Recent content by Eddie Spitzer

I can't speak to Mr Peavey's successes or failures as I don't know the man or his company. I do know that I achieved far more than I ever set out to do which was to make a line of hand made tube amps for my retail store. What started as a back room project turned into a user group including the...

By those standards Peavey would be the best amp. There are certainly tens of thousands of them that all sound the same.

I can't speak to the issue of DFM. I never designed for manufacturing ease or production yields, Only for sound. I'll leave the production techniques to the corporate guys. If I wanted to build for production I would just use 4558's or whatever the modern op-amp is.

It sounds like we agree on more than we disagree on. I also have been working in the industry since 1971. Can we agree on this: The 12AX7 is a high-gain pre-amp tube that is notoriously prone to microphonics and thermal drift. It requires carefully designed external circuits to maintain...

Were you with Boogie in that era?

The trick of using solder on board traces to correct layout errors in tube circuits was first shown to me by an assembly tech at Bell Aircraft who built 1950's guidance systems out of tubes and circuit boards which was brand new tech at the time. Later, a guru at General Dynamics that used tubes...

That's a nice assurance. I got the same assurance from Carvin about their Nomad amp. Anyway, I owned and ran what was left of Prune Music at the time in San Anselmo, was a Boogie dealer and shared a workspace with the most famous of Boogie's design team so I know exactly what went on. Cheers...

I define RF, in this case, as any unwanted frequency that causes intermodulation distortion. The solder is not regular in shape and even though it thickens the trace, which you would think would exacerbate the issue we found the irregularity disrupts the trace's ability to form a capacitor. I...

It's pretty well known now. If you google, "will 12AX7 triodes that are run beyond the manufacturer's spec produce RF on circuit boards" it will open a line of knowledge. I built the amp you are looking at 40 years ago. At that time the only audio people that knew about RF on tube circuit boards...

Pushing a 12AX7 twin triode beyond its design limits will cause non-linear clipping, which generates high-frequency harmonic overtones. If the circuit has high stray capacitance, this will lead to parasitic oscillations, unintentional RF signal generation and Miller Effect. The solder on the...

Thanks for the input. New perspectives are always welcome. Your point is exactly my point, solder is different from parallel traces and putting the solder on the traces makers them act differently than traces left bare or covered in solder mask. On the second point the technique, as a layout...

Yes, parallel traces on circuit boards form capacitors. Whenever two conductive copper paths run parallel to each other and are separated by an insulating material (like fiberglass or solder mask), they act as a capacitor. Those capacitors cause high gain audio pre-amp stages to oscillate. The...

We used a lot of solder back then. It helped with layout loops and gave the amps an unmistakable sound. Stupid looking now that I look back at it after 40 years.

That amp was built June 23, 1987 in Hayward, CA. It was the first amp of the day. That amp, or an amp just like it was used on the Joe Satriani, "Surfin with the Alien" album for the bass tracks. Probably why it was saved for 40 years. Contact me and I will add you to the registry of users. Eddie

Made by me, not the case, Eddie Spitzer about 1986. If you like, contact me. I keep a registry of users.