Building the Starving Student II Hybrid Headphone Amplifier

Completed Starving Student II.
Completed Starving Student II.

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The popular DIY budget amp has graduated and fully realized its potential.

Completed Starving Student II.
Completed Starving Student II.

The first Starving Student hybrid headphone amplifier originally debuted in 2008 on Pete Millett’s DIY Audio Pages. Pete had gained notoriety in DIY and headphone enthusiast circles by publishing tube, solid-state, and hybrid amplifier designs online and by making them public domain. Pete’s previous creations were highly praised, and when he designed the original Starving Student, he had a new agenda.

“The idea was to design the simplest, lowest-cost hybrid headphone amp possible. It still had to perform well and sound good, of course. I think I succeeded… it sounds very good.” – Pete

The Starving Student II (SSII) shares the same basic architecture as the original. It’s a triode voltage amp, with a MOSFET source follower that is loaded by the tube heaters. It differs from the original primarily in two ways: using 18FX6 tubes rather than the 19J6 (due to availability shortages of this tube) and with the addition of a switchable plate load between resistive or Constant Current Source (CCS).

The SSII is a hybrid (meaning both vacuum tube and solid-state) headphone amplifier and preamplifier.
The original Starving Student amplifier from pmillet.com.
The original Starving Student amplifier from pmillet.com.

Many folks built the original Starving Student on a shoe-string budget with point to point wiring and salvaged cases. In contrast, the Starving Student II is available from diyAudio Store (in collaboration with Pete) as a Printed Circuit Board (PCB) with all components and a chassis. It’s a polished and professional product that is at odds with its austere namesake.

Original Starving Student point to point wiring from pmillet.com.
Original Starving Student point to point wiring from pmillet.com.

This article will discuss:

  • Building the Starving Student II. How to populate the printed circuit board (PCB) of this beginner-friendly tube amplifier kit.
  • Assembling the aluminum case available from diyAudio Store.
  • Reviewing objective measurements, and my subjective opinion on how it sounds.
The polished looking Starving Student II.
The polished looking Starving Student II.

Before we dive into this new tube project, and to better understand where this design comes from, let’s first take a look at the designer – Pete Millett.

Who is Pete Millett?

Pete is a self-professed ivy-league engineering school dropout. He is an electrical engineer and for almost 40 years has done board-level hardware design for computers and consumer electronics.

“I don’t do a lot of audio work in my “day job”, though I am working on some class-D amp ICs right now. I’m just old enough that when I was a kid, I worked with vacuum tube designs a bit.” – Pete (In a personal email exchange)

As a hobby, he’s been designing all sorts of tube audio gear and sharing it with the world. Pete has created headphone amps for Headroom, written for audioXpress magazine and started several audio businesses (Wheatfield Audio and Apex Hi-Fi).

“…mostly I design and publish DIY designs, largely tube audio stuff… I’m an engineer. I don’t believe in the latest fashionable nonsense, boutique wire, magic rocks, stuff like that.” – Pete (In a personal email exchange)

The Starving Student II Amplifier

As mentioned above, Pete’s original goal was to produce a good sounding, inexpensive and easy to build DIY headphone amplifier. Currently, the SSII is available from diyAudio Store for $119 (PCB + components) or for $229 including the case.

“I partnered with the diyAudio store to provide a complete kit – including the enclosure – because lots of potential builders aren’t comfortable sourcing parts or building chassis. The hope was to make it approachable for people with little or no experience building electronics.” – Pete (In a personal email exchange)
Beezar Audio offers original Starving Student kits, PCBs and components. The Beezar Audio kit builds version 1 of the Starving Student which uses the 19J6 tube and does not have the CCS load option.

By ordering the SSII kit from diyAudio Store, the preparation work is already done for the builder. There is no need to carefully peruse a Bill of Materials (BOM) to select and order the right components – they all come in the kit, neatly bagged and ready for installation.

The parts box freshly delivered and opened.
The parts box freshly delivered and opened.
Clearly the SSII kit is intended to be as easy as possible to complete for the neophyte DIYer.

One of the aspects that I like most about DIY is that you can often ask questions directly to the designer and, in some cases, assist with the development of a project. Pete is a regular contributor to the Head-Fi and diyAudio forum discussions. He frequently answers questions and provides assistance, even though he does have a standard disclaimer:

“In ALL of these cases, I make no profit from any of the sales. Zero, zip, nada. I have a normal “day job” that pays the bills, this is strictly a hobby with me. So please do not expect me to provide the level of technical support that you might expect when buying a product.

I try and help, but it sometimes takes me days – even weeks if I’m traveling for work – to respond.” – Pete

Starving Student II Specifications

SpecPlate Load150 ohm load30 ohm load
Gain (at max volume setting)CCS20 dB18 dB
Resistor17 dB16 dB
Frequency response +/-3dBCCS11Hz - 40kHz18Hz - 40kHz
Resistor12Hz - 50kHz20Hz - 50kHz
Frequency response 20Hz-20kHzCCS+/- 0.8dB+/- 1dB
Resistor+/- 0.8dB+/- 1dB
THD+N 1V 1kHzCCS0.47 %0.15 %
Resistor1.8 %1.3 %
Maximum output @ 5% THDCCS9.9 V RMS2.5 V RMS
Resistor3.1 V RMS2.4 V RMS

Starving Student II Circuit and Design

The amp uses a pair of 18FX6 tubes (functioning as triodes) as a voltage amplifier stage. The SSII design uses a MOSFET source follower (also known as a buffer or common-drain amplifier). The gate of the MOSFET is biased such that there is about 18V on the source terminal of the MOSFET, which is loaded with the 18FX6 tube heaters.

This type of circuit has several desirable traits including the MOSFET can provide power and current gain, as well as providing low output impedance. The MOSFET draws no current from the input, has infinite input impedance and the output will not drop under load.
The Starving Student II circuit.
The Starving Student II circuit.

The input signal is applied to grid #1 after the volume control and the plate AC is capacitively coupled to the output stage.

All the parts out of their bags and ready for assembly.
All the parts out of their bags and ready for assembly.

The output RCA jacks are deactivated when a headphone plug is inserted in the jack. Both headphone and RCA outputs are muted for approximately 15-20 seconds upon start-up to eliminate any ‘thump’ noise from capacitor charging.

The 18FX6 Tube

The 18FX6 is an uncommon tube choice for a headphone amplifier as it was traditionally used in radios (they were used in the last generation of the “All American 5” tube radio). It is a pentagrid converter, which in Pete’s words “turns out to make a pretty decent amplifier if you connect it as a triode”.

The 18FX6 tube.
The 18FX6 tube.

Pete purchased thousands of the 18FX6 tubes after the original Starving Student tubes became difficult to source. They are all ‘new old stock’ (NOS) from a large master case and likely 1960’s vintage. Most are labeled Raytheon and were made in Japan, although Pete says he has examples from just about all the manufacturers (RCA, Sylvania, Westinghouse, etc.).

“I did this largely to keep the amp affordable – I bought literally thousands of these tubes, so we could be sure that they would never run out. That’s something I learned from the original Starving Student.” – Pete (In a personal email exchange)

Pete expects that the tubes should last between 5,000-10,000 hours. Although the tubes included in the kit are not ‘matched’, all measure just about identically (Pete reports of the ones he’s measured, the gain was matched to about +/-0.2dB).

The 18FX6 tube is rated at 18V and 0.1A across the heater (very similar to the first Starving Student 19J6 tube rated at 18.9V and 150mA). This means the SSII has the same 48V DC 0.625 power supply requirements as the original and has plenty of current to drive most headphones with ease.

“In case you’re wondering, yes, it’s OK to put audio on the tube heaters. Think about it – normally they run on 19V RMS AC. In this case, they’re running on 19V DC, with a little bit of audio superimposed (rarely more than 1V or so).

There could (theoretically) be a little coupling from the filament to the cathode – the cathode resistor is un-bypassed – but it would be negative feedback, and the capacitance from heater to cathode is so low compared to the cathode resistor it would probably only be measurable at RF frequencies.” – Pete Millet

Selectable Constant Current Source or Resistive Plate Loading

To increase flexibility in tuning the sound of the amplifier, Pete changed the design of the SSII to include a pair of jumpers to select between resistor or CCS plate loading. The jumpers are accessible by removing 4 screws from the bottom of the chassis (if using the diyAudio kit).

The blue load jumpers currently in resistor load position.
The blue load jumpers currently in resistor load position.

CCS Benefits

  • Lower distortion
  • Increased linearity
  • Increased gain

Resistor Benefits

  • Softer clipping
  • Traditional tube sound
“So with very sensitive headphones or IEMs, the resistive setting tends to be a better match. With low sensitivity headphones where you need more gain and higher output levels, the CCS works better. But there are no rules, you can use whatever sounds better to you.” – Pete (In a personal email exchange)
The diyAudio chassis uses free sliding nuts in the side rails. While effective, they aren’t convenient for quick bottom panel removal and replacement and are a bit finicky to use.
The blue load jumpers currently in resistor load position.
The blue load jumpers currently in resistor load position.

CCS Biasing LEDs

The CCS uses a PNP transistor, biased with two blue LEDs which are also used to light the tubes from below. Unfortunately, for many enthusiasts who love the glowing tube aesthetic, the 18FX6 tubes have little to no glow on their own.

The blue LEDs shining up through the tube.
The blue LEDs shining up through the tube.

In this case, since the blue LEDs are used in the circuit, it makes sense to also use them to shine up through the tubes. This provides a bit of visual interest and functions as a power indicator.

The blue color is a controversial choice. In a recent discussion on the Headphone Audio group on Facebook, (although there were a few positives) the overwhelming response was negative.

“I am not a fan at all, just seems gimmicky to me.”

“Tacky blue LED’s look cheap imo.”

“Don’t like it personally, looks cheap. I much prefer the natural glow of tubes.”

Many expressed a preference for a different color, preferring a more natural orange or yellow tint to appear like a glowing tube filament.

“I like it for certain tubes, for example, if you can’t see the natural glow of the tube then it’s ok to have an LED to make it look cool, but on tubes where you can see it glowing, nothing looks better than seeing the natural tube glow.”

However, Pete participated and explained why changing the LED color isn’t possible with this circuit design:

“If you use the CCS plate load option (as opposed to the resistor load) you shouldn’t change the LED. Not for a different color, or even a different brand/type of blue LED. The forward voltage of the LED sets the reference for the CCS, so changing it will change the plate current. Even within blue LEDs, the forward voltage varies from under 3V to over 4V.” – Pete

.

So blue!
So blue!

Of course, you can mount the LEDs inside the chassis (on the other side of the board) so they don’t show.

If you use only the resistive load you could even omit the LEDs. I followed the stock instructions and did not do this for the build featured in this article.

Starving Student II Aesthetics and Quality

The diyAudio kit is of excellent quality. The printed circuit board is attractive, thick, intelligently laid out and clearly labeled. All you can ask for in a PCB.

The Starving Student II board layout.
The Starving Student II board layout.
The first release of the PCB reportedly had smaller than normal solder pads that made it a bit tricky to use. diyAudio store quickly addressed the issue and sent out replacement boards. The revision 2 board I received presented no issues.
The bare PCB.
The bare PCB.

The aluminum case is made in Italy by HiFi 2000, a company that has produced precision-milled electronic cases since 1977. The case features a 10mm thick, black anodized, aluminum front panel. All cuts and edges are perfectly done and smooth to touch. It’s held together with a combination of (included) Philips and hex screws, which fasten the top, bottom, front and back to the side pieces.

The completed case.
The completed case.

The volume knob is fashioned from satin-finished solid aluminum. The power button is black plastic.

The completed kit is fairly diminutive in size. It’s about 5.25 inches wide and 7.75 inches deep (including the volume knob). The case is 2 inches tall and the small 18FX6 tubes add about another 2 inches in height. It weighs approximately 1.75 pounds so, with its rubber feet, it isn’t likely to move around on your desktop.

The case pieces.
The case pieces.

Assembling the Starving Student II

Building the SSII is a very straightforward affair that should only take a few hours to complete. Assembly is helped immensely by following Pete’s excellent assembly instruction manual. As always, take your time, read carefully, and check your work. You should have very few issues completing the build.

To populate the SSII PCB, you will need a few basic tools:

  • Soldering iron
  • Solder – Tin/lead 63/37 is recommended.
  • Wire cutters
  • Fine tipped needle nose pliers
  • Digital Multimeter (DMM) to test

To assemble the case:

  • Phillips Screwdriver
  • Metric Allen (hex) keys
My work bench and shop.
My work bench and shop.

Experience is not necessary to build the SSII, as this is designed to be a basic kit to assemble. However, a little practice soldering would be beneficial to not damage components or the PCB. With some care and careful following of instructions, this project is entirely appropriate for a first-time builder.

PCB Population Instructions

This section is a standard inclusion in my build articles.

Assembly of the components on the PCB can happen in any order, however, the instructions organize things to install the lowest profile components first and work up through the taller parts. Parts are numbered from the lower-left corner when the PCB is positioned so that the writing is the proper orientation.

If you are new to electronics, some components are polarized (such as capacitors and diodes) and MUST be installed in the proper (marked) orientation! Other components such as resistors can be installed in either orientation, although for neatness, I recommend picking a standard and sticking with it.
A resistor with neatly bent legs.
A resistor with neatly bent legs.

While the leads of components can be bent with your fingers, I find that more attractive results are obtained if I estimate the distance between mounting holes by eye, and then bend the leads to perfect 90-degree angles (using needle nose pliers) prior to insertion.

In general, to populate a PCB with components, each component is inserted in the board from the top through the appropriate holes. The component is pulled down to be flush with the top of the board and the leads (tinned metal wires extending from the component) are gently bent outwards on the back of the PCB to hold it in place. This temporarily holds the component in place and readies it for soldering.

Starting the build process.
Starting the build process.

The soldering iron is momentarily touched to heat the solder pad on the board and the lead evenly and at the same time. Solder is applied to the hot pad and lead, which liquefies and creates a small, neat mound. If done properly, the solder cools to a cone shape and hardens to encompass the pad and hold the lead securely. The excess lead beyond the solder is then trimmed off using wire cutters.

Use an old toothbrush and rubbing alcohol to remove flux and clean the board once soldering is completed.
Use an old toothbrush and rubbing alcohol to remove flux and clean the board once soldering is completed.

This is just a quick overview of the soldering process, and there are many excellent in-depth tutorials available if you are new to soldering or want to learn more.

The completed PCB.
The completed PCB.

Repeat until all components are attached, triple-checking before applying solder for all components (capacitors and diodes) that have to be oriented properly for polarity.

Starving Student II Order of Installation

The instructions walk the builder through installing (in order):

  1. Resistors
  2. Diodes
  3. Transistors
  4. LEDs
  5. Heatsinks and power MOSFETs
  6. Film capacitors
  7. Electrolytic capacitors
  8. Choke
  9. Input and Output RCA jacks
  10. Power jack
  11. Power Switch
  12. Volume Control
  13. Headphone jack
  14. Tube Sockets
  15. Tube LEDs
  16. Jumpers
  17. Push-button power cap
The green replacement switch and original black switch.
The green replacement switch and original black switch.
The included power switch (black with a blue square shaft) interfered with the hole in the front panel of the case. Pete sent me the new replacement switch (green with a white round shaft) which (still perfectly) fits the PCB and also the front panel. Future kits should come with this new switch.

Power On Test

Before plugging in the tubes, it’s time to do a couple of easy power tests, or as the manual calls it ‘smoke tests’. If you are unfamiliar, ‘letting out the magic smoke’ is a common DIY joke referring to improper connections burning up components.

Once the board is fully assembled, and DOUBLE-CHECKED AGAIN, it’s just about time to plug it in and push the switch. First place the board on a non-conductive (wood, paper, plastic, etc.) surface and plug in the power adapter. Without plugging in the tubes, depress the power button to turn it on and the tube socket LEDs should light up.

Next, use your Digital Multimeter (DMM) and measure the DC voltage between ground and pin 3 on each of the two tube sockets. This should measure between 18.5 and 19.5 volts (this value will be somewhat lower after the tubes are installed).

Everything plugged in and ready to test.
Everything plugged in and ready to test.

If all checks out, find your test headphones. Power the amp off. Insert the tubes and connect the headphones and a source. Utter a quiet and quick prayer to the deity of your choice and power it on. Finally, give it a listen.

Remember to power the SSII off (and I’d suggest unplugging it) before changing the jumper settings between CSS and resistor.

If there are any issues encountered, it’s almost certainly a problem with the soldering of one or more components. Since you carefully quadruple-checked the orientation and positioning of all components, an open joint or shorted leads are the most likely candidates. Almost all electronic troubleshooting recommends reflowing and redoing all solder joints carefully, one by one. Joints should look like tiny volcanoes, not blobs or balls.

Case Assembly

Assembling the case is purely a matter of lining things up and tightening screws and nuts. The case is very high quality and lines up perfectly. If things aren’t working out, double-check orientation and carefully start again.

The instructions walk the builder through installing (in order):

  • Board standoffs
  • Top plate and sides
  • PCB
  • Bottom side panel nuts
  • Rear panel
  • Front panel
  • Headphone jack nut
  • Volume knob
The top screwed to the side.
The top screwed to the side.
The case is not symmetrical. The rear of the top panel sticks out the back of the chassis slightly. The sliding nuts to hold the top and bottom work well, but it will take a little jiggling to get everything to line up and match the holes.

Starving Student II Upgrades

There are few potential upgrade options when assembling the SSII PCB, and I’d recommend restraint. This is intended to be a low-cost kit, and subtle or questionable upgrades for much more money is rather beside the point.

Additionally, the kit includes high-quality components from reputable suppliers. However, DIYers tend to be tinkerers, so there may be some room for swaps to be made.

Most deviations from the stock build will require a custom chassis.

Capacitors

The default capacitors are all very good Nichicon electrolytic caps and Wima polyethylene film caps. It may be difficult to find better capacitors that will fit on the PCB, especially if the diyAudio chassis is used.

Wima film capacitors on a partially assembled board.
Wima film capacitors on a partially assembled board.

Power Supply

A linear power supply can be used in place of the suggested switching power supply, “…assuming it has reasonable filtering and/or is regulated so that it doesn’t have a lot of 120Hz output ripple. 120Hz ripple will probably cause more audible artifacts than the switching regulator ripple.” – Pete on Head-Fi

RCA Connectors

The stock RCA jacks are basic non-gold-plated versions. Off-board mounting will require separate insulated connectors and a custom case.

The back panel with RCA and power connections.
The back panel with RCA and power connections.

Volume Control Potentiometer

Although the volume control on the SSII is small and inexpensive (typically a recipe for poor performance)I found it to have reasonable channel balance and be relatively free of noise. This is a great improvement on the stock potentiometer included in Pete’s NuHybrid kit.

Starving Student II Performance and Measurements

I’m happy to report that the SSII achieves a balance between gain and power. All too often I find desktop amps either are unable to deliver enough power for difficult to drive headphones or have far too much audible hiss (any hiss is too much hiss for me) when paired with highly efficient IEMs.

Impressively, the SSII maintains a great balance. It’s really got sufficient power to drive most any full-sized headphones but maintains a quiet background for efficient IEMs. It works well to easily muscle any of my full-sized headphones including the power-intensive Beyerdynamic T1 (600 Ohm, 104 dB) and (Fostex T50RP modification) the MrSpeakers Alpha Dog (50 Ohm, 98 dB).

The T1 or Alpha Dog achieves a loud listening volume at approximately ½ on the SSII’s volume control. It has plenty of power on hand for any of my full-sized headphone needs, yet it retains a silent background when used with efficient IEMs like the Mee Audio MX4 Pro (12 Ohm, 103 dB) or the KZ ZS10 Pro (30 Ohm, 111 dB).

Without being able to dial back the input signal, the very efficient ZA10 Pros have a tiny usable volume range on the SSII. A loud listening level is achieved at approximately 1/8 on the SSII’s volume control. It would be easy to accidentally damage either the IEM or your hearing unless you are careful.

Starving Student II Frequency Response

The diyAudio page includes a pack of 12 SSII graphs and measurements, for both CCA and resistor modes, driving 30 and 150 Ohm loads.

Resistor load frequency response 30 ohm load.
Resistor load frequency response 30 ohm load.
Resistor load frequency response 150 ohm load.
Resistor load frequency response 150 ohm load.
CCS load frequency response 30 ohm load.
CCS load frequency response 30 ohm load.
CCS load frequency response 150 ohm load.
CCS load frequency response 150 ohm load.

All measurements show relatively similar results and the frequency graphs are remarkably flat. The worst-case low-frequency response is -3dB at 20Hz for a 30 Ohm resistor coupled load. The high-frequency HF response drops over 20-30kHz for all.

In personal listening, I have to concur. I experienced no audible anomalies with CCS or resistor loading testing with a variety of headphones.

Tube Amps and Harmonic Distortion

This section is a standard inclusion in my tube amp articles.

Tube amps are not theoretical “ideal” amplifiers that simply apply voltage gain. With a tube amplifier, it is important to understand that harmonic distortion is part of the intended sound signature. Harmonic distortion may be defined as the presence of frequencies in the output signal that are not present in the input signal. These frequencies may be even or odd.

Single-ended circuits are asymmetrical, so they tend to create more even harmonics, while push-pull circuits are symmetrical, so they tend to create more odd harmonics.

Harmonics may be seen at 2nd, 3rd, 4th, etc levels. Higher-order harmonics tend to be more audible (and thus less desirable) because they are further from the original frequency. 7th order harmonics and above are considered very undesirable as they tend to be harsh-sounding.

Even harmonics are typically considered more pleasant-sounding than odd harmonics. The desirability of low-level, even harmonics is why 2nd order harmonics are often touted as “what you want” with a tube amplifier.

At first thought, that seems bad! Imagine… making up signals that weren’t there originally. But harmonics themselves aren’t necessarily a bad thing. In the real world, all musical instruments, even our voices, have harmonics. These are sometimes called overtones. In fact, certain harmonics may even be pleasing to the listener and make listening more pleasurable.” – FiveFish Audio Blog

Of course, personal preference and the music listened to, may lead one to prefer the sweet, tube-like characteristics of even harmonics, or the more-detailed, brighter sound of odd harmonics. Lower-order harmonics tend to mask higher-order harmonics, but higher-order harmonics tend to be more audible, and as we noted above, less pleasant sounding.

So a typical “good sounding” tube amp will try to minimize total distortion, and make sure the higher-level harmonics are at a smaller amplitude than lower-level harmonics (typically in a stair-step pattern downwards).

Harmonics are measured using a Fast Fourier Transform (FFT) graph which displays a signal both in the time domain and the frequency domain. The harmonics of a signal’s frequency appear at higher frequencies than fundamental frequency on the FFT graph.

Starving Student II Sound Quality

“A little even distortion can be a good thing, as long as there’s not too much.” – Pete (In a personal email exchange)
Resistor load Fast Fourier Transform (FFT) graph.
Resistor load Fast Fourier Transform (FFT) graph.
CCS load Fast Fourier Transform (FFT) graph.
CCS load Fast Fourier Transform (FFT) graph.

The SSII output displays traditional single-ended triode amplifier characteristics with strong 2nd order harmonics and subsequently smaller higher-level harmonics. This is somewhat stronger with the resistor loading, but the CCS graph displays similar results.

When I asked Pete what he wanted the Starving Student II to sound like, he told me “…like a single-ended tube amp. Think 300B or 2A3.”

Now here’s the thing. I find the SSII to have a very clean and vibrant sound, with little to no background noise. Very similar to decent solid-state amplifiers I’ve used.

Perhaps a little too similar. If anything, I find the SSII somewhat less ‘tubey’ sounding than I expect. Resistor load is my preference (over CCS) but honestly, the sound is not dramatically different between modes.

Remember, the SSII is a hybrid and uses solid-state components in addition to tubes for amplification. My preferred sound signature may also vary dramatically from your own. I’ve definitely moved away from the more sterile sound of solid-state amplification.

The SSII tends to feel bright and I found it borderline a bit sharp with some headphone pairings and song choices. Electronica through the Fostex planar headphones was not a great match. I asked Pete what his headphone suggestions are, and it jives pretty well with what I experienced.

“I usually don’t attempt to recommend any particular headphones, as they all sound very different, and what I might like, others might hate. This amp isn’t too picky about what it’s driving. As for me, the old AKG K1000 is near the top of my list. Also Focal Elear, and in general I like the Sennheiser HD600/650/800 family. For some reason, I’ve never been a big fan of the planars.” – Pete (In a personal email exchange)

If I set my expectations for super warm harmonics aside, there is much to like about the SSII sound quality. Clean, clear, and transparent with plenty of power. Equally adept with my perennial favorite Sennheiser HD650s and the newest IEMs.

Conclusion

The Starving Student II kit from diyAudio is a pleasure to build. It’s got everything that a novice DIYer could hope for: one-stop ordering for all parts, excellent instructions, and an active forum to ask for help. Not to mention, the SSII is a proven design from one of the foremost names in DIY tube amplification and design: Pete Millet.

Simple good looks.
Simple good looks.

All the variables have been streamlined to simplify the build experience. Depending on your level of skill, this may be exactly what you are looking for, or you may find it somewhat limiting. The superb enclosure is, on one hand, perfect for the kit, and on the other hand, limits what modifications or upgrades can be done.

The SSII may be a perfect first foray into tubes for solid-state amplifier aficionados. Or it may not capture the tube experience enough. It all depends on your point of view.

Don’t get me wrong, the SSII is a great amp. It’s got many happy customers and excellent reviews. It just wouldn’t be my first recommendation for someone looking for that exalted warm distortion of tube amplification (or the illumination of tube glow).

The sound of the SSII matches the blue LED tube lighting to some extent. A bit too clinical for my personal tastes.

The SSII certainly doesn’t have the look or feel of a cheap product. In no way does it project the “I could stop working at any moment” vibe of many DIY projects. The entire experience is clean, high quality and no-nonsense from beginning to end.

If you want an affordable project or tube amp that you can build and immediately use with a variety of headphones (and with minimal fuss) then the SSII should certainly be considered.

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