1996 Hotrod Deluxe Mods / WOWZA!

[plexi50]

I bought a 1996 Hotrod Deluxe this week. I have completed all of the Fromel mods and added a pair of JJ 6V6S tubes. Had to lower the bias resistor to 47K to get a larger trimmer pot swing in DC Milla Volts. All i can say is this amp is dialed in and absolutley a killer clean and mean machine. A .0047 replaces the 1.5n cap going to the drive channel and adds the perfect amount of bass for this channel. I tried a .01 cap here but it was a tad to much bass which i thought was strange. It is tight and right. I have the 6V6S power tubes biased at 44mv which is about 38ma with a 425 VDC plate voltage. I have never like the hotrod Deville much. The HR Deluxe has a lower plate voltage that makes the 6V6S tubes just perfect. 6L6GC are just to bloomy boomy in this amp. I still have a good amount of headroom so not much sacrifice there. Im adding a switch under the chassis edge to lift the feedback. I never thought a Hotrod Deluxe could sound so good. Note articulation is amazing. In other words,the amp is ALIVE! I was just going to flip this amp before getting into making any changes. It aint going no where now. 3 friends have already tried to pry it from me. Thats all the confirmation i needed. My hearing is ok after all!  

[phsyconoodler]

Yes indeed the fromel mods do work.I've done several now and all sounded much better than the stock amp did in every respect.
  Good work!

[plexi50]

Yes sir! I put a SPST switch next to the speaker out jacks to lift the neg feedback as well if desired. Man what a keeper of an amp

[LooseChange]

Gonna tell us what the mods are? Just general overview? Thanks!

[jjasilli]

I did the "Justin" mods from the "Unofficial HRD Website".  Seem to be the same as the Fromel modes.  Agreed that, after modding, these amps sound fantastic. 

Cons:  PIA to work on; not sure the cheap cold-soldered PCB's will ever be reliable.  (Don't see how they could stand-up to touring, but that's not an issue for most players; and touring pro's do use them.)

[plexi50]

The Justin mods are from what i have gone over are the same as the Fromel mods. It's a very informative site and deals specifically with the HR Deluxe & DeVille. I tried the reverb mod and it sounded ok but a lot of the presence of the reverb was missing. I think a different value cap (C52)  reverb would be a better way of setting the reverb shine than cutting R103 out of the circuit


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

[LooseChange]

Lot's of info out there on Mods...
Master volume pot change?
Reverb cap snip?
Blackface Tone control mod (More bass control)?
I do the top three.
Did you do the SAG thing?
What else?
Thanks!

[punkykatt]

.038mA  x  425v = 16w.  Isn`t that kinda hot for 6V6`s ?

[jjasilli]

mods I did to my HRD (see Unofficial HRD website):

*  input jacks > SwitchCraft, chassis mounted
*  speaker upgrade > Celestion Greenback, made in England + 2X 10" vox Bullgogs in a custom built (by me) matching ext'n cab
*  12at7's in V 1 and V2
*  power tube upgrade > TAD short bottle 6L6's
*  carbon comps in the signal path
*  orange drops in the signal path
*  470R 5w resistors > 330R 5W (the stock resistors were burning the PCB)
*  SAG mod switchable > 150R 25W inductive metal housed power resisitor in the B+ rail
*  Plate resistors & 220K power tube mix resistors > carbon comp
*  Master Vol pot > audio taper & jumper the attenuating resistor R45
*  Mid pot jumper mod
*  .022 orange drops in the tone stack; silver mica 250pf cap
*  lead mode bass boost
*  jumper R102 bright mod for drive channel
*  bypass caps for Vol & drive pots 
*  reverb mods
*  diode in B+ rail & .22 orange drop across the last filter cap
*  C1 > 4uf
*  22uF cathode bypass cap added to V1b

[plexi50]

.038mA  x  425v = 16w.  Isn`t that kinda hot for 6V6`s ?

I got the ma wrong when i said 38ma @ 425PV. I have to check it again later. Right now i have it set at -42mv @420PV
The master pot swap from linear to audio makes a huge difference in tone and ramp up. It just keeps getting better. I put all CC plate load resistors in R4-R11-R16-R22-R57-R58. I have some nice wavy action going on. Sort of stereo sounding effect

I wonder if anyone makes a female 6 pin connector that i can solder to the boards for V2&V3 to get rid of these gray ribbon cables which are going to break loose if i keep going in on this. Then use a male 6 pin plug cable. I say im done now. But we all know thats a (lie!)

Looked at the Sag thing and may or may not try it. I would need the chassis mounted 25watt 150r resistor. There cheap like 5-8 bucks

[phsyconoodler]

I also add 100pf caps across the volume and drive controls.Very nice for both channels.

Makes a mediocre amp a keeper.I've done lots of these for customers.Another improvement is using good filter caps.It does seem to make a bit of a difference.I tried before and after with just filter caps.I used Sprague Atoms in one and F & T in  another and both were smoother than the Illinois but not enough to write a book about it.(GW content)
  The biggest and best filter cap change was upping the first cap to 100uf or using two 47uf caps.It really tightens the bottom end.

[plexi50]

I also add 100pf caps across the volume and drive controls.Very nice for both channels.

Makes a mediocre amp a keeper.I've done lots of these for customers.Another improvement is using good filter caps.It does seem to make a bit of a difference.I tried before and after with just filter caps.I used Sprague Atoms in one and F & T in  another and both were smoother than the Illinois but not enough to write a book about it.(GW content)
  The biggest and best filter cap change was upping the first cap to 100uf or using two 47uf caps.It really tightens the bottom end.

Good thinking on the 100uf 1st stage filter cap. I just happen to have a bunch of 100uf/450V caps i ordered last month. Now i have to go in again!  

I put one 100uf/450VDC in the first stage. Your right ! Tighter bass. Great! Im going in search of the switchcraft input jack swap next/

[John]

Plexi, on those CCs you put on the plates: did you notice any increase in hiss? Also did you use 1/2 or 1 watters?

I haven't used any on my couple builds, but of course my first repair job was all CC and that's what I used. I'm thinking I might just try them in my Pentup Six when (not if hah) I open it up again.

Thanks!

[plexi50]

John the hiss i had with the stock resistors was far more noticable and high pitched (sharp)
The CC have less hiss and sounds smooth and more filtered . Though i did add a 100uf/450 cap to the first stage. Over all to answer your question i would say CC resistors in the signal path are King and have a very nice noticable change to the amps tone. I havent been this excited in a long time with the results i have gotten

[John]

Thanks for the reply. Like I said, each new one I've built I've went back and forth whether I wanted to use them or not. I was planning on digging back into mine to put a bigger cap on the first stage anyway. It sounds great but the bass is pretty loose on the low power chords.

Now I've got an excuse to order more stuff from Doug! 

[plexi50]

Thanks for the reply. Like I said, each new one I've built I've went back and forth whether I wanted to use them or not. I was planning on digging back into mine to put a bigger cap on the first stage anyway. It sounds great but the bass is pretty loose on the low power chords.

Now I've got an excuse to order more stuff from Doug! 

The 100uf cap makes a big difference. I like the 6V6S tubes over the 6L6GC. Plenty of punch and more articulate tone to my ear

[John]

I haven't tried 6L6's. Right now I have some cheapie Russian 6v6s (Hn9 or something like that) and I tried a pair of 5881s which I really liked too. I'll definitely up my first stage filter for sure. Thanks again!

[Colas LeGrippa]

Would anybody have a schamatic for Fromel mod ?

Tanks

Colas

[Colas LeGrippa]

maybe we can do a trade for yellow jackets schem ?  

[jjasilli]

Would anybody have a schamatic for Fromel mod?

Colas:  checkout schematics & instructions here:  http://www.justinholton.com/hotrod/

maybe we can do a trade for yellow jackets schem ?  

Yellowjacket circuits have been posted on this forum, I think more than once.  But here's one thanks to FYL:  http://www.el34world.com/Forum/index.php?topic=11045.0

[Colas LeGrippa]

yeah I know, I think I was  the first to post the schem here, after taking one apart !

merci beaucoup, brother.

Colas

[Colas LeGrippa]

I already have Justin's mod, the same as Fromel ?

[jjasilli]

I already have Justin's mod, the same as Fromel ?

Yes, that's the general consensus per earlier posts in this thread.

[Colas LeGrippa]

I love you.

[plexi50]

I would love to learn how to make a PDF file. I never got around to learning about it. Here is a High Res PDF. I want to show all the changes but dont know how/ By the way i looked closer at the Drive channel plate coupling just before the master. I am going to change this from .047 to .022. I'll let you know what happens. I think it will smooth out the bass on the Drive channel a bit more from the cap change made at C23 .0047 with R52 shorted
http://www.triodeamplification.com/files/hotrod_deluxe.pdf

[Colas LeGrippa]

well if your program is up to date, when saving a file  you have the choice of the format you want the file to be saved as. As simple as that.

Colas

[plexi50]

I'll figure out the PDF thing someday. I finished off the HR Deluxe tonight with all CC resistors in the PI,Grid,Bias coupling and feedback. Changed the .1 coupling caps out for .047. A little tighter on the bass. Also put in the switchcraft input jacks this morning. I havent had this much fun and killer tone change in an amp in a while

[plexi50]

.047 coupling caps sucked. Lost a lot of the fullness. .1 coupling caps back in. Some one slap my hands and call it done!

[Colas LeGrippa]

I have one HRD that the customer wants to get rid of. Maybe a good opportunity to get one cheap, and mod it up to my taste !