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Old 16th March 2011, 11:51 AM   #21
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Quote:
Originally Posted by vgeorge View Post
Andy,

I used ll1667 25mA with more than 200H inductance and cap output in my 26 pre.
Switching to ll1660pp 4:1 improved the sound considerably.
I' m using battery bias and Rod' s fillament supply.
I'm currently using a LL1660/5mA in 1:1 in my 26 preamp. I have filament bias right now but I could also use battery bias at some point - I tried that in my 10y preamp and it sounded fairly similar. Anyway, I'm loving the LL1660.

So I have a question for the 26 community. There are more choices in plate chokes for the 26 than there are in output/interstage transformers.

What is available besides the LL1660 in transformers? I can't think of anything obvious, and some builders of 26 preamps might want - for example - to consider the availability of cheaper transformers at the expense of a compromise (big or small) in sound. Edcor do a 15K:15K

Other builders may want something more sophisticated - nickel, amorphous etc.

Any ideas for transformers the 26 would be happy with? I'm guessing at least 150 Henries

Andy
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Old 16th March 2011, 01:21 PM   #22
kevinkr is offline kevinkr  United States
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On the vintage side both UTC HA-133 and UTC A-25 15K:600 work well.

Electra-Print will custom build OPTs for the 26/01 as well.

Magnequest made excellent 10K:600 and 20K:600 OPTs. (Both have sufficient primary inductance for use with a 26 or 01)

Hashimoto HL-20K-6 (20K:600) for 26/01

Hashimoto HL-10K-6 (10K) which is probably a better match for the 12/112 due to its primary inductance of 95H.

Sowter doesn't appear to make anything with sufficient inductance for use with a 26.

AE might be persuaded to custom make an appropriate transformer, but does not appear to offer anything directly suitable.

In the Lundahl line the LL1660/10mA appears suitable when configured as a 4.5:1 step down.

Bartolucci line stage models A, B and F could also be used. (While my experience with Bartolucci is limited, the few I have worked with were excellent.)

Trafomatic may also make suitable transformers, but lists none on their site so they would have to be contacted. (They also make excellent transformers)

Iso Tango NP-126 may be suitable, no idea what the primary inductance is however.

James, and Tamura would be other likely sources as well.

None of these are particularly cheap either...

Edcor (a custom type, not OTS) or Electra-Print are likely to be the most economical choices.
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Last edited by kevinkr; 16th March 2011 at 01:44 PM.
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Old 16th March 2011, 02:55 PM   #23
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Wow!! That's really useful. I'm shooting for 1:1 and short leads to the amp, or even put the first stage in the amp itself, simply because I only use DHTs with low mu and so gain is too precious to sacrifice. I know Thomas and yourself and conventional practice favour stepdown and higher mu tubes in the amp, but that's not the application I need here, which effectively is an interstage. I'm probably happy with the LL1660/5ma but I'm really curious about alternatives.

This may then be a question of a custom made unit if it's 1:1 since most of the above list are 600 ohm output. You wouldn't normally use a 26 as a driver, so interstages rarely go up that high in Henries.

You can't help getting a bit excited at the Japanese exotica, though....... Mmmmm. But as you say, expensivo.

Andy
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Old 16th March 2011, 03:13 PM   #24
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by kevinkr View Post
On the vintage side both UTC HA-133 and UTC A-25 15K:600 work well.

Electra-Print will custom build OPTs for the 26/01 as well.

Magnequest made excellent 10K:600 and 20K:600 OPTs. (Both have sufficient primary inductance for use with a 26 or 01)

Hashimoto HL-20K-6 (20K:600) for 26/01

Hashimoto HL-10K-6 (10K) which is probably a better match for the 12/112 due to its primary inductance of 95H.

Sowter doesn't appear to make anything with sufficient inductance for use with a 26.

AE might be persuaded to custom make an appropriate transformer, but does not appear to offer anything directly suitable.

In the Lundahl line the LL1660/10mA appears suitable when configured as a 4.5:1 step down.

Bartolucci line stage models A, B and F could also be used. (While my experience with Bartolucci is limited, the few I have worked with were excellent.)

Trafomatic may also make suitable transformers, but lists none on their site so they would have to be contacted. (They also make excellent transformers)

Iso Tango NP-126 may be suitable, no idea what the primary inductance is however.

James, and Tamura would be other likely sources as well.

None of these are particularly cheap either...

Edcor (a custom type, not OTS) or Electra-Print are likely to be the most economical choices.
Dave Slagle, who posts here sometimes, also makes custom chokes and transformers. Made some massive chokes for a 801 parafeed amp of mine. They measure and sound good.

Sheldon
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Old 16th March 2011, 03:24 PM   #25
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Sheldon View Post
Dave Slagle, who posts here sometimes, also makes custom chokes and transformers. Made some massive chokes for a 801 parafeed amp of mine. They measure and sound good.

Sheldon
I'll second that, don't know how I forgot Dave...
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Old 16th March 2011, 05:11 PM   #26
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Hi!

For interstage, the Tango NC20F works nicely. Although it has surprisingly low inductance I got excellent results with it, especiaqlly in the bass. It is very expensive but among the best interstages available today and worth it's cost

Thomas
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Old 16th March 2011, 08:46 PM   #27
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Hi Thomas,

Did you use the Tango with a 26 tube?

Andy
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Old 16th March 2011, 10:09 PM   #28
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Hi Andy,

yes I used it with a 26 in this amp:

VinylSavor: Making of an 45 / 2A3 amplifier

Thomas
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Old 17th March 2011, 12:40 AM   #29
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Hmmm. Interesting. I was thinking 150H was the minimum for a 26.

I just hooked up two 156C Hammonds in series as plate chokes. Twice 150H should give 300H I assume. Sounds remarkably pleasant for a cheap solution. Doesn't quite have the magic of the LL1660 which is a bit special, but nevertheless the sound is all there - clean and clear. I used battery bias. Output caps were Teflon FT-3. I'll also try some Russian 0.1 silver mica when I can. Haven't compared those directly and that would be worth knowing.

andy
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Old 17th March 2011, 08:19 AM   #30
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Hi Andy,

all Tango Transformers have surprisingly low primary inductance for the intended applications yet sound remarkably good, especially in the bass.

Generally I also prefer to have higher inductance. Especially in the linestage I want the roll off not to start too early.

I also like the LL1660 a lot. Although it really sounds best in 4.5:1
If you don't have to adjust your volume pot all the way up for average listening and have some margin in gain, I do encourage you to just try this. It is just a few solder joints and reversed in a few minutes. I'm sure you will be pleasantly surprised! See I try hard to convert you on this point

Coming back to the NC20: This one is sound wise in another league alltogether! However just 1:1, so only for interstage use.

As step down transformers I also tried Tango NP8. Here I clearly prefer the Lundahl 1660/4.5:1! Even in my most elaborate directly heated linestages I use the Lundahl.

Best regards

Thomas
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