp circuit as your CD player output stage!

How many 5687/6X4 do you expect to sell?

I’m not expecting to sell many. The whole idea of doing this is to show you that building tube amps (or preamps) is very simple. There’s nothing magical inside. There’s nothing to “tweak here and there otherwise it won’t work”. You know, that kind of nonsense some folks spew to fool you into thinking DIY tube amps is only for electrical engineers. Once you understand this and start your first DIY project, trust me, this is going to be your most rewarding journey.

Okay, will stop here. Let me know if you have more queries.

The post How to build your own tube preamp FAQ appeared first on diyparadise.

Since the day I put up the Simple 5687 preamp on my website, I have been
overwhelmed by the response! So many have approached me and so many have
initiated their rites to tube DIY! Some of their baptism of fire was easy, while
some had a bit more trouble, but overall, no one has yet written to me claiming
they don’t like the preamp. This is great!

Well, if you have built your 5687 preamp, write to me and I’ll put your work
here.

Waily, Ang Mo Kio, Singapore     Well done, Waily! Waily is using Marantz CD63, Roksan solid state power amp and Paradigm Studio Reference speakers. Waily can be reached at waily at yahoo dot com.

Hi Yeo,After weeks of tweaking, I finally concluded that those values that U used in the project is very very near to ideal(best) what a 5687 should sound. Maybe my preference for good sound is quite similar to yours, in expecting what a good, neutral sound on system should have. Or maybe my gear should match with this kind of sound.   Here I would like to kow tow to you as I presumed that u’ve probably tried up quite a number of different values/ config before concluding and sharing this project with us and other diy’ers.   Initially I thought that this humble preamp has’nt reach the full potential yet, hence the word TWEAK comes into my mind. But then, those original values definately has to stay in order for me to really enjoy all my favourite albums/cd. Of course, there is room for improvement, but does it really justify the total cost of the project, or the degree of improvement- branded coupling caps (hovland, multicaps, etc), black gate skz/wkz sound of music power caps, dact stepped attenuators, pure thicko silver hook up cable, lundahl or other expensive choke/ transformer, and much more parts. Ok, I might do that when I am very loaded and doesn’t feel the pain of thrashing/ keeping those that sound unsuitable to me.;-)   Remember the 100u+100u, I just took it off and in place back the 50u+50u. The smoothness, creamy voice has came back, dynamic is a bit slower – u can get to hear the singer voice extension very well. The 100u might sound much dynamic with Mohamad Ali punches in his fancy footwork and that of course, will very soon send u to K.O. (definately ngam those ah beng in honda civic with the windscreen wind down). One words, I can’t take it anymore. Out u go. The opposite of things happen with the 25u+25u, it makes everything slow motion and dull, lifeless.   Anyway, the 390ohm dubilier has found some use in this preamp..I put it in the grid resistor for fun and suprisingly it sound much better than the Riken but different values that I’ve tried (100,150,1K). I can safely said that this resistor ngam ngam roll off those tiring highs and the loss in sonic clarity is negligible. (of course, it cure my power amp shutdown too).   To summarise, the only difference my circuit to you is only this grid resistor, 250K ohm alps pot, some cheap, thick solid core copper hookup cable, S$15 per pair bronze female RCA from Well Audio, pair of Welwyn 20K for the plate(well), others is riken (well) and 1000u cerafine cathode caps that i found it brings more mid and lower bass than the 470u (who knows I might revert bacck to 470 in future??;-), and of course this will varies from system to system.

    Thanks for your input Waily! Well, the circuit has
been optimized by vt4c. I just muck around with the power supply. : ) That said,
glad you like it! I hope you’ll be encouraged to try more DIY projects in
future!

Thanks Mike for your endorsement! 

Xavier Goh, Petaling Jaya, Malaysia   Ha! Another Simple 5687 comes to the fore! I like this. Non-boutique parts at all! Okay, just one Black Gate cap but cheap/common parts everywhere. Well, you can still hear its beauty. This, to me, is the mark of a good design. Kudos to vt4c again. Congrats on a successful project!

Hi Yeo, All parts are non-audiophiles grade except cathode cap (blackgate). I will upgrade it with adding in another choke with FT cap (awaiting your supply). The sound was transparent & the mid was good compared with my existing SS preamp. Source from Marantz CD6000OSE, 5687 preamp, JVC 4-channel power amp & out from Revolver floor standing speaker. I would expect better sound with additional 10H choke & FT cap. The holes beside the transformer & choke are for this purposes. I am using DC filament supply for 5687 tubes & with additional resistor at the grid input. Thanks. BR, Xavier

 

 

 

Billy Florentino, a Filipino lost in Singapore   Well, well, well. This Simple 5687 has a more “modern” aesthetic feel. The handles and plumbing bobs do add a touch of “IKEA” to it. Ha ha! Well done Billy! Well done!

Hi Yeo, Finally, I finished my first ever project 5687 preamp. It’s pretty lovely sound. The look that matches the sound. The Look : Those cabinet handles makes it look very cool. The chokes, I sprayed black to match the chasis. The blue light makes it very high end. The Sound : First, I was bothered about the hummm although it can’t be heard when listening. It did improved when I did the star gounding. It’s true that this machine is very dynamic and fast. The vocal is also great after changing the cathode cap to 1000uF (thanks to Wally for this). The extension of the highs are amazing. There are a lot of little sounds that brings out with this preamp. Further Improvements : I know there still a lot of room for improvement like finding the right value for the grid resistor, DC filament supply, trying tung-sol 5687 etc… Thanks man for all your help.. More power to you.. Regards, Billy

 

 

Come on! If you have built this project, send your pics to me!

The post Update: Simple 5687-based preamp appeared first on diyparadise.

So you need help building your preamp/amp and have no one to turn to? Or is your Significant Other pestering you to build those Ultra Cool stuffs at diyparadise but you don’t even know which end of the soldering iron to hold?

Have no fret! ‘Cause help is here! The PowerPoint files below (with PDF versions as well) has not only helped many a DIYer cooked up their own version of Ultra Cool Audio, they have been extremely educational too. Not to mention just downright entertaining clicking them slide by slide….

Best part is, the info below is free for you to download! The schematics, layout and even wiring diagram are all given FREE! No expensive E-books nonsense! This sure beats some of my competitors asking you $$ to purchase their lousy manuals. And stupid meaningless instructions like “connect point A to point B”. : )

As I spent some hours to build all this, I’ll appreciate your token of appreciation. And also, a note informing me what would you like to see more from diyparadise.

PPT PDF How to build the Simple 5687 preamp

PPT PDF How to build the Simple EL84 amp

PPT PDF How to build the 5842 Grounded Grid Tube Gain Stage

Thanks to all those Really Cool DIYERS for the PDF conversion!

Recommended enclosure plans for Merrill DCA4 and DCA5.5 drivers. Enclosure design courtesy of our resident speaker guru, Gabriel. These are simpler designs, great for DIYers. The horn poses a challenge though… Watch out for more interesting designs in future!

DCA4 Wide Baffle

DCA4 Transmission Line

DCA5.5 Transmission Line

DCA5.5 Double Horn

DCA5.5 Tuned Box

Merrill DCA4 and DCA5.5 driver and TC025 specifications.

Merrill DCA4, DCA5.5 and TC025 specs

The post Downloads appeared first on diyparadise.

Simple 5687-based preamp

  Do you fancy a simple DIY project? So simple and so cost-effective that it gives you the most bang for the buck? And let’s stay away from popular (and hence expensive) audio tubes like 12AX7, 12AU7… Here’s 2 very simple linestage preamps. The first credit goes to Audio Note. It’s called the Audio Note M7 preamp. The second is a modification of it by KLANS resident DIY guru, Mr. vt4c. Here’s some reasons why this project is so mojo.   1. A very linear and inexpensive tube, the 5687. Some people question the pedigree of this tube. They are nuts. You can question Audio Note’s decision to use it in the quarter-million RM Ongaku or their best selling M7 preamp! : ) 2. Use of tube rectifier here. Yes! It just sounds better! 3. Some folks have used it to drive their mega-expensive solid state power amps and found that it improves the sound of their gear. At the price of this project (less than their interconnects), it’s a no-brainer. 4. It’s a simple enough project for you to cut your teeth on DIY. You can move on to greater things from here. 5. This is a really cheap project! I would estimate you could do this for less than RM250. That’s right. I love #4 as this project is a good/simple way for you to cut your teeth on DIY. Once you learn what works, and what doesn’t, once you learn the cost-effectiveness of DIY, you can fly! All right, which circuit? Here is Audio Note’s M7 preamp.   Here is vt4c’s M7 preamp. There’s actually a full write-up on The Star’s DIY Den but there’s no schematics there, so this should complement that page.

 

 

Other than the above, you need also the datasheet of 5687 and 6X4. If you need the 5687, 6X4 tubes, sockets, capacitors and tagboard, you can get from me, from this page. If you need to build the power transformer, this vendor here can get one done for you at a very good price. I have no affiliation with this winder, so there’s no middle-man charges here. Oh yeah, with end-bells as well.   Mr. Tan Tonsin Components 30, Argyll Road 10050 Penang Tel: 04-2644691 or 04-3703303 Fax: 04-2620169   Alternatively, you could also ask this vendor. I have more confidence with EKK as they flash test their transformers before handing over to you. Don’t be suprised by this as almost all the local transformer winders I know of DO NOT run this test. They (the transformers, not the people) are ugly though as they don’t come with end bells. Runs slightly hot but the voltages with load hasn’t failed my expectations.   Miss H’ng EKK Supreme Electronics 411 Jelutong Road 11600 Penang Tel: 04-282 2897/282 2855 Fax: 04-282 2855   Sorry, I haven’t tried other transformer winders. There’s one I tried but opinion has been mixed, so I’ll leave it as that.   A suitable power transformer specs will be 12.6V@2A, 6.3V@2A and 200-0-200V@100mA, for Audio Note’s circuit. This is, of course, just a guide. You can definitely steer away from this. You could even use a single 6.3V@4A heater for both 5687 and 6X4 tubes though this isn’t recommended. vt4c’s circuit specifies power trans of 350-0-350V@100mA, followed by 10H, 50uF, 10H, 50uF. Topology is shown below.   That’s all to it! Simple enough? Think you can wire a transformer, a few resistors, few cap and 2 tubes correctly? More information will be available on this page later.     Update on 6 January 2003: I’m back! I’m more than back! I built vt4c’s circuit but with my own power supply. Here’s the circuit:   I actually asked for the power transformer to be winded 350-0-350V but the winder got it wrong and gave me 330V only. Anyway, it still works out okay.   Damage: Signal circuitry

          Lesson learned from this project : Trust me, you’ll appreciate this later. This little project lays the path to DIY a simple power amp to go with this preamp. Okay, but thought you mentioned that this preamp will cost less than RM250 to build? Well, you COULD get it down that low. Try to minimize bulk in the power supply. Maybe you want to just use a simple CRC filter ala Audio Note’s circuit. You save 2 chokes. Instead of using the Alps volume pot, you could build a cheap stepped attenuator ala Bottlehead’s Sweet Whisper from this article. You could use Auricap 1uF 450V at RM32 each as well. There you go! I built it with whatever I have on hand though I’ll say the sound will change somewhat if you take out the bulk from the power supply. I like chokes and I’ll stick that in. Your milage may vary…   Coming soon! Photos and step-by-step (almost) tutorial on how to build this simple 5687 preamp.   Update on Jan 9, 2003: It’s ready! How to build your own tube preamp.   Update on Apr 6, 2003: Preamp update!.     diyparadise.com

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How to build your own tube preamp

Alright, I have introduced a few simple projects. Now, let me show you step-by-step (almost) how I built one. I’m refering to the circuit explained on 5687-based Simple Preamp. Schematics is repeated here.

Okay, before class begins, pre-requisite knowledge is:
1. You got to know your resistors and capacitors. Yes, if you can’t tell a resistor from a capacitor, ask knowledgeable friends or pay a visit to Jalan Pasar.
2. Know what is a choke and what is a transformer.
3. Directly related to 1 and 2. Know what the symbols mean on the schematics below.
4. Know how to solder.
5. Able to follow simple instructions. Once your preamp is singing, you can mod to your heart’s content, but for now, let’s follow instructions, okay?

Okay! Let’s start!

We begin by first drawing the layout on paper, how are we going to lay the components out. We need to decide where does signal come in, and where does it go out. For simplicity, I’m using a piece of metal, folded at the ends, so it forms a huge upper case ‘C’. Components will be layed on the top plate. Back plate holds RCA jacks and IEC socket. Front plate is left blank. Click on preamp picture to open up this power point file.

Okay, study time. Please go through the schematics, wiring drawing and tube base configuration in the ppt file. Print it out if you have to. Can you understand how is this preamp wired? It’s important to understand the ‘whys’ now. Please be accountable for every wire there!

If you now understand the wiring, then comes the implementation.

Step by step we’ll go…
The power transformer is specified as one primary and three secondary tappings. Primary is 240-0V and secondaries are 350-0-350V@100mA and two secondaries of 3.15-0-3.15V@2A. The 3.15-0-3.15V secondary is to provide 6.3V to the heaters but there is an option to use the ‘0’ tapping to either reference it to ground or reference it to some elevated voltage. You want to do this as there is a limit to the potential difference between tube cathode and heater. If you exceed this limit, unneccessary stress is placed on the tube and it’ll fail in a shorter lifetime. Thus, if your cathode sits at 100V, then it’s a good idea to reference your heater to ~100V. In this preamp, I have referenced both heaters for 5687 and 6X4 to ground as cathode of 5687 is only 5V and though cathode of 6X4 is at ~250V, the datasheet says that it can take up to 450V, so that’s okay. You can of course, choose to reference the heaters to some other voltage.

Boring eh? Well, you need some photos! Read on!
 

How to build your own tube preamp Part 2

If you have done your homework, you should understand how it’s wired up by now. Nevermind, here are some photos to help you.

You start by laying out the ground path. I used the same wire as the rest here, but you could opt for the better option of using thick copper, say awg 12. A good and cheap option is those copper rods used for gas welding, available from your local hardware store.

Here, the filament wires have been wired. This is simple as there’s only 2 tubes to consider. Note that I have wired 5687 heaters in PARALLEL. That means shorting pins 4 & 5 and wiring heater to 8 and 5. All filament ‘0’ tap refered to ground.

Next, I wired up the power supply section. It’s easy with this double capacitor. The pink wires are 350V. The red wire coming out from the capacitor is my B+. Note that I have wired in a resistor on the capacitor. This goes from +ve to Gnd. This is a bleeder resistor, meant to discharge your capacitor’s charge, lest it discharges on YOU with dire (some find it fun though) consequences. Aim to bleed about 1mA, so for B+ of ~280VDC, a bleeder resistor of 270kohm/2W is fine.

Ahem, signal circuitry. Remember signal circuitry consists of only 2 resistors? One on the plate and one on the cathode? Here the plate resistor is a paralled combo of two 20kohm 2W resistor to give me a 10kohm 4W resistor. The cathode resistor is 470ohm, paralleled with a 470uF electrolytic. It’s better if I could place the electrolytic lower but this makes it easier for modifications later. Being DIYers, this is important! Err, shown here is only signal circuitry for Left channel. Yellow wire is for filament heater.

While you are enjoying the pictures (and waiting eternally for them to download…), I have finished wiring up the other channel! Click for higher resolution (and more waiting) picture.

Okay, the urgency to power on is high now but hang on! First thing first, before you plug in your IEC cable, change the fuse in the plug to a lower current rating. I have 2A here as I can’t find 0.5A. Preamps don’t need high current so 0.5A is good enough. The last thing you want is for some fault to occur and your nicely built preamp go up to smoke just because the current isn’t high enough to break the 13A fuse. You have been forewarned!

Another use of a wire spool… This way, I could test the voltage points with a multimeter. It’s important to make sure voltages are correct within 10% tolerance before plugging into your system. Check with voltage points on the schematics.

Finito! Bathed in warm light as well! No wonder it sounds warm?

Plays music with the rest of the system. It worked right the first time!

There you have it! Hope you enjoyed the music, err the ride. Sorry for the long download time.

Done yet? Not yet!

How to build your own tube preamp Part 3

This is basically an options page.

The fun of this preamp doesn’t end with its completion. In fact the fun has just begun!

Even if you haven’t built this preamp, it’s good to take a look here to see the options ahead of you.

Power supply. You don’t have to follow my power supply circuit. I like chokes but it’s okay if you hate them. You can build it ala Audio Note or your own design. Your own design? Yeah, why not? It’s not that difficult. You can use Duncan Amp’s excellent Power Supply Designer. This simulator is highly recommended. Includes tube rectifier as well! Only snag is: you don’t know how it sounds. Anyway, with some idea what is the B+ needed, try different combinations and build different circuits and see which sounds better to you. There’s solid state diodes to play with, different tube rectifiers, capacitor input power supply filter, choke input…

Operating point. This 5687 has plate voltage of ~140V at 11mA. You can go higher, or lower with just a change of resistors here and there. You’ll get different sound, for better, for worse, try it and tell me!

Coupling capacitor. There are choices here rather than just the 0.1uF of Audio Note’s circuit or 0.47uF of vt4c’s circuit. The function of this capacitor is to block out DC voltage and allow AC signal to pass through. With the succeeding resistor to ground, it forms a high pass filter. Knowing the input impedance of your power amplifier that you are going to connect to this preamp helps you determine which coupling capacitor you can get by.

freq = 1/[2*pi*R*C]

Remember the above formula. Because taking R as input impedance of the subsequent stage, then… nah, this is too much to explain. Look at the table below. I have calculated the bass frequency cut-off using a combination of R and C. The R refers to input impedance of the next stage paralleled with your 1M resistor (which would come up pretty close to the next stage input resistance anyway). The C refers to coupling capacitor at output of the preamp.

What’s the point of knowing all this? So that you can be cheap! If your power amp has input impedance of 100kohm and you find coupling capacitor of 0.47uF to be too expensive, look at the table… this combo gives a cut-off of 3.39Hz. Well, if you don’t mind the cutoff at 7.23Hz, then you could use 0.1uF! After all, can your speakers produce THAT low? The point being 0.1uF is cheaper than 0.47uF of the same voltage rating. Okay, enough talk, try your hand at being ‘cheap’.

Resistors. Try any type you like! Carbon, metal, Kiwame, Holco, Vishay, Caddock, Chinese firecracker, cap parang… see I told you you could mod to your heart’s content. Just observe power ratings. Plate resistor of 10kohm has to be rated for at least 2.5W while you can get by with cathode resistor 470ohm of 1/2W.

Electrolytics. In the power supply, and cathode bypass of 5687. Use whatever you like.

Actually, my parts philosophy is very simple. Build it with whatever cheap components you have. Build it first, get it working first THEN mod it and substitute with whatever audiophile-approved, boutique, space-age, friends-claim-to-be-best-sounding part. Blindly using audiophile parts without regard is like cooking without knowing what spices you are using.

Wire. Yeah, some say solid core sounds better, some swear by stranded Litz, some prefer copper, some silver, Teflon insulated blah blah blah… Take your pick. For simplicity, I’m using cheap 600V solid core tinned copper of 22-23AWG. Try whatever you like. Just be sure to observe voltage ratings.

What next? How about a hint? This is a tube preamp… Yeah! Tubes! Here are some choices.

RCA, Tungsol (sold out), GE & Raytheon.

Tungsol, RCA, GE, Mullard (not avail) & Philips JAN.

Okay, I’ve done enough. It’s time to enjoy my music!

I said that too soon. Here is a FAQ page.

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