Fender Hot Rod Deluxe Discussion

Okay, so Tim and I are starting a new thread to talk about this schematic. Courtesy of Blueguitar.org and Fender(tm) all rights reserved.

So the first thing that I don't like about this is they just use 12AX7s like jellybeans, not taking into account the purpose of the tube function/location in the ckt.

Second thing is the opamp drive for the reverb which is a 600 Ohm input impedance spring tank.

Third thing is all those cursed relays for switching stuff in and out of ckt.

Is this the schematic that you are looking at Tim?

Peace!
Charlie

I like that amp if it the tweed one. I have fixed one the channel switching stopped it looked like one of the 16 zeners and power resistor legs got hot and then unsoldered from the board. I guess the heat and vibration caused this. In that repair the missing supply caused the solid state switching not to work corrrectly.

http://www.accutronicsreverb.com/schemat.htm

Some cool schematics.

Gus,

I certainly respect your opinion. But I find some of the new Fender amps to sound a bit like a buzzsaw. I think there is just too much gain thru the whole preamp and its hard to balance out the controls to get the classic Fender sound, IMO. We stuck a 12AU7 in place of V3 in another friend's amp the other day. It really improved the overall tone, we all thought.

I don't think the reverb sounds good either. I have heard a few guys say that removing the HF bypass cap C52 that's around the verb pot to really help.

I am currently working on modding a Crate V16 (same handful of tubes as the Blues Jr.) and it uses a TL074 to drive a 150 Ohm verb tank. Duh! I was looking at the schem for a Traynor amp last night and that particular one used two 5532 in parallel to drive the verb tank. I have another opamp in mind for the Crate.

I just don't understand why they stopped short on driving the verb with a tube??

Most of the verb tanks are less than USD$40 if I have my facts straight, btw.

Peace!

I should have looked closer at the title. The first tweed one is different than the hot rod, one less gain stage IIRC. I will look for a tweed schematic.

Its cool Gus.

Maybe you mean the 5E3 Tweed Deluxe? Fender calls the current offering a "57 Deluxe". No reverb though, but no doubt a Tone Machine!

The AA763 Deluxe Reverb is the thing we all crave, IMO.

Peace!

The Blues deluxe that was the model before the hotrod. The blue guitar site has a schematic of it.

Gus,

Cool, not a lot different but does have less crap in the way. Still has opamp line out and reverb ckt. If you still have access to this try a 12AT7 or 12AU7 for V3 and tell us what you think. I have decided that they don't want to buy "another part number" when the 12AX7 "works"...

For the "Drive" thing, I don't know why they didn't use the leftover triode set up like your normal CC amp and then switch it in and out of the ckt. That would be one less relay, yes?

At least Fender is using 600 Ohm verb pans, though I think a higher impedance or a different opamp is in order here.

Peace!

I can't comment on the circuits, but I have a Blues Deluxe. When I bought it, there were two Blues Deluxes (tweed) and Two Hotrod Deluxes (tolex) in the store. They were very different sounding amps, with the Blues deluxe winning out by a strong margin to my ears. I agree about the reverb. It's not bad, but I've definitely heard better. The high gain setting on the amp also leaves something to be desired, but for clean to OD, this amp chunks and chimes all day. It among my all time favorite clean amps.

I was always curious as to what they did to the "Hot Rod" version that killed the tone (to my ears).

-Chris

-But I find some of the new Fender amps to sound a bit like a buzzsaw. I think there is just too much gain thru the whole preamp

That is because they filter out all the low end, and a good chunk of the middle before going into the high gain sections. I have one, I got it for pretty much free, I have thought about modding it, but it just does not seem worth it. With a better output transformer it is really capable of some great clean sounds. Every time I think about modding it, I realize it would be easier to just build a new amp in its carcass. Just the idea of taking the circuit board out drains me.

-Second thing is the opamp drive for the reverb which is a 600 Ohm input impedance spring tank.

I am currently working on modding a Crate V16 (same handful of tubes as the Blues Jr.) and it uses a TL074 to drive a 150 Ohm verb tank

I use a 150 ohm tank with my HRD, one of those cheap Type 1 tanks that I am not sure are even made anymore. It sounds great. Cutting that cap will help some, it will get rid of some of the boing.

For guitar range some of the loading effect caused by the inadequate driver can be fine, we do not need to get from 20hz to 20khz.

-Third thing is all those cursed relays for switching stuff in and out of ckt.
Ignore it, I never use those switches, it makes a fine clean amp, and it works great for kids who want to make noise. It is what it is.

I really do not think you will be able to get much out of this amp by simple mods. Like I said, less work to build a new amp in its carcass.

The cutouts on the chassis for the 12AX7s are 1" or was it 1 1/8", perfect size for octal sockets. I have been thinking about making mine a B15ish amp for awhile. Single channel , have a tube left over for some reverb duty.

adam

Yeah, that's the schematic and you're correct - it buzzes like a saw in the drive settings. But, we aims to fix that! :wink:

(Gus, I was going to ping you about this but I see you're already here.)

I picked up this used HRD cheap at GC the other day and thought I have some fun trying to make it sound decent. I'm willing to try just about anything except throwing out the board all together and replacing the transformers. I know Mercury's would be great, but I don't want to go that far just yet.

I'm planning to re-tube, replace the speaker, and perform whatever mods I can without hacking up the pc board. I'll try and record samples along the way to measure the progress.

Here's my initial thoughts:

You can tell right off that this thing was designed to sell itself at the music store. Volume is about 95% loud with the knobs set at "3". Going past that doesn't get any louder.

In the "clean" mode, the power tubes start breaking up right around "3". From that point on, it gets more distorted, but only slightly louder. (Not bad sounding either, but could be a little better.) Needs more headroom imo, and I'm hoping a re-tube will fix that. The power tubes are GTs with the white print, which I think are mid-way between lowest and highest headroom.

In the "drive" and "more drive" modes, it's just nasty and un-musical to my ears. Not only that, but if you turn up the master volume in "more drive" mode, it's even nastier and sequels like a pig. The only good thing I can say about "more drive" is that it has plenty of sustain.

Anyone else have one of these?

[quote author="SonsOfThunder"]I am currently working on modding a Crate V16 (same handful of tubes as the Blues Jr.) and it uses a TL074 to drive a 150 Ohm verb tank.[/quote]
HRD uses a TL072, so a 5532 will drop right in and not much more trouble to parallel a couple.

I completely agree - blues deluxe is better sounding and I may end up with a similar circuit before this is over with. Want to try some other things first, tho. I'm making a list...

Wow, that HRD has some stuff in it that reminds me of my Champ-12 (single 6L6 thing from the late 80s). Except back then Fender used dual LDRs for "channel switching" instead of relays. That thing had a heinous "drive" channel, but I modded it. Need to do some more now that I know more.

Anyway, maybe you could try swapping in a 12AY7 for V1 to tame the gain. Speakers--what does it have now? My Champ-12 has a 12" Fender "Special Design" which I plan to swap out--maybe for an Eminence Red Fang.

A P

replace the speaker,

I would say the speaker is the amps strong point, but alot of people do find it bass heavy. It sounds and looks alot like the Eminence V128s I used to have.

You can tell right off that this thing was designed to sell itself at the music store. Volume is about 95% loud with the knobs set at "3". Going past that doesn't get any louder.

It is a linear taper pot, some of the old amp companies used to this for master volumes. I believe they did it to give finer control of the volume at stage volumes, not so you can play it really quietly at 3 am with loads of distortion.

In the "clean" mode, the power tubes start breaking up right around "3". From that point on, it gets more distorted, but only slightly louder.

Yes better tubes will solve that, I get up to around 7 or 8 before the clean channel starts to get crunchy.

In the "drive" and "more drive" modes, it's just nasty and un-musical to my ears. Not only that, but if you turn up the master volume in "more drive" mode, it's even nastier and sequels like a pig.

Thats them filtering out all of the low frequencies, cheap way of getting good not definition and lots of distortion. Put it in the more drive mode and turn the bass knob, almost no effect, the mid is almost as useless, but it has more effect then the bass.

These amps driving a lower powered speaker and sticking with the clean channel is really pretty great. Throw a 35 watt C12 in there and see what you think. That is my one problem with the speaker in this thing, its to big for the amp. They really wanted to avoid speaker breakup.

I am curious to see what you come up with, I see no simple worthwhile ways to make it suit me for things other then clean.

adam

I forgot to write for a stock amp that you could buy. The tweed blues deluxe is not bad for a mass produced amp. Chris put it the best with his post.

If you want to clean up the drive and other sounds in the amp, try 1uf to 10uf PET caps for the cathode caps in the preamp. From my measuring of caps a GOOD 10uf, 16VDC to 35VDC Al electro will measure about 1.5 ohms ESR a GOOD 1uf PET will measure about 1.5 ohms ESR. A 2.2uf PET is often a nice starting point replacement for a 22uf cathode cap. Panasonic or CDE or what you like. Roger tried different cathode caps for one of his builds.

When I rebuilt my Laney I used 2.2uf PETs cathode caps and polypro power supply caps. When I recapped a pro jr I used Atoms in the power supply it is not nice looking inside, kind of hard to fit the caps. Angela has/had nichicons at 450VDC that measured good IIRC.

I find the first two caps( the output plate and screen power supply part) seem to make the most difference. Atoms might fit.

The stock output transformer does not sound bad to me the other parts of the amp might be what you are hearing.

What do the fils run at in your amp? I seem to remember reading 7.something VAC with the tubes installed.

Tim,

Check the part number on the verb tank. You can look at the "secret decoder ring" at the Accutronics website to determine the input impedance.

I am wondering if you need to keep a FET-input opamp for its high input impedance in these ckts. So I'll go ahead and say that I am looking to sub TLE2072 for verb drive/recovery.

Not sure about the spkr in the HRD, but IIRC (I have been looking at a lot of Epi Valve Jr mods threads of late!) the Blues Jr speaker is pretty well liked after modding the amp.

Next ? What is up with that wacky Brite switch setup? I mean I think I know what they are doing but I don't think I like it.

Something I saw someone else do on a BJr and I did it on this Crate...drive the tonestack with a cathode follower. It seemed to make the tonestack more effective. Maybe take V2a out of the ckt where it sits and connect it as a CF on V1b? R9 needs to be shorted and replace R6 with a 1M pot. Use S1a as a real Brite switch with a cap across R6 pot.

On the Crate, I have been able to "move" tube sections by removing parts and using jumper wires. I think I have only cut one trace so far. They used a too small coupling cap after the first gain stage and when I put in a decent value, the amp got a bit ballsy-er. So far I have removed 9 Rs and 2 Cs and one triode from this amp and it is starting to sound like something good! It came with a Celestion spkr from the factory so its sounds different from the Fender in any case.

Peace!

I am wondering if you need to keep a FET-input opamp for its high input impedance in these ckts.

The output of an average 12AX7 is only around 35k, but, these opamps are also the input and output of the effects loop. The power amp in may not like some guitar FX if you have something other then a JFET in opamp. But who puts those kinds of effects in a FX loop anyways.

Next ? What is up with that wacky Brite switch setup? I mean I think I know what they are doing but I don't think I like it.

I do not think I have ever know anyone who actually used the bright switches on any amp. they flip it a few times then forget about it, maybe flip it every now and then so they can see that it does very little. I leave it off in the HRD it just adds noise.

drive the tonestack with a cathode follower. It seemed to make the tonestack more effective.

Some tone stacks are happier being fed with a low impedance. The HRD tone stack is either pretty close to or is a copy of the old Blackface BMT stack, it would be easier to start out converting it to one of those first before doing something big like a cathode follower.

Here is the site that seems to have the most HRD stuff by far: http://studentweb.eku.edu/justin_holton/

According to this site, the speaker is an Eminence Legend 125 and from what I’ve read overall is that it is sort of dark and low-endy. I tend to like a brighter speaker (as long as it’s not harsh) with some spank and clang, so I’m thinking about a Weber Ceramic 50 watt Blue Dog.

I ordered some Fender style 250KA’s a few days ago from Antique Electronic Supply to replace the volume, drive, and master pots. The schematic shows the volume and drive pots as analog, but mine are definitely linear. The master pot is 100K, but a 250K should work fine, if not better.

I’m certainly going to change C23 to .022uF. I’m thinking about using another J111 FET to switch a 10-20uF in and out of parallel with a .68-1uF cathode cap when switching more drive the way the FETs switch the other cathode caps. More on this later.

I’ll check the filament voltage and the reverb tank # this weekend – I’m going to be tied up every night for the rest of the week, so I won’t get a chance to mess with it until then.

Well, looking at the schematics the BD uses a similar o/p trafo as the HRD but they are different part numbers. Wonder how much this has to do with the difference?

Tim, I ran across that site the other day looking for the schematic. Lotsa cool stuff to try there!!

>>>But who puts those kinds of effects in a FX loop anyways.

No doubt... but I don't see why you need an opamp for the FX loop anyway. Why not cap-couple and be done? Maybe its a liability thing, if the cap happens to short, the possibility of shock hazard exists?

The HRD tone stack is close to the BF/SF tonestack in the Super with the exception of a couple of minor value changes, the wiring of the mid pot and that R105 hanging off the bass pot. I would guess that this is an attempt to prevent interaction between the pots?

It looks easy enough to feed the tone stack from the bright switch to make it cathode follower. Can someone post a picture of the inside? Given carte blanc I would replace the pcb with my own creation, but that is usually not the kind of mod an amp owner wants.

[quote author="SonsOfThunder"]...the BD uses a similar o/p trafo as the HRD but they are different part numbers...[/quote]
Interesting...

[quote author="SonsOfThunder"]...and that R105 hanging off the bass pot...[/quote]
Yeah, what's up with that? It's in parrallel with the total bass and mid pots resistance. Guess I'll find out when I take it out, heh heh.