I guess I could swap out the input cap and try my Cetron 5R4WGB - or ask Santa for one of those nice EML274B, but neither are likely to fit the spacing on the chassis, and it would be just a little bit silly to invest more in the rectifier than the rest of the amp cost me out of pocketMaybe Santa will bring you a NOS Mullard GZ34.
stock circuit value is .1mF - I ordered some Solen Tin Foil films that I very much enjoyed in other projects
yup - typo , and come to think of it, I may have mistyped that more than once before
Thanks for posting your impressions Chris. I should have known I'd be the only one who preferred no NGFB...I thought it might have been due to the full-range drivers I was using, but maybe its just the sound me and my wife like...maybe we need to clean our old ears out
Anyway, glad you like it, the extra power certainly helps, even with single Mark Audio drivers. I find 6 watts will do the job very nicely, but the 15W or 17W or whatever of the Simple PP does it easier/better.
Anyway, glad you like it, the extra power certainly helps, even with single Mark Audio drivers. I find 6 watts will do the job very nicely, but the 15W or 17W or whatever of the Simple PP does it easier/better.
Thanks for posting your impressions Chris. I should have known I'd be the only one who preferred no NGFB...I thought it might have been due to the full-range drivers I was using, but maybe its just the sound me and my wife like...maybe we need to clean our old ears out
Anyway, glad you like it, the extra power certainly helps, even with single Mark Audio drivers. I find 6 watts will do the job very nicely, but the 15W or 17W or whatever of the Simple PP does it easier/better.
I haven't played with defeating the feedback yet - will probably try that over the next couple of evenings
Those Emission Lab tubes definitely rate a 10 on the old drool meter.
I have an old Mullard 5AR4 in my HK amp, which is taking a rest at the moment. You're more than welcome to try it out.
jeff
Those Emission Lab tubes definitely rate a 10 on the old drool meter.
I have an old Mullard 5AR4 in my HK amp, which is taking a rest at the moment. You're more than welcome to try it out.
jeff
why the heck not? - but let's wait for the snow to stay melted
I'll likely be delayed at least a few more days pulling the trigger on any new outputs for this baby, and wonder if anyone has opinions or experience regarding to the JJ EL844? It looks like the manufacturer hasn't updated their web-page yet, but several distributors are posting availability of several new models, including "reduced power, more balanced frequency response" EL84 (also new fat bottle 6CA7 and 6550)
http://www.eurotubes.com/euro-u.htm
An externally hosted image should be here but it was not working when we last tested it.
now exactly why anyone would intentionally design a 30% lower power output I'm still not clear about yet, but only the hearing would really give the answer to that
and I wonder how ES feels about the logo - who wouldn't want to ride shotgun with ms high output
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Ok.
That's a bit of a head scratcher, given that the current production has a good reputation.
jeff
I don't think it's intended to replace their "standard" EL84 - perhaps its performance is something that musicians would more appreciate? George, any thoughts there?
Good point. These new tubes seem to be all over the guitar sites.
Specs For New JJ Tubes: 6550, 6CA7, EL844 - The Gear Page
jeff
I just got email from CE Distribution, the other side of Antique Electronics's warehouse. They are claiming the new EL844 "has lower gain for a smoother tone". The spec sheet shows a 9 watt plate rating VS 12 watts for the EL84, yet CE claime that these are drop in replacements in EL84 amps. They do seem to be aimed at the guitar amp market.
There is some speculation that they are derived from the old Russian EL83/SV83/6P15P tube which doesn't handle the Simple P-P voltages well. To me it looks more like a 6AQ5 in a 9 pin bottle. I can find no references to anyone actually using these tubes on the internet, so I would wait until someone else melts a few.
There is some speculation that they are derived from the old Russian EL83/SV83/6P15P tube which doesn't handle the Simple P-P voltages well. To me it looks more like a 6AQ5 in a 9 pin bottle. I can find no references to anyone actually using these tubes on the internet, so I would wait until someone else melts a few.
typical operating points?
so I finally got around to taking a few measures on the amp a few minutes ago, and wonder if I need to worry about life span of the output tubes (which according to Dave, whom I'll trust 'cause I certainly can't read the Cyrillic, are the 6P15P-EV after all)
anyway, with 123V coming out of the wall, after about 10 minutes warm up, and with 5 load on 4ohm tap (the closest value loads I had on hand) I'm getting the following readings:
12AT7 (NOS Sylvania 6201)
1 = 243 / 250 (L/R)
2 = 115 / 109.5
3 = 116 / 110.9
6 = 110 / 109.6
8= 1.015 / 1.032
Outputs
plates = 368 (average of all 4)
screens = 370 (average of all 4 - 820R for pentode mode as suggested)
cathode = 11.06 / 11.16 / 11.23 / 11.47
1) do these make sense?, and
2) as noted earlier, I wouldn't mind rolling at least one set of different output type/brand, but don't want to be replacing them like this was a Vox AC30, and wonder if any of these operating should be dialed down a bit even for the JJ's, etc.?
edit:
George, thanks for the above post -( while I was composing the above masterpiece ) - you've more or less confirmed that I should probably consider something other than the SV83 clan for this one
so I finally got around to taking a few measures on the amp a few minutes ago, and wonder if I need to worry about life span of the output tubes (which according to Dave, whom I'll trust 'cause I certainly can't read the Cyrillic, are the 6P15P-EV after all)
anyway, with 123V coming out of the wall, after about 10 minutes warm up, and with 5 load on 4ohm tap (the closest value loads I had on hand) I'm getting the following readings:
12AT7 (NOS Sylvania 6201)
1 = 243 / 250 (L/R)
2 = 115 / 109.5
3 = 116 / 110.9
6 = 110 / 109.6
8= 1.015 / 1.032
Outputs
plates = 368 (average of all 4)
screens = 370 (average of all 4 - 820R for pentode mode as suggested)
cathode = 11.06 / 11.16 / 11.23 / 11.47
1) do these make sense?, and
2) as noted earlier, I wouldn't mind rolling at least one set of different output type/brand, but don't want to be replacing them like this was a Vox AC30, and wonder if any of these operating should be dialed down a bit even for the JJ's, etc.?
edit:
George, thanks for the above post -( while I was composing the above masterpiece
) - you've more or less confirmed that I should probably consider something other than the SV83 clan for this one
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Based on a 270R (?) cathode resistor, your tubes are dissipating (on average) about 15 watts each. Or did you go with a larger cathode resistor?
Do they the plates glow in the dark?
jeff
yup the stock 270R
Well, they are thermionic devicesDo they the plates glow in the dark?
jeff
- actually no more than standard heater glow Just thinking about this a bit - there's likely not enough initial voltage drop across the Hammond choke ( 158S = 60R), which I substituted for the 150R. I'll swap those out first (or maybe even increase the R a bit) and retest.
Even so, it looks like I'm in the market for some more robust outputs, and the new EL844 should probably not be on that short list.
So what are reasonable for plate & screen operating voltages? The triode connected El Cheapo has higher forward drop 5R4 with much more PS filtering and measures 358 plates/ 355 screens, 10.4 at cathodes across shared 150R. It's been running a set (from I think same batch) of 6P15P's for at least a year with as of yet no problems.
That 6P15P-EV data sheet shows 250V for plate and screen. Obviously, they'll take a lot more than that, but with a slightly reduced life span. Your El Cheapo numbers suggest the tubes are running at their dissipation limit.
If you could get the B+ in your Simple P-P down to 300V, then the 6P15P's would be running at there limit power wise, and could last for a long time.
Or, leave the PS alone and spring for a quad of 6P14P-EV's.
jeff
No need to spring... just drive up the mountain (i'll have to compare the 4 he has to some labeled ones and see what they are)
It is the screens of the SV83 (6P15P) that are particularily delicate.
dave
group therapy on the internet, cool
OK Dokee, Dave: per my earlier documented confusion, I thought that's what these were - I really should start reading the labels (when there).
Once Simple P/P is dialed in, the El Cheapo should probably be revisited - as previously discussed, for more than just a "cosmetic" rebuild.
that could easily I think be directed to the host of this particular vendor forum, his-self being a musician I think - folks whom are renowned for wanting all 11 of it
no, not inches
but seriously, I think that particularly with guitar amps, there's magic reputed to reside on the other side of the red line
The best sound is found by trying different plate and screen voltages, if these happen to be outside limits, then what do you do. If within limits then all good...George found a couple of good operating points for the JJ EL84, something around 325 or 340V across the tube and on the screens was one of them if I remember right, there's a post of his somewhere on this forum...
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