ECC88 OTL heaphone amp - diyAudio
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Old 22nd December 2011, 06:29 PM   #1
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Default ECC88 OTL heaphone amp

Looking for a tube headphone amp for my Sennheiser HD600 I saw this OTL with ECC88, it seem simple design & easy to make, advice & ideas will welcome.

PSU

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OTL headphone amp

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PCB

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Picture

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Also exist other version without integrated PSU.

Last edited by merlin el mago; 22nd December 2011 at 06:38 PM.
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Old 22nd December 2011, 06:58 PM   #2
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Hi Merlin,

this schematic is loosely based on the better known Morgan Jones ECC88 OTL headphone amp which is an improved version of the famous Earmax amp.
Check out the info on
HeadWize - Project: The Morgan Jones Mini Tube Headphone Amplifier by Chu Moy since the original Headwize site is down.
I have built the Morgan Jones myself with LED bias for the first stage and a better psu (but now I would definitely use the Salas shunt for B+). When you are interested in a schematic I can mail it to you... it is easily built P2P on perf board. It is a nice sounding amplifier although there are better ones (non-OTL comes to mind).
When you are interested I can give the details for a very good sounding amp based on the C3G wired as triode, Salas shunt for HV and output transformers...

Cheers
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Old 22nd December 2011, 07:35 PM   #3
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Hello Stixx,

I'm looking for a tube headphone amp capable to drive my Sennheisser HD600 not necessary must be OTL, I'm interested on the C3G amp please send me details (I have Salas shunt HV for B+)

Greetings

Felipe
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Old 23rd December 2011, 10:04 AM   #4
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See schematic attached... it doesn't get much simpler than that.

http://s7.directupload.net/images/us...7/fg3o8znu.jpg

You have the choice of output transformers... I am using headphone opt's from Reinhoefer in Germany that sound very good at about 55 a piece. But you can try anything that has about 7.5k:300 for your Sennheiser phones ( I am using Sennheiser's). Lundahl and Sowther have very good OPT's as well. Or have them custom wound at AE Europe in the Netherlands.

My amp is still on the breadboard
--> http://s3.directupload.net/images/us...8/rap477if.jpg
but will eventually look like this -->
http://s1.directupload.net/images/us...4/wzrdgt9j.jpg

Just my two cents in headphone amplifiers...but I have tried quite a few schematics and am currently building the eighth one
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Old 23rd December 2011, 10:18 AM   #5
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Forgot to mention that I am running the C3g at around 150V and 15mA now...but with the Salas shunt it is easy to try different voltages until you find your "sweetspot". The rectifiers provide a slow ramp up of the HV after about 20 sec.
Cheers!
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Old 23rd December 2011, 11:40 AM   #6
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Thanks for schematics & pics, where can buy the matched C3G tubes with a reasonable price with good quality?
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Old 23rd December 2011, 01:14 PM   #7
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check german Ebay...

here for instance
2 PIECES OF C3g-C3 g-SIEMENS-NOS-NEW-OWN BOX | eBay

Good seller, although prices have gone up over the last years. But a good ECC88 is not cheap either...
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Old 23rd December 2011, 01:19 PM   #8
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I have a couple of these E88CC Russian military stock bought to Erno Borbely (sounds amazing), could I use them?
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File Type: jpg DSC00051.jpg (438.5 KB, 838 views)
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Old 23rd December 2011, 01:26 PM   #9
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No, ECC88 cannot be used in a single stage amp, it is best for preamp duty.
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Old 23rd December 2011, 01:38 PM   #10
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OK thank you.
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