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Old 8th April 2011, 06:07 PM   #941
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Hi Johann,

I did use the 1692A already, but with lower rp tubes for which it is intended. It is an excellent transformer and sounds good. I have not compared it directly to the 1660 with the same tube. I use it in my LCR phonostage with EC8020 tubes.

These frequency responses are not directly comparable since they are based on different source impedances.

I never considered the 1692A for a linestage with 26 since I always set as a target a Zout of 300 Ohms or lower. With the 1692 your would have about 600 Ohms. I need a low Zout since I drive TVCs with low inductance.

Depends on what you want to drive with the linestage. If a Zout of 600 Ohms is sufficient, the 1692A will work well. I would tend to stick with the 1660 with the 26 however.

I don't know what the DC rating of the PP 1692A is, not sure if it is also ok for 5ma like the 1660PP.

Since you live in Germany: I have 1660 available which you could get from me. If they don't work for you I would take them back. I also have 1692As but only in 18mA.

Best regards

Thomas
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Old 8th April 2011, 08:45 PM   #942
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Thomas - did you ever use the LL1692A in 1:1 as an interstage in an amp? I have the 18ma and want to try this with the 46 and the 10Y

I'm really liking 46>interstage>300b in my amp, with 26 as either preamp or first stage in an integrated chassis where it's direct coupled to the 46, and uses a plate choke. this works really, really well. so right now the 10Y is on the shelf. The 46 is just right for the Hammond 126C interstage and also the LL1660/18mA. they both sound natural and detailed, with lovely tone. Good combinations

andy
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Old 8th April 2011, 11:23 PM   #943
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Hi Andy,

I have not used the 1692A as interstage yet, only as step down in my LCR phono. There are two per channel. One drives the 600 Ohm LCR RIAA and the second at the output for low Zout.

I do use the 1660 in close to 1:1 configuration as interstage in my lower cost amps for example with the 6CB5A tube. While I think it is brilliant as step down lineoutput, it is ok for it's cost as interstage. The Tango NC20 is in a completely different league (also cost wise). I hope to be able to try Pieters (Tribute) interstages soon as well. I'm confident they will also be quite excellent.

As much as I like the Lundahl stuff, for certain applications there are better transformers. Still the 1660 is not bad as interstage and as I said, ok for the cost.

Best regards

Thomas
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Old 9th April 2011, 04:06 PM   #944
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Quote:
Originally Posted by Vinylsavor View Post
As much as I like the Lundahl stuff, for certain applications there are better transformers. Still the 1660 is not bad as interstage and as I said, ok for the cost.
Independent of the price, whatīs in your opinion the best sounding transformer for the #26 in a circuit like Rodīs or kevinkr?

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Old 9th April 2011, 04:15 PM   #945
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Don't eliminate a plate choke and coupling cap as an option! Plate chokes are very suitable for a 26 because of the higher impedance generally available, like 200H or more.

andy
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Old 9th April 2011, 04:22 PM   #946
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Quote:
Originally Posted by andyjevans View Post
Don't eliminate a plate choke and coupling cap as an option! Plate chokes are very suitable for a 26 because of the higher impedance generally available, like 200H or more.

andy

You mean this circuit?

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Thatīs the 2nd question. Witch circuit should i build to get the maximum SQ (independend of the price).
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Old 9th April 2011, 05:03 PM   #947
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Hi!

Quote:
Originally Posted by dvb-projekt View Post
Independent of the price, whatīs in your opinion the best sounding transformer for the #26 in a circuit like Rodīs or kevinkr?
In such a circuit with a step down lineout, which is the right way to go in a linestage, the Lundahl LL1660 is hard to beat, independent of price. This is the application in which the 1660 excels. I have not tried everything on the market. But for me the 1660 wired 4.5:1 performs so well that I stopped thinking about alternatives and rather look for other things to optimize.
Also to you I can offer to send a pair to you, if you don't like them, send them back.

Best regards ... Thomas
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Old 9th April 2011, 05:06 PM   #948
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Hi!

Quote:
Originally Posted by dvb-projekt View Post
Thatīs the 2nd question. Witch circuit should i build to get the maximum SQ (independend of the price).
I would prefer the first circuit for a linestage. I'd however go a step further and use a TVC at the output.

Thomas
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Old 9th April 2011, 07:38 PM   #949
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I can't compare my system with Thomas, because we're trying to do different things. If you want stepdown, Thomas is your man. I use three stages of DHT - 26, 46, 300b and my aim is to put the 26 into the amp chassis and couple 1:1. I'm not interested in stepdown because I don't need a preamp as such, even though I'm actually using the 26 stage in a preamp temporarily. This requires an extra output cap with my plate choke, which I don't need if I put the 26 in the amp and direct couple the first two stages.

I just tried out some different variations. Out of battery grid bias and filament bias I prefer filament bias by a narrow margin. It's cleaner and more immediate. But I should emphasise this is not night and day - they are close. I used Thorsten's version of battery bias which puts the battery in parallel with the cap and a 10M resistor after a 100k pot, which supplies the earth for the battery + side. The filament supply has a choke input which you need to keep the supply clean in filament bias, so you may not get the same results without the choke input.

I then, preferring filament bias, tried out the LL1660/5mA in 1:1 against two Hammond 156C plate chokes in series, giving 300H at 8mA. Output cap there was a teflon FT-2. I preferred the Hammond plate chokes, which may surprise some. Again a very small margin. I didn't use the LL1660/5ma in stepdown for the reasons above, so can't comment on that.

I have now built an integrated amp which has 26 with plate choke direct coupled to 46, interstage coupled to the 300b. so no caps now. That's as far as I've gone and is my preferred listening experience to all of the above. It's not an obvious solution for a free-standing preamp which I guess this thread is all about, but if you move the 26 into the amp chassis it really makes sense to use a plate choke and direct couple to eliminate the cap.

andy

Last edited by andyjevans; 9th April 2011 at 07:43 PM.
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Old 9th April 2011, 07:42 PM   #950
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Hi Andy,

fully agree with your approach! As input stage in a power amp, you can couple the 26 1:1 or similar. That's why my recommendation above refers to the use as a linestage where low Zout is desirable.

But the full potential of a lowZ linestage can only be explored if the opportunity of the drive capability is also used to drive an inductive volume control.

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