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Ampeg SS140C issues

Started by scott.sevall, October 24, 2015, 09:29:11 AM

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scott.sevall

Hi there. So I own a Ampeg VH140C that sounds monstrous. More gain than anyone would ever need with the gain on 6. Chorus sounds good and on the lead channel if you pull out the chorus knob it boost the volume even with chorus on zero. So I saw a SS140C on Craigslist for a good price. And it sounds similar but with the gain on 10 it's barely enough... sounds like my VH with gain on 3.
So issue 1. Low gain.
Issue 2. With chorus on it lowers volume of entire amp.
Issue 3. When turning amp on there is a LOUD pop. Bad on speaker cab. I can plug the cab in after I turn the head on to avoid the pop but I know this isn't right....
I love my VH140C but this SS140C sucks. Any ideas?

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J M Fahey

Start by hunting both schematics (Mr google and Miss patience are your friends) and post both here, so we can compare them.

scott.sevall

I've got both. But I'm a Ludite and can't tell what's what. I've talked to other owners of both amps and have been told the VH has more gain. But the POP when turning the amp on and the total volume suck age when the chorus is on are my main concerns at this point.

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Enzo

Hi Scott.

That is why JM Fahey asked if you could POST the schematics so we might have some idea what the circuits are you'd like to discuss.  Or at least link us to them.  I think I have them on paper, but they are in my shop miles away, and I can't post paper copies myself.

One thing about speaker pops.  On a solid state amp the limits are the power supply voltages, which are the same limits the amp faces making audio.  In other words, the pop is no louder than the amp cranked to clipping.  if the speakers can handle the full power of the amp, they will handle the loudest pops it can make.

I don't remember on this one, but many chorusing amps with two speakers have two power amps, one per speaker.  And when chorus is on, the dry signal feeds one speaker, and the chorused signal feeds the other.  So when you lose volume in chorus, listen carefully and tell us if one of the speakers goes silent when in chorus.

scott.sevall

#4
Okay. I'll try to attach them. The amp does have 2 separate power amps to make it stereo. Both my VH and SS are heads. There are a dry speaker outputs side and a chorus outputs side. The level of the amp is the same on both the chorus and dry sides. Until I pull the knob out to engage the chorus. Then there is a drop in volume in Only the lead channel.

scott.sevall

#5
Also... issue 4. There's a pretty good lag time when switching from clean to lead...

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scott.sevall

#6
http://javajunkiemusic.com/Audio/misc/     theres both the VH140C and SS140C  schematics

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scott.sevall

Quote from: Enzo on October 25, 2015, 03:49:11 PM
Hi Scott.

That is why JM Fahey asked if you could POST the schematics so we might have some idea what the circuits are you'd like to discuss.  Or at least link us to them.  I think I have them on paper, but they are in my shop miles away, and I can't post paper copies myself.

One thing about speaker pops.  On a solid state amp the limits are the power supply voltages, which are the same limits the amp faces making audio.  In other words, the pop is no louder than the amp cranked to clipping.  if the speakers can handle the full power of the amp, they will handle the loudest pops it can make.

I don't remember on this one, but many chorusing amps with two speakers have two power amps, one per speaker.  And when chorus is on, the dry signal feeds one speaker, and the chorused signal feeds the other.  So when you lose volume in chorus, listen carefully and tell us if one of the speakers goes silent when in chorus.
Enzo. Is,there a fix for the pop? And no speakers go lower.. the entire volume drops when the chorus is engaged. Not a lot but it's noticeable. On my VH140C the chorus actually boost the lead channel... opposite with the SS140C

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Enzo

Pops come from several sources, but I have no offhand solution because I never considered it a problem.  Pops can come from the brief moment of instability in the amp as the power supplies come up or go down.  Other pops come from the little spark inside the switch a the current is switched, and the circuit amplifies it.

Just as an experiment, pick ONE of the speakers and reverse the wires to it.  It is just possible we have a phasing issue.  And if not, the wires are easily returned to the way they were.

Isolate the problem, there are FX sends for each side are there not?  Run a cord over to some other amp, and listen to one side only as you switch chorus off and on.   Does that signal reduce when chorus is on?  Now the other side.