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Project Specific Discussions => Preamplifiers => Topic started by: [silent:arts] on July 16, 2017, 11:39:02 AM

Title: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on July 16, 2017, 11:39:02 AM
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 (http://www.silentarts.de/DIY/V672X/V672a_Schematic.png) | original data-sheet (http://www.silentarts.de/DIY/V672X/V672a_Data.pdf) ]

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

(http://www.silentarts.de/DIY/V672X/V672X-Front.jpg)(http://www.silentarts.de/DIY/V672X/V672X-Profile.jpg)
(http://www.silentarts.de/DIY/V672X/V672X-Side.jpg)(http://www.silentarts.de/DIY/V672X/V672X-Top.jpg)

Documents:

V672X Schematic (http://www.silentarts.de/DIY/V672X/V672A_rev03-Schematic.pdf)
V672X PCBs (http://www.silentarts.de/DIY/V672X/V672A_rev03-PCBs.pdf)
V672X Parts List (http://www.silentarts.de/DIY/V672X/V672A_rev03-PartsList.pdf)

Full Kits are available in the White Market (https://groupdiy.com/index.php?topic=39570.0)
Title: Re: V672X
Post by: kante1603 on July 16, 2017, 12:13:47 PM
Wow,beauties they are!
The german writings are cool,hahaha....


Congrats Volker,


best regards,


Udo.
Title: Re: V672X
Post by: mhbunch on July 16, 2017, 06:21:54 PM
Looks amazing! When will they be available?
Title: Re: V672X
Post by: [silent:arts] on July 22, 2017, 11:09:04 AM
Schematics, PCB overlays and parts list added to the first post
Title: Re: V672X
Post by: kante1603 on July 22, 2017, 11:41:04 AM
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.
Title: Re: V672X
Post by: [silent:arts] on July 22, 2017, 12:46:02 PM
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
Title: Re: V672X
Post by: kante1603 on July 22, 2017, 12:52:54 PM
Great,thank you very much indeed Volker!


Best regards,


Udo.
Title: Re: V672X
Post by: Potato Cakes on July 24, 2017, 10:59:12 AM
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
Title: Re: V672X (Telefunken V672 in GDIY51X format)
Post by: [silent:arts] on July 30, 2017, 05:23:48 AM
Full Kits are now available in the White Market (https://groupdiy.com/index.php?topic=39570.0)  8)
Title: Re: V672X (Telefunken V672 in GDIY51X format)
Post by: kante1603 on August 21, 2017, 03:28:35 PM
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.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on August 22, 2017, 01:41:51 PM
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
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on August 22, 2017, 01:47:39 PM
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
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on August 22, 2017, 02:11:01 PM
Awesome Volker,


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


Best regards,


Udo.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on August 24, 2017, 07:02:26 AM
You are welcome Udo.

Added the Service Manual I mainly used to design the V672X to the Technical Documents (https://groupdiy.com/index.php?topic=45156.msg845549#msg845549) Section.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on August 24, 2017, 02:32:50 PM
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.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on August 25, 2017, 10:29:42 AM
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.

Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on August 25, 2017, 10:30:47 AM
…and here while phase checking etc. and listening:
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on August 26, 2017, 05:07:05 AM
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?
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on August 26, 2017, 06:15:52 AM
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.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: leadbreath on August 26, 2017, 09:16:57 PM
Love these amps!!! Glad to see other people share the love of these units... :D
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: fragletrollet on September 04, 2017, 11:13:10 AM
What settings would be used for line levels, if suitable? Would any of the gain settings be close to unity?
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on September 04, 2017, 11:29:25 AM
What settings would be used for line levels, if suitable? Would any of the gain settings be close to unity?

You would choose
S1 =  dB Gain: 41dB / R Gegenkopplung: 12K
S5 = dB Input: -40dB / R Eingang: 24K
The trimmer R26 should be fine to adjust that one dB difference
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: fragletrollet on September 05, 2017, 03:55:48 AM
Cool! Would be nice if the frontpanel reflected this, but i wont complain  ;D
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on September 05, 2017, 04:18:16 AM
Since I do individual front panels we can add this to yours, no problem :-)
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on September 05, 2017, 04:28:40 AM
Hi Volker,


excuse me chiming in,but I think what fragletrollet meant was writings in decibels instead of resistances?


Best,


Udo.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on September 05, 2017, 12:02:20 PM
Everything is possible, international dB version attached  :)
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on September 05, 2017, 12:28:27 PM
Hahaha...very nice indeed ,but I'll stick to german  ;D


Udo.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: fragletrollet on September 06, 2017, 03:04:49 AM
Nice!! Someone needs to get himself a +24v rack ;)
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: Potato Cakes on September 09, 2017, 10:16:40 AM
Hahaha...very nice indeed ,but I'll stick to german  ;D


Udo.

I second Udo. It really adds to the uniqueness of this project. I don't recall anyone having issues with German words used on vintage Telefunken gear.

Just my two cents.

Keep 'em coming, Volker!

Thanks!

Paul
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on September 15, 2017, 07:40:36 AM
Just want to show you two custom front panels I did today.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kml23956 on December 28, 2017, 05:40:41 PM
Volker,  The radial diodes d41 -d44. Which way is negative? How do I put them in?
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kante1603 on December 29, 2017, 12:39:42 AM
Hi,
look here at the lower left side of the page:
http://www.silentarts.de/DIY/V672X/V672X_rev03-PCBs.pdf (http://www.silentarts.de/DIY/V672X/V672X_rev03-PCBs.pdf)
The black bands of the diodes show upwards.


Best regards,


Udo.
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: [silent:arts] on December 29, 2017, 03:16:49 AM
Like Udo said. All diodes up  :)
Title: Re: V672X (Telefunken V672a in GDIY51X format)
Post by: kml23956 on December 29, 2017, 10:32:22 AM
Thank you. I could not figure that one out. Everything else is well marked. The thing is designed to be built like a tank!