There may be some issues with regards to the output current capability not being enough to drive my pair of Audio Technica ATH-M30X Headphones, cause it's quoted impedance is 42 Ohms.
Last edited by DrNomis_44; 12-07-2018 at 11:13 PM.
After some further googling for info on the internet, I've found that you can substitute an ECC88 tube for a 6N1P, I was doing some quick reading of some service manual PDFs for my Telequipment D33R Oscilloscope, and found that it uses a few ECC88 Tubes, since some new 6N1P tubes from Evatco will probably set me back something like Au$20 each or so, I'm going to try using three ECC88 tubes from my Telequipment D33R scope to build the OTL Headphone amp instead of three 6N1P tubes, I've read in a forum that the ECC88 sounds better than the 6N1P.
From looking at the circuit of the 6N1P OTL Headphone amp, one half of V1 is used as a common cathode voltage amplifier, it's anode is connected directly to the grid of one half of V2, which then has it's cathode connected to the anode of the second half of V2, this forms a low-impedance output stage, it's an interesting design, very simple for an OTL Headphone amp.
Update:
Turns out there was only one ECC88 tube in my Telequipment D33R tube oscilloscope, the rest of the tubes in it are either 6BL8, or ECF804 small-signal Triode-Pentode tubes, so I'll have to order some 6N1P and ECC88 tubes from Evatco after all.
Last edited by DrNomis_44; 24-08-2020 at 10:25 AM.
After some ummmm-ing and ahhhhhhh-ing, I've elected to mount all the resistors, caps, and power diodes on some tag boards with solder-tags on two sides of the boards, rather than wire it all up point-to-point style, so I'll need to order some suitable tag boards from Evatco along with all the other needed components, I'm still debating in my head what I'm going to use as the chassis for my OTL Headphone Amp build, once I've got everything worked out and all the needed parts, I'll start the build-process and will be doing a write-up as I go along, will also include some photos as well.
I've just finished drawing some layouts for the tagboards which will be used to mount the components.
Evatco sell two different types of tag boards I could use to mount all the resistors, caps, and power diodes on, one of them is a dark brown phenolic 36-way tag board with two rows of 18 tags, it looks like this:
Seeing as I'm really in the mood for doing some diy scratch-build Tube amp projects this year, the diy scratch-build OTL Headphone amp is officially scheduled for 2023, well, it'll give me something "constructive" to do with my time anyway, besides, it'll fun.
You know what? getting back into doing some diy builds this year again, has made me re-discover why I got into electronics in the first place, it's because it's a whole lot of fun to go through the process of getting together all the parts for your build projects, and put them all together into a finished working electronic device, you get a huge sense of achievement out of it knowing you built it yourself, you also learn far more by doing practical things, rather than sitting in a classroom, well that's how I seem to learn best anyway.
Last edited by DrNomis_44; 04-02-2024 at 09:31 AM.
Here's a link to one interesting OTL Headphone amp design article, it looks really simple and easy to build, just notice how simple the circuit is compared to a solid-state design of similar performance capability:
I think I have finally found the OTL Headphone amp circuit I want to build, this particular design uses a set of three 6N1P twin triodes and it looks like it can drive load impedances down to about 64 Ohms, some of the other designs I was considering building aren't happy with driving low impedance loads as low as that, here's a link to the webpage:
Evatco don't seem to have the Hammond 269AX power transformer in stock, but, Mouser Electronics do seem to stock it, so I'll have to order it online from there.
I just found the perfect application/use for my diy scratch-build 6N1P OTL Headphone amp build, currently I'm using a pair of wireless headphones with my new Blaupunkt HDTV, while the wireless headphones works with it, it has a nasty habit of the rechargeable battery going flat at annoying times, I can't use a pair of wired headphones with the Blaupunkt because there's no headphone out socket, but, it does have stereo RCA Audio Line-Outs on the back, all I would need to do is connect up my 6N1P OTL Headphone amp to the stereo RCA line outs and plug in a pair of headphones.
Last edited by DrNomis_44; 04-05-2023 at 04:13 PM.
I looked on the Evatco website and as it turns out, they do stock 6N1P Twin Triode Valves, they may also stock the Hammond 269AX Power Transformer as well.
I'm going to be mounting all the components, minus the main power supply filter caps, on tagboards, so, I'm now in the process of designing suitable layouts for the tagboards, I'll need to make three of them, one for the power supply, and two others for the left and right channels, this is going to be a fun build.
I've made a hand-drawn copy of the full schematic and will post a scan of it later on......stay tuned!!
I just ordered three new Svetlana 6N1P tubes online from Evatco, for my 6N1P OTL Headphone amp build, Evatco don't stock the Hammond 269AX Power Transformer I need, but fortunately Mouser Electronics do have it in stock, so I'll order it online from Mouser Electronics, they may also stock all the resistors and caps that I'll need too, so I'm going to do some browsing on their website and see what I can find.
Jaycar stock this big diecast aluminium box which I will be using as the chassis for my OTL Headphone build, it's a little bigger in size than the one used in the original build article:
Oops....I just found out that the Hammond 269AX power transformer only has a 115/125V AC primary winding, so I'm going to have to go looking for a similar specced transformer with a 240V AC primary.
Evatco do have a Hammond 369AX power transformer in stock that looks like it'll do the job, it has a 250V CT @ 115mA secondary winding, a 6.3V CT @ 2A Heater winding and a 240V AC primary, so I'll order one of them instead.
Last edited by DrNomis_44; 26-07-2023 at 04:43 PM.
I’m wondering why you don’t just get a 240v to 6.3V transformer (if such a thing exists) and just use straight 240V instead of 250V for the secondary side. More efficient and you only drop the secondary voltage by 10V/4%.
Posting Permissions
Reply With Quote