’65 Re-Issue Question

John Bechtel · Post by **John Bechtel** » 27 May 2006 8:29 pm

OK, let's say I turn ‘OFF’ the Reverb and Vibrato Effects and only want to use the EQ along with my External BOSS RV-3 for my Effects. Can anyone tell me if there is any difference between the Input/EQ/Output of either of the (2) channels of my Twin Custom™ 15”? Will I get the same results from either channel, or would one be more efficient than the other? I could just read the manual, but; with my limited amount of electronic's understanding, I probably still wouldn't know any more than I do now¡ This inquiring~mind would really like to know and in layman's terms if possible! Thanks a Bunch! Even if I get no Reply, I'll try it anyway, but; I'm speaking “from a technical standpoint”!
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“Big John”
a.k.a. {Keoni Nui}
Current Equipment
[This message was edited by John Bechtel on 27 May 2006 at 09:31 PM.]

John Bechtel · Post by **John Bechtel** » 27 May 2006 9:23 pm

I just read up on the manual for my Amp. and if I understand it correctly, both channels have the same Middle & Bass response to the EQ, but; the Treble Response is more noticeable in the Vibrato~Channel. So, in other words if I use the Normal~Channel; I'm going to have to turn the Treble Knob higher to get the same overall~sound. So, actually both channels ‘can’ produce the same sound, when setting Middle & Bass the same, with a higher setting on the Treble of the Normal~Channel! Is this the correct understanding? I'm as dumb as I thought I was!

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“Big John”
a.k.a. {Keoni Nui}
Current Equipment

Donny Hinson · Post by **Donny Hinson** » 28 May 2006 5:17 am

I think that's about it, John. Also, I've noticed that the reverb channel is a little louder than the "normal" one.

John Bechtel · Post by **John Bechtel** » 28 May 2006 9:24 pm

The loudness might be the effect of the brighter Highs in the Vibrato/Reverb Channel! (???)

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“Big John”
a.k.a. {Keoni Nui}
Current Equipment

Jerry Erickson · Post by **Jerry Erickson** » 29 May 2006 4:50 am

The vibrato channel is louder because it has an extra gain stage. When you're looking at the back of the amp and counting from right to left, tube 4 is used for reverb recovery and as a gain stage for the reverb/vibrato channel.

John Groover McDuffie · Post by **John Groover McDuffie** » 29 May 2006 10:05 am

I am most familiar with the original BF & SF amps. In those (and I imagine this feature might have been re-created in the re-issue) the vibrato channel has a treble bleed, or "bright" cap wired across the volume pot, like having the bright switch permanently on, although a smaller cap value than that used for the bright SWITCH in larger Fender amps, so the effect is more subtle. The normal channel doesn't have this cap. It is also true that the reverb channel has more gain due to the stage where the reverb return gets mixed back in.

As far as getting the same sound from the normal channel by turning up the highs more, I don't think that is quite true. The high end which the "bright" cap produces sounds different that the high end resulting from turning the treble control up. This is because the respective circuits use different cap values, are in different points in the signal flow, etc.

I have sometimes plugged into the normal channel when recording to get the sound of the amp without the bright "switch" circuit. By the way the bright cap is most effective at the lowest volume settings, and gets proportionally less as the volume is turned up, because of how it is wired to the vol pot.

Hope this helps.
[This message was edited by John Groover McDuffie on 29 May 2006 at 11:14 AM.][This message was edited by John Groover McDuffie on 29 May 2006 at 11:16 AM.]

Mike Fried · Post by **Mike Fried** » 29 May 2006 4:20 pm

What you say is true, John (hi, BTW...). I would characterize the Deluxe's 47pf "bright" cap as more like a "presence" effect, as it works on a higher frequency than the "treble" control circuit. They are both shelving-type EQ's and interact to some degree, but the "treble" circuit shelf starts in the high-midrange area and the "bright" cap start to work much higher. It is actually a high-frequency bypass cap that works with the resistance of the volume pot, which is why its effect is more pronounced at lower volume settings (higher resistance in the pot=more signal thru the cap in proportion). It's the same type of circuit used on a guitar's volume pot when it has a small cap or cap/resistor combination across it.[This message was edited by Mike Fried on 29 May 2006 at 05:28 PM.]