Dave Hunters tube amp build questions

[Rybow]

Hello everyone. I am going to start building Dave hunters two stroke amp in the next couple of weeks, but I have a few questions about the build. I want to make sure that the amp is high gain friendly. I don't want to turn the amp into a high gain monster or anything like that, but I just want to make sure that when I dial in some molten gain, the amp will respond in a satisfactory way. I must admit that my experience is limited, and this will be my first major project. On to the questions.

Rectifier- The design calls for a tube rectifier. I have never played an amp with a tube rectifier, but I know that most metal guys don't like the sag that occurs when a strong signal hits the rectifier. How difficult would it be for me to wire in a solid state rectifier to a switch so that I can switch between solid state and tube rectification? Are there rectifier tubes that have better response than others? Are rectifier tube types swappable?

Transformers- The design calls for hammond transformers that are an open design for that vintage sound. If I wanted to change the transformers to a more modern sound, what type should I be looking at?

Cathode bias- I have read some varying information on this one. The amp design does incorporate a cathode bias. As I understand it, a cathode bias will automatically adjust the bias as long as the tube falls within the range of the bias resistor. Is this about right? How is a cathode bias adjusted if the tube is outside the range?

Thanks in advance for all of your help everyone.

 

[Davo]

Hmmm.... looking at the Dave Hunter, it looks like it's a hotrodded 5f2a (fender princeton)
I built one of these guys last year, and if you're looking for a modern/high gain type of sound,
this isn't the amp to build.... this has a really fat vintage tone.... of course, depending on the OT, speaker
etc. you could lean it any way you want.  Fantastic sounding amp as it is

 

[Rybow]

Thanks or your reply! Thats just it. I have heard sound samples online, and I really love the sound of the amp. Its just what I am looking for in terms of a clean amp. When I need some more gain, I will be using pedals to supercharge the gain, but not to any extreme levels, just to get a good solid crunch.

What speaker did you pair your build with? I was thinking about going the greenback route, but I am not sure. My experience is limited to using amps that are 50 watt plus.

 

[Davo]

You definitely won't be disappointed with this amp!
The speaker I'm using is a 30w weber blue pup... alnico... it's a good speaker, maybe a bit fatter than your average fender,  I think
the original used a Jensen.... Weber sells the 10A125 which would work well in this application
Good luck with your build!

 

[PRR]

> I want to ... dial in some molten gain
> switch between solid state and tube rectification?
> change the transformers to a more modern sound,
> this will be my first major project.

For a first-timer, you are over-thinking.

If you MUST have the 1999 end-of-era crunch, this may not be the amp you want.

There are billions of DIY amp projects. It will take more than one build to dial-in "the" sound you want. I know guys build dozens of amps, keep some, sell or trade the ones they don't like to someone with different taste who loves it.

OTOH, a $69 pedal can dial-in 99 different classic distortions, and the Princeton will play what you feed it, competently.

It is a good solid amp, a well documented project. It WILL serve you well as a small sweet amp, can do dirt too, and is an excellent way to get addicted and build more different amps.

> How is a cathode bias adjusted if the tube is outside the range?

If one tube won't bias-up, throw it away.

If all tubes bias badly in the amp, change the B+.

A happy self-bias amp has a relation between the load impedance and the cathode resistor. And tube parameters, but the critical Mu(g2) is quite consistent among all 6V6, all 6L6, or whatever type the amp was designed to use.

So stick in a tube. If it red-plates, or plays weak, try another tube, this one may be sick. But if several samples of the same type all have the same mis-bias, the amp is out of balance. And if Rk is about 6% of Rl, yet all tubes red-plate, then the B+ is just too high.

There ARE forums for DIY gitar amps, where you find large numbers of rabid builders swapping tips and tales. This forum attracts more microphone and studio-gear types.

BTW: a single-ended amp (the 2-stroke is SE) doesn't "rectifier sag". That only applies to big fix-bias push-pull amps.

 

[Rybow]

I will certainly look into Weber speakers Davo, thanks for the reply!

You are right PRR, I am way over thinking this build. I know there are lots of DIY amp projects out there, but none that I've found are as well documented as this one. So I figured it would be a good place to start. I will build it as per the instructions, but I am going to make it into a head instead of a combo amp so I can easily try out different speakers and what not, but thats the only thing I am going to do thats different then the stock design. Thanks for setting me straight man. I needed a reality check. I will take a look around the net for an amp building forum. Thanks again.