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Hi, all! While I had a bright-leaning system it got worse when I Pro-Gold'd the tube pins. Seems now too electronic sounding.Would appreciate a look at what I have and offer any opinion on getting this warmer ( but too warm kills "realness" for me). Play mostly today's jazz, love clarity, stage depth /spacing, not a boom bass guy/judge (ie) by acoustic guitar string. JoLida 502B w/Svetlana 6550-C/Mullard CV4024 (12AT7) / Jan Phillips 12AX7 ( crucified in prior reviews )-DIY Bob Crump recipe PwrCd /Maggie 1.6 with DIY Mye Stand copy/VH Audio Pulsar IC/Rotel 955 CDP .Many Thanks!
Follow Ups:
Having Pro-Gold'd the tube pins and then having (what seemed) an instant sound change I posted before trying a few changes. One Reply-er offered what I believe is true for me: The Mullard CV4024 (AT) are lean/bright in my system but what made the problem is that the Crump recipe DIY PwrCd puts me over the edge, plastic cups as cable lifters add some hurt, and maybe even the stranded wire as bi-wire jumper substitutes add. I had bought Phillpis AT's with the AX's because they were just $10 but with the Pulsar IC the JP's together were now too warm / slight veil over supporting instruments/percussion, etc / with old IC just horribly muddy. George Benson's guitar is about warm tones but an acoustic guitar string must have the high side /some lean resonance in the pluck to be real to me. The Mullard lean must complement the Phillips traits to get me close to ideal but also right at the edge of disaster if I screw too much with the mix. The Maggies 4-ohm power demands may make the JoLida be "right on the edge" of capabilitiy, too, although my budget appreciates the 502B. I re-installed the Mullards and 18 Ga Pwr Cd / the cable is on the carpet, and the original jumpers are back in. Until I get a different tube mix I think I'm limited in effective tweaks. Where everyone else either hears no difference or celebrates, these tweaks seem to hurt me in each case. Thanks to all for your imputs.
I have mid 80's 4024's which are lean/bright. I've yet to find a use for them.
I'd be surprised if a contact treatment would have that sort of effect. Reclean the pins with isopropyl or plain Deoxit, which is not prone to present residue problems.If you can still find any in a tested grade, the Ei KT-90 Type III is the best sounding output I've heard in a 502, with a nice lush tone. That by itself might do the trick. I've got several matched quads of the early ones when they were still good quality production, but none are for sale.
The 502 has good power delivery, but will quickly lean out if overmatched by the wrong (i.e. current ravenous) speaker pairing. If your system is borderline that way, it doesn't take much to push it over the edge.
The JAN Philips is generally a decent tube, with a long burn in phase. Occasionally one sounds outright spectacular, for reasons I have yet to discover. But most are just good decent tubes. Not what I'd call lean, though. Make sure you have at least 100 hours on one before drawing any conclusion. But if you still want to tone it down a little more, go with a Mullard or perhaps an RCA black plate X7.
5751s are a little dicey in some 502s; the 5751 is NOT a universal X7 substitute. I'd stick with X7s in your 502.
Another trick is to pop open the hood and upgrade the coupling caps to something a little heavier sounding, like a polyester.
Be careful of catching the clarity disease. Before you know it, all the music is gone.
Good luck!
Try Jim McShane he has NOS type 2 KT 90's, that is where I got my stash.regards
Ian
. . . is of what I speak, not the type II.
As I wrote here already, 3 weeks ago I got KT90Ei type III from triodeelectronics.com and they sound extremely good in my amp and have no any reliability problems.
How hot are they biased? Please DO NOT interpret this as ANY sort of knock on Ned/Triode (heck I just stopped in to say hi to him yesterday, he's really such a good guy!) because it isn't a knock AT ALL. Not even one teeny little bit of a knock. Nil. None. Zero.But you may not see any red plates on type IIIs unless you run them over about 28-30 watts dissipation. Also, there are a VERY few type IIIs that are okay build quality (my last shipment had 3 out of 100 tubes that were okay).
So you are one fortunate purchaser - one, I know Ned does his darndest to deliver quality goods so he screened them as well as he could. Two, you may have gotten a good set - God knows how many bad ones Ned had to sort through to find them. Three, you may be using them at a low enough dissipation that you don't see any problem.
Please don't misunderstand me - I LOVE type III Eis. I think the only better tube out there (and it's by a quite small margin) is the type II. If the majority of type IIIs begin to be made right again, I'll definitely put them back in my stock. But I haven't found that to be the case yet - I'll keep trying and let everyone know what I find.
FYI, if you missed it - do an archive search for my listening impressions of the EH KT-90. Disappointing sound... Nicely built, but sound wise not in the same league as the Ei type II or properly built type III.
Amp runs with 500v on plates, bias is automatic with 475ohm cathode resistor - I didn't measured voltage on it meanwhile. Amp is custom-made PP and tubes work in triode. What was really surprised me was much better resolution than with 6550C and it was resulted in bigger,
more transparent and deeper soundstage. Better bass,speed and dynamics were obvious too from the first work hour. And no, no red spots.
Looks like ~30 watts of plate dissipation, with a few on the screens. at .5 v/mA, we're looking at about 70 mA and 430 V plate-to-cathode, less if the screens are at significantly lower voltage than the plates...The acid test is over 400 volts on the plates and screen, and 100 mA+ of cathode current. If no hot spots show up on the screens, and one side of the plates doesn't glow, you've got a good tube.
BTW, a few pairs of GE 6550A I have tried at 380 on plate/screen have gotten too hot at less than 35 W of combined dissipation. The good KT90's are not even loosening their ties, or unbuttoning the top button of their shirts at this rate.
regards,
Douglas
I run Tung-Sol 6550's (black plate, triple getter), RCA CV4024's (red base?), and a Tunsgram 5751 (2 mica), which together provide a good balance in my modified Jolida 801 (similar to the 502). We have similar goals, i.e. I don't like warmth that obscures detail and realistic acoustic guitar is one of my goals as well. Try rolling the 12AX7 with the Tunsgram 5751 (a bargain), a Telef. 12AX7 (expensive), or a RCA 5751 (less expensive). The RCA 5751 was too warm in my system, but might do the trick for you. The T-S 6550's, which I highly recommend, have something to do with my impressions, as well.
Craig,How many hours are on the amp? You won't believe the difference in tone once the components hit 30-50 hours.
What type of coupling caps and values does your amp use?
Some silver IC's are notorious for giving that "WOW FACTOR" SS sound. Which becomes annoying as hell, with time.
Tubes are only a fraction of the total tone of any unit. Best to keep this in mind---or you'll be buying tubes to tqame the system, 'til Kingdom Comes.
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