Basic questions from a complete novice

[Jack Sparrow]

I'm hoping to build my first amplifier. I have some hobby experience with small electronics and hope that I can build a small amp for home use. I've been studying schematics and reading all I can find about DIY amp builds and I have a few questions I hope you won't mind answering.

I gather that Sprague Orange Drops are the capacitors of choice for a lot of folks. I see that most or all of that line has radial leads. Yet most pictures I've seen show that the majority of caps are axial. So are Orange Drops only used for the smaller caps or am I missing something?

On the fender schematics, I see some caps marked in pF and others with only a number value. Would those be in Farads? Caps marked like 25-25 would be 25F caps with a 25V rating?

What do the numbers like 2-35 and 0353 on some pots mean?

I want to build an amp in the Tweed Deluxe style but with reverb. A Deluxe Reverb in that style of cabinet, stained, no tolex covering would be nice. The length of the chassis can be 18-19" but the space for the top-mounted controls would be reduced to about 12" which isn't a lot of room. I thought about possibly making the chassis deeper so the controls can be stacked with one channel "above" (or more like in front of) the other. Another possibility is that of using smaller pots and knobs to put the controls closer together. Has that been done? Or is there some reason that's a ridiculous idea? My fallback is a Princeton Reverb but I like having two channels.

Thanks for getting me started in the right direction.

[Jack Hester]

I'm hoping to build my first amplifier. I have some hobby experience with small electronics and hope that I can build a small amp for home use. I've been studying schematics and reading all I can find about DIY amp builds

Hello, Jack -

I made my return to tubes starting about 3 years ago, after being away from them a very long time. I had the same aspirations with building either a 5E3 or 5F6-A. Then, I decided to build a 5C1 Champ. Not because I particularly liked that amp. Mainly because it was simple and all octals, which I love. I experimented with other simple stuff, but the 5C1 was my first scratch-built amp. And, it was a great success (no cabinet, just chassis). Learned a lot from such a build. Though I built it on a turret board, it would make an even simpler point-to-point build. I also built a 5C2 Princeton, just to have something with a tone control, as the Champ had none. It too was a success. And, I used cheap components on these builds, as I was honing my skills as economically as possible.

Anyway, flash forward to now. Here's a project that I just completed in an old un-named PA amp chassis cabinet:





This is the same amp in it's trashed condition, when the seller did not follow my instructions as to how I wanted it packaged:



The finished amp sounds really great, with each channel having wonderfully different voicings. The tone stack is really simple and has a fine, rich tone range.

All this being said, I'm still a novice builder and will probably remain so, as my old brain just can't soak it up like it used to. But, I take good notes, so that I don't have to reinvent the wheel. By the way. A 5E3 and 5F6-A could be considered relatively simple builds compared to this project. This one was easy, in the manner that I built it.

I completed the power supply, and tested. Then, I completed the power amp and phase inverter. Once proven as functional and quiet, I moved on to the 2nd gain stage/Cathode follower and tone stack. Same testing. Then, Channel 1. Again once this one was proven, I built Channels 2 & 3, as they were in the same dual triode tube. Lastly with help from Mark (MWJB) on my negative feedback (NFB) and values for resistors on my PI, I added a 3rd gain stage using the second triode in my PI. Other than cleaning up some hum issues, this is one fantastic sounding amp. It's great to have people like Mark and others, who have the knowledge base needed to make your build(s) simpler.

Now that I've been so wordy, and have not answered any of your questions, I'm hoping that you enjoy the ride as much as I have. Nothing like a project exceeding your expectations. That's the best encouragement there is.

Jack

P.S. - On the schematics, when you see just a number value for a capacitor, it is typically an indication of microfarads. 25-25 being 25 microfarads (µf) with a voltage rating of 25 volts. Also, I used really good components on this build, though no Orange Drops were employed.

[Jack Sparrow]

Hello, Jack -

On the schematics, when you see just a number value for a capacitor, it is typically an indication of microfarads. 25-25 being 25 microfarads (µf) with a voltage rating of 25 volts.

I'm glad I asked that question before I started.

My story is that back in the day (I'll be dating myself here), I had a brand spankin' new SF Bandmaster. 1968, I think. I used that and a second one for a long time as a teenager. Back when louder was better. Along came life, a wife and kids and I parted with the amps and most of my equipment, though I do still have a pristine condition Vox Invader. No regrets but I always said I wanted another Fender amp. I was thinking Twin Reverb but I really don't need that. I play at home, just getting back into guitar after a long time away. Mostly acoustic but I'd like to add pickups to a couple of those guitars and maybe break out the Vox. I think the Deluxe Reverb AB763 will give me all the power I need and maybe the Princeton AA1164. I'm sure there are better amps made specifically for acoustic guitars, but this will satisfy my desire for an old Fender, too. Yeah, I could buy one, but where's the fun in that? Besides, I can make my amp look the way I like.

I'm not an EE or amp designer. But I can follow instructions and plans. I'm hoping I can build something that's relatively easy and works without a lot of tweaking. Once I get that far, I don't mind experimenting with improvements but I've no illusion of creating a circuit from scratch. I'm even shy of merging two circuits to get, say, a Champ with reverb.

Thanks for sharing your pics. I really enjoy seeing the experiences others have had.

[tubeswell]

I see some caps marked in pF and others with only a number value. Would those be in Farads? Caps marked like 25-25 would be 25F caps with a 25V rating?

pF is picofarads - 1 pF is one million-millionths of a farrad (on some really old schematics you will see uuF, which is micro-micro farads, which is picofarads)nF is nanofarads - 1nF is one thousand millionths of a farrad (1nF = 1,000pF)uF is microfarads - 1uF is one millionth of a farad (1uF = 1,000nF = 1,000,000pF) (i.e.; .1uF = 100nF, .022uF = 22nF etc)'25-25' next to a cap on a fender schematic means 25uF and 25V rating. (This invariably means an electrolytic cap, because only they tend to be physically small enough to be practical in the microfarad range. If you had 25uF film caps, they would be relatively huge. With an e-cap, you need to have the polarity the correct way around or the cap will explode).

What do the numbers like 2-35 and 0353 on some pots mean?

Pot manufacturer's code - depends on the manufacturer.

I want to build an amp in the Tweed Deluxe style but with reverb. A Deluxe Reverb in that style of cabinet, stained, no tolex covering would be nice. The length of the chassis can be 18-19" but the space for the top-mounted controls would be reduced to about 12" which isn't a lot of room. I thought about possibly making the chassis deeper so the controls can be stacked with one channel "above" (or more like in front of) the other. Another possibility is that of using smaller pots and knobs to put the controls closer together. Has that been done? Or is there some reason that's a ridiculous idea? My fallback is a Princeton Reverb but I like having two channels.

If you are at the start, and you want 2 channels, then just build a 5E3 (without reverb). You really should start with something straightforward and relatively uncomplicated to get tube-amp-building-addiction properly. ;-) There is usually a bit of troubleshooting with each build. If you try something too ambitious, you may end up quickly frustrated. If you insist on reverb, then maybe build a 6G15 to plug in front of the 5E3, or build a BFPR, (but even that is a lot trickier to get the grounding right with). JM2CW

[tubeswell]

When I posted the above post I had lines between the bits of text after the 1st quote, but for some strange reason they deleted themselves when I pressed the 'submit reply' button, and I tried to re-edit them straight away, but strangely it wouldn't let me edit. So here is the first part of my reply (hopefully this time formatted s I intended it to be the first time. (If not we may need t-boy to take a look at the formatting problem)

I see some caps marked in pF and others with only a number value. Would those be in Farads? Caps marked like 25-25 would be 25F caps with a 25V rating?

pF is picofarads - 1 pF is one million-millionths of a farrad (on some really old schematics you will see uuF, which is micro-micro farads, which is picofarads).nF is nanofarads - 1nF is one thousand millionths of a farrad (1nF = 1,000pF).uF is microfarads - 1uF is one millionth of a farad (1uF = 1,000nF = 1,000,000pF) (i.e.; .1uF = 100nF, .022uF = 22nF etc).'25-25' next to a cap on a fender schematic means 25uF and 25V rating. (This invariably means an electrolytic cap, because only they tend to be physically small enough to be practical in the microfarad range. If you had 25uF film caps, they would be relatively huge. With an e-cap, you need to have the polarity the correct way around or the cap will explode).

[tubeswell]

Dang! it didn't work again. Please help t-boy!

[loudthud]

Many of the kits on the market do not include step by step instructions. You are basically presented with a schematic, a layout diagram and a bag of parts. So before you purchase a kit, check that the level of documentation and instructions meets your needs. In addition to the kit you should have a Digital Volt Meter. You can find them for less than $10. It's useful to measure all resistors to make sure you have the correct value, the color codes confuse some builders. Also if there is any trouble with the amp, voltage readings help locate the problem. Besides simple hand tools you should get a wire stripper. It will save you a lot of time.

[Jack Sparrow]

Thanks, Tubeswell, for the clarification on the caps. I recognized the pF values. I assumed that I'd see uF if they meant microfarads and that nothing would mean farads but I hadn't thought about the size of the caps which might have straightened me out. I appreciate what you're saying about not getting in too deep the first time out. I was looking at the 5E5 circuit today and thinking it looked less challenging (but no vibrato or reverb). I hadn't looked at the 5E3 yet. The reason I mentioned 2 channels is to be able to separately control the volume of a second input from an acoustic stompbox or microphone. Both the 5E3 and the 5E5 would meet that requirement. I'll be careful about how much I bite off.

Besides simple hand tools you should get a wire stripper. It will save you a lot of time.

on the tools. I think I have most of what I'd need, including a nice digital multi-meter. That said, I'm more at home with a hammer and saw than with a soldering iron. That's why I'm interested in making a wood finished cabinet. I think I can do a good job on a small hardwood cabinet. But, yeah, the electronics will be more of a challenge. I've got more confidence than experience. The good news is that I tend to plan out projects like this to avoid surprises and make sure I know what I'm getting into before I even start.


Thanks for your comments and advice. I'm still in the early concept stage so anything could happen before I place an order.

[Enzo]

Not always, of course, but MANY schematics will have notes in the corner, and you should read them. IN many cases it will say things like "all caps in microfarads unless otherwise noted." Or all resistors 1/2 watt unless otherwise noted. And so on.

As Loudthud mentioned, kits can be as simple as a bag of parts or so comprehensive as to include layout drawings and assembly instructions. Worth checking out before purchase. But kits ARE worth a look. If nothing else, they usually come with everything, you won;t get halfway through a build and discover you never ordered the 1.5k resistors you need. And sockets, and nuts for the jacks, and and and...

But kits also can save you the trouble of making a chassis. A premade and punched chassis is a big work saver in my book. COntrol labels already printed on. Places that sell amp kits often also sell just the chassis, if you want to gather your own parts elsewhere. And like forgetting to order a resistor, drilling holes on the panel for one less control than you have is something you don;t want to discover the hard way. Cabinets as well.