Project Headphone amp build thread.

[davefo]

Ian, jeremy

Sorry if I appeared to raise this as an issue again. That wasn't my intention. I was pointing out that the remaining hum issue I had was nothing to do with the amp but was instead to do with poor quality cables.

Just so anyone else is aware just because the plugs appear to be gold plated, it doesn't necessarily mean the cables are anygood.

Dave

[Deleted]

No problem, Dave. I seem to be a noise magnet. If anything is going to hiss or hum, it'll do it for me for sure!!

Mine is extremely quiet now.

In fact, it's one of my favourite amps and has this rock solid, warm and weighty sound that nothing else that I have does. It's quite unique.

[BonOeil]

Hi,

I'm very interested about this amp but how it is in comparaison with a Bottlehead Crack if somebody tried both of them ?

Anything else, why don't put a (cheap) stepped attenuator from eBay instead of the ALPS potentiometer ?

[Deleted]

Crack = high voltage all tube amplifier intended for high Ohmic headphones with a 120 Ohm output resistance and gives 6dB more SPL in high Ohmic headphones compared to the Sunrise.

Sunrise = low voltage hybrid amplifier intended for low to high Ohmic headphones and the output resistance can be set for 10 Ohm or 68 Ohm.

So not comparable.
How they will sound comparably is (certainly in this case) highly dependant on the used headphones.
The choice of which amp to buy (in this case) should depend on the impedance of the headphone(s) owned.

the technical reason for using a stepped attenuator is tracking, in other words differences between L and R channel in amplitude when adjusting.
So each step has a very similar attenuation for the L and R channel.
In case of a volpot a difference CAN be present which can vary depending on the volume setting.
Especially in the lower volume settings region.
with a stepped attenuator this difference is smaller value than with (cheap) pots.

Since above mentioned amplifiers do not have overall feedback the amplification is dependant on the tube.
Only a few of all tubes I tested have a very close matching in amplification, the main technical reason to have a stepped attenuator is totally irrelevant now as tubes often have 0.5dB to 2dB differences in amplification factor.

For an open frame I would not recommend a stepped attenuator as the sheer size of it and the open unshielded character of them makes them nice antennae for picking up hum and other nasties.
A (grounded) and preferably shielded volpot is preferred in this case.

Also the frequency range of a stepped attenuator is smaller, has more contacts and much more solder joints are present.

So the choice of an attenuator comes down to subjective perceived differences and how it 'feels' when adjusting.
Stepped attenuators are believed by subjectivists to be superior in sound.
Measurements, like in most cases, cannot confirm this.
Strangely every subjectivist is MUCH concerned about solder joints but NOT concerned about having lots of them in series with a stepped attenuator.

[Deleted]

Strangely every subjectivist is MUCH concerned about solder joints but NOT concerned about having lots of them in series with a stepped attenuator.

That's not quite true Frans. Most people , whether sujectivists, or "Sergeant Schultz" types,are more concerned about the quality of the soldered joints, not the number of them.(although there are a few exceptions )
Also, you are well aware that the thin film resistors used in the better type attenuators are also lower noise, and much closer tolerance,as well as having lower capacitance. A good attenuator has a much wider bandwidth than a typical volume control too.
The differences are VERY measurable , despite you insisting that
reported audible differences are due to people's imagination, most likely based more on the premium prices often paid for them.
Alex

[Deleted]

I bow to your wisdom

I am glad to be mistaken again and appear to have no REAL knowledge in TRUE audio matters ;D

[BonOeil]

Thank you Solderdude It's very interesting !

I have a Beyer DT770 Pro in 600 Ohms and a Alessandro MS1i so the Sunrise is more recommended I think.

[Garage1217]

To note, small form factor alps pots are not used in the sunrise design. I use bourns pro audio units which I like a lot better in this size / footprint.

[BonOeil]

By the way, how many ampere it doing at maximum ?

Somebody use a linear power supply in place of the switch power supply ?

Thank you

[Deleted]

0.6A @ 24V ... its class A so always constant.

[BonOeil]

Fine so a 30VA toroidal transformer is enough.

I have to build a power supply for it, so full parts kit with board only is good ?

[Deleted]

30VA may be a bit small when building a regulated linear supply.
The regulator will get hot.

The PS must be able to deliver at least 1A and the regulator will also use up power so 30VA might be on the tight side.
the trafo will be loaded with about 20W continuously which is already steep for some 30VA trafos.
Perhaps a 50W is more suited and the costs may not be that much higher.

[BonOeil]

I've forgot the waste of power so I'll buy a 50VA or maybe a 80VA R-Core transformer if I can put it in my enclosure.

One more thing before I order it : what's the difference between minus chassis and serialized chassis ?

[Garage1217]

If asking about the Sunrise Chassis, there is a K chassis and a standard chassis. The one marked with a K means it came in Kit form. For example S/N:0101 is a pre-built amp. S/N:K0101 is a kit.

[BonOeil]

Thank you, I've order a full kit of it.

I'll be back to give my feedback !

What's the best valve for it ?

[Garage1217]

In the world of valves, there is really no best... just what people like best! Talk to 5 people and you will get 5 answers. I suggest you give the stock one a go, then pick up a few other types and see what you like. Mike has some great tested / matched - select units for sale on here that you will like I am sure.

[BonOeil]

I just see Project Sunrise II !

What's the changes between both them ? Maybe I should have wait a bit...

[Garage1217]

Was wondering if anyone would notice it Still about 30 days off. Production / Sales of the current version were stopped / pre-orders welcome for the new version.

The original Sunrise has become popular enough we decided to give it another go and add some features that some were requesting.
- Easy Bias via LEDs. No need for a multimeter but still has the test points of one desires
- Adds a line output for pre-amp use
- Improved protection circuit for pre-amp use
- Some other changes to the circuitry
- Slightly larger footprint
- Changed the layout a bit because of the line out addition

No worries, the amps are VERY similar, especially SQ wise. Enjoy your Sunrise! Listened to my original for hours today. Was a good day.

Merry Christmas everyone and Happy new years just around the corner!

[PinkFloyd]

No worries, the amps are VERY similar, especially SQ wise.

Can you please define "very similar"?

[PinkFloyd]

Same old in a different package? If not, how are they dissimilar and WHY should they be SIMILAR? They are either not as good, the same or better.... please define "similar".... to "me" that means a lot of things and not all of them good things... please explain....

[Garage1217]

Hey Mike, Per your questions

- Sunrise II is the same amp / same parts audio wise with the added
features listed above and different layout. Sonically it is the same,
save 1 change to the circuitry which cleans up the waveform at higher
volumes, generally past 12'oclock. This will be released soon as a mod
to the original sunrise and is very easy to implement and can be totally
hidden.
- The mute circuit is different, this one also works when powering the amp on and off by switching the mains power.

- Volpot grounding was added into the new PCB per your suggestion which eliminates the 2'oclock noise that Ian noticed.

- Ceramic coupling caps prior to the volpot were changed to film per
requests. I cannot hear a difference between the two in this particular
position but some say they can so they were included, as well as two
footprints if one want to use their choice cap (100pF) is the proper value.


So in short "similar" should be "identical" (when the small mod is implemented) with added features mostly on request by owners.


A higher power version of Sunrise II that is still class A is in the works
that will share the same PCB and will be released just after Sunrise
II. It is called "Project Horizon" This version runs on 48V. For those
that need more power for high-Ohmic (300 and 600 Ohm) headphones.


A lot of components are different between Sunrise II and Horizon so while a swap from a Sunrise II to a
Horizon is possible, desoldering on a thick PCB is not practical and it would not be cost effective so a person should choose one or the other depending on their needs. Cost will be higher on the Horizon amp as it uses a much more expensive power supply, different chassis, a few more parts, some of which are more expensive.


Horizon is still a open air chassis in Acrylic like Sunrise II to keep
the amp affordable. It is available without a chassis so one can put it
in whatever chassis they desire. Also, because it runs past the
generally safe 42VDC mark, Guards are included for the areas that one
could accidentally touch. So while it is open air, it is safe to use
around kids or accidental touches. I am looking into offering an aluminum
chassis built specifically for the new PCB but it is not cheap
unfortunately. Or just source your own if desired. This board is
slightly larger than the original Sunrise PCB at 4.25" x 5.25" (133.35mm
x 107.95mm) to note.

Happy New Years!
Jeremy

[Garage1217]

Just a sneak peak prototype of the new amp. This is an early revision to note. Some layout changes have been implemented, rear PS caps moved closer together, DC input and power switched spaced out for easier access, all major items such as heater voltage selection, bias and output impedance can now be adjusted without taking off the top. Similar in looks to the original Sunrise.

[Garage1217]

Sneak peak at the final revision / boards in production now and will be here a little later than planned unfortunately. They will arrive on the 10th or 13th of Feb.
- Output resistance is selectable from the outside of the chassis via right angle jumpers in the front of the amp / on each side.
- Not shown in this version until the new top is made, 6/12V tube jumper is also accessible from the top of the amp, just behind the tube via an extended 3 pin header

So in short, you can adjust bias or select output impedance without taking off the top now.

Made several other small changes and visual changes from the original SRII proto. Top covers due late this week and will post pics for you guys.

[PinkFloyd]

That looks great Jeremy, it'll be so much easier to dial in different settings / tweak it now without having to take the top plate off.... nice one

[Deleted]

Really nice idea to be able to change the output impedance. Higher power too so plenty of headroom.

Getting better all the time Jeremy.

I really enjoy mk 1. A really entertaining listen. It even drives a k601 nicely. Mine's used every day.