I'm interested in building my own tube amp for a guitar and really optimizing it so that it's on par with some of the really nice boutique guitar amps. Can anyone out there point me in the right direction for parts and on how to go about creating the component configuration?
I've worked with FPGAs and DSPs for the bulk of my career, going bacwards in time I encountered my first FPGAs during my PhD, my first microprocessor at University during my degree, and going further back as a young teenager (actually I think I was just turned 12) I used to build Disco amplifiers using Valves from old Radio and TV sets I found on rubbish dumps as I couldn't afford the new 'Transistors'.
So I'm not old enough to have serious career experience with Valves, nor am I an expert on 'boutique' expectations. But if you have no other responses on this thread then I am happy to give what knowledge I remember, accompanied by the many years of semiconductor electronincs I have lived through since.
Thanks Jeff, much appreciated. I guess I'm looking for tubes that would easily bias towards a much more saturated and distorted tone. Also, I'm wondering how I would go about designing the EQ for this as well.
You can obtain schematics for many of the tube guitar amps. The tubes used are still manufactured. Tubes such as the 6LCGC, 12AX7, 12AT7, and 12AU7 are made in China.
The power transformers and audio output transformers are still made by Hammond Manufacturing. Here is a link:
You could do a lot worse than joining the DIY AUDIO Forum. It is packed with a near endless suppl of imformation on all things audio. It has a section Dedicated to musical Instrument amplification . Give it a try i dont think you will disapointed.
I have a whole book outlining old vintage tube amps and it comes with all of the schematics of the amps that were described. It has presented some good ideas as to what I'd want the amp to sound like but my problem is seeing where I should start with the prototyping. Which tubes will do the best job? Etc...
there are many EEs on diyaudio some famouse ones too go have a look i can asure you you will find what you are looking for. also dont forget the output transformers are a large part of the sound too .
I am not guitar amp specialist so I can't bring you schematic. In my opinion the best one is hybrid tube-bipolar amp, where gain is obtained from tube and bipolars are used as additional supporting devices for supply voltage filtering and current sources (to achive more linear characteristic and adjust output impedance). Nowdays pure tubes constructions appears a bit obsolete. What tubes? Any kind of HF miniature like ECC83 (12ATX) triode or pentode is suitable for this. As far as EQ is concerned.... there is a lot off integrated IC's for this, however implementing EQ stage, be aware that sound would be much more flat with EQ than without it.... Kris
Each tube will have it's own sound. Even different manufacturer's 12AX7 for example can sound different.
The classic distorted electric guitar sound can of course be had with a tube amp. It is also synthesized these days.
As to tubes I believe the popular output tubes are the 6L6GC and the 6V6. The 6L6GC is still made (the 6L6 came out in 1936) so that is what I would use. For the input stage the 12AX7 is a favorite. It has a mu of 100 but is operated at a plate current of just 200-500 uA. It was designed as an audio amplifier tube. The 12AT7 has a mu of 60 and runs considerably more current. It is an RF amplfiier tube that makes a fine audio tube. I like it as an all around tube. The 12AU7 has a lower mu but will run 10 mA or more. This is a good tube for driving the grids of the 6L6's.
The guitar amp sound is a combination of "blocking distortion", operating the tube in highly non-linear areas of the transfer curve, the 3/2 power curve of a tube, and as mentioned by Ian the output transformer.
Blocking distortion: The plate of one stage is coupled to the grid of the next stage via a DC blocking capacitor. The grid of a tube acts as diode with the cathode. Drive the grid positive and it draws grid current. Normally in an audio amp one would not drive the grid of one of these tubes positive but in a guitar amp they do. This causes the grid to draw current and charge the DC blocking cap. The blocking cap now has a charge such that until it discharges back to where it was the tube is presented with extra negative bias.
Most guitar amp stages are single-ended and contribute mainly even harmonics; 2nd, 4th, etc. The output push-pull stage cancels even order harmonics and contributes mainly 3rd harmonic as does the transformer.
IMHO the most important thing in working with tube amplifiers is to ensure you have quality passive parts.
I once worked at a plant that was loosing 2 - 3 amps a day. I instituted a program to replace the 1W 600 ohm carbon resisters feeding the Cathode with 5W non inductive wirewound. We turned our loss rate down to 2 - 4 per month.
Make sure your capacitors are high temperature rated. Especially the electrolytics. Plan to replace all your electrolytics about every 5 years.
However beware I’ve been in contact with some of their colleagues and to date I still cant get answers in relation to some of the simulations that I’ve had problems with in particular oscillators Colpits, Crystal controlled , Flip flop, and certain Oscillators using logic gates I am a little disappointed in their attitude however I suppose one cant expect to much from CAD software which is to all intensive purpose quite cheap although I hasten to add you have to pay £25.00 each year to keep this up dated
I think it’s a bit of joke really when you consider that students relay on this software as to does the industry to produce designs Such is the software industry not just with cad also with windows also with games and really needs to be exposed for what it is
If you are going to produce something then why is it that the customer end user has to have an almighty bloody argument with them just to get what they paid for in the first place Still I notice that they are continuing to produce the software and of course I still have no response whilst being advertised in a magazine who also doesn’t seem to worry about this at all whilst customers readily not only purchase the magazine but also purchase form the adverts within that magazine
In fact to say I’m disgusted with this trade and industry plus the attitudes of not only the manufacturers but also the general trade would be an understatement surely there must be some course of action that we can take On the whole though its not a bad package but as they say a miss is as good as a mile
One of these days well get an answer in the meantime of course check this software thoroughly and you too will notice the catastrophic errors that they have made
Makes you wonder why these companies end up failing hmm Us no not at all It’s the typical had your money couldn’t care less attitude of none other than Great Britain, United States, the rest of the world
If only they would just open their bloody ey6esd and realize exactly what is they do not only to other businesses but also to people lives “Business they call this!! “
What happened to Business ethics then forgot these did we??
No bloody wonder we have a massive recession isn’t about time we put an end to some of them once and for all
But having said all this Believe it or not you can still design vacuum tubes amps within this although like many other people I’ve worked on tube amps still do, even guitar amps and hybrids They are quite easy to work with ,more or less similar basis to FET design although obviously don’t have depletion or enhancement capabilities
Yes it’s terrible and I am also really truthfully disappointed in some of them to say the least
Still not to worry one of these days they may even get something right In the meantime of course yet another person gets ripped off by these people
Finally of course they then wonder why their businessmen are attacked treated with extreme violence and riots erupt Not really surprising is this anymore dare I say another situation such as Greece with recent highlights of course In Brixton , Eltham etc In London UK also I might add the state of the NHS system in the UK People contracting MRSA , going into hospital for lumber punctures and leaving unable to walk left as cripples with of course no responsibly being accepted by these so call departments who are shall we correctly and politely say are the so called leaders in society in general
The nice thing about the Valvecaster is that it doesn't require high voltages.It uses a 12AU7 tube, which only needs 12VDC. It can be built as a stompbox and set on the floor next to your other effects. You can use one tube or chain a couple together. It uses minimal components and decent tubes can be bought for as little as $10.
