Hello,
Thank's for the suggestions regarding where to split the psu. It seems that there are different views on the matter (surprise
) I think maybe that if I put the las LC or the las C in the signal chassis is a matter of taste and space. It seems like a good idea that if I put the last C in the signal chassis, also to put a cap on the other side of the cable.
Theo
Thank's for the suggestions regarding where to split the psu. It seems that there are different views on the matter (surprise
) I think maybe that if I put the las LC or the las C in the signal chassis is a matter of taste and space. It seems like a good idea that if I put the last C in the signal chassis, also to put a cap on the other side of the cable.Theo
Hi Thomas.
I look at the pics of you #26 preamp on your webpage. Very nice build
I like your arrangement with the tubes in the small subchassis. I will try to implement that solution.
Theo
Well, to be correct about this, you would use the LL1660/5mA because its primary inductance is sufficiently high for the 26. You could use this as 1:1 in order to keep the gain of the 26. Or as Thomas does, you could use it as a stepdown and lose some of the gain in favour of a better turns ratio. Both are possible and with Lundahl you usually have plenty of choices. But there's no free lunch here - if you lose gain at one point you have to make it up at another point in whatever way you chose. Thomas has some clever and sophisticated solutions. Others including me would just use it in 1:1 to keep the gain.
andy
andy
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Hi!
Sorry to be so persistent on this point. I do not recomment to use the 26 in a linestage with a 1:1 transformer. Although some might get away with a linestage with such a high output impedance it is not generally advisable. With such a high output impedance the length of cable and cable type will become very audible. Which in turn leads many people to the false conclusion that the cables have a certain sound and start swapping cables. Some power amps have low input impedances which will also not work well in this case.
If there is lack of gain in the system this is the wrong way to fix it.
What is the point of a linestage if it is not able to drive long cables and also power amps with low Zin?
If you insist to have the gain, maybe the 26 is better placed into the power amp as input stage.
Most sources have output levels in the range of 2V. Most power amps need much less than 1V for full power out. In such a situation the 18dB of gain a 26can provide are wasted! Instead exchange some of the gain for low Zout. with 4.5:1 the linestage will still have more than 3dB of gain.
Also be aware that the 4.5:1 connection of the LL1660 is by far it's best sounding connection alternative! I even prefer it to the Tango NP8 wired like this. In other ratios the LL1660 is still good, but not excellent.
If you still insist that you need the full gain out of the 26, how about this:
Wire it 4.5:1 and place a 1:4 step up transformer in the power amps input. This way you have all the gain plus the advantage of the possibility to make linestage output and power amp inputs differential and have a balanced conection for superior noise supression!
Best regards
Thomas
Sorry to be so persistent on this point. I do not recomment to use the 26 in a linestage with a 1:1 transformer. Although some might get away with a linestage with such a high output impedance it is not generally advisable. With such a high output impedance the length of cable and cable type will become very audible. Which in turn leads many people to the false conclusion that the cables have a certain sound and start swapping cables. Some power amps have low input impedances which will also not work well in this case.
If there is lack of gain in the system this is the wrong way to fix it.
What is the point of a linestage if it is not able to drive long cables and also power amps with low Zin?
If you insist to have the gain, maybe the 26 is better placed into the power amp as input stage.
Most sources have output levels in the range of 2V. Most power amps need much less than 1V for full power out. In such a situation the 18dB of gain a 26can provide are wasted! Instead exchange some of the gain for low Zout. with 4.5:1 the linestage will still have more than 3dB of gain.
Also be aware that the 4.5:1 connection of the LL1660 is by far it's best sounding connection alternative! I even prefer it to the Tango NP8 wired like this. In other ratios the LL1660 is still good, but not excellent.
If you still insist that you need the full gain out of the 26, how about this:
Wire it 4.5:1 and place a 1:4 step up transformer in the power amps input. This way you have all the gain plus the advantage of the possibility to make linestage output and power amp inputs differential and have a balanced conection for superior noise supression!
Best regards
Thomas
Hi!
The LL1660 is a transformer as the datasheet says. It can be used as a choke, if you connect the primary and leave the secondary floating. You can even wire primaries and secondaries in series for higher inductance but less DC current capabilities. But if you want a anode choke, better use LL1667 or LL1668 which are made for this purpose.
All wiring diagrams are given in Lundahls datasheets.
Lundahl transformers and chokes can be obtained from me BTW as part of my kits.
Best regards
Thomas
The LL1660 is a transformer as the datasheet says. It can be used as a choke, if you connect the primary and leave the secondary floating. You can even wire primaries and secondaries in series for higher inductance but less DC current capabilities. But if you want a anode choke, better use LL1667 or LL1668 which are made for this purpose.
All wiring diagrams are given in Lundahls datasheets.
Lundahl transformers and chokes can be obtained from me BTW as part of my kits.
Best regards
Thomas
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In response to Thomas and the question of 1:1 transformers, he is of course right in saying stepdown for a "commercial" product that may be used with a ss amp, or one with longer cables, but my reasoning is that users who choose to build a 26 preamp will probably:
1) Use a tube amp with a high input impedence
2) Put their units close together so cables are short
I'd add that users who start to use input DHTs like the 26 will be only a short step away from using all DHT amplification, i.e. use something like a 26 in the input to their amps, and maybe something like a 46 as a driver stage. The problem here is none of these tubes have a gain of over 10 so gain is precious. Personally I'm not going to compromise my system by putting something like a 12AX7 in the input of an amp to get gain - you'd lose all the magic of the 26. That would be the weakest link, so why?
So I'm thinking "DHT system" not DHT preamp. Thomas has a good point - put the preamp stage in the amplifier. I'm going to try exactly that - it makes good sense. And Thomas has another good point - the LL1660 will sound better in 4.5:1. My solution to that is simply this - don't use a 26, use a 10Y. Keep the 26 for the input of the amp and direct couple it to the driver stage, like another 10y.
Different ways of doing it - I'm saying this in favour of the idea of using nothing except DHTs. That's what's given me the best sound.
Andy
1) Use a tube amp with a high input impedence
2) Put their units close together so cables are short
I'd add that users who start to use input DHTs like the 26 will be only a short step away from using all DHT amplification, i.e. use something like a 26 in the input to their amps, and maybe something like a 46 as a driver stage. The problem here is none of these tubes have a gain of over 10 so gain is precious. Personally I'm not going to compromise my system by putting something like a 12AX7 in the input of an amp to get gain - you'd lose all the magic of the 26. That would be the weakest link, so why?
So I'm thinking "DHT system" not DHT preamp. Thomas has a good point - put the preamp stage in the amplifier. I'm going to try exactly that - it makes good sense. And Thomas has another good point - the LL1660 will sound better in 4.5:1. My solution to that is simply this - don't use a 26, use a 10Y. Keep the 26 for the input of the amp and direct couple it to the driver stage, like another 10y.
Different ways of doing it - I'm saying this in favour of the idea of using nothing except DHTs. That's what's given me the best sound.
Andy
I want to use 26 preamp with my SS Erno Borbely 75WRMS class A amps & eventually for my Sennheisers HD600 as heaphone amp, can I use it or I have to forget in the applications that I want?
If I understood correctly LL1660 only for line output & LL1667 or LL1668 as anode choke & psu choke.
It's a good idea to use a super shunt regulator like Salas between the psu & the anode choke or will be better only the anode choke?
Every time I'm a little more confused....
If I understood correctly LL1660 only for line output & LL1667 or LL1668 as anode choke & psu choke.
It's a good idea to use a super shunt regulator like Salas between the psu & the anode choke or will be better only the anode choke?
Every time I'm a little more confused....
Merlin,
this is something that you have to try for yourself and decide.
What kind of transformers do you have on hand now?
If you have some volts to spare you can try Salas shunt.
With a 180-0-180 trafo you can go either with choke input and passive filtering and get around 130V B+ or cap input, with a small first cap and depending on your rectifier, and get around 180 - 200V and regulate down with SSHV. These are rough calculations, you can use PSUD2 for more accurate results.
this is something that you have to try for yourself and decide.
What kind of transformers do you have on hand now?
If you have some volts to spare you can try Salas shunt.
With a 180-0-180 trafo you can go either with choke input and passive filtering and get around 130V B+ or cap input, with a small first cap and depending on your rectifier, and get around 180 - 200V and regulate down with SSHV. These are rough calculations, you can use PSUD2 for more accurate results.
Hi!
Thomas
Check the input imoedance of your SS amp. You can simply do this my measuring with a multimeter with the amp switched off. SS amps often have low input impedances like 10-20k. Not good at all with a preamp with a Zout of 7k!
Matter of taste. If you ask 3 people you will get 5 opinions. I prefer the purely passive approach with my DHT linestage. As little SS as possible (just the filament rectifiers)
Thomas
Member
Joined 2006
After my second 26 preamp was complete (see earlier posts ->#622), I also had the 112-A driven 45 amp built, using a pair of Noguchi C-core nano crystal output trans (parafeed), Rod Coleman's filament regs, and lots of trans used as input, loading, and interstage, thus becoming quite heavy as it consists of 11 irons altogether....
Initially I was thinking of building the parafeed 26 preamp for my Linkwitz Pluto, and call it a day, thereafter just enjoy the music, but because I already had certain parts on hand including a few pairs of full rangers, so I decided to build the DHT amp too, and it indeed sounds great
(photo showing 01As, not 112-As)
Member
Joined 2006
The rectifier tube is an 83, thus two switches on panel as one needs to periodically turn on the pre-heat switch first before pumping in the HV....
Voltage more constant as current draw fluctuates I understand.....
BTW, I wondered how different it would be if 10y is used as driver instead of 112-A....
Voltage more constant as current draw fluctuates I understand.....
BTW, I wondered how different it would be if 10y is used as driver instead of 112-A....
Wow - CFT, that's nice work. I bet it sounds wonderful!
I think you'd get a noticeable increase in quality with a 10Y - I'd recommend it. I have some if needed.
Do you use filament bias at all? I'm getting good results with that, assuming you have a really good filament supply like Rod's or some nice chokes for choke input, or for overkill a choke input supply followed by Rod's filament board or another choke as Thomas uses.
Alternatively, battery bias like Kevin uses?
Andy
I think you'd get a noticeable increase in quality with a 10Y - I'd recommend it. I have some if needed.
Do you use filament bias at all? I'm getting good results with that, assuming you have a really good filament supply like Rod's or some nice chokes for choke input, or for overkill a choke input supply followed by Rod's filament board or another choke as Thomas uses.
Alternatively, battery bias like Kevin uses?
Andy
Here's mine - it has a separate power supply. Glow tubes on the left for the input tubes. I use a modular chassis with several interchangeable top plates, with rackmount parts as you can see. All my chassis are 2U and usual rack width. Lundahl transformers underneath.
Andy
Andy
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@vgeorge
Thanks for the input.
@Thomas
Bad news, my SS Borbely amps are less 10K input impedance so can't match with the 26 preamp? can I use the 26 preamp like a headphone amp for Sennheiser HD600?
This only means you can't use it with a 1:1 output transformer or with LC or RC coupled output. With a Lundahl 1660 4.5:1 it will easily drive your SS amp.
Thomas