Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frank57 on May 01, 2011, 08:52:48 am
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How big a role does the Hiwatt phase splitter play in the Hiwatt sound?
It sounds like a big role I think.
I tried an experiment on my little Hiwatt .
It might be an edsel but what the hell.
I stripped it down to 2 stages, bypassing v2b and getting around the efx loop.
I also made a few changes here and there.
A lot of the noise and so on are gone in this experiment,(unless you really put everything full blast)
but what's obvious is how clean the hiwatt phase splitter is.
Even with 2 220k plate resistors and cathode caps, if you put the master fairly low and gain at 10, there is breakup, but you have to hit the guitar pretty hard or,
start turning that Master way up to hear it.
You really have to put that gain way way up there and turn that master up some.
More of a power tube distortion?
Is that typical of a Hiwatt?
(I also changed a filter cap in the front to 47 from 22 and that helped a lot as well as changing the tone stack a little for the noise.)
(On the face of it you would think 3 stages might work, but obviously that middle stage is a big problem in the 3 stages version as originally designed unless there is a pcb problem there as well.
I f you start to change it or use a lower gain tube there then the amp starts to work better.)
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A 12AT7LTP driven by a CF stage? I'd say that'd add a bit of character. (Use of the 12AT7 LTP alone would make it quite a bit sweeter. Here's an experiment - if you have some LTP inverter amps lying about, put a 12AT7 in that slot and see how you like it. I did this a while back with a bluesbreakery clone I made and I quite like it. No special changes are required to the circuitry to try this.)
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The cathode follower is only to DC bias the phase inverter- no signal goes through it. It's Hiwatt extravagance!
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A 12y7 in v2 in the original setup does help, but it's still noisy past noon.
It's odd because if you take v2b out of the picture and leave the two 470k resistors there on v2a you have zero breakup even with the gain at 10.
The two stages version actually has some decent sound going but you have to turn the master up a little
say around 2-3.
Does anybody know where I can post a soundfile?
I tried a few places but when you use the link it just goes round and round forever.
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Does anybody know where I can post a soundfile?
http://www.mediafire.com/
Kagliostro
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Here's a short test rhythm sample.
From an interview I read with the audio Brothers, the phase splitter at 70 volts keeps things super clean everywhere.
Even with the gain on 10 and master at 2 or 3 you can actually play clean.
It's very very pressure sensitive.Whack it good and hard and it distorts, play normally, very clean.
Although you don't hear it in this short test.
I have a few other short test files, so we'll see if this works.
All controls high noon no pres.
Short Who song.
Master 2 or 3 gain 10.
http://www.mediafire.com/?0f4ela4im33a6eb
The phase splitter in this amp is a 12at7 by design.
I suspect that something is wrong in the middle stage area in the 3 stages versions.
Or they should have gone from the cathode before the tone stack.
I've got a clip of the original problem but I have to find it.