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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 11:27 am
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TimsAudio wrote:
I , the two things I wonder about is what value do you have for the feedback resistor and what brand output transformer do you have?



" The OT is Classic Tone's "beefier upgrade" with multi taps for 4, 8 and 16 ohms. I used the green which is for an 8 ohm load. "

-upnorth2


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 12:09 pm
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Thanks Strat, that slipped past me. The choice of secondary tap for the FB makes a big difference in output stage gain.
The 4 ohm tap or a larger value FB resistor can pump up the resopnse.
With all controls centered, reverb and Trem Off, an AB763 Normal channel puts out 2 Volts RMS at 4 Khz.into 8 ohms. Other frequencies vary, but most of them are consistent at this frequency. You need a scope or true RMS meter and dummy loads.
If the multitap transformer is the same physical size as the original, the primary windings are probably higher resistance than stock OTs. This reduces max power output. Compare the published specs and measure yours..


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 12:22 pm
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TimAudio, you impress me.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 2:15 pm
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The NFB resistor is an 820 ohm. Here's a pic of the 1 meg resistors. You can also see that I used heater wire and grounded the cathodes in the preamp section to the middle of the chassis at the big washer, I have a big soldering iron I use just for chassis grounding/mounting but this chassis is stainless. Disregard the reflection that looks like more wires in the background. I've thought about my choice of OT and probably should have gone with the standard 8 ohm OT.

As far as a kit stratele, not. It would have been much easier. I sourced every part myself and built the cab from scratch. The chassis only came from Weber as a 5A40 in their bargain center and needed some mods to get it to work for this. I usually steer clear of Mojotone but Tube Depot must get their pots (advertised as regular CTS) from them anyway, or maybe even owned by them. AES, Mouser, Hoffman, etc. usually.

UN

Image

Image

Image


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 2:45 pm
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Thanks, upnorth2, I had forgotten that Weber sold a "5" style chassis for their "6" style builds. Looks good!
On my DR build, I too used a multitap OT and I used a switching jack in the aux position. Nothing plugged in is 8 ohm, plug into aux, and it switches to 4 ohm. (I kept the standard shorting jack in the main position).


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 3:38 pm
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upnorth2,

You are a great cabinet builder and do a great job with covering !

Congrat


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 4:58 pm
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Indeed, your woodworking and covering skills are top-shelf!

Arjay

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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 15, 2017 12:48 pm
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The reverb is pretty strong on this amp, surf territory at 4 even with a 12AU7. The Fender AB763 schematic and layout show two different reverb mix resistors, 3.3m on the schematic and 4.7m on the layout. Don't know why that is. I have a 4.7m in it now and if I understand this correctly should actually be taming the reverb more than a 3.3m would. I also wonder if my higher voltages have anything to do with it.

UN


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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 15, 2017 1:04 pm
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upnorth2 wrote:

The reverb is pretty strong on this amp, I also wonder if my higher voltages have anything to do with it.

UN



Probably.
Higher value of cathode resistors on reverb tubes may help IMO


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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 15, 2017 8:08 pm
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The reverb dropping resistor is a real choke point in the signal path. It pushes fine harmonic detail into the noise floor and disappears
The reverb balance is your choice. If you use less reverb, try a 2.2Meg The 3.3 meg is the usual vakue installed, but Fenders usually have more reverb than most pickers use. I haven't seen the 4.7M used.
Dropping the value should make a significant increase in Vibrato channel volume. At low to mid frequencies, they should be about the same, channel to channel.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 20, 2017 1:43 pm
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Might that mod also work on some of the modern Fender platforms? I'm thinking specifically of the Supersonic line.

:idea:

Arjay

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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 22, 2017 8:21 am
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Well that was the wrong post. Lets try again
The Supersonic 60 uses a 3.3M at R75.
Tacking another 3.3M on it in parallel will drop it to 1.65M.
That should give it a boost. A temporary 3 meg pot can dial in the desired amount.


Last edited by TimsAudio on Sat Apr 22, 2017 6:24 pm, edited 1 time in total.

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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 22, 2017 6:15 pm
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TimsAudio wrote:
If you use less reverb, try a 2.2Meg The 3.3 meg is the usual vakue installed, but Fenders usually have more reverb than most pickers use.


If I went down to a 2.2 meg do you think I need to change the value of the 10pf cap as well? I did try a 100K audio pot instead of the linear and it slowed the onset of the reverb some.

UN


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Post subject: Re: Deluxe Reverb Build Help
Posted: Sat Apr 22, 2017 6:28 pm
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The 10pF gives the dry treble a bit more sparkle. I would leave it unless its ice-pick bright after you put in the 2.2M.


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