U73b (drip) - 3 questions

[Sc]

Hm - I'd say the Drip has a rather flat response - here at +2dB

 

[Sc]

At higher levels there's a slow increase from about 5k - 12k, not more than 1.5dB

 

[andre tchmil]

that's interesting , I wonder what causes that. The 88CC tube ?
While we're at it , I measured the various plugin emulations; Response is super flat throughout

 

[Sc]

You said "boost at 5k " - more than the Drip ? Threshold is one of the parameters beeing calibrated to originals spec's in original units- we play around with it today ... . But compared to high class speakers curves a max. deviation of +1.5dB is probably not very much.

 

[Sc]

Hi
Glad to show you some pics of my U73b with varicom build - fully operational and within specs finally. Varicom still needs a nice front plate though .... We discussed several tweaks here and in other threads. This setup now has two Drip mainboards (V1), two separate unregulated B+ PSU with chokes and much lower capacitance over all (also on the mainboards), two DC-Heater PSU's (hvforless on ebay), Sowters and Haufe BV514 (still availiable). The green front boards are designed by a friend and feature the original time constant U73b and the switches and connectors for bridging R55 with 10M in varicommode. Bridging R80 ist not necessary, since the old manual refers to U73 (not U73b) where R80 is not in the control line. Added working attack switch in the control line. Varicom has also newly designed boards including the calibration switches and feature the beautiful MD188 reconstructed by Manfred Deppe (maybe he has some left) and has it's independent own PSU. Flipping one switch on U73b and varicom each engages or disengages the varicom - could be one instead, but I wanted to have these independent.
Can't show you here because of the large audio-files, but the varicom is fantastic to have a fully automatic pleasant compression over a raw digital studio file. You just set the switches (pretty interactive) to a good setting for the music style and let it work then. A long way to go - but worth the pain .

Cheers
Walter

 

[L091c]

Hi
Glad to show you some pics of my U73b with varicom build ... A long way to go - but worth the pain .

Wow that looks amazing Walter!
What meters did you use? Printed the meter scales?

Joshua

 

[Sc]

Hi Joshua - thanks ! The U73b meters are Simpson 27. Jason at IMS was kind enough to print the scales with the specs we measured. These are availiable - also with the round instrument.

https://www.metersales.com/shop/pro...y=139#attr=120740,120742,120743,120741,120744
I have no idea, where the Varicom - Instrument was used - probably military surplus (100uA - calibration point is 63uA).

 

[opacheco]

Hi
Glad to show you some pics of my U73b with varicom build - fully operational and within specs finally. Varicom still needs a nice front plate though .... We discussed several tweaks here and in other threads. This setup now has two Drip mainboards (V1), two separate unregulated B+ PSU with chokes and much lower capacitance over all (also on the mainboards), two DC-Heater PSU's (hvforless on ebay), Sowters and Haufe BV514 (still availiable). The green front boards are designed by a friend and feature the original time constant U73b and the switches and connectors for bridging R55 with 10M in varicommode. Bridging R80 ist not necessary, since the old manual refers to U73 (not U73b) where R80 is not in the control line. Added working attack switch in the control line. Varicom has also newly designed boards including the calibration switches and feature the beautiful MD188 reconstructed by Manfred Deppe (maybe he has some left) and has it's independent own PSU. Flipping one switch on U73b and varicom each engages or disengages the varicom - could be one instead, but I wanted to have these independent.
Can't show you here because of the large audio-files, but the varicom is fantastic to have a fully automatic pleasant compression over a raw digital studio file. You just set the switches (pretty interactive) to a good setting for the music style and let it work then. A long way to go - but worth the pain .

Cheers
Walter

Dear Sc,

Could you share the TVS type and number used in your Varicom please? Manfred Deppe said this parts are actually manufactures still but don’t gives us more info about the specific TVS data sheet used for him Varicom.

Thanks a lot anticipated
opacheco

 

[Sc]

Hi opacheco
Now you really got me on the wrong foot - that's the point I'm not absolutely sure and my knowledge about the technical function of these three TVS is limited. So I dont' have a bulletproof solution. Maybe we have some engineers our there ... . The link goes from anode E88CC over 2uF / TVS and 10k to the grid, while on the other side over 2nd anode / cathode follower into the T188. So the purpose cannot be just to avoid transients - you usually don't need a link anode - grid. The 2uF will block DC - so there will be (if I'm right - please let me know if not) some sort of (by TVS) min./max. limited feedback impulses to the grid, damping the main signal. Since it's feedback, it must be in a low voltage range (I estimate total Vf of the chain between 2 - 5 V). So there's a wide range of small signal diodes (6pc.) to simulate the E1008 (nothing known about this one ?). But actually I don't know the exact working point of this one. Sorry - I was planning on creating different TVS chains to compare listening results, but got not there yet.
cheers

 

[tomas.borgstrom]

It's a bit hard to tell what it says on the schematic. Are they perhaps zener diodes, E100B or Z100B?

 

[Sc]

Manfred Deppe will hopefully forgive me - that's the pic of the original part from his website ....

 

[tomas.borgstrom]

Ok, thats clearly E1008. Does anybody know a substitute?

 

[hugo]

Varicom is coming, but the pair of U73b are there and sound awesome.
Cheers,
H

 

[L091c]

Varicom is coming, but the pair of U73b are there and sound awesome.
Cheers,
H
View attachment 85957

Oww the original panels don't look that bad actually! Does claim a lot of your rack real-estate no?