832 TWEEKS

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pre65
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#1 832 TWEEKS

Post by pre65 »

Hi-i am going to try the 832 in triode mode.

Convention says connect grid to to the anode via a 100R resistor,but on the 832 that is a little bit of a problem.

I know sometimes you can connect the grid to cathode,which will be a LOT easier for me as the grid and cathode are common connections for both halves of the dual valve.

Is it likely to work ?
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#2

Post by pre65 »

Hi-tried it to cathode-bloody horrible !

At any more than slight volume horrible distortion.

Will put it back as it was and try the constant current thingy next.

As i have one grid 2 and two anode connections could i connect to just 1 anode or will that create an imbalance ?
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#3

Post by pre65 »

Hi-i now have grid 2 connected to one anode via a 100R resistor.

Good things these clip leads !

Now i was lead to believe that triode mode would result in less watts but the initial impression is of no change (or even more).

Sound is difficult to assess cos of me but i would say there is nothing "worse" and possibly the bass is less obvious,but more "tuneful".

It is said that the gain of the driver valve is too great for the 832 as it was but would it be more suited to it in triode mode,hence not suffering a lack of volume for a given knob setting ?

This is confusing me !
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#4

Post by pre65 »

Hi-thinking about this,have i really got triode mode ?

I seem to remember on some valves the unused grid is connected to earth ?
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#5

Post by Nick »

Hi-thinking about this,have i really got triode mode ?
I think you have something very very odd. One will be in triode, but the other will have its g2 driven out of phase from its anode.
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#6

Post by pre65 »

Hi-so it looks like you cant run an 832 in triode mode !

Well i tried !!

The amp is now back to standard,but there was a "something" about the "strange" way i had it connected. :)
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#7

Post by ed »

correct me if I'm wrong but isnt g2 common to both valves...in which case you can only run triode connected in PSE configuration..shirley?
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#8

Post by pre65 »

Hi Ed-that sounds more feasible !

Andrew tried them as single ended some time ago but was not at all impressed.
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#9

Post by pre65 »

Hi-i will bring my 832A experiments back to this topic.

Now the CCS mods have been allowed to bed in i must say i am impressed by the changes.More so to the lower regions,but it is not just louder.There seems to be more bass,and its more "tuneful" if you know what i mean.I have a feedback switch but feedback "off" is the norm.

And also playing with the DL103 now set up in the Yamaha DD with help from ace TT man Gerry has given that a more listenable sound.Perhaps Greg would like to try again with those set up tips.

I wont say that the 823A is "better" than the "Chokeoskvi" (ECL82 Doddington) or the PT15 Doddington as they are all enjoyable in their own way.There is no perfect amp,if there was we would all be building it !

All i can say is that i seem to use 832A more than the others.

Roll on the next fest ! :)
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#10

Post by andrew Ivimey »

I like(d) your 832 very much and it was really good to hear it,round here. Quiet what you've done to it now I shudder!

The CCS has completely destroyed the attractive sound (now grainy and harsh) that used to come out of the 6JF7 push pull amp I brough to Witham. I wilbe happy to restore the cathode resistors and if that doesn't get me to heaven then I'm back to SE with this valve ... maybe PSE.
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#11

Post by pre65 »

Hi-just to say its not only my ears.

I posted on the DIYers forum as they have an 832 topic and this reply came today


Quote"I have similar experience when I replaced my 220R cathode resistor on my 832 PP with LM317 with 15R.

Bass is tighter and highs have more air, dynamics and clarity are better too!"Unquote


According to my calcs 15R would give him 83 ma against my 75 ma.

I had thought of making this mod switchable with the normal cathode resistor/cap so what sort of switch do i need ?

Need 2 sets of contacts,one set on and one set off at each setting.I have a 2 pole 6 way switch on PT15 thats not used,would that do ?
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#12

Post by pre65 »

The "must do something different" itch is starting to develop with the 832A PP amp.

Reading up on the "simple EL84" amp that Andrew I is so fond of i wondered if i could reconfigure the 832A input and simplify/improve the front end.They suggest the driver valve can be dispensed with if using a pre amp.

The 832A amp input is really too sensitive for full pre amp input so i wondered about doing away with the first valve (12AT7/ECC81) and using a transformer as the phase splitter.

Any thoughts on that ?

http://www.audiohobbyist.com/images/832/832sch.jpg
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#13

Post by Nick »

If you don;t need the gain, then a TX splitter might work well. Or given you have a CCS in the tail, you could try grounding one grid, and just taking the input to the other one, like Mr I's simple 84 if I remember correctly.
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#14

Post by pre65 »

I don't understand ! HELP !!!!

I thought the idea was to put the same signal on each grid ( G1 ) but out of phase ?

So ground one of G1 (pin 3 or 6) and put the signal on the other ?


ps pin numbers on the circuit diagram are shown incorrectly.(G1 is shown as pins 2 & 6)
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#15

Post by andrew Ivimey »

yep, that's it - frightening huh!

I didn't think it would work for the same reasons you are probably thinking.

It was Mick Mathers who explained it all to me.
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