fazer

Re: OP-6 from scratch
« Reply #80 on: January 24, 2020, 04:47:34 PM »
Quote
I’m falling more and more in love with it’s delicious tone :)


I’ll start rounding up some parts.   I have some 0uncer 016 input with 50k output mic transformers and the 6j7’s.  Plenty of old cases so will need a choke and output trans .   Also have some Modutec VUs I don’t have any old ones.  These have to be 50 years old but nothing that goes back to the 30’s.


EmRR

Re: OP-6 from scratch
« Reply #81 on: January 24, 2020, 05:12:21 PM »

I’ll start rounding up some parts.   

I have original OP-6 inputs in the BM.

I can make the original gain control for anyone wanting that, including modified Daven's that will retrofit a bad original OP-6. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

DaveP

Re: OP-6 from scratch
« Reply #82 on: January 24, 2020, 05:18:00 PM »
Quote
I was thinking about using a 6SN7 as the triode with the second section as a CF to replace the 6J5.  It could be a Parallel connection also.  rp is the same as a 6j5 .  Thoughts.
That would work OK, just need a bit more heater current.

DaveP
Soundcloud: Delayed Action.

mjrippe

Re: OP-6 from scratch
« Reply #83 on: February 10, 2020, 12:02:34 PM »
I just posted the schematic of the OP-6's grandpa, the 62-A, in the Tech Docs section if anyone is interested.  I will be scanning the entire manual from 1937 soon.

EmRR

Re: OP-6 from scratch
« Reply #84 on: February 10, 2020, 12:17:50 PM »
I just posted the schematic of the OP-6's grandpa, the 62-A, in the Tech Docs section if anyone is interested.  I will be scanning the entire manual from 1937 soon.

Grandpa is true, interesting to note the 62-A was the budget alternative to the OP-5, and like many other things the fancier gave way to the more inexpensive as things progressed into the 1940's.   I have an OP-4 and an OP-5, both are intended for battery power only.  Have seen the OP-2 and OP-3, nearly scored an OP-3 once. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

mjrippe

Re: OP-6 from scratch
« Reply #85 on: February 17, 2020, 03:09:59 PM »

EmRR

Re: OP-6 from scratch
« Reply #86 on: February 17, 2020, 05:32:28 PM »
Complete RCA 62-A manual uploaded here: https://www.dropbox.com/s/hna6milje5hq5xe/62-A%20Manual.pdf?dl=0

Wow, that PSU is same concept as the 96-A.  Very surprised to see such complexity in the lower range remote amp, and no similar supply offered with the OP-4/5. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

DaveP

Re: OP-6 from scratch
« Reply #87 on: February 17, 2020, 05:44:07 PM »
mjrippe,

Thank you for that!

Best
DaveP
Soundcloud: Delayed Action.

mjrippe

Re: OP-6 from scratch
« Reply #88 on: February 18, 2020, 08:10:35 PM »
Wow, that PSU is same concept as the 96-A.  Very surprised to see such complexity in the lower range remote amp, and no similar supply offered with the OP-4/5.

Agreed, Doug.  I was sharing this manual with a friend who designs audio gear and mics and we were marveling at the PSU.  Four tubes and DC regulation is a HUGE expenditure at the time.

Re: OP-6 from scratch
« Reply #89 on: April 27, 2020, 09:15:26 PM »
Greetings,

May I ask what type of cable and  power connection did you use between the power supply and preamp?

best,
Ryland


DaveP

Re: OP-6 from scratch
« Reply #90 on: April 28, 2020, 04:30:39 AM »
It was about 5A cable, but the most important thing was the diameter, it had to fit in a Bulgin Plug  313-993
 and socket  313-970.

These are Farnell part numbers, I believe this is Newark in the US.

They were wired HT/B+,  6.3Vdc and Earth/ ground.

Best
DaveP

Soundcloud: Delayed Action.

fazer

Re: OP-6 from scratch
« Reply #91 on: July 03, 2020, 09:24:35 PM »
Hey Dave I have question on the gain switch.  I’m assuming it’s non-shorting.

DaveP

Re: OP-6 from scratch
« Reply #92 on: July 04, 2020, 03:18:44 AM »
Quote
I have question on the gain switch.  I’m assuming it’s non-shorting.
I use MBB (Make Before Break) switches for this kind of use to lessen switching noise.

I use BBM types when switching B+ on meters.

Hope that answers your question, happy 4th of July and stay safe!

DaveP
Soundcloud: Delayed Action.

fazer

Re: OP-6 from scratch
« Reply #93 on: July 05, 2020, 10:59:07 AM »
Thanks Dave.   We are all safe.   I ordered the shorting type. 

syn

Re: OP-6 from scratch
« Reply #94 on: October 23, 2020, 11:37:31 AM »
Very nice work Dave. Is your attenuator a drop in replacement for the original attenuator? If not, what are the differences apart from 21pos of the original vs 12pos that you made? I'm in the process of building OP-6 clone myself and have the iron ( not original but quite close, 10:1 out etc) and the tubes,  so I want to bring the attenuator part as close as I can.

Thank you


 

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