Any thoughts on the HiWatt preamp schematic here?

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9/2/2000 7:51 AM

Steve A.

Any thoughts on the HiWatt preamp schematic here?     So what is this preamp like? Has anybody tried it with a cathode-biased EL84 power amp? Any tweaks or mods recommended? How does the signal level from this preamp compare to a plexi or a BF Fender?     " target="_blank">http://www.ampage.org/schems/hwpre.gif">     --Thanks!     Steve Ahola     P.S. It is interesting how they mix the two input channels... just a single 100k plate resistor going to pins #1, which is jumpered together to pin #6- right?

 

9/2/2000 8:13 AM
PeteR	Steve A,   I had to go and check my schematics - I've never noticed that before. Interesting isn't it?   Sorry, no idea how it compares but I'd like to!   Pete

 

9/2/2000 2:52 PM
Carl Z	Steve;     I cobbled this design together a couple years back and it's bright as hell! I never really did much with it so there may well be something tasty that can be wrung out of the design.     Yup, you've got the wiring right. They're just paralleled stages. If I remember right Ken Lewellen used a similar arrangement with a CF in one of his amps.     Carl

 

9/2/2000 4:03 PM
Corwin	That schematic isn't the full monty. there's 2 stages missing after the tone stack. the full schematic is at Andy Ruhl's Machine Gun Amps site. I can't remember the URL though. there's a link to it on Steve Ahola's page.

 

9/2/2000 4:26 PM
Carl Z	Corwin;     Yeah, it's only the preamp. That phase inverter is real different from the standard FMV stuff. That's most likely what's primarily responsible for the sound of these amps.     Carl

 

9/2/2000 4:55 PM
Steve A.	Carl, et al:         Here is the current link to Andy Ruhl's site:     http://www.users.uswest.net/~aruhl/mga/         Definitely a different animal... I bet Randall Aiken could write a few articles just explaining the circuitry to us!     Steve Ahola

 

9/2/2000 8:05 PM

ChrisW

Steve :     There's also some gain ( the ECC83 right after the master-volume-pot ) before the p.i. .     I don't know the H.W.s but I did hear and read that they have very nice clean and crunch sounds . Compared to a 5F6A or AB763(without reverb) it does have an extra circuit between the pre-amp and the p.i. .     Design-wise you can compare the shared plate-resistor to the shared cathode-resistor from the 2nd preamp stage from an AB763 circuit.     Give it a try .....     Have a good time !     Chris

 

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