[nlitworld]

 So a while back I decided to build a tube amp for my system. Having success with Tubes4HiFi kits in the past, and seeing lots of good reviews on the punchy little ST35, I decided to jump on that and build from the ground up. I already have an EL34 amp for bigger power, so a little EL84 looked like a lot of fun. Circuit design appears to be same as the Audio Note EL84 kit, so I know the design is solid.

Since I was already going to build, I decided to go full regalia and build from scratch having only purchased pcb and transformers. Everything else I would source and go as high as feasibly possible. This involved oversize custom chassis (with thick 1/8" aluminum top plate for reinforcement) exposed tubes, exterior mounted transformers and a massive Hammond choke in the power supply. I decided to mount everything external due to the size of capacitors used in the build. There are 3 100uf caps in the power supply, so why not make them giant Obbligato film oil caps? It'll probably fit... Everywhere else got a minimum of Solen or Audyn mkp caps except the required 470uf electrolytic caps which gets the Audio Note treatment. Coupling caps are Duelund tinned copper. Wiring will all be VH Audio, connectors KLE rca and Tube Connectors. Top it off with Amperex and Siemens tubes, it should be pretty rad when it's all done. I'm still legitimately hoping everything fits inside the chassis easily. When I'm done, it'll end up close to 40lbs. 

Just thought I'd share the fun of the process as I finally have all parts together and holes drilled in chassis. Next step is prep and paint chassis, then bust out soldering iron. Hoping to make some progress over Christmas break.





Also big shout out to Dan @ Tubes4HiFi. He was super helpful filling in the blanks for parts list questions. Not surprised since his predecessor Roy was the same way.

Will update with progress photos as we go along.

[JakeJ]

Thanks for posting this, I will be following along. 

Could you share your component BOM?  I think I see Jupiter and Mundorf caps?  And it would appear you have found different transformers than the basic kit?

[mresseguie]

Cool stuff! I'm following.

Off the wall question for you....there are six fans  What do you do with six fans? [I know. Silly question.]

[FullRangeMan]

IMO the output tubes are too close each other unless you live in Canada.

[opnly bafld]

 
Enjoy the build, it will be a fine sounding amplifier when done.

IMO the output tubes are too close each other unless you live in Canada.

No problem, he has plenty of fans as pointed out by mresseguie. 

Small tubes like EL84 don't need a lot of space for heat, many vintage amplifiers with 6BQ5 tubes have worked well for decades with the tubes close to each other, OPTs, etc.

[nlitworld]

Could you share your component BOM? And it would appear you have found different transformers than the basic kit?

Let me get my notes together and I'll post full BOM. Transformers are all Antek with covers, but the giant black box is the Hammond choke for power supply filter. Needed 5H 350ma which meant that 10lb behemoth was kinda the only easy option. Seeing it in person is just comical.

Off the wall question for you....there are six fans  What do you do with six fans? [I know. Silly question.]

Not silly question at all. There are actually 11 fans in the garage for basically turning it into a paint booth. 2 fans in back of garage, 9 along the door to pull air out, and crack the side man door for air inlet. My day job is selling automotive paint, so weekend hobby is painting silly stuff super wild fun colors. Bicycles, helmets, computer cases, SPEAKERS, dog show prizes, etc. Currently painting dog water buckets for Albany dog show prizes and raffle items.

IMO the output tubes are too close each other unless you live in Canada.

Yep, I agree, except that's what is on the circuit board so that's where they stay. That is a major reason I made tubes exposed though. Not competent enough with circuit design and building to make things point to point yet. Also, I might as well be in Canada since I'm on Pacific coast about 4 hours south. Same rainy cold weather most of the year. Also why I built out a modded Douk amp for summer listening when it does get hot.


All in all, I'm excited to build this out, and will post up as we go. 

[JakeJ]

Dood!
You gotta post some photos in Eye Fidelity of your paint work! Start a thread and others that have art hobbies could post stuff too.

Sorry, OT, now back to our previously scheduled amp build thread.

[Jon L]

EL84 is one sweet tube.  Do yourself a favor and stick a 4-pin XLR socket in front to power some sweet planar headphones!  Additional transformers/resistors may or may not be needed depending on how difficult-to-drive the planar headphones are. 

[poseidonsvoice]

Let me get my notes together and I'll post full BOM. Transformers are all Antek with covers, but the giant black box is the Hammond choke for power supply filter. Needed 5H 350ma which meant that 10lb behemoth was kinda the only easy option. Seeing it in person is just comical.

...

All in all, I'm excited to build this out, and will post up as we go. 

Looking forward to your build docs, thanks for starting the thread!

Best,
Anand.

[Tyson]

That's the amp I have!  Great sounding amp, you're going to love it.

[S Clark]

I'm also a fan of that  tube.  Years  back Gary  Dodd built me a pair of integrated mono amps using old Eico chassis and iron.  They were really sweet on vocals if not the tightest on bass.   I need to pull those out and hook up my Altecs to them this winter.   

[FullRangeMan]

I admire those who have the skill to build a kit.
Its not my case.  Congratulations.

[nlitworld]

Ok guys, build list is kind of a slog and overinformation, but here goes. Everywhere necessary, all caps, resistors and tubes are matched pairs just for OCD peace of mind.

Signal section:
Amperex 7643 input tubes
Siemens E84L power tubes
Duelund Cast PIO tinned copper coupling caps
Audio Note Kaisei in bias circuit
Solen PB for one of the 4.7uf off input cap. Connects pin 3-7?
Takman carbon film resistors in signal path
Takman metal film in ground path
Amtrans AMRG for all 2W resistors
Silver mica caps for itty bitty pf size and feedback circuit

Power Supply section:
Vishay fast recovery diode
Audyn Q4 MKP caps for the 22uf and 10uf in filter
Obbligato 100uf 500v giant film caps in filter
Mills MRA5 for all 5W resistors
Takman metal film for all 1W and ¼W
Hammond 193 choke (5H350mA)

Chassis:
Hammond 17x13x4 chassis that I sliced the roof off and glued 1/8" aluminum sheet to top. Will likely paint a fun color to boot.
KLE rca plugs
GR Research tube connectors
Furutech FI06 iec inlet
HiFi Tuning Supreme fuse
VH Audio Pulsar shielded wire for input
VH Audio unicrystal 18g for any other required wire
All black hardware to keep it looking cool
Lastly some Vibrapod feet to keep it squishy.

I plan to do a couple other tweaks along the way, but that shouldn't really change anything. My plan was to splurge as best I could while still not maxing out a c/c. I still have a mortgage, so always have to keep it in check. Mostly I wanted to try building one of these that is better than Tyson's, which is a tall order. In all fairness, it's Tyson's review that sealed the deal this was the kit to build. Gonna be good fun. I'm so excited to start on this next week.

[planet10]

E84 is a great output tube. We have built both SE and PP EL84 amps. The PP is in the same league as my SIT-3.

The circuit itself is more important than wxotic bits. That is MIA in your post.

And you have some i;’d  stay away from. Danny Richies connectors for instance. And 18g for internal wiring?

dave

[Tyson]

My EL84 amp is probably my 3rd favorite amp of the ones I own right now (about 13 total including a couple of SS amps).  And this amp is going to be better than mine!  Better parts equals better sound. 

[FullRangeMan]

My EL84 amp is probably my 3rd favorite amp of the ones I own right now (about 13 total including a couple of SS amps).  And this amp is going to be better than mine!  Better parts equals better sound.

What are your first and second amps ?

[nlitworld]

E84 is a great output tube. We have built both SE and PP EL84 amps. The PP is in the same league as my SIT-3.

The circuit itself is more important than wxotic bits. That is MIA in your post.

And you have some i;’d  stay away from. Danny Richies connectors for instance. And 18g for internal wiring?

dave

Yes, I could and should have lead with this circuit is same as the Audio Note +/- a little parts choice. All in all, it should have good bones to build off of.

As to parts list re: tube connectors, I chose those because every time I've used in an amp build or speaker, they've jumped up in clarity and impact on par or better than the KLE and WBT I've tried before. Add in the zero maintenance and lower cost, it was a no brainer.

Also curious Dave, is there a bad thing about 18g solid for internal wiring? I have the shielded wire for input signal, so really the only things off the other wiring might be a ground wire, the front panel led or extra length for those giant power supply capacitors. Anything with a +/- power would be a tightly twisted pair run as far away from sensitive components as possible. If there's one you think is better, I'd be curious to check it out.

[Rusty Jefferson]

Congratulations on the new amp/build. Interesting that they supplied it with (or you chose?) toroidal output transformers rather than EI type. Is that a cost consideration or design preference? The OT has a larger effect on sound quality than output tubes with transformer coupled amplifiers (in my experience).

[nlitworld]

Transformers were spec with the ST35 kit. Not sure when they swapped to toroidal but I'll roll with it for now. Honestly I don't know enough yet about specs to start swapping transformers. I've heard several times that is a huge part of the sound though.

[nlitworld]

Alright Rusty,
Your comment got me thinking, if I were to upgrade OPT what would be a good option? Like I said, I'm not really knowledgeable enough on transformers to know what's what. I'm sure I could find something with similar specs but if you know of something better sonically that isn't hateful pricing, I'll give it a look.

Current OPT is Antek MP-25W76

Product Brief:
Output power                     25 Watt
Turn Ratio                          30:1
Ultra Linear tap                40%
Primary impedance           7.6K ohm
Primary DC resistance      191 ohm
Output impedance             4 & 8 ohm
Output DC resistance        0.3 & 0.5 ohm
Max DC plate current       125mA
Frequency response          10Hz - 20KHz
Suggest Tubes                   807, 5881, EL34, 6L6, 6V6
Weight                              3.5lb
Dimensions                      4.0" d x 2.0" h