First tube amp build: Fender Deluxe AB763 style amp (no reverb).

[mikepukmel]

You'll want to run a vacuum hose near any dremeling, the board dust is nothing you want to inhale.

One of the standard power cable nylon strain reliefs is Heyco 6NP3-4, I get 'em by the 100 from Mouser. Also, your local Home Despot typically has a selection, you could bring in your chassis, find one that fits & buy that.



I thought you might have a mid Hudson connection. A couple decades ago (80's) there was a reporter for the local paper named Pukmel. First name I forget - Gary? - so did his editor. He had a weekly column, said when his editor wanted to see him, he just yelled out "PUKMEL ! ! !"

Poughkeepsie still draws river water for public use. They went the wrong route on "purification" some years ago, put in a system that added some half ass chemical, chloramine, that other cities had previously tried and declared unfit to continue. That's the way things go around here. I'm sure somebody pocketed a fortune on that deal. There's still a standing warning to strictly limit eating fish from the Hudson. Although the river has recovered greatly from its condition 60 years ago (THANK YOU PETE SEEGER ! ! ! ) it's still not safe. And now the Coast Guard wants to approve allowing barges full of crude oil from Canada to use the river as a parking lot while oil futures traders buy & sell contracts on them, IOW make lots of cash for the rich folks while endangering the environment for us normal folks. I'm sure it will get full approval from . . . well that's a matter for another thread so we'll send the rest of it there, shall we.

Thanks for the tip on the Heyco, I will look them up. Yep, (Bill) Pukmel was my dad, started as a reporter when he left the radio business. He was managing editor by the time he left the Poughkeepsie Journal in the late 80's. (I still remember some of the names Jim Shumacher, Whitey Deckner, Bob Niles, Lou Peck, ...) He did have an editorial column and did some cartoons as well. My school friends father worked at the Poughkeepsi water works, and a few other friends from school days as well. yes, I remember one of them getting burned spilling some nasty chemicals on his leg, very lucky he had thick pants on and could get them off in time. Oh no, crude oil up the hudson, after all that it took to get it where it is now? <big frown> yeah, another thread.

[mikepukmel]

After much toil, decided on Nichicon capacitors for the first build As long as I don't blow it up, can always put in pricey ones later. Total bill for all electrolytics is about 11.00 from Mouser (plus shipping). I will tack on the Hammond transformers since they are a Hammond distributor, and prices seem about what everyone else is charging. That leaves the other bazillion parts to buy.

[mikepukmel]

An easy way to come up with a BOM would be to print the schematic and label each component with a letter and number... R1, R2, C1, C2, etc. When you assign it a number, make a note of it in a spreadsheet. For ease of ordering later, make sure to also note anything special about it. "Label | Value | Notes" or something like that. Once you've entered it in your spreadsheet, highlight it on the schematic you've printed out.

I suggest using a spreadsheet because later on when you go to order you can sort the list by the value column and quickly see that you need, say, sixteen 1-meg resistors. I'll typically add a couple columns for, say, "Vendor," and "Vendor Part #" which helps greatly to have in advance. Even though it happens to me every time, it seems I'm never fully prepared for a Mouser order and within 5 minutes of ordering parts I'll remember at least a dozen 5-cent parts that I need. Also with vendor information included, you can make nifty pivot tables.

For capacitors, make sure to get at least the same voltage rating, or better. A lot of coupling caps are rated to withstand 630V - this is fine.
For resistors, make sure to get at least the same wattage (power) rating, or better. If the schematic calls for a 1/2-W resistor, a 1W or 2W will also work just fine.

Also don't forget that you're going to need jacks, sockets, tubes, the tremolo optoisolator "bug", transformers, knobs, a footswitch, wire... all that stuff.

For vendors of general electronic components, I tend to use Mouser. It can be tricky learning how to navigate their site, but once you get the hang of it, it goes quickly. One nice thing about Mouser is that they include the value in the part number, so once you find a resistor you like in 220k, you can just replace the "220k" in the part number with "100k" and get the same resistor in a different value.

You're probably going to need to use multiple vendors though, and someone like Antique Electronic Supply is a decent place to start.

Building a clone amp is a balance of frustration versus cost. Or any amp, really; but with a clone you have the option of a fully compiled kit with all the parts and maybe even instructions. Simple to order, but higher cost. On the other end, you can spend hours hunting down each and every little part, and while your hair might fall out, at least you saved some money.

For a first build, you might want to save your "frustration budget" for actually building the thing. I'd recommend building a Champ kit, because they're great and quite simple. Or buy a little 5W tube amp (there are a bunch out there) and experiment on it. Oh yeah, look up the "AX84 P1 Theory Document" - that's a good start on learning what does what.

Oh man, I didn't realize how much toil I would go through sourcing parts! Yes, I did start with the firm intention of building a single ended amp, few parts, simple build easier to diagnose, etc. Firm. Absolute. Then, I thought, meh, you know Mike, it doesn't have a tone stack. Gotta have a tone stack. OK so what's the smallest amp that has a tone stack. Bass, Treble. that's all I need. Princeton, that's the build for me. Two output tubes, 10x more complex than the Champ, but ... has a tone stack. Then, I thought, you know Mike, you never really loved the sound that blackface princeton reverb you had back in the 70's. A teeny bit bigger amp would be better, one with a long tail pair phase inverter. So ... I argued my way the way up to a Twin Reverb clone. No way could I put a 80 to 100 watt amp in my house. Akkk. Then all the way back down to a Princeton again. Then up to a Deluxe. To keep from flip flopping again, I just fixed on a Deluxe after finding a few amp techs on Youtube, that played through the thing, sounded awesome, so hope mine sounds anywhere near that good.

[mikepukmel]

wooh: http://www.tubebooks.org/Books/gray_...tronics_2e.pdf tough to trudge through this one.
Currently reading Merlin's book (awesome). Will get through both eventually.

[eschertron]

wooh: http://www.tubebooks.org/Books/gray_...tronics_2e.pdf tough to trudge through this one.
Currently reading Merlin's book (awesome). Will get through both eventually.

Merlin's book on preamps. Good one. I'm still waiting with bated breath for him to reissue the rest of the series.

Just looking through the TOC for the Applied Electronics text, I had flashbacks to Freshman physics. Big book, not in a year did every chapter get covered. Pick and choose. When you realize you need some of the earlier content (that was skipped) to explain the material you're reading, go back... or use the internet
IOW don't trudge, investigate!

[mikepukmel]

Merlin's book on preamps. Good one. I'm still waiting with bated breath for him to reissue the rest of the series.

Just looking through the TOC for the Applied Electronics text, I had flashbacks to Freshman physics. Big book, not in a year did every chapter get covered. Pick and choose. When you realize you need some of the earlier content (that was skipped) to explain the material you're reading, go back... or use the internet
IOW don't trudge, investigate!

Thanks for the tips. My calculus, especially vector calc, is massively rusted, as is most of the physics I once knew. Very anxious to get into the tube stuff, still on charged particle trajectories and such.
Im alternating time on the Merlin book, as you say its awesome. yeah, hope he gets time to do a power amp book.

[mikepukmel]

Total cost ...

Still just over $1,000.00. Probably will end up in the 1,150 range.

Transformers + cabinet + speaker + tubes, not much can do to get those costs down.
Surprised at how fast the pots + knobs + misc added up.

Got the order list down to 3 orders total:
1) Hoffman - eyelet boards for cap board, bias board, most of the resistors, some caps, tube sockets, some wire.
2) Mouser - major items are transformers and choke. Also ordered a few misc discretes (some ceramic caps, power resistors)
3) Antique Electronic Supply. - Knobs, pots, misc hardware, tube set,

The only thing this doesn't cover is some mounting hardware, and hookup wire. Will probably order wire from Hoffman, but he's out of a few of the colors I want to use.

Thought by now I would be hacking out my favorite Jeff Beck tunes through this amp, but I haven't even ordered most of the parts yet. Hoping it will go together fairly quickly once the parts are in.

Found an awesome site:
https://sites.google.com/site/jmasterschematics/
this guy has redone many of the Fender schematics, READABLE! they are just great. I got a trial of acrobat, and annotated a few of the schematics (Deluxe, and Pro) with part reference numbers on all the caps and resistors and pots, so I can check for errors in my parts order list.

Got some tips from Merlin on reducing blocking distortion and 'farting out' on this amp, since its famous for that.

[eschertron]

Found an awesome site:
https://sites.google.com/site/jmasterschematics/

Excellent link! Probably should figure out how to post this into the schem forum. [pause] Done. http://music-electronics-forum.com/t19518-2/#post453831

[mikepukmel]

Should have done this first (some of you suggested before ), annotated a schematic with part id's, then wrote parts lists from that. Anyway, after hours of misery with a flaky trial version of Adobe Acrobat:

DeluxeAB763Annotated2.pdf

Went back through the web shopping carts Ive been working on for ages, found that the resistors I had in the carts were all low voltage versions. Fixed that. Also, upped the wattage on a few 100k resistors that feed plates, and the 2 dropping resistors on the cap board. Praying for the strength to type in the credit card and click "Submit order". today, so that at least I can get the pots, and tube sockets and transformers bolted in, and main board soldered up by next week.

[mikepukmel]

Questions for the gurus: The smoothing electrolytic cap right after the diode on the bias board, is 25uf in the old (ab763) schematics. This cap value was raised a few times by CBS, in later versions "to reduce hum". I think the final version was 70 or 80uf. The GZ34 has a max capacitance rating of something like 60uf, but since this isn't inline with the GZ34, is it safe to use a larger cap here, 80uf or 100uf, whatever I can find?

In some later amps, all of the 100k resistors feeding the anodes in the preamp are higher wattage. Is it safe to up the wattage on these resistors, would this increase noise or cause some other problem?

The early amps, by the chassis images I could find, have a nice brass sheet under the pots that is bent to sit in the chassis, and heavy buss wire is soldered from this plate to ground points in the circuit on the fiberboard. I have read that the 'dissimilar metals' issue between the brass sheet and steel chassis caused corrosion in some amps. I have found thin sheet brass with teflon or some other insulator on one side. Just placing the teflon side against the steel chassis would make a very nice big capacitor, but what if I took my big weller and ran a few big solder beads right at the edge of the brass plate to the steel chassis to short the unintentional capacitance between this plate and the chassis would this work?

[Dave H]

The smoothing electrolytic cap right after the diode on the bias board, is 25uf in the old (ab763) schematics. This cap value was raised a few times by CBS, in later versions "to reduce hum". I think the final version was 70 or 80uf. The GZ34 has a max capacitance rating of something like 60uf, but since this isn't inline with the GZ34, is it safe to use a larger cap here, 80uf or 100uf, whatever I can find?

Yes, that's OK. The bias tap is rectified by the diode not the GZ34.

[mikepukmel]

Thanks Dave!

[mikepukmel]

preventing oscillation, instability, etc in new amp builds

I have been reading up, trying to understand causes of parasitic oscillation, and instability in tube amps. Lead dress comes up often. Bad tubes, bad discrete components, bad solder joints, bad shorting jacks. The article link below, a nearly open electrolytic cap caused problems that would be very difficult for me to diagnose on my own.

So, we should measure the values of all of the components, the best we can, before installing them in a circuit?

Amplifier Stability

The last bit on the article, the writer was diagnosing some problems with the amp, and found one cap was far off spec, nearly open ckt.

[eschertron]

In some later amps, all of the 100k resistors feeding the anodes in the preamp are higher wattage. Is it safe to up the wattage on these resistors, would this increase noise or cause some other problem?

From what I've read, higher-voltage-capacity resistors will have less thermal noise than their lower-voltage-rated cousins, other things remaining equal.

[eschertron]

So, we should measure the values of all of the components, the best we can, before installing them in a circuit?

My hope is that components recently purchased from reputable sources will match the values printed on the components. However, it's not a bad idea to verify the values of the components prior to installation to find grossly failed or mislabeled parts. I'm thinking primary component ratings, anyway. I don't have an ESR meter and so could not test my e-caps for that, for example. The one good reason I can think of for taking these readings (and logging the evidence!) is when the circuit does not work as expected and a component is suspected that is impossible to measure in-circuit. May save some de-soldering time?