#164568  by Pointclear
 Sun Feb 03, 2019 8:28 am
Great info mike. I am familiar with the way capacitors work in series/parallel etc, now. I actually went through several configurations at the output: the .1, a .22, a .47, and the two point .1’s in series. To my ears ,for whatever reason, the two .1 in series sounds best: bass is still tight enough, and the treble is blooming a little more. I may change it to something more orthodox one day, but the other configurations were so, so bright and glaring that it was difficult to listen too. A different room or different guitar may respond quite differently. I think the volume at which Jerry played in large halls and stadiums must have done a lot to round some of the hard edges of his rig.
Regarding the ground shunt, THANK YOU for the explanation! This all means a lot to me. I’d like to set up my taps this way and pull the power tubes and speaker to see the difference in voltages/feel. But I’m hesitant to do so until I put some larger filter caps in place.

I have a question in regards to preamp voltages and transformers: I assume that the preamp is getting 400 plus volts from the twin’s power transformer. In building a small rack mount preamp, how does one get those high voltages and/or the quick response time that the big iron of the twin reverb provides with ease? Voltage doublers? Special little transformers that I haven’t discovered yet? Or Are the voltages just lower overall? This May be a question for brad, or may be proprietory info, but I think it’s worth asking since everyone discusses preamp voltage levels in regards to the feel/tone of a Jerry rig.
 #164571  by waldo041
 Sun Feb 03, 2019 9:51 am
:cool: :D

Preamp voltages are subjective to whomever is doing the work. I do it my way, brad does it his, and so on. You have to learn how to massage them to where you want them. Also, if you have the math down and already know how you like the amp, finding a smaller transformer to suit your small build needs is not to difficult to locate. I am not gonna do the research for you but alembics stancor type is something to shoot for spec wise, or learn how transformers work and browse the catalogs, there are literally thousands to choose from or custom builds are also available through places like Mercury Magnetics.

That said, I have been down this road, I am out, you got this!


~waldo
Pointclear liked this
 #164801  by Pointclear
 Mon Feb 18, 2019 10:00 am
Hi! I just wanted to update my progress with amp and the tapping of the twin reverb: I finally tapped my twin’s second channel in the Alembic way (shielded wire/shunt jack/grounding into the power amp). Anyway, it works and is great. However, I had been using an ungrounded tap previously and changed output capacitors to tube frequency response etc. I have found that the Alembic style tap with the grounding makes the signal a little less “alive” and I can finally see the need to get the output cap dialed in to tighten the bass etc.

Just wanted to chime in.