Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: floyd on March 02, 2013, 08:09:41 am

Title: Fender EC Vibro-Champ schem
Post by: floyd on March 02, 2013, 08:09:41 am
http://forums.fender.com/viewtopic.php?f=13&t=72304&start=30 (http://forums.fender.com/viewtopic.php?f=13&t=72304&start=30)         There may be some interest in this...scroll down a bit to see the schematic. The schem I posted below is not legible.
Title: Re: Fender EC Vibro-Champ schem
Post by: phsyconoodler on March 02, 2013, 01:36:46 pm
I played a couple of those amps at a local guitar store.They dropped the ball totally on those amps.
  They sound awful at best. They are not even near as good as some of the builders here at Hoffman build.
 The speaker is also totally wrong for the amp. A G1265 Celestion? What were they thinking?
My 5E3 builds are superior in every way,same as many of the talented builders that lurk on this forum.

 A dismal failure as far as I'm concerned.

Same with the other EC Fender hand-wired amps. They sound pretty bad.
Title: Re: Fender EC Vibro-Champ schem
Post by: kagliostro on March 02, 2013, 02:04:51 pm
May be this is more readable

K
Title: Re: Fender EC Vibro-Champ schem
Post by: floyd on March 02, 2013, 04:18:33 pm
I played a couple of those amps at a local guitar store.They dropped the ball totally on those amps.
  They sound awful at best. They are not even near as good as some of the builders here at Hoffman build.
 The speaker is also totally wrong for the amp. A G1265 Celestion? What were they thinking?
My 5E3 builds are superior in every way,same as many of the talented builders that lurk on this forum.

 A dismal failure as far as I'm concerned.

Same with the other EC Fender hand-wired amps. They sound pretty bad.
Yes , of course it's awful , but Fender promotes this as " output tube bias modulation", when I think it's just a Vibro -Champ trem circuit. The negative feedback in the 5F1 vs. VibroChamp aren't the same , so, the 5F1 with trem , is naturally going to sacrifice the original nice Tweed Champ tone.
Title: Re: Fender EC Vibro-Champ schem
Post by: floyd on March 02, 2013, 04:44:29 pm
I played a couple of those amps at a local guitar store.They dropped the ball totally on those amps.
  They sound awful at best. They are not even near as good as some of the builders here at Hoffman build.
 The speaker is also totally wrong for the amp. A G1265 Celestion? What were they thinking?
My 5E3 builds are superior in every way,same as many of the talented builders that lurk on this forum.

 A dismal failure as far as I'm concerned.

Same with the other EC Fender hand-wired amps. They sound pretty bad.
We're talking about a 5F1 , not a 5E3, but of course your sentiment is right, the EC line is disposable hype.
Title: Re: Fender EC Vibro-Champ schem
Post by: HotBluePlates on March 02, 2013, 08:25:58 pm
... Fender promotes this as " output tube bias modulation" ...

The trem is applied to the 12AX7 stage ahead of the 6V6.

... I think it's just a Vibro -Champ trem circuit. ...

It's the same, except the Intensity is fixed at a bit below full-up. Which doesn't seem like a good idea to me.

Cathode bypass for the 12AX7 stage it's injected at is also a bit large, but the trem frequency may be low enough it doesn't matter.

The negative feedback in the 5F1 vs. VibroChamp aren't the same ...

If you assume the same output power and speaker impedance (and therefore the same voltage at the OT secondary), the blackface VibroChamp has less feedback than the 5F1 Champ. And the EC VibroChamp has even less feedback than the blackface VibroChamp.

This assertion is based on figuring the resulting voltage if the same signal is applied to each amp's feedback voltage divider.
Title: Re: Fender EC Vibro-Champ schem
Post by: Willabe on March 02, 2013, 09:25:21 pm
May be this is more readable

Yes, thank you K.


       Brad      :icon_biggrin:
Title: Re: Fender EC Vibro-Champ schem
Post by: DummyLoad on March 02, 2013, 11:19:16 pm
yes K thanks! much more readable...

btw, what 's the EC stand for? Extra Crispy?

--pete
Title: Re: Fender EC Vibro-Champ schem
Post by: floyd on March 03, 2013, 08:00:09 am
yes K thanks! much more readable...

btw, what 's the EC stand for? Extra Crispy?

--pete
extra crappy