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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 07, 2012 12:15 am
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Sorry for the delay. Time to wrap up this saga with a few mods that I have considered but have not decided to do yet.

CAUTION!!! Tube amps contain high voltages that can be lethal. Be sure to check the power supply caps with your DVM prior to working on your amp and drain the caps if necessary. Make sure your amp is unplugged and never stick both hands inside a live amp.

This first mod I'm going to credit to shimmilou as I believe he has done it to his Hot Rod Deluxe.

As I noted earlier in this thread, my BDRI has always exhibited low B+ voltage that drops significantly the hotter the power tubes are biased. I could never find a reason for this after all the tests I ran and have just decided "it is what it is". Shimmilou has mentioned in the past about how he has increased the power supply filter capacitance for the B+ supply by adding another filter cap in parallel with the 47 mF cap. There is room on the board to easily do this as shown in the layout:

Image

Neither C32 nor C34 are populated in the BDRI. It would be simple to add another cap, say 22 mF, next to C31. Stick it to the PCB with hot glue or silicone sealant (get the kind without acetic acid) and solder the new cap's leads over to C31. As I have not done this mod, I cannot say how it changes the amp's sound and performance beyond saying the the B+ supply will have a little less ripple and may be steadier than without the added cap. Perhaps shimmilou can comment on this mod.

While we are on the power supply, one difference between the performance and sound of the 5F6A clone and the BDRI that I didn't mention is that with a solid state rectifier, the BDRI exhibits no significant sag in the power supply that I can hear. The 5AR4/GZ34 does not have a lot of sag, but there is some as the volume on the 5F6A clone is cranked. To add some sag to the BDRI, a "sag resistor" can be added in the power supply. Here is a great writeup on how to add a sag resistor and its effect on a Hot Rid Deluxe:

http://www.justinholton.com/hotrod/sag.html

I might try this one in the future.

The next mod that I have thought about involves the effects loop. I don't use the effects loop and have always wondered if leaving it in place is loading down the output of V2A. The mod is a simple one in that you just have to lift one end of R28 (or remove it entirely).

Image

Image

Disconnecting R28 will remove the preamp out section of the effects loop. The power amp in section is not connected unless a plug is inserted into the jack.

The next mod involves modifying the master volume control to work with the clean volume control as well as the drive volume control. This mod would be useful is you are using a 12AX7 in V1 and need a little more control over the volume level. With a 12AY7 or even a 5751 in V1, the lower gain of those two tubes allows finer control over clean volume as discussed earlier in the tube selection part of this thread. Also, use of lower gain tubes in V1 minimizes the gain and overdrive of the preamp.

The first thing that would need to be done is to disconnect R18:

Image

Image

Next, a shielded cable needs to be added between the output end of R45 and the cathode of D2:

Image

Image

Note that before doing this mod, I suggest you trace out the wiring for R45 and D2 to make sure the correct connections are made. It's hard to tell from the layout where the PCB copper traces run.

The final mod is one I found to increase the gain in the drive channel by utilizing the second half of V2. It is described in the Duncan Amp pages. This is a fairly complex mod so exercise caution if you decide to do it. Since I don't use the drive channel, I have no use for it, but thought I would throw it out there to those who like to plug their guitar straight into the amp. Also note that this mod is written for the original Blues Deluxe, not the Reissue. There are some circuit differences between the two that will need to be accounted for.

http://www.duncanamps.com/technical/bluesdeluxe.html

Well, that about wraps things up. I'm sure that there are other cool mods out there for the BDRI that people have done. Feel free to post them here. If you have any questions about anything I have said or if you have found any mistakes in what I posted, please bring them up. I hope you all have enjoyed this little adventure with the Blues Deluxe Reissue. :D

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 07, 2012 4:03 pm
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Hey there - to the OP and others who have posted here - just wanted to say a huge thanks for sharing all this info. I bought a used Blues Deluxe RI a few months back, based on the need for an amp I could fit on the back seat, channel switching option, a few nice YouTube demos, and having fallen in love with the style and size. After a few days, I began to realise I was a bit ...meh about it.
Started reading up on it a little, and although I'm not very experienced in these matters, I found a lot of useful - and accessible - info through this post from Bluesky636 , and others. Took it out for it's first gig last night, and I am finally feeling the love for this amp. FWIW, the mods I carried out;

Replaced the Groove Tubes with JJ's
Reset the Bias (ie. using the trimpot and multimeter), eventually to 72mv (I'm aware that there are other factors here, but this measure was within my abilities, and budget)
Replaced the stock speaker with a WGS G12C.

After each step, I tried it out over a couple of days, and actually undid each step, to make sure I liked what I was hearing, before re-doing. I found the rebiasing and tube swaps to have worthwhile results, but the Warehouse speaker is a real game-changer ( I may buy a couple more for my Bassman). I may get into some more detailed mods further down the line, when I have a clearer understanding of what's involved, but for now, the amp has rich, detailed tone, just enough growl (for me!), exactly the balance of warmth and sparkle that I want from a Fender amp. I'm sure if I win the lottery I could find something better, but I think this'll keep me happy for some time. Thanks to all!


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 07, 2012 4:26 pm
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Glad to hear that this thread uas been useful to you. I hoped it would be for owners of this amp. You have followed a good approach to making changes to your amp. You might want to consider getting the bias probe I recommended (or one with similar capabilities) to properly bias the amp as I described. I have found that the JJ 6L6GCs really like to run toward the hot side for best tone in this amp.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 07, 2012 7:27 pm
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Fantastic job with this thread bluesky636! :!:

As for the extra capacitance in the power supply, I have to credit Billm for that one. I did this with my HRDlx, and BJr, doubling the capacitance of the first stage of the power supply. As you mentioned, this lowers the ripple voltage, adding a few volts to the B+, and has the affect of tightening the bass response of the amp. Adding capacitance to the power supply has the opposite affect of the sag resistor mod.

I am interested in your idea about disabling the loop. One mod that I have in mind, along those lines, is to install sockets for the op amps and experiment with different types of op amps other than the TL072. One thing that I have learned is that there seems to be a significant amount of cross-talk between the halves of the loop op amp. I advised another forum member to use a dummy plug in the Power Amp In to disable the amp output while using the Preamp Out for recording. I had done this myself, but had my amp at low volume and didn't notice that the amp still produced sound, more evident when turning the amp volume up over 3. Using the dummy plug in the Power Amp In, there should be no output from the amp as the signal path to the PI is disconnected at the jack, but there was sound out. The only way that the amp would produce sound AFAIK is cross-talk through the loop op amp, so I will probably eventually install the sockets and try a few other op amps. I surmise that this same problem occurs with the reverb op amp also, affecting the reverb sound, but probably not a concern with the channel switching op amp though.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 07, 2012 10:02 pm
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Thanks, shimmilou. :D

According to page 5 of the datasheet

http://www.datasheetcatalog.org/datashe ... /tl072.pdf

there is 120 dB of crosstalk attenuation between the two outputs of the op amp.

However, looking at the layout of all the loop components, they are all clustered around the op amp. I wonder if it could be more of a case of capacitive coupling between the PCB traces?

Image

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Dec 08, 2012 5:19 pm
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I'll add another big THANK-YOU to those you've already received, Bill for a really wonderful thread! I regret not having the background knowledge to fully understand the content, but I watched every episode. :wink:

Quote:
    p1 - Intro: How Bluesky came to own a BDRI
    p2 - Tube Swapping Adventures
    p2 - Speakers in General
    p2 - Recommended Reading
    p3 - BDRI Schematic Diagram
    p3 - Reverb Circuit Mod
    p3 - Safety Lesson
    p3 - Replacing the power tube screen grid resistors.
    p3 - Modifying the BDRI's bias power supply circuit.
    p3 - Mods to the phase inverter plate resistors.
    p4 - Negative feedback from the speaker to the phase inverter.
    p5 - Removing the grid suppressor resistors from in front of the power tube grids.
    p5 - Modding the BDRI tone stack to the same configuration as that of the 5F6A Bassman
    p5 - Modded BDRI compared to 5F6A Bassman clone
    p6 - The shimmilou HRD Mod
    p6 - FX Loop Mod
    p6 - The Master Volume Control Mod
    p6 - Drive Channel Gain Mod


BTW, I got a couple of the books you recommended so hopefully one day (soon) I'll be able to revisit this thread and learn much more.

Thanks and Cheers!
BM

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Dec 08, 2012 6:57 pm
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bluesky636 wrote:
... 120 dB of crosstalk attenuation between the two outputs of the op amp.

However, looking at the layout of all the loop components, they are all clustered around the op amp. I wonder if it could be more of a case of capacitive coupling between the PCB traces?...


Maybe. It looks like the compatible op amps that I've considered so far aren't much different in that respect, and some don't give the crosstalk spec (OPA 2131, OPA 2604). I'll just have to try some and see.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Dec 08, 2012 10:03 pm
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Bluer Monkey wrote:
I'll add another big THANK-YOU to those you've already received, Bill for a really wonderful thread! I regret not having the background knowledge to fully understand the content, but I watched every episode. :wink:

Quote:
    p1 - Intro: How Bluesky came to own a BDRI
    p2 - Tube Swapping Adventures
    p2 - Speakers in General
    p2 - Recommended Reading
    p3 - BDRI Schematic Diagram
    p3 - Reverb Circuit Mod
    p3 - Safety Lesson
    p3 - Replacing the power tube screen grid resistors.
    p3 - Modifying the BDRI's bias power supply circuit.
    p3 - Mods to the phase inverter plate resistors.
    p4 - Negative feedback from the speaker to the phase inverter.
    p5 - Removing the grid suppressor resistors from in front of the power tube grids.
    p5 - Modding the BDRI tone stack to the same configuration as that of the 5F6A Bassman
    p5 - Modded BDRI compared to 5F6A Bassman clone
    p6 - The shimmilou HRD Mod
    p6 - FX Loop Mod
    p6 - The Master Volume Control Mod
    p6 - Drive Channel Gain Mod


BTW, I got a couple of the books you recommended so hopefully one day (soon) I'll be able to revisit this thread and learn much more.

Thanks and Cheers!
BM


Thanks. :D

Seems like a lot of my threads could benefit from a table of contents. :lol:

Reading books is a good thing. :wink:

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Dec 08, 2012 10:08 pm
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shimmilou wrote:
bluesky636 wrote:
... 120 dB of crosstalk attenuation between the two outputs of the op amp.

However, looking at the layout of all the loop components, they are all clustered around the op amp. I wonder if it could be more of a case of capacitive coupling between the PCB traces?...


Maybe. It looks like the compatible op amps that I've considered so far aren't much different in that respect, and some don't give the crosstalk spec (OPA 2131, OPA 2604). I'll just have to try some and see.


Should be an interesting experiment. Let us know the results.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Mon Dec 10, 2012 10:09 pm
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Here's an interesting mod that I once considered doing. I thought I had lost the link but I found it. Basically, it is a mod to replace the single 12" speaker with two 10" speakers.

http://www.markhansen.dk/Subarticles/Fe ... xemod.html

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 14, 2012 6:50 am
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First of all, bluesky636, much thanks for posting all of this! I've skimmed through a lot of it (I'm not quite as technical as you are...) and found many things of interest.

Of late I've been trying to decide on a tube amp that is relatively portable and in that process I've auditioned a stock BDRI at a local store.
Here is a YouTube vid that pretty much sounds like the one I tried:http://www.youtube.com/watch?v=uewGwH8l7kw

That is exactly what I would NOT want an amp to sound like. Every note seems very "snappy" (perhaps compressed, but not in a smooth way). Very "clanky" - way too much treble. Not what I would call "bluesy". As you mentioned:
bluesky636 wrote:
The tubes sounded OK, but a couple things I noticed were the highs were somewhat piercing and the clean sound was kind of thin and harsh. I play (or at least try to play) Blues and prefer a thicker, warmer sound. The drive channel I did not like at all (I currently use a Full Tone FD-2M through the clean channel for overdrive).

I think that what I am after is much more in line with what you want out of a BDRI.

I'm primarily a blues/hendrix/trower player and want something more "bluesy". I've tried the SS-22 and mostly liked it but found that playing relatively fast leads sounded rather blurred (notes running together without enough definition to keep them separate perhaps as a result of the frequency response curve). The BDRI has such a great vibe design-wise, but the stock sound is just unacceptable for me.

Do you have any audio samples of either your amp or perhaps a reference to a song that would give a good idea of how yours turned out?

I wouldn't try to perform your mods myself so I would need a local tech to do them.

Do you think that just swapping the speaker with the Cannibas Rex would make a significant improvement?

Again, thanks for a very informative thread!

MrM


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 14, 2012 10:26 am
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Sorry, Mr Mxyzptik, But that guy on the YT sure does yaddy-yaddy-yaddy a lot & plays very little. FWIW... Here's a YT. No Fender amp or guitars (well, Blind Owl is using a 12AX7 tube shield off a Fender amp as slide) ---BUT what a great tone outta that Goldtop and those vintage Orange amps. :) :)

http://www.youtube.com/watch?v=tu8Rx4zz-3U


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 14, 2012 12:18 pm
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Yeah, I hate that BDRI demo. The guy definitely likes to hear himself talk. :lol:

It's been a while, but I don't think my stock amp sounded that bad. Way too much reverb too. Unfortunately, I have not gotten around to making a demo with my modded BDRI. I can tell you this, I have my BDRI set up for use with humbuckers. I plug into input #2 (6 dB less sensitivity than #1) and set the clean volume on 4 or 5. Treble is set to 4, Bass set to 6, and Mid set to 8. Presence is set to 6 and Bright is on. With a bridge humbucker, the tone is bright but smooth to my ears. The neck humbucker is clear with no mud.

As said in my summary of the mods: "The speaker change is probably the most bang for your buck and easiest mod to the amp to change the overall tone of the BDRI." That is followed by the tube change. If you only do one or two mods to a BDRI, these are the meat of the mods you want to do. Speaker first, tubes second. All the other mods are gravy.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 14, 2012 5:30 pm
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Yes, admittedly that guy talks quite a lot. Sorry about that, but the sound he's getting there is very similar to the sound that I've experienced (today again, in fact) when auditioning the BDRI.

I really, really wanted to love it, but that "snappy" attack on all the single notes really bugs me. Do you know what is causing that from a technical standpoint?
I can't imagine that it's just the stock speaker but I could be wrong.

MrM


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Fri Dec 14, 2012 6:01 pm
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Mister Mxyzptlk wrote:
Yes, admittedly that guy talks quite a lot. Sorry about that, but the sound he's getting there is very similar to the sound that I've experienced (today again, in fact) when auditioning the BDRI.

I really, really wanted to love it, but that "snappy" attack on all the single notes really bugs me. Do you know what is causing that from a technical standpoint?
I can't imagine that it's just the stock speaker but I could be wrong.

MrM


Well, there are these little things on the amp called "tone controls" ... :wink:

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