6bx7 tube amplifier
Imaging is particularly good — I make much greater use of my headphones than ever before! Hum is low and unintrusive. I have used 60 ohm and ohm headphones with this amp. The amp is designed also to drive an efficient pair of 8 ohm loudspeakers. If you do build it, please let me know how you get on — ideas for improvement are always welcome! Figure 1.
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Tube Guitar Amplifiers Volume 2: How to Repair, Modify & Build Guitar Amps (Paperback)
Imaging is particularly good — I make much greater use of my headphones than ever before! Hum is low and unintrusive. I have used 60 ohm and ohm headphones with this amp. The amp is designed also to drive an efficient pair of 8 ohm loudspeakers. If you do build it, please let me know how you get on — ideas for improvement are always welcome! Figure 1. Figure 1 shows the amplifier schematic for one channel.
The output stage runs at 32mA, V, i. The amp was designed to work with 8 ohm loudspeakers. Nearly all loudspeaker drive units I have encountered have a nominal impedance of 8 ohms — of course this varies with frequency by a few ohms.
When driving headphones, the audio output transformer must be shunted with a ohm resistor Ro to present the correct load to the transformer secondary. The shunt allows higher impedance headphones to be used. Remove the shunt add a switch to take it out of the circuit when driving loudspeakers. A wide range of headphone impedances can be used with this amplifier because of its low impedance output.
However, with the ohm shunt, there is still plenty of power. Figure 2. Output tranformer is a home-made 2kR using dual isolated bobbin for safety. Primary: t of 32g; Secondary: 45t of 22g. I used a 20VA transformer kit to source the laminations and bobbin.
Everything you need to make all the transformers can be obtained from Maplin Electronics by mail order. From the catalogue:. Maplin Electronics also do copper wire on 50g and g reels in the gauges required I would suggest the g reels. Heavy items such as transformers have an additional carriage charge. On slowest speed, I count revolutions for a minute, then calculate winding time from that. Secondary is wound manually. No extra gap spacer is required as the ampere turns are well within limits for DC saturation.
I use plenty of 1-hour epoxy resin to hold it all together. That was not intended to be a lesson in winding transformers! Figure 3. Figure 4. The original uses a half-wave thermionic rectifier EZ The all-silicon power supply uses a different transformer HT secondary, and the rectifier heater winding is not required. I have shown a capacitor-choke-capacitor filter which should prove quieter than the original resistor-capacitor chain filter. A green L. Here, I allowed no compromise to get the best sound for this type of application.
It can be used without any limitation as preamplifier. It can drive any kind of power amplifier such as my Power Follower 99 , because it has enough output voltage swing, enough gain about 30db and a very low output impedance about 30 ohms. The schematic for one channel of the headphone amplifier is shown in figure 1. The improvements in this version come from the careful selection of parts, the use of tube diodes, and the elimination of the interstage MKP capacitor.
Please use only Allen-Bradley, 2W carbon resistors where specified in the schematic. I have not tested the Black Gates, but I know because I have read so in many articles that the Black Gates need many hours of use before they sound good. It is also necessary to switch on the amplifier every day, or the sound gets bad again.
It was not necessary to select the tubes. I bought them at:. The output stage is a paralleled-triode cathode follower. The amplifier will drive headphones of to ohms impedance. For more output to drive ohm headphones, add another 22K ohm resistor 9 to R k to increase the bias current of the ECC. The power supply schematic is shown in figure 2.
To get no-compromise performance, the rectification should be vacuum tubes only. I suggest using two 5Y3s or one 5R4, as you like. Only the first capacitor after the diodes could be a normal electrolytic type or better, a paper-oil type. The inductors can have an internal resistance of up to 70 ohms max. The filament supply is AC, but I am developing an alternative supply for use in a country like Italy, where I live and where the voltage goes from volts in the morning to the volts in the evening.
In my previous article , I presented a very good DC filament supply, but in tests, I heard better sound with the AC supply. To avoid turn-on thumps, wait about 30 seconds after switch-on before connecting the headphones. I will probably add a time-delay to the audio output, but integrated with a new regulator for the filament supply. The frame of the chassis is made of walnut and measures 53cm x 30cm x 5cm.
The top is a sheet of 3mm aluminum. I kept the wood separated from the metal with gaskets placed at the screw points. All of the audio input and output jacks are gold-plated. The extra octal tube socket seen in the photograph was for testing a 6SN7 tube. For commercial use of the circuits in this article, please contact Andrea Ciuffoli. Republished with permission. This article shows my tube headphone amplifier designs for driving headphones with an impedance of to ohms I am using these amplifiers with the Sennheiser , which has a ohm impedance.
The problem with many tube headphone amplifiers is the high output impedance and the low output current that decrease the sonic performance. The hybrid with the IRF source follower does not have very good sound, the amp with the output stage has pretty high output impedance more devices per channel would lower output impedance, but then the tubes must be carefully selected and the 6C33C-B is not very linear for a headphone amp but it is very good in an OTL amp for driving loudspeakers.
This model is very close to real tube performance, and I have developed an interactive program to find the right parameters. Here are the results for the ECC simulation in red, actual in white :. The SPICE model is so close that it is sometimes difficult to see the difference between model and real tube curves. Figure 3a.
Figure 3b. Figure 3c. The headphone amplifier circuits figures 3a, 3b and 3c use a single-ended triode class A gain stage and a paralleled-triode cathode follower output stage. It has good sound but with some distortion because noval new 9-pin tubes tubes are not very linear. I have tested the first version with a JAN Philips. Each section of is biased at 4. The second version with the 3A5 I used a RCA 3A5 , a direct heating tube, gives less distortion and has a very liquid sound as only direct heating tubes can do.
The third version with the a Jan Philips 6SN7 that I now prefer has a less liquid sound than the 3A5, but the distortion is very low and the bass response is fantastic! Sometimes during listening sessions with the 6SN7 I thought that the high frequencies were missing, but this is not true. I have mounted the 3A5 on a floating socket. Tube dampeners might also reduce the microphonic effect, but I have not tried them.
In all versions, the output tube V2 is biased at 26mA per section 52mA combined for a total dissipation of 6W 2x3W.
Figure 3d. All resistors should be Allen Bradley carbon types for the better sound. Figure 3d shows how I mounted the 7x22K resistors. The copper board templates are included in the PC board layouts below. In the last years, two trends have emerged about the capacitors to use in a high-end amplifier: MKP polypropylene output stage and interstage , electrolytics in the power supply and paper oil interstage.
The MKPs in many tests rank at the top for low distortion, low internal resistance and maximum speed under dynamic conditions. Electrolytics have higher distortion and lower speed, but very good electrolytics are now available, such as Black Gate and ELNA Cerafine, both designed for audio.
I have not tested these new capacitors, because I am searching for a good source with a good price before I buy.
In listening tests, the MKP has an inclination to smooth out contrasts. So make your choice! In this design, the output capacitor of the power supply and the output capacitor of amplifier can be replaced with uF or higher value MKP types or other audio types.
This list of capacitor sources is very useful for finding the right shop:. Figure 5. Figure 6. About the power supply, the filaments can be powered by AC or DC except that the 3A5 version 2 of the amplifier requires a DC filament supply. Each supply has a timed relay that mutes the audio output until the tubes stabilize.
I have designed 3 different power supplies — regulated, passive and cheap passive:.
Preamp tubes
We have lots of great conversations, we'd love you to join us, click here. What kind of cheap Chinese tube amp should I get? In the last few weeks, I've become obsessed with vacuum tubes, and would like to buy a tube amp and speakers. I'm currently in Hong Kong, and there is quite a variety of Chinese-made tube-based audio equipment available here.
tube amp 300Watts 2X16 6P3S-E
Aber sowas von! Wir vertreiben die Mach' ihn wieder fit! Pimp Your Guitar! Werten Sie Ihren Sound noch weiter auf, z. Zur Kategorie High Fidelity. Ohren auf! DeoxIT Luftfracht. Do it Yourself!
Does tube amp technology use harmonics to amplify?
Do you have the full schematic. Thank you. Just wondering, after reading a very interesting article, was the transformer designer you mentioned Menno Vanderveen? This idea of low gain or unity gain of the output stage is also something I have been working on, but achieving it in a very different way contact me if you want the schematic FYEO.
Tube power amplifier 3W with 6BX7
Thomas, Never heard of this tube until today that is Any chance of a project in the works using this tube soon? Sounds like a very good candidate for a headphone amp! Hi Randy, I have too many other things going on so will probably not get around to work with this tube for a long time. Hello Thomas - I am the happy owner of a little collection of these tubes.
Hifi Devices (1)
Volume 2 of the most complete and practical modern reference on tube guitar amplifiers. Out of necessity, Volume 1 was a bit more theoretical of the two. Chapter 4 discusses practical wiring, soldering and circuit modification issues seldom or never mentioned in other books. Although numerous circuit modifications and improvements have been dispersed throughout both volumes, chapters 5 and 6 cover two specific areas where mods are particularly effective and noticeable, namely in power supplies and in tone changes through simple changes such as tube and component substitutions. These case studies illustrate common issues and improvement options.
FrankCooter
And of course Ralph is a true gentleman and a constant pleasure to deal with. You made a remark somewhere about the 6BX7 being more linear than the 6BL7 because the grid is further from the cathode, to give the lower mu. I am certainly convinced that, all other things being equal, greater grid-cathode distance is goodness, because reducing grid-cathode distance is the principal cause of "tuck under" in the plate curves at increasing Vg. However mu is determined by grid pitch and by plate-grid spacing.
Do you still have this amp, or access to this amp. As others have suggested, the 6BW6 is quite a modest valve and this amp is unlikely to be pulling more than mA at full output. After that I build several small amplifiers mainly with different TDA-chips. A small 3 watt practice amp, which was advertised in the main Selmer Electronics catalogue during the mid's. I think I still have one - somewhere!!
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Zynsonix Link. The circuit is designed to power most headphones, including those with a 32 ohm impedance. Top and Bottom of PCB. Using all these tubes requires a hefty transformer, the 8.
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