Awhile back I bought a Plush super 450 4x10 combo in an auction for what to me felt like a good price for a Fender replica. The thing was pretty thrashed and I only got to play one show with it before it burnt up some resistors on the power tubes. Upon opening it up I decided to take on the journey of redoing the whole amp. Tube sockets falling out, completely seized pots, dusty floating components, other components with questionable life spans left in them.
Fast forward a few months a good buddy of mine invites me over to the studio he works at for a jam, and just so happens the owner has a Dumble (can’t remember the exact number but somewhere in the #140s) and a few Dumble clones. I fell in love with the sound and decided that’s what I want to do with this shell of a Plush I have sitting in my shop.
Anyways as a newcomer to the forum I’d like to share my idea and later on start a thread following my journey with the build. My idea is that the transformers should be good candidates, I should have most if not all of the components in my workshop, g10 boards I can machine at work. I don’t plan on this being an exact clone build as I don’t see the switching relays as an important part for me and if I can keep this build down to what I have in stock then I’m happy with it.
Plush as a Dumble style donor build
Moderators: pompeiisneaks, Colossal
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doomedwizard
- Posts: 5
- Joined: Tue Oct 10, 2023 12:25 am
- Location: Austin, TX
Re: Plush as a Dumble style donor build
The Plush Super 450 Combo amp was introduced in 1971 and then died out in 1973 (Along with Plush as a company).
Plush built 3-4 different variations on this model starting out with a tag board version, culminating in the last variation which uses a mixture of terminal strips and PCB's. Different variations existed between the 1st generation and last generation Super 450's.
The circuit is not too far removed from the Fender AB763 though the reverb and vibrato circuitry are notably different. You are correct, the iron is actually of exceptional quality and was made by Northlake Engineering and was based on the Woodward Schumacher Fender iron but Northlake was known for their high quality standards being primarily a military and industrial supplier. Saul Marantz and a team of his engineers actually reversed engineered iron from a blackface Fender Twin and made some tweaks and specification changes on the magnet wire, the lamination pack and the turns ratios. The chassis is stamped steel (like a Fender) and quite massive...considerably larger than a Fender Twin chassis (and heavier). It has no side gussets...it is open on either end but heavy enough gauge that it doesn't matter. Of course, it is also drastically larger than a Dumble ODS chassis. So no shortage of space and the iron is much further away from the sensitive preamp circuitry...so that's good.
That said, steel versus aluminum for a chassis in a high gain Dumble ODS...definitely less than desirable. Can you build an ODS inside this chassis? Of course but getting the S/N ratio as optimal as the aluminum chassis will be a bit of a challenge. That said, you can easily build an ODS inside the 450 chassis and get a great sounding amp...the noise floor will be a bit worse.
Having built other circuits inside this large Plush chassis many times, I know exactly how this works out for the ODS circuit (Or Boogie Mark II or Marshall JCM800, etc.). Great caution in grounding scheme and layout/lead dress matter. Nothing new here...high gain circuits in a steel chassis can be tricky to contend with.
just so you know, the Super 450 chassis (And the similar Super 550) chassis are essentially the same as the 3K and 4K series Plush heads but with the face panel bend the opposite since its designed to hang from a combo cabinet whereas the head chassis is designed to sit on the bottom of a head cabinet (Like a Marshall or Sunn or similarly constructed amp).
You could also, quite easily affix the Plush PT, Choke and OT onto a readily available aftermarket ODS chassis which might be the path of least resistance requiring a lot less hole punching/drilling since you can get prefabricated tag boards and/or PCB's for the ODS aftermarket chassis. I do prefer the ODS's be built in aluminum...just solves problems of having a ferrous chassis. I have built Dumble clones using the Plush iron with superlative results...often I prefer the Plush (Northlake) iron to the standard Fender/Woodward Schumacher iron in old Fender amps and have many times replaced dead stock Fender iron with Plush iron and have always been happy with how well it works and performs. Plush amps are often listed for sale for high prices but rarely sell for very much...and that makes them great donor amps for high quality iron to be used elsewhere.
Also, another nicety is the Plush OT is in the Super 450 they generally are a multi-tap secondary...4 ohm/8 ohm which is much more useful than the single 4 ohm tap of your typical 60's or 70's Fender OT.
Plush built 3-4 different variations on this model starting out with a tag board version, culminating in the last variation which uses a mixture of terminal strips and PCB's. Different variations existed between the 1st generation and last generation Super 450's.
The circuit is not too far removed from the Fender AB763 though the reverb and vibrato circuitry are notably different. You are correct, the iron is actually of exceptional quality and was made by Northlake Engineering and was based on the Woodward Schumacher Fender iron but Northlake was known for their high quality standards being primarily a military and industrial supplier. Saul Marantz and a team of his engineers actually reversed engineered iron from a blackface Fender Twin and made some tweaks and specification changes on the magnet wire, the lamination pack and the turns ratios. The chassis is stamped steel (like a Fender) and quite massive...considerably larger than a Fender Twin chassis (and heavier). It has no side gussets...it is open on either end but heavy enough gauge that it doesn't matter. Of course, it is also drastically larger than a Dumble ODS chassis. So no shortage of space and the iron is much further away from the sensitive preamp circuitry...so that's good.
That said, steel versus aluminum for a chassis in a high gain Dumble ODS...definitely less than desirable. Can you build an ODS inside this chassis? Of course but getting the S/N ratio as optimal as the aluminum chassis will be a bit of a challenge. That said, you can easily build an ODS inside the 450 chassis and get a great sounding amp...the noise floor will be a bit worse.
Having built other circuits inside this large Plush chassis many times, I know exactly how this works out for the ODS circuit (Or Boogie Mark II or Marshall JCM800, etc.). Great caution in grounding scheme and layout/lead dress matter. Nothing new here...high gain circuits in a steel chassis can be tricky to contend with.
just so you know, the Super 450 chassis (And the similar Super 550) chassis are essentially the same as the 3K and 4K series Plush heads but with the face panel bend the opposite since its designed to hang from a combo cabinet whereas the head chassis is designed to sit on the bottom of a head cabinet (Like a Marshall or Sunn or similarly constructed amp).
You could also, quite easily affix the Plush PT, Choke and OT onto a readily available aftermarket ODS chassis which might be the path of least resistance requiring a lot less hole punching/drilling since you can get prefabricated tag boards and/or PCB's for the ODS aftermarket chassis. I do prefer the ODS's be built in aluminum...just solves problems of having a ferrous chassis. I have built Dumble clones using the Plush iron with superlative results...often I prefer the Plush (Northlake) iron to the standard Fender/Woodward Schumacher iron in old Fender amps and have many times replaced dead stock Fender iron with Plush iron and have always been happy with how well it works and performs. Plush amps are often listed for sale for high prices but rarely sell for very much...and that makes them great donor amps for high quality iron to be used elsewhere.
Also, another nicety is the Plush OT is in the Super 450 they generally are a multi-tap secondary...4 ohm/8 ohm which is much more useful than the single 4 ohm tap of your typical 60's or 70's Fender OT.
Re: Plush as a Dumble style donor build
I agree on the Alu chassis, it sounds different than a steel chassis, more hollow. The steel chassis' sound nice too though, but not like an ODS
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doomedwizard
- Posts: 5
- Joined: Tue Oct 10, 2023 12:25 am
- Location: Austin, TX
Re: Plush as a Dumble style donor build
This is more info on Plush amps that I’ve seen over all the other forums and groups I’ve asked on. Any chance you have the schematics for the 450? Specifically the reverb and trem circuit? I crudely traced the circuit but the part numbers on the transistors seemed to be rubbed off. My initial plan was to build the amp back up exactly like a twin with tube driven trem and reverb. I don’t really use either on an amp so I don’t mind leaving them out on this build.GPD wrote: ↑Mon Oct 16, 2023 11:36 pm The circuit is not too far removed from the Fender AB763 though the reverb and vibrato circuitry are notably different. You are correct, the iron is actually of exceptional quality and was made by Northlake Engineering and was based on the Woodward Schumacher Fender iron but Northlake was known for their high quality standards being primarily a military and industrial supplier. Saul Marantz and a team of his engineers actually reversed engineered iron from a blackface Fender Twin and made some tweaks and specification changes on the magnet wire, the lamination pack and the turns ratios. The chassis is stamped steel (like a Fender) and quite massive...considerably larger than a Fender Twin chassis (and heavier).
As for the chassis I’m gonna stick with what I got. It’s cheaper and simpler at the moment. Besides my plan wasn’t to clone a Dumble exactly but to be more of a learning experience and I figured I would continue to tweak things to my taste down the line. That information is appreciated though and will be something to consider with my next build after this one (and yes that build is already in the works haha)
Re: Plush as a Dumble style donor build
There are no factory schematics for the various versions of the Plush Super 450 available. There were at least 3 different versions of the 450 circuit and Plush, in those days, were in fly-by-night mode and just trying to stay afloat with no internal engineering on the payroll. Plush was looking to reduce labor and parts costs starting in 1970 and dove deep into PCB construction which ended up being an Achilles heel of sorts for them. Some of the early PCB's were poorly engineered and of poor quality and in some cases resulted in amps that caught on fire...never a good thing in general and definitely not good when an amp is being played on a dealers showroom floor and bursts into flames. Saul Marantz and his crew of engineers started Plush initially and after they got started, Ron Lipsky, the owner did have some design engineers up until 1971 or so...but after that no real engineering was on staff. BTW, no difference between the 2 x 12" 450 versus the 4 x 10" 450 other than the cabinet/speakers.
Nearly all the 450's (and the handful of 550's they built) were made in the Santa Fe Springs plant for which pretty much none of the assembly staff could speak English nor were they in the USA legally. The NYC factory (if you want to call it that) was shut down before 1972 came. A sales office was retained in NYC.
Also, none of the Plush Santa Fe Springs staff had electrical engineering knowledge. The assemblers simply copied a mocked up chassis that was hanging from a peg board in front of their workstation. Lipsky was fond of SoCal so he opened up the second factory and sales office so he could spend more time in SoCal...not so much for any sort of business strategy. There were some QC technicians on staff that would make certain the amps made noise, the controls worked and they didn't burn up during QC check. Those few technicians weren't really engineers either. Some served the dual purpose of a QC function and a test player.
By 1973, Plush was throwing together semi-finished amps and selling them to local SoCal electronics surplus shops (Net Electronics being one of them) just to keep the lights on though bankruptcy for Mr. Ronald Lipsky the owner (Who lived in Marina Del Rey) was right around the corner. By late 1973 when they could no longer get vendors to supply them parts they sold off the remaining inventories to various local surplus shops and should you wander into one of them during this timeframe you would find bins filled with Plush pots, trannies, chassis' and piles of passive components. Net Electronics actually started assembling some amps out of the spare cabinetry and chassis they ended up with and they sold those out pretty quickly by 1974. The guy who assembled them for Net Electronics is still alive and well and still doing tube amp repairs in and around SoCal...his name is George Rigney and should you be looking for a very skilled amp repairman near Vista, CA...give George a ring...he's really very skilled. BTW, George never worked for Plush...he was hired by Net Electronics the surplus shop.
Having interviewed a number of former employees (many years ago now) it was very common for Jeff Beck and Buddy Rich to show up at the Santa Fe Springs factory to pick up or drop off gear. Beck only used Plush gear live during one year of his Jeff Beck Group (Rod Steward/Ron Wood incarnation) for some dates on the East Coast but he remained in contact with Ron Lipsky (The owner) until the demise of Plush. They did build him some more "Marshally" amps that he would use when he was out in Los Angeles...not so much for gigging but in the studio I've been told. The 4000G model which essentially started out as a copy of the Traynor YBA-3 amp and then evolved a bit was the basis for one of the Jeff Beck Marshall type Plush amps that he was using/testing out with Plush in the early 1970's. The early 4000G used a quad of EL34's...just like the Traynor but later ended up with a quad of 6550's. Three different former employees confirmed this to me that Beck was a frequent visitor to the Plush Santa Fe Springs factory...so there likely is some truth to it. Also, they explained he would swing by the factory in one of his hotrods which was another fascination of Beck's during his lifetime.
Where these prototypical amps ended up? Who knows...but apparently several were built for him and he would take them, bring them back, get another, so and and so forth. He would sometimes go into the QC sound test room and start ripping...now that would have been memorable to anyone who was working there at that time. The only old pix of Beck using Plush gear dates to the 1969 JBG tour. Ron Wood definitely was using Plush gear and the drum kit and even vocals were running through Plush gear. Beck...sometimes you'll see him plugged into a Plush head at some shows but most of the stage photos from that tour show Marshall heads for Beck...Wood and others did use the Plush year on a number of dates. 1969 was where Ron Lipsky made the connection with Beck that persisted until the Plush demise in 1973.
Buddy Rich's band used the Plush Congress IV PA heads (Basically a Fender PA 100 long before the PA 100 came into existence). So an AB763 with 4 discrete channels. Buddy like the looks of the diamond tufted sparkle upholstery and he would mic up his kits with them. He used a variety of different oddball Plush enclosures loaded with a mixture of EV SRO's or JBL's and various horns in these enclosures as well. I have some pictures tucked away somewhere of Buddy on stage in the early 1970's with his Plush PA rigs on the backline.
Back to your 450 question on the reverb and vibrato circuitry. I have the reverb drive/recovery circuitry committed to memory for these amps (There were a couple different versions) along with the JFET Vibrato circuit...not much to them but both work very well. The Reverb on your amp will be a mixture of tube/transistor and utilize a high impedance pan...works pretty nicely actually, I'd argue better than the Fender all tube transformer low impedance an circuit that Plush used also on earlier Plush amps like the P1000S. The transistor is for certain going to induce more noise into the Reverb but it turns out to be negligible...the Plush high impedance Reverb circuit sounds just as splashy and springy as a Fender setup...less parts and less cost to execute.
So if you are wanting to use the 450 chassis and iron for a Dumble-type build...I say go for it. Plenty of real estate to work with and you can slap in the V1, V2 and V3 boards quite easily. Plenty of pre-amp tube holes to choose from as well. I would toss the crappy void-filled cheap plywood cabinet (Literally butt joints with wood glue and large staples holding the 4 corners together hidden underneath the Naugahyde) in the garbage...as that is what it is...garbage. I would build a custom head-shell for it for certain...you have to hang the chassis from the top like a Fender due to the angled bend of the face panel. Way more holes than you need on the front and back of the chassis to execute an ODS plus you can add an external OD trimmer very easily...lots of space to play with. You could even put HRM controls on the faceplate...its that long with that many holes!
The potential bad news, depending on how you configure the pre-amp in the chassis is you might need some long runs of coax...and that means more capacitance than ideal. So be sure to use a coax with low capacitance (like 16-17pf/ft.) and go with a coax type that is more typical to an ODS as that does come into play with the overall voice of the amp.
Other than that...it should be a straightforward build...plenty of details all over this site and elsewhere across the internet to draw upon. Like I said before, pay close attention to ground connections since it is a steel chassis. Like all high gain circuits, be careful with the plate and grid hookups for the preamp tubes...just look at any of the many Dumble ODS's that are documented here from a layout and lead dress perspective and you shouldn't have too much trouble. I would also run very short jumpers from the Power Tube Cathodes to ground...solder directly to the chassis...don't waste your time with the 1 ohm bias checker resistors to ground and definitely do not daisy chain the cathodes as Plush did on your 450 when originally built.
You should end up with a nice sounding amp as the end result. Lots of space to add in reverb or a tube buffered loop as well...common modifications to those that don't like the high impedance high voltage interrupt style loop of an ODS. Lots of options on what reverb circuit to run should you desire it.
Good luck...
Nearly all the 450's (and the handful of 550's they built) were made in the Santa Fe Springs plant for which pretty much none of the assembly staff could speak English nor were they in the USA legally. The NYC factory (if you want to call it that) was shut down before 1972 came. A sales office was retained in NYC.
Also, none of the Plush Santa Fe Springs staff had electrical engineering knowledge. The assemblers simply copied a mocked up chassis that was hanging from a peg board in front of their workstation. Lipsky was fond of SoCal so he opened up the second factory and sales office so he could spend more time in SoCal...not so much for any sort of business strategy. There were some QC technicians on staff that would make certain the amps made noise, the controls worked and they didn't burn up during QC check. Those few technicians weren't really engineers either. Some served the dual purpose of a QC function and a test player.
By 1973, Plush was throwing together semi-finished amps and selling them to local SoCal electronics surplus shops (Net Electronics being one of them) just to keep the lights on though bankruptcy for Mr. Ronald Lipsky the owner (Who lived in Marina Del Rey) was right around the corner. By late 1973 when they could no longer get vendors to supply them parts they sold off the remaining inventories to various local surplus shops and should you wander into one of them during this timeframe you would find bins filled with Plush pots, trannies, chassis' and piles of passive components. Net Electronics actually started assembling some amps out of the spare cabinetry and chassis they ended up with and they sold those out pretty quickly by 1974. The guy who assembled them for Net Electronics is still alive and well and still doing tube amp repairs in and around SoCal...his name is George Rigney and should you be looking for a very skilled amp repairman near Vista, CA...give George a ring...he's really very skilled. BTW, George never worked for Plush...he was hired by Net Electronics the surplus shop.
Having interviewed a number of former employees (many years ago now) it was very common for Jeff Beck and Buddy Rich to show up at the Santa Fe Springs factory to pick up or drop off gear. Beck only used Plush gear live during one year of his Jeff Beck Group (Rod Steward/Ron Wood incarnation) for some dates on the East Coast but he remained in contact with Ron Lipsky (The owner) until the demise of Plush. They did build him some more "Marshally" amps that he would use when he was out in Los Angeles...not so much for gigging but in the studio I've been told. The 4000G model which essentially started out as a copy of the Traynor YBA-3 amp and then evolved a bit was the basis for one of the Jeff Beck Marshall type Plush amps that he was using/testing out with Plush in the early 1970's. The early 4000G used a quad of EL34's...just like the Traynor but later ended up with a quad of 6550's. Three different former employees confirmed this to me that Beck was a frequent visitor to the Plush Santa Fe Springs factory...so there likely is some truth to it. Also, they explained he would swing by the factory in one of his hotrods which was another fascination of Beck's during his lifetime.
Where these prototypical amps ended up? Who knows...but apparently several were built for him and he would take them, bring them back, get another, so and and so forth. He would sometimes go into the QC sound test room and start ripping...now that would have been memorable to anyone who was working there at that time. The only old pix of Beck using Plush gear dates to the 1969 JBG tour. Ron Wood definitely was using Plush gear and the drum kit and even vocals were running through Plush gear. Beck...sometimes you'll see him plugged into a Plush head at some shows but most of the stage photos from that tour show Marshall heads for Beck...Wood and others did use the Plush year on a number of dates. 1969 was where Ron Lipsky made the connection with Beck that persisted until the Plush demise in 1973.
Buddy Rich's band used the Plush Congress IV PA heads (Basically a Fender PA 100 long before the PA 100 came into existence). So an AB763 with 4 discrete channels. Buddy like the looks of the diamond tufted sparkle upholstery and he would mic up his kits with them. He used a variety of different oddball Plush enclosures loaded with a mixture of EV SRO's or JBL's and various horns in these enclosures as well. I have some pictures tucked away somewhere of Buddy on stage in the early 1970's with his Plush PA rigs on the backline.
Back to your 450 question on the reverb and vibrato circuitry. I have the reverb drive/recovery circuitry committed to memory for these amps (There were a couple different versions) along with the JFET Vibrato circuit...not much to them but both work very well. The Reverb on your amp will be a mixture of tube/transistor and utilize a high impedance pan...works pretty nicely actually, I'd argue better than the Fender all tube transformer low impedance an circuit that Plush used also on earlier Plush amps like the P1000S. The transistor is for certain going to induce more noise into the Reverb but it turns out to be negligible...the Plush high impedance Reverb circuit sounds just as splashy and springy as a Fender setup...less parts and less cost to execute.
So if you are wanting to use the 450 chassis and iron for a Dumble-type build...I say go for it. Plenty of real estate to work with and you can slap in the V1, V2 and V3 boards quite easily. Plenty of pre-amp tube holes to choose from as well. I would toss the crappy void-filled cheap plywood cabinet (Literally butt joints with wood glue and large staples holding the 4 corners together hidden underneath the Naugahyde) in the garbage...as that is what it is...garbage. I would build a custom head-shell for it for certain...you have to hang the chassis from the top like a Fender due to the angled bend of the face panel. Way more holes than you need on the front and back of the chassis to execute an ODS plus you can add an external OD trimmer very easily...lots of space to play with. You could even put HRM controls on the faceplate...its that long with that many holes!
The potential bad news, depending on how you configure the pre-amp in the chassis is you might need some long runs of coax...and that means more capacitance than ideal. So be sure to use a coax with low capacitance (like 16-17pf/ft.) and go with a coax type that is more typical to an ODS as that does come into play with the overall voice of the amp.
Other than that...it should be a straightforward build...plenty of details all over this site and elsewhere across the internet to draw upon. Like I said before, pay close attention to ground connections since it is a steel chassis. Like all high gain circuits, be careful with the plate and grid hookups for the preamp tubes...just look at any of the many Dumble ODS's that are documented here from a layout and lead dress perspective and you shouldn't have too much trouble. I would also run very short jumpers from the Power Tube Cathodes to ground...solder directly to the chassis...don't waste your time with the 1 ohm bias checker resistors to ground and definitely do not daisy chain the cathodes as Plush did on your 450 when originally built.
You should end up with a nice sounding amp as the end result. Lots of space to add in reverb or a tube buffered loop as well...common modifications to those that don't like the high impedance high voltage interrupt style loop of an ODS. Lots of options on what reverb circuit to run should you desire it.
Good luck...
Re: Plush as a Dumble style donor build
Not the model schematic you're looking for but perhaps some clues that might be of help?
https://el34world.com/charts/Schematics ... l_bass.pdf
With respect, 10thtx
https://el34world.com/charts/Schematics ... l_bass.pdf
With respect, 10thtx
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doomedwizard
- Posts: 5
- Joined: Tue Oct 10, 2023 12:25 am
- Location: Austin, TX
Re: Plush as a Dumble style donor build
Wow a lot of good info in this post. I actually thought about doing a version with the HRM controls on the outside of the amp I just wasn’t sure if I’d get any hate for doing a build in such a non traditional way…but then again I’m just an amateur cloning an amp. I also thought about machining a new face plate from aluminum scrap I have at work (perks of hoarding all leftover material to get every last drop I can from it) I machined the g10 boards today as per some PDFs from another thread on this forum. I’ll be documenting the whole build with pictures and throw it up on here once I get further along. Next is souring any components I don’t have on hand which is luckily not a whole lot at all.GPD wrote: ↑Tue Oct 17, 2023 7:26 pm So if you are wanting to use the 450 chassis and iron for a Dumble-type build...I say go for it. Plenty of real estate to work with and you can slap in the V1, V2 and V3 boards quite easily. Plenty of pre-amp tube holes to choose from as well. I would toss the crappy void-filled cheap plywood cabinet (Literally butt joints with wood glue and large staples holding the 4 corners together hidden underneath the Naugahyde) in the garbage...as that is what it is...garbage. I would build a custom head-shell for it for certain...you have to hang the chassis from the top like a Fender due to the angled bend of the face panel. Way more holes than you need on the front and back of the chassis to execute an ODS plus you can add an external OD trimmer very easily...lots of space to play with. You could even put HRM controls on the faceplate...its that long with that many holes!
Re: Plush as a Dumble style donor build
Some pix of the guts of your 450 will make it easy for me to tell you what version you have. The last generation (version) of this amp had a PCB for the Reverb and Vibrato controls that mounted on the back of the chassis face...actually, quite a sanitary setup and makes for a very fast and simple assembly. Its a single sided PCB...and rarely are they problematic. Even if they are...easy enough to jump the traces...I think in the decades of repairing these amps I've only had to do that once. If you've got this you should definitely plan on retaining the stock reverb/vibrato circuit and just tack it on to the Dumble ODS V1/V2 you install. I'm attaching a picture of what this looks like up close...don't toss this if your amp has it...a very useful board for any project where you want both Reverb and Vibrato. That little trimmer pot with the arrows is important...part of the chopper FET based Vibrato circuit...works really well and actually sounds much better than the the Fender Optoisolater style Vibrato most are familiar with.
Attaching another picture of the big brother to the Super 450, the Super 550 which is a 6 x 6L6GC version of the 450...same chassis. You have different options on where to build the pre-amp. Stock, you can see some of it is on terminal strips towards the front of the chassis with the tubes right behind the terminal strips. The PCB in the middle of the chassis is the Bias Supply/Polarity Splitter board. If you look closely on the back row, you'll see holes where I would recommend you run the Dumble clean (V1) and OD (V2) tubes. You chassis might be punched differently...there were many variations but odds are you have the 3/4" pre-amp holes just like the 550 gut shot pictured. You have a couple of 1.125" holes for running multi section electrolytic cans...I like these, personally, and often use them for filtering the pre-amp tubes versus discrete mounted underneath the chassis...your call on what you want to do. Note, Plush put the OT on the opposite side of the chassis and you can see the braided sheathing in place which you might (or might not) need for your amp. You can relocate the OT to a central spot of the chassis like a Fender or Dumble if you want it further away from the pre-amp tubes...again, lots of space to work with. If you do not like where the holes are already punched? Well, punch your own where you want them...note the vast expanse of chassis to work with...tons of space.
If you use ground lugs...solder them directly to the chassis...your grounding scheme as I stated before is going to be very important if you want a decent S/N ratio.
Attaching another picture of the big brother to the Super 450, the Super 550 which is a 6 x 6L6GC version of the 450...same chassis. You have different options on where to build the pre-amp. Stock, you can see some of it is on terminal strips towards the front of the chassis with the tubes right behind the terminal strips. The PCB in the middle of the chassis is the Bias Supply/Polarity Splitter board. If you look closely on the back row, you'll see holes where I would recommend you run the Dumble clean (V1) and OD (V2) tubes. You chassis might be punched differently...there were many variations but odds are you have the 3/4" pre-amp holes just like the 550 gut shot pictured. You have a couple of 1.125" holes for running multi section electrolytic cans...I like these, personally, and often use them for filtering the pre-amp tubes versus discrete mounted underneath the chassis...your call on what you want to do. Note, Plush put the OT on the opposite side of the chassis and you can see the braided sheathing in place which you might (or might not) need for your amp. You can relocate the OT to a central spot of the chassis like a Fender or Dumble if you want it further away from the pre-amp tubes...again, lots of space to work with. If you do not like where the holes are already punched? Well, punch your own where you want them...note the vast expanse of chassis to work with...tons of space.
If you use ground lugs...solder them directly to the chassis...your grounding scheme as I stated before is going to be very important if you want a decent S/N ratio.
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doomedwizard
- Posts: 5
- Joined: Tue Oct 10, 2023 12:25 am
- Location: Austin, TX
Re: Plush as a Dumble style donor build
Mine has a 1” eyelet style board for the preamp and a lot of terminal strips holding flying components. No PCBs. When I originally took this amp apart I was banking on using all the original components and maybe replacing any as needed. The resistor leads are too short to do that on this build, but the orange spragues and mallorys seem like they could work. I’ll test those on an LCR meter soon. As far as resistors go I have an endless stash of xicons laying around that could easily carry this build. Just ran out of eyelets tho so that’s my only hold up at the moment
Re: Plush as a Dumble style donor build
OK, so if you look at your chassis there will be pencil markings on it with a date (maybe multiple dates) and odds are they date to 1971...or early 1972. From what you describe you have the earliest incarnation of the Super 450 which uses a fiberglass tag board with well-type eyelets (Commonly found on Televisions and other electronics of the 1960's before PCB's came into vogue). I would not salvage any of the passive components from the donor amp other than perhaps the potentiometers which are most likely Centralab...so nice thick carbon composition resistive elements. Plush also did use CTS pots from time to time...these too are worth salvaging. I'm attaching a picture of an old Super 450 with the 1st generation, tag board construction for your perusal...should look very familiar to you. Regarding passive components...
I would avoid using cheap parts (like Xicon's as Xicon is just a brand owned by Mouser and the parts could have been made by any number of low cost resistor mfg.'s). Plenty will argue that modern parts are more than suitable...after all, Fuchs, Two Rock and many others building Dumble Clones use modern parts that are ROHS compliant and nobody complains about these amps. But if you are going to go through the effort for such a build...why not get your hands on some good old NOS parts more commonly found in the Dumble amps that Dumble built? Jelle, for a modest fee, can outfit you with pretty much anything you need on the passive component side...so why not?
I have a few old Plush 450 chassis laying in my "pile-o-stuff". I'll dig one out and overlay some boards and show you how much room you have to work with...its pretty crazy how massive that 450's chassis is
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I would avoid using cheap parts (like Xicon's as Xicon is just a brand owned by Mouser and the parts could have been made by any number of low cost resistor mfg.'s). Plenty will argue that modern parts are more than suitable...after all, Fuchs, Two Rock and many others building Dumble Clones use modern parts that are ROHS compliant and nobody complains about these amps. But if you are going to go through the effort for such a build...why not get your hands on some good old NOS parts more commonly found in the Dumble amps that Dumble built? Jelle, for a modest fee, can outfit you with pretty much anything you need on the passive component side...so why not?
I have a few old Plush 450 chassis laying in my "pile-o-stuff". I'll dig one out and overlay some boards and show you how much room you have to work with...its pretty crazy how massive that 450's chassis is
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doomedwizard
- Posts: 5
- Joined: Tue Oct 10, 2023 12:25 am
- Location: Austin, TX
Re: Plush as a Dumble style donor build
Yup that looks just like mine. Except like I said mine has Mallory/sprague orange drop capacitors so I wonder if someone had put those in after the fact. There seems someone had done some mods to this amp at one point but took them out judging from some crudely cut holes oddly placed in the chassis. As far as usable components go tho I don’t have much left from this build. Most of the pots were completely seized and even after spraying with deoxit they’re still fairly stiff and eventually go back to being stuck again. Most likely I’ll order new pots (thinking about push pulls for brite, deep and possibly even rock/jazz settings). Only a few of the orange drops I have seems to fit the bill, but I do have a large collection of silver micas that I’m wondering if could be used in this build. The carbon comps went straight into my stockpile for another build (not only are these useful for vintage audio but they’re also very sought after for my job in the pulsed power world). I have some F&Ts added to my cart so I might as well just order some new caps while I’m at it. As far as the xicons go I saw them listed in a few builds and BOMs on here and figured since I have a huge lot of those available at work I might as well use them. I see this build as a never ending journey of sorts so later down the line I’ll replace them with a more on brand resistor for a Dumble. I’d appreciate a layout if you have any ideas. With the amount of space I have and only using the rectifier, filter, preamp and jfet boards it seems like I won’t have any issues.