Drip V72 build (pics)

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Bowie

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Zander said:
Sorry to post in here.


Does somebody still have the documentation for the drip72 project? Can't find it elsewhere.


Zander
What do you need?  I'm still struggling to get the noise down in mine but I do have the manual, etc.
 

duy_hoang

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Apr 26, 2009
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Berlin
The roll off is due to the caps and resistor in the gain setting part, which form a RC-filter.

Michael Tibes said:
Stagefright13 said:
Actually that is good. Only -1.5 at 20k. I typically roll of stuff that goes that high depending on what it is. :)

John

Well, the original goes higher... I wonder why? The Lundahl should probably be better than the 40 year old iron?

Michael
 

Bowie

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JingleDjango said:
Any drip boards going around still?
I have an unpopulated Drip V72 v2 PCB that I may or may not sell.  I just ordered parts to see if I can successfully do the 55dB mod (bring the gain from 34 to 55).  If successful, I'll keep the 2nd board.  If not, I'll have the board + new parts available.  Will know in a couple weeks.
 

JingleDjango

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That would be great. I'm curious what these cost? I guess with Drip he does a single run of every board he designs and that's it?
 

Bowie

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JingleDjango said:
That would be great. I'm curious what these cost? I guess with Drip he does a single run of every board he designs and that's it?
I think they were around $125 if memory serves.
It used to be a legit company with regular product runs but the customer service is now intermittent at best and straight answers are few and far between.  Really unfortunate that it went south.
 

JingleDjango

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That's a shame. I've been getting really excited about done of his boards, particularly this pre. Most diy preamp builds I've seen are 500 series designs and I don't have or need a lunchbox. Can you recommend anything similar to the v72?
 

Bowie

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JingleDjango said:
That's a shame. I've been getting really excited about done of his boards, particularly this pre. Most diy preamp builds I've seen are 500 series designs and I don't have or need a lunchbox. Can you recommend anything similar to the v72?
There was mention of a different V72 pcb run in the black market here recently.  The V72 is not a complex circuit but is highly recommended.  There's really something special about the sense of depth and the smooth, airy top end response.
 

My3gger

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Why not make it point to point or have circuit on pcb wired to tube sockets on L profile or similar? You would learn a lot more, wouldn't depend on lacking support (this problem comes up often), then functions can be added, removed or modified, etc. Same goes for psu although it is simpler having it on pcb. This is how many of us started and continue to do so to this day. I saved several nice&simple p2p layout examples for those who want to see how things are put together this way.
 

Winston OBoogie

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Yep, the V72 is a fairly simple circuit and easily made point-to-point.
You could even just copy the tagboard type layout that's in the original.

I'm not sure how Drip does the gain adjust etc. but just use the scheme found in the V77 which, in the V72 with a 1:10 input transformer, will give you gain between about 28dB and 48dB. Change the V77's main series feedback resistor from 50K to about 100K and gain will be 34dB - 54dB.
 

Urskov

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Jan 6, 2020
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Fredensborg, Denmark
I'd be very interested to have a look. Just finishing up the Drip dual STA-Level, and was thinking about p2p for my next project.
Stephen
Same! Woud really love to see a V72 layout. Building a REDD 47 p2p atm - would be fun to also try the preamp that the REDD 47 replaced!
 

My3gger

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I'd be very interested to have a look. Just finishing up the Drip dual STA-Level, and was thinking about p2p for my next project.
Stephen
I'm not sure original V72 layout will be of any use here because it was made for cassette, i'm attaching schematic with voltages and terminal board M Rippie posted.
There are many ways to wire the circuit, having it in rack makes more sense than cassette. I did them the way LA2A was done with tube protruding from the back plate which is better technique for compressors producing more heat than 1-2ch preamp. Some were on good quality veroboard where components are connected with pins on the top of it, other with turret board and small turrets for connecting components (not forked turrets used in fender amps). Both had tubes on L profile inside chasis wired to boards (not all are V72s) making build safer in use.
I'm adding dual Pultec MB1 from another member which is easily adaptable layout with good pics and description. Mine wouldn't help because i draw them only partially where needed. I wouldn't change much in MB1 ,except having psu board horizontally for safety and use toroid with regulated HT and heaters for lowest noise. 1ch is easier to make and troubleshoot:
Gyraf G9 has nice regulated psu i used for some projects, it can be done on pcb or even veroboard if care is taken with layout: Gyraf Audio - G9 DIY
MB1 layout author is using components available from big shops, it makes project cheaper and datasheet for each component is provided. I believe they are higher quality than audiophile or guitar stuff, beside radial component leads can help with tighter layout better following current loops. My signal wires come from good multicore cable because it lasts a long time and is cheap.
I can check for another V72 schematic with voltages if needed. Making layout should be fairly simple with this example.
 

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  • V72 Schem with notes voltages and turret layout original.pdf
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