The Amp Garage

Hi guys, thank to these pages, I build a decent clone that I played for month with pleasure. Now I'd like to add some effect to widen the palette of sounds and due to the nature of the beast, I came to the wet/dry combination, so I added a line out. The idea is to pick the signal from the line out, ...

Cents are always welcome! VVR already implemented scaling the whole B+ rail. I took other measurements that confirm what has been said before about primary impedance shifting and 6k6 being too low: when in SE mode, the voltage swing goes up again doubling the impedance (16 ohm cab in the 8 ohm speak...

"Addio sogni di gloria"
Went back in the basement and took some other measurements, my God it's true!
When the two are working, the swing goes up to 300v and when one is grounded, it goes down to 200v.
So this is a dead end street, thanks for your patience and collaboration.

6k6 primary, separate cathodes, schem asap.

@Jana: if cutoff were to happen I should have seen clipping on one side of the sinewave only, as I said it's almost perfectly simmetrical all over the range of the volume pot. @Martin: I thought that grounding one grid wouldn't affect primary Z. I'm at work now, pi has 0.47uf input capacitors, 470k ...

As mentioned earlier, 3 (or 6) db more is just suiting my need to boost the solos. I used the genalex datasheet, where you could find curves for even g2=100V. The amp is where it it supposed to be except for the lack of clean range and let me insist on my primary question: why does it clip when the ...

Normal playing: one tube, clean to mean with guitar pot
Solo playing: two tubes, double power, enough boost for my needs.
Problem is that I don't get enough clean range despite biasing @ -15.

+1 for above and maybe you could find usefull the following link:
http://www.hammondmfg.com/pdf/5c007.pdf
for future reference.

Basically I want to play using one tube doing so by grounding the grid (se mode) of the other and whenever i need a boost, e.g. during solos, switch in pp mode. The choice of operating the amp in class a is because in se mode the signal is simmetrically amplified (and clipped), while in class ab thi...

Put one probe on the anode (pin 3) and the other on the control grid (pin 5), so it is only the power tube. My mistake , Rk is actually 264R. Actual measurements: Va=212 Va-k=197 Vg2=205 (500R Rs - Ig2 2.5 mA) Vk=15.18 Rk =264 15.18/264=0.0575A minus screen current (2.5 mA) gives about 0.055 mA and ...

I've scaled the whole amp and, to give a complete view of the project, it has an express pre and PI. The idea was to have more clean range using a different tube, but what puzzels me is that early clipping: why does it clip with a 15Vpp sinewave when it is biased @ -15v? In my ignorance I was expect...

Yes i can understand the points, but I was interested in Having a low power amp, class a in order to have the possibility to switch from se to pp, big bottles mainly because I thought I could have more headroom and of course for their tone. But it seems there's not all that gain in terms of headroom.

Hi, I was trying to verify the theory learned and when it comes to the power amp I was disappointed because the numbers aren't as expected: it's a class A PP KT88 6k6 OT, 200Va, cathode biased (460R and 2200uF each tube) at about -15v @ 55mA, so I was expecting a 30Vpp signal at the grid would make ...

Thanks. So, if I understand correctly, until the heaters keep the cathodes warm enough, the tubes are still working at idle and the electrons find their way to ground from the caps through the cathodes when the standby switch is placed before any cap as in the hot rod deluxe where the switch is on t...

Hi, my bandmate has the amp in the subject that was motorboating, I found it was the last cap in the chain, changed with a 33uF/500v I had at hand and the amp was better than before as this guy pointed out, and I'm glad for him. But I noticed, when testing voltages with a DMM, the voltage was going ...