By "wiring errors", do you mean that they lack your 'Galactic Grounding' scheme? Or are there others?
I found that Hoffman also offer a 'Deluxe Reverb' kit---seems to be much better because they allow you to CHOOSE your components.
Hi Guys
Hoffman does not post a layout on their site, or if they do it is difficult to find. In any case, if it follows Fender's layout then it is compromised.
Galactic Grounding fixes 90% of problems with these old amps as it inherently eliminates the use of multi-section caps. Axial-lead filter caps are also a bad choice as their quality is poor compared to an equal-rated radial-lead cap regardless of price. Screen resistors are the wrong value. Carbon resistors are unstable and noisy. Being able to choose your parts is great except when the choices are limited to "vintage" technologies... but to each his own.
"Better" parts are not necessarily more expensive and they are rarely the most expensive. The latter are usually voodoo parts not worth one-hundredth of their asking price.
You are going to put in a lot of hours building your amp. You can use that time to put in a good part or a bad part; to wire it correctly or according to a production convenience; or just follow instructions to get it working and later change things to make it better. The DR topology has all kinds of potential to be a great amp and you will like end up modifying later anyway..
Have fun
Hoffman does not post a layout on their site, or if they do it is difficult to find. In any case, if it follows Fender's layout then it is compromised.
Galactic Grounding fixes 90% of problems with these old amps as it inherently eliminates the use of multi-section caps. Axial-lead filter caps are also a bad choice as their quality is poor compared to an equal-rated radial-lead cap regardless of price. Screen resistors are the wrong value. Carbon resistors are unstable and noisy. Being able to choose your parts is great except when the choices are limited to "vintage" technologies... but to each his own.
"Better" parts are not necessarily more expensive and they are rarely the most expensive. The latter are usually voodoo parts not worth one-hundredth of their asking price.
You are going to put in a lot of hours building your amp. You can use that time to put in a good part or a bad part; to wire it correctly or according to a production convenience; or just follow instructions to get it working and later change things to make it better. The DR topology has all kinds of potential to be a great amp and you will like end up modifying later anyway..
Have fun
Hi,
I just today finished the basic build for a Fender Deluxe Reverb. I built the amp from scratch and used Fender's basic design idea with several mods. There is more or less zero noise until you turn the amp almost wide open on the second channel. I did not ground the amp like Fender does. Everything is isolated from the chassis and I installed buss bars. I built my own chassis which was a pain in the butt.
I looked at Hoffman's schematics and layout. I looked at Mojo's stuff also.
I used Hoffman's tremolo circuit design and not a "roach" like Fender does. I am not sure which I like best yet.
I got a few parts like boards and turrets from Hoffman. I don't really like either one. The turrets were to small and the board was sensitive to flux remover. I am not sure who I would try next. There was nothing actually wrong with Hoffman turrets or boards. They just did not fit my needs so well. Doug Hoffman is a good guy to do business with and he is on top of things. He has a ton of stuff to sell and a ton of useful information on his web site...perhaps a bit hard to find your way around in.
I used metal film resistors. There are no can cap in a Fender Deluxe Reverb. I used F&T axial filter caps in the power supply without issue and there is very little ripple. Other caps were Cornell Dubilier and the cathode cap were Sprague.One could use radial caps but they just require a different board layout.The pots were PEC which cost too much for what you get at $10 each. Really good pots but expensive. I used rg179 shielded wire to the grids and for the master volume control.
All you will really get with anyone's kit is a schematic and a layout diagram. Of course the parts also.
If I was going to buy a kit I would not buy everything from one kit maker. Every kit maker is going to sell the parts they like and some are good and some not so good.
Unless you have very good skills at making things like chassis or cabinets, it is better to buy them.
The AB763 is not the easiest amp to build but very doable. Once you get it figured out you know how many Fender amps are built. Deluxe Reverb, Super Reverb, Twin Reverb, Vibrolux all are almost the same. The difference is mostly transformers and output tubes.
If you look at the schematics from the kit makers you will find they all are just copies of the original Fender AB763 schematic with a few mods.
The type of resistors you use should be based on what you like in sound and what you are willing to put up with in reliability and if you are trying to create a vintage look. There is no right or wrong, just what you like.
Many great recordings have been made with a original Fender Deluxe Reverb with all the technical issues it has.There are lots of mods for this amp and free tone stack software to give you ideas of what changes to make.
It is not really a "bedroom" amp and you will most likely need to add a master volume or power scaling which Struth can help you with if you want to play it at home.
All of these kit makers are pretty easy to deal with and none of them are going to hold you hand to make the amp. Support is more or less there for the asking via a lot of nice people are on the various forums.
The cost from kit to kit should not change to much IF you are comparing the SAME parts. Questions to ask...who makes the transformers? who makes the speakers and what model? If the kit maker will not answer the questions I would not buy from them. I have seen some Webber cabinets lately that were pretty good, also some Webber speakers that I like the sound of, but that is just me.
I hope some of this is helpful. I know I stressed out a bit digging up all the info...lol
Final word, I like the sound of Fender Deluxe Reverb style amps. I think you
most likely be happy with the results and the good news is you can modify things to better suit if you don't like everything.
Cheers,
Billy
EDIT: BTW, I would be glad to help you any way I can with your project...just drop me a line.
I just today finished the basic build for a Fender Deluxe Reverb. I built the amp from scratch and used Fender's basic design idea with several mods. There is more or less zero noise until you turn the amp almost wide open on the second channel. I did not ground the amp like Fender does. Everything is isolated from the chassis and I installed buss bars. I built my own chassis which was a pain in the butt.
I looked at Hoffman's schematics and layout. I looked at Mojo's stuff also.
I used Hoffman's tremolo circuit design and not a "roach" like Fender does. I am not sure which I like best yet.
I got a few parts like boards and turrets from Hoffman. I don't really like either one. The turrets were to small and the board was sensitive to flux remover. I am not sure who I would try next. There was nothing actually wrong with Hoffman turrets or boards. They just did not fit my needs so well. Doug Hoffman is a good guy to do business with and he is on top of things. He has a ton of stuff to sell and a ton of useful information on his web site...perhaps a bit hard to find your way around in.
I used metal film resistors. There are no can cap in a Fender Deluxe Reverb. I used F&T axial filter caps in the power supply without issue and there is very little ripple. Other caps were Cornell Dubilier and the cathode cap were Sprague.One could use radial caps but they just require a different board layout.The pots were PEC which cost too much for what you get at $10 each. Really good pots but expensive. I used rg179 shielded wire to the grids and for the master volume control.
All you will really get with anyone's kit is a schematic and a layout diagram. Of course the parts also.
If I was going to buy a kit I would not buy everything from one kit maker. Every kit maker is going to sell the parts they like and some are good and some not so good.
Unless you have very good skills at making things like chassis or cabinets, it is better to buy them.
The AB763 is not the easiest amp to build but very doable. Once you get it figured out you know how many Fender amps are built. Deluxe Reverb, Super Reverb, Twin Reverb, Vibrolux all are almost the same. The difference is mostly transformers and output tubes.
If you look at the schematics from the kit makers you will find they all are just copies of the original Fender AB763 schematic with a few mods.
The type of resistors you use should be based on what you like in sound and what you are willing to put up with in reliability and if you are trying to create a vintage look. There is no right or wrong, just what you like.
Many great recordings have been made with a original Fender Deluxe Reverb with all the technical issues it has.There are lots of mods for this amp and free tone stack software to give you ideas of what changes to make.
It is not really a "bedroom" amp and you will most likely need to add a master volume or power scaling which Struth can help you with if you want to play it at home.
All of these kit makers are pretty easy to deal with and none of them are going to hold you hand to make the amp. Support is more or less there for the asking via a lot of nice people are on the various forums.
The cost from kit to kit should not change to much IF you are comparing the SAME parts. Questions to ask...who makes the transformers? who makes the speakers and what model? If the kit maker will not answer the questions I would not buy from them. I have seen some Webber cabinets lately that were pretty good, also some Webber speakers that I like the sound of, but that is just me.
I hope some of this is helpful. I know I stressed out a bit digging up all the info...lol
Final word, I like the sound of Fender Deluxe Reverb style amps. I think you
most likely be happy with the results and the good news is you can modify things to better suit if you don't like everything.
Cheers,
Billy
EDIT: BTW, I would be glad to help you any way I can with your project...just drop me a line.
Last edited:
Planobilly: THANKS for your kind reply! I think the Hoffman offerings give the most flexibility; you can buy only what YOU select. I'm thinking that the metal film resistors, orange drop caps, and Switchcraft jacks would be best. Still deciding on tubes, tank, and transformers. I agree that the tubes and OP Xfrmr make the most difference, and I like the bias-modulation scheme for tremolo rather than the opto-isolator. Which output transformer did you use? I'm leaning towards the Heyboer--it's got taps for 4-8-16 Ω. Maybe Ruby tubes? Has anyone tried the 'Power Scaling' mod? It ain't exactly cheap at $120 or so. I think I'll build a separate head, as I've already got several speaker cabinets to try (1x Celestion 12", 1x JBL D130, 1x Peavy 12"). The only cabinet I've found so far is the Mojotone one at ~$220. Others??
Hi dotneck335,
I used Cliff jacks because I wanted to isolate the jacks from the chassis. I used all JJ tubes because I have a super good vendor who provides me with very high quality tubes matched to my requirements. I used Hammond transformers because I got very good pricing from Hammond. The output transformer has 4,8, and 16 ohm taps.
There was a small issue with the power transformer because it did not have a center tap for the heater voltage which required placing two resistors to ground in parallel. I used 68 ohm resistors but anything for 47 ohms to 100 ohms would likely work. There exist better transformers than Hammond produces...well...at a price. Nothing wrong with Heyboer.
I also built this as a head because I have several speaker cabinets. I assume Webber has a cabinet...not really sure...the last I got from them was for a Marshall JTM 45 build and was pretty well made.
One of the issues you get into ordering parts is the cost of shipping. I ordered a few things from Hoffman that I would normally order from my normal suppliers for that reason. The service from Hoffman was very good as he processed the orders the same day and I received them very quickly.
I have not used London Power's MOSFET power scaling products as of yet but my research into the issue has lead me to believe they work as advertized. I actually have in mind to give it a try. I was not put off by the $120 cost of the circuit but I thought the books were a bit pricy. The books may be well worth the money...I just don't know.
The amp I am building is purely experimental and as such has been built in a way that lends itself to being easy to make changes to. All the panels on the chassis are removeable for example. There is an extra octal tube socket I put in the amp so I could uses dual rectifiers or use 4 output tubes and a solid state rectifier. I left plenty of space to put in a larger power transformer.
I wanted to learn for myself what works well and what does not. I want to make some recordings when I get it running well and then I want to change all the resistors to carbon comp and re- record them compare the two.
Here is a photo. The wiring has been put in for easy removal, not to look good.
Best of luck on the build,
Billy
I used Cliff jacks because I wanted to isolate the jacks from the chassis. I used all JJ tubes because I have a super good vendor who provides me with very high quality tubes matched to my requirements. I used Hammond transformers because I got very good pricing from Hammond. The output transformer has 4,8, and 16 ohm taps.
There was a small issue with the power transformer because it did not have a center tap for the heater voltage which required placing two resistors to ground in parallel. I used 68 ohm resistors but anything for 47 ohms to 100 ohms would likely work. There exist better transformers than Hammond produces...well...at a price. Nothing wrong with Heyboer.
I also built this as a head because I have several speaker cabinets. I assume Webber has a cabinet...not really sure...the last I got from them was for a Marshall JTM 45 build and was pretty well made.
One of the issues you get into ordering parts is the cost of shipping. I ordered a few things from Hoffman that I would normally order from my normal suppliers for that reason. The service from Hoffman was very good as he processed the orders the same day and I received them very quickly.
I have not used London Power's MOSFET power scaling products as of yet but my research into the issue has lead me to believe they work as advertized. I actually have in mind to give it a try. I was not put off by the $120 cost of the circuit but I thought the books were a bit pricy. The books may be well worth the money...I just don't know.
The amp I am building is purely experimental and as such has been built in a way that lends itself to being easy to make changes to. All the panels on the chassis are removeable for example. There is an extra octal tube socket I put in the amp so I could uses dual rectifiers or use 4 output tubes and a solid state rectifier. I left plenty of space to put in a larger power transformer.
I wanted to learn for myself what works well and what does not. I want to make some recordings when I get it running well and then I want to change all the resistors to carbon comp and re- record them compare the two.
Here is a photo. The wiring has been put in for easy removal, not to look good.
Best of luck on the build,
Billy
Looks good to me! I notice an unwired pot on the far right---is that for a future master volume? I am not sure that the difference between carbon comp and metal film resistors would be audible, but ???? I am thinking that the choice of capacitors would make a bigger difference. Now I am considering a 'bigger iron' output transformer that has 2-4-8 Ω taps and will accommodate 2 x 6L6 output tubes (should I want to try that later).
After looking at the power supply schematic, I am wanting to put a MUCH larger choke in (20H, 100ma), and take the power tube B+ from AFTER this choke rather than before it---I believe this would reduce the amount of power supply ripple on the signal system by quite a bit. Do you know how much current is drawn from the supply on a Deluxe Reverb? I notice that Hoffman offer two different transformers--one at 330 VAC, 120mA; and the other at 384 VAC, 75mA. My concern is: is the 100mA rating on my bigger choke enough?
Do you have a link to the pots you used? The Alpha pots are only $2.16 each, but I don't know if they are top quality.
Looking forward to hearing your recording results with your new build!!
After looking at the power supply schematic, I am wanting to put a MUCH larger choke in (20H, 100ma), and take the power tube B+ from AFTER this choke rather than before it---I believe this would reduce the amount of power supply ripple on the signal system by quite a bit. Do you know how much current is drawn from the supply on a Deluxe Reverb? I notice that Hoffman offer two different transformers--one at 330 VAC, 120mA; and the other at 384 VAC, 75mA. My concern is: is the 100mA rating on my bigger choke enough?
Do you have a link to the pots you used? The Alpha pots are only $2.16 each, but I don't know if they are top quality.
Looking forward to hearing your recording results with your new build!!
Link to the pots. https://www.tubesandmore.com/
The last pot in the photo is for a post phase inverter master volume control. I may not like it and buy power scaling from London Power.
I will let you know about the resistor issue when I devise a meaningful test. May be a while.
Mercury Magnetics makes a output transformer that has two impedance taps so you can use 6v6 or 6l6gt tubes. I think all the standard power transformers are a little under powered for the HT amps value and on the primary for that matter. There is no real answer to that issue without spending a good bit of money. I have not measured the current draw as of yet. If you can get a higher rated choke, I would do that. I have to think about the effect of using a 20 henry choke...something is tapping me on the shoulder but I don't remember what...don't ever get old...lol
If you use the Hoffman layout for a bright switch and Mid pot let me know. I will guide you through some things that were left out on that layout. The Deluxe layout is correct but does not have the bright switch and Mid pot.
Hoffman has tried to combine several amp layouts on one layout diagram and it is a bit confusing.
I also think the screen resistor may be incorrect like Struth said. It works but I am looking into the issue.
Cheers,
Billy
The last pot in the photo is for a post phase inverter master volume control. I may not like it and buy power scaling from London Power.
I will let you know about the resistor issue when I devise a meaningful test. May be a while.
Mercury Magnetics makes a output transformer that has two impedance taps so you can use 6v6 or 6l6gt tubes. I think all the standard power transformers are a little under powered for the HT amps value and on the primary for that matter. There is no real answer to that issue without spending a good bit of money. I have not measured the current draw as of yet. If you can get a higher rated choke, I would do that. I have to think about the effect of using a 20 henry choke...something is tapping me on the shoulder but I don't remember what...don't ever get old...lol
If you use the Hoffman layout for a bright switch and Mid pot let me know. I will guide you through some things that were left out on that layout. The Deluxe layout is correct but does not have the bright switch and Mid pot.
Hoffman has tried to combine several amp layouts on one layout diagram and it is a bit confusing.
I also think the screen resistor may be incorrect like Struth said. It works but I am looking into the issue.
Cheers,
Billy
I added a post PI MV to my '71 DR. I like it a lot. I used the type where it replaces the grid (leak) resistors. Included "wiper safety" resistors. Used shielded cable to and from it with the (insulted) shield carrying the bias voltage. The only trick is to turn the bass down to 2-3 when cranking the preamp. Just like you would have to do if there were no MV.
Can you provide specifics, such as M.V. pot value and exact placement in the circuit? And what are "wiper safety resistors"?
Here is a link that will give you a lot of what you need to know.
https://robrobinette.com/The_Trainwreck_Pages.htm
Billy
https://robrobinette.com/The_Trainwreck_Pages.htm
Billy
Dotneck335
If you look at the Trainwreck Pages down around page 32 and take a close look at the type two master volume control, this may be the best solution to try first.
I don't know what you had in mind for your negative feedback circuit but I am placing a switch to remove all NFB or switch the current 820 ohm feedback resistor with another value to reduce NFB.
The "wiper safety resistors" add a backup path for the bias if the pot fails to keep from burning up the output tubes.
Also you more or less have to use shielded cable and for sure if you place the dual gang pot on the far end by the power transformer.
Cheers,
Billy
If you look at the Trainwreck Pages down around page 32 and take a close look at the type two master volume control, this may be the best solution to try first.
I don't know what you had in mind for your negative feedback circuit but I am placing a switch to remove all NFB or switch the current 820 ohm feedback resistor with another value to reduce NFB.
The "wiper safety resistors" add a backup path for the bias if the pot fails to keep from burning up the output tubes.
Also you more or less have to use shielded cable and for sure if you place the dual gang pot on the far end by the power transformer.
Cheers,
Billy
Wow-those links are fantastic!! Thanks!!
The Type-2 Master Volume seems the best way to go--do the grid stopper resistors (1500Ω) remain as they were?
I like the negative feedback switch as well as the 'raw' switch. All good things to try.
Checked out the Mercury Magnetics transformers--they appear to be good, but whoa!--they sure are expensive!! Same thing with your $10 Precision Electronics pots-- very good but hard to justify $100 just on pots!!! Perhaps there is something in between those and the $2 Alpha Pots.
I'm thinking that shielded wire might be a good thing all way around. Might eliminate the possibility of the dreaded 'CBS parasitic oscillation'.
The Type-2 Master Volume seems the best way to go--do the grid stopper resistors (1500Ω) remain as they were?
I like the negative feedback switch as well as the 'raw' switch. All good things to try.
Checked out the Mercury Magnetics transformers--they appear to be good, but whoa!--they sure are expensive!! Same thing with your $10 Precision Electronics pots-- very good but hard to justify $100 just on pots!!! Perhaps there is something in between those and the $2 Alpha Pots.
I'm thinking that shielded wire might be a good thing all way around. Might eliminate the possibility of the dreaded 'CBS parasitic oscillation'.
Hey dotneck335
I more or less finished up with the AB763 build. I added a single pot master volume which I may change later...not sure how the double gang pot system will sound. I connected the reverb and tremolo circuit to work on channel one, so now I can also externally jumper the two channels. I also increased the gain on channel one. I have a few small details left to do but I am pretty happy with the sound so far.
I have in mind to try some 5881 tubes in the amp and see if I can make that work with the current power transformer. I only assume I can bias them with the 50V negative supply.
It has been a fun project. The next project will be an EL84 based amp.
BTW, Send me a PM and I will send you my phone number if you need it.
Cheers,
Billy
I more or less finished up with the AB763 build. I added a single pot master volume which I may change later...not sure how the double gang pot system will sound. I connected the reverb and tremolo circuit to work on channel one, so now I can also externally jumper the two channels. I also increased the gain on channel one. I have a few small details left to do but I am pretty happy with the sound so far.
I have in mind to try some 5881 tubes in the amp and see if I can make that work with the current power transformer. I only assume I can bias them with the 50V negative supply.
It has been a fun project. The next project will be an EL84 based amp.
BTW, Send me a PM and I will send you my phone number if you need it.
Cheers,
Billy
Looking forward to your thoughts on the master control. I agree with you that, if you are using capacitors on both sides of the dual-ganged pot, they should be doubled in value to equal the original circuit's response.
I still think the 6V6s are the sweetest of all the power amp tubes, and, unless you NEED more volume, that they are the best.
I am going to have to back-burner my AB763 build for a little bit, due to other pressing needs, but I will post when I get back to it.
I still think the 6V6s are the sweetest of all the power amp tubes, and, unless you NEED more volume, that they are the best.
I am going to have to back-burner my AB763 build for a little bit, due to other pressing needs, but I will post when I get back to it.
Great discussion, guys! Just wanted to point you to AmpMaker's kits, and particularly his variable voltage control -- a much more reasonably priced alternative to Hoffmans' power scaling kit: Amp Maker: Guitar amp kits and parts :: Guitar amp kits :: VCB/VVR kit for cathode-biased amplifiers. Let's you adjust B+ from max down to about 25V. Can be applied to the whole amp (minus heaters) or just the power stage (might lame tube reverb it's tubes aren't excluded). He's in Britain, but the current exchange rate makes the pricing reasonable enough to cover the extra shipping cost. About $25 at today's rate for the simple MOSFET-based VCB kit.
I ordered his DoubleSix kit because it essentially matched the amp I'd spent a month or two to design myself (James stack with Mid scoop control, parallel 6V6s). Can also run 6L6s or a single EL34 or KT88. Placed the order on Friday evening, got the kit Tuesday morning in Virginia. Very complete kit with excellent instructions. Designed to be very easy to mod, with extra holes in the chassis and free turrets on the board. His other kits look good, too. Check 'em out: Amp Maker: Guitar amp kits and parts.
I ordered his DoubleSix kit because it essentially matched the amp I'd spent a month or two to design myself (James stack with Mid scoop control, parallel 6V6s). Can also run 6L6s or a single EL34 or KT88. Placed the order on Friday evening, got the kit Tuesday morning in Virginia. Very complete kit with excellent instructions. Designed to be very easy to mod, with extra holes in the chassis and free turrets on the board. His other kits look good, too. Check 'em out: Amp Maker: Guitar amp kits and parts.
It does seem to make more sense to put a pot before the PI (between the .001uF coupling capacitor and the 1M grid-leak resistor). This would eliminate the tracking problems of a dual-ganged pot in the output tube biasing circuit. I also think the MOSFET-adjust to the output tubes' B+ power supply would make sense--similar to the Mercury Magnetics idea of a lower B+ power transformer, but adjustable. If anyone has the resources to compare these two approaches to master-volume control, I'd LOVE to hear the results!! Has anyone seen the circuit for the London Power-Scaling method? I don't know how he is doing it.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.