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.
30, Argyll Road 10050 Penang
Tel: 04-2644691 or 04-3703303
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.
EKK Supreme Electronics
411 Jelutong Road
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:
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.
"Rich, warm tone" is a consequence of elevated mid-bass response, attenuated high-frequency response, or both. Tube amplifiers have a reputation for warm sound because they tend to have high output impedances (low damping factors), which can cause their frequency responses to bump up at the connected speaker's bass resonance frequency. (I think the fact that they glow in the dark also has an influence, but ...) You can get the same result with a tone control or equalizer, however.
I found a book at the library from the author W.E Butterworth with the title of Hi-Fi.
It was a good overview of the "Music Reproduction" industry until the mid 1970's. The thing I came away with was how competitive the industry was right from the beginning at the turn of the century and how it stayed that way.
It did give me some incentive to listen to some vinyl and see what all the fuss is about. From the authors point of view tape seemed like a far superior medium.
12-25-09: Tpreaves Buying within the same mfg. line takes all the guesswork out of equipment matching.They spend hundreds of thousands of dollars on R&D to insure their equipment works together.I'm not in any way saying mix and match does not work,just stating the obvious. Tpreaves (System | Threads | Answers | This Thread)
12-25-09: Mitch2 Ok, I am going to borrow from Wikipedia, and also add some things I have found to work.
If you think of your preamp as a source, and your power amp as a load, then you may consider that maximum power transfer can occur when the output impedance of the preamp matches the input impedance of the power amp. However, in high fidelity audio, it is typically considered optimum to have a source with low impedance connected to a load with high impedance. In that case, the power that can pass through the connection is limited by the higher impedance (so power transfer is not maximum), but the electrical voltage transfer is higher and less prone to corruption than if the impedances had been matched.
When matching preamps to power amps, a general rule of thumb is for the load (amp) input impedance to be at least 10 times higher than the source (preamp) output impedance to provide a suitably flat frequency response. Many prefer using a minimum ratio closer to 20 to 1, or having an amp with input impedance 20 times or more greater than the preamp output impedance.
With solid state preamps, this is generally not a problem since most have output impedance of only a few hundred ohms or less, while most SS amps have input impedance of at least 10K ohms. However, you must pay much closer attention when trying to match tubed preamps to SS amps, since many tubed preamps have an output impedance of several thousand ohms or greater. Another thing to watch is how the output impedance spec is reported, since it is sometimes limited to a measurement at a given frequency such as 1K Hz, while the actual output impedance may vary with frequency. It is not unusual for the output impedance of tubed preamps to rise significantly as the signal approaches a lower frequency of 20 Hz, because of the size of coupling capacitors used in the preamp. In these cases, a low frequency roll off can occur whereby, for the same power output, the lower frequencies drop in output compared to the rest of the frequency range, resulting in a loss of deep bass.
The good news is that most tubed amps have sufficiently high input impedance to allow the use of most preamps, tubed or SS. Also, for SS power amps, input impedances of around 50K ohms and above are common and these amps should work well with the vast majority of tubed and SS preamps.
Only a couple of manufacturers make SS amps with input impedances of 10K ohms (e.g., McCormack DNA500), and a couple (such as Pass) make SS amps with input impedance of 20K ohms. These lower impedance amps would require careful matching with tubed preamps. If you are trying to match a preamp with one of these lower input impedance amps, you should try to find information on your preamp's output impedance throughout the entire frequency range. Some manufacturer's report this information and some do not. A good source is a Stereophile review, since JA commonly provides the information as part of his measurements. Others will likely have good suggestions I have missed, but this information should give you a good starting point. Mitch2 (System | Threads | Answers | This Thread)
Behringer makes three similar products with very similar names. This one - the UCA202 - provides line level RCA stereo inputs and line level RCA stereo outputs, a S/PDIF optical output, and a 1/8th inch stereo headphone output with a dedicated level control. There is also a small switch which turns the output monitor on and off (so the audio output doesn't interfere with your headphone listening).
The UFO202 includes a turntable pre-amp and a ground. The 222 is identical to the UFO202, but it has a snazzy red cover. To add to the confusion there is an identical UCA202 on Amazon for $10 more. God knows why.
I bought this to replace the similar Alesis in/out unit. The Alesis sounded dim, and the input volume control crapped out after four days - one channel was 6dB lower than the other. I sent it back.
Based on using the UCA202 constantly for a week, here is my assessment:
THE BODY - it is well designed, well thought-out, and well made. It's plastic, but is solidly made. (I wish it had that snazzy red body, though.) I like how the headphone volume control is recessed. I like how the connectors are all gold-plated (unlike the Alesis). I like the strong strain relief on the USB cord (unlike the Alesis). I like the reassuring LED that tells me it is connected to my computer. I like the way the labels are carved into the faceplate - no paint to rub off. I like having an optical digital output. I like the way it is small enough to take along with a laptop. (Gosh. I wish I had a laptop!)
THE SOUND - In short, it is fine. My cassettes go right from my premium Nakamichi deck into the computer, I edit the sound and bake a CD from the edit. And I get to bypass the cruddy soundcard in my old Dell (which has the sound quality and signal-to-noise of a six-transistor radio). The limiting factor is the cassette itself - not the analog-to-digital converter in the 202.
BTW - I compared two identical classical music recordings made with the Alesis and the UCA202. It was not even close - the Behringer was MUCH clearer and cleaner. I actually erased all the Alesis recordings and redid them through the Behringer, despite all the extra hours it cost me. The difference was THAT big.
I am not able to run the 202 directly through my big stereo rig, but it sounds pretty damn good on my $80 Grado headphones. It may not be the ultimate in audio refinement, but it is far more than adequate. For $30 I am a very happy audiophile. UPDATE - It is now plugged into a T-amp and good speakers and it sounds GREAT! UPDATE #2 - The 202 doesn't always sound good with cheap low-impedance headphone. See the end of this review.
I have looked long and hard at this product category - the next better unit up the food chain is the Cakewalk UA-1G USB Audio Interface for $90. The rest of the products at that price range ($100-200) include mic inputs, guitar inputs, multiple line inputs, mixers and other things I do not need. And the converters are about the same quality as the Cakewalk's.
Several devices will output your computer sound into RCA jacks, but this is one of the only ones that INPUT sound into your computer via RCA jacks. If you want to input (and edit and burn) cassettes, this is your baby! If you want to input LPs you either need a separate phono pre-amp or you go with the Behringer UFO202, which has one built-in. (I have not used it, so I can't comment on it, but Behringer seems to know what they are doing).
I'd give the USC 202 5 stars, but ....
THE INSTRUCTIONS - They stink. They go off on tangents about other Behringer products you don't need. They do not mention that the speaker in the diagram is a powered speaker. They do not explain that otherwise you need an amplifier to power your speakers.
They absolutely do NOT explain how you have to change some parameters in your Windows XP Control Panel. Or what those parameters are. They do not explain that you have to set up your computer's audio recording program (such as Audacity) to input and output through the USB connection. Figuring out all that jazz took me HOURS of research (though it takes only a few minutes to do).
That's one star down for pissing me off and delaying me two entire days. Unless you are willing to make a toll call, you reach Behringer tech support via email from their website. It takes a day or two to get an answer, but they are friendly and helpful and honest.
THE SOFTWARE - If you read the description, Behringer offers you "tons" of free computer software for your audio files. But don't think you will get some CD-ROM discs. It turns out that you have to download all three from different websites - and you have always been able to download them for free without buying any Behringer products. That's not dishonest or immoral, but it IS skeezy.
I'm a very happy camper with this product. If anything changes after a few months, I'll let you all know.
UPDATE - One year in and everything is still just fine. Now that I figured out how to set it up (with help from a Behringer tech guy), I'd give it 5 stars for sound. But I won't because I had to email them to make it work.
BTW - Please see my answer to the first comment for details about setup.
UPDATE #2 - Everything is still working fine, but I found out some new information.
1) The $90-200 devices that input audio into your computer don't actually sound any better than this device. But they come with inputs for mics, guitars, keyboards, guitars and the like. So if that's what you want to do, buy one of them. But if you already own a mixer that does not have a USB connector, just plug that mixer into this device and get on with your recording.
2) A professional audio engineer, NwAvGuy, has measured the 202 to be extremely flat and the noise level to be below audibility. He thought the build quality was good and the electronic circuit implementation was superb. He even liked the cheap headphone volume control. His bottom line: "the Behringer UCA202 line outputs measure very well even for a more expensive DAC."
But he notes that the headphone output only works well with high impedance headphones (like a pro would use). Cheap consumer phones that run at 16 or 32 ohms don't sound so good. I have pro phones, so I never noticed it. He'll tell you all about it.
NwAvGuy UPDATE - Apparently, Amazon will not let me link to the review. So put "NwAvGuy Behringer" into Google and click on "NwAvGuy: Behringer UCA202 Review", and "NwAvGuy: UCA202 DAC Take 2" for his follow-up.
There are still relatively few Linux music players that support bit perfect output. I've used a few that will support it, and they work well. Examples include deadbeef, Quodlibet and Clementine. I've not tried mpd yet, but it supports bit perfect output as well.
The trick is to bypass Pulse Audio and and have the music player output direct to ALSA. This thread explains how to do it:
I also output from my laptop running Linux to a USB DAC, and then to my amp. As long as the outboard DAC does not require proprietary drivers, the DAC is plug and play under Linux Mint and many other distros. I've used the Furutech GT-40 ang the Antelope Zodiac, both with good results.