Jump to content

Super Twin Reverb mod - w/clips


wagdog
 Share

Recommended Posts

  • Members

Most of the "web" knowledge says that you can't "blackface" a later 70's fender amp.

 

It's probably true, but I think I came pretty close to nailing a decent twin sound with my super twin reverb.

 

I pretty much tore out the entire pre-amp, all the way up to the phase inverter of the amp, and rebuilt it to a AB763 preamp spec (found in older twin reverbs and deluxe reverbs (minus the mid control).

 

I had come to the conclusion that all the super twin "stuff" such as a presence control and 5-band EQ, was neat, but I couldn't dial in the tone I wanted. It was always really middy and punchy, but not well defined. The low end was flat as well. The distortion control was not so neat, so I took that out a while ago and used the switch to lift the NFB loop if desired. I think all the extra stuff was masking the twin reverb part of the amp.

 

The PI is a bit different on the super twin in that it has a cathode follower buffer after the PI and before the power amp, but the pre-amp, in my opinion is the real problem. Also, the reverb in the super twin reverb is driven by a single pentode rather then two triodes of a 12AT7 in the twin, but I think the reverb sounds really nice now that it's wired in correctly.

 

Also, ultra-linear twins are not that well thought of either, and the super twin has that as well. It turns out though that the ultra-linear sounds nice and smooth, once the preamp situation is sorted out.

 

With the new preamp, and correctly wired reverb, the amp has that great, round fender low end, and it sounds really balanced from the low end to the top end. It also sounds MUCH better at lower volumes then it did in the past (that or I'm going deaf from playing a super twin reverb, which is possible).

 

Here are a bunch of short clips of the new SUPER twin amp (it does have 180w and 6x6L6's after all!). I made them with my '74 strat w/bg-pups.com v60's in it. The last one is w/my srv sig strat.

 

http://wagner-usa.net/tunez/wag_track1_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track2_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track3_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track4_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track5_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track6_mixdown01.mp3

http://wagner-usa.net/tunez/wag_srv_mixdown01.mp3

 

A word of warning: if you're considering modding your amp, don't do it if you don't REALLY know what you're doing. There are stored voltages present in your amp, even after it's been turned off, unplugged and sat for a while. These voltages can SHOCK and possibly KILL you. Find a reputable technician and have them work on your amp.

Link to comment
Share on other sites

  • Members

If you haven't removed the negative feedback loo yet, do that.

 

The big complaints about the UL Fender's being sterile all stem from that. The UL output transformer has negative feedback built in, but the Fender engineers ignored every tube manual out there, which all say don't use a NFB loop with UL transformers, and used it anyway. Removing that loop makes a huge move to warmth and more 3D like clean tones.

 

Dr.Z uses UL OT's successfully in the Route 66 and others.

Link to comment
Share on other sites

  • Members

If you haven't removed the negative feedback loo yet, do that.


The big complaints about the UL Fender's being sterile all stem from that.

 

When I removed the distortion control (and parts), it left a switch and 100k pot free. I wired the switch up to lift the NFB loop. When I get some time next weekend I'm going to set it up so when it's switched on, the 100k pot will go in series front of the 820ohm resistor in the NFB. I'll probably put a 3.3K resistor across the pot so it'll go from the stock 820 to about 4K in the NFB loop.

 

It does sound nice without the NFB loop, but I like having the versatility as well.

Link to comment
Share on other sites

  • Members

Track 3 sounds really sweet. You should have done the before tracks so we could compare them.

 

Good point! Luckily I did post some clips a while ago...

 

This is when I first got it back in august ('74 strat):

 

http://wagner-usa.net/tunez/str_74strat_wagdog_mixdown01.mp3

 

and this is after recapping the power supply (srv):

 

http://wagner-usa.net/tunez/str_srvstrat_neckmid_wagdog.mp3

 

funny, I'm playing a lot of the same stuff on those clips! (not funny actually)

 

Listening to those clips, it still sounds pretty good - however you can kind of hear the undefined bass that was bothering me. Also, the amp feels much more responsive now, like the notes just jump out of the speaker...

 

especially after lifting that NFB as Wyatt was talking about - just played it like that, and it does have a rounder sound.

 

Another trait it had prior to modding was it was really peaky, especially in the mids.

 

FWIW, I learned a ton by doing this mod. The normal preamp channel on a twin reverb (and deluxe reverb) is exactly 1x 12ax7! 1 triode before the tone stack and volume, and 1 triode after it, into the phase inverter and out to the power amp. That's it - super simple, and they sound sooooo good! The vibrato channel (what I built in my amp) is 1 and a half 12ax7's. The twins reverb takes 1 and a half 12ax7's and the vibrato adds another 12ax7. I didn't build a vibrato circuit (have no need for it) and just modded the existing reverb circuit to quasi blackface specs (used the existing pentode driver instead of a complete 12at7).

 

So simplicity really does make for a better sounding amp, imo.

Link to comment
Share on other sites

  • Members

BTW; can someone who knows answer a question I have about the CF after the PI;

 

What are the sonic benefits/drawbacks of the CF, and what would be the result of removing it and converting the PI to a blackface fender PI? And why is there a CF in this amp anyway? Is it to support the fact that there are 6 power amp tubes rather then 4?

Link to comment
Share on other sites

  • 10 years later...
  • Members
On 11/1/2010 at 7:18 PM, wagdog said:

Most of the "web" knowledge says that you can't "blackface" a later 70's fender amp.

 

It's probably true, but I think I came pretty close to nailing a decent twin sound with my super twin reverb.

 

I pretty much tore out the entire pre-amp, all the way up to the phase inverter of the amp, and rebuilt it to a AB763 preamp spec (found in older twin reverbs and deluxe reverbs (minus the mid control).

 

I had come to the conclusion that all the super twin "stuff" such as a presence control and 5-band EQ, was neat, but I couldn't dial in the tone I wanted. It was always really middy and punchy, but not well defined. The low end was flat as well. The distortion control was not so neat, so I took that out a while ago and used the switch to lift the NFB loop if desired. I think all the extra stuff was masking the twin reverb part of the amp.

 

The PI is a bit different on the super twin in that it has a cathode follower buffer after the PI and before the power amp, but the pre-amp, in my opinion is the real problem. Also, the reverb in the super twin reverb is driven by a single pentode rather then two triodes of a 12AT7 in the twin, but I think the reverb sounds really nice now that it's wired in correctly.

 

Also, ultra-linear twins are not that well thought of either, and the super twin has that as well. It turns out though that the ultra-linear sounds nice and smooth, once the preamp situation is sorted out.

 

With the new preamp, and correctly wired reverb, the amp has that great, round fender low end, and it sounds really balanced from the low end to the top end. It also sounds MUCH better at lower volumes then it did in the past (that or I'm going deaf from playing a super twin reverb, which is possible).

 

Here are a bunch of short clips of the new SUPER twin amp (it does have 180w and 6x6L6's after all!). I made them with my '74 strat w/bg-pups.com v60's in it. The last one is w/my srv sig strat.

 

http://wagner-usa.net/tunez/wag_track1_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track2_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track3_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track4_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track5_mixdown01.mp3

http://wagner-usa.net/tunez/wag_track6_mixdown01.mp3

http://wagner-usa.net/tunez/wag_srv_mixdown01.mp3

 

A word of warning: if you're considering modding your amp, don't do it if you don't REALLY know what you're doing. There are stored voltages present in your amp, even after it's been turned off, unplugged and sat for a while. These voltages can SHOCK and possibly KILL you. Find a reputable technician and have them work on your amp.

Hi there! Tell me more about these mods, i would like to modify my Super Twin as well...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...