#26 pre amp - Page 94

vgeorge · 5th April 2011, 04:54 PM

-9v bias and 150v B+ is around 8mA on a 26 tube so I would prefer 135v, in order not to stess the 1660 at 5mA. If you use a SSHV and have the proper sinks, you can adjust easilly. I drop around 90v on mine. I used a plate choke and prefered the 1660 transformer. Mind you that I use 4:1 for the 1660.

dvb-projekt · 5th April 2011, 06:58 PM

Does it make sense to use the amorph version of the Lundahl 1660?

BTW, i don´t find any datasheet of the 5mA version.

andyjevans · 5th April 2011, 07:02 PM

The 5mA version does exist. As far as I know it's the same as the PP version - same gap.

andy

Vinylsavor · 5th April 2011, 07:18 PM

Hi!

Quote:

Originally Posted by Bas Horneman

How about the Lundahl 1680. a Replacement built for the UTC ls-2

I tried the 1680. I prefer the 1660 it sounds and measures better

Thomas

Vinylsavor · 5th April 2011, 07:19 PM

Hi!

Quote:

Originally Posted by dvb-projekt

Does it make sense to use the amorph version of the Lundahl 1660?

Matter of taste. I prefer the standard cores

Thomas

Vinylsavor · 5th April 2011, 07:19 PM

Quote:

Originally Posted by andyjevans

The 5mA version does exist. As far as I know it's the same as the PP version - same gap.

Correct!

dvb-projekt · 5th April 2011, 07:44 PM

Quote:

Originally Posted by Vinylsavor

Hi!

Matter of taste. I prefer the standard cores

Thomas

The 5mA or 10mA version?

Vinylsavor · 5th April 2011, 07:52 PM

Hi!

I have not compared the different cores for all transformers and all currents.

If you intend to run the 26 at 5mA or less and you want to use the transformer only for the 26 linestage, go for the 5mA. If you want to experiment with higher currents or maybe want to try other tubes as well. The 10mA will still work well with the 26. I use the 10mA version in my linestage which can be switched between 26 and 801A. Since the 801A runs at around 10mA, I used the 10mA transformer. I mainly listen with the 801A anyways since I prefer it.

Thomas

Bas Horneman · 5th April 2011, 09:56 PM

Quote:

I tried the 1680. I prefer the 1660 it sounds and measures better

Thanks. Good info to have.

Lauscher · 8th April 2011, 05:00 PM

To Thomas and all others:
Have you tried the LL1692A as line output ?
The PP-Version with 5mA gap has 210Henry. This should be fine for the tube 26. The LL1660-PP has 290Henry.
I was comparing the data sheets of both transformers:
Both with a gap for 18mA in Connection Alt. Q in SE Line Output:
LL1660 Freq. Response: 11Hz - 35KHz
LL1692A Freq. Response: 10Hz - 55KHz
The LL1660 has 4.5 : 1 ratio and the LL1692A has 3.5 : 1 ratio. The 5mA gap version should have better Freq. Response than 18mA.
In this connection Alt. Q the LL1660 has a primary DCR = 1250 Ohm and the LL1692A has primary DCR = 690 Ohm.
On the site of K&K i have found, that the LL1692A has a resonance point that is moved up in higher frequency and has a lower amplitude compared to LL1660. No comment about sound.
What transformer should i use ?
Thank you. Johann

5th April 2011, 06:58 PM	#932
dvb-projekt diyAudio Member Join Date: Feb 2009 Location: Willich, Germany Blog Entries: 31	Does it make sense to use the amorph version of the Lundahl 1660? BTW, i don´t find any datasheet of the 5mA version. __________________ Reference TDA1541A DAC project PCB´s / Tube-I-zator PCB / SSHV-Shunt PCB Stock status in my Blog

5th April 2011, 07:52 PM	#938
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! I have not compared the different cores for all transformers and all currents. If you intend to run the 26 at 5mA or less and you want to use the transformer only for the 26 linestage, go for the 5mA. If you want to experiment with higher currents or maybe want to try other tubes as well. The 10mA will still work well with the 26. I use the 10mA version in my linestage which can be switched between 26 and 801A. Since the 801A runs at around 10mA, I used the 10mA transformer. I mainly listen with the 801A anyways since I prefer it. Thomas __________________ http://vinylsavor.blogspot.com/

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5th April 2011, 04:54 PM	#931
vgeorge diyAudio Member Join Date: Mar 2004 Location: poros island	-9v bias and 150v B+ is around 8mA on a 26 tube so I would prefer 135v, in order not to stess the 1660 at 5mA. If you use a SSHV and have the proper sinks, you can adjust easilly. I drop around 90v on mine. I used a plate choke and prefered the 1660 transformer. Mind you that I use 4:1 for the 1660.

5th April 2011, 07:02 PM	#933
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	The 5mA version does exist. As far as I know it's the same as the PP version - same gap. andy

8th April 2011, 05:00 PM	#940
Lauscher diyAudio Member Join Date: Oct 2007	To Thomas and all others: Have you tried the LL1692A as line output ? The PP-Version with 5mA gap has 210Henry. This should be fine for the tube 26. The LL1660-PP has 290Henry. I was comparing the data sheets of both transformers: Both with a gap for 18mA in Connection Alt. Q in SE Line Output: LL1660 Freq. Response: 11Hz - 35KHz LL1692A Freq. Response: 10Hz - 55KHz The LL1660 has 4.5 : 1 ratio and the LL1692A has 3.5 : 1 ratio. The 5mA gap version should have better Freq. Response than 18mA. In this connection Alt. Q the LL1660 has a primary DCR = 1250 Ohm and the LL1692A has primary DCR = 690 Ohm. On the site of K&K i have found, that the LL1692A has a resonance point that is moved up in higher frequency and has a lower amplitude compared to LL1660. No comment about sound. What transformer should i use ? Thank you. Johann