I have written many posts about mods I have made to my BDRI. These mods have ranged from the simple, such as tube and speaker changes, to the more complex, such as circuit modifications. These posts have been scattered around in various topics in the forum, in some cases in multiple threads. I thought I would take some time and create one single thread detailing the what, why, how, and results of the changes I have made. The changes that I have made were not the result of a general dissatisfaction with the amp, but were out of a desire to learn more about tube amps (it was my first tube amp) and how they worked.

Instead of just writing one giant post covering everything, I'm going to treat each mod to its own post in this thread. That way it will be easier to keep track of things and hopefully make any questions on each mod easier to address. I'll probably post one mod each day, but anytime anyone has a question, feel free to ask. I hope others will find this thread interesting and maybe learn something from it.

Before I forget, I should point out that most of these mods, with a few tweaks, are applicable to the Blues Deville Reissue and to some extent the original Blues Deluxes and Devilles.

Stay tuned for more.

Disclaimer: I take no responsibility for damage to your amp due to failure to follow the mod instructions as presented here. Also, it is your responsibility to verify the circuit connections in your amp before and after making the mod. If you find an error in anything I posted, please bring it to my attention before you proceed with any mod. If you are not comfortable working on a tube amp, do not attempt these mods. Finally, most of these mods will void your warranty. Do not do them if that is of concern to you. Bottomline: You break it, you bought it.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

Bluesky, cool... look forward to future posts.

And so am I!

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The quintessential sound of 60/70's R&R:
Fender Tube Amps
Gibson Guitars

Ok. Let's kick this thing off with a little introduction of how I came about owning a BDRI.

Like I said in the first post, this was my first tube amp. When I graduated from college in 1976 with a BSEE, vacuum tubes were a dying breed, discrete transistors were already well established, and integrated circuits were the next big thing. But vacuum tubes were still being taught, so I at least gained a fundamental knowledge of tubes.

Fast forward to April 2010, when I announced to my wife that I wanted to buy an electric guitar after a 25+ year break in playing (from the late 60's to mid 80's). She sighed and said "Ok, as long as you promise not to sing". So I bought a Fender Strat and, naturally, a solid state amp, specifically a Frontman 25R. I mean, who used tubes anymore?

After a few months, I saw the Fender Blues Deluxe Reissue on sale at my local Guitar Center. It was love at first sight. It was also $750 (but on sale for July 4th for $700). What to do? I found my wife at the local furniture store ogling the ugliest chair I had ever seen. She was likewise in love. So a deal was struck. We each went home with our latest "must have" item (well, hers was delivered a few weeks later).

So I had my first tube amp, and I was in love. I didn't even know about Tweed amps at the time (every rock star wannabe played Blackface Twin Reverbs in my dorm, or so it seemed by the volume of sound on Saturday night). But this was the coolest amp I had ever seen so I started doing some research and dusting off the dark recesses of my brain to dig up long buried memories of these glass bottles known as "tubes". The more I read and learned, as well as reading about the adventures of other BDRI owners, the more I wanted to try different tubes. So the first mod I made to my BDRI was a new set of tubes.

Coming up next, "Bill's Adventures In Tube Land".

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

Thanks for posting these little adventures Bill, I'm tuned in for future episodes.

Cheers.

Snowy

Some of them would make a good TV comedy series. At least better than a lot of what is on today.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

i look forward to reading your stories. also i wanted to say that i love my bdri as well. i have changed speakers and tubes of all varieties, power and preamp. the bias has been up and down, but right now after i sat down the other day and did the bias calculations and properly adjusted it. it now sounds the best it has ever sounded in 4 yrs. also i wanted to note that it has it's original gt 6l6-r (5881wxt) and biased at 87.3mV witch gave me 413 on the plates and that is a nice comfortable 18 watts and that is 60%. i wanted to go to 70% but the tubes have a good bit of use so i went with the side of caution. but so far so good and i feel that it will be good to go for a while. thanks for your past threads about biasing.

OK. As I promised last night, here is my adventure swapping tubes around in my BDRI. Note that I am not going to recommend specific tube brands, just identify what I have been using. Tube brands are a very personal thing and everyone has their favorites. I like JJ tubes and use them in all three of my tube amps, but we're primarily going to talk about tube types. If you want more information about JJ tubes for the BDRI, check out

https://www.eurotubes.com/cart/index.ph ... ory_id=122

My BDRI came equipped with Groove Tubes in the following configuration:

V1 = 12AX7
V2 = 12AX7
V3 = 12AX7 (Balanced for PI use)
V4/V5 = 6L6R (Actually SOVTEK 5881WXTs).

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).

The first thing I did was learn about biasing the amp. After doing some research, I learned that Fender has a tendency to bias their amps pretty cold, primarily to extend tube life. The Fender spec for the BDRI is 60 mV at the bias test point with a plate voltage of about 430 VDC. I learned that this equates to an idle power of about 12 watts. I have read, but not confirmed that the stock power tubes are only rated at 25 watts. This would translate to a bias setting of about 48% max plate dissipation. Way cold! If the stock tubes were 30 watts, they would be even colder at that setting. Anyway, I tried increasing the bias voltage at the test point to 70, then 75, and finally 80 mV. The amp probably sounded best at about 75 mV. What I didn't realize at the time was that you also have to measure the plate voltage as it will decrease as the bias is increased and vice versa. Oh, well. Nothing blew up. Yet.

Still not happy, I decided to change tubes.

My first crack at different tubes was the JJ "Blues Option" from Eurotubes. That set consists of:

V1 = 12AX7
V2 = 12AT7
V3 = 12AX7 (Balanced for PI use)
V4/V5 = 6L6GC.

12AT7? Now I had to learn more about different "gain factors" for preamp tubes. Turns out a 12AX7 has a gain factor of "100" and a 12AT7 has a gain factor of "60". Here's a good explanation of gain factor:

http://thetubestore.com/gainfactor.html

So, what this all means is that the amp now has a little less gain from input to output. It will still play plenty loud, you just have to turn it up more or hit it with a bigger input. How did it sound? Pretty good. I also learned that the JJ 6L6GCs could be biased hotter for a thicker, more driven tone. By this time I learned that you had to measure plate voltage too. So, I set out to increase my bias when things blew up.

Well, they didn't really "blow up", but there were a lot of sparks and a small fire.

While I was measureing the plate voltage with my DVM on pin 3 of V5, the probe slipped and momentarily connected pins 3 and 2 (the heater). There was a big spark and a tiny fire on the PCB. Naturally I jumped back, pulled the probe out, blew out the fire, and turned off the power. There was a small charred area on the PCB between the two pins. How do I clean that up? Well, I took my electric toothbrush, and old brush attachment dipped in alcohol, and scrubbed the charred spot. It actually cleaned up quite nicely. There is a small depression where the fire burned the PCB, but very little residue. Amazingly, there was no damage and everything worked afterwards. I never told my wife what happened.

Following that episode, I invested in a bias probe:

http://www.amp-head.com/product_info.ph ... ucts_id=70

Now I could safely bias the amp to my heart's content.

The amp was sounding pretty good, but there was one issue I had that I had been reading about others complaining about. That was the fact that volume on the clean channel jumps significantly between "1" and "3". The common fix is to suggest replacing the volume control with an audio taper pot. That is wrong, by the way, as the clean volume control is already an audio taper pot. My research led me to believe that the problem was too much gain in the preamp stage. What to do? Swap the 12AT7 from V2 with the 12AX7 in V1. So now my tube configuration was:

V1 = 12AT7
V2 = 12AX7
V3 = 12AX7 (Balanced for PI use)
V4/V5 = 6L6GC.

Hey. That works! The volume didn't jump as much and you had to turn the clean volume up a little higher to get things loud like before. But it didn't sound good. With the original configuration, the clean channel was a little thicker sounding. This setup sounded too thin, almost as bad as the original tube set did. So I changed things back to the origninal JJ setup and searched some more.

I then discovered NOS tubes and the 5751.

I buy all of my NOS tubes from here:

https://www.kcanostubes.com/

The owner, Mike K is a nice guy (I got to meet him) and lives only about 20 minutes from me.

Anyway, after reading about SRV and others using a 5751 in V1 to bring the gain down a little I bought a couple. The 5751 has a gain factor of about "70" a little more than the 12AT7 but still less than the 12AX7. And the sound? Fantastic. Warm and thicker with no harshness. But the amp was still a little too loud for home, so I decided to try a balanced 12AT7 in the PI like Fender uses in some of their other amps. So this configuration was:

V1 = 5751
V2 = 12AX7
V3 = 12AT7 (Balanced for PI use)
V4/V5 = 6L6GC.

The 12AT7 in the PI position seemed to tighten up the bass a bit. Volume was now at a more resonable level for home use (but still capable of being quite loud), and the clean channel voume control was, well, more controllable. The amp sounded great.

But could it sound better?

By this time I had learned about the real "tweed" amps from the 50's. Hey, the BDRI looks like a tweed amp. Can it be made to sound like one? Well, no. But I did learn that several tweed amps used a 12AY7 (gain factor of about 40 - 45) in V1. Why not. First I tried a EH 12AY7. I was not impressed. Then I said to myself "The 5751 is an NOS JAN tube. Maybe an NOS JAN 12AY7 would sound better". So, back to Mike K I went for some NOS JAN 12AY7s. Now my amp looked like this:

V1 = 12AY7
V2 = 12AX7
V3 = 12AX7
V4/V5 = 6L6GC

I have found sonic heaven.

Well, that's a little bit of an exageration, but the amp did sound darn good. Oh, I briefly tried a 12AT7 in V3 but that made the amp too quiet for me. Overall loudness is about the same as the previous configuration but the clean volume had an even better sweep than the 5751 provided. So, that is my final tube configuration. Does it sound better then the 5751/12AX7/12AT7 combination? Its a bit of a toss up. Both are very smooth and thick sounding. Very nice cleans and capable of a nice "Bluesy" tone. I think it would boil down to personal taste, but you can't go wrong with either combination in this amp.

A couple of things to note. Most of what I have talked about was the effect on the clean channel. Using lower gain tubes in V1 or V2 will reduce the amount of gain available from the drive channel. You can still get a bit of drive, but you have to turn the drive volume up higher. Some may like it, or not. Another personal taste thing. I don't use the drive channel myself as mentioned previously. Also during this time I was experimenting with biasing the power tubes. That will be a separate subject, because I discovered some very unusual things about the bias circuit in my amp.

Tomorrow night: "Speak up. I can't hear you". Yes, we'll talk about speakers for the BDRI.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

You're welcome.

Stick around, because my bias story has some interesting twists and turns.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

This is awesome! I've had my BDRI for about 1 year now and learned so much about it from you and several others. Thanks, Bill! Is your speaker change out going to have pics? That is one of my future mods (along with new JJ power tubes) and pics would be great!

This post should get pinned!

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2000 American Deluxe Stratocaster
2011 Gibson Les Paul Traditional Pro 50's
2007 Epiphone Les Paul Custom
JH-1B Jimi Hendrix Crybaby
Visual Sound Jekyll & Hyde V1 Grey Box
Korg Pitchblack
Boss TR-2 & PH-2
Blues Deluxe Reissue
Peavey Ultra 60 410

Are the stock speakers Eminence legends? I just bought a new BDRI im running a Bogner xtc red pedal in the clean channel, I would prb like it for less break up. Re did the preamp tubes, going to use the drive channel for my mid gain crunch. You guys prb arent into the higher gain stuff but here a quick sample the bass is a little heavy though. I thought it came out pretty good. I have a couple years of playing not 20! lol
http://www.youtube.com/watch?v=d7adbEAgL6w

I do have a eminence green back type speaker i wonder if that would sound good in these amps? have to take the chassis out? thx!

Thanks.

Sorry. No photos, but a swap is very easy.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

Yes, it is my understanding that the stock speakers are Legends.

I'll talk about a tone stack mod to reduce bass heaviness in a later installment.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio

It is easier if you remove the chassis. I'll talk about what to look for in a speaker later tonight.

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Bill

Jimi Hendrix, Eric Clapton, BB King: The Ultimate Guitar Trio