Pye Black Box MK111 valve swap - UK Vintage Radio Repair and Restoration Discussion Forum

wrenrover · 29th Aug 2017, 11:51 am

can anyone recommend changing the PCL83s for 30PL1's. does it offer any sound improvements and will they still clear the underneath of the deck etc.
thanks

Edward Huggins · 29th Aug 2017, 12:49 pm

The envelope is slightly taller, but unlikely to foul the Garrard autochanger. The amplifier circuit is very fussy and I have never seen the 30PL1 used as a substitiute.

ukcol · 29th Aug 2017, 2:27 pm

The BB/A black box was designed to use PCL83s and there is no reason to expect an improvement in sound quality by substituting a different valve that isn't even claimed to be an equivalent.

As indicated by Edward the BB/A employs an unusual and complex circuit; the design employs 2 negative feedback paths and 1 positive one, so any valve substitution may even have implications for stability.

In fact (and I'm sticking my neck out here) I don't know of any well designed amplifier that would benefit from a change of valve type without any changes to the original circuit design. There may be however benfits from using an improved version of a particular valve type.

paulsherwin · 29th Aug 2017, 2:32 pm

It's certainly extremely unlikely to sound any better.

Edward Huggins · 29th Aug 2017, 3:28 pm

PCL83s are cheap enough, regarded as a "TV" valve rather than an audio type. They are around £12 pair. Maybe a tad more for a matched pair. Why mess about with an non-recommended option?

29th Aug 2017, 11:51 am	#1
wrenrover Retired Dormant Member Join Date: Dec 2015 Location: Etchingham, East Sussex, UK. Posts: 6	Pye Black Box MK111 valve swap can anyone recommend changing the PCL83s for 30PL1's. does it offer any sound improvements and will they still clear the underneath of the deck etc. thanks

29th Aug 2017, 12:49 pm	#2
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,338	Re: Pye Black Box MK111 valve swap The envelope is slightly taller, but unlikely to foul the Garrard autochanger. The amplifier circuit is very fussy and I have never seen the 30PL1 used as a substitiute. __________________ Edward.

29th Aug 2017, 2:27 pm	#3
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Pye Black Box MK111 valve swap The BB/A black box was designed to use PCL83s and there is no reason to expect an improvement in sound quality by substituting a different valve that isn't even claimed to be an equivalent. As indicated by Edward the BB/A employs an unusual and complex circuit; the design employs 2 negative feedback paths and 1 positive one, so any valve substitution may even have implications for stability. In fact (and I'm sticking my neck out here) I don't know of any well designed amplifier that would benefit from a change of valve type without any changes to the original circuit design. There may be however benfits from using an improved version of a particular valve type.

29th Aug 2017, 2:32 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,969	Re: Pye Black Box MK111 valve swap It's certainly extremely unlikely to sound any better.

29th Aug 2017, 3:28 pm	#5
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,338	Re: Pye Black Box MK111 valve swap PCL83s are cheap enough, regarded as a "TV" valve rather than an audio type. They are around £12 pair. Maybe a tad more for a matched pair. Why mess about with an non-recommended option? __________________ Edward.