Zen Mod said:
er, it's just the 90V supply voltage that might come in handy. Anyways, carry on!!
wirewiggler said:
well - firm hug of Q4 and Q5 is sorta more important than their exact matching .
matching certainly can't harm , but - don't loose your sleep ......
I presume that output voltage is steady 😉 , no hum , no whirl ..... so - mission accomplished .....
They are like kissing cousins with some kind of kinky plastic belt. So far so good. Had to finish harness between chassis then will add covers and allow to cook and readjust.
Bill
Bill
OK,
got things wired up and allowed them to warm up a bit. Was able to dial offset down below a volt but it dances around a bit. I didn't really give it a chance to truly reach a stable temp. I will look forward to the servo. I got my Joshua tree attenuators up and running but not my source selector is tomorrows project. Then I can check it on the scope. Come to think of it how would I check the balanced outputs on the scope short the minus to ground ?
Bill
got things wired up and allowed them to warm up a bit. Was able to dial offset down below a volt but it dances around a bit. I didn't really give it a chance to truly reach a stable temp. I will look forward to the servo. I got my Joshua tree attenuators up and running but not my source selector is tomorrows project. Then I can check it on the scope. Come to think of it how would I check the balanced outputs on the scope short the minus to ground ?
Bill
wirewiggler said:
😉
you need either :
isolation xformer for your scope , or
any decent signal xformer between Pumpie output and scope , or
cap between both gnd and hot of scope , and Pumpie .
that last can be used as Poor Man's xformer 😉
Pumpkin/Shunty in temporary home
I threw together a maple box to listen to Pumpie while waiting for a few nicer parts and to work out switching, etc. That's a Goldpoint balanced (quad) attenuator sitting on top doing duty, some day to be replaced by a nice balanced Lightspeed with remote.
I threw together a maple box to listen to Pumpie while waiting for a few nicer parts and to work out switching, etc. That's a Goldpoint balanced (quad) attenuator sitting on top doing duty, some day to be replaced by a nice balanced Lightspeed with remote.
Attachments
tms0425 said:
whoa !
that's fugly !!!
OK- entire room/system is looking real cozy , but wooden case is ..... sort of - to die for
😉
That case used to be a single 4' x 6" $10 piece of solid maple from the hardware store, cut in 4 pieces, miter'd and glued corners, with a little bit of wipe on poly satin finish. ...and lots of 1/4" holes in the top for a heat stackZen Mod said:
4 XLR's for in/out on the back and 7-wire detachable umbilical in Techflex wrapping down to the other little wood box on the lower right with the transformers, mains filter, fuse, switch, etc. So far it is dead quiet through the outputs that way.
tms0425 said:
Dedicated listening room....Jealous.
I wouldn't mind knowing the mods to the DCX that were done.
I took mine out of the upper frequencies, sounded only okay. Too much diode noise.
Tea-Bag said:
My final DCX mod list:
- Replace analog inputs and outputs with Linear Audio (Jan Didden) remote control analog I/O board with a few tweaks
- Remove CS8420 digital in. Install Frank Oettle CS8416 clock/SRC replacement board (<2ps jitter).
- Replace 2 7805 regulators with 2 Oettle discrete mini-regulators (5v)
- Removed extra A/D converter not used on C input
- Replaced 3 AKM 4393 DACs with AKM 4396 DACs
- Replaced all electrolytics with Panasonic FM's, Black Gates, and Elna Silmic II's
- Installed LC filters on +/-15v lines
- Rewired and reterminated AES/XLR input with BNC SPDIF 75 ohm with coax direct to input transformer, bypassing ribbon cable and connectors
- Add external "Felix" AC mains filter
At this point there isn't much left to do. I'm not sure this poor DCX chassis/pcb could take any more soldering to improve it so I think I"ll quit while I"m ahead. Sounds pretty good this way, better than I ever imagined this cheapo DCX could get.
Where did you buy your mods for the DCX? I have been looking at putting one together myself.
Bill
Bill
I bought Jan Didden and Frank Oettle's kits from Ward at Pilgham Audiowirewiggler said:
The AKM 4396 DACs are a little harder to come by, but I think Scott Endler was going to buy some for resale so you might check with him. Otherwise there have been a few group buys on occasion.
The SMT soldering is not trivial, so I'd recommend buying the Oettle board preassembled or at least starting with the regulators first if you haven't done it before.
ChipQuik is an absolute must for desoldering parts on the DCX board at lower temperatures.
Tom
Well,
I got tired of waiting for micro controller and hooked the Pumpkin up with some manual switching. I have to admit I was quite surprised the upgrade in sound from my XBOZ. Much better detail & sound stage. From my analog source it would seem to have more bottom end. ZM are you still considering a servo for off set it doesn't seem to hurt sonics but it wonders all over the place. I don't have a cover over due to wires hanging out so I am sure that is not helping.
Thanks
Bill
I got tired of waiting for micro controller and hooked the Pumpkin up with some manual switching. I have to admit I was quite surprised the upgrade in sound from my XBOZ. Much better detail & sound stage. From my analog source it would seem to have more bottom end. ZM are you still considering a servo for off set it doesn't seem to hurt sonics but it wonders all over the place. I don't have a cover over due to wires hanging out so I am sure that is not helping.
Thanks
Bill
wirewiggler said:
bettering XBOZ isn't suprise to me
servo is little postponed because of my recent troubles with my back , but I hope that I'll make tests soon ....... even if I'm pretty sure that it will be functional
anyway - not having formal education in electronics is sometimes more than fun thing ...... I'm always surprised when something I drew on back of napkin is actually working .......
( is it just plain curse , realizing how Papa drew something like that ages ago...... ?
maybe is better and shorter just to ask him for working servo 
)Sorry the back is still bothering you, I have issues with mine too. To much fun in my youth. Never learned my lesson still having fun in senior years as well. I just take enough pain medication and my back will finally loosen up and gets better. As I am sure the design contributes to better sound, I also pushed the budget with Audience caps bypassed with kimber - the XBOZ has Solen.. I used Audience in my tube amps and liked them. In fact I had been listening to my tube amps with my back loaded horns and hadn't turned on the F4s for some time, was quite surprised how much more I like the F4 with Pumpkin. They were sounding quite sterile by comparison to the tube amp with BLH.
Thanks
Bill
Thanks
Bill
I'm afraid that this thread is so long that the answers to these questions may have been posted and I just didn't find them...
I need a new diy project, and am considering an F4, and a preamp flexible enough to use either with it or with my diy F5 (which I am v. happy with...) Candidates for the preamp include an Impasse (which Nelson suggested, and which would be a first tube project) or I am now thinking about a Pumpkin. A couple of questions:
1. Is it OK to use one shunty for a stereo Pumpkin? (I guess yes, but I got a bit confused trying to follow the thread...) On the schematic, "4E7" means 4R7, or 4.7ohms, right? A transformer described as 84Vct means a simple secondary with 84Vac output? Clearly the "AC" connections mean the output from this secondary, but what are "Vin" at J1 and J1A?
2. The schematics don't show any volume pots, or any other controls for that matter. I understand from this that the circuit is a gain stage, and some kind of volume control should be put first. (Right??) Would it work well following a B1 buffer preamp? Or should the B1 come after? If I made a good B1 preamp I could experiment the Pumpkin and/or Impasse, or other gain stages that I could put in separate cases. (Suggestions for other circuits??)
3. If I try to build a Pumpkin by dumpster diving to save a few $$$, I could try heatsinks for the mosfets that I pulled out of computer PSUs. Anyone tried them? Likely good enough? (My best guess would be yes...)
4. I have not etched a PCB before, and thought about having a go with this circuit, but the PCBs here seem to be all two-sided. Anyone done a one-sided version? I am quite happy to try p2p, but it would be fun trying a pcb....
Well, thanks for any help
Cheers
Nigel
I need a new diy project, and am considering an F4, and a preamp flexible enough to use either with it or with my diy F5 (which I am v. happy with...) Candidates for the preamp include an Impasse (which Nelson suggested, and which would be a first tube project) or I am now thinking about a Pumpkin. A couple of questions:
1. Is it OK to use one shunty for a stereo Pumpkin? (I guess yes, but I got a bit confused trying to follow the thread...) On the schematic, "4E7" means 4R7, or 4.7ohms, right? A transformer described as 84Vct means a simple secondary with 84Vac output? Clearly the "AC" connections mean the output from this secondary, but what are "Vin" at J1 and J1A?
2. The schematics don't show any volume pots, or any other controls for that matter. I understand from this that the circuit is a gain stage, and some kind of volume control should be put first. (Right??) Would it work well following a B1 buffer preamp? Or should the B1 come after? If I made a good B1 preamp I could experiment the Pumpkin and/or Impasse, or other gain stages that I could put in separate cases. (Suggestions for other circuits??)
3. If I try to build a Pumpkin by dumpster diving to save a few $$$, I could try heatsinks for the mosfets that I pulled out of computer PSUs. Anyone tried them? Likely good enough? (My best guess would be yes...)
4. I have not etched a PCB before, and thought about having a go with this circuit, but the PCBs here seem to be all two-sided. Anyone done a one-sided version? I am quite happy to try p2p, but it would be fun trying a pcb....
Well, thanks for any help
Cheers
Nigel
njepitt said:
first - if you look at my sig line - you can find link to Pumpkin "clean thread " , which is made by great effort of our
- to clean this one from numerous off topic posts and other sidetracking ....there you can maybe can find informations somewhat easily ;
was primary made for F4 in balanced config ; even if most important goal was to squeeze every possible volt from balanced F4 , little pumpie is surprisingly good even in lower gain settings ( adequate for F5 , which needs no more than few volts at input for full blast ) .I dunno for Impasse , which is certainly one hell of a preamp for same role - driving balanced buffer , how is acting in less demanding role - idling with just few volts at output . you must ask SY about that .
anyway - as I mentioned before - with both Pumpie and Impasse , world is your Oyster :
just imagine these combos -
two preamps - one Pumpie ( SS) , one Impasse (real parts , not 3 legged fuses
)two output buffers - one F4 (SS) and one tube (just output stage , without any sort of drivers and/or phase splitters - which is then pretty close to zero gain ie. buffer )
what combination you'll make , is just your choice ...... driving SS amp with SS preamp, or tube amp with SS preamp , or SS amp with tube preamp , or tube amp with tube preamp .....
OK ......
1. yes - one Shunty for two Pumpies , with better heatsinking than for 2+2
4E7 is old European trick to confuse boyz from other side of Big Splash
........ same as you boyz wrote uuF , driving us nutz but - 84Vst means 84V center tapped on both sides of silly ocean 😉 , and you can imagine it as twice 42Vac
Vin at J1 and J2 are points for connecting DC pos & neg supply , in case that you already have adequate voltages ( from power amp PSU , for instance ) so there is no need for additional rectifying with internal Pumpie's Graetz bridge .
2. in most cases - volume pot is going BEFORE gain stage ; both Impasse and Pumpie don't need any sort of buffer before them ...... and God forbid after them . that's pure redundancy .
3. you can use for heatsinks even plain sheets of Al or Cu . but - at least from my experience - for dumpster dive approach in making singing gadgets , you must have pretty much more experience than you have - at least according to your questions ;
don't take that even slightly as insult - nobody is born knowing everything ..... but Pumpie is everything but simple ;
it is simple - just 4 active parts per channel , counting it even in balanced mode ....... but rest is pretty complicated , in case that you don't have enough understanding of each part functionality ...... and in that case - everything is simple 😉
4.
look at post No.2 of this very thread - Lykkedk made Pumpkin on one side pcb ..... even without Shunty it's working pretty well ......
in any case - good luck ; if you ask me for advice - I'll made two amps and two preamps in your boots .......
edit:
I had impression that I wrote pretty clear Cook Book ; did you read it ?