Andy,
I just copied from post #7 attachment, or did I miss something there ??
Albert
Yes, absolutely!
I have seen several preamps with Russian silver micas in this position.
But I am still wondering about the voltage requirements?
Hi Albert,
I Don't use regulators in my DHT linestages. I stick with strictly passive filters for both B+ and filament. With the amount of filtering you already have, do you really need a reg in addition? If you insist to use this reg I'd consult the developer of it.
Best regards ... Thomas
I Don't use regulators in my DHT linestages. I stick with strictly passive filters for both B+ and filament. With the amount of filtering you already have, do you really need a reg in addition? If you insist to use this reg I'd consult the developer of it.
Best regards ... Thomas
Thomas,
Do you mean the psu I have on my attachment is good to aim the purpose for both channels ??
Albert
Thomas,
I have to build the Sala's reg. from scratch. Certainly would try separate LC stage, but I have to buy one more 30H choke that.
Albert
Hi Albert,
to use the Salas HV-Shunt reg. is realy a good idea!
I use his circuit for the B+ of my Tube-I-zator module, a SRPP output stage for I-out DAC´s.
It has an extreme low Z-out an sounds fantastic.
Hi Albert,
to use the Salas HV-Shunt reg. is realy a good idea!
I use his circuit for the B+ of my Tube-I-zator module, a SRPP output stage for I-out DAC´s.
It has an extreme low Z-out an sounds fantastic.
dvb-projekt,
Are you suggesting me to try the attached..
Albert
Attachments
Hi!
Up to you how to do it. I always encourage newbies to try simpler circuits first, of which they have a better chance to understand it. A reg is much more difficult to understand as a beginner, while a passive filter is easy to get a grasp upon.
Best regards
Thomas
Up to you how to do it. I always encourage newbies to try simpler circuits first, of which they have a better chance to understand it. A reg is much more difficult to understand as a beginner, while a passive filter is easy to get a grasp upon.
Best regards
Thomas
Albert, here is my take on the DHT line stage.
I agree with many here that a step-down transformer has many advantages for driving cables and Power-Amp inputs.
But, the transformer is a high cost component - though they should last a lifetime. High quality transformers are ESSENTIAL - you would be better served with op-amps like the OP627 than to waste time with cheap trafos.
My personal experience is with SOWTER transformers, and so I know that these are the highest possible quality, and will last forever. For Line use, thei range is here:
PRE AMP OUTPUT TRANSFORMERS
The 5:1 9040 offers interesting possibilities, since it can perform Line duty with SE stages all the way up to 45mA, meaning that PX4 and 2A3 can be tried at the heavy end, or the 26 at the higher-Rp range.
With a 2A3, PX4 or 45 you can easily drive 600-Ohm lines, long cables, or hard-to-please power amps. Even with 600 Ohm, the valve will only see a load of 15K with the 9040 trafo, meaning you will get ultra-low distortion.
On the other hand, you could drive 10K loads with shorter cables using the 26, again with ultra low distortion.
This versatility appeals to me. You pay a high price for your trafo, and have the rest of your life to try to wear it out. Why paint yourself into a corner and only have one choice of valve to use? The 2A3 and others are still in production, unlike the 26, so planning to replace your 26 can be built into the line stage design.
The rest of the schematic is straightforward. Alkaline battery bias is shown - very quick to implement with a 26. with 2A3 regular fixed bias from a dc supply - or multiple alkaline batteries can be used.
The B+ should be choke input, for sure. If you have some more chokes, then build the line stage with passive filtering. When you have enjoyed it for a while, build a Salas HV and insert it as shown. With a 26, use around 180V.
For any DHT linestage, you need a proper dc heating solution. Using ac heat, or crude regulation like LM317/LT108x will rob you of any chance of hearing what these DHTs can do. Enough builders have reported on the upgrade effect on my kits to give you confidence, and they are still available for all these DHTs. The schematic shows the connexions needed.
The other component I have labelled is the input coupling cap. You can try all kind of expensive types, but I am still waiting to hear anything much better than the LCR components PC/HV/S, from Farnell etc. These are industrial FKPs with huge pulse and slew handling, 1500V durability, and sound great.
Attachments
I think you need to start at 150H for a 26 and work up. I'm using a LL1660/5A and personally I can live pretty happily with this in 1:1. Thomas would use it in stepdown which may well be better if you can lose the gain - he's tried both ways and has good ears! But I tried a Hammond 126C in 1:1 with the 26 and that's 106H and it wasn't happy at all. What sounded good there was the 10y and the 31.
Plenty of plate chokes available at 200H - starting with Valab on ebay, plus LL1667 etc. So that's one other way to do it. You have choices. For the plate I'd use something passive and magnetic over a solid state solution - like Thomas. But having said that I'm very glad to have Rod's filament boards in my system - after a choke input!
Andy
Plenty of plate chokes available at 200H - starting with Valab on ebay, plus LL1667 etc. So that's one other way to do it. You have choices. For the plate I'd use something passive and magnetic over a solid state solution - like Thomas. But having said that I'm very glad to have Rod's filament boards in my system - after a choke input!
Andy
Hi Albertli!
Some excellent advice there from Rod and Andy! As you can see there are different tastes and approaches. None of them wrong or less suitable, just different ways of doing things. I have not tried Rod's regs yet but have a pair and will give them a go. Although I will most likely stick to pure passive filtering as this fits better to my style, I'm sure Rod's regs work nicely. The kit makes a very good impression.
Thomas
Some excellent advice there from Rod and Andy! As you can see there are different tastes and approaches. None of them wrong or less suitable, just different ways of doing things. I have not tried Rod's regs yet but have a pair and will give them a go. Although I will most likely stick to pure passive filtering as this fits better to my style, I'm sure Rod's regs work nicely. The kit makes a very good impression.
Thomas
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