Tube Amp Archive

The Amp I for Hi Fi use. Screen resistors are really needed to help prevent instability. By using both cathode Feedback from the OPT Sec and screen UL Tap's on the transformer, The Tube and transformer are interlocked in a localized feedback loop around the Output stage so the screen resistors act a...

Cliff Schecht, Thanks! Yes i am using the 1650P along with the 372JX Power Transformer rated at. 243VA, 300-0-300 @ DC ma 250, 5VCT @ 4A, 6.3VCT @ 8A. the 1650P secondary is connected for 16 ohms so This would make the Reflected Primary Impedance 3,300 Ohms with an 8 Ohm load, I am thinking that sho...

Thanks for the Tip however I am not Interested in other Topologies I am doing this one at the moment?

I have finished an EL34 Ultralinear push Pull Tube Amp and would like options on the Ideal DC Operating Voltages of the Amp shown in the schematic. Thanks for Looking

I have got the Preamp almost together. I am putting it on a PC Board. I also tried connecting the Sup Grid (g3) to the Screen's (g2) and no misadventure results it dose slightly shift the DC operating points and these will have to be compensated for. As for change in Tone yes it did change it slight...

the C from G3 to the cathode is the standard screen Bypass cap, however again I returned this to the cathode rather than ground so as to improve its bypass capability and if needed re sized for HF Roll-off. I haven't got to the point of measuring this yet it is not quite ready for prime time. (1) th...

Hears My Preamp I have been Playing with this last weekend, It has the bass and treble controls inside the feedback loop for fast articulate tone response. it is a (2) two stage design using a cascode Input driving a pentode Output in what I call my APHEX circuit. I would like to have (2) two of the...

An old yet Informative site is Jukka Tolonen Tube DAC pages has great Info on what we are talking about. http://koti.mbnet.fi/siliconf/JukkaTolo ... part1.html

I installed one EF184 and left the remaining cascoded 12AT7 in the Other Chanel so I could compare the two.

ya tubes are somewhat forgiving of abuse so can't hurt to test. I am thinking of replacing the 12AT7 in The 777 Amp to a EF-184 and see how that performs. This will give me a seat of the pants feel for the Clean tone difference between the 12AT7 and EF-184. Apparently the EF 184 is starting to gain ...

Andy are you sure you can connect the Suppressor grid to B+ I always amused perhaps incorrectly that the Suppressor grid and Beam forming plate be connected to Ground and in some instances at a potential slightly above Ground like 12 volts? I have a friend that Plays Acoustic and he is begging me to...

Thanks mike for the 6L6 Print. My love for cascodes comes from my previous Solid State background as did my Love for Multi-Loop feedback systems. Yes Mr. Crowhurst Inspired me a lot. http://www.scribd.com/doc/27573111/Crowhurst-Cooper-1956-High-Fidelity-Circuit-Design. Also Walt Jung had my interest...

Hi Andy, yes the DC Bias voltage of V1’s cathode will be present upon the Input grid of the next stage. Since this affects the DC Bias of V2, you will need to adjust the cathode resistor of V2 to maintain the same Grid to cathode voltage for V2 as was without the mod. AC Phase relationships are the ...

The Attached Circuit I think You might find useful it takes the cathode regulation concept further and adds Ultra linear operation to the Picture. You trade gain for linearity however output swing is not limited but is in fact unproved. Note the grid leak of the following stage after the coupling ca...

FWIW, I am a huge fan of this cascode 6DJ8 design, and I am putting it in many of my production amps. I have been meaning to try it with a 12AU7. I think this is an unfortunate neglected gain stage design that has a lot to offer. I have used the 6DJ8 and 6922 in the standard Ultra linear cascode. I...