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Old 31st March 2010, 09:42 PM   #1
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Default DHT amplifier for orthodynamic headphones

Hi

I'm a happy owner of Yamaha YH100 modded to the limits. I use them with an amplifier made by a man who knows good about tubes and electronics ( 6l6 in se triode connected driven by 6sl7 srpp ) but I would like to make an headphone amp by myself. The project statements:
-It must be Transformer-coupuled
-It must be Single-Ended
-Power tube must directly-heated
-It must give a minimum 2 Watts

YH100 have rated power of 3 Watts so these are not easy to drive Grados.

I was wondering what DHT tube can I use? The Sovteks 2a3 are cheap and as my friend said have great price/perfomance ratio for 2a3s. 45 are said to be better in sonics but they have won't deliver much power.

Frank Cooper made an very interesting amp using GM70 ( yes, you read
correctly, that 125W tube ).
"This is the amp I brought to the recent NorCal meet. Plenty of pictures in the meet impression thread. Basically it's a simple two stage, zero feedback, SET using a triode connected Western Electric 418a to drive a Russian GM70 via an interstage transformer. Output is via an Electra-Print 5k:32 transformer. The GM70 is run at a relatively low 550V@60ma. Sort of my interpretation of the Japanese "Sakuma style". Power supply is a dual mercury rectified, LCLC filtered "brute force". Power out right now is about 6 watts. Probably capable of three times this if the B+ is cranked up. "

For me a GM70 is an overkill for orthodynamics so I wouldn't use it. What other DHT can I use?

Karol
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Old 1st April 2010, 03:12 AM   #2
Gordy is offline Gordy  United Kingdom
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Karol,

According to Yamaha YH-100your - Wikiphonia your YH-100 is rated at 98 dB for 1 mW.

(Ignore the 3W as that is the maximum that the headphone can take continuously before overheating damage, likewise the 10W is the very short term peak that can be accepted before damage. These figures have NOTHING to do with loudness for the user, and everything to do with physical limitations of the headphones).

Most people seem to listen to headphones in the region of 70 - 85 dB. However you might want high power for peaks; power doubles for every 3 dB of sound pressure, so 1mW for 98 dB leads to 128 mW for 119 dB (which I understand is about maximum rock concert level).

So perhaps your design target should be about 128 mW not 2 W !

With respect to Frank Cooter (not Cooper), his GM70 amp seems based on a combination of fun and ego-trip. Good luck to him, however please note that you can get better performance from a more simple design.

If you go with a DHT then I am sure that many people will recommend DC heating for the filament, otherwise it will hummmmmmmmmm very badly.

However it is possible that the best solution is a non-DHT design?
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Old 1st April 2010, 07:27 AM   #3
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"However it is possible that the best solution is a non-DHT design?"

What do you think about?

"If you go with a DHT then I am sure that many people will recommend DC heating for the filament, otherwise it will hummmmmmmmmm very badly."

A friend of mine who built a few Sun Audio 2a3 kits with AC heating said that non of his amps had hum problems. Sun Audio uses hum balance pots between the filament ends and as far as I know, AC heating is more heatlty than any DC heating.
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Old 1st April 2010, 07:06 PM   #4
Gordy is offline Gordy  United Kingdom
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Quote:
Originally Posted by krisio06 View Post
"However it is possible that the best solution is a non-DHT design?"

What do you think about?
My recommendation is a 6H30, with a constant current anode load and a parallel feed output to a transformer such as the Sowter 8665.


Quote:
Originally Posted by krisio06 View Post
"If you go with a DHT then I am sure that many people will recommend DC heating for the filament, otherwise it will hummmmmmmmmm very badly."

A friend of mine who built a few Sun Audio 2a3 kits with AC heating said that non of his amps had hum problems. Sun Audio uses hum balance pots between the filament ends and as far as I know, AC heating is more heatlty than any DC heating.
Naturally it is your design choice, however when combining AC heating a DHT with headphones I say "Good luck".
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Old 3rd April 2010, 08:59 PM   #5
dBel84 is offline dBel84  United States
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I use orthodynamic headphones exclusively and they will not be phased by a 50W power amp driven hard, ignore the ratings and just realise that they are inefficient and benefit from OTT power. Now build the amp you want and don't limit yourself to the headphone moniker.

I have spent a fair amount of time with a 300B amp ( with both the YH100 and YH1000, not to mention an assortment of others )and personally it had more eyecandy than sonic merits. I would recommend a good hybrid over most any tube amp for this particular application.

The choice is obviously yours but if you are open to other designs there are many possibilities.

..dB
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Old 3rd April 2010, 09:43 PM   #6
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>50W power amp

Does it give 50W into 8 ohm or 150 ohm load? YH100 drivers won't survive a 50W shock, for sure.
Before I got that 6l6 se amplifier, I had a LM3875 GainClone with all gizmo's you might possibly want ( separate power transformers, Black Gate N 100uF and STD 1000uF, dual mono PS, Riken and Caddock resistors ) and my amplifier sound better with YH100 than GC. GC had more bass but that bass itself had no impact comapred to 6l6 se, the mids were not exacly natural, either the trebles. I've not tried it with other speaker amps so I don't know how does it sound with other construcions.

Do you think that 6B4G driven by choke loaded 6SL7 will do the job?
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Old 4th April 2010, 11:28 PM   #7
dBel84 is offline dBel84  United States
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You are right in saying that they will not survive 50W and the amp is a 50W speaker amp rated for 8 ohm load , so not 50W into the YH100 either. Not debating that and neither suggesting it. The point was that you don't have to view the amp design in the context of a headphone and look for something with 150-300mW.

If the amp is well designed , it will sound good. I use hybrids as it affords the best of both worlds - offers tube characteristics with the output capability of solid state. The amps I have used are not widely known outside of the DIY Headphone sphere and I will not get into them here if this does not interest you.

Tube amps that I have heard the YH100 with include the Bijou which is a futterman style amp - it is a very pleasant combination.

The remainder are commercial which doesn't really help you. The amp I currently use is a mosfet hybrid which uses the 6DJ8/6H30 and a parafeed or transformer coupled 6H30 as suggested by Gordy is a good idea.

..dB
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Old 4th April 2010, 11:53 PM   #8
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by Gordy View Post
Naturally it is your design choice, however when combining AC heating a DHT with headphones I say "Good luck".
That will be tough. But no problem with DC heating. I use this amp (with different OPT's) with AKG 701's. No hum. Very nice sound.

loftin white 801 amp

Sheldon
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Old 15th April 2010, 10:30 AM   #9
sachi is offline sachi  United States
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I am in agreement with dBel84 on this.

I think Broskie's Akido and Cavalli AUdio's EHHA are two amps to seriously consider for amping your orthodynamic headphones.

Also check out the parafeed spud amplifier here http://www.ecp.cc/

Last edited by sachi; 15th April 2010 at 10:53 AM.
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