What a great post.
I've built a 10y preamp with Ales Hybrid Mu Follower boards and have to say that I was not expecting it to be so "good". It compares very, very well with a high end SS preamp that I have here (AU$20k) and actually gives a very accurate and dynamic sound with increased clarity/detail and a more intimate connection to the music in my system. I can verify that the gyrator/10y can drive troublesome amplifier loads as my power amps have an input impedance of about 5k including six channels of passive line level crossovers at the input. This is only the second preamp I have tried that has been suitable for that kind of reactive load and it is wonderful.
Hi guys and gals, I contacted Ale about the gyrator boards.
I am new to tubes though not new to DIY or amp building. Hoping to get some help and guidance from all of you on building Ale's preamp.
From what I've read on Ale's website, he is providing some of the major elements but I am on my own to source other parts, put it together, and put it in a chassis, if I so choose. I presume the rest of the wiring is point-to-point.
My system does not need more gain. My DAC/source provides plenty. However, I'm planning to combine this preamp with the FirstWatt F4 amp, which is a source follower or power buffer (current gain only), so, I'm assuming I'll need some gain, maybe 5-10 db.
Given the above info, here are my questions:
1. Would the 01A triode work for the above situation?
2. Could you recommend reliable sources for the tubes? I'm in the US.
3. Does someone have a parts list they could share? I presume I need a power transformer for filament supply and B+. Any recommendations for that? Is there a schematic for the B+ supply? I can manage resistors and capacitors because I have a stock of them.
4. What are folks doing about the chassis? I want something to enclose the build. I am also considering putting it in a diyAudio chassis for the F4 and building the two together. Though that would limit the flexibility in using the preamp in the future for other projects. I guess I could stick a pair of output RCAs on the back.
5. Anything else I'm not thinking of?
Any other words of wisdom would be welcome! I want to make this a success and not put it on the shelf.
I am new to tubes though not new to DIY or amp building. Hoping to get some help and guidance from all of you on building Ale's preamp.
From what I've read on Ale's website, he is providing some of the major elements but I am on my own to source other parts, put it together, and put it in a chassis, if I so choose. I presume the rest of the wiring is point-to-point.
My system does not need more gain. My DAC/source provides plenty. However, I'm planning to combine this preamp with the FirstWatt F4 amp, which is a source follower or power buffer (current gain only), so, I'm assuming I'll need some gain, maybe 5-10 db.
Given the above info, here are my questions:
1. Would the 01A triode work for the above situation?
2. Could you recommend reliable sources for the tubes? I'm in the US.
3. Does someone have a parts list they could share? I presume I need a power transformer for filament supply and B+. Any recommendations for that? Is there a schematic for the B+ supply? I can manage resistors and capacitors because I have a stock of them.
4. What are folks doing about the chassis? I want something to enclose the build. I am also considering putting it in a diyAudio chassis for the F4 and building the two together. Though that would limit the flexibility in using the preamp in the future for other projects. I guess I could stick a pair of output RCAs on the back.
5. Anything else I'm not thinking of?
Any other words of wisdom would be welcome! I want to make this a success and not put it on the shelf.
At first had no bass, due to lack of break-in Russian FT3 teflon capacitors, also used PCB separators of metal possibly causing a ground loop, once solved using plastic PCB separators & screws and the capacitors with the break-in got a very good sound quality, better than RC coupled or LC coupled, only have advantages, it's so good that inmediately found easily the difference using in the CLC PSU different quality chokes, the bad Stancor 10.5H 110mA 225 ohms and the good Bartolucci 10H 100mA 10 ohms. A big thanks to make it available for the DIY community. Gracias Ale.
For constructors in the U.S. Antek, inc offer screened toroidal transformers - these are now first choice recommended for my filament regulators.
Be sure to select units from the AS- series, to get a screened version. This means that 50VA is the minimum rating - but that is no problem.
Example for 01A Filament Bias:
AS-0512 - 50VA 12V Transformer - AnTek Products Corp
This gives around 16V DC for filament bias. Other options are possible, if a little more voltage is needed.
Connect the PURPLE wire to the negative of the Anode/Plate supply, at the PS end.
BTW, Ordinary toroidal transformers are not recommended - the external field may be low, but without a screen, they couple too much noise through from the mains. I have measured nF levels of leakage capacitance - much worse than ordinary EI PTs, (Hammond 166 - 266 series for example) -which get the leakage down to 50-70pF. The EIs should be chosen, if screened PTs are not available.
Hello,
As ALWAYS good advice from Rod without sending you a bill.
The French audiophiles in the eighties already had their doubts about toroidal transformers for the same reason Rod mentions. Back then polution on the power net was much lower. Now every house has loads of devices with badly designed supplies because these devices dont need a high tech supply.
For my Rod Coleman supplies i am using the split bobbin Triad transformers which he recommended before. I have one that was a bit noisy mechanically but can be solved by using some grommets.
BUT if you have a transformer that passes garbage from the power net it will be hard to solve. And depending on the gear , the transformer could also pass garbage back into the power net.
But i guess most folks will continue using toroidal ones without any screens because everyone else does.
Greetings, Eduard
As ALWAYS good advice from Rod without sending you a bill.
The French audiophiles in the eighties already had their doubts about toroidal transformers for the same reason Rod mentions. Back then polution on the power net was much lower. Now every house has loads of devices with badly designed supplies because these devices dont need a high tech supply.
For my Rod Coleman supplies i am using the split bobbin Triad transformers which he recommended before. I have one that was a bit noisy mechanically but can be solved by using some grommets.
BUT if you have a transformer that passes garbage from the power net it will be hard to solve. And depending on the gear , the transformer could also pass garbage back into the power net.
But i guess most folks will continue using toroidal ones without any screens because everyone else does.
Greetings, Eduard
Hi Rod, just curious about your thoughts regarding split-bobbin EI versus screened toroidal transformers for your regulators. I've always used the former, with excellent results.
Hi Bob,
EI are perfectly good, especially if you have it installed and delivering on low hum.
A screened toroidal is likely to be in the same region - as good or better - for leakage capacitance.
I don't have an Antek AS series to measure - but if anyone has a 9 - 15V one to measure capacitance across PRI→SEC that would be useful data for constructors.
The Antek will be better for stray magnetic field though, and probably better for mechanical hum (so long as the level of DC on the wall voltage is low). These features should be welcome in a preamp build.
EI are perfectly good, especially if you have it installed and delivering on low hum.
A screened toroidal is likely to be in the same region - as good or better - for leakage capacitance.
I don't have an Antek AS series to measure - but if anyone has a 9 - 15V one to measure capacitance across PRI→SEC that would be useful data for constructors.
The Antek will be better for stray magnetic field though, and probably better for mechanical hum (so long as the level of DC on the wall voltage is low). These features should be welcome in a preamp build.
Thanks Rod! Appreciate the input. 16V seems plenty for 01A, 71a, and 26, based on the recommendations on your website. I'll be springing for those regulators soon. Any recommendations for B+?
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