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simple SE headphone amp

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Since I never had a tube amp I have decided to build a simple tube transformer output headphone amp.

Tube candidates could be C3g, but it is an expensive one and not easy to get one or 6s45P or the similar 6c45P. They are not too expensive, have decent gain, acceptable plate resistance and can handle 7W.

So I came up with two solutions, a parafeed and a "classic" se tube amp. Any comments on the schematic are welcome!

My other problem is hard to get a good output transformer. Only headphone dedicated transformer i found is the sowther transformers.
 

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I have a spud amp using a EL55 like your parafeed version. I used a torodal power transformer as the OT and it works well out to past 30khz and is a cheap option. The parafeed cap is probably marginal at 3uf. The inductance of the transformer and the capacitance of the parafeed cap forms a resonant tank which will produce a frequency bump somewhere below 100hz. Most parafeed designs underspecify this cap and treat the bass boost as an advantage. My implementation uses a 8uf cap, but it is not uncommon to see a cap of 40uf in this position.
Unfortunately the exact cap value will be dependent on the output impedance of the valve and its usually a matter of trail and error to get the correct value.

Shoog
 
Since I never had a tube amp I have decided to build a simple tube transformer output headphone amp.

Tube candidates could be C3g, but it is an expensive one and not easy to get one or 6s45P or the similar 6c45P. They are not too expensive, have decent gain, acceptable plate resistance and can handle 7W.

So I came up with two solutions, a parafeed and a "classic" se tube amp. Any comments on the schematic are welcome!

My other problem is hard to get a good output transformer. Only headphone dedicated transformer i found is the sowther transformers.

I found a company BEZ in China sells a dedicated HP transformer at a reasonable price. I have not tried any of their products yet, but there was a post here on DIYaudio that indicated that they were OK to deal with.

BEZ tube amplifier
 

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The 6e5p is a very nice tube for this application. I built an amp around this tube : http://www.diyaudio.com/forums/tube...ns-parafeed-headphones-amp-2.html#post4037465

For the transformers, edcor makes small 10k/7k-300/32 parafeed transformers which are surprisingly decent. You can get them in Europe from Don-Audio.

Wrt the bass bump of parafeed, one solution is to either use a rc network in // with the output cap. Another solution might be to simply use a big electrolytic... I did that in another amp and, honnestly, I can't hear a difference with mkp caps I used before (40uf mkp vs 220uf electro).
 
I have a spud amp using a EL55 like your parafeed version. I used a torodal power transformer as the OT and it works well out to past 30khz and is a cheap option. The parafeed cap is probably marginal at 3uf. The inductance of the transformer and the capacitance of the parafeed cap forms a resonant tank which will produce a frequency bump somewhere below 100hz. Most parafeed designs underspecify this cap and treat the bass boost as an advantage. My implementation uses a 8uf cap, but it is not uncommon to see a cap of 40uf in this position.
Unfortunately the exact cap value will be dependent on the output impedance of the valve and its usually a matter of trail and error to get the correct value.

Shoog

I think you ment E55L. :)
Probably you are right about the capacitance, though simulations showed, that 3uF is enough. The real tests will tell, I think i have to do some experiment.
 
I found a company BEZ in China sells a dedicated HP transformer at a reasonable price. I have not tried any of their products yet, but there was a post here on DIYaudio that indicated that they were OK to deal with.

BEZ tube amplifier

It seem to me, that they offer pretty much iron for a small amount of money. I think it is worth to give it a try. I will contact them, if they can create some custom transformers. I wil inform you if I have any news.
 
I built a SET amplifier based on the C3G which I like a lot because of the midrange and treble... some details can be found here -->
C3G SET

Before I settled on the Lundahl transformers (got them at a good price) I also used transformers from german winder Reinhoefer (53-61...) with very good results.
In another amplifier (Aikido) I tried inexpensive Hammond line transformers as parafeed trannies, and they did surprisingly well.
 
Wow really nice builds! :drool:
I will check both the hammond and edcore transformers.

I am still not sure wether to go parafeed or not, but many builders seem to happy with them. Though the ccs and the large cap bothers me a bit.

Do you have any suggestions on rectifier tube, or should I go for SS rectifer? :)
 
If you want to get the sound of a valve rectifier without the waste and hassle take your diode (preferably schottky or a similar soft recovery type) place a snubber across it (1nf in series with 100R is a good start) and then place in series a 100R resistor before the first cap or choke. I absolutely defy you to be able to hear any difference between this an a valve rectifier.
A engineering approach to understanding why they might sound different is the best way to dispel the magical thinking.

Personally I prefer the superior performance of a nude schottky.

Shoog
 
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