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Post subject: 1995 Blues Deville 4x10 Reverb
Posted: Thu Sep 20, 2018 8:54 am
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Hi,

Any known / tested way to upgrade the Reverb ?
I like this Amp sound very much, but find the Reverb very weak..
Injected 4mVAC via the input jack and traced the signal with a osciloscope. The signal is present, but to weak -
OP Amp input AC voltage to low. Checked Resistors and Capacitors, the tank, wiring etc. Looks Fine.

Any Help will be much appreciated!

Thanks!


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Post subject: Re: 1995 Blues Deville 4x10 Reverb
Posted: Wed Sep 26, 2018 1:42 am
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http://www.guitarampboard.com/forum/vie ... =5&t=43302

Wait for TimAudio, he his the master here.

Did you look at this ?
http://billmaudio.com/wp/?page_id=46


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Post subject: Re: 1995 Blues Deville 4x10 Reverb
Posted: Wed Sep 26, 2018 9:07 am
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Unusually, the voltages on this amp are measured with a dvm in the Drive channel.
Controls at 50%, reverb 0, Bright sw off. The input to the reverb should be close, but the output depends on pan effeciency.

There are improvements easily accomplished.
First, glue the tank coils to the laminations to prevent the coils from vibrating.
Next, replace U2 with a high slew rate version. TLE2072 or OPA2134. This improves articulation. Do U1 as well if you use the effects loops. Buy sockets with nice round pins and get a couple extra.

If you compare the circuit of the original to the reissue, U2b has larger value capacitors that will pass more mid and bass.
C21 output coupling cap is changed from .015 to .47uf.
C50 bright bypass cap .0015 to .0068
C20 hi frequency rolloff cap 560pf to 47pf.
C18 input coupling 330pf to direct connection.

C19 also limits bass rolloff frequency. Raising it adds bass.

Each of these cap changes will affect tone.
For experimentation with different values, take those extra dip sockets and cut the pins away. Now solder the pins where you want to mod the cap values. Get them tight against the board so when you push in a lead, it doesn't bugger the solder pad on the backside.
Keep the capacitor leads short. You can solder the pin when you arrive at a final value.
Let us know how it works out.


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Post subject: Re: 1995 Blues Deville 4x10 Reverb
Posted: Wed Sep 26, 2018 12:40 pm
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Looks like the preamp signal into the reverb passes through connection J3 "pwr amp in", so maybe exercise those connections. At that point another path to ground could be leakage thru JFET Q1, some diodes there too. It's something to check. There is also JFET Q2. Don't forget to ck the op-amp pwr supplies, +/- 16V.

https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Blues-Deville-Schematic.pdf


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Post subject: Re: 1995 Blues Deville 4x10 Reverb
Posted: Thu Sep 27, 2018 2:46 pm
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If it is discovered that there are no physical issues, there may be another option.
I believe the Blues Devilles from the 90s came with the 4BB3C1B tank which is a 17" two spring tank.
I would imagine you can get a more lush reverb with a 8BB3C1B which is a three spring tank.
Or if you want to go for more there is the 9BB3C1B which is a six spring tank.
The input and output impedances are slightly higher than stock but they should still work.
I have done this mod myself on a Blues Series amp; installed a six spring tank.
The difference was remarkable.
It may work on the Deville as well.

Your thoughts, Tim?

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Post subject: Re: 1995 Blues Deville 4x10 Reverb
Posted: Fri Sep 28, 2018 8:45 am
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Well, I think the OP issue of low reverb signal can be traced to note 3 on the schematic. Its note 4 on the other Deluxes. Basically, it says to measure voltages in the Drive channel. Since these are single channel switching amps, measuring in the Drive channel will get a complete test of both channels.

Each spring is a different length and thickness, with its own delay characteristic . It adds another complete audio signal per spring. More springs causes more interaction between the delayed signals in the return coils to give that lush sound. Its good if the complexified signal can be handled well by the electronics.
A tube reverb system has a high enough slew rate to accomodate the more complex signal coming from multiple springs. A SS system such as the BDX needs the improvement in the op amp to handle the signal well.
I like the long tanks, but the best sounding tank ive heard for vocals is from old Peavey mixers. It has two springs in series with a straight metal bar to connect the springs. So instead of adding parallel signals, it is a single signal coming out of the tank. The clarity of the reverb is very clean and sonically simple


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