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PostPosted: 12 Sep 2011, 18:13 
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Joined: 17 Aug 2011, 06:05
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Location: Australia
pleasure mark :)
should be about 20 mins from work for me i think. about same from home (50 mins) - home is werribee

ah yes. seen them before but never bought one. don't need an excuse to go to bunnings mate :)
well now that is strange.

ground the tranni frame? its plastic. I was going to have two grounding points - one for the 12VDC and one for the 250VDC. oh if you look at the top of the pic you can see a leg of the 0.01uf :)
thanks for the tip though on the cheap big electros - hence why everyone gets the more expensive caps such as auricap ect to quieten things down. get what you pay for.

oh : PS if you order stuff from futurlec, it comes from overseas. hence the expensive postage and the fact it takes 2-3 weeks to get here. although i've enough capacitors and resistors to sink a ship :)

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PostPosted: 12 Sep 2011, 20:12 
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Location: Australia
I didn't mean earth the wall wart but the 24V to 240V step-up tranni. Should be metal. Earth its frame.

Some CRO results into 33K load gain results with pot open full the 3db points with pot at 80%

12AU7: Gain of X5 -3db points <10hz to 40Khz
12AT7: Gain of X5 -3db points <10hz to 36Khz
12AX7: Gain of X7.5 -3db points <10hz to 33Khz

Sqr wave results at 100hz and 10khz are not the best but good at 1000hz. For those who would like to build the Universal here are the updated drawings, same as Matt's Universal hand drawing.
Attachment:
4SMKIVss.jpg
Attachment:
4SMKIVPSss.jpg


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Projects: | “La Ruse” - tube SRPP ECC83 preamp | "Noir” - Psvane tube preamp | ”fiih-300” - 300W Holton based amp | "Sortilege" - 180W Tripath Class D Mundorf upgrade amp |


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PostPosted: 12 Sep 2011, 22:21 
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mark pSpice for the win dude :)

hmmmm. yes the frame of the step up is metal. earth to what? earth to +240vac from the wall, or, ground from the 240vdc 'stepped up' and rectified?

sorry this is one thing i'm not clear on. earthing. in alot of the schematics i look at, it calls out a ground - as per your diagram up there mark. is that ground that you infer a DC ground post rectification (ie : the negative side of the +12vdc), or an earth from the wall? i suspect its the former but the logic somewhat confuses me. my friend tells me that earth is a ground potential which confuses me even more.

furthermore, if i wire up an IEC plug, i have three pins, active, neutral and earth. where does earth from the IEC (from the wall) get wired to?

apologies for the dumb questions, need to get my head around this.

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PostPosted: 13 Sep 2011, 00:47 
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I don't think you are building the same amp/PS on this thread. You should have a 24V AC wall wart feeding the secondary of a 240/24V step down tranni. So 24V in 240V out. After rectification, the negative of the HT should be connected to the metal frame of the tranni (not wall wart). You have me concerned.

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Projects: | “La Ruse” - tube SRPP ECC83 preamp | "Noir” - Psvane tube preamp | ”fiih-300” - 300W Holton based amp | "Sortilege" - 180W Tripath Class D Mundorf upgrade amp |


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PostPosted: 13 Sep 2011, 04:46 
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mark - thanks i appreciate your concern mate :)
yes i'm building this little guy (preamp) - but i am also researching future 'projects' - hence the questions about the IEC etc.
i printed out the diagram in A3 so i make sure when i wire it i get it right :)

so (another dumb question) even though i have rectified 240vdc out (so + and - 240vdc) and 12vdc for the heaters (also + -) i ground (or put the negative) of the 240vdc out onto the frame of the step up tranny (no not the wall wart) and provide ground to the rest of the circuit where required. understood. the 12vdc is for pin 4 and 5 of the heaters and thats all.

now, initially i was going to build an amp ala whats here http://www.ozvalveamps.org/ava100/ava106lamington2.htm but this is a guitar amp and i don't understand enough of this and won't do it until i am comfortable with my understanding - i have a healthy respect for the 240VAC 10A that comes out of the power socket and until i understand it completely (to be safe) will i then embark on something else. hence things that use the 'wall wart' are 'safer' (with the exception of the step up transformer) and things like the bottlehead and the oatley electronics headphone amp with the 6418s are keeping me busy.

in summary i need to walk before i can run. i don't want to get dead due to being silly or over excited - so apologies if my questions are silly - am trying to learn the best i can.

thanks mate. i appreciate your help and your concern i really do.

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PostPosted: 13 Sep 2011, 07:43 
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The Lamington (tin) amp is a goody.

Take a look at my Fender Champ with cotton coated wire, 1970 lead solder, 40 years old Australia black glass 6V6GT and and Australian made 12AX7. The chasis is cheif's steel baking pan, stiff as. I used tube rec. here and choked it. I bought 30 year old 12" Jensen (Alnico magnet) speaker from the States. I wanted an older sound as I could get. This does it.

http://mongreldogaudio.blogspot.com/2009/11/mongrel-dog-audioo-guitat-puppy.html

The negative of the 12V heater voltage and the negative of the HT volatge can be joined together. Either one can go to the step-up tranni frame.

Some might say leave the heater voltage floating. In other words do not join the two grounds together just connect the heater voltage to 4 + 5 (pin) of the tube. I have joined them everytime and found no probelm. What would you do Matt?

Hey mate just keep asking questions and I'll just keep making-up answers (haha).

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Projects: | “La Ruse” - tube SRPP ECC83 preamp | "Noir” - Psvane tube preamp | ”fiih-300” - 300W Holton based amp | "Sortilege" - 180W Tripath Class D Mundorf upgrade amp |


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PostPosted: 13 Sep 2011, 16:12 
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thanks very much mark - i'll have a look at that now.

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PostPosted: 16 Sep 2011, 03:04 
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I had a second pair of ears around today. We compared the MKIII The Black to the MKIV Universal, Dave's selection each time came back to the Universal (12AT7). We swapped them in and out, over and over again. For the last few days I have listened to nothing else but he MKIV. I think the 4S MKIV Universal is the best. It hurts 'cause I felt nothing would beat The Black. It may just be the vero-board which made the difference!!??!!.

But Dave did like the Oppo BDP-83 direct into the Pass F5's he just made and we were using on the day. I'm about to mod the MKIV and have the bypass cap across the Rk switchable in or out. I'm looking forward to this.

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Projects: | “La Ruse” - tube SRPP ECC83 preamp | "Noir” - Psvane tube preamp | ”fiih-300” - 300W Holton based amp | "Sortilege" - 180W Tripath Class D Mundorf upgrade amp |


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PostPosted: 18 Sep 2011, 00:14 
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Being very pleased with the performance of the 4S MKIV Universal with the English 12AT7 (tested 100% on my tube tester) I decided to make the cathode caps switchable in and out. It sounds nicer with caps out. You can hear a small increase in volume when switched in and the sound takes on a little bass weight up into the mids.

Sounds cleaner and clearer with a little local NFB. I have some Gold Lion 12AX7 and 12AU7 tubes to try in it yet. Also I replaced the Ozzy 12AX7 in my 3W 6AS7 SET with a Gold Lion 12AX7.

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Projects: | “La Ruse” - tube SRPP ECC83 preamp | "Noir” - Psvane tube preamp | ”fiih-300” - 300W Holton based amp | "Sortilege" - 180W Tripath Class D Mundorf upgrade amp |


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PostPosted: 18 Sep 2011, 15:52 
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Joined: 06 Apr 2009, 10:08
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Mark;

Have you had an opportunity to try out the universal with a 12AY7? I'm curious as to how it will sound.

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