01A has a high Rp, about 10K IIRC, and very low current handling, in the area of 3mA... I don't think you easily can power headphones with it. 12A has same gain, half the Rp, and double current handling (7.6mA).. It looks like the 01A does and sounds like an angel.. you might be able to power headphones with that tube, loaded with something like a 20K:600R preamp OPT..
EDIT: high impedance headphones...
EDIT: high impedance headphones...
For inspiration, take a look at "The Journey" preamp by Bjørn Aaholm at http://vinyl.and.triodes.net/. It is similar to what you are trying to do exept you want lower output impedance.
A problem with only one stage DHT is getting enough gain, as you will have to trade it to get low enough output impedance to drive your headphones. "DHTRob" has an unusual twist on an headphone amp combining a DHT and a IDHT without output transformers, at http://www.dhtrob.com/projecten/hfdtlfverst_mustage_1_en.htm. Could be worth a look.
Another good source for headphone amplifiers using tubes is www.headwize.com, but I don't think there are any DHT projects at that site.
Have a look around. Possebilities are many when power requirements are modest. I built a 700mW DHT amp very recently, 12A driving 71A, my first DHT amp
www.vt52.com was perhaps the biggest source of inspiration for me.
A problem with only one stage DHT is getting enough gain, as you will have to trade it to get low enough output impedance to drive your headphones. "DHTRob" has an unusual twist on an headphone amp combining a DHT and a IDHT without output transformers, at http://www.dhtrob.com/projecten/hfdtlfverst_mustage_1_en.htm. Could be worth a look.
Another good source for headphone amplifiers using tubes is www.headwize.com, but I don't think there are any DHT projects at that site.
Have a look around. Possebilities are many when power requirements are modest. I built a 700mW DHT amp very recently, 12A driving 71A, my first DHT amp
www.vt52.com was perhaps the biggest source of inspiration for me.Rocky said:
Thanks for finding this
I'm not to worried about gain as my sources are pretty good. I'll look into this one
I'm on that site, as well as headfi. You're right, I don't think there are any DHT projects. I'm building this one http://headwize.com/projects/showfile.php?file=waarde1_prj.htm
Followed by this one
http://headwize.com/projects/showfile.php?file=strain1_prj.htm
They're both OTL and low cost. I figure once I get them working I can move up to bigger and better things
Originally posted by Rocky Have a look around. Possebilities are many when power requirements are modest. I built a 700mW DHT amp very recently, 12A driving 71A, my first DHT amp
I saw that amp... I liked the look of it. It's actually what I want to try in the next few projects
I've seen on the net a couple of implementations using 01A to drive a 71A.
I planned on running the 01A at 100V/3.5mA/4V bias through a 6922 CF as well for a preamp.
I wanted to use this as a preamp, but I believe it will be as difficult as the 26 as far noise is concerned.
Joel Tunnah has an amp that uses 01A as drivers at 135V/3mA/9V bias via batteries.
I planned on running the 01A at 100V/3.5mA/4V bias through a 6922 CF as well for a preamp.
I wanted to use this as a preamp, but I believe it will be as difficult as the 26 as far noise is concerned.
Joel Tunnah has an amp that uses 01A as drivers at 135V/3mA/9V bias via batteries.
arnoldc said:I am as confused as you as to where to use my 01A
Tubelab.com has mentioned using them in a headphone amp. http://www.tubelab.com/AssemblyManual/Headphone.htm
-d
Yes, I built one headphone amp for a customer that used the 01A. The customer was thrilled with the design and sound quality of the finished amp. I am not a headphone user myself (my head sweats profusely with headphones on), and I was not that impressed with the sound, but he was. The customer was a high end audiophile who had purchased one on my TubelabSE 300B amps previously for a second amp. It wound up as his main amp. I had added a simple headphone jack to his amp using a 12 ohm load and 100 ohm resistors in series with the phones. This worked well for a while until he collected more headphones of different impedances. His music was mostly Frank Sinatra, Tony Bennet, Barbra Streisand type stuff, mostly vinyl.
This led to the experiences outlined on the web page. It took two weekend long sessions with him listening and me tweaking to get him the sound that he wanted. We tried at least 6 or 8 different tube types that I can remember (this was over 2 years ago) including the 45 (sounded best to me), the 30, 31 2A3 and 300B.
The 01A design put out about 100 MILLIWATTS of power. I was running the tube over the published 3 mA spec, but I don't remember where we wound up. There were two secrets to this success. We tried about a dozen 01A tubes to find some that could pass at least 10 mA of current, you need this much to get good bass. The output transformer needs to be able to match the tube to the headphones. Headphones come in a wide variety of impedances. We tried dozens of transformer combinations before finding the UTC LS57's. These are push pull transformers, but it didn't seem to matter at low current. The UTC transformers have output taps from 2 ohms to 500 ohms. The final design had 3 sets of jacks wired to 3 different taps for use with different impedance phones.
It was interesting that the rest of the amp design was a standard TubelabSE. The amp used PowerDrive, so it was capable of A2, but I never had time to scope the grid to see if it ever went there. Once we found the "magic OPT" the only tweak that he wanted was to put in his magic rectifier tube. After that it was " it is perfect, don't mess it up". The amp wound up in an ugly wood box because the new owner didn't want to wait for a cabinet. He lived over 200 miles from me and had travelled here on two weekends to get this made. I heard from him twice after he took delivery. Both times he wanted to be walked through setting the bias to try new tubes that he had collected.
This led to the experiences outlined on the web page. It took two weekend long sessions with him listening and me tweaking to get him the sound that he wanted. We tried at least 6 or 8 different tube types that I can remember (this was over 2 years ago) including the 45 (sounded best to me), the 30, 31 2A3 and 300B.
The 01A design put out about 100 MILLIWATTS of power. I was running the tube over the published 3 mA spec, but I don't remember where we wound up. There were two secrets to this success. We tried about a dozen 01A tubes to find some that could pass at least 10 mA of current, you need this much to get good bass. The output transformer needs to be able to match the tube to the headphones. Headphones come in a wide variety of impedances. We tried dozens of transformer combinations before finding the UTC LS57's. These are push pull transformers, but it didn't seem to matter at low current. The UTC transformers have output taps from 2 ohms to 500 ohms. The final design had 3 sets of jacks wired to 3 different taps for use with different impedance phones.
It was interesting that the rest of the amp design was a standard TubelabSE. The amp used PowerDrive, so it was capable of A2, but I never had time to scope the grid to see if it ever went there. Once we found the "magic OPT" the only tweak that he wanted was to put in his magic rectifier tube. After that it was " it is perfect, don't mess it up". The amp wound up in an ugly wood box because the new owner didn't want to wait for a cabinet. He lived over 200 miles from me and had travelled here on two weekends to get this made. I heard from him twice after he took delivery. Both times he wanted to be walked through setting the bias to try new tubes that he had collected.
The user had headphones ranging from 30 ohms to 300 ohms. The Hammond transformers that I tried (125CSE) could not put enough voltage into those 300 ohm phones to make enough volume. They may work with 55 ohms on the 16 ohm tap, but I think you will come up short on volume since there isn't much power to waste here since the tube will only make 1/10 of a watt.
I tried a transformer that had 5K ohm and 600 ohm windings. It drove the 300 ohm phones very well, but resulted in a weak distorted sound with the 30 ohm phones.
The UTC transformers that I have are used ones from the 1960's. I found them at a flea market for $50 with a non functioning homebrew 6L6 P-P amp attached to them. The user found NOS ones on Ebay. He paid about $500 for the pair.
I tried a transformer that had 5K ohm and 600 ohm windings. It drove the 300 ohm phones very well, but resulted in a weak distorted sound with the 30 ohm phones.
The UTC transformers that I have are used ones from the 1960's. I found them at a flea market for $50 with a non functioning homebrew 6L6 P-P amp attached to them. The user found NOS ones on Ebay. He paid about $500 for the pair.
500 beans is a bit pricey. There are sowter transformers
http://www.sowter.co.uk/headphone.htm
There are some models specifically for the 2A3, 300B etc. But at 72 pounds sterling each that's $252.00 plus shipping for the pair.
Would one of those work?
http://www.sowter.co.uk/headphone.htm
There are some models specifically for the 2A3, 300B etc. But at 72 pounds sterling each that's $252.00 plus shipping for the pair.
Would one of those work?
sbelyo said:
No.
The only one anywhere near the inductance you need is rated no DC (parafeed).
For the 01A, you have 10K Rp at it's max rating of Ua=135V, Ug=-9V.
remember the -3dB point f0=Rp/(2*pi*L)
I haven't put it through the calculator but I'd say you need something like 300 henries for decent bass...
I tested the tubes at 10 mA to weed out the ones that did not have enough reserve emission capability. I test 45's at 50 to 60mA, the ones that don't make it tend to sound wimpy when played loud. Some 45's will go over 100mA and some 01A's will do 20 mA or more. The test should be brief. 10 mA is only 1 to 1.25 watts which is nothing for the plate of an 01A. You just need to find a filament with enough emission. Given the age of these tubes, they are all over the place.
I measured 100 milliwatts early in the design cycle using a Hammond 125CSE and an 8 ohm load. Due to the hurry by the customer, I never tested the final design.
I set the bias somewhere in the 5 mA range. I did this over two years ago. Most of the tubes that I had were pulls from old radios and ones that I got cheap on Ebay, I don't remember any particular brand names. The customer bought several more tubes, mostly NOS, on Ebay. I explained that more current gives more sound (to a point) at the expense of tube life. I don't know where he finally set the bias.
The Sowter transformers should work well, but I have never used any of them. This was the only headphone amp that I have ever made. It was done by special request, and took up a lot of time. I had far more spare time then. The customer had read in an audio magazine that 01A's were "magic" and he had to have an amp with those. We tried other tubes, but he was convinced that the 01A's were the best. He did not seem to care what any thing cost, I think he paid $500 to get the transformers in a hurry. The old UTC's do go for big bucks on Ebay.
There were radios made in the 1920's that used an 01A to drive a horn speaker. I have an old metal cased Atwater Kent radio that has 6 or 7 tubes, ALL 01A's that feeds speaker. I got it at a junk shop in Wheeling West Virginia for $20. I don't have the speaker, but pictures show it as a horn.
I measured 100 milliwatts early in the design cycle using a Hammond 125CSE and an 8 ohm load. Due to the hurry by the customer, I never tested the final design.
I set the bias somewhere in the 5 mA range. I did this over two years ago. Most of the tubes that I had were pulls from old radios and ones that I got cheap on Ebay, I don't remember any particular brand names. The customer bought several more tubes, mostly NOS, on Ebay. I explained that more current gives more sound (to a point) at the expense of tube life. I don't know where he finally set the bias.
The Sowter transformers should work well, but I have never used any of them. This was the only headphone amp that I have ever made. It was done by special request, and took up a lot of time. I had far more spare time then. The customer had read in an audio magazine that 01A's were "magic" and he had to have an amp with those. We tried other tubes, but he was convinced that the 01A's were the best. He did not seem to care what any thing cost, I think he paid $500 to get the transformers in a hurry. The old UTC's do go for big bucks on Ebay.
There were radios made in the 1920's that used an 01A to drive a horn speaker. I have an old metal cased Atwater Kent radio that has 6 or 7 tubes, ALL 01A's that feeds speaker. I got it at a junk shop in Wheeling West Virginia for $20. I don't have the speaker, but pictures show it as a horn.
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