Page 11 of 12
#151
Posted: Sat Apr 16, 2011 3:50 pm
by al newall
Richard wrote:
I tried different IV resistors, 53R and 100R but found the 82R best.
I seem to remember not being able to go much higher than 82R, without getting all sorts of strange noises.
I think i settled for 68R in the end.
#152
Posted: Mon Apr 18, 2011 10:20 am
by Richard
Nick wrote:Cool, going round in circles can be fun and informative sometimes
Yes, certainly a good way to learn
#153
Posted: Mon Apr 18, 2011 11:34 am
by Richard
Aardvark wrote:And how does it stack up against your reference player on rehearing?
Same as before except that I now accept the differences more readily. Before I was suspicious, like when someone gives you something for nothing.
#154
Posted: Mon Apr 18, 2011 12:43 pm
by Richard
Mike H wrote:I note on page 6 it says:
"If we change the load we must change Rk too, [bias] or linearity will probably suffer (too many authors try to ignore the load when analyzing the circuit, which leads to quite misleading results).
"It is therefore a mistake to use an SRPP as the output stage or line-driver of a preamp, for example, because we can't be sure what it will be plugged into and hence what Rload might be." . . . "The SRPP can only be designed properly if we know what the load impedance actually is, and treat the whole thing as a unified system (remember, an SRPP with no load is not an SRPP at all!)."
Further down this caught my eye also:
"What may not be immediately obvious is that absolute maximum power from the SRPP obtains when the load impedance is equal to ra so, in theory, it should be possible not only to optimise the circuit resistances but also to choose the optimum triode for the job! All we have to do is find one whose ra is equal to the impedance of the thing we wish to drive,"
Further to the above, that's an aspect I hadn't considered (what is Rload) and I should have 'cause I'm sure I saw that PDF before. Need to experiment....
Yes 6n2p has 50k ra and I use 50k input so that was what got me "optimising" the srpp for the 6n2p into my 50k preamp load.
It works fine as the little table of results bottom page 8 shows, bottom right blue figs, distortion suddenly notches out at the correct 50k load.
#155
Posted: Mon Apr 18, 2011 12:51 pm
by Richard
al newall wrote:Richard wrote:
I tried different IV resistors, 53R and 100R but found the 82R best.
I seem to remember not being able to go much higher than 82R, without getting all sorts of strange noises.
I think i settled for 68R in the end.
Hi Al, Interesting as I didn't listen to other than 82R, just checked them on the plank against the meter and they measured worse, so stuck with 82R as it had worked fine in the listening I had done.
#156
Posted: Thu Jun 23, 2011 12:11 pm
by pre65
The coupling cap on Richards lampy circuit is 2.2uf and need to be 100v +.
Looking around are these a "good" cap to use ?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 1492wt_727
Alternatives could be Russian K75-10, or Clarity cap SA, or WD equivilent.
Any other (reasonably priced) suggestions ?
#157
Posted: Thu Jun 23, 2011 12:36 pm
by Nick
Who can say. almost the same price as a SA. Or
http://uk.rs-online.com/web/search/sear ... &R=2108768
at 58p
#158 Mundorf
Posted: Thu Jun 23, 2011 2:15 pm
by IslandPink
#159
Posted: Thu Jun 23, 2011 2:51 pm
by Mike H
Phil the one you posted looks suspiciously like a run-of-the-mill power supply filter type that may or may not have been "tarted up" with new lettering. A cynical viewpoint I know
I got some 1uF ClarityCaps going spare, 2 of each in parallel?
#160
Posted: Thu Jun 23, 2011 2:56 pm
by Mike H
BTW this is the circuit is it?
I might be able to try summink like this with the Philips player, I know naff all about it but I was considering using an augmented cathode follower type of thing using a EF86 with its screen tied to the CF output.
#161
Posted: Thu Jun 23, 2011 3:00 pm
by pre65
I'm using Richards updated version. He spent a lot of time perfecting his version so I'd rather trust that.
#162
Posted: Thu Jun 23, 2011 3:01 pm
by Mike H
Yep OK.
#163
Posted: Thu Jun 23, 2011 3:16 pm
by Mike H
BTW "MKP" just means
Metallisierter Kunststoff Polypropylen (German: Metallized Plastic Polypropylene)
I.e it's not some sort of quality or other suchlike attribute that means anything special
#164
Posted: Thu Jun 23, 2011 3:23 pm
by pre65
Yes, I knew that, but they have a (supposed) good reputation.
May I take you up on the kind offer for 4 1uf Clarity caps ?
Just be careful how you pronounce the middle word.
#165
Posted: Thu Jun 23, 2011 3:42 pm
by Mike H
Certainly mon-sewer.
Ah just as well I looked, all I can lay my hands on at the mo is 4, 2 used & 2 unused. Thought I had more than that! But think I gave or sold 4 to someone else as well