Tube Amp Archive

Here you are. I didnt change the saturation voltage, I don't expect a big change due to Ug2 =280V. Please keep in mind that this is a design aid estimation only. But it gives a good indication what will happen.

You should be able to get about 100W. Please see the result of my rough design aid estimation. Due to the low Ug2 I expect a relatively high saturation voltage of the plate (100V) which limits the output power.

With 505V for my HT is it possible to achieve 80-110W? Some comments to the OT: First some background about this tube from my own experience. The KT120 is very sensitive against cathode current overdrive. Heavy violation will kill this tube within hours. From the datasheet: Ik max=250mA If you want...

would you have a schematic diagram of that circuit that you could post? Only ones I've seen have been bits & pieces; no practical circuits with components values and that actually have been proven to work well... Thanks :D TT Have a look here http://music-electronics-forum.com/t28617-post360510/#po...

I have done some KT150 tests during the last year published here http://www.diyaudio.com/forums/tubes-va ... kt120.html

The 68K is the grid stopper. In addition there should be a resistor from grid to ground - before or after the grid stopper.

I assume that the grid resistor is something like 5 or 10 MegOhm. This mode is bias via grid resistor.
As an example have a look at this pdf, page 2 http://www.mif.pg.gda.pl/homepages/fran ... /12AX7.pdf.
Look at the table, the last 4 rows show this mode.

Stevem wrote:Can we talk some about the phase change that takes place as the signal goes thru coupling cap after coupling cap?

> have a look here http://www.electronics-tutorials.ws/fil ... ter_3.html

David,

to prevent pop noise during switching bridge Relay 1A with e.g. 47K (high value compared to 1K5 cathode resistor of V2a). Then the cap 1u is loaded all the time.

Hans- Georg

Looking to the Picture : Where are the two 33uF caps to filter supply D and E?

In all of these cases your negative feedback was turned into or was accompanied by positive feedback, which is required for oscillation. You are right, I should have been more precise: the design faults has lead to a condition of a total phase shift of 360 degree while having an amplification >=1 a...

Regarding NFB and oscillations here is my observation after successful building tube amps (as a hobby) for about 40 years: - for sure you can get oscillation caused by NFB, I had it more than enough especially in early times - there were different root causes: e.g. wrong cabling structure, too much ...

There is no general rule like "if no load then the amp will blow up". The most critical situation is when at full output power you loose the connection to the load during a current peak at the secondary. Then you have induction peaks of up to several thousand volts at the primary side of the OT. Thi...

Some technical background, these diodes indeed are intended to protect the OT: Assume the following scenario including a descriptive explanation what happens: You are running the amp with full output power then suddenly the connection to the speaker gets lost when you have a current peak . Now the O...

Screen resistors reduce the voltage at the screen especially at medium full power as a type of safeguard for the screen. Most of the time the power stage tubes are working in class B. In fact most of the time the current is flowing only through one side of the PP stage while the other side is switch...