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Garage 1217 Project Sunrise III measurements

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atomicbob:

--- Quote from: Solderdude on May 25, 2015, 07:55:40 AM ---The amount of distortion greatly depends on the output level.
The lower the output level the lower the distortion.
At 'Normal' listening levels the THD levels are considerable lower b.t.w.
--- End quote ---
An excellent point! The dScope measurements were performed with a -1 / -2 dBu output. I tend to listen with a level averaging -10 dBu or less. I should reprogram the dScope amp scripts to allow a lower reference and repeat.

Tube dependency allows tuning amplifier character to suit one's tastes. It also makes comparison of notes between listeners a little more difficult as they need to discuss which tube was used that gave them the sound they heard.

I did not put up the crosstalk measurements as I found considerable variance depending on the cable used for TRS to stereo RCA for connection to the dScope input. The least expensive Radio Shack performed much better than a major name high end super duper TRS to stereo RCA cable, for example.

atomicbob:
Conditions:
1. PS Vane 12AU7
2. PS3 32 ohm output setting
3. 50 ohm load
4. 4 Vpp input from signal generator (+5.23 dBu)
5. 600 mVpp output from PS3 into 50R load

Frequency Response

-0.5 dB  3 Hz to 70 KHz
-3.0 dB  1 Hz to 200 KHz

10KHz and 100 KHz square wave response
top trace - signal generator input
bottom trace - Project Sunrise III output

10 KHz square wave response:


100 KHz square wave response:



100 KHz square wave response x-axis zoom:

Cos:
Interesting page! Thanks for taking the time to do the measurements! ahoy Wondering how the Sunrise compares against the local classic, the much revered Bottlehead Crack. Using just one (exotic) tube, to me has the advantage of beeing cheaper than two for Crack, not to mention four for Valhalla 2 (finding matched tubes EDIT: other than the smart and nicely priced set provided by Shiit - extra headache).

Also wondering if the Sunrise/Horizont schematics can be modified similar to Valhalla 2 to be optimized for both high and low impedance headphones.

Solderdude:

--- Quote from: Cos on September 14, 2015, 09:17:19 AM ---Also wondering if the Sunrise/Horizont schematics can be modified similar to Valhalla 2 to be optimized for both high and low impedance headphones.
--- End quote ---

The amplifiers differ too much to compare.

In case of the Valhalla2 there are 2 output resistances to 'choose' from. 14 Ohms or 3.5 Ohms.
The reason there is some difference in output R has to do with the topology (the way the circuit is built) and the amount of feedback.
It's an 'all tube' design.

More feedback = lower gain = lower output R
Less feedback = higher gain = higher output R
Those aspects are directly coupled within the design.
It also means that even though the valhalla can be used with low impedance headphones it is more suited for higher impedance headphones.

For the SR/Horizon things differ.
Firstly this is a (low voltage) hybrid design (more akin to Lyr than Valhalla, EDIT: in output stage)
The gain and output Resistance can be set separately and are not coupled.
The internal gain of the amplifier is not determined by the amount of feedback (which it is in Valhalla)
In SR/Horizon the gain is determined by the tube used and there is NO overall feedback at all.
The input signal can be attenuated (so not gain control technically but attenuation control).
The amount of attenuation can be changed quite easily by the user (SR-III, Horizon III).
For the older versions the 2 gain steps are fixed.
The output R can be set in 3 steps: 1.5 Ohm, 35 Ohm and 68 Ohm for SR and 1.5, 35 Ohm and 120 Ohm for Horizon.

Both SR and Horizon can be used for low and high impedance headphones.
the SR can provide a bit more current in low-Z headphones while the Horizon can provide a higher voltage for higher Z headphones or low Z headphones that could best be driven from 120 Ohm.

schiit:

--- Quote from: Solderdude on September 14, 2015, 12:56:34 PM ---Firstly this is a (low voltage) hybrid design (more akin to Lyrr than Valhalla)

--- End quote ---

Incorrect. Both Lyr and Lyr 2 are high-voltage hybrids, not starved-plate designs. They have a proper 200V B+ rail. Which may make them unique at their price points.

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