V672X (Telefunken V672a in GDIY51X format)

[silent:arts] · Jul 16, 2017

I would like to present you a new member in my German Legends family, the V672X

based on the Telefunken UNIVERSAL AMPLIFIER V672a,
with improved output driver and added mic-pre features,
switchable series resistance (input impedance) and
switchable feedback resistance (gain)

[ original schematic | original data-sheet ]

NOTE: the V672X is NOT API500 COMPATIBLE, a GDIY511 Rack is required

Documents:

V672X Schematic
V672X PCBs
V672X Parts List
Calibration Instructions
#V672X on Instagram

Full Kits are available in the White Market

kante1603 · Jul 16, 2017

Wow,beauties they are!
The german writings are cool,hahaha....

Congrats Volker,

best regards,

Udo.

mhbunch · Jul 16, 2017

Looks amazing! When will they be available?

[silent:arts] · Jul 22, 2017

Schematics, PCB overlays and parts list added to the first post

kante1603 · Jul 22, 2017

[silent:arts] said:
Schematics, PCB overlays and parts list added to the first post

Excellent Volker!
May I ask a question:The parts list says that Ü1,Ü2 and Frontpanel "....are not included any kit....".
Will you offer them (I guess most of us don't have a good access to Haufe transformers,and the panels look really nice)?

Thank you in advance,

Udo.

[silent:arts] · Jul 22, 2017

Hi Udo,

changed that to "* not included in the parts kit".
I will offer full kits.
However, it is easier for me and my stock inventory software to have the transformers and front panels as separated items.
Some people might have the transformers anyway (or V672D cards with broken thick film IC),
and the front panel can be either in silver or black.

Kind regards
Volker

kante1603 · Jul 22, 2017

Great,thank you very much indeed Volker!

Best regards,

Udo.

Potato Cakes · Jul 24, 2017

When I come out from under the pile of things I have to finish building, I'd be interested in metal work, boards, and transformers.

Phenomenal job as always.

Thanks!

Paul

[silent:arts] · Jul 30, 2017

Full Kits are now available in the White Market 8)

kante1603 · Aug 21, 2017

Hello Volker,

about adjusting,C8 is for symmetry trim,right?
Are there any rules or recommendations how to set the fine gain and the filters?

Thank you in advance,

Udo.

[silent:arts] · Aug 22, 2017

Hi Udo, yes C8 is the input symmetry trim.

For calibrating we use the original V672D Meßvorschrift 8)
For the V5672 and V672X I adapted it like followed:
(for all steps my generators Zout is set to 200R, and analyzer Zin to 600R)

S1 = dB Gain: 62dB / R Gegenkopplung: 240K
S2 = LPF OFF / Tiefpass Überbrückt to left position (on)
S5 = dB Input: -20dB / R Eingang: 2k2

GAIN ADJ R26:
Generator = 1kHz -40dBu
Set R26 to measure +2dBu

HF ADJ R37:
Generator = 15kHz -40dBu
Set R37 to measure +2dBu

LF ADJ R29
Generator = 40Hz -40dBu
Set R29 to measure +2dBu

[silent:arts] · Aug 22, 2017

For C8 input symmetry you need a special cable.

(generators Zout is set to 200R, and analyzer Zin to 600R)

S1 = dB Gain: 38dB / R Gegenkopplung: 5K6
S2 = LPF OFF / Tiefpass Überbrückt to left position (on)
S5 = dB Input: -20dB / R Eingang: 2k2

Generator = 15 kHz -5dBu
Adjust C8 for lowest possible output

kante1603 · Aug 22, 2017

Awesome Volker,

thank you very much!
Will order very soon (if I may of course).

Best regards,

Udo.

[silent:arts] · Aug 24, 2017

You are welcome Udo.

Added the Service Manual I mainly used to design the V672X to the Technical Documents Section.

kante1603 · Aug 24, 2017

Thank you for the docs Volker!

Two kits received this afternoon,parts checking time now (most time-consuming thing,I look forward to assembly) ;D
The kit looks very nice and professional,the frontpanels are awesome!

Best regards,

Udo.

kante1603 · Aug 25, 2017

Done!

Finished assembly and adjusting/trimming today,all went very well.An easy build,well prepared (Grayhills came with stopping pins set already!) and complete up to the last washer.
Haven´t heard too much,but what I heard was excellent sounding.
Did first tests with some music via (Bo´s) active D.I.s as well as some microphones I had here at home.
Sm57 was easy too bring up to a useful level at just speech,even an SM7b worked good enough when raising speech level.With a Cloudlifter the SM7b sounded very very nice.
CMC6+MK4 was fantastic.

Addendum:
Heard it with U87 and U87Ai on vocals today,as expected it sounded excellent.
I can only recommend building them.Not only is it easy to do -I built two in just one day-but the kit price is on the more lower side compared to other kits in this sound range (290 Euros+VAT).

A massive thank you to Volker for another great project!

Best regards,

Udo.

P.S.:As usual the pics of proof,here while CMRR-trimming:

Edit:Addendum added.

kante1603 · Aug 25, 2017

…and here while phase checking etc. and listening:

[silent:arts] · Aug 26, 2017

Fast as always my friend

Thanks for your kind words Udo.

Can you tell us something about your interesting looking module screws in the 2nd pic?

kante1603 · Aug 26, 2017

Hi Volker,

those are 4/40-thumbscrews,they're just temporary because a)we are in metric land and I had no fitting silver countersunk types here and b) they are usable without a screwdriver ;D
They look very nice on black facias,I have them from Cemal ("sahib") for my TAC gear which make them look even better,hahaha......

Cheers and greets to Berlin,

Udo.

leadbreath · Aug 26, 2017

Love these amps!!! Glad to see other people share the love of these units...

V672X (Telefunken V672a in GDIY51X format)

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