The Amp Garage

Yes. The design tries to maintain symmetric clipping even in the preamp stage. One should note that Kelley ultimately prefers push-pull power stage clipping (i.e. FACS and the later "Line Amp" power amp emulation), which by its nature is very symmetric. Reputedly basis of Jim Kelley amp design was i...

Class-D is considerably more efficient than AB so I would expect a hefty increase in output power. Maybe closer to VA rating of the PT. I suppose that as long as nothing gets excessively hot, you don't crank up the amp for long periods of time, or use it as a bass amp it should run fine, though.

Free stuff: https://www.ampbooks.com (See sections titled classic circuits and technology) https://robrobinette.com/Voicing_an_Amp.htm https://robrobinette.com/Tube_Guitar_Amp_Overdrive.htm (Other good stuff too) The Preamp Stages: how they sound and why thread on this forum is also great reading. T...

No. I do not regard Russell Hamm paper a good source. It's not technically incorrect but unless it's read with a very thorough understanding (especially understanding limited choice of equipment he tested and its general bias towards certain types of circuit architectures) there's a great chance to ...

Well said about picking the right tool for the job. EL34 is a great tube for power amplification at "high" levels of current but does not excel with its capability to amplify voltage (in great ratios). Matching that to performance of 12AX7 as a preamp gain stage (or vice versa) is therefore not triv...

The diodes enforce symmetric clipping distortion. Grid conduction clips the positive lobe of the signal at threshold equivalent to approximately DC bias (cathode) voltage and some. The diodes clip negative lobe at approximately same threshold. Relying to plate clipping would produce traditional asym...

I would not regard the early 1970's Russell Hamm whitepaper as too trustworthy source of information about this topic. Most of its content was debunked already when the paper was released and there are other major issues as well, biggest one that the paper is written according to principles of high ...

Can one make an apple taste like an orange? As was acknowledged earlier, EL34 is a true pentode tube while 6V6 is a beam tetrode. They will have somewhat different characteristics of operation discussed pretty well in various literature. This site is pretty good: http://www.r-type.org/static/grid14....

I can think of one advantage: Copper is an excellent conductor due to its low resistance so if you abandon all decent grounding layouts and schemes, and just connect the grounds to closest convenient place in the chassis using the whole chassis as "ground terminal", the ground return currents will i...

There is another detail in selecting proper potentiometer taper for NFB-based controls, which is that we can't assume the amplifier is driving a purely resistive load. In essence, the control (frequency selectively) varies magnitude of NFB, adjusting effective gain of the amplifier between open loop...

For the trouble's worth, I would mount all preamp tubes, if not all tubes, on a separate metal plate, which is then fixed to the chassis with aforementioned rubber gaskets and bolts. Chassis, of course, needs all neccessary holes to acces tube sockets underneath. Bit off topic, but in my opinion you...

Correct me if I'm wrong, but I believe R.C. Ballard actually worked for RCA. So yes, the circuit is probably featured in their books etc. ...Oh, and pickups for electronic guitars were practically invented around the same time this circuit was already in use (probably in TV and radio sets) so there ...

Easily pre-dates those Gibson amps. Here's a patent applied for in 1937.

[img::]http://www.muzique.com/news/images/tone1937.gif[/img]

In practice, it's just a fader between hi -and lo-pass signal paths. You don't need to be a rocket engineer to "invent" something like that.

The following are naturally generalisations of the extremes but I hope it relays the idea: High bypass capacitance and low coupling capacitance causes higher gain (most importantly) -throughout- the effective bandwidth of the gain stage and then distinct high-pass filtering of the result signal due ...

Yes, insufficient "decoupling" - largely in the power supply circuit - can sometimes lead to resonance as signal creeps back to earlier stages through supply rails as positive feedback. This is usually an issue only when no decoupling at all is employed in critical supply nodes. In other words, if y...