My Fender Hot Rod Deluxe mods!

Hi everyone,

I've just finished some mods to my HRDlx that I want to share.

I bought my amp used almost a year ago.
- The first thing I had to change has been the speaker: the original speaker was broken (it produced a kind of distortion when playing bass notes), so I decided to go for a Celestion Vintage 30, as it is my favourite speaker and it is also stock on the limited edition version of this amp. Very helpful to smooth out the sound (I really hate shrill sounds), very useful for distorted tones.
- Next I changed the tubes, as they still were the stock ones (the amp is from 1998) and I had read about how much the sound of this amp could improve. I didn't want to spend a lot of money, I had just bought the new speaker, so I chose Electro-Harmonix for all the tubes, because I read a lot and they seemed to have the best quality/price ratio. I got a 12AT7 for V3 (the phase inverter), to tame the volume a bit. Compared to the stock tubes, the sound did improve, but it was almost a year ago, so I don't remember. Not a radical change at all, though.

Now the most recent mods.
NOTE: I didn't want to mess with taking the board out of the chassis, so I worked on the components side of the PCB. Whenever possible I soldered new components in parallel to the existing ones (for example to increase a cap value or decrease a resistor value). When not, I cut the component pretty near its body, in order to leave a long bit of the component leg to solder the new component to. This way my mods are all easily reversible.

- I did the reverb mod http://studentweb.eku.edu/justin_hol...b.html#dallman. This is a must, IMO. Now the reverb is much more usable.
- Changed C11 (390p) to 1n. Now more highs are shunt to ground at the end of the drive channel.
- Changed C1 (47u) to 22u. A bit less bass and gain are fed to the following stages.
- Added a 10n cap in parallel to C23 (1.5n). More bass to the drive channel.
- Added a 180k resistor in parallel to R9 (220k) in order to get 100k here. This way less highs are blocked at the beginning of the clean channel (note that as a collateral effect you also get more gain, as we're reducing a resistor between gain stages).
- Added a 470k resistor in parallel to R12 (130k) in order to get 100k, the standard value in Fender tone stacks. However, after checking again with the Tone Stack Calculator, I realized this mod increases bass and bass-mids (I had inverted the curves in my mind) rather than decreases them. So I might go back to 130k.
- I tried cutting R105 out, because it looks like an added component to the standard Fender tone stack, but I ended up soldering it again into place, because its role is to tame the bass a bit. I also read in another thread of this forum that it is better to keep it.
- Unfortunately, I couldn't do the middle pot mod (soldering the wiper to the bass-pot-side leg) because the big C6 cap in front of it isn't letting my soldering-pen tip go there. This is a pity, as that mod allows a better control over the overwelming bass of this amp. Edit: my recent thoughts about this mod in the following thread: http://www.thefenderforum.com/forum/...d.php?p=448875
- I added a 22u cap in parallel to C8 (1u). I did this because I noticed the More Drive setting was harsher than the normal Drive. As the More Drive differs from the normal Drive setting by two added cathode bypass caps (C8 and C9) in the last two gain stages, I thought this was the culprit, because I know that a cathode bypass cap smaller than 22u alters the frequency response of the gain stage (the smaller the cap, the more you have an increase in gain only for treble frequencies). C9 was already 22u, so no problems there.
I'm happy with this mod, now the More Drive is really an extension of the Drive setting. You also get even more maximum gain in More Drive: I like this, because it allows me to keep the drive knob lower, so I have a bigger highs-blocking effect from that pot.

Most of this mods are inspired from the Blues Deluxe schematic, but also from other Fender amp schematics. I played a Blues Deville 4x10" once at a gig and I think its clean sound was superior to the HRDlx, although it also had different speakers.
As you can see, the aim of these mods is to reduce the bass/increase the highs in the clean channel and to increase the bass/reduce the highs in the drive channel. This is to cure the harsh sounding drive channel (most of all) and the rather dark sounding clean channel. As most of the circuit is shared between the two channels, I decided to give priority to the clean channel, which is the one I use more because I mostly have pedals for my distorted tones. At the same time, I tried to give the clean channel more sparkle in order to be able to keep the treble and presence knobs lower, as this improves the drive channel tone.

I'm very happy with my mods!! The clean channel improved and, most of all, the drive channel is now more than usable. I'm looking forward to trying my amp loud at a gig to confirm the improvement.

Thanks for reading this, I hope it will be helpful to someone!

Giulio

Edit: I played the amp extensively today and I'm really stunned with the improvement in sound!! Now my strat really plays like a strat, both clean and "drived" (the stock amp didn't do its justice)!! I was about to change its neck single coil but now I'm happy again!

Dude - you may not like the sort of comments your post is likely to attract - I had a HRDv of the same age and it just fell apart - good luck to you though... :D

Hi shredgd, hi forum

I made nearly the same changes with slightly other values because I have JJ tubes and a Jensen C12N.

I only have one other mod at the R45. At the side that comes from the Master-Pot I soldered a 50k trimmer and at the other side a 100K trimmer. The ohter ends I soldered together and from that join a 22nF to Mass.

the 50k trimmer is set to 32k this means ~225 Hz low-pass and with the 100k you can tame the horrible highs. If then the normal drive (not the mor drive) is not sparkling enough add a capacitor in parallel to R24 I used 5.6nF .

So I could revers the C11 mod.

Now the drive channel has nearly the same sound as the clean channel when I turn the Guitar down. A little bit mor britisch sounding. And the more drive is fat and creamy.

Hi,

I'm glad we came up with similar solutions.
Your R45 mod is a bit unclear to me, though. Why two trimpots? You should get a high cut as well by adding only one, with the cap to ground... am I wrong?

I like the R24 mod a lot!
It solves the problem of the normal drive channel being too dark because of the high cut necessary for the more drive.
I think I will try it (as soon as I'll play the amp loud again with my mods and I'll see what is left to improve!).

By the way, the more drive sound of this amp is not defined on the bass; it is somewhat similar to a fuzz, I mean you can't do metal palm muting (even though it's got all the necessary gain!). I realize it would change the character of the clean channel as well (because of the shared circuitry), but do you know how one could (teorically) mod an amp to sound more defined on the bass?

Giulio

Hi Giulio,

I find very interesting your mods. I've got a HRDlx with a Celestion V30 too and was planning to do the unnoficial HRD web mods one by one to improve the amp sound, but i've seen yours are not the same mods. Are yours better? I see both try to brigth the clean chanel and improve the drive ones, where's the difference?

thank you!

Hi Giulio,

I take trimmpotis for canging the values on the fly. And yes it is more a High-Cut at the R45. Its a Y with the pots in the arms and the Cap in the leg. and between the "arms" is the R45. If You want to take normal resistors start with following values: for the front end 33k an for the end going to the relay/switch 68k.
In that place i soldered a "contur"-securit but it worked not so good because it was originaly from the solid state Deluxe 112. So I reduces the securit at first to two capacitors and two pots. And 3h later I had only one Capacitor and two pots. The R45 is one Resistor of a Voltage-Divider and the Highcut is more efficient behind the R45 than before. It makes a different sound than two Pots and two caps. I tried a ton of values:ride
Now the amp ist in te practice room from the band (yes the one on the photo) and is awaiting to be played. A lot of things in the Sound are better now, but I am sure it will be opened by me.

I forgotten to say I prefer a JJ ECC81 (12AT7) µ=60 for V1. Keeps away a lot of mud in the Drive section.
V2: JJ ECC83 S (12AX7)
V3: ECC81 (12AT7)
V4+5: JJ 6V6 biased at 90%, ca. 58mV

My C11 mod was 1,5nF in Series to a 250kPot(set to 120k-150k) in parallel to C11. Very like yours.

Quote:

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Originally Posted by Alcaraz

Hi Giulio,

I find very interesting your mods. I've got a HRDlx with a Celestion V30 too and was planning to do the unnoficial HRD web mods one by one to improve the amp sound, but i've seen yours are not the same mods. Are yours better? I see both try to brigth the clean chanel and improve the drive ones, where's the difference?

thank you!

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Hi Alcaraz,

some of the unnoficial HRD web mods are superb. At first the Reverb mod.
Some other mods are not so good I think the C23 mod to fatten up the drive cannel but it makes the distortion sounding bad. To much distortion in the interferences of minor chords. For that make a high cut at C11 or the other mod shown above in the postings.

Instead of a C1 mod (half the value of the cap) you can plug in a lower Gain Tube (12AT7 or ECC81) in V1.

Personaly I like to short R102 results in a high boost in normal and drive but not in more drive.

You have to try them all if You like. Tastes are different. :spin:

I never tried the C8 mod. I can read the plans and now I understand what will happen if I change a value. C8 makes a high boost above 106 Hz to bring down distortion in the interferences. For example if You bent some tone to the same on the next string. This wawawawa wa wa wa wa wa wa in tune in the Background of the tones from the two strings. To beware these wa-wa-s from distortion there was a C8.

Hi ²Thom,

I didn't mean "why trimpots" but "why two of them" instead of only one trimpot + the cap to ground (either before or after R45)... It probably gives you different results in terms of tone: could you explain me why/how/which? :smile:

About C11: yes, we made something very similar. I decided to go directly with a new 1n cap instead of a cap + trimpot combo because I like simple things and I also didn't want trimpots flying around inside my amp: I gig with this amp, so I need things to be tight inside it...! :spin:

For Alcaraz:
:welcome:
I decided to go for my own mods because the ones at the unofficial HRDlx webpage are somewhat more tricky, because they involve major disassembly, added components/pots, etc... I thought one could improve things by simply altering the values of the original components... and it works!
Of course I cannot say mine are better mods, because I didn't try those other mods. Mine do not involve adding pots, so you can't have a "continuous" control over your mod, you have to go by trial and error and see what is the best value for any given component. At the same time, my mods are very easy and quick to do, they do not need you to take the PCB out of the chassis, you won't have to find a place to secur the trimpots inside the amp or to drill new holes for pots.
I came up to my mods by looking at this and other schematics, and by reflecting over the meaning of each component inside the HRDlx.
I made a quick description of each mod in my first post. If you need some more explanations about their meaning you're free to ask! :smile:

I, too, enjoyed repairing and modifying my HRDlx, and did most if what's been talked about here:

http://www.tjadamowicz.com/pMach/ima...s/HRDmod09.jpg

Lots of fun. However, one word of caution, the PCBs are fragile and can't take too many mods. Even left alone, the PCBs are not very sturdy considering the way the circuit is designed.

In the end, I did the ULTIMATE HRDlx mod, it's perfect now.

Sorry, I had a problem with my post, read below.

Quote:

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Originally Posted by ²Thom

You have to try them all if You like. Tastes are different. :spin:

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²Thom is right, you have to try and see what you like.

Quote:

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Originally Posted by ²Thom

Some other mods are not so good I think the C23 mod to fatten up the drive cannel but it makes the distortion sounding bad. To much distortion in the interferences of minor chords. For that make a high cut at C11 or the other mod shown above in the postings.

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I know the C23 mod increases intermodulation distortion, but I think it is necessary to have a larger value cap there to avoid the excessive low-cut.

Quote:

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Originally Posted by ²Thom

Instead of a C1 mod (half the value of the cap) you can plug in a lower Gain Tube (12AT7 or ECC81) in V1.

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The C1 mod is not primarily for gain, it is most of all because it reduces bass. However, a lot of people found a 12AT7 is a good fit for V1.

Quote:

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Originally Posted by ²Thom

Personaly I like to short R102 results in a high boost in normal and drive but not in more drive.

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I think you are wrong: shorting R102 results in a fixed high boost when you engage the bright switch, both for the clean and for the drive/more drive channel.

Quote:

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Originally Posted by ²Thom

I never tried the C8 mod. I can read the plans and now I understand what will happen if I change a value. C8 makes a high boost above 106 Hz to bring down distortion in the interferences. For example if You bent some tone to the same on the next string. This wawawawa wa wa wa wa wa wa in tune in the Background of the tones from the two strings. To beware these wa-wa-s from distortion there was a C8.

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??? :arhhh: :D I think I understood, anyway. Again an increase in intermodulation distortion (for the more drive only, however) with my mod, but it avoids the really unnecessary high boost in the more drive mode.

Reading again the Jame Vanden Berg mods, I'm curious to try the part of his "lead mode sparkle boost" mod which regards C3. I already thought about working on C3 to reduce high content in the drive channel (that cap forms a low-pass RC filter with R8, reducing high frequencies above 6.4k only with the drive/more drive channel). His clever mod lets you have that high-cut only with the more drive, keeping highs in the normal drive channel. However it is a bit too complicated and involved to be a "quick and easy mod" (following my phylosophy), so I'll think a lot before I'll do it. I must be sure I need more highs with the normal drive channel.

Unfortunately we only have one set of tone controls in this amp, so we must find the magic setting for the clean channel, and only then do our mods to have a balanced sound in the drive/more drive channel (this is true only for mods regarding the components exclusively used in the drive/more drive channel, of course).

Hey! thank you very much! ²Thom and shredgd.

I think it's going to be harder that I thought!
I didn't like to add pots either, so I think I'll follow your mods and see what I get. To take the PCB off you have to uscreew the controls and 6 screws, isn't it?
So I think I'll try the middle pot mod and the bright mod (add 2 silver mica caps)
.
Then I read these changes:

C5 -> 0,022uf
C7 -> 500pf
R12 -> 56K

what do you think about that?

²Thom, you advice me to change C11 instead of C23 in order to get a better distorted sound?

what about C8 should I change it or not?


thank you again! :spin:

It won't be hard at all!!

I think you can start modding your amp without taking the PCB out, as I did.
First of all, the mid pot mod has the disadvantage of making the mid and bass pot interactive, that is when you increase the mids you'll increase the bass, too. So, before doing that mod, to reduce the excessive bass of this amp, I suggest you to set the mid knob higher, in order to have a relative decrease in bass. Yesterday I discovered how sweet this amp can sound by placing the mid knob at 12!!

Changing C5 to 22n will decrease bass and increase mids a bit. I didn't modify C5 because 0.1u (100n) is the original value of Fender's tone stacks, so why bothering? However, theorically this mod goes in the right direction.

Reducing R12 to 56k will increase bass, mid-bass and mids. Again, you'll get farer from the original Fender's tone stacks values. This time, however, the change goes in the wrong direction, because of the increase in bass and mid-bass. I wouldn't do this.

Increasing C7 to 500p will brighten things up. Watch out! This means you'll also get more treble with the drive/more drive channel! I wouldn't do this.

I absolutely suggest you to replace C11 with a bigger cap, to have your first real and evident improvement in your distorted tone. This is the first mod I suggest you to do. Then you will see if that is enough or you have to go further (I suggest you, in sequence, to reduce R9 to 100k to brighten the clean channel only, and to increase C23 to maybe not 10n but 4.7n - this value is also suggested in the unofficial HRDlx guide, and I will probably change my 10n to that value too, now that ²Thom scared me about intermodulation distortion... :D - to increase bass in the drive/more drive channel only).

Thank you very much for your advices shredgd!

I like the idea of starting with those easy changes. I will do it on xmas when I'm planned to replace the tubes.

One last question: which kind of caps should I use? I've heard some people saying orange drops are better for these aplications, while others say it doesn't affect.

This is how these amps get busted, and a bad rap. Cook up that pc board with these "mods", then bitch about it crapping out in a few weeks. Leave it alone, make sure to not judge it until the speaker is good and broken in, open her up and let it wail.

Or do what I did - sell it and biy a Vox AD50VT. ha!

A quick update about my mods.

Today I took off the 10n cap I had paralleled to C23: ²Thom was right, it is better to keep the original value for that cap. Probably when you fix the treble harshness of the drive/more drive channel, then you don't need a bass increase anymore (it makes your bass notes mushy, kind of a fuzz face. You lose definition). Alternatively, a small increase (for example 2n) might be the perfect balance. I will come up to a stable conclusion when I will try my amp loud, so I'll see if it is ok with the original cap or not.

Today I also added another 360p cap in parallel to C11, reaching a total of 1,36n for that cap position. Now the drive/more drive channel is smooth, but again I will have to check my mod at high volumes.

Giulio

Hi shredgd,

1+

If i did a mod I test it with the Band, loud. Therefore the trimmpots. So I can reverse the Mod by dialing it out. My last Value for the C11 was 1.5nF in series to ~150k and a very dark sounding V3.

Quote:

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Originally Posted by Hutch

This is how these amps get busted, and a bad rap. Cook up that pc board with these "mods", then bitch about it crapping out in a few weeks.

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More like "these things crap out all by themselves. They don't need any additional help."

Anohter wide Field for mods is R69 - th coupling resistor between secondary wire from the tone-transformer to the input of the power amp or better the Presence-cicurit.

Try a cap parallel or in series to it (gives more bass). In series is not difficult. Its the grey thin cable from the Ext. Speaker - Jack.

If the Value of R69 gets to high or much to low, the Presence control wouldn't work propper anymore.

The higher the value the more the sound is getting "british". (as a fender can do so?!?)

Quote:

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Originally Posted by Hutch

This is how these amps get busted, and a bad rap. Cook up that pc board with these "mods", then bitch about it crapping out in a few weeks. Leave it alone, make sure to not judge it until the speaker is good and broken in, open her up and let it wail.

Or do what I did - sell it and biy a Vox AD50VT. ha!

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Hi Hutch,

the PCB is industry standard 1.5 mm Epoxy with 35 or 50 µ copper layer and if the solderjoints of the mods on top of the board are propper they are rock solid. :smile:
The problem is that the PCB is verical and not horizontal and the Resistants for the +-16V are getting to hot

I dont know why Fender uses Sovtek tubes JJ are cheaper and better and the speaker (125 (no)legend ) is crap I prefer Jensen C12N.

Now my HRDLx has a crisp, tight low end clean a thick drive (from SRV to Hendrix) which is very controlable by guitar volume and a creamy (garry moore like) more drive without any extra pedal in front of it.

Therefore we are modding.

If you are bying an 22-40W amp fore 2500 bucks there is no need for modding but a HRDLx (600$) with other tubes (JJ's all ~60$), a speaker (100$) and 3 mods (reverb, R24 and R45) (3$) it sounds pretty the same.

So what is Fender doing? They couldn't sell a 700$ amp that is sounding better than their 1500$ Amps. Its the same with Squire-Guitars the wood is good, the hardware is cheap but ok and the pickups are super shitty. So what are you doing with a Sqire-Guitar? put in some original PU's and its sounding like the original. :smile:

So Mery Cristmas to you all and a good start into the new Year!

Here are my Hot Rod Deluxe mods. The sound is very smooth and even (no more ice picks!), the clean tone sounds like a Twin (without the twang), and you can actually work with the drive channels for a change! Tubes: V1-JJ ECC83S; V2-JJ ECC832; V3-Mullard 4024 AT7; JJ 6L6's for the power tubes. Speaker: Jensen 12-70 Mod 8 ohm. Cost of mods: < $170 (take that Celestion!). It's a really nice sound for a MIM amplifier. Best, Malcolm

Quote:

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Originally Posted by mgm7810

Cost of mods: < $170 (take that Celestion!).

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My mods cost about that and I got a Tweed Pro out of it.

http://www.tjadamowicz.com/amps/gall...Dconverted.jpg

:D

Looks nice! What kind of power tubes are those?

Those are SED Winged C 6L6GCs. Very nice, but they bias differently than a lot of other 6L6GCs.

I bet it sounds sweet. I am tempted to convert to Yellow-Jackets for that EL34 type of sound, but I am happy with my rig the way it is. How does that Patriot speaker sound? I'm speculating that it's similar to an old Jensen sound.

The Eminence Patriots are amazing...right out of the box and for the price. They're my new favorite.

Not sure if I'd call it an 'Old Jensen' sound, but it was the right sound for my tweed build. I would suggest the Texas Heat for your Hot Rod Deluxe.

Hey gang: here's a question for yall (and please don't respond with "trash the Hot Rod Deluxe," because I don't own a lemon HRDlx). I am contemplating replacing some electronic components to my HRDlx, as I am currently in the process of overhauling my '66 Bassman with new electronic parts. Are there any electronic components recommended over the HRDlx stock parts? I really don't like it when an amp breaks down (it is sort of like when your car breaks down). Thanks! Malcolm

If you look up in post #9, I posted a pic of my Hot Rod with my mods.

Replacing the tone stack caps and phase inverter caps with higher quality makes for a difference. In that pic, I used Sprague OD 715 series, but I would suggest the 225 instead if you want Sprague ODs.

Otherwise, try some Mallory caps in those areas.

Also, increase the value of C23 to taste. It helps the drive channels.

Quote:

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Originally Posted by mgm7810

Hey gang: here's a question for yall (and please don't respond with "trash the Hot Rod Deluxe," because I don't own a lemon HRDlx). I am contemplating replacing some electronic components to my HRDlx, as I am currently in the process of overhauling my '66 Bassman with new electronic parts.

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The boards appear to be fragile enough that I wouldn't recommend replacing parts just for replacing parts sake. The parts themselves aren't the weak link, it's the general construction. I'd advise against it, unless you're pretty confident in your PCB soldering skills, and know specifically what you want to do.

Quote:

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Originally Posted by NTBluesGuitar

My mods cost about that and I got a Tweed Pro out of it.

http://www.tjadamowicz.com/amps/gall...Dconverted.jpg

:D

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NTB, that layout looks so nicely done - wish I had your skills with a soldering iron and tube circuit...

I've always jonesed for a tweed vibrolux or tremolux, myself...

DAMN NTB. That is a freakin' flawless wiring job there.

If that was my amp I'd put a clear plexiglas cover on the back. :D

Outstanding work. :appl:

hey NTB. What would you charge to do something like for me if I were to pick up an HRDlx/deville? I live in Lewisville. That looks amazing. And, for the money it would cost me to move into a DRRI, I assume that I could buy one used and then look into a change like that.

If you'd be into something like that. Feel free to email me at chumpster@gmail.com.

NTBG, if you have any more pics of your "Ultimate HRDx Mod" can you send them to me? I would really like to see them. You can email me at hippiebob01@aol.com.

kcwm, if you're in need of a hand-wired tweed circuit, it's probably easier and cheaper to purchase the proper kit and have someone build it for you.

Well, Rickenjangle, if you score a Hot Rod for anything less than $400 and buy all the parts I used, you come out well ahead from a similar kit (Tweed Pro is $620 at Weber). That's the main reason I worked out my build re-using all the same iron and hardware.

But you're right...it doesn't make sense to do this to a new, more expensive working amp. It sure is fun though!

Quote:

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Originally Posted by Rickenjangle

I've always jonesed for a tweed vibrolux or tremolux, myself...

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I'm currently planning out a '63 Brown Vibroverb. Just building it with the vibrato channel and a bright switch (takes one tube out of the question), and I'm going to build it into a narrow panel tweed cab; 2x10.

:D

Hippiebob, Boobtube, and Kwcm...I thought I posted that pic before... regardless, thanks for the compliments! It's my favorite amp so far...and I've got a 5F1 I built, and played a few SF reverb amps.

As far as other images....they're around TFF somewhere. Here's one with the faceplate I had made:
http://www.thefenderforum.com/forum/...5&postcount=24

I think there's sound clips of it here:
http://www.thefenderforum.com/forum/...ad.php?t=35879

There's the original thread where I shared the prototyping process with help from all the groovy TFF'ers around too. Search and you will be rewarded. :D

Hello,
Shredgd,²Thom, what about those mods? I'm going to order some components and I'd like to know if the values are correct:

C11 -> 1,5nF (less highs for the drive)
C1 -> 22uf (less bass for the clean)
R9 -> 100k (more brigth for the clean)
Short R102 (add gain to Clean and drive -not more drive-)
Cut R103 (improve reverb)

That's all isn't it? My V1 is a TAD 12AY7, should I leave the original C1 value?

Thank you!

Quote:

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Originally Posted by Alcaraz

Hello,
Shredgd,²Thom, what about those mods? I'm going to order some components and I'd like to know if the values are correct:

C11 -> 1,5nF (less highs for the drive)
C1 -> 22uf (less bass for the clean)
R9 -> 100k (more brigth for the clean)
Short R102 (add gain to Clean and drive -not more drive-)
Cut R103 (improve reverb)

That's all isn't it? My V1 is a TAD 12AY7, should I leave the original C1 value?

Thank you!

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Order a 1n cap for C11, as well, so you can decide if 1,5nF is too much or not.

If I were you, I wouldn't leave the original C1 value even with that lower gain tube in V1. But I've never tried a lower tube in V1 so I'm only talking by theory: 22u is the standard Fender (and not only) value for that cap. Why keeping that oversized 47u?

Shorting R102 won't give you what you said, but it will only make the bright switch active for the drive/more drive channel as well. I don't think that is desirable, because we all agree the drive/more drive channel is too bright to begin with, so keeping the bright switch a clean-only feature might be more useful (as a stock feature the bright is automatically turned off when you use the drive/more drive channel; this might allow you to keep a darker equalization in order to make the drive/more drive channel better sounding, without sacrifying the clean channel highs. Anyway I personally don't use/like the bright switch at all).

Giulio

Thank you Giulio! I'll leave R102 then.

For C11 I'm thinking about putting a cap in parallel so I'll order a

610 pF cap (390p//610p = 1nF)

and a 1,1nF cap (390p//1,1n)

do you think it's better to change the original cap instead of adding another in parallel? :speechles

Parallel is fine, it allows you to go back to stock whenever you want.
As you can read above, I actually got almost all my new values for caps and resistors by using parallels...!

Giulio

Thanks Giulio!

I see I'll have to cut out C1 (47uF) and replace it for a 22uF CAP as I can't add anything in parallel.

I have read some mods for the tone stage such as:

Treble cap: C7 (250pF) -> 500pF
Bas cap: C5 (0.1uF) -> 0,022uF
R12 (130k) -> 56k

what do you think about them?

Quote:

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Originally Posted by Alcaraz

Thanks Giulio!

I have read some mods for the tone stage such as:

Treble cap: C7 (250pF) -> 500pF
Bas cap: C5 (0.1uF) -> 0,022uF
R12 (130k) -> 56k

what do you think about them?

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Those are more like Marshall values. I dont think they work well in Fenders. The only change I'd do is R12 to 100K and C5 to .022.

Ok! Thank you JAM! I'll start from the basic mods then and leave those!

Quote:

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Originally Posted by Alcaraz

Thanks Giulio!

I see I'll have to cut out C1 (47uF) and replace it for a 22uF CAP as I can't add anything in parallel.

I have read some mods for the tone stage such as:

Treble cap: C7 (250pF) -> 500pF
Bas cap: C5 (0.1uF) -> 0,022uF
R12 (130k) -> 56k

what do you think about them?

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In my previous message I was about to write: "You forgot a 100k resistor for R12 ;-)". Then I decided not to write it, because, that mod actually increases bass, which is not what we want with this amp. However, again trying to go as close to a standard Fender circuit as possible, I did that mod in mine (you can read it at the beginning of the thread), and the mod is still there. I did the mod together with something else, so I can't judge about it alone, but at least it doesn't sound bad! It narrows the mid cut achievable with the mid pot, if you want a further technical explanation (not that I have noticed that, though...). However lowering it to 56k is too much, IMO. Again, the standard Fender tone stack slope resistor is 100k.

Those C7 and C5 stock values are Fenderd standard, too. Why changing them?
Doubling C7 will give you a permanent bright function, which might not be helpful with your drive sounds. However, the bright switch of vintage Fender and also Mesa amps actually adds a cap in parallel to the 250p one. So if you're only using this amp for cleans and you like a vintage Fender amp with the bright switch on, you might like that mod. As it is a simple paralleling mod, you might try it temporarily and then go back to stock.
Reducing C5 to 22n will cut some bass and give you more mids. This is theorically in the "right" direction for this amp, but I think it will change the whole character of the amp a lot.

However, if you look for "duncanamps tsc", you will find a freeware program that allows you to see how the different values in tone stacks affect the frequency response. It is very nice, and it will guide you through the most appropriate mods for your tastes.

Giulio

Quote:

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Originally Posted by shredgd

Doubling C7 will give you a permanent bright function, which might not be helpful with your drive sounds. However, the bright switch of vintage Fender and also Mesa amps actually adds a cap in parallel to the 250p one.

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I dont know amout Mesas, but Fenders use a 120pf cap across the volume contol for the bright, not a parallel 250pf with the existing 250pf in the tone stack. I have seen the additional cap used as a 'mid boost' however. It's a matter of taste ultimately.

Quote:

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Originally Posted by JAM

I dont know amout Mesas, but Fenders use a 120pf cap across the volume contol for the bright, not a parallel 250pf with the existing 250pf in the tone stack. I have seen the additional cap used as a 'mid boost' however. It's a matter of taste ultimately.

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That's why I wrote "a cap" and not "a 250p cap" ;)
Mesas use a 750p, in fact.

Giulio

Thanks again! I'll start from C11, C1 and R9. I'll also try the R24 cap and the trimmers that Thom suggested for R42 and see what I can get.

I cut R103 and now the reverb is great! :)

Quote:

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Originally Posted by shredgd

That's why I wrote "a cap" and not "a 250p cap" ;)
Mesas use a 750p, in fact.

Giulio

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I had 250pf on my mind, which I've seen used, but my point is it doesnt add brightness. The Gxx series Yamaha amps (SS) did a similar thing for a 'pull fat' for example.

I use EL84s in my HRDx and it rocks. No soldering and completely reverseable at a gig in 1 minute flat. Just like the manual says, no rebiasing needed - I checked before and after and it was dead on. If you want sound clips, I've got them.

Cheers

I'd love to hear som nice clips JJGross :)

I am having trouble finding a good place to get caps. Can anyone recommend a place?

One seems to be a problem. The C11 cap is listed on the schematic as 390 pF @ 1kV. I can't find anything that is rated for 1000 V.


I already cut R103 and the reverb is much more manageable, sounds great.

That cap could be changed to a 47pF, I did that.

Shouldn't need more than a 500V rating.

Quote:

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Originally Posted by NTBluesGuitar

That cap could be changed to a 47pF, I did that.

Shouldn't need more than a 500V rating.

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Are you sure for C11? Seems like that would let even more high signal through to the drive channel. I already have problems with highs in the drive and want to cut out more highs in the drive. Most people are suggesting an increase at C11 to 1.4 - 1.5nF

C11 is basically a 'bright cap' on the MV. As a bright cap, 390pF seems quite excessive.

Going to a 1.5nF is the same as 1500pF. Really excessive, IMO.

I see that a lot of people are complaining about their drive channel being muddy and the decrease you suggested to 47pF is a typical mod. I seem to have the opposite problem with my HRDx and have too much high chimey sound in my drive channel. Since I can increase the value on C11 by adding a cap in parallel, that's what I'll try first to see, if I don't like it, it's easy to remove. For the mod you suggested, I would have to replace C11, which I might try later.

At any rate, where do you get your parts from, I would like a recommendation for a good place to order them online as all of my local electronics shops have been put under by Radio Shacks.

Quote:

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Originally Posted by Falco

At any rate, where do you get your parts from, I would like a recommendation for a good place to order them online as all of my local electronics shops have been put under by Radio Shacks.

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http://www.mouser.com/

http://www.tubesandmore.com/

http://www.tedweber.com/

Thanks, JAM.

I usually order from Mouser, too. Try both caps to see which you like better, they're really cheap.

Quote:

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Originally Posted by NTBluesGuitar

C11 is basically a 'bright cap' on the MV. As a bright cap, 390pF seems quite excessive.

Going to a 1.5nF is the same as 1500pF. Really excessive, IMO.

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Maybe you are referring to another cap, C11 shunts high frequencies to ground!

Giulio

HUGE WARNING !!!
I opened my amp, and see that 3 resistors aren't at schematic's value (11 august 95, rev B.)
all values are in first stage of normal and drive volume....
So R9 is not 220k but 270kOhm on PCB.
R52 is not 180k but 240kOhm on PCB.
it change a little bit the cut-offs frequencies....
moreover, R44 is not 180kOhm but 56kOhm instead.this later control the gain of first stage.

So, before doing any mods to my amp, I will do some further calculations :)
My PCB is dated 2002.

Take care.
Largol.

let me know if you discover something else....

Quote:

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Originally Posted by shredgd

Maybe you are referring to another cap, C11 shunts high frequencies to ground!

Giulio

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Maybe...of course, my Hot Rod hasn't been a Hot Rod in a loooong time, so I forget some of what I did.