yaffstone

The 6n1P-EV is a Russian military tube I stumbled accross. It's supposed to be quiet and rugged (rated for bomb EMP use). If it doesn't work out, I'll switch to E88CC since they're pin compatible. I've seen some positive articles from Eastern block DIY audiophiles who have built SETs using these for the driver stage. The only down side to 6N1P I see so far (from specs) is that the filament current is twice normal for a low gain signal tube. Back to the iron, I may go used if I can find enough.

Maybe you are lucky and just the finish is damaged. If so, you could use a cabinet scraper to get the finish layer off the top, then re-finish. I scraped a pair of LaScalas in an evening and then refinished with Danish Oil. They turned out pretty good with not much work.

I'm going to build a 7 channel surround sound tube amp using 6N1P-EV triode drivers into KT-88 ultralinear push pull. The only output transformers I've found so far are Hammond and DynaClone. Has anyone had enough experience with these to recommend between them? Alternatively, what's the thinking on best output transformers these days? Thanks, David

People are not as easily replaced as speakers. Only one of these come from a store.

Wax should desolve in a non-polar solvent such as paint thinner. Try that since you have nothing to loose.

The IC-150 is the first integrated circuit pre-amp. I've had experience with two of them and they're not the best design. They have some hiss at zero volume which is impossible to get rid of. I replaced the IC op-amps with low noise versions and put in some new caps. This all helped but the hiss was still there and quite noticable. The PSL-2 is a much better pre-amp and is readily available on e-bay. It's extreamly quiet. In general, the old Crown stuff I've seen appear to have dirty and therefore noisy volume or gain control knobs. Cleaning sometimes helps but replacement is the only real way to quiet down this portion. I'm working on a DC-300 now which pops like hell when you power down. I'm going to start with the power supply caps and see where that gets me. Note that the old units used 45V rails for the semi-conductor which is pretty harsh. Newer designs will typically use 12 V .... All that said, 300 isn't bad for the pair and if you have patience, you could end up with good components in the end.

The market has been going nuts. I've seen MKIII's go for as much as 1200 a pair.

Tubes not included but this is a rager of a deal. http://cgi.ebay.com/Dynaco-Dynakit-Mk3-MKIII-tube-power-amps-Upgraded_W0QQitemZ5835621515QQcategoryZ71545QQrdZ1QQcmdZViewItem I am not connected with this item in any way. Just a heads up.

Class A/B or B/A, this was an improvement over the EL-34. I suspect the difference is in the efficiency of the beam design. Far less internal scatter of electrons with the commensurate loss of power and potential noise. So far the X-former is happy. I did lose a JJ GZ34 though. I don't think this is due to the KT88s since there is less B+ draw than before as the bias current is reduced from 100 mA / tube to 50. I think I just got a bad GZ34.

You have mail. I need the upper grills. David

Mick, You have a PM regarding the squawkers. David

I got a free pair of corner horn bass bins today. One walnut, the other mahogony. Neither had the squaker and tweater section or crossovers though. Any one with extra top sections? David

And one from afar. The EQ is no longer in use since I went to the tube amp! Sorry about the pic quality (lack of) The only digital camera I have is the one on my cell phone. No flash, and not enough light in the room without the corner lamp on. Anyhow, you get the idea.

Pics are perhaps attached.

Dee, If you need angioplasty, ask for drug coated stent. They have been amazing at preventing re-stenosis. Please disregard if the diagnosis doesn't fit the cure. Best wishes, David

The Dynaco ST-70 doesn't use KT-88, but mine does. I guess it's not a Dynaco any more, but it sure sounds great. I replaced the driver board with a VAT board capped with Auricaps and Orange Drops and have some ECC-82 (12au7) on order for it. The quad cap was replaced with an under chassis unit while keeping the original quad cap can for asthetic purposes. I've replaced all the sockets with ceramic and am using JJ Tesla KT-88 for output tubes. Currently running bias current of 40 mA and in ultra-linear mode. It's hooked up to the teak horns you may remember which have had their crossovers re-capped with polypropylene. The whole thing just sounds awsome. I'm now considering design and construction of a surround sound (seven channel) tube amp based on what I've learned from the Dynaco. I'm thinking dimond plate surrounded by cherry and point to point wiring under. But back to the question: Are KT-88 better in triode mode than ultra-linear or did they do a good job designing the beam power tube in the first place????

And there you have it. Has anyone compared KT88 beam power tubes wired in triode versus pentode configuration? I have to replace the octal sockets in my heavily modified ST-70 and I need to know whether to go triode on the output section. Beam power tubes were designed to solve the sonic issues with pentode so did they? Inquiring minds need to know.... Thanks, David

I used the Vacuum Tube Audio driver kit with Auricaps and orange drops as well as a Curcio under chassis mount quad cap replacement board. I left the original quad cap on the chassis just for looks but it is disconnected below. I had to modify the Curcio cap design to meet the VTA requirements. Both upgrades include a bias supply and a solid state rectifier section. I used the bias supply on the VTA board since you can set bias individually on each output tube and I kept the 5AR4 rectifier tube. The original Sellenium rectifier is replaced with a silicon diode. As to the filament supply, the KT88 draws 1.6 A while the EL34 draws 1.5. A total of 0.4 amp more load on the filament supply. The VTA driver board uses 3 12AT7 tubes so that's probably a bit more current than the original pair of 7199s as well. So far everythings fine. I leave the cover off for better looks and cooling.

I have a question about the proper bias current setting for a modified Dynaco ST-70. The original design calls for 100 mA accross the EL-34 output tubes. I replaced the driver board and the instructions in the replacement kit were to set the bias to 40 mA. Now I have replaced the EL-34 with KT-88 beam power tubes and am wondering what to do about the bias current. I had to change a couple of resistors in the bias supply to get it set back to 40 mA and it sounds spectacular. The question is, what effect does the bias current have on the sound, tube life, etc? The KT-88 is rated for 230 mA max plate current so I'm way under specs, but I wonder is more better or less? Next question: There is a dual ceramic disk capacitor on the fillament supply center taps. It's 50 years old and rated at 20 pF. I'm going to replace it, but should I go higher in capacitance value? I suspect so but opinions will be appreciated. Finally, I'm waiting for ceramic octal sockets. When they come in I'm going to change to pure triode mode to see what that'll do. So far, I just can't believe how good Yo-Yo Ma sounds!

I just updated my profile. I'm in Norwich.

I'll keep them in VT. They'll be right at home. Yes, Vermont is an oddity. Only about 750,000 people in the entire state and at least 4 forum members.

Ditto on the last post. I have boh LaScalas and Belles. The LaScalas dig deeper on bass even though they should be the same. The longer horn makes a difference also. Better imaging in my opinion. No doubt, the Belles look lots better in the room. LaScalas are rather ugly (obviously my opinion). If you have the right space to sink them into, though like flanking a largish sideboard, they turn out ok.

Thanks for the notes. I figured I was being overly critical. I got home tonight, turned on the system and couldn't hear a thing from my usual chair. Absolute silence. Now Wayne Shorter is playing and it's just great.

I just got a Dynaco ST-70 in original shape. Plugged it in and listened for a while. Not bad but not good either. It had a humm in both channels, a bit muddy, and just not any better than the solid state unit I was hoping to replace. So... I replaced the original 7199 driver board with a VAC all triode design and auricaps. New EL-34 driver tubes, new GZ-34 rectifier, and finally a Curico quad cap replacement board. The unit now sounds awsome on the K-horns. Detailed, punchy bass, really warm. Now the question: If I shove my ear in the tweaters I can still hear a slight hiss. Is this residual from the GZ-34? I could hook up the diode rectifier on the Curico board, but I'd have to loose the GZ-34 and I hate to have an empty socket on the top of the amp. Any suggestions? I could just stop being rediculous, turn up the sound and listen happily, after all, how many hours can one hold their ear to a horn with no sound but a slight hiss? Thanks, David

Painful Reality does not have any contact info info in their profile. I'd take the crown at the right price as I need a backup unit.