Brumjam

01A Preamp Builders Unite!

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Super Wammer

There are at least two of us on this forum embarking on a project to build a preamp using 01A valves.  We will use this thread to track the progress of both builds.

All I've done so far is order the parts needed for my HT supply, plus the transformers for my LT supply.  I'm essentially going to follow Ale's Gen2 circuit which can be found here:

http://www.bartola.co.uk/valves/2017/01/15/01a-preamp-gen2-build-complete/

To keep this build simple to start with, I'm going to build it on two separate pieces of wood.  This will allow for lots of tinkering before I put it in two separate metal cases.

It would be great to hear from anyone else who has built a preamp using 01A valves - tips, tricks, do's, dont's greatly appreciated.

Edited by Brumjam

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I'm the second one, but it will be slow going for me.  I have recently finished (?) my type 26 DHT pre  http://hifiwigwam.com/forum/topic/115323-type-26-dht-pre-amp/ and decided to try an 01A pre, using the same PSU.  So far i have ordered the gyrator boards from Ale Moglia, and will gradually build up the other components.  The chassis is something I can start on first, the same size as my 26.

So watch this space, and if anyone else has anything to add, then the more the merrier.

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What's the difference between this one and the ones that you have just finished?

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27 minutes ago, ijrussell said:

What's the difference between this one and the ones that you have just finished?

For me it will be using a gyrator instead of a transformer output.  And when I started the type 26 several people who had made them in the past had already moved on to the 01A, reckoning it is even better.  But the 26 was my first DHT pre, built without fixed plans or from a kit.  With much help from someone who actually knows what he is doing! :D  However I have learnt loads and thought I might as well try another build.  

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I also will be using Ale's Gen 2 circuit, at least as a starting point, but will need a couple of questions answering, probably by Ale.

Will it matter if the volume pot is 100k or 47k?  100k might be easier for me as I have pots to start me off.

And can the gain be reduced without compromising the sound?  I don't really need ANY gain, and I got rid of a Consonance valve pre as it had too much gain.  The output transformer on my type 26 can be wired in various configurations which changes the gain, but I have no idea how the gyrator works!

It may already be apparent that I am better at construction than calculation!

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Super Wammer
19 hours ago, ijrussell said:

What's the difference between this one and the ones that you have just finished?

My current pre is based on two pcb's Ian.  All the parts have to be as per the BoM.  With this new build, there is a lot more flexibility around which components to use - there's no PCB's in the power supplies.  The 01A tube is meant to be slightly on the warm side of neutral-sounding compared to the type 26 and 4P1L.  

Here is the HT power supply I will be using.  This is shown on Ale's website (link shown earlier up this thread).  I will be using AZ1 valves which turned up in the post today, along with the chokes, caps and resistor.  I don't expect the AZ1 valve bases and mains transformer to arrive for another week.  Another set of Coleman regs are in the post.

01a-Universal-HT-Supply-V01.png

Edited by Brumjam

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This is my current HT supply for the 26; I am hoping that by changing R1 and I1 I can get the voltage I need for the 01A.

TYPE%2026%20HT_zpsblffqlfw.jpg

Edited by awkwardbydesign
I meant change I1 not L1

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Gyrator PCBs arrived just now.  That was quick!  I thought he had sent bare PCBs (I paid for the SMD soldered version), but the SMDs are so small I missed then initially. :doh:

D3 near the top.  I left them in the anti-static bags for the photo, as I can't use them yet.  But at least I can work out where to fit them now.

20170128_131917_zpstlmmafdy.jpg

So I suppose I will have to build it, now!  But I have one of those stupid colds (?) that hang around for ages, and it's gone to my chest so I daren't cut any wood.  Damn!

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Good though the TKD pots are, the Canadian PEC carbon pots have been recommended to me.  Unfortunately they only seem to be available from the likes of Digikey, which makes then almost as expensive as the TKDs.  Unless someone can add them to a larger order, or a group buy.  They are about $34 plus whatever gets added. 

http://www.digikey.com/product-detail/en/precision-electronics-corporation/KKA1041S28/KKA1041S28-ND/770961

EDIT. Actually, after checking the UK site, they appear to be £26.55, with free shipping on orders over £33.  So if two of us buy them it would come out at about £33 each if you allow 25% for VAT and import duties.  I might want a 100k, but they are available as 50k too.

2nd EDIT!  Actually it looks like £26.55 might include taxes!

Edited by awkwardbydesign

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Super Wammer

Hi guys. I've built loads of DHT preamps with 26, 01A, 4P1L, 10Y and more besides. I stated off in 2009 with transformers and plate chokes but I'm now using Ale's gyrator - it's cleaner and more detailed. I'm also finding the 01A the best preamp tube. Ale's a friend I collaborate with, and hats off to his gyrator. I'll give you my power supply and I'll try and post pictures of my latest build for a fellow enthusiast. The circuit for the 01A Gen 2 is on Bartola Valves, and the PSU goes with that. the choke input filament supply feeds a pair of Rod's regs. Andy

PSU 01A Gen 2.png

Here's the 01A pre feeding my 4P1L PSE output stage. 

Denis 01A+amp.jpg

Edited by pmcuk
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Super Wammer

"The 01A tube is meant to be slightly on the warm side of neutral-sounding compared to the type 26 and 4P1L.  Here is the HT power supply I will be using.  This is shown on Ale's website (link shown earlier up this thread).  I will be using AZ1 valves which turned up in the post today, along with the chokes, caps and resistor.  I don't expect the AZ1 valve bases and mains transformer to arrive for another week.  Another set of Coleman regs are in the post."

The 01A is more neutral than the 26, which is warmer and more euphonic, verging on the lush on vocals. The 01A has a thoriated filament which gives a clean and dynamic sound, just like the expensive 10Y but cheaper. The 4P1L is clean and clear with a more bright top end. Not quite a subtle as the 01A, but better for driving more difficult loads since it operates at 25mA and upwards. Ale's gyrator works for the 4P1L at up to 25mA but no more since the BF862 won't take it. 

AZ1 mesh plates are the creme de la creme. I have a collection and have been using them for many years. The plain plates are probably no better than some others, but cheaper. Worth having the mesh. Expect to pay £30 at least but hopefully not much more. I also use AZ11 mesh, different base but same tube. I prefer that base since the AZ1 base is very grippy and you can easily loosen the bottom of the AZ1. Always prise it up from the bottom, never pull from the top. The easiest mains transformer to get is by big.daddy! on eBay (he's in Hillingdon, London), 50VA Mains transformer for Valve tube pre amps 250-0-250V + 6.3V 2A + 6.3V 1A:

http://www.ebay.co.uk/itm/172130550448?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The 6BY5G is a nice rectifier at 6.3v, Ale and I both use and like it but I bought my stocks from the USA. The EZ80 or EZ81 is common here. You can use 5v rectifiers with a couple of step-down resistors but I wouldn't unless the supply were rated more than 2A, which you might get with a Hammond transformer from Bluebell Audio, where I get the chokes from. Philip's a musician and a good guy. AZ1 would need step-down resistors as well, or a 4v supply which isn't obvious. 

Coleman regs are great! You don't need a heatsink if your top plate is fairly massive. I use 4mm soft aluminium. The 4mm medium hard is a bit tough on tools like drills and hole saws which you need. Richard uses the hard grade of aluminium, and frankly he's welcome to it! The softer grade shows up imperfections more but hey, this is DIY. 

Have you looked at Lincoln Binns for chassis? Their Uniobox 2 is really useful in 220mm length. Fits this project perfectly if you use 2 boxes.  

https://www.lincolnbinns.com/en/custom-extruded-aluminium-enclosures/

 

 

 

 

 

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26 minutes ago, pmcuk said:

Richard uses the hard grade of aluminium, and frankly he's welcome to it! The softer grade shows up imperfections more but hey, this is DIY. 

 

It's what real men use! :D   I find it easier to work than the soft grades, as drill bits don't bind and clog.  And it takes a polish rather well.

20160629_162307_zpsyqovfkab.jpg

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Super Wammer

Thanks for all that information Andy.  I'll have a read through later tonight.  James.

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Super Wammer

Here is the enclosure I'm looking at:

http://www.ebay.co.uk/itm/Aluminum-Enclosure-Amplifier-Chassis-PSU-Cabinet-DIY-Case-Box-W220-H100-D311mm-/251742467443?hash=item3a9d053573

I can see this working well with a wooden front and a carbon top plate B|.

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I used a small case from them for a PSU for my Duet.  It is quite good quality, if a little sharp edged, and lacking that silky feel of more expensive casework. Luckily I can make my own bigger chassis and save money.  Not time, but I have enough of that!

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