Hi All,
New to this forum, but need some advice from amp techs/builders:
Fender '57 5e5a re-issue eyelet board / handwired.
I have modified the preamp to be more like the more basic 5d5: -
V1 - Was - 820r 22uF - 12AY7
V1 - now - 470r + 22uf - 5751
V1 - Intended - 470r + 25uF - 5751
V2 - was - 1k5r + 22uF - 12AY7
V2 - now - 470r + 22uF - 12 AY7
V2 - intended - 820r + 25uF - 12AY7 - slightly colder bias
Will the intended changes above make any audible difference?
Do I run the risk of running the preamp tubes too hot?
Given the components have ~10% tolerance - are the above changes worth it?
**I have removed the local feedback loop in the preamp - removed 4.7m and 220k completely
PI was - 12Ax7
PI now - 5751
(PI appears to be fixed bias)
As I am reducing gain in the the 5881 tubes, do I run into a bias issue? The power amp is converted to cathode bias and running 470r 5 watt resistor and a 25uF 50v cap (measured at ~30v - hence the larger v cap)
The amp absolutely roars and sounds phenomenal at about 4-5 on the volume - huge overdrive and usable breakup. I have modified based on ear as opposed to maths, but have done the maths! However, I lack the experience to know if things are gonna go bang.
No smoke is escaping and the amp does not appear to overheat.
Comments
If the circuit is running within its own limits and you like the resulting sound, then run with it.
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
will do the math….reluctantly.
Hence the experiment. Bridging the channels is awesome - it is like a fire breathing monster!
*I also removed the bright cap as this seems to stiffen the sound and removes some ‘squelch’ from the drive sound.