Rivera era Concert amp workover

premiumplus · Post by **premiumplus** » 23 Jul 2008, 14:17

Hi all,
I recently acquired a nice '83 Fender Concert ll amp, mainly to score the EVM12L lurking within

. Here's the schematic: http://www.schematicheaven.com/fenderam ... _ii_83.pdf
It has a fair clean sound but I think the OD side really sucks. I play blues rock, and this amp was a stab, I think, at answering the Boogie amps of the period. I'm not a Mesa fan anyway but this amp kind of didn't really do it anyway.
Note the first stage. I've never seen anything like it and I think it's gotta go! Why would Rivera put that stage in parallell with itself, for impedence consideration, to drive the two tonestacks that he hooked up to it?
Also the od channel tonestack needs to go after the second or third stage...where would you recommend it to go?
I think this amp has lots of potential but it sure has some boneheaded (to me, anyway

) ideas going on. It looks like someone made a nice amp and someone else screwed it up!

premiumplus · Post by **premiumplus** » 24 Jul 2008, 12:13

Any thoughts? I'm trying to decide whether to leave it like it is and sell it or find out if it really has potential.
Thanks!

guilds100 · Post by **guilds100** » 24 Jul 2008, 19:21

I've heard one of those amps and didn't really care for it. I do believe you are right in thinking it was suppose to be compition for the Mesa Boogies of the time. There has always been alot of hype related to those amps due to the Rivera connection. If I had one I would unload it as quick as possible to someone who has bought into the hype.

AL · Post by AL » 25 Jul 2008, 16:00

Rivera era stuff seems to be highly regarded as guilds100 said. I've never played one but, personally, I'm not a fan (at all) of Fender's later stuff. I much prefer the BF and early SF amps. I'd dump it and get something else.

It looks like someone made a nice amp and someone else screwed it up!

yeah... look at any Fender at around 1976 or later. I think they were stock-piling bad ideas for several years before they decided to put them all in their amps. Have you ever seen the guts of a 70 watt Super-Reverb? Ouch !! I've been to Italian family reunions with less spaghetti.

AL

Fuzzer · Post by **Fuzzer** » 25 Jul 2008, 16:54

Here's a picture of 70 Watt Super reverb innards.

And I have to say for me, The 75 Amp (which is a Rivera-era-era-era) is a great amp, granted, the distortion is awful, because they tried to make the fender something it's not, but the clean Channel is superb, and with the pull fat boost it just rumbles. That's just my opinion though.

John G · Post by **John G** » 28 Jul 2008, 07:35

Hi,
I remember in the late eighties modding the Concert gain stage to one of the Boogie MK ll two stage distortion circuits. There is a spare section of tube to play with.
I do remember adding a 10-20pF cap across the 3MEG gain pot to up the treble at min drive, but little else.
I also used the Boogie schem to mod old Twin Reverbs where I removed the trem circuit and replaced it with the distortion stage and used an AB box to switch channels. Crude by todays standards but if my memory seves me right it sounded good..........a poor mans Boogie.
Cheers,
John G

bajaman · Post by **bajaman** » 28 Jul 2008, 11:58

Never understood the hype surrounding Rivera designed fender amps - why use a resistor when a vacuum tube two capacitors an inductor and 4 resistors can do the job just as well

bajaman

The Fender 75 was the ultimate worst sounding amp of that period too

Fuzzer · Post by **Fuzzer** » 28 Jul 2008, 15:52

Yikes, I guess I really have shit-ears, bajaman.

Or maybe the amp I heard was blessed in some way

. Let's hope for that.

premiumplus · Post by **premiumplus** » 28 Jul 2008, 23:04

Yeah, I never have been that enamoured with any of his stuff. I mostly bought this because of the sweet EVM12L inside it. I swapped it with a Weber 150 something or other (never that hot on Weber stuff either...) and I guess I'll put it up on auction. I saw one go for $800 recently! But it had a JBL in it.
Thanks guys, I kind of thought a rebuild would be like polishing a turd

soulsonic · Post by **soulsonic** » 29 Jul 2008, 03:48

Personally, I would strip it bare and rebuild it as something else. That circuit has alot of "resources" you could redistribute. You could probably build a really cool amp from all the stripped parts without having to purchase hardly anything additional.
BTW, I've seen that parallel input stage before... on the Knucklehead.

premiumplus · Post by **premiumplus** » 29 Jul 2008, 14:52

You know, soulsonic, you've got a great point. That thing has a lot of nice caps and pots, transformers, choke etc...I'm going to have to sleep on that. I do love 1X12 combos and it is a nice heavy chassis. And since I got laid off I've got a little time on my hands between interviews. How are the transformers in that thing? Are they good Iron?
The Knucklehead uses that parallel input stage? I've never played or heard one that I know of anyway. Why use a tube like that? It's not for driving a heavy load, is it? I could see driving a transformer or the like with that type of configuration but I'm really honestly confused as to why Rivera did that in the Concert. But like bajaman said a few posts up, Rivera has done different things with circuits before. I'd just like to know what the parallelling of stages accomplishes in the Concert.