I'm planning on an OTL headphone amp and was wondering if it's worth the extra expense to use film output cap's, or just go with electrolytics bypassed with Miflex copper.
It depends on what value of capacitance you need. If it's less than 10 uF, a film cap won't be terribly large, or terribly expensive. Beyond that, film caps can get very large and expensive. Of course, much of this depends on what type of film cap you are considering (polyester, polypropylene, etc), and what voltage rating you require. Personally, I would always opt for a film cap if size/cost are not out of bounds.
How much DC leakage current will you allow to go to your headphones?
DC current moves the voice coil out of the center of the magnetic gap.
Electrolytics sometimes have significant DC leakage current.
Some old non-electrolytics sometimes also have significant DC leakage current.
Note:
Now there are 2 Threads on this.
DC current moves the voice coil out of the center of the magnetic gap.
Electrolytics sometimes have significant DC leakage current.
Some old non-electrolytics sometimes also have significant DC leakage current.
Note:
Now there are 2 Threads on this.
I linked one thread to the other to cover the bases. Anyway, if I go with a bypassed electrolytic, I will use a Mallory 250uF/250V can cap bypassed with a 0.022uF copper foil Miflex. The straight film will me a Mundorff 220uF/250V EVO oil, which will cost about three times more.
My question is, will the extra expense be worth it?
My question is, will the extra expense be worth it?
A bypassed electrolytic with a film capacitor can improve the sound significantly but it strongly depends on the value. A 10µF elec with a 2,2µF or even 1µF in parallel will increase the resolution (well, if the amp can deliver the details) but with 100µF a 2,2µF will do sh*t.
Don't expect drastically changes, it will be subtle, esp. on low level the increase in SQ will be bigger. If you only listen to pop or rock, the increase in SQ will probably not be audible.
Don't expect drastically changes, it will be subtle, esp. on low level the increase in SQ will be bigger. If you only listen to pop or rock, the increase in SQ will probably not be audible.
Purchase whatever single cap, or whatever single and parallel bypass caps that you want to try first.
. . . Then measure the millivolts of DC that appear, or that do not appear, across the headphone voice coil (headphones connected).
Next, rated capacitor voltage.
You did not post a schematic, I have no idea about the topology, and no idea about the maximum B+ voltage that occurs at power up before the tubes warm up an provide a load to B+, or in the case of a tube failure that does not draw B+ current.
I always use rated voltage that is higher than the maximum unloaded B+ voltage.
For example, I have some B+ that start out at almost 400V, before the tubes warm up.
I always use 600V or 630V coupling caps on those amplifiers.
likewise, your output cap, can be called a "coupling cap" because that is what it is . . . it couples Signal (AC) but blocks DC.
Some parts are not cheap.
Sanity and Insanity has been defined as a line; Sanity on one side, and Insanity on the other.
Guess on which side of the line all Hobbies appear?
You do not have to think hard to know the answer.
Frank Reps wrote an article, "Baby Ongaku 2A3 amplifier" which was in "Sound Practices" (thanks Frank Reps) . . .
Frank said: "Good is not Cheap, and Cheap is not Good".
(And thanks Joe Roberts, and Thanks Gordon Rankin for your parts in the making. of this article too).
Getting Quality is like pulling Eye Teeth. If you are not a dentist, it will be even harder for you.
. . . Then measure the millivolts of DC that appear, or that do not appear, across the headphone voice coil (headphones connected).
Next, rated capacitor voltage.
You did not post a schematic, I have no idea about the topology, and no idea about the maximum B+ voltage that occurs at power up before the tubes warm up an provide a load to B+, or in the case of a tube failure that does not draw B+ current.
I always use rated voltage that is higher than the maximum unloaded B+ voltage.
For example, I have some B+ that start out at almost 400V, before the tubes warm up.
I always use 600V or 630V coupling caps on those amplifiers.
likewise, your output cap, can be called a "coupling cap" because that is what it is . . . it couples Signal (AC) but blocks DC.
Some parts are not cheap.
Sanity and Insanity has been defined as a line; Sanity on one side, and Insanity on the other.
Guess on which side of the line all Hobbies appear?
You do not have to think hard to know the answer.
Frank Reps wrote an article, "Baby Ongaku 2A3 amplifier" which was in "Sound Practices" (thanks Frank Reps) . . .
Frank said: "Good is not Cheap, and Cheap is not Good".
(And thanks Joe Roberts, and Thanks Gordon Rankin for your parts in the making. of this article too).
Getting Quality is like pulling Eye Teeth. If you are not a dentist, it will be even harder for you.
Last edited:
I think there are thousands of Franks in the world.
You are one of them.
Frank Reps is another of them.
I did not mean to cause any confusion, sorry.
And, I added lots of edits to my Post # 6, AFTER you replied to it.
You are one of them.
Frank Reps is another of them.
I did not mean to cause any confusion, sorry.
And, I added lots of edits to my Post # 6, AFTER you replied to it.
I am using a 10uf odam Vcap capacitor and a 0.022uf Vcap CUTF capacitor connected in parallel at the output of the amplifier, I find it very great. How much money do you plan to invest in that location, from there you can consider choosing the appropriate capacitor. miflex capacitors are quite good. But I prefer to choose jantzen Sliver Zcap capacitors because the sound is quite natural
Greetings Friends. I've found this thread while seeking similar answers. OP provided neither a schematic nor the impedance of the headphones to be used and I would like to re-frame the discussion around the Morgan Jones Headphone Amplifier. In the linked Headwize page, the author implements a series of alterations to the original circuit, making it more suitable for Low Z cans. I have a pair of HD 600 and I would build such an amp to drive 300-ohm loads. In older articles such as this one, it's pointed out that High Z cans don't require large uF output caps, and film caps become a possibility. So the question is, are DC Link caps (such as these WIMAs) suitable as outputs?
Thanks for taking a look!
Thanks for taking a look!