After reading reading everybodies coments and bashing people over the heads with soldering irons I propose this challenge. To design a guitar amplififer with either class A or AB around the 50-100W with off the shelf parts.
You may think that this has been done before but think again the challenge is to incorporate ideas we all have had like I placed on the forum Auto-Biasing regulation with say J Fet's.
So get those old ideas you have had and get others to be involved this may be a fun way to get people interested in being part of a project.
Hope to hear from you all.
Wyatt
You may think that this has been done before but think again the challenge is to incorporate ideas we all have had like I placed on the forum Auto-Biasing regulation with say J Fet's.
So get those old ideas you have had and get others to be involved this may be a fun way to get people interested in being part of a project.
Hope to hear from you all.
Wyatt
Seriously, Wyatt, go visit www.ampage.org and see what everyone is doing there. Designing and building and modifying amps is what that site is all about.
If you try to get a transformer from Mesa Boogie, it will cost you an arm and a leg. You con't neeed a name brand transformer. You can get generic power and output transformers.
And I also have to say that in the land of guitar amps the word "bias" is almost a mantra. Bias bias bias, we chant until it takes on a mysticism. In reality it is not all that critical an adjustment. it may be interesting as an exercise to make some complex sensing circuit that servos the bias level in some way, but plain old vanilla bias circuits work just fine.
Amp bias is a bit like the tire pressure in your car. You don't want so little air in them that they go flat, nor do you want them blown up so hard they won't sit flat on the pavement. But in between there is a wide range of tire pressures that are perfectly good. A few pounds either way from the "proper" pressure won't really affect their performance much. A couple milliamps either way on cathode current will not have a large affect on tone.
On the other hand I am fairly practical at this point in my life, I don't experiment as much these days. I certainly do not mean to discourage any project, even complex bias circuits.
If you try to get a transformer from Mesa Boogie, it will cost you an arm and a leg. You con't neeed a name brand transformer. You can get generic power and output transformers.
And I also have to say that in the land of guitar amps the word "bias" is almost a mantra. Bias bias bias, we chant until it takes on a mysticism. In reality it is not all that critical an adjustment. it may be interesting as an exercise to make some complex sensing circuit that servos the bias level in some way, but plain old vanilla bias circuits work just fine.
Amp bias is a bit like the tire pressure in your car. You don't want so little air in them that they go flat, nor do you want them blown up so hard they won't sit flat on the pavement. But in between there is a wide range of tire pressures that are perfectly good. A few pounds either way from the "proper" pressure won't really affect their performance much. A couple milliamps either way on cathode current will not have a large affect on tone.
On the other hand I am fairly practical at this point in my life, I don't experiment as much these days. I certainly do not mean to discourage any project, even complex bias circuits.
Wyatt Turk said:
Such language in the "Tubes" area
🙁 😉
Why not? Why should AX84 and Ampage have all the fun? 😀
Good idea.
I think 50W is the most you should shoot for unless it is designed for large concerts. The reason is you'd never be able to overdrive the output stage without blowing everybody, you playing mates included, out of the place. I vote for a sweet 20watts, switchable between class A and AB. Also, as few gainstages as possible. Using SS for biasing and even loading of the tubes is a good idea. It's time for something different than all those Fender copies.
I think 50W is the most you should shoot for unless it is designed for large concerts. The reason is you'd never be able to overdrive the output stage without blowing everybody, you playing mates included, out of the place. I vote for a sweet 20watts, switchable between class A and AB. Also, as few gainstages as possible. Using SS for biasing and even loading of the tubes is a good idea. It's time for something different than all those Fender copies.
This subject appears to be dead before it got started maybe instead of saying what you think it should be, start puting a basic diagram together and get cracking...
Wyatt
Wyatt
I am smelling a hybrid. 4 stage 12AX7 feeding into a bridged LM3875.
Since tubes are good at voltage, let it handle the preamp stage, and driven into crunching distortion. Modern ICs nowadays can deliver high power cheaply.
For power stage, the bridged 3875 can give you 100watts easilly.
But then you cannot overdrive the output stages, unlike a fully tube design.
Since tubes are good at voltage, let it handle the preamp stage, and driven into crunching distortion. Modern ICs nowadays can deliver high power cheaply.
For power stage, the bridged 3875 can give you 100watts easilly.
But then you cannot overdrive the output stages, unlike a fully tube design.
Do you have an idea of what sound you're looking for? And how loud you want it to go in a stage setting? If so, look at the classic schematics available freely on the web and reverse engineer. This'll get you a whole lot closer to the area of peformance you want to start with, and then play with the tubes, biassing, tonestacks etc to tweak the tonal range to your choice.Wyatt Turk said:
If you simply want a rich 'Jazz' sound then a gainstage (or two, depending on your pickups), a tonestack and a SET poweramp will do fine most of the time. Remember too, that the speaker you choose will have a huge effect on the final tone, as well as the amplifier.
Output trannies can be sourced from New Sensor.
The chip amps usually stink as guitar amps.
Wiiling to participate
G'day Wyatt,
I've got as far a some prototype metal work on just such a project.
My ideas at present are for a "mini head". Driving a Marshall 50W Output transformer (or a Hammond equivalent) with 4 off 6V6 switchable cathode bias or fixed bias. This is something which I think has promise AND I haven't seen done.
The preferred guitar amps seem to be the ones using lower gm output tubes ie 6L6, 6V6. If you are thinking in terms of a low power bedroom / small flat practice amp 6BM8 may well be worth a go.
The ONLY amps which use high gm tubes seem to be the VOX with EL84s in deep Class AB (NO its NOT pure Class A regardless the opinions to that effect which permeate the web) and Marshalls (EL34). I've NEVER been a Marshall fan - bloody awfull screech boxes with so much top end its hazardous to the ears.
I've also got most of a clean/crunch/overdrive preamp schematic on paper which is unashamedly a Hughes and Kettner rip off. I say unashamedly since a look at the H&K schematic quickly leads you to the view that it is ripped off from Fender (Clean Channel), Marshall (Crunch Channel) and Mesa (Overdrive Channel).
For your edification - read Kevin O'Connor (London Power) Ultimate Tone Volume 3 (I think its Volume 3) where he gives schematics and construction details for a range of "Icon" Amps.
Cheers
Feel free to email me direct
G'day Wyatt,
I've got as far a some prototype metal work on just such a project.
My ideas at present are for a "mini head". Driving a Marshall 50W Output transformer (or a Hammond equivalent) with 4 off 6V6 switchable cathode bias or fixed bias. This is something which I think has promise AND I haven't seen done.
The preferred guitar amps seem to be the ones using lower gm output tubes ie 6L6, 6V6. If you are thinking in terms of a low power bedroom / small flat practice amp 6BM8 may well be worth a go.
The ONLY amps which use high gm tubes seem to be the VOX with EL84s in deep Class AB (NO its NOT pure Class A regardless the opinions to that effect which permeate the web) and Marshalls (EL34). I've NEVER been a Marshall fan - bloody awfull screech boxes with so much top end its hazardous to the ears.
I've also got most of a clean/crunch/overdrive preamp schematic on paper which is unashamedly a Hughes and Kettner rip off. I say unashamedly since a look at the H&K schematic quickly leads you to the view that it is ripped off from Fender (Clean Channel), Marshall (Crunch Channel) and Mesa (Overdrive Channel).
For your edification - read Kevin O'Connor (London Power) Ultimate Tone Volume 3 (I think its Volume 3) where he gives schematics and construction details for a range of "Icon" Amps.
Cheers
Feel free to email me direct
I'll make some donations to the project 🙂
Here's a wicked sounding OD, using a triple section compactron:
http://geek.scorpiorising.ca/contrib/Geek/GuitarPre.png
No compactron? It's electrically similar to 12AT7 😉
Some good linedrivers:
http://geek.scorpiorising.ca/contrib/Geek/12AT7-SRPP.png
http://geek.scorpiorising.ca/contrib/Geek/12AT7-White-CF.png
http://geek.scorpiorising.ca/contrib/Geek/12AU7-SRPP.png
http://geek.scorpiorising.ca/contrib/Geek/12AU7-White-CF.png
The 12AU7 can give more output, but the 12AT7 just plain sounds better.
Here's a wicked sounding OD, using a triple section compactron:
http://geek.scorpiorising.ca/contrib/Geek/GuitarPre.png
No compactron? It's electrically similar to 12AT7 😉
Some good linedrivers:
http://geek.scorpiorising.ca/contrib/Geek/12AT7-SRPP.png
http://geek.scorpiorising.ca/contrib/Geek/12AT7-White-CF.png
http://geek.scorpiorising.ca/contrib/Geek/12AU7-SRPP.png
http://geek.scorpiorising.ca/contrib/Geek/12AU7-White-CF.png
The 12AU7 can give more output, but the 12AT7 just plain sounds better.
Agreed. BUT only when they are not used properly. Like I said, you cannot overdrive the power stages, unlike true tube amps. Combine a hybrid, you can overdrive the preamp as much as u like, then feed it to a good chipamp.
Also, there are a few good amps out there that uses chips.
Original thread:
Modern chips are better at handling large output powers at relatively low cost, compared to tubes. Even worse if you want to use NOS parts.. i believe many people have leftover chips lying around, which can be used immediately.
You shouldn't overdrive the chips, true, but the speaker's interaction with the amp dynamically contributes to the tone. Preamp overdrive is not the same as poweramp overdrive, sonically speaking.skyraider said:
For practice amps maybe..
now you've mentioned it, an amp sounds good as a contribution from everything; the number of gain stages, eq position, types of tubes, transformers, enclosure design, and of course speakers. Leaving any part out and you cannot get the amp's sound.
Since we are to respond to a new challenge design, why not turn away from conventionals? It seems that you are limiting yourself to tubes design only. My proposal is for a design using off the shelf parts. Well, unless you have lots of el34s and trannies lying around... well.. what can I say.
untill someone designs the first
Ah,
Just what I like to hear the dirty talk!, Overdriving, distortion my ISDN Light quivers under this. Why should the AX88 project have all the fun?. I do admit I made a guitar amplifier out of a Gibson front end and a 100w Mosfet back end for my brother some years ago and still works very well. "Sorry about the bad language using transistors etc in a valve section".
What I have done so far is buy a NOS 50w output transformer for a Mesa Boogie Mk3 and that what I'm starting with. I'm thinking more on the lines of a Messa Heartbreaker back end like amp with at least 3 preamp stages with effects etc. I do like the sound of individual channels that maybe swith at various sections to give you any style you like without manualy doing so.
Although I have made several transistor etc guitar amps I like the warmer sounds of valves and I will have a look at any schematic that people send me...
Wyatt
Just what I like to hear the dirty talk!, Overdriving, distortion my ISDN Light quivers under this. Why should the AX88 project have all the fun?. I do admit I made a guitar amplifier out of a Gibson front end and a 100w Mosfet back end for my brother some years ago and still works very well. "Sorry about the bad language using transistors etc in a valve section".
What I have done so far is buy a NOS 50w output transformer for a Mesa Boogie Mk3 and that what I'm starting with. I'm thinking more on the lines of a Messa Heartbreaker back end like amp with at least 3 preamp stages with effects etc. I do like the sound of individual channels that maybe swith at various sections to give you any style you like without manualy doing so.
Although I have made several transistor etc guitar amps I like the warmer sounds of valves and I will have a look at any schematic that people send me...
Wyatt
How'bout using triodes as output tubes? And how'bout DHTs like 1G6G for preamp work? That'd be different! And use modern SS CCS loading for max gain, new meets old. How'bout it?
Wyatt - preamp ideas
Preamp ideas:
I once spent a lot of time reverse engineering the H&K TriAmp to understand the gain struture and voicing of the 6 available "sounds" including spice simulations. I then started to look at designing a switching preamp to give me those sounds.
About half way thru' I came across some Trace Elliot schematics at the Schematic Heaven website under the "Post 70's Amps" heading ONLY to find that they had already done what I was setting out to do.
Grab a copy of these schematics as a good head start to your preamp section.
Preamp ideas:
I once spent a lot of time reverse engineering the H&K TriAmp to understand the gain struture and voicing of the 6 available "sounds" including spice simulations. I then started to look at designing a switching preamp to give me those sounds.
About half way thru' I came across some Trace Elliot schematics at the Schematic Heaven website under the "Post 70's Amps" heading ONLY to find that they had already done what I was setting out to do.
Grab a copy of these schematics as a good head start to your preamp section.
Well I'm in the midst of building a 6L6GC PP Fender bassman copy. For a speaker I am using a Goodmans Audiom 70 which is a very sensitive 12" and it is DEAFENING in terms of volume. I can't get a power tube crunch at any sort of sensible level, but when you do crank it up- whoa! What a sound. And I am just using wussy cathode bias, not even fixed bias.
However it sounds great. I would truly recommend a PP 6L6GC or EL34, thats a classic amp tone right there. Build a very basic tube preamp, and get some pedals to do all your effects for you.
I have built a couple of SE 6V6 and EL84 guitar amps, but they really dont have the bite that this PP 6L6GC has...
However it sounds great. I would truly recommend a PP 6L6GC or EL34, thats a classic amp tone right there. Build a very basic tube preamp, and get some pedals to do all your effects for you.
I have built a couple of SE 6V6 and EL84 guitar amps, but they really dont have the bite that this PP 6L6GC has...
Geek I have downloaded your diagrams and will have a look at them when my wife lets me have more than five minutes peace. I am trying to go through the diagrams that I have which is some 167 on my hard drive.
One thing that I have noticed is that 459 people have viewed this thread with only 15 responses. That's a lot of people just sitting around waiting for something to happen.
Rome was not built in a day so is a great amp project!!!... Just think what a new Marshall, Fender Or Mesa costs and you could be the next one to contribute to that.
Time for Bed
Wyatt
One thing that I have noticed is that 459 people have viewed this thread with only 15 responses. That's a lot of people just sitting around waiting for something to happen.
Rome was not built in a day so is a great amp project!!!... Just think what a new Marshall, Fender Or Mesa costs and you could be the next one to contribute to that.
Time for Bed
Wyatt
Wyatt, I check this thread every day to see where it is going. I made my coments earlier and have nothing of substance to add. I think a lot of your people sitting and waiting to see what happens are people visiting more than once, and they may not have anything to add either. We are not hiding.
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