2. amps-preamps
  3. 194065-38016

Speedboost or other lps for Hagerman Trumpet MC

I have been really enjoying this unit so far and now have Tele ac7 smooth plates (curve trace matched low noise and non-microphonic, thanks Brent Jessee) and a fantastic pair of Valvo e82cc triple mica in the au7 sockets.  I think I have the tune combo I want.  
I have read about folks using lps for this phono stage and I am a little confused as to how it could make sense since the power supply in the Trumpet MC is a switching one.  Can anyone explain how lps would affect the onboard power supply or would one need to somehow bypass it, and if so how would you do that without rebuilding the unit?

lastly I saw @lewm  recommend 12fq7 as a substitute for 12au7.  Looking at the data sheets, they are similar with identical on out, but not identical.  Has anyone tried this and if so what was the result?  Sheesh, guess I am not done tube rolling after all.

thanks 

oceanica
oceanica OP
35 posts
 

Sorry, spell check, jfets not jets.

mulveling's avatar
mulveling
2,190 posts
 

@mulvelimg, that is what I was getting at with my question.  With the jets and the 555 chip.  I couldn’t see how an external LPs could get around the internals in the unit.  The external LPS would end up in a switching circuit to get the rail voltage required.  
On another note, what have you found works best in the v2 position?  12ax7 tube.  I want to confirm what this position is for.  Looks like it handles phase correction.  But I am not very good a reading schematics.  Any suggestions?

At least it’s not switching on wall AC anymore? :)

I’m not going to hazard a guess at the 12AX7 parts of the circuit; I’m a software engineer not hardware :) 

I’ve always liked more incisive / detailed tubes to balance the Trumpet’s inherent warmth. Telefunkens and Mazdas are great for the 12AX7 slots. I’ve run Mazda silver plates front row and Tele ribbed plates in 2nd row. That seemed to be best. Tele smooth plates it you want to slide a bit more back into warmth. 

oceanica OP
35 posts
 

Thanks,

I have tried several variations.  So far running Tele smooth plates in the v1, and a pair of Raytheon 7025 in the v2 (have another pair of Tele coming to try there.  And a pair of Valvo (Siemens made) E82cc triple mica in v3.  The Valvo replaced a pair of Mazda pinched waist Ecc83 and are an improvement.  You might want to try them if so inclined.  Thanks for the feedback.  
 

oceanica OP
35 posts
 

Sorry, 7025 are Sylvania not Raytheon.  Spiral filiment low noise non-microphonic made for Baldwin.  

More to discover