Pass DIY F5 Amp Build

[MrBoat]

Here's something of novel curiosity. It's a Korg 6p1dual triode (vacuum tube). I intend to make a preamp with it at some point. It's featured in another diyaudio kit by Nelson Pass.

Cool stuff, at any rate.

KORG Nutube | A new vacuum tube which puts vacuum fluorescent display technology to practical use

Nutube, similar to a conventional vacuum tube, has an anode grid filament structure, and operates exactly as a triode vacuum tube. Also similar to a vacuum tube, it creates the same characteristic rich overtones. By applying their vacuum fluorescent display technology, Noritake Itron Corp., a...

korgnutube.com

 

[Pogre]

What a cool build boat! Nice to see you man! It's been a while!

 

[Mikado463]

Nicely done, I'm enjoying your progress !

 

[MrBoat]

What a cool build boat! Nice to see you man! It's been a while!

Mostly I just listen to what I have built/collected over my time here. After awhile, that's what's left to do with it all. Besides, I am solidly a 2 channel listener and found a relative sweet spot/method to all of that, room be damned, and it became more about the music than the gear itself.

Basically got out from under information overload, 2nd guessing everything, and just listen a lot now. Found out the biggest problem I was having with what I was trying to do was, I just wasn't turning it up loud (truth) enough.

 

[MrBoat]

Nicely done, I'm enjoying your progress !

I am taking my time, as time allows. May change a few things yet. It's all a lot of fun.

 

[Mikado463]

Besides, I am solidly a 2 channel listener and found a relative sweet spot/method to all of that, room be damned, and it became more about the music than the gear itself.

Truer words have never been said !

 

[MrBoat]

It's slow going but, I manage a little each night. Wasn't happy with the previous dimensions, once I got everything set up in front of me. Wanted more air flow on the interior so I expanded the width another 1.125" per side. In the mean time, I bought some smaller welding electrodes/filler rod to do these smaller types of joints with at lower power and it made life a little easier.

A tedious affair. All of the pencil lines connected where they were supposed to, but I could not use a center punch to mark them with. This many punches would have expanded this metal significantly, so I basically just 'hope'n poked' with a bullet point small bit at first, followed up with the larger, after. Yes, that means I had to drill all these twice. And then treated them twice again with a countersink bit. No, the holes did not all land precisely on their marks. By about 1/4 of the way done, it was making my eyes water so it gets what it gets.

Also managed to match up pan, to the tapped holes in the sinks and got some feet under it and the transformer bolt hole drilled.

I could power thru now and get it done but I am making myself stop and think about things a bit. Like: "Hey Einstein, how do you propose to adjust those pots with these big honking power towers in the way now?" lol! Will have to do it with the sinks detached. Thankfully it's something that only needs to be done once. I almost put piano hinge between the sinks and pan so I could open the whole works similar to a book, but I stopped myself.

What also took some more time was I did not have the fasteners I wanted so, I had to order an assortment. They did not come with lock washers though so I still have to sneak those in, at some point. I have all kinds of stainless hardware but most of what I need here is metric, if I don't want to mix and match or remember which it is, some years from now.

ETA: I could either make some small knobs for the pot screws, or make a stubby screwdriver to fit them easily enough, if I so choose.

 

[MrBoat]

Managed to fire off the power supply for the first time, using my dim bulb tester. Everything measures as should. Will let those fat caps bleed down overnight before getting back to it.

 

[slipperybidness]

Managed to fire off the power supply for the first time, using my dim bulb tester. Everything measures as should. Will let those fat caps bleed down overnight before getting back to it.

I always use filter cap bleed-off resistors! That tends to be the overall safer approach on large caps. You could also just do it manually with some resistors, rather than wait for them to discharge on their own.

I know I have at least 1 commercial amp that does not have bleed off resistors on the filter caps. That is valuable info to know before working on a power supply!

 

[MrBoat]

I always use filter cap bleed-off resistors! That tends to be the overall safer approach on large caps. You could also just do it manually with some resistors, rather than wait for them to discharge on their own.

I know I have at least 1 commercial amp that does not have bleed off resistors on the filter caps. That is valuable info to know before working on a power supply!

There is bleeders (in between the two LEDs) in it, but it's a new circuit without a load connected and I was in no hurry anyway. It was end of the night, too, so I was done for the evening. You can visibly see it bleeding off with the meter connected but it is slow going without a load on it. A couple hrs would likely well be enough without discharging it myself.

Thank you for the heads up, regardless.

 

[MrBoat]

Just ordered the boards for Honey Badger.

 

[MrBoat]

I am new to Euroblock terminals. Where I left off, we were using wire wrap connections, which I still prefer, when it comes right down to it. Still, I was not thrilled with stuffing stranded wire in a hole. There is always one or two that seem to pull away from the pack and end up outside the actual connection point. At least is usually the case when the AWG is really pushing the limits of would-be accommodations for it. After about two times of feeling the wire brush effect going in, I opted to put ferrules on the wire instead. The crimper actually squares the ferrule and it ends up being a good match to the squared terminal.

It also offers some strain relief.

 

[Benni777]

Wow, this is impressive!!!! I wish I had the know how, patience, tools and money to do this myself. Kudos to you, Kudos...

 

[Benni777]

Was this a kit buy or did you have to find each part separately?

This is the second one. The first one I built I never really got time to build a proper chassis for. My buddy has it powering his Klipsch RF-7 speakers. I was given a rather large box of matched P & N channel JFETS that are supposedly quite good, albeit NLA. At any rate, the man that has gifted me the use of them also kicks whatever other associated parts I might need if he has them in stock. Only stipulation being, he does not want me to sell or give away the parts. If I ever quit being interested in electronics, he will have them back. I do welding for him, occasionally over the last 25 years to now.

Also, I don't want just another Euro styled, or Chinese type universal chassis. Definitely don't want another black, blue LED amp either. Thinking a hand built aluminum chassis with wood trim. While I am waiting for the rest of the components for the power supply, I have time to think about it. Meanwhile, I have the board stuffed except for the MOSFETS. Will get to drilling and threading the heat sinks this weekend. That's the only thing I am really reliant on is factory made heat sinks. I have thought about making my own, or perhaps even liquid cooled, for having the tooling and experience to make those, I suppose. Maybe something unique will occur to me in the future. There are other amps I want to build, as well.

Here's the boards for each channel. Some time was also spent reading the tiny printed values of those Dale resistors and testing them beforehand.

The heat sinks, which roughly measure 12" x 6.5" x 1.5" are without any holes for the boards. I think when I got these, diyaudio store was out of this particular size so I ordered elsewhere. Diyaudio's sinks has their proprietary, universal mounting scheme.

Here is the PSU board awaiting parts. I thought I had bought them already, but I was mistaken. I am just going for the +/-25V supply for the 25 watt version of the F5. I have higher sensitivity speakers that perform even with 3-4 watts. I may build the 50watt (F5 Turbo) at a later date.

Was this a DIY kit with everything, or did you part this out? What is the cost on something like this? This is crazy impressive. Assuming you'd need to be well versed in electrical engineering to do something like this?

 

[MrBoat]

Wow, this is impressive!!!! I wish I had the know how, patience, tools and money to do this myself. Kudos to you, Kudos...

The internet is the university of everything, right at our fingertips! Anything, anyone wants to become is here. I save up my pennies until I have enough. I did not buy the whole kit at once. I have been collecting tools since age 17. At least one/week.

I bought the boards first. Parts kit was out of stock at the time. Some amps I source parts myself from a BOM. I had to with the power supply portion of this build. Also had to source some of the special transistors that have been out of production for some time. I will have around $400 into it spread over about 2 years. It doesn't feel like I have spent anything on it. I just woke up one day and all the parts had accumulated.

 

[Benni777]

That's awesome, I'm going to look into this.

 

[slipperybidness]

The internet is the university of everything, right at our fingertips! Anything, anyone wants to become is here. I save up my pennies until I have enough. I did not buy the whole kit at once. I have been collecting tools since age 17. At least one/week.

I bought the boards first. Parts kit was out of stock at the time. Some amps I source parts myself from a BOM. I had to with the power supply portion of this build. Also had to source some of the special transistors that have been out of production for some time. I will have around $400 into it spread over about 2 years. It doesn't feel like I have spent anything on it. I just woke up one day and all the parts had accumulated.

To be fair, your labor doesn't come cheap!

I understand the labor of love, so it's a moot point. But, the opportunity cost is still there.

 

[panteragstk]

To be fair, your labor doesn't come cheap!

I understand the labor of love, so it's a moot point. But, the opportunity cost is still there.

Or skill. Nice to see the skill and technique other folks out there have. Projects like this are always fun to follow.

 

[Eppie]

I was looking at some of the Pass kits last year: turntable pre-amps and stereo amps. Some interesting designs. Wish I had time to try a build but need to complete a restoration on my Ampeg bass amp first. Beautiful welds on that tray! I'd have to have a welder friend do that quality of work for me.

 

[slipperybidness]

@MrBoat
I have likely shown you this link before, but I have been really looking at the builds from the Signal Transfer Company! These are the designs of Douglas Self, he has many commercial designs, and several books on audio electronics construction. I don't think he has any of the crackpot designs like Pass does

The Signal Transfer Company

The Signal Transfer Company, audio, preamp, power amps

www.signaltransfer.freeuk.com