Marantz preamp - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 20th September 2003, 01:28 AM   #11
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
but it shouldn't be too hard to work an active RIAA eq into the NFB (hopefully).
I may just be in a pessimistic mood but I don't think it will be all that easy...

Quote:
So this should sound ok as line level pre?
According to the press it seems to...

It appears as an awfully and overly complicated linestage to me with way too much gain but so what, it's only my opinion anyway...

Cheers,
__________________
Frank
  Reply With Quote
Old 20th September 2003, 01:32 AM   #12
Hamish is offline Hamish  Australia
diyAudio Member
 
Hamish's Avatar
 
Join Date: Nov 2002
Location: Brisbane, Australia
And i appreciate your opinion, Frank. I'll try and find something a little simpler. No recommendations for a phono stage?
  Reply With Quote
Old 20th September 2003, 01:43 AM   #13
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
No recommendations for a phono stage?
Sure, recommendations are easy enough to hand out....

Actually producing a good phono stage is another chapter entirely....
MC compatible ones are a living nightmare if you want, like myself stubbornly adhere to valves...

I've got a thousand ideas floating in my mind none of which is perfect but perfection is not of this world anyway...he, he...

Cheers,
__________________
Frank
  Reply With Quote
Old 20th September 2003, 01:55 AM   #14
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Quote:
Originally posted by Hamish
Any suggestions then? i like this one because the 12ax7's are pretty easy to get and i have a few here anyway. I want a REALLY good phono stage (but not too complicated). That's my main aim.

IMO/IME, you'll not get a really good phono stage with 12AX7's. And not with feedback either.

Before I recommend anything, how much gain do you want, and what sort of input voltage are you thinking of using? This will largely determine what sort of topologies will work.

As for tube availability, do you have a credit card? If so, then tubes are not an issue to obtain. There are a number of US vendors for instance that will have a few tubes to Brisvegas within 7 working days (I'm in the bush and that's how long they take to me) and the postage is decent. Europe takes a bit longer. There are some in Oz too like David Crittle at Retrovox whom I'd highly recommend.

As an example, a simple resistive loaded 6BX7 or 12B4A would be a hell of a lot better than the 7C for a linestage, and the tubes are 7 and 3 USD respectively for real NOS stuff. One stage and no NFB, and for a further improvement use a Lundahl choke, or a CCS to make a mu stage.
  Reply With Quote
Old 20th September 2003, 01:56 AM   #15
Hamish is offline Hamish  Australia
diyAudio Member
 
Hamish's Avatar
 
Join Date: Nov 2002
Location: Brisbane, Australia
Thanks Frank. If you think of any "less than ideal" preamps that might do the trick, let me know

I'm not keen enough yet for a MC. I'm just about to send a Grace F-9 down to Garrot brothers for a rebuild, so i'll be using a MM for a while to get my money's worth.

I'm not really after perfection in the linestage, in fact that is probably the last thing i want. I just want something that's not too hard as a first project, and musical. That's all. I got my first taste of tubes with an Akai M-8 i picked up for next to nothing, and now i want more!

Thanks again, Frank.

Hamish
  Reply With Quote
Old 20th September 2003, 02:12 AM   #16
Hamish is offline Hamish  Australia
diyAudio Member
 
Hamish's Avatar
 
Join Date: Nov 2002
Location: Brisbane, Australia
Thanks for the info, Brett.

So do you have any schematics for the 6BX7 or 12B4A? I still don't really understand them enough to design my own.
  Reply With Quote
Old 20th September 2003, 02:39 AM   #17
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Quote:
Originally posted by Hamish
Thanks for the info, Brett.

So do you have any schematics for the 6BX7 or 12B4A? I still don't really understand them enough to design my own.
Here's a setup for a 12B4A in a line stage.


B+ 300V
Ia 25 - 30mA
Ranode = 6 - 7K
Vg -12.5 (@ 30mA / 6k)
Rk 410R
rp = 950R
u = 6.4

6k anode load will dissipate 5.4W, so I'd suggest 2 x 12W Mills 12k in //

Bypassed, gain will be 5.5 and Zout 820R. Unbypassed 3.8 and 2k4.

A similar design was discussed in this previous thread.

12B4A Linestage & PSU

Let me know what you have in the way of power supply iron, transformers and chokes, as well as caps and I'll tweak the values for you.

I may also have some spare 12B4A's here, and if not, I'm going to order a few other tubes from the US next week and could add some in if you like.
  Reply With Quote
Old 20th September 2003, 02:50 AM   #18
Hamish is offline Hamish  Australia
diyAudio Member
 
Hamish's Avatar
 
Join Date: Nov 2002
Location: Brisbane, Australia
As far as power supply goes, i've got a 260-0-260 transformer i nicked from an old AWA receiver (with a 6x4 rectifier). I haven't got anything in the way of caps yet (there are some, but they're no doubt too old to be used). I was just going to run up a supply on PSU designer with a simple RC filter to keep things cheap and cheerful. Chokes seem to be a shade pricey.

I got a few tubes out of that receiver if they're of any use: some 6au6's, a 6be6, some 6aq5's, and a 6n8 (an oscillator i think). They're all old AWA tubes so i don't know how good they are...............
  Reply With Quote
Old 20th September 2003, 05:28 AM   #19
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Brett's already talked you out of the 12AX7 linestage, but here, for reference, is the RCA phono stage. My buddy built one (with a power supply bigger than some power amps) and its not c^$%. At least the RIAA is all figured.

dave
Attached Images
File Type: gif chris_phono.gif (9.0 KB, 394 views)
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 20th September 2003, 05:31 AM   #20
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
And a bit more modern one... found at Vacuum State Electronics.

Click the image to open in full size.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Marantz 7 Preamp Audiohifi Tubes / Valves 12 8th May 2010 09:38 PM


New To Site? Need Help?

All times are GMT. The time now is 03:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2