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cad software for guitar tube amp design

7/22/1999 5:48 AM
rapack	cad software for guitar tube amp design hello, I'm new to this whole "build your own guitar tube amp" gig, and I'm hoping someone here has an answer for me: Is there a software package (Windows95+ compatible desired) out there that one would/could use to help in designing/testing vacuum tube amplifier circuits, particularly amps for use with musical instruments (like a guitar amp) ??? I own a copy of "The Ultimate Tone", the Pittman book "The Tube Amp Book" 4,1, "Vacuum Tube Guitar and Bass Amplifier Theory" by Tino Zottola, "Beginner's Guide to Tube Audio Design" by Bruce Rozenblit, and even "How to service your own tube amp" by Tom Mitchell. (and a few various books on basic electricity and electronics to boot) I'm thinking of building myself a first TUBE amp based on the Fender "champ" but with various modifications - to improve the signal to noise ratio and add a little more flexibility. I purchased "Tube CAD" but its not really at all what I'm looking for - I've "heard" (over the web, in various places like this) murmurs that lead me to think that there are CAD like packages that can be used to create TUBE-based circuits AND do some simulation/modelling too... am I correct in this ASSumption? If so, what are those packages and where might I search to find them? (okay that was long winded, sorry) Thanks for any help you can offer! rapack

7/22/1999 5:48 AM

rapack

cad software for guitar tube amp design

hello, I'm new to this whole "build your own guitar tube amp" gig, and I'm hoping someone here has an answer for me:

Is there a software package (Windows95+ compatible desired) out there that one would/could use to help in designing/testing vacuum tube amplifier circuits, particularly amps for use with musical instruments (like a guitar amp) ???

I own a copy of "The Ultimate Tone", the Pittman book "The Tube Amp Book" 4,1, "Vacuum Tube Guitar and Bass Amplifier Theory" by Tino Zottola, "Beginner's Guide to Tube Audio Design" by Bruce Rozenblit, and even "How to service your own tube amp" by Tom Mitchell. (and a few various books on basic electricity and electronics to boot)

I'm thinking of building myself a first TUBE amp based on the Fender "champ" but with various modifications - to improve the signal to noise ratio and add a little more flexibility.

I purchased "Tube CAD" but its not really at all what I'm looking for - I've "heard" (over the web, in various places like this) murmurs that lead me to think that there are CAD like packages that can be used to create TUBE-based circuits AND do some simulation/modelling too... am I correct in this ASSumption? If so, what are those packages and where might I search to find them?

(okay that was long winded, sorry) Thanks for any help you can offer!

rapack

7/22/1999 4:16 PM
Bruce	There are a number of us here who have built a bunch of these little amps and I can tell you from much experience, there is NO substitute for getting your hands dirty! If a SE Champ type amp is where you want to go now, forget the computer model stuff for a bit and get some amp parts. These amps are butt simple and a blast to experiment on with small circuit changes. And cheap! You'll learn more in a putzing weekend with a homebrew champ circuit then any computer program is going do for you. Start asking questions and you'll find guys falling over themselves trying to help you here. Pop over to the AX84 link for another small amp project. http://www.intsys.net/ax84/index3.html Bruce

7/22/1999 4:16 PM

Bruce

There are a number of us here who have built a bunch of these little amps and I can tell you from much experience, there is NO substitute for getting your hands dirty!

If a SE Champ type amp is where you want to go now, forget the computer model stuff for a bit and get some amp parts.

These amps are butt simple and a blast to experiment on with small circuit changes. And cheap!

You'll learn more in a putzing weekend with a homebrew champ circuit then any computer program is going do for you.

Start asking questions and you'll find guys falling over themselves trying to help you here.

Pop over to the AX84 link for another small amp project.

http://www.intsys.net/ax84/index3.html

Bruce

7/22/1999 6:25 PM
rapack	hrmph. Um, OKAY. Well then, I guess thats the way I'll approach it... Here's my THINKING at the present moment: 1) I'll be starting with the Fender "champ" model - either the "5C1" or the "5F1" version - looks like the "5C1" has a couple of differences: a capacitor AND resistor off the first triode's cathode (instead of just a resistor in the "5F1", and the use of a choke (instead of just 10K resistor), and one capacitor is 16 (farads or micro-farads?) instead of just 8... 2) I'd like to use DC for the filaments rather than AC - overall I'm trying to keep it as noise-free as I can - and I'd also like to skip the rectifier TUBE for a more solid-state power supply choice (although the "Ultimate Tone" volume talks about a circuit to make a solid-state power supply "sag" similar to the TUBE rectifier - I'd like to try that) 3) I even thought it'd be nice to use TOROIDAL transformers instead of the standard (iron-core?), but they're pretty expensive - if I used ONE toroidal and the other a regular one, would the power transformer be the best choice for the toroid? In terms of keeping noise down? 4) I'd wanted to use a Bass Mid & Treble tone control bit instead of just a single tone control - similar to the "Bassman" ? I hear that the more stuff I stick in the signal chain, the more I'm gonna screw with the sound, so I've been thinin' of cutting back to just bass & treble... 5) (here's the real ambitious part) I'd WANTED to ad two more gain stages IN PARALLEL with the first one and make then all mixable (as discussed in "Ultimate Tone") but I think that woudl be too complex. So then I've stepped back to thinkin' of just adding the two gain stages, with a fixed gain, and putting switches in to be able to switch each/either of them in or out of the circuit. I don't need to switch em DURING "a performance", its just for home practice/recording. but I also figure that I probably ought to semi-remote the switching part so that I don't have to pull the actual SIGNAL path all the way out of the circuit TO the front panel switches... (does that make sense?) 6) I was PLANNING to NTO ground to the chassis, but try for a "star ground" ... but I also wanted to place the chassis inside a nice built case made of wood (with plenty of breathing holes!) that is lined with a conductive screen on the inside to filter out radio interference? So does that mean I need to run a wire from "star ground" out to the "cage"? 7) is it WORTH it to use "hi-silver-content" wire for all the hookup in the amp? 8) is this WAY too much for me to be thinkin for my first hand-built tube amp project? Thanks for your help and patience! rapack

7/22/1999 6:25 PM

rapack

hrmph. Um, OKAY. Well then, I guess thats the way I'll approach it... Here's my THINKING at the present moment:

1) I'll be starting with the Fender "champ" model - either the "5C1" or the "5F1" version - looks like the "5C1" has a couple of differences: a capacitor AND resistor off the first triode's cathode (instead of just a resistor in the "5F1", and the use of a choke (instead of just 10K resistor), and one capacitor is 16 (farads or micro-farads?) instead of just 8...

2) I'd like to use DC for the filaments rather than AC - overall I'm trying to keep it as noise-free as I can - and I'd also like to skip the rectifier TUBE for a more solid-state power supply choice (although the "Ultimate Tone" volume talks about a circuit to make a solid-state power supply "sag" similar to the TUBE rectifier - I'd like to try that)

3) I even thought it'd be nice to use TOROIDAL transformers instead of the standard (iron-core?), but they're pretty expensive - if I used ONE toroidal and the other a regular one, would the power transformer be the best choice for the toroid? In terms of keeping noise down?

4) I'd wanted to use a Bass Mid & Treble tone control bit instead of just a single tone control - similar to the "Bassman" ? I hear that the more stuff I stick in the signal chain, the more I'm gonna screw with the sound, so I've been thinin' of cutting back to just bass & treble...

5) (here's the real ambitious part) I'd WANTED to ad two more gain stages IN PARALLEL with the first one and make then all mixable (as discussed in "Ultimate Tone") but I think that woudl be too complex. So then I've stepped back to thinkin' of just adding the two gain stages, with a fixed gain, and putting switches in to be able to switch each/either of them in or out of the circuit. I don't need to switch em DURING "a performance", its just for home practice/recording. but I also figure that I probably ought to semi-remote the switching part so that I don't have to pull the actual SIGNAL path all the way out of the circuit TO the front panel switches... (does that make sense?)

6) I was PLANNING to NTO ground to the chassis, but try for a "star ground" ... but I also wanted to place the chassis inside a nice built case made of wood (with plenty of breathing holes!) that is lined with a conductive screen on the inside to filter out radio interference? So does that mean I need to run a wire from "star ground" out to the "cage"?

7) is it WORTH it to use "hi-silver-content" wire for all the hookup in the amp?

8) is this WAY too much for me to be thinkin for my first hand-built tube amp project?

Thanks for your help and patience!

rapack

7/22/1999 9:17 PM
Michael Cameron	For a first amp I reccomend you don't bite off more than you can chew. Build the 5F2 or similar Champ/Princeton and enjoy it stock for a while. After you are familiar with its strengths and weaknesses try changing ONE THING AT A TIME. Much better chance of sucess following this route IMO. You have plenty of time to hone your chops as an amp building whiz. Most guys I talk to manage to make at least one mistake building their first amp, even one as simple as a Champ. If you do get into trouble on your first build it will be a lot easier for those here to help you troubleshoot it if you haven't added lots of extra features. Good luck Michael

7/22/1999 9:17 PM

Michael Cameron

For a first amp I reccomend you don't bite off more than you can chew.

Build the 5F2 or similar Champ/Princeton and enjoy it stock for a while. After you are familiar with its strengths and weaknesses try changing ONE THING AT A TIME. Much better chance of sucess following this route IMO. You have plenty of time to hone your chops as an amp building whiz.

Most guys I talk to manage to make at least one mistake building their first amp, even one as simple as a Champ. If you do get into trouble on your first build it will be a lot easier for those here to help you troubleshoot it if you haven't added lots of extra features.

Good luck

Michael

7/22/1999 11:39 PM
SteveR	My first amp (and hence screw-up!) was an AC30 top boost clone. Talk about biting off more than you can chew! I think the hardest part was figuring out where everything was going to go. I think layout and signal routing is something of an art unto itself. The whole thing was point to point using terminal strips in a two rack space high chassis. I mounted both transformers and all the tubes (no rectifier tube or vib channel) on a piece of aluminum that I had to have punched and worked at a sheet metal shop (not cheap!). I mounted this piece in the middle of the chassis so the tubes were horizontal but not sticking out the back unprotected. I drilled about a bajillion vent holes above and below the tubes through what seemed like cast iron. I even had rigged up a three way power switch for off/on/on-with-fan. When I eventually finished mounting everything and soldering it all up, I thought it sounded OK but kind of weak. Further analysis would reveal that I had managed to ground the output of one side of the PI. But it's Class A so there wasn't any awful cutoff distortion! It was basically running parallel single ended el84s. Goofy, huh. Then of course when I fixed that I came across some nasty squealing at hi gain/volume levels. This was before I had internet access so I really didn't have any resource for learning how to troubleshoot. I had pretty much figured that if I hooked it up according to the schematic it should work. Hah! I haven't touched the thing since. I'm sure I'll get to it one day... Rapak - I'd skip doing a lot of the stuff to make it quieter for now. It's not a high gain circuit and isn't very loud so noise probably isn't going to be a huge problem. I would say a good well filtered power supply, careful high quality lead dress (perhaps even using shielded leads), and proper grounding techniques are going to go a long way at keeping noise down. With a SS rectifier you cn use quite a bit more capacitance in the b+ filtering. This will give some improved bass response as well as reducing ripple (noise). I don't know about the toroidal tranny. Leo didn't have no toroids. Instead of rectified DC, just referencing the filament line to ground will help, and you could go a slight step further and add a hum adjust pot. I'd agree with Michael about keeping it stock for awhile. You may want to get a chassis that will allow for expandibility (added stages) but start with the basics. SteveR

7/22/1999 11:39 PM

SteveR

My first amp (and hence screw-up!) was an AC30 top boost clone. Talk about biting off more than you can chew!

I think the hardest part was figuring out where everything was going to go. I think layout and signal routing is something of an art unto itself. The whole thing was point to point using terminal strips in a two rack space high chassis. I mounted both transformers and all the tubes (no rectifier tube or vib channel) on a piece of aluminum that I had to have punched and worked at a sheet metal shop (not cheap!). I mounted this piece in the middle of the chassis so the tubes were horizontal but not sticking out the back unprotected. I drilled about a bajillion vent holes above and below the tubes through what seemed like cast iron. I even had rigged up a three way power switch for off/on/on-with-fan.

When I eventually finished mounting everything and soldering it all up, I thought it sounded OK but kind of weak. Further analysis would reveal that I had managed to ground the output of one side of the PI. But it's Class A so there wasn't any awful cutoff distortion! It was basically running parallel single ended el84s. Goofy, huh.

Then of course when I fixed that I came across some nasty squealing at hi gain/volume levels. This was before I had internet access so I really didn't have any resource for learning how to troubleshoot. I had pretty much figured that if I hooked it up according to the schematic it should work. Hah! I haven't touched the thing since.

I'm sure I'll get to it one day...

Rapak - I'd skip doing a lot of the stuff to make it quieter for now. It's not a high gain circuit and isn't very loud so noise probably isn't going to be a huge problem. I would say a good well filtered power supply, careful high quality lead dress (perhaps even using shielded leads), and proper grounding techniques are going to go a long way at keeping noise down.

With a SS rectifier you cn use quite a bit more capacitance in the b+ filtering. This will give some improved bass response as well as reducing ripple (noise).

I don't know about the toroidal tranny. Leo didn't have no toroids.

Instead of rectified DC, just referencing the filament line to ground will help, and you could go a slight step further and add a hum adjust pot.

I'd agree with Michael about keeping it stock for awhile. You may want to get a chassis that will allow for expandibility (added stages) but start with the basics.

SteveR

7/22/1999 10:13 PM
Don Symes	Don't be too distressed... there ARE a couple of somewhat helpful tools you can get hold of. Dave Cigna's tone stack simulator can give you some idea of the effects of component values for Fender and Vox -style circuits. I don't know who's hosting it now. You can get a free copy of Spice from microsim. It's a limited version, but can be sort-of handy for modeling. There are a couple of articles around on DC filaments, try R.G. Keen's site, then Steve Ahola's. At least one of them either has them or links to them. Transformer style, at least in power transformers, is less important than correctly orienting its field with the OT so they don't interfere and inject hum. As for the tone controls, look at a BT stack and a BMT stack. You'll notice the MID pot replaces a fixed resistor. It would be reasonable - as a refinement step - to have a pull-switch mid pot to do the swap. I'd really suggest you stick with a real rectifier tube. I think you'll be happier. Besides, it makes your PT selection easier. Angela has 'em in stock almost all the time. As to the gain stages, that sounds like another refinement step. Theoretically, it's a simple thing to do if you can get the LDRs - usually VACTEC 5C1 (or 2,3,4). Consider the additional filament load of another tube. Actually, consider using a Deluxe Reverb PT. What does NTO stand for? The case is a nice idea, just ground the cage to the chassis and cover the circuit 'pan' with a metal plate. I'd suggest two things at this point: 1) build you amp as a head so it's easy to use a variety of speaker arrangements 2) use a chassis that's at least half again the size you think you need. Do use a very similar layout to your model (don't spread out too much). Now you have gobs of room for mods/enhancement, or just a larger amp altogether. Good luck, and read everything this site links to. Don

7/22/1999 10:13 PM

Don Symes

Don't be too distressed... there ARE a couple of somewhat

helpful tools you can get hold of.

Dave Cigna's tone stack simulator can give you some idea of the effects of component values for Fender and Vox -style circuits. I don't know who's hosting it now.

You can get a free copy of Spice from microsim. It's a limited version, but can be sort-of handy for modeling.

There are a couple of articles around on DC filaments, try R.G. Keen's site, then Steve Ahola's. At least one of them

either has them or links to them.

Transformer style, at least in power transformers, is less

important than correctly orienting its field with the

OT so they don't interfere and inject hum.

As for the tone controls, look at a BT stack and a BMT stack. You'll notice the MID pot replaces a fixed resistor.

It would be reasonable - as a refinement step - to have a

pull-switch mid pot to do the swap.

I'd really suggest you stick with a real rectifier tube. I

think you'll be happier. Besides, it makes your PT selection easier. Angela has 'em in stock almost all the time.

As to the gain stages, that sounds like another refinement step. Theoretically, it's a simple thing to do if you

can get the LDRs - usually VACTEC 5C1 (or 2,3,4). Consider

the additional filament load of another tube. Actually,

consider using a Deluxe Reverb PT.

What does NTO stand for?

The case is a nice idea, just ground the cage to the chassis

and cover the circuit 'pan' with a metal plate.

I'd suggest two things at this point:

1) build you amp as a head so it's easy to use a variety of

speaker arrangements

2) use a chassis that's at least half again the size you think you need. Do use a very similar layout to your model (don't spread out too much). Now you have gobs of room for

mods/enhancement, or just a larger amp altogether.

Good luck, and read everything this site links to.

Don

7/22/1999 11:19 PM
rapack	you asked: "What does NTO stand for?" Referring to where I said: "I was PLANNING to NTO ground to the chassis..." ...er ...um ...thats Greblarianeze for "aint gonna" ... (meaning, "I aint gonna ground to the chassis") Oh yeah, I DO plan on making this a separate amp HEAD and Speaker Cabinet - so I can try different speakers AND so that I can keep them in separate places so the speaker doesn't interfere with the tubes and the vibration doesn't shake em... Where you say: "Theoretically, it's a simple thing to do if you can get the LDRs - usually VACTEC 5C1 (or 2,3,4)." Um, what does the term "LDR" mean? Thanks again, -rapack

7/22/1999 11:19 PM

rapack

you asked: "What does NTO stand for?"

Referring to where I said: "I was PLANNING to NTO ground to the chassis..."

...er ...um ...thats Greblarianeze for "aint gonna" ... (meaning, "I aint gonna ground to the chassis")

Oh yeah, I DO plan on making this a separate amp HEAD and Speaker Cabinet - so I can try different speakers AND so that I can keep them in separate places so the speaker doesn't interfere with the tubes and the vibration doesn't shake em...

Where you say: "Theoretically, it's a simple thing to do if you can get the LDRs - usually VACTEC 5C1 (or 2,3,4)."

Um, what does the term "LDR" mean?

Thanks again,

-rapack

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