To All The Transformers I've Loved :)

The 'other' signal unit that I'm working on for this 'Modular PSU' is a  stereo 'character box'  ...

It's  some stew mac  of many  transformers,  tubes,    JLH modules for line amps  and also the little JLH  'Liniac' modules  ..  for general purpose purposes   

Basically,  two  'feature'  instrument channels    ie  some    level control, eq and output amp duties with a good bunch of extras  .... 

- 'parallel' balanced outputs with some chip(s)
- some balanced  'send-return' buffering  with some chip(s)
-  a little bit of 'light weight mixing with aux-in' connections onto the little passive bus [es]

I think that should do me   for my build 'two towns over'    [after this first signal unit goes live!]

....

Here's a pic of what's going on so far  ... with my first 'signal unit' - 4 chan to stereo  'recording mixer' 

....    while I'm filing the front panel  'vu meter'  holes     

Lol, half of all my  'diy time' over these past  years  ..  is  'filing meter holes'       
 
[just can't help it - classic audio without proper meters is like  hot dog, no sauce ]

If I were 'doing  all over' ,  I would have gone 'modular' external PSU for all my tube stuff 

... and the  locating of  PSU racks in an adjoining closet  ! 

Makes better economic sense, better radiated EM performance [meaning lower humm]  and cleaner 'aesthetic lines'  on the 'signal units'.

I also suspect  'centralised modular psu' might be less 'overall' power (VA) consumption too ..  rather than having each unit with it's own large PSU traffo, chokes etc - but I would have to work up some 'scenarios' to get a better idea on that front ..

But, for sure,  it's a very  'bespoke'  concept ..    as I now know, I only ever needed 8 [eight]  great tracks  .. the rest was so many 'millstones of opportunity' which just diluted my    'musical performance'    time .. 

NO probs, I was an *e_eng*  first  and  fore-most anyways,  and thus made my living from the more mundane tech world.

All 'this diy of ours' has always been so much 'icing on the buds' 

...

I especially like the 'dust and rust' all over now  ...  quite 'apt'  symbology  as regards myself  8)

So - for this '4 chan preamp mixing to 2 chans'  with a few 'twists', the *present* lineup of signal transformers are :

Altec Model 15335A  15K/15K (non centre tapped, 20-20Khz measured)  as load for the 'one bottle'  AV7 preamps  (2 stages mit nfb)

-> this is a heavy shielded can octal type of 120g in weight.  I'm using all four of my favs in this 'jackie blue' build and they were quite affordably priced.

I do plan to run a couple of loads off of this  'plate and  iso / matching  transformer' combo, including some 'attenuation network' ..    to 'knock down' the signal amplitude a bit ...  in light of the 1:1 ratio and the expected  'lightly loaded' secondary max of  50Vpp or so

...  very much  TBD still _

UTC  H-25 [TF4RX17YY] 500/500 (centre tapped secondary with up to 20mA dc on primary,  1W and 40-20KHz +/- 2dB stated)

-> this is a hefty cylindrical shield moderate thickness and is 240g in weight and well bigger than the Altec, though not as 'precision' in performance.  I'm using four of these as 'JLH Class A line amp transformers  ...  and they were super cheap

UTC LP-519 (part Nbr 202348) 10K/5K interstage traffo (non centre tapped,  0.13W and 50-20Khz stated)

-> this also is a cylindrical shield moderate thickness, bit bigger again  and 260g in weight. I'm using two of these as load for the stereo mix make up stage  6SN7 tubes. They were also dirt cheap.

A pair of Trimax [aust] 600/300 line output traffos with heavy cast shield ..  as load to the JLH line amp class A discrete modules on the main stereo mix line amps  ..  too.

.....

That's quite a lot of transformers, right ?

-> input channels    :  4x Lundahl mic pre, 4x Altec interstage, 4x UTC class A   
-> output channels  :  2x UTC interstage, 2x big a** Trimax  low impedance line outs
-> psu                              :  2x Edcor  250Vac at 100mA, 24Vac at 1A, 6.3Vac at 2.5A

That all 'winds up'  [like the magnetics pun!]  to be :    16x signal irons + 2x psu irons  -> 18 irons  -  a personal record for me 

[if I can  indeed pull it off, that is ]

1ru PS        Unit [  two more ru  for clearance on top]  and
2ru Signal Unit  (three more ru for clearance on top] 

I would say something like  100VA  or less  power usage  [tbd]  and  about 17kg for both units combined    [tbd]

  ..  and of course, that  8ru total space needed preferably with 2m seperation in betwixt.

Sturdy metal rack recommended - wooden panel accoutrements optional 

...

Should come together quite quickly as I have most of the subsytems tested already and just I've finished the front and rear panels.

Mostly this is a 'stitch up' job and a bit of 'rigging' as concerns getting all 6x JLH modules with sufficient heatsinking  [as well the  +15V class A regulator module]  in the signal unit  !

Even so, I'll get things fully tested before I start drilling and milling the 'top panel', which is steel.

Take nothing for granted ! Check everything before committing to steel.

..

PS - for the inevitable and justifiable 'why bother' ? type questions, the answer is 'because fine magnetics'  and because that's what I have  'at hand'  8)

When this is inevitably 'parted out', the 'throwaway' part is not so much ..  120aud for the racks and maybe 80aud for the disposables  or 'deplorables'   

lol once again I seem to gravitate to the '100usd piece of kit'  descriptors

The rest can easily return to the eb&y 'ether' from when it came  and I'm confident they will return at least what I paid for the 'vintage bits'  as well as the 'throwaway' bits    [balanced portfolio of stuff concepts ]   

I would estimate about 600aud or so for  the choice bits    ... making around  500usd more or less  for the lot  ...

[mostly bought over previous 5 years or so and when the aud was worth more]

..

Here's a pic of some of the signal irons ..  sorry about the fuzzy  ..  my cam, my eyes, the light etc don't always play together well.

And the Trimax  low impedance  line output irons  ..    basically free plus postage and handling and taxes - all up same as a regular bottle of Johnny Walkers Red  from the local 'outlet'

These guys can drive some serious  'lines'  and last considerably longer than the scotch of same value 

I'm well on my way to being the local Trimax Transformers [Aust]  expert  ..  at this last civilised place 'north of the border'  [down antarctica way ]

They  probably featured in the Aust. Broadcasting Commission (ABC) studios circa early 60s ..  I like to think they came from my state of Tas  capital city Hobart, from the studios of that 60s/70s 'music video' program  on local  black and white TV  ... 

called    'Happening Hobart'  [as I remember early 70s or so when I was a kid]

Mmmm, Trimax

They're    'double malted'      [on the cheap] 

...

Here's my panels .. in the raw ..  I have to say, doing the stupendous Triplett meter, from Bluffton Ohio, 'raw' as opposed to the 'bezel' mounting is ^&**&%$ liberating!

I've always done the bezel mount, which is superior to most, no question  ..  machined hardware etc ..  and certainly the Triplett meter with the full regalia  ...  the serious hardware mounted 'buffer board' is glorious in all respects ...

But holy heck - the more basic mounting [circular fitting]  is just like being weightless ...

And the top panel, still in prog ...

I've decided to really 'go the rat' on the panel legending   

I mean a cheap A3 inkjet and some adhesive, clear A3 printable films.

Nothing new really, except in the past it was always A4 prints - meaning a big, ol'  'seam' down the middle of the panels.

No more! Going forward, I'm re doing the do-over again one more time  - this being an A3 inkjet printer around 220aud and A3 film stock 50aud.

I figure my 'signature series' is worth 200usd for my 'next step DIY  labeling'  capability,  spread out over the couple of units I have in mind

If I get it 'right', you won't see any difference  [except in HD] 

...

This is where the top panel is going ...  now I can really get moving ...

And just for fun, here is my 'watching tv' rig  ...  you can see  'tatami pad' {or whatever'}  to do my 'steps' while I play.

It is a lovely Japan woven reed affair with a  hard firm foam ..  makes the 'stepping' really luxurious ..  while you play the guitar.

The Yamaha 03D digital mixer is the finest 'guitar effects and monitoring mixer' I ever used [and purchased new 1997 !]

I very much like the 'gate-comp-limiter'  [compander]  dynamics control on the channels  and the 2x  stereo fx units built in have that super feature 'side chaining'  .. 

My fav personal guitar preset  is to set up a 'stereo delay'  with an in-line 'reverse gate' that is 'side chain'  triggered by my [guitar] instrument channel  ...  so the delay presents only after the guitar has 'died down'.  It makes delay less 'cluttering' 

Once you get the 'preset' sorted it's there every time, along with the automation  ...  I think these go locally for about 400aud nowadays with the digital  ADAT card.    Mine is 23yrs old, used daily - no probs.  Thanks Yamaha [awesome]

and some detail on the fine magnetica  .  or magentica  [sic]

Really looks great!

Thanks Doug!

Here's where things are shaping up some ...  you can see my '4 Chan Rec Mixer' back and insides ...

Finished the first pass of 'fitting' the 2ru case ...  stitched up enough to get going on the main event ...  the top panel.

It's going to be busy!

..  of course, the 'top panel' is  steel ..  not a prob to drill,  but tough to file 'at all',  no question.

Nowadays, for my 'top shelf stuff', I use some chassis from the 'hong kong hifi world' ...  a little  more expensive than these 'utilitarian' racks      [ie. 'cheap']      from my local Australian supplier 'Altronics'   

..    of course, the 'alu  all round'  is much easier to work with.

I like the HK  enclosures with the  'thick alu'  front panel and the decently thick top panel.  For the aesthetics, for sure  ...  but with no 'rack ears' one needs to make racks mit 'shelf's.  That's where I like the 'spacious' wood racks  - particularly made from reclaimed 'old furniture'     

...  plenty, plenty airflow is the key to not having issues with heat,  [especially with regards 'tubes + wood'  I think but it's perfectly fine as long as one has plenty of 'airspace' all around!

And now you can see the front and top coming together ...

And the top detail pic ...

Sadly I don't have space to provide a volume pot for each of the four channels on the top panel - so I'm just using a switch to provide a    'hi - lo'  sensitivity, in lieu.    It's not a biggy - most of the volume action is on the front panel and should suffice for this very simple 4 track rec thing.

The switches are good too because they provide some 'landing points' for wiring of the little stereo bus arrangement.

You can see the JLH modules ...  I have  a bunch of these in different 'dimensions'  ...  they differ mostly on the provision for the output transistors.

These ones, with BD13x  types  are typical and can really drive some lines no probs  ..  with around +15V supply, the heat dissipation is not too bad and I am using the large steel 'top deck'  as a heat sink ... shouldn't be more than a couple of watts for each one.  The 'heatsinking arrangement' also doubles as the 'mounting arrangement'. So there's that too!

I may end up using these pictured JLH modules just on the stereo line amps and go for a 'smaller' dimensioned set for the channels. Will know when I get there!

...

Anyway - next step is get some juice going, re-establish my 'baseline' performance and get on with the business of working thru the 'gain staging' ...

That's the part I like most ...  it's going to be challenging matching the 15K  secondary of the 'One Bottle' transformer to the JLH.

I will probably need to alter the first transistor stage somewhat, to give a higher input impedance  ..  something like the '56K' at the front of a neve-e gain stage.

Possibly a deal breaker, but I know soon enough - once I unleash the power of R E W and my 'DIY-Probulator' 

[I have a pic of schemo for my [passive attenuating]  'DIY-Probulator'    if anyone wants ... ]

The margin-over-hum of the 'One Bottle mit AV7' is quite good ... at 1%, so I have some room to play, but the noise is already so low down there, that after 'dropping' more than about 6dB in level, I'll be fully clobbering that margin. 

[meaning that the hum floor can probably drop by half before disappearing into the interface 'background noise'  which defeats most things dearly]

So we see.    Maybe I shift to my  personal fav AY7. Perhaps, perhaps not.

....

And  that's the challenge ..  whatever, I'll adjust my plans as required  

If necessary, I'll go the more obvious 15K/600 route in lieu of the fine, fine Altec  ..  they could stay on my bench some more,  with no loss of fidelity!

I will say, I've used the Altec 15K/15K as 'interstage' feeding a 'tube line amp' and they completely 'nail' it.  Even with very high amplitude signals they still shine on.

And [in pic of tv rig posted above]  -  that little blue  'Moskie Deluxe Preamp'  boost + overdrive/EQ  for 50aud is quite good  ..  not 'perfect' but nearly so!

What a killer little, cheap, 2 footswitch  'Blue'  pedal it  is  ...  to put in front of your own DIY 6V6 Amp [with WCF line amp] 

I wish I had have known all these things when I was 21 and 'gigging the local pubs' in various bands ..

Mostly then, tech-wise,  I was doing  e-m  'field theory'  in all sorts of crazy 'domains'    ... and luggin about a Peavey Heritage BW!

...

Here's a gratuitous pic of my previous 'tv rig' 

-  'LA2A with Fender Preamp'  build based on the 'Drip v1' pcb with Sowter and a mix of Hammond, MCI traffs
-  '175b'  build with the 'Drip' pcb with Sowter traffos and Edcor PSU traffos
-  Sum Bus' build using the 'back end of 1272'  modules and Carnhill traffos and an eb*y outboard PSU
-  'fixed up'  TNC Chineve 1081-styled mic pre box
-  Quad 'Reamp / fet DI / API styled  DI'    build

And above all that is the 'AV' section  ..  a Pioneer Digital hifi amp and a TC Electronic Finalizer+ 

The Finalizer stitches together the digital world of 'AV media player'  ...  to  my cosmos  of 'DIY studio electronics'  ..  beautifully 

[hearts and flowers for this awesome Danish  'one-box-to-rule-them-all'  unique-r  ]

...

Then there's also the instrument  'du -jour'  .. 

  ...  in this case,  the crazy fine  Schecter C-1 E/A guitar from Korea

- which is kind of a 'cnc carved super strat'  ...    a chambered mahog body [2 F holes!] with the curved top contours,    Seymour Duncan passive pups    plus the LR Baggs  '6 ways from Sunday'    'peizo + actives'  system  ..  and TonePros 'locking'  bridge/tail combo.

In terms of 'electronics' this guitar does great and very usable  things  ...  and can go very 'hot' in signal level indeed.

The chambered body  retains quite a credible 'resonance' [in the hands]  with surprising acoustic volume - that I really love when going 'unplugged'.   

If desired, it sounds very much like a stage amplified acoustic but one that you can really dial in the 'crunch' too.  It has the 'stereo' output jacks which function in a variety of ways.

Truly  *the*  modern 'lounge / TV guitar'    and can be very 'hi-fi' indeed  ..  making it perfect to test some of my boxes, which generally benefit from a proper 'hifi' monitoring setup  ..

AND they go for very low dollars these days  ...

...

Speaking of low dollars [that's me]  ...  you can also see  the 'monitoring' get up  .....  an ancient SPL Vitalizer  and give-away priced Pyle Power Amp mit BJTs  and of course, some even older Tannoy System 8.

For those times when one is on the couch doing 'research'    well    'over the hill'    ;D

I even built the rack from cheap pine boards from the local 'tip shop'  ~

And now is the time to re-'bone up' on the JLH stuff  ..  regarding the input impedance and gain at that first transistor.

I suppose what I really need is a    'med high Z'  input with not much gain and  that can 'take a reasonable amount of signal'  without borking out.

ie. a 'tube' 

But seeing as how this whole 'signal unit' grew out of the need to 'do something'  with a pair of  hitherto    'unused'  Edcor  Blue psu traffos  that I originally bought to do some groupDIY build or another ... that didn't work out    .  .  . 

The Edcor PSU  traffo  has  not enough current on the 9Vac  'heater winding'  to get    'truly silly'    [with tubes],  on the  half-doz  line amps that I need.

It does however have this  24Vac 'utility winding' for around 1A  that I wanted to  'utilise'  ..  it drops 'precipitously' when loaded and can be then 'regulated' to drop some more ...  to get to somewhere like +18Vdc good for 700mA or so    .. enough for 6x modules, I hope.

...  and so a reasonable 'fit' for that  gaggle of 'class A discrete'  tiny modules for line amp duties that have captured my attn.

Together, it means 'some tubes' and 'some discretes'      Which happily,  can be a great combo.

....

Hence the 'JLH' modules  ... John Linsley Hood   which have been the 'object of fascination'  to me since forever.

Certainly before I knew anything detailed about  'tubes'.

And 'serendipity - ously' , there are no shortage of eb%y modules 'super cheap' based on said JLH, that range in power handling from quite low to horrendously huge  [class A audio].

I've had loads of fun playing with them and they turn in figures that to a 'tube person' can seem very credible   

...  so now I'm hoping to 'adapt' the basics to something I can use here, being primarily 'something to capture my interest' more than anything else. 

Certainly of no interest to a 'fast lane' audio person with access to modern tech  ie. one could do very much better than I'm going to find here

..  this is more of a    box to    'soak up excess time, unused and unloved parts  ...  some vintage'    before being parted out in the not too distant future!

....

I'm just  now  setting up the JLH supply  'regulator module'    [with decent heatsink]  ..    that is to live 'at back' of the signal unit  ...  it  can manage a 'useful amount'  of current with a 'low voltage drop LTxxx device' 

... and apparently  with better ripple figures  [than  my usual standard LM31x regulators]

Those little **&**s    forever puke at the first sign of  'trouble ahead'  and can be quite ordinary at best. Never again!

These LTxxxx  are much more  the ticket for anything 'Class A'  [which is very unforgiving of ripple and gloriously inefficient ]  ...    particularly when using  some quantity of  [6 off]  of ..   

....

Once I have that  'in hand',  I will be characterising these typical  JLH  5cmx5cm modules with respect to input impedance, useful input amplitude range, gain and  level  capabilities  ..  at the quiescent currents that I am prepared to 'sink'  and with the regulated Vcc that I can 'live with'  [heat wise].

After that would be some 'taming down' of the beastly capabilities of even these  ..  and then  build up some new ones up that hopefully will work for me.  It may require a change to some 'fet' up front at the module ..  and so on.

Otherwise ... who knows, I can take a year or so to think about it 'some more'.

..

Here's a pic of the insides of the 'Modular PSU #1'    ..    I have also worked on my #2 model, but that is much more serious! being able to weld  up a small steel boat.    For another day ..

This is what I want to try to 'best'  ...  done with the same Modular PSU #1  ..  and my 'Tube Test Rig'  which is a protyping thing.

The last snap I took before downing tools last summer  ...  when the fires were getting close.

So - I want to try to get 'here' with the tube channels ..  and not mess it up too bad from there  ...  to my line outputs  and mix outputs and so on.

..  and this was the 'birds nest'    and an early, tamer version for sure!

..  and a suitably more modest 'top side' view ..

Believe it or not, this 'setup' has given me my best proper performance figures to date 

When I started 'honing in' on the zone, with this thing, I did find that the process of 'normalizing' the various different tubes I tried [the best of the common man's best, I like to think]  ..  the performance measured generally speaking, converged ...

Quite a bit more than I expected, really ...  in the end, the differences between the several candidates for the 'best' wound up to be surprisingly 'small' ..  at least to me.

So - this is the 'bar' r  such as it is ..  It's going to be difficult to better it  ... with super simple tube circuits  ... and the same audio interface [that is]  ..  and same  PSU  too.

If I can 'not stray too far' it will be a huge win.

My last 'optimisation' effort with this sort of thing, R E W and my 'DIY-Probulator'  [the TWalton Special Edition]

..  made such a huge difference to my little 6V6 Amp Head [mit WCF Line Amp],  it paid for itself 10 towns  over.

..  and this is what I mean, probing-wise.

Apologies for the crap photo .. but you should be able to get the gist.

The 'deal' gets a lot more interesting when one goes to an 'active' DIY-Probulator . Seriously.

One adds a decent cathode follower (CF)  ..  I like 'pentode on-top-of-triode'  myself  ..  but it does kind of need a proper 'tube build' just for that.

Happily that's what my 'Tube Test Rig' does for me  ...

That's when the 'loading effects' can be 'simplified away'  providing your 'active probe'  is exceptionally quiet etc.

And this was my horse, this time last year - Aedigus

He went off to a family with some 'dressage' girls and so found a nice place for him to get on with it

He wasn't too impressed with DIY to be sure.  This is what he would look like when I would wax lyrical on the EF83 tube !