DIY Audio Projects Forum

Hi Bruce,

Thank you for the Headphone Build. This was my first tube amplifier build
and I learned a lot. Especially proper grounding techniques and the use
of a current regulator. Great job explaining those topics.

Observations:
Pros: The sound is clean and full.

Cons: Under powered. At .63dbv voltage gain, it can barely drive my Beyer Dynamic
DT-770 80 ohm headphones.

Suggestion: Please avoid hyperbole like "This is much more output than is needed for really
excessive sound levels with most headphones." It is misleading!

@slotube Which output transformers are you using in your build? If they have additional taps on the output side (e.g., a center tap), I would try one of those to see whether it's a better match.

Hi Bradley,
I am using the Edcor xsm10k/150 and using
the 75 ohm center tap. I measured an impedance
of 63 at that tap. So it's in the ballpark. The was done
measuring the output in Vpp with two different loads and
calculating for Z

Hi, I'm glad you liked the project but you are the first person who indicated it didn't have enough output. I did say for most phones. The large majority of which have sensitivities in the 100db per milli watt range. For them the 50-100 milli watts is quite excessive. Yours are the exception clearly. Yes I did say the gain was low and that some sources might be insufficient. Since a basic goal of that project was simplicity I don't consider any of that hyperbole. There is nothing saying you can't make a better or more suitable project. That is what diy is all about and indeed how I got started about 12 years ago.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:

• PoddWatt: 5751 / EL84 Push-Pull DIY Tube Amplifier Project
• OddBlocks: KT88 Push-Pull DIY Tube Amplifiers (Mono Blocks)
• ForeWatt: ECC802S (12AU7 / ECC82) DIY Tube Preamplifier Project
• GrooveWatt: Tube (Valve) RIAA Phono Preamplifier Project

I'm using a modified circuit to run 6CG7 tubes with different outputs. Drives speakers. As Bruce mentions, some clever DIY might be the answer.

If the 6DJ8s can handle it, maybe a small step-up transformer on the front end would be enough? I'm using a 10K-90K step up on one of my inputs since the source is a bit lower level, which helps. Anything with an appropriate turns ratio would probably work well enough to test the idea.

Hi Bruce,
Thanks for your reply. Yes, you were clear on the output.
But I like tweaking, building and improving things, so
further refining will be fun with this elegant design.

I am also in the process of building your 12AU7 Preamp Design and
looking ahead at possibly the Push-Pull EL84 Poddwatt. I am a fan of
the current regulating design you use.

Thanks again!

Hello
Since a few weeks I am building the ecc88 headphone amp. Today I could listen to one channel of the amp, the first time.
So far it sounds very good without any distortion or hum.
But there are a few things I am wondering about.
Maybe you can help me to find the answers to my questions.

1. The input signal on the pin 7 is higher than the input signal on pin 2. I thought that the input signal on both inputs should be the same?
2. I am wondering about the amplification factor. The output signal in volts on the output of the output transformer is higher but only a bit higher than the input signal ( pin7 ) at all. It is even not as twice as high. That is the reason why I think, there is something wrong with the amp.

Thank you all in advance.

I've made a start (finally) on my second version of this amp, after having had the original version in use for over a year now.

First up is the power supply:



The mount is printed in PETG, and the output transformers will get something similar. The power brick is a 15V 4A Meanwell unit, so I still have the 7806 to handle the filament power.

The enclosure will be made out of hardwood, with some copper (probably lasercut) panels for the front/back and as a ventilation panel for the internal components.

The Khadas will get it's own hardwood little box, that I'm going to try to mount/attach to the amp so it looks as one coherent unit, but could still be easily detached.

I also recently got a matched quad of 6p-14p-EVs to try my hand at a PoddWatt with those and the 6n1Ps

Kind regards

Nim

Hi, what boost converter did you use? I have found many are pretty noisy.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:

• PoddWatt: 5751 / EL84 Push-Pull DIY Tube Amplifier Project
• OddBlocks: KT88 Push-Pull DIY Tube Amplifiers (Mono Blocks)
• ForeWatt: ECC802S (12AU7 / ECC82) DIY Tube Preamplifier Project
• GrooveWatt: Tube (Valve) RIAA Phono Preamplifier Project