Hi Guys Is the 10k resistor replacing C105? If so, it is there to add compliance to the clipping. This softens the sound as TUT explains. Oddly, on the schematic, beside the designation for R104 is written 1nF-50V. This cap - were it in the R104 position, would also soften the distortion a bit. Have...

Hi Guys Do you mean MG15CDR? If so, then the problem is likely the output chip TDA2050. You can also check voltages inside the amp with no speaker connected. make sure both supply rails are intact. Like most circuits based on the manufacturer's app notes, this one does not have a leak resistor from ...

Hi Guys Actually... the risk of saturating the output transformer due to mismatched currents is not something to worry about. Balanced splitter halves, balanced coupled caps, balanced dynamic performance of output tubes are almost all things that you don't want in a guitar amp. These are things that...

Hi Guys To those who thought they were wrong: you are actually right. Steve's response was a bit heavy handed inasmuch as making a blanket "wrong-ness" statement. The bias pots let you balance hum. They also allow a higher percentage of available tubes to be used in the amp, provided there is suffic...

Hi Guys The ethical points have all been covered more or less: Behringer is an outright thiff, copying everything created by others and occasionally coughing up a new product of his own. Bugera is just Behringer in not-sued-yet-by-the-FCC clothing. The Blackstar guys ran off with Marshall's vendor l...

Hi Guys

Well, one of our Power Scale kit customers told us that the kit and installation cost him about half the price of a Hotplate.

So, there is "inexpensive" and "even more inexpensive".

The proof is in the listening.

Have fun
Kevin O'Connor

Hi Guys How attenuators operate, the nature of sound, how Power Scaling works and many other things are explained in great detail in TUT4 (The Ultimate Tone vol.4). With Power Scaling, only as much power as you need is generated and the amp is solidly connected with the speaker. The amp-speaker inte...

Hi Guys Fact is you wont be getting any of these sounds even if you buy a YJM. ´got a 1959 amp and been trying to nail Brian Robertson of Thin Lizzy´´s tone for many years but it never sounds the same. Many guitarists back then used effects, boosters or other tricks to get their tones. There is rath...

Hi Guys Hey Phano36: Check if the pop occurs when the boost is not selected, or if it makes a difference. The jfet referred to by Steve is normally-off. Two comparators are set up as a window detectors, where upper and lower voltages are ignored but a signal within the window causes one or the other...

Hi Guys To my eyes, I think the OD selection could have been improved and the feed-through problem eliminated by design. The first relay in the signal path sends the first-stage signal to either the clean EQ or to the OD Gain control. This is a series switch. The load of the EQ is disconnected from ...

Hi Guys

Lift one end of R52 to hear the loop without the treble emphasis.

Have fun
Kevin O'Connor

Hi Guys As detailed in TUT4, the UA is far from "ultimate". It was designed by Ho in Vancouver, BC, a repair tech who modifies amps and custom builds odd items. The UA guys copied it and made no improvements despite adding a "voice" switch. The unit provides a 30R load to the tone amp - a common val...

Hi Guys The line output is simply a divided version of the speaker output - two resistors will suffice, or a resistor and a pot, or just a pot. You will want to EQ it for recording and most other purposes. If you want a ground-isolated line out, use a small transformer such as the Hammond 109T or 10...

Hi Guys To make the attenuator variable you need a rheostat rather than a pot. A pot is usually a carbon or plastic film element that cannot handle the currents even of a 5W speaker output. A rheostat is also called a "wirewound" potentiometer as the element is literally a coil of resistance wire. Y...

Hi Guys "Why is the difference in tone so little when i turn up the JVM 410H to 10 but so big when i turn up my Marshall plexi reissue to 10? Why does a high gain amp like the JVM tend to distort the output stage less than a 1959 plexi wich has less gain?" Amps designed with a master volume have pre...