audio-talk

andrew Ivimey · Posted: Wed Apr 29, 2009 5:47 pm Post subject: The Butterfly

Consider the rather dull picture ...

a 417a into AE interstage to 300B (wha'!?!) with total choke input PSU using 83.

The end of a real crappy WAD300BPSE, the phoenix or rather flutterby emerges.

Not much to say really; it works - very easy and quick build, slowed down because I had to do some drilling arrrrgggggH, no bleeding (yet). Lots of tweaking but few components so ... we'll see.

It sounds ??? very powerful, I'm not used to such power! Wink

kinda 'organic', Nice but 'could do better' perhaps.

Not much more to say but I am consoidering the 2A3SE with MVRS and this is a quick and interesting diversion and what else can you do with a heap of badly designed junk?

Anyway more later, I'm off to Malvern imminently and I have no time to do any mods so this is how it is for the moment.

Ah... a weak link. It was 300BPSE, yeah! well that means the output trafos are only around 1.5k and this is not Kosher with 300bSE. Oh there are things I can do and I suppose I will. If these trafos have a respectable number of Heneries (which I doubt) parafeedling would be easy and pay enormous dividends.

We'll see.

onwards --------phrraoarrrrrr and so on.

andrew Ivimey · Posted: Wed Apr 29, 2009 5:48 pm Post subject:

I know, I know, the masking tape!

Well, if you were constantly turning over an amp to dig into it's vitals and the nice shiny chrome could get scratched, maybe you'd do the same.

Mike H · Posted: Wed Apr 29, 2009 5:54 pm Post subject:

One green, one pink!!

Ahh sweet Very Happy

shane · Old Hand Joined: 16 Sep 2007 Posts: 650

Obviously a nautical man.

Mike H · Posted: Wed Apr 29, 2009 6:02 pm Post subject:

Right way round as well!

andrew Ivimey · Posted: Wed Apr 29, 2009 6:10 pm Post subject:

Sorry to disillusion you though I have spent time 'before the mast'!

It's red for right and blue for left - the audiologist's first law.

Anyway, HH's Headhunters sounds great and Prokofiev's 5Th is muddy and confused in the mids - supposedly a 300B's strong point. (muddy and confused in the mids comes from Anna (SWMBO) so it's true!

cor its loud though! Sabs good.

If it don't do Prokofiev it ain't a good amplifier.

Mike H · Posted: Wed Apr 29, 2009 6:48 pm Post subject:

What's the input valve?

Mike H · Posted: Wed Apr 29, 2009 7:00 pm Post subject: Re: The Butterfly

andrew Ivimey · Posted: Wed Apr 29, 2009 8:10 pm Post subject:

Now really ... I'd never take the piss out of someone sensorily disabled but... come on.

How many valves do you see? huh? I said 417a into AE I.S.T to 300B, using 83 as MVR in PSU.

WAD300BPSE was crap and used two 300Bs - 'nuff said. I was robbed and frankly wish I'd never bought it though I enjoyed the trip to Yorkshire to pick it up!

So.......................................................

output transformer, from whatever the source is going to be approx 1.5k primary so it is not GOOD. Fine, I accept that.

'san interesting sound though with sinteresting detail but it doesn't like complicated music hence............. distortion.

But it is dead loud and loads of detail in an interesting kind of way so perhaps it is worth tweaking (though the dustpeople come tomorrow) but otoh I have pair of ONETICs PP transformers that is begging to be used so could so easily do parafeedlydeedly.

Right now, however, until I get back from Elgar country, there's no point in charging up the soldering iron so for what is left of this evening, its solid Jazz and simple music.

rockon.

kuroguy · User Joined: 17 Mar 2009 Posts: 42

andrew Ivimey · Posted: Thu Apr 30, 2009 6:42 am Post subject:

Seems like audiologists do it the same as US sailors then!

shane · Old Hand Joined: 16 Sep 2007 Posts: 650

andrew Ivimey · Posted: Thu Apr 30, 2009 8:27 am Post subject:

Because a) I frankly don't care and b) When you are looking at a patient who is wearing headphones their red 'phone is actually on my left etc.

But does it matter?!

This morning, before jumping on the bicycle. I played Schubert's trout - beautiful, though there may have been some 'oddness' in the mids, again.
So, I'll have to have a look at that.

Can anything br right, though, with output trafos that are rated at 1.5K? It doesn't give the poor old 300Bs much chance of being 'pure'.

pre65 · Posted: Thu Apr 30, 2009 8:43 am Post subject:

I'm using my 5K OPT with 300b SET at the moment,is that OK ?

TBH I thought 5K was the "norm" for 300b. Embarassed

Red for right applies to hi-fi connectors as well.

andrew Ivimey · Posted: Thu Apr 30, 2009 8:54 am Post subject:

We...............lllllllllllllllllllllllllllllllllllllllllllll

the old rule of thumb was 2 1/2 X the plate resistance of the output valve.

A 300B has 800ohms, I believe, so 2K is close. 2 1/2kOhm seems the preferred value.

Now, as a general rule, Philip old chumbly, the higher the primary resistance the lower will be the level of distortion but the lower will be the output power. So the classic 45 valve likes 5K output trafo but you can push this down (i.m.e) to 3.5k and get a little more welly with no audible degradation.

I.M.O, 1.5k is just too small for comfort (and the same applies to 2A3s)but, as I said, earlier, if there is a healthy amount of Henneries then I may aswell just slap on a cap and output trafo and call it parafeedly output - could be very good indeed!