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Hoffman Amps Forum image Author Topic: Should I build a Hoffman ab763 Deluxe reverb? help advice needed  (Read 9634 times)

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Offline njkmonty

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Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« on: September 01, 2016, 06:43:44 pm »
I currently have an 18 Watt TMB withh PPIMV, VVR & Radio shack attenuator thing.


I only use the normal channel and either play it clean or use vvr etc to push the power tube for overdrive.
I currently also have a Roland JC120  and  a Sloclone 50


I recently sold My Fender Twin amp (Pro tube Series)

http://ww.w.shoppersgalaxy.com/instrumentpro/by-manufacturer/fender-amplifiers/fender-pro-tube-guitar/fender-twin-amp.html
this is a gutshot of the one i sold...

I remember researching about modding this amp a few years ago and was told dont waste your time.

my question is...

1) how much different sounding is the 18 watt to deluxe reverb?   ( clean that is ?
2) how much different sounding is the  deluxe reverb  to  the above mentioned twin amp?

I guess im trying to determine if i need to build another amp or not, I do like the occasional tremolo and reverb.

also i noticed that the hoffman ab763 uses bias tremolo over the ldr based,, I assume this is more sonically pleasing, would love to hear peoples thoughts!

Offline MakerDP

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #1 on: September 01, 2016, 06:59:06 pm »
A Deluxe Reverb is a VERY different animal to the 18W. Well to ANY Marshall for that matter.

With a VOX, your 18W TMB and a Deluxe Reverb, you have pretty much covered all the bases.

IMHO, it is a must-have tone in every serious guitarist's arsenal.


So, YES if you are thinking you may want to build a Deluxe Reverb clone, DO IT! You won't be sorry.

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #2 on: September 01, 2016, 11:49:45 pm »
ok I have many other questions regarding this build should i ask them in this topic or a new one for each question?

Offline eleventeen

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #3 on: September 02, 2016, 12:20:27 am »
I say stay on this thread. Obviously, you have the chops to build an amp, that's apparent from your pix. All I think anyone would ask is to ask your Q's 3-4 at a time.


I have one of those Twin Amps for sale, too. CHEEP. Want it gone.

Offline drew

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #4 on: September 02, 2016, 12:47:59 am »
You might want to think about whether all you really need to build are a trem pedal and a reverb pedal, which could be done for a small fraction of what a full DR build will run you. 

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #5 on: September 02, 2016, 04:36:43 am »
ok here goes 3-4 at a time! :)
I will enclose some pics too as I got together stuff I already have for a new build.
Ive started writing a list  so I will go from that.

1) which is the recommended rectifier to use?   5AR4 / GZ34 Tube Types  or 5U4GB  or something else?
 
2) I have used Sprague atom axial power caps before and also F&T Can Caps and JJ's before ,
while researching some 16uf /475v   and 22uf /500v   the Sprague Atom's are almost double the price as the F&T Axials.  why is this?
they are both good power caps arent they? or should i stick to Sprague?
I dont want to use the real cheap ones, If the F&T's are just as good , well I will get them, I am making this for sound quality, not trying to make an exact replica,

3) I have some unused Hoffman Turret boards and about 200 turrets and turret tool. I have 4, they are 12" long by 3.125 inch wide.
my question is i was going to use these to make a 2 channel deluxe hoffman layout

 http://hoffmanamps.com/MyStore/catalog/images/IMG_8481.jpg

which from my research has 121 turrets and is 15.63" long.(I cant find out how wide. is it ok to make the layout into 2 pieces so i can use 2 of my boards?
also Ive found it difficult to print out his board layout to correct size, does anyone have another template or something to use ,or if not what is the usually turret spacings ?

here are some pics of parts  ive already got



Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #6 on: September 02, 2016, 09:27:46 am »
1) 5AR4

2) I prefer F&T over Sprague Atoms. I also use a lot of Illinois caps.

3) All of Hoffman's boards are 3.125" wide. You can split the layout onto two boards. But, for under $20 Hoffman will send you a predrilled board. That's a bargain IMO. When you print a pdf file, set the page scaling to NONE and it will print the correct size. You may need to go to Kinko's to get it printed unless you can tape a couple pieces of paper together and set up a custom page size for your printer. Like I said, Hoffman's $20 board is a bargain.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline HotBluePlates

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #7 on: September 02, 2016, 10:14:12 am »
here are some pics of parts  ive already got

A distraction, but 2 of the 3 tubes in the drawer look like they have "milky getters".  That means the vacuum is compromised (probably a crack in the glass base, next to a pin) and they're no longer usable.

Offline eleventeen

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #8 on: September 02, 2016, 10:20:13 am »
HBP good eye. The leftmost tube is dead. The middle one, probably.

Offline BetterOffShred

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #9 on: September 02, 2016, 03:30:34 pm »
Nice selection of stuff :)  Ive started amassing strange collections of components for this stuff too.   Is that SLO-50 clone in a Weber Chassis? I think Onetics makes one too maybe?  Those all look great!

I also say go for the amp.  Sure you can build a unit to do stuff, but Amps are always more fun in my opinion. 

-Brett

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #10 on: September 02, 2016, 05:56:48 pm »
yeah , I know about the tubes, I just grabbed everything together, to make the point that ive already got stuff for the build. 

I live in Australia, so i DONT KNOW WHAT kINKO'S IS,(WOOPS ACCIDENTLY PRESSED CAPS LOCK
 
c3 amps slo 50  is what i have.


i dont mind making my own board, helps me learn more about it, and since i have all these boards and turrets!

4) do you guys incorporate a bias test probe circuit? and what would the values of the 2 resistors be?
see pic below


5)  Transformer selection??   240v primaries, however there appears to be some much "voodoo" in iron, and im on a Hoffman site, however is mercury magnetic just all marketing, is iron all iron? any suggestions, again im not trying to make a replica , just a great sounding amp.

6)
negative feedback,  fixed / cathiode bias switch, raw tone stack mod,  tremolo  and reverb removal switch mods,  are any of these worth trying? 

Offline BetterOffShred

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #11 on: September 03, 2016, 09:20:47 am »
Cool stuff man.  I don't know as much about modding these amps as a lot of guys, but I put the feedback loop mod using a pot on my Bassman and it's awesome. You can do it to basically any fender or other amp with ease I'd imagine. Totally worth the time and pot.

-Brett

Offline eleventeen

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #12 on: September 03, 2016, 01:33:12 pm »
Usual values for those bias resistors is 1 ohm which causes the output to read out in millivolts which then translates directly into milliamps. Yes, exactly how you show it. Super clean work there. They need not be fat power resistors by the way. A tube pulling 100 ma = .1 amp (BIG) would cause those resistors to dissipate I*I*R = .1 * .1 * 1.0 = .01 watt.

Offline drew

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #13 on: September 03, 2016, 11:44:45 pm »
^ but make sure you use 1% tolerance resistors there.

Kinko's was a large chain of photocopy/print shops.  Federal Express bought them and stupidly jettisoned the name, but people continue to use it as a generic reference to copy shops.

The Mercury Magnetics transformers are a very expensive proposition for one-off builders.  I would use whatever Fender-type units you can acquire locally at reasonable cost.

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #14 on: September 04, 2016, 12:42:55 am »
so the hoffman transformers and heyboer  are good to use?

Offline drew

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #15 on: September 04, 2016, 04:16:02 pm »
^ yes, but check whether Doug stocks the power transformers that can be used with 240v power.

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #16 on: September 04, 2016, 10:23:15 pm »
another question, or 2!...

Ive only ever used 12" speakers in my builds, usually 2x12,   however the deluxe in pairs uses generally 2 x 10,,  is 2x12 ok, ?  or is there some magic with the 2 x10 config?


also  ive read that 5 x 16uf power cap config can cause bass farting!!   should i stick with this or up them to 22-25 uf caps?



Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #17 on: September 04, 2016, 10:45:33 pm »
The AB763 Deluxe Reverb amp was only supplied as a 1x12 combo amp. I'm sure a 2 speaker cab would sound good too.

I expect the difference between 16µF or 22µF filter caps would be not much, if any.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #18 on: September 05, 2016, 04:34:45 am »
never plyed a DR before, ive read that most people just use the Reverb Channel, If i Build the 1 channel Hoffman circuit, will it sound much different due to the removal of associate parts?  Ive read that just pulling v1 on a 2 channel can dramatically change it

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #19 on: September 05, 2016, 08:45:58 am »
If i Build the 1 channel Hoffman circuit, will it sound much different due to the removal of associate parts?  Ive read that just pulling v1 on a 2 channel can dramatically change it
It will sound the same. Pulling V1 on a "real" Fender AB763 amp will give a slight gain increase in the VIB channel. I would not call it a drastic change. That will not happen in a Hoffman AB763 amp.

The Hoffman AB763 is based on the real Fender AB763 but it's not identical. There is one major difference and several minor differences, all considered improvements. Compare the schematics of each to see the differences...

     http://el34world.com/Hoffman/files/Hoffman_AB763_2.pdf

     http://el34world.com/charts/Schematics/files/fender/Fender_Deluxe-Reverb-AB763-schematic.pdf

A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline PRR

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #20 on: September 05, 2016, 04:39:38 pm »
> is 2x12 ok, ?

Fender 2x12 is often a "Twin". Many models over many decades. The common factor for most open-back 2x12 speaker systems is enormous punch and throw (and weight). It's a big air-slapper.

Here's another viewpoint. One 12" cone in compact box has the face-area of a large acoustic guitar. One Ten is a small acoustic. Both are "right size". Eights and Sixes are ukulele-size sources even when whomped-up to e-guitar power. A Two Twelve is *bigger* than any acoustic, and sounds bigger. "A huge guitar." A 4-Ten or 8-Ten is even bigger, but the midrange is ratty as the multiple sources interact.

A Two-Twelve is an authoritative and much-loved guitar speaker.

Offline kagliostro

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #21 on: September 05, 2016, 05:07:50 pm »
In one of his books Kevin O'Connor reccomend as a good solution to use a 2 x XX cab with two mounting holes but only one speaker

Franco
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Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #22 on: September 05, 2016, 07:29:43 pm »
From what i can see and have read,
* is the whole tremolo section replaced the "bug" LDR version to Bias version which is apparently better?
* Due to availability 25uf/25v caps are replaced with more commonly available 22uf
* Bright switch and associated treble cap
* 1 ohm power tube pulldown resistors  thingys?
* Standby switch before first 2 power caps?
* faux ground tap thingy from heaters

« Last Edit: September 05, 2016, 10:20:59 pm by njkmonty »

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #23 on: September 06, 2016, 12:02:12 am »
another question i had was.

I was looking at some mods which could be resorted back to stock at anytime ,
could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???

1)  PPIMV
2) VVR
3) Presence Mod  (just before Phase Inverter
4) Tremolo "Disconnection switch"
5) 3 way toggle Negative Feedback switch , 2 seperate resistor values and middle position no connection?
6) fixed/ cathode bias switch
7) Not a mod, however every other amp i have built has 2 Fuses, 1 straight before power switch and the other just before power filter caps, why doesnt the DR have 2?

what i am trying to do is come up with exactly what i want then make a layout etc and post here for verification :)

Offline HotBluePlates

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #24 on: September 06, 2016, 09:48:02 am »
From what i can see and have read,
* is the whole tremolo section replaced the "bug" LDR version to Bias version which is apparently better?
...

... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???
...
4) Tremolo "Disconnection switch"

The Hoffman AB763 replaces the neon optoisolator "roach" as the injection point with varying the bias of the output tubes.  While an non-neon LDR can have a smooth sound, the neon light is an on/off affair with no varying intensity.  This also makes the resulting trem a choppier on/off affair.  That's "a sound" to be sure, but the rationale for the bias-vary trem is to get a smoother sweep from off to on.  So your choice on which version to use, depending on the sound you want.  "Better" as always, depends on what you want to hear.  I have trem pedals, and most offer the option of choppier trem as well as smooth trem; which sounds "best" varies depending on the effect you want to achieve in the song.

The original neon optoisolator of the bigger Fender amps is in parallel with a 50kΩ Intensity pot, which loads the amp's circuit.  A disconnect switch is sometimes suggested to "unload" the circuit by breaking the connection to that pot, which raises gain through the amp somewhat.  If you don't choose the neon optoisolator variant of the trem circuit, you will not need the disconnect switch (the bias vary doesn't load the circuit compared to stock, because it just sweeps the bias voltage).

From what i can see and have read,
* Due to availability 25uf/25v caps are replaced with more commonly available 22uf

Both are available; use whichever you have.  You won't hear any difference between the two values.

From what i can see and have read,
...
* Bright switch and associated treble cap

I don't like bright caps myself, so if I were to include it in an AB763 I would want it on a switch.  It can make the amp shrill when you're set for very low volume (2-3), but also has no effect when the Volume control is at maximum.  It seems most player like them when they have the amp up around midway, for just a little extra brightness.

From what i can see and have read,
...
* 1 ohm power tube pulldown resistors  thingys?

They are for measuring tube current, and are the blue resistors in your previous post.  Very handy so you don't have to measure tube current in more dangerous ways.

From what i can see and have read,
...
* Standby switch before first 2 power caps?

If you want a standby/mute function, that's a good place to put the switch.

From what i can see and have read,
...
* faux ground tap thingy from heaters

If your power transformer does not have a filament winding center-tap, then you will need the 100Ω resistor artificial center-tap to avoid buzzy hum.

Offline HotBluePlates

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #25 on: September 06, 2016, 09:48:32 am »
... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???

1)  PPIMV
2) VVR

I haven't tried these for this type of amp, so I defer to someone else.

... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???
3) Presence Mod  (just before Phase Inverter

Adding a Presence control?  Only you know if they're essential to how you use an amp.  On the only Fender I had with a Presence control, it always stayed on 0 so I removed it.

... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???
...
5) 3 way toggle Negative Feedback switch , 2 seperate resistor values and middle position no connection?

It can be handy to reduce negative feedback.  Instead of a switch with fixed settings (which you'd probably have to determine experimentally), I'd be more likely to use a ~5kΩ pot in series with the 820Ω series feedback resistor, with the pot wired as a rheostat.  That would allow you to sweep from stock feedback to essentially no-feedback and find whatever setting sounds best to you.

... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???
...
6) fixed/ cathode bias switch

This may be a nice feature, or not.  Some folks who have tried them found that unless the amp was at different bias points, the cathode bias setting didn't sound very different from the fixed bias setting.  As a result they usually left the switch in one position all the time.  I'll defer to others for comment...

... could someone tell me straight up for each which is worth doingon a Deluxe Reverb, and which is a waist of time???
...
7) Not a mod, however every other amp i have built has 2 Fuses, 1 straight before power switch and the other just before power filter caps, why doesnt the DR have 2?

History.  The stock Fender amps only used a mains fuse.  You can certainly add the HT fuse if you prefer.

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #26 on: September 06, 2016, 10:30:05 am »
Quote from: HotBluePlates
The original neon optoisolator of the bigger Fender amps is in parallel with a 50kΩ Intensity pot, which loads the amp's circuit.  A disconnect switch is sometimes suggested to "unload" the circuit by breaking the connection to that pot, which raises gain through the amp somewhat.  If you don't choose the neon optoisolator variant of the trem circuit, you will not need the disconnect switch (the bias vary doesn't load the circuit compared to stock, because it just sweeps the bias voltage).
Just to add to what HBP has already said... The whole purpose of the tremolo disconnect switch in a stock AB763 is to give a gain boost and it works very well. You can still get that same gain boost with the Hoffman AB763. Hoffman used a 47K resistor (R30) to simulate the loading of the original 50K INT pot. Without that resistor, the extra gain changes the typical clean character of the AB763 amp, so R30 is used to bring the gain back down to sound more like a clean AB763. You can use a switch to disconnect R30 from ground to have that gain boost available for solos, etc.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #27 on: September 09, 2016, 04:20:15 am »
IVe decided to build a 1 channel DR    but instead of asking everyone's thoughts on mods, that i would build it stock on a home made chassis try some mods
then go from there, then once complete i can transfer into a proper chassis.

I just noticed that the parts list for the 1 channel DR uses a 40w  / 6L6 configuration Mojo762    354-0-354
  isnt a DR a 6V6? 041316 transformer  330-0-330??

Im from Australia (240v)   and noticed that Hoffmanamps doesnt carry a 240v primaries for this project, will the following do ? (from Ce distribution)

and would this (see link below) be a suitable multi output transformer? 4Ω, 8Ω, 16Ω
https://www.cedist.com/products/transformer-hammond-output-upgrade-fender-20w-66k

https://www.cedist.com/products/transformer-hammond-240v-deluxe-deluxe-reverb

also is  my wiring diagram correct that i did on paint????


Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #28 on: September 09, 2016, 08:17:47 am »
Transformers and your drawing are fine.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #29 on: September 09, 2016, 09:38:27 am »
I just had a look at your website etc and was floored! wow you must have collected some knowledge re amps etc over the years!!

just curious what is your most favourite amp build / circuit  if there can be one?

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #30 on: September 09, 2016, 09:53:22 am »
The Vox AC-15 is my favorite.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Planobilly

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #31 on: September 09, 2016, 10:13:48 pm »
I just finished up with a Hoffman AB763 two channel build. I used a 290BX PT (120V 60Hz) without issue. If you use the Hammond transformer you will find the voltages on the original Fender schematic match very close.

The AB763 lends itself to many mods and I have have tried several. I changed all the caps to 715P series which I like the sound of but what I like may not be something you like.

I only tried a single 1m single pot style PPIMV which I did not like the sound of. I have some other dual gang pots on order to try.

The adjustable NFB was worth the effort to me.

None of any of the mods you mentioned are very time consuming to try and remove if you don't like them. I used 25uf electrolytic caps because I had them in stock. I think they were Sprague as I remember. I try to use F&T where I can and that is what I used on the filter caps.

I took the amp to my friends music store and tried out several speaker cabs. I liked the sound of several single 12" speakers we tried. I also like the Marshall quad cabinet I have.

The reverb sounds great on this amp. The tremolo also sounds good but different from the "roach". I own two other original Fender Deluxe Reverb amps and have always liked both of them. This Hoffman amp and the changes I made cause it to sound a bit cleaner than the originals.

I also ran some 5882 JJ tubes in the amp with the same transformers without issue. I am pretty sure doing that or running 6l6's will cause early failure of the PT. Mercury Magnetics makes some really high dollar transformers that will allow you to run both 6v6 or 6l6gt tubes and the output transformer has taps for both tubes. Pretty pricy stuff.

All in all the Hoffman schematic was a good basic schematic and a little easier to read the the original Fender schematic. I bought a turret board from Hoffman to save time which was worth it to me. I have a CNC mill and can drill the board with high precision but the programing time is not worth it to me.

These guys have been a good company to do business with and I feel comfortable recommending them to anyone.

Cheers,

Billy
Between fishing, flying, and fooling around with guitar amps, somehow 70 years got behind me. Shorter of breath and one day closer to death as the song goes.

Offline PRR

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #32 on: September 10, 2016, 10:49:29 am »
> ran some 5882...

5881 are more likely.

> that or running 6l6's will cause early failure of the PT.

5881 is a tough old-type 6L6 and will suck the same power.

With six(!) small bottles, we have 3.6A on a nominal 3.0A heater winding. However we also have the DCR number for that winding. I figure the extra loss and heat comes to less than 0.1 Watts. This does tend to "early failure" but that would still be many decades. Ample cooling would easily make up the difference.

> These guys have been a good company

FYI: "Hoffman Amplifiers" is Doug and two dogs.

Offline Planobilly

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #33 on: September 10, 2016, 04:22:44 pm »
Hi PRR,
Yes, 5881 tubes and 2 dogs...lol Any business run by two dogs and a guy is ok in my book!!...lol

I agree that there is some likely possibility of early failure of the transformer. The Hammond transformers don't cost too much, about $70 as I remember. The Mercury Magnetics solution to the issue was pushing $300. 

I built this amp just to experiment with so I expect to have some failures somewhere along the line.

I cranked up the gain on V1 and connected channel 1 to the reverb and tremolo. I also liked channel one the way it was so I may try to make that mod switchable. I sometimes curse my Mesa Boogie amps for being too complex and hard to work on so I don't want to fall into that trap.

I want to try to use a variable resistor on the NFB but don't have that figured out just yet.

At any rate this is a fun amp to play around with.

Oh, BTW, what are the doges name?

Cheers,

Billy
Between fishing, flying, and fooling around with guitar amps, somehow 70 years got behind me. Shorter of breath and one day closer to death as the song goes.

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #34 on: September 11, 2016, 04:46:00 am »
another quick questionnn..

re  cpacitors..

ive used sozo  caps before in my 18 watter   and 716  in my sloclone

now do i use the..

a    SoZo BlueMolded Vintage Capacitors™    https://www.cedist.com/products/capacitor-sozo-nextgen-blue-molded-vintage

b    Capacitor - 630V, Metal Film, Tubular       https://www.cedist.com/products/capacitor-630v-metal-film-tubular

c   Capacitor - 600V, 716P Series, Polypropylene   https://www.cedist.com/products/capacitor-600v-716p-series-polypropylene

d   Capacitor - Mallory, 630V, 150s, Axial Lead   https://www.cedist.com/products/capacitor-mallory-630v-150s-axial-lead

e   or other?

do i use a fancy brand?   do i use fancy brands only in signal path?

are the more expensive simply made with magical mojo juice????
 :dontknow: :dontknow: :dontknow: :dontknow:



Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #35 on: September 11, 2016, 07:06:01 am »
There is another important reason for choosing which cap to use... form factor. Will the preferred cap physically fit on the board? When you are designing a board layout you have the freedom to choose any cap you want and adjust the layout so the cap will actually fit the location where it will be used. This requires knowing the physical dimensions of the chosen cap.

I assume you may want to use a Hoffman board for your build? If so, you should know that board was designed to neatly accommodate the Xicon and Mallory 150 caps in Hoffman's store. Some of the caps you named are physically bigger than the Xicons and will look crowded and ugly on a Hoffman board. Some may not even fit at all. Look at this pic of an AB763 board that Hoffman actually built...


Here's another prime example of a densely populated Vox AC-15 board that was designed to accommodate Xicons and Mallory 150s. No way could you put Jupiters or Solens, or orange drops on this board...


A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #36 on: September 11, 2016, 07:38:39 am »
im making my own board so forgetting size , i was more curious about tone..   now i know the originals like most mass produced amps  used what ever was cheap,, i was curious if the sozos etc was superior tone wise or cheaper ones just as good?

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #37 on: September 11, 2016, 08:11:05 am »
Quote
im making my own board so forgetting size , i was more curious about tone..   
Physical size is still important and needs to be considered when making your own board. Cap tone is very subjective. 10 people may have 10 opinions about which cap has superior tone but what does that say to you? You still won't know which has a superior tone to your ears.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Planobilly

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #38 on: September 11, 2016, 11:09:44 am »
I think it would be difficult for anyone to truly describe the tone difference in different caps. Perhaps in some general terms, but likely not enough for you to make a decision. It is not a big job to change them in any event. Here are the two types of caps I installed in the AB763. As you can see, the board was designed for the smaller caps.  Using these larger caps makes it hard to get to resistors under them and creates other issues. Typically if I had in mind for this to be the final build I would lock them in place with silicone glue between the caps. I was not overly concerned with any of this because I built this amp to experiment with and for no other reason.

It is always good to have a clear idea of the final results of an amp build but it has been my experience that you will likely change some things no matter how much planning you do. The only way you will decide if sozo cap sound better to you is to try them. Higher price sometimes means higher quality but not always. A higher quality part often has no discernible effect on sound. The exact value of a component more often than not will not produce a change that you can hear. When some component changes the sound, the terms "good or bad" are more or less meaningless. Changes to the tone are purely subjective and totally dependent on the opinion of the listener.





BTW...I like the look of the heater wiring in sluckey's amp. I may remove mine and give that a try.
« Last Edit: September 11, 2016, 11:19:10 am by Planobilly »
Between fishing, flying, and fooling around with guitar amps, somehow 70 years got behind me. Shorter of breath and one day closer to death as the song goes.

Offline Willabe

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #39 on: September 11, 2016, 09:00:16 pm »
What Sluckey's saying about cap size is very important. And what he said about 10 different opinions I think is very true.

It depends on what kind of sound you want for the way and what guitar you play.

Long thread on how/if caps sound different, 4 pages, but a lot of good info;

http://el34world.com/Forum/index.php?topic=19534.0
« Last Edit: September 11, 2016, 09:11:39 pm by Willabe »

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #40 on: September 14, 2016, 03:35:07 am »
another question   ....

just to clarify , building either a  single or dual channel hoffman ab763
  i can either go the 22w or 40+w version 6v6  or 6l6
   where i purchase the corresponding output /power transformers and matching power tubes
is this correct?
 apart from different biasing
is there any different resistor values etc needed?  also which is preferred? ive never played through 6v6 tubes before only el84 and 6L6's
only fender I ever played through before is a new Fender Twin pro series

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #41 on: September 14, 2016, 04:25:02 am »
There are several components that are different between the various AB763 models. Look at Hoffman's schematic. You will see parts that are colored blue. These component values are different for the various models. Now look at Hoffman's BOM. The parts are listed for any model you may want.

I highly recommend reading all the links listed under the AB763 section on the Library of Information page.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #42 on: September 14, 2016, 05:33:41 am »
ive printed out heaps, even a lot of pdfs from your stuff and taking it all in!

i saw the blue parts variances , however only just discovered this

http://el34world.com/Hoffman/files/Hoffman_AB763_2_BOM.pdf   which was what i needed!

on your
 TWEED DELUXE REVERB designed by Steve Luckey. (2006)
Schematic is based on Fender Deluxe Reverb AB763 circuit.

http://sluckeyamps.com/tdr/tdr.pdf

i see you have incorporated a 100k log master pot,  how did this go? i like also that you have voltages aswell . Ive learnt a little more of this circuit  since and am looking at using some sozo's on the signal path only, and looking at modifying a layout to accomodate them.


Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #43 on: September 14, 2016, 06:05:19 am »
That MV allows you to crank up the preamp gain for some grit. It was really a fix for omitting a 47K resistor on the board.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline njkmonty

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #44 on: September 15, 2016, 07:30:12 am »
Hi Slucky , I feel like im getting on top of the info , and was wondering if i could pick your brain a little more regarding your builds?

I think Im going to stick with the Single Channel Hoffman ab763 using the following..

6V6

Transformer - Hammond, 240V for Deluxe, Deluxe Reverb    - Hammond P-T290BX  330v-0-330

Transformer - Hammond, Output replacement for Fender, 20W 6.6kΩ   - Hammond  1750H

I was wondering if you could share some of your thoughts about different values I found on your Schematic?

http://sluckeyamps.com/tdr/tdr.pdf



*) Tonestack C4 .022uf, Did you find this a better value to use than .047uf?   
*) C11 Reverb Coupling Cap, .0033uf is used where others use .0022uf?  again small potatoes? or just what you had or your personal taste?
*) Power Resistors you use are 1Watt, Is that ok?  if so I don't need to buy any more, however Hoffman schematics have 3W resistors used.
*) c23 47uf Cap between Diode and Bias Pot, I haven't seen this on other schematics
*) C16-17 you use 0.047uf caps where others have 0.1uf.
*) 220K 1W resistor next to C18 (20uf)

These are some small variances I noticed, and just wondering if , its because thats just what you had a the time? or you found them improved the circuit or other?  as if you feel they benefit, then i was going to incorporate them in my build

Offline sluckey

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Re: Should I build a Hoffman ab763 Deluxe reverb? help advice needed
« Reply #45 on: September 15, 2016, 08:39:31 am »
Quote
*) Tonestack C4 .022uf, Did you find this a better value to use than .047uf?
.022µF was used in the Super Reverb. Don't remember why I decided to use it.
   
Quote
*) C11 Reverb Coupling Cap, .0033uf is used where others use .0022uf?  again small potatoes? or just what you had or your personal taste?
That is the value that original Fender used.

Quote
*) Power Resistors you use are 1Watt, Is that ok?  if so I don't need to buy any more, however Hoffman schematics have 3W resistors used.
The original DR used 1 watt. If I had to buy resistors I would use 3 watt metal oxide.

Quote
*) c23 47uf Cap between Diode and Bias Pot, I haven't seen this on other schematics
This was my idea borrowed from Sunn. The extra cap provides better filtering for the bias voltage.
 
Quote
*) C16-17 you use 0.047uf caps where others have 0.1uf.
My choice. The original DR used .1µF. I used the smaller values to eliminate some flubby bass.
 
Quote
*) 220K 1W resistor next to C18 (20uf)
My choice. The resistor will drain/bleed the cap charge when you turn the amp off.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

 


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