Rob Flinn

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #20 on: September 19, 2006, 06:38:37 AM »
I was thinking about the class A output stage.  The biggest problem to DIY this is the tertiary feedback winding in the output transformer.  

I had the idea that perhaps it would be possible to use 2 output transformers instead, one for the audio out, & the other to provide the tertiary feedback.

Anyone have any thoughts on this or think of a reason why this wouldn't work ??
regards Rob


gyraf

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #21 on: September 19, 2006, 07:14:47 AM »
Wouldn't work, as the idea in the tert. winding is that it shares magnetic path - and thus distortion etc. with the main windings.

The sensible thing to do would be to talk someone like Edcor into making a decently-priced version of this transformer.

- hint-hint -  :wink:

Jakob E.
..note to self: don't let Harman run your company..

Rob Flinn

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #22 on: September 19, 2006, 08:08:35 AM »
Do we know aht the characteristics of the transformer are ??
regards Rob

gyraf

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #23 on: September 19, 2006, 08:19:54 AM »
Should be possible to find out..

Mr Hacksaw - will you, please?  :razz:

Jakob E.
..note to self: don't let Harman run your company..

tony dB

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #24 on: September 19, 2006, 08:38:06 AM »
hint?  :green:

of course we would need specs, then a lot is possible

gyraf

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #25 on: September 19, 2006, 10:06:05 AM »
Quote from: "tony dB"
hint?  :green:


Exactly..  :wink:
..note to self: don't let Harman run your company..

tony dB

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #26 on: September 19, 2006, 10:40:12 AM »
are there mu cans involved?
We don't do those for the moment...

gyraf

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #27 on: September 19, 2006, 11:09:25 AM »
No cans. But there may or may not be gapped-core or ni-lams involved..
..note to self: don't let Harman run your company..

tony dB

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #28 on: September 19, 2006, 11:52:47 AM »
less of a problem then cans (little reserve, in case expectations not met)

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #29 on: September 19, 2006, 01:34:00 PM »
edcor custom tert wound o/p tx's.  a noble idea if ever was one.  

the true noble deed will come from our saviour, who shall give forth his everlasting o/p tx to be crucified on the hacksaw to redeem all our fet squishing sins.

or maybe we're lucky and cj already knows the specs ;]

luckier still will be if it doesnt require any tricks that edcor doesnt do.

fingers crossed

billy


tony dB

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #30 on: September 19, 2006, 01:49:48 PM »
enter Hacksaw

edanderson

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #31 on: September 19, 2006, 02:09:05 PM »
i've had edcor do a number of custom designs, and i would guess that given some time, they could do a workable version of the class A 1176 OPT.  but here comes a delicate thing...  purple has spent some time/effort/money to figure out how to correctly wind these OPTs.  we sell them for $55ea now, and don't make much money on them that way.  i understand that as DIY-ers we're all "thrifty" and edcor could possibly make them a bit cheaper than our current supplier.  but then again, the guy making them for us is probably as close as you can get to the original winder.

so, send purple an email if you want to buy one from us.  if someone wants to organize a group buy from cinemag, the part number is PA96731.  at one point i also specified a version with both secondaries brought out seperately, the part number is CM96731-A.  i'm not sure you'll get a better price going direct, but you are welcome to try.

ed

edanderson

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #32 on: September 19, 2006, 02:15:52 PM »
also, the MC76 kit page is going to be updated to include the ratio and meter switchbanks and caps, which are now included in the $300 price.  for a long time it was difficult to get them, so they weren't included, but now we have a reliable supplier.  meters are also available.

is there anything else (other than lowering the price) that we could do to make the kit better?

i personally would like it if DIYers would support a company that offers a kit version of one of their current products.

ed

SSLtech

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #33 on: September 19, 2006, 04:13:28 PM »
Yay!!!

Hey look... I'm famous, on the purple MC76 kit page!!!

Keef
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

clintrubber

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #34 on: September 19, 2006, 04:56:25 PM »
Quote from: "Rob Flinn"
I was thinking about the class A output stage.  The biggest problem to DIY this is the tertiary feedback winding in the output transformer.

Are such TXs that rare ?

FWIW, I pulled a board with audio TXs from an old Ampex video-tapemachine and found that
the output-TXs had a third winding for driving a meter
(no idea why that required an additional winding, but OK):





But what's the story for output-circuits like that ? (class A & feedback with a tertiary winding)
How do they do 'their signature' ?! One would say they're actually more transparant, right ?

At least I assume that all that third winding trouble is to get higher fidelity
- so one would say that such a stage is then less contributing w.r.t. 'sound'.
Please tell  :roll:

Thanks / regards,

  Peter

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #35 on: September 19, 2006, 05:04:47 PM »
ed, that just made that kit mucho better, in my opinion....  what are your prices on meters if you dont mind me asking 'in forum'?

thanks so much for the kit offer, its an excellent one.... i'd like to get into some soon as i can.  

quick q about the input attenuator... is it stepped or variable?

just curious about it.

thanks again

billy

khstudio

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #36 on: September 19, 2006, 05:57:40 PM »
Quote from: "edanderson"
i've had edcor do a number of custom designs, and i would guess that given some time, they could do a workable version of the class A 1176 OPT.  but here comes a delicate thing...  purple has spent some time/effort/money to figure out how to correctly wind these OPTs.  we sell them for $55ea now, and don't make much money on them that way.  i understand that as DIY-ers we're all "thrifty" and edcor could possibly make them a bit cheaper than our current supplier.  but then again, the guy making them for us is probably as close as you can get to the original winder.

so, send purple an email if you want to buy one from us.  if someone wants to organize a group buy from cinemag, the part number is PA96731.  at one point i also specified a version with both secondaries brought out seperately, the part number is CM96731-A.  i'm not sure you'll get a better price going direct, but you are welcome to try.

ed


I have 2 of the G1176 (Mnats - new version) boards fully stuffed & ready to go... OEP's on the outputs, one w/IC in & one w/Lunduhl input.

I didn't realize your kits were priced so reasonable. Is it posible to MOD the output stage of my current G1176 board to the "Blackface - Purple - Class A circuit" & use your output trannys or is it too much of a PITA :?:

Also, I'm really confussed about the input "T  PAD's" & if they're needed in the "Silver face/G1176 clone" & for WHAT???

- is this something I should add to my G1176 & do you sell those too :?:

Thanks ED,
Kevin
Kevin ~ KHStudio

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #37 on: September 19, 2006, 06:21:29 PM »
I am still interested in a purple kit somewhere down the road. Especially to complement the G1176. Just need to recover from a soundcard/converter buying spree  :green:
This kit really looks amazing.  :thumb:   :guinness:

Flo

eskimo

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #38 on: September 19, 2006, 07:07:31 PM »
I've been really interested in the mc76, including the switches didn't make me any less. In fact, the trouble with that was kinda intimidating before.

edanderson

G 1176 vs PURPLE AUDIO MC76 vs UREI 1176
« Reply #39 on: September 19, 2006, 08:12:26 PM »
meter - $100
attenuator - $70

the attenuator is continuous (not stepped).  all of the urei revs with input transformers (A-F) used an attenuator before the input transformer.  the rev G and later versions used an opamp before a 10k pot, which is what the gyraf version does.  when you install the input transformer on a g1176, it goes before the pot.  if you were to put the pot first, the input impedance would not stay constant as you turn the pot, which is why you need a special attenuator if you want it before the transformer.

the output transformer is gapped, has a teritary winding AND a dc balance winding.  more common features in tube amp OPTs than solid state, from what i've seen.

i don't recommend trying to mod the gyraf or mnats boards to class A.  better to do it on a small piece of perf board.  or lay out a new board.  or buy the purple kit.

if it wasn't clear before, i work for purple audio, but andrew roberts runs the company and all purchase inquirys should be directed to him via email.

ed


 

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