The Amp Garage

Am I the only one who finds it funny that etiquette is being discussed at a site devoted to piracy?

I don't know about that particular amp but I had to fix a svt4 this week and found a free schematic at www.eserviceinfo.com

Thats right about the mismatch - higher Zs make for generally higher voltages and increase the probability of arcing. Often the socket or tube base is the weak link. This is just about words, but the culprits are voltage spikes -- not flyback. Spikes in the couple kV range are normal in tube power s...

If you use a Mesa Boogie, it is not smart to use anything but their tubes. They cover damage as a result of tube failures, which are not unusual in some models and can be extremely expensive to fix owing to the type of designs they use and the cost of parts if a board is burned or transformer needs ...

Speakers have two power ratings. The one they tell you is how much current the voice coil can handle before getting too hot. That is rarely how speakers fail. The real power rating is much lower and involves how much excursion they can take before they max out and deform, start rubbing, or get stuck...

[I guess as a bass player of over 35 years experience I need to speak up now. Not necessarily true.The right bass speakers operated in a properly designed cab are easily as efficient as guitar speakers , if not more. The BP102 is not a good bass driver. I only mentioned the BP102 as an example. The...

This may not be of interest but there is a dude in Australia (ESP) that sells nice transistor diy boards. I've used a 100W board called a P3a a few times to repair/refurbish old Polytone Minibrutes with good results. Also... there are two reasons bass amps require more power than guitar amps. One is...

Since rp and mu vary between tubes and with signal level, combinations of tubes never give the full output you expect on paper. I way prefer the clean of a Twin to a Deluxe. The two speakers are a big factor but the more complex output stage definitely adds some "tubey-ness." A funny thing about thi...

Nobody asked, but some more thoughts... The reactance of a .02 uF cap at 60 Hz is about 100 kOhms. So even if you were soaking wet and touched a "hot" chassis, (such as the Alamo mentioned above) the current through the cap shouldn't exceed about 1 mA. Although its annoying when you get it on the li...

Why would this amp come with one on each side of the power cord then? The theory behind using two caps is is that you accept some hum (voltage-wise its exactly in-between the worst and best case) for the simplicity of getting the same result regardless of plug orientation and not needing a polarity...

[I will either acetone or fabric soften the SPIDER!!! Anyone screw with the spider for speaker breakin accelleration? No, but the spider is responsible for most of speaker stiffness, so if you can find an easy way to modify it, it makes more sense than messing with the surround. By the way, I think...

The rule of thumb is that the plate resistor is twice the rp of the tube, and that the downstream load is twice that. The whole idea is to keep noise down by using the smallest resistors you can get away with and still have a gain that is a reasonable fraction of the tube’s mu. The main reason for u...

I just re-labeled my speaker phase switch "suck" and "extrude." Much better than plus and minus.

It would be cool if there was a way of mis-wiring an amp where it would actually suck all the sound out of a room.

Could be any number of things but a problem I've seen several times in that amp is the preamp supply caps coming loose on one side. I mean the big caps over by the inputs. I think there are two. It makes a static noise that is vibration sensitive and tends to be most audible when notes are trailing ...

Thanks martin (for doing and sending the THD calc privately sub rosa.) I only realized after looking it over that what I asked is a real perplexing conundrum. I think the method you used involves the largest signal that doesn't clip. But since that signal is different for different Q points you can ...