vintage tube I/V from the year 1960 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

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 1st August 2005, 11:11 PM   #1
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Talking vintage tube I/V from the year 1960

Today it came to my posession a shure stereo conversion preamplifier model M65E.
2 x ECC83 TFK <> tubes, gain 63dB in microphone mode.
My first idea was to change the circuit to a gain of 2 for use as a playstation buffer.
Second idea was to use it as I/V with a 0,68ohm I/V resistor to amplify to 2V.

Do I need the input coupling caps ?
Can I replace the ECC83 with any of E88CC or CCa ?
If it is a 4 x os DAC, does it make sense to use a transformer after 0,68 ohm ?
Any suggestions to improve the circuit ? Bigger output caps ?

Another thing that came to my mind, I read that opamp works best as buffer with no gain. What if the resistor of a standard op amp I/V is changed so that output will only be 2mV instead of 2V ?
Would that be more like a buffer operation ?



Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 2nd August 2005, 03:13 AM   #2
Banned
 
Join Date: Feb 2002
Location: As far from the NOSsers as possible
Quote:
Another thing that came to my mind, I read that opamp works best as buffer with no gain.
Where did you read that? I can't think of many things that sound worse than an op-amp operated as a buffer.

Jocko
  Reply With Quote
Old 2nd August 2005, 05:57 PM   #3
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Hi

I'd leave the unit as is, don't know about the sound but it looks cute.

For IV conversion other tubes suit better, and you coulod consider using a cathode as input.

cheers
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 3rd August 2005, 07:13 AM   #4
Franz G is offline Franz G  Switzerland
diyAudio Member
 
Franz G's Avatar
 
Join Date: Jun 2004
Location: Bern / Switzerland
Quote:
For IV conversion other tubes suit better, and you coulod consider using a cathode as input.
I attach here a scratch. Something like this idea?

Franz
Attached Images
File Type: gif idee_iv_konversion_mit_gitterbasisstufe.gif (11.7 KB, 1061 views)
  Reply With Quote
Old 3rd August 2005, 08:18 AM   #5
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Quote:
Originally posted by Franz G


I attach here a scratch. Something like this idea?

Franz

Hi Franz,

Looks good !

I have some suggestions to improve the circuit though:

You may use the same (10k) load on the cathode of the second stage, and tie the supplies of both stages together. Ignoring external load, the power supply now sees "no" current swing.

Some people at the forum may object to the use of the cathode follower at all. Taking the signal from first stage anode will result in some k-ohms output impedance. If that is too high, we still need the CF. Improving the CF includes the use of a current source in the tail, which does away the advantage I describe above.....

Once we are on the subject of current source loading cathodes, also the first stage may be equiped with a CS (instead of the 68 ohm): This greatly reduces distortion

succes
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 3rd August 2005, 08:48 AM   #6
X.G. is offline X.G.  China
diyAudio Member
 
X.G.'s Avatar
 
Join Date: Sep 2003
Location: GuangDong China
Quote:
Originally posted by Franz G


I attach here a scratch. Something like this idea?

Franz
your I/V resistor is too higher.....the output volts of yours is very stronger
  Reply With Quote
Old 3rd August 2005, 08:49 AM   #7
diyAudio Member
 
Audiofanatic's Avatar
 
Join Date: Oct 2002
Location: The Netherlands, Utrecht
Default Guido

Quote:
Originally posted by Guido Tent



Hi Franz,

Looks good !

I have some suggestions to improve the circuit though:

You may use the same (10k) load on the cathode of the second stage, and tie the supplies of both stages together. Ignoring external load, the power supply now sees "no" current swing.

Some people at the forum may object to the use of the cathode follower at all. Taking the signal from first stage anode will result in some k-ohms output impedance. If that is too high, we still need the CF. Improving the CF includes the use of a current source in the tail, which does away the advantage I describe above.....

Once we are on the subject of current source loading cathodes, also the first stage may be equiped with a CS (instead of the 68 ohm): This greatly reduces distortion

succes

I agree with Guido for at least 100%.

Best regards,


Audiofanatic
__________________
Be nice to animals.
  Reply With Quote
Old 3rd August 2005, 09:07 AM   #8
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Thanks for replies.
Still the question: Can I replace the ECC83 with ECC88 or 81 or 85 or CCa or do they need other anode voltages ?
I would like to just the box to test tubes go - no go ...

Is the 86ohm in Franz's schematic the I/V resistor ?

Why is it bad to use the circuit as is ?
A 0,68 ohm from Iout to gnd would give very little distortion of a 1541.
The box would act like a preamp.
I have completely no knowledge of tube design, only see that three coupling caps at input, between stages and on output.
  Reply With Quote
Old 3rd August 2005, 10:16 AM   #9
Franz G is offline Franz G  Switzerland
diyAudio Member
 
Franz G's Avatar
 
Join Date: Jun 2004
Location: Bern / Switzerland
Quote:
Still the question: Can I replace the ECC83 with ECC88 or 81 or 85 or CCa or do they need other anode voltages ?
No, as the heather is different: with ECC83 there is 12.6V at pin 4 and 5, at ECC88 it is 6.3V between this pins.

You can find tube datasheets here: http://frank.pocnet.net/sheetsE.html

Quote:
Some people at the forum may object to the use of the cathode follower at all. Taking the signal from first stage anode will result in some k-ohms output impedance. If that is too high, we still need the CF. Improving the CF includes the use of a current source in the tail, which does away the advantage I describe above.....
Yes, the idea of the CF is keeping the output Z low.

Is the conclusion from your statement: don't use current source for the CF?

Quote:
Is the 86ohm in Franz's schematic the I/V resistor ?
Exactly, this is at least the intention. Is the value too high, for a TDA1541A?

The value 86ohm is just calculated out of the tube datasheet.

Quote:
Once we are on the subject of current source loading cathodes, also the first stage may be equiped with a CS (instead of the 68 ohm): This greatly reduces distortion
With a current source instead of the cathode resistor in the first stage, there is a separate I/V conversion resistor needed. Isn't it?

Franz
  Reply With Quote
Old 3rd August 2005, 10:21 AM   #10
Franz G is offline Franz G  Switzerland
diyAudio Member
 
Franz G's Avatar
 
Join Date: Jun 2004
Location: Bern / Switzerland
What about using a LED instead of the first cathode resistor, as I/V converter?

I remember at the triode festival, a speach from Lynn Olson (or was it Morgan Jones?): LED's are very nice low-Z current sources, instead of cathode resistors.

Could this work? Worth a try?

Another question:

Is it recommended to use a coupling cap at the input? Are the 1.3V DC dangerous for the DAC's output?

Franz
  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
Tube amps from vintage RTR's? Brisso57 Tubes / Valves 5 19th February 2009 07:08 PM
Vintage tube tester Cassiel Tubes / Valves 2 9th February 2009 08:04 PM
Vintage tube amp speakers mikje Multi-Way 8 3rd June 2008 05:02 PM
Can anyone help me with 1960's vintage Leak 2 Way Sandwich Speaker System Cure??? slbender Multi-Way 8 7th February 2006 01:32 AM
vintage tube I/V from the year 1960 Bernhard Swap Meet 1 1st August 2005 11:20 PM


New To Site? Need Help?

All times are GMT. The time now is 03:04 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