300B Headphone Amp

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Ray P
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300B Headphone Amp

Post by Ray P » Sun Nov 19, 2017 7:17 am

It won't be very long before I start building my 300B Headphone amp project. It'll essentially be a scratch build of the Transcendent Sound 'Masterpiece', which is essentially a single output valve version of the Transcendent 300B SE-OTL amps I brought to Owston.

Andrew/Nick, at Owston we talked about trying your new regulated supply for the B+ and I'm wondering how this is looking? The 'stock' B+ supply is CLC delivering around 150V 110mA per channel. The inductors are rated at 1H 240mA. I have all of the parts except the mains trasnformer and if we're still to try your new regulator I'll need to specify a secondary winding to allow for the regulator drop when I order from Canterbury Windings.

I've also been looking at the Neurochrome 21st century Maida regulator as a possibility.

More generally, I've got some modiied versions of the PCBs I used in my SE-OTLs for the amp build, a couple of Andrew's DHT filament supplies for the 300Bs and a pair of Dave Slagle's autoformers for the volume control. All will be housed in a chassis similar to the one I used for the SE-OTLs, though I''m thinking the silver finish is a bit old hat so maybe I should take a lead from Steve's 6B4G project.

I plan to use the amp with the 600ohm Beyer Dynamic DT880s that Judy's getting me for Christmas.

Ray

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Re: 300B Headphone Amp

Post by Andrew » Fri Nov 24, 2017 4:29 pm

Hi Ray,

Nick and myself are in the process of modifying the PCB design so it can handle power valves. Let me have a chat with Nick and see where we're at.

cheers,

Andrew
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Re: 300B Headphone Amp

Post by izzy wizzy » Fri Nov 24, 2017 6:46 pm

Is this the thing you'll be building?
http://www.4tubes.com/SCHEMATICS/BY-BRA ... dphone.bmp

I'm getting headphones for Xmas too and will be building something like this.
http://kandkaudio.com/images/PP%206H30% ... %20amp.pdf

It would be hard to think of two more different headphone amplifiers. Should be fun :)

cheers,

Stephen

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ed
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Re: 300B Headphone Amp

Post by ed » Fri Nov 24, 2017 7:37 pm

the k and k circuit looks interesting..I keep visualising plastic critters and wonder if it started life as a solid state circuit..
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Re: 300B Headphone Amp

Post by izzy wizzy » Fri Nov 24, 2017 7:50 pm

I don't like them ss thingys so I'll probably centre tap choke load the first stage and use a resistor in the tail of the second. No CCS whatsits to start with. I have most of the parts lying around here some place.

cheers,

STephen

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Ray P
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Re: 300B Headphone Amp

Post by Ray P » Sat Nov 25, 2017 11:15 am

izzy wizzy wrote:
Fri Nov 24, 2017 6:46 pm
Is this the thing you'll be building?
http://www.4tubes.com/SCHEMATICS/BY-BRA ... dphone.bmp
Yep.

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Re: 300B Headphone Amp

Post by Ray P » Sat Nov 25, 2017 4:31 pm

Should have expanded a little in my previous post...

I've chosen the Transcendent circuit for two reasons;

1. It is essentially the same circuit as the SE-OTL amps I brought to the last Owston meet but with only one 300B perchannel instead of four. The SE-OTL amps are the best I've owned so hoping for more of the same.
2. I have most of the parts to build it left over from my SE-OTL project so it's a relatively cheap project.

Ray

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Re: 300B Headphone Amp

Post by Ray P » Sun Nov 26, 2017 7:23 pm

Broke the ice today...

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Re: 300B Headphone Amp

Post by Andrew » Thu Nov 30, 2017 7:07 pm

Hi Ray,

Looking good! Whose are the PCB? Just professional interest....

cheers,

Andrew
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Re: 300B Headphone Amp

Post by Ray P » Thu Nov 30, 2017 8:48 pm

Andrew wrote:
Thu Nov 30, 2017 7:07 pm
Whose are the PCB?
Cheers Andrew. I laid out the PCBs myself (I used my PCB layout for the driver section of my 300B amps as the basis for these boards). I had the PCBs fabricated by this outfit.

http://dirtypcbs.com/store/pcbs

I've had several boards done by them and they've all been fine (for my purposes) and very good prices. I had 10 of these 300B headphone amp boards fabricated and delivered from China for around $25 IIRC. Only downside that I can see would be if I were in a hurry as they take a couple of weeks to arrive.

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Re: 300B Headphone Amp

Post by Ray P » Sun Oct 14, 2018 5:41 pm

I had some time on my hands today (no cycling in this weather) so I dusted off a couple of semi-dormant projects, including this one. I finished off asembling these boards and hatched a plan to incorporate my Soekris DAM 1121 DAC board into a chassis with these units; It should make a nice combo for the spare room...

I assembled the boards with the two outputs configured with different caps to suit 32ohm and 600ohm headphones rather than a line-out option.

This project will still be a slow burner as I want to focus on the 6C33C amp and my DSD decoder first.

Ray

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Re: 300B Headphone Amp

Post by Ray P » Mon Nov 26, 2018 8:50 pm

I started to assemble the Soekris R2R DAC into the chassis yesterday;

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Re: 300B Headphone Amp

Post by Wolfgang » Mon Nov 26, 2018 10:49 pm

I am using for some time the Neurochrome regulator (Ray's recommendation) for the #26 buffer and it has changed my opinion about reg. B+ psu. Originally I wanted to try it with my EF86 buffer but here it somehow limited the harmonics and the difference between pentode and triode settings wasn't so clear anymore compared to the CLCLC psu. But for a single DHT it seems to be an excellent choice.

I would even suggest to give up the CCS and use cathode bias instead together with the Neurochrome reg. in the case of the MP. That would keep the clarity but add also some warmth. The 300B as biased in the original MP has very little distortion but can also sounds a bit too "neutral" for my feeling. With good headsets the combination of B+ regulator and more harmonics would be a perfect match IMO. TS 300Bs are biased for best linearity /least distortion which is great for driving speakers (300B OTL) but it might not be what we would expect from a 300B preamp driving very high quality headsets. But maybe it's already to late for changing things?

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Re: 300B Headphone Amp

Post by Ray P » Mon Nov 26, 2018 11:07 pm

Not to late at all Wolfgang, I haven't done anything about power supplies for the HPA aspects yet, I have made up my Masterpiece amp boards (with CCS), as covered a few posts ago but nothing else. This is my lowest priority 'back burner' project and I'm just working on the Soekris DAC stuff at the moment.

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Re: 300B Headphone Amp

Post by wantech » Wed Jan 01, 2020 12:18 pm

I am looking for a 300b preamp or headphone amp schematic,
can somebody HELP ! :bounce:

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