Help support VinylAudio.net today - become a Premiere Member! Look for 'Paid Subscriptions' in your profile!
Hello Guest
  • Sign up for free and join our community.
Fred Nachbaur's high precision tube phono preamp
6 Replies
26562 Views
0 Members and 1 Guest are viewing this topic.
January 09, 2012, 03:19:09 PM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
I was looking for a good quality tube phono preamp and I stumbled upon this:
http://www.dogstar.dantimax.dk/tubestuf/sapinde1.htm
It looks very interesting! :D It seems to me well designed and quite different from most tube preamps. Check out the sound sample. What do you guys think?
Pro-Ject RPM 5.1 Denon DL-110 Sony BDP-S373 Fred Nachbaur High Precision Tube Phono Preamp Nuova Elettronica FET preamp Nuova Elettronica IGBT power amp Mission 701 Clicktronic cables Norstone Loudspeaker Cable


January 24, 2013, 07:27:56 AM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
It's complete! I need a wooden outer housing to enclose the metal inner chassis, but everything else is done.
The first testing was OK: everything worked, it is just a bit low on voltage because one of the transformers supplies slightly less than the nominal 117 Volts, but the volume is good. There's a barely audible hum in the background, possibly due to not perfect ground solderings, I'll investigate that.
Soundwise I will judge it after the break in period of around 300 hours; the first listen was hardly indicative. It sounded very closed in and muddled, not airy at all. I guess the coupling capacitors need to open up. I'm going to buy Intertechnik Audyn Caps Plus if the current capacitors won't satisfy me.
Compared to my solid state preamp, it's quite soft, but equally fast. I didn't notice any loss in the highs; bass is more recessed and soft, but definitely more meaty. The mids are more pronounced, and the thing that surprised me the most, is the added dept in the sound stage: with my solid state amp it's like you are in the first row or directly on the stage, while with this phono preamp you are almost in the middle of the hall among the public.
« Last Edit: January 24, 2013, 10:45:40 AM by lshin80 »


February 08, 2013, 03:20:27 PM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
Now, it may look crappy, but it sounds like heaven  ;)
The case is an old multipurpose pre-drilled chassis my dad had since the '60s. The circuit looks messy, but it was built not to use long pieces of wire, in order to avoid any possible noise or hum. There is a light hum in the background, so we'll have make a central ground (star) point. Otherwise, it has no issue. It is possible I will get a better looking steel chassis, so consider this as the working prototype.

Pic #1 - front view.
Pic #2 - rear view with power switch, AC input, fuse holder, line in & out.
Pic #3 - tubes detail: 2x ECC83 Philips Miniwatt, 1x ECC81 Siemens.
Pic #4 - circuit overview.
Pic #5 - power supply detail. F&T and Hitano Electrolythics. 2x NOS Wima TFF series caps. Ultra fast rectifier diodes.
Pic #6 - input and output caps. Bottom: 2x NOS Russian KBG series paper in oil caps. Top: Solen Fast Caps bypassed by KBGs (Solens will be replaced by Intertechnik Audyn caps.)
Pic #7 - RIIA circuit detail. 4x Icel MPL series caps.


February 11, 2013, 01:52:19 PM
    • VinylAudio.net
  • BSD2000
  • Administrator
  • Trade Count: (2)
  • Posts: 623 Male
    Offline
    Pennsylvania Send PM
    • Share Post
I think it looks good!  :)

I wish I could hear it. This is giving me the bug to want to build one.   :D

First, I need to buy a new set of tubes for my phono preamp. One of the tubes went bad last year and I'm using a spare. They really should be replaced all at once with all matched tubes since the left channel has slightly higher gain than the right.  :(
Rega P25 Zyx Omega G Zyx R100H Audio Research PH5 Denon DP-52F Denon DL-103D Burson HA-160 Sennheiser HD-650 and HD-800


February 12, 2013, 07:22:09 AM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
The Intertechnik caps have arrived. They are now plugged to a frequency generator for the break in. A frequency sweep of 100 Hz to 3 kHz @ 10 Volts is applied. Next step will be a sweep of 1 Hz to 100 Hz. I expect much from these caps, especially when compared to the Solen Fast Caps, which I feel to be the weak spot in the audio path. Well' see :)

Since we have to remake the ground point, we'll possibly have to dismantle everything. That could be a pretext to get a better looking chassis. I was thinking to this:
http://www.hammondmfg.com/dwg20.htm
in the black version:
http://www.hammondmfg.com/jpeg/1441BKU_B.jpg
This chassis would resolve the problem of a wooden case, there is in fact this version which looks great:
http://www.hammondmfg.com/dwg20CWW.htm
However that would cost almost 60 Euros, while the simple steel version costs 10 Euros...so I could get the simple version and then apply two pieces of unused wood that I've got.

What tubes do you need? I looked for a long plate Philips ECC83 to couple with the one I've got (no matter if they're not matched, my solid state preamp has independent volume controls for each channel), but nothing under the 100 Euros mark :(


April 26, 2013, 03:44:26 PM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
New chassis:
[attach=1]

Also new capacitors for both the phono preamp and the solid state amps:
(lower left corner: teflons, for the RIAA circuit; others: PIO and metallized PIO for the solid state amps)
[attach=2]


May 16, 2013, 11:48:42 AM
  • lshin80
  • Full Member
  • Trade Count: (0)
  • Posts: 196 Male
    Offline
    Planet Earth Send PM
    • Share Post
Finally, the last caps have arrived (these things are HUGE!); they will go in my solid state preamp. They are now undergoing the break in; meanwhile I'll reassemble the phono preamp in the new chassis. Once the phono preamp is rebuilt, I'll change all the coupling caps in the solid state preamp and power amp.

Also I got 5 metres (15 feet) of pure copper oxygen free 6 mm section loudspeaker cable to replace the cheap cable I've been using so far. This will be the last upgrade in my HI FI system.



Share via delicious Share via digg Share via facebook Share via linkedin Share via pinterest Share via reddit Share via stumble Share via tumblr Share via twitter

xx
Presonus Studio Channel Tube Microphone Preamp

Started by BSD2000 on Professional Gear

0 Replies
1765 Views
Last post September 08, 2014, 07:13:06 AM
by BSD2000
xx
Audio-Technica CN5625AL Phono Cartridge and Stylus - $19.76!

Started by BSD2000 on Online Deals

0 Replies
5097 Views
Last post March 13, 2014, 08:37:50 PM
by BSD2000
clip
New: Tascam DA-3000 High-Res Recorder

Started by BSD2000 on Vinyl Ripping and Archiving

3 Replies
19086 Views
Last post August 01, 2014, 10:10:38 AM
by GoodVinylLover
xx
U.S. Vinyl Album Sales Hit Nielsen Music-Era Record High in 2017

Started by BSD2000 on Vinyl Grooves

0 Replies
7766 Views
Last post January 07, 2018, 04:21:36 PM
by BSD2000
 


Users found this pages searching for:

web
stats