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headphone amp design w/ true headphone OPT

post #1 of 15
10/15/09 at 9:56am
Thread Starter 
Are there any good designs for an SET amp with a true headphone amp OPT with 300-600 ohm taps on the OPT?
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post #2 of 15
10/15/09 at 3:12pm
To my knowledge there aren't many true headphone amp OPT's readiliy available... with the exception of Sowter in the UK and probably very few others.

Dsavitsk has a few designs on his website, some of them parafeed, but for lower impedance cans. Higher impedance headphones seem to be more popular over here, but schematics for headphone amplifiers are scarce.
I built a SE-OTL amp using the C3G as my first amp that can be converted to SE-output transformers (sold by Gerd Reinhoefer. He is one of the top guys to wind transformers in Germany...).

I also recently breadboarded something similar (spud amp using either D3A, E810F or C3G) using vintage Saba OPT's and an HV shunt regulator.
Sounds quite promising but still has a few issues, one of them being not satisfactory bass reproduction, probably due to too little primary inductance of the old OPT's...

Other than that a few amplifiers have been built using tubes like 6H30 with Lundahl transformers or exotica using 45's or 71a's... but then you are pretty much on your own and OPT's have to be custom wound.

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post #3 of 15
10/15/09 at 4:49pm
Electra-Print will wind the transformers you need at a reasonable price. Have you been through the plans at Headwize? There are a few that meet your requirements.
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post #4 of 15
10/15/09 at 5:23pm
Lundahl or Electra-Print are great choices.

If you're going parafeed (with a plate choke or current source) you can use small amveco toroids or the Edcor 10K:600 transformers (I wired mine as about 5K:300 autoformer and it worked great.)
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post #5 of 15
10/16/09 at 1:19pm
Thread Starter 
I can design an OTL headphone amp but I am pretty lost when a transformer is involved. Looking for a plan that I could follow to the letter. Wanted a classic SET no parafeed.
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post #6 of 15
10/16/09 at 1:48pm
As Eric said...

HeadWize - Project: Hi-End Transformer-Coupled Tube Headphone Amplifier With Digital Input by Andrea Ciuffoli

HeadWize - Project: A Zero-Feedback SRPP-Input Headphone Amplifier by Simon Busbridge

All of them (including the attached schematic by K&K Audio further up are quite straightforward to build...
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post #7 of 15
10/17/09 at 4:25am
Thread Starter 
This is an updated design from the same guy. Looks very promising. Would be cheaper to buy a Woo6 or something but this way I would know what I am getting. Opinions?




Hi-end headphone amplifier
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post #8 of 15
10/17/09 at 5:11am
While I didn't build exactly this one, that is the schematic I mentioned earlier...
sits on a breadboard with vintage OPT's and shunt regulator (see attached schematic).
D3A's are a bit difficult to deal with because they are prone to oscillations, that's why I also tried other pentodes like 7788 and C3G. But apart from an issue with low level hissing I feel limited by the old output transformers... but haven't quite got the money at the moment for some Lundahls or custom wound transformers.
The HV shunt regulator (by Salas over at diyaudio) is very worthwhile to build... I am using the same schematic to power my Aikido headphone amp with parafeed output transformers, and it is the most musical psu that I built so far.





Apart from the psu it doesn't get much easier than the Cuiffoli design
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post #9 of 15
10/17/09 at 5:49am
Thread Starter 
Thanks again.


The issue I am running into is that buy the time you buy 5k/300 DC gapped transformers you could just buy a Woo SET amp for less. I wonder what the design is actually on those amps, probably they are using a cap to block the DC so they can use cheaper OPT's ? It is an odd time these days when it is cheaper to buy an amp than to build one.
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post #10 of 15
10/17/09 at 11:05am
Quote:
The issue I am running into is that buy the time you buy 5k/300 DC gapped transformers you could just buy a Woo SET amp for less.
Well, not exactly... The Woo6 is about 585 US plus shipping (?) while Jack at Electra Print (quote dsavitsk) will wind you SE output transformers (and with better quality probably) for about 100 a pop when I remember correctly.
The built quality on Woo stuff is quite amazing though ... and looks carried out much better than Singlepower .
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post #11 of 15
11/30/09 at 9:33pm
Quote:
Originally Posted by regal View Post
This is an updated design from the same guy. Looks very promising. Would be cheaper to buy a Woo6 or something but this way I would know what I am getting. Opinions?




Hi-end headphone amplifier
i've a similar design built but using a tube rectifier instead of a solid state. using different rectifiers, you get different sounds, i might prefer that of a 5u4g over a 5R4 with a slightly higher B+







the 1689 is an excellent transformer, but if your budget permits, you can try the amorphous core version which is more than twice the price of the regular
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post #12 of 15
12/2/09 at 8:39am
Nice, clean build!!

I happen to have the same 5R4 on my C3g headphone amp... (or others )
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post #13 of 15
12/2/09 at 12:24pm
Quote:
Originally Posted by stixx View Post
Nice, clean build!!

I happen to have the same 5R4 on my C3g headphone amp... (or others )
thanks

the post tubes are indeed one of the best tubes i've ever used so far, i've four pairs of c3gs and c3ms sitting around, now having heard the d3a i'm even more curious about how a c3g would sound.

are you using your c3g under transformer coupling or capacitor coupling?
any c3g schematic to share?

i'm intending to use the c3g the same way as the d3a, i.e. cathode bias resistor 200-220 ohms, and B+ between 180-220V. probably coupling the output with a capacitor for convenience till i get another pair of OPT
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post #14 of 15
12/2/09 at 1:09pm
Quote:
are you using your c3g under transformer coupling or capacitor coupling?
any c3g schematic to share?
Both... my first ever headphone amplifier is a cap coupled C3G which is kind of "different" because it is a simple anode follower that supposedly has quite high output resistance.. It sounded not overwhelming in the beginning, only after I changed the entire psu to MKP capacitors and used Os-con caps in the cathode it sounds very nice ...



My other C3G sits on a breadboard (see post 8, there with E810F). Schematic is quite similar, but I am running them at 155V and 147R cathode resistor (around 14mA). Don't have the money for your nice Lundahls at the moment, but maybe when I get around to case it up...
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post #15 of 15
12/2/09 at 3:42pm
Another D3a amp here, using regulated power supplies for both B+ and heaters.
No Lundahl 1689 but Sowter 9351 output transformers with very good results to my ears.


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