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I'm using Curcio's driver replacement board in my Dynaco ST-70. Love the sound and quality of Joes work. But lately I'm longing for a warmer sound. The driver tubes are Amperex 7308 JANs made in USA. Are there any recommendations for different tube types in this position for a warm sound while maintaining the wonderful detail. Current output tubes are JJ Teslas and recitifier tube is original RCA.Actually this is my second question. When the recitifier tube starts to fade is there any sonic impact. Sadly all the original tubes in this unit have failed or just gotten to weak. The recitifier is the only original remaining tube, is it still good??
Charles
Follow Ups:
If you want a warmer sound try the 6CG7/6FQ7. A lot of people like the RCA cleartop that cost about $20 each.Dave
If it is specifically a 7308 you want, I will mention one that probably won't be by others. Try La Radio Technique 7308's (French). Very nice, very smooth.
I know this is going to start a discussion, but I am going ask the question. Why don't you Solid State the supply. Good regulation, no heat and it reduces the burden on the power xformer (no 5 volt filiment current). What effect would this have on the sound quality of the amp.
Have you thought of using 7308/E188CC Mullard GB Gold pins, there are 10pcs NOS in an auction on e-bay at present.Nicolas
I just read a review and Dick Olsher really likes the Richardson "Bugle Boy" 6922/6DJ8. They are are, according to him, JAN tubes that are carefully selected and burned in. Richardson owns the Bugle Boy name. Don't know the price though.The review was on Enjoy the Music, an Audion PX 25 amp.
Les,I think Dick should stick to reviewing turntables and not tubes. Those things from Richardson sound like cr?p.
Mike
Hi Mike,I don't use this tube, but Dick really liked them in the Art Audio PX 25 amp.
If your 7308 JAN is a green or red label, go to the earlier versions with white labels, they sound much more like a better detailed Bugle Boy. I am especially fond of the USN-CEP versions (middle 60's) for being musical. But second to that I agree with the recommendation of the Bugle Boy. There are some 6922 USN-CEP's as well and they also sound very good.
Agreed on the 7308. I have the mid 60s USN-CEP. I also have some marked Hewlett Packard with the same date codes. To my ears these are both fine sounding tubes.Never tried the later 7308. Loves these so much never had the desire!
My vote would be for the Bugle Boy. It does not have quite the detail of the 7308, but it is a much fuller, warmer sort of sound. More dynamic and punch as well, with good extension at the extremes. A tad bit loose in the bottom compared to the 7308. I love the Amperex 7308 as well, but by comparison it is a leaner less warm/rounded sound. Still, a wonderful tube. I like them both.In the Amperex family, and I have by no means listened to everything, good detail generally comes at a price: too much energy on the top. The 7308 seems to be about the only one that does not have this problem. To tame the topend generally comes at the expense of some detail, i.e. the Bugle Boy, but there is still plenty of detail!
I am a little bit of a novice. I have the triode board. I have found that when I replaced teh rectifier tube (mines was original) it made a mall difference (more warm) The original was a Mullard and so was the replacement ($80+ for NOS).I have found that the Svetlana output tubes are plaesant to listen too.
Second the Svetlanas, my favorite EL-34 in this amp, and a very reasonable price.Jim
I don't know about your 7308s, but if your rectifier is starting to get weak, I would expect to notice a reduction in dynamics as the rectifier loses its ability to replenish current to the filter.Why not have it tested? A good guitar shop might have a tube checker that will at least check for good emission.
Cheers!
Jim
It's hard to find a place to test tubes these days. The dynamics are getting a little flat lately. Maybe I'll get a new tube anyway. Ya know this one is going to go sooner or later anyway. I'll look into what the going prices are for, RCA, bugleboy or mullard. I think I did see a Siemans on Upscale audio.Is there a difference with large/big bottle vs the standard RCA type I already have?
Charles
Don't rule out the ElectroHarmonix 5AR4 as an inexpensive new production unit. Once again, a good guitar shop should stock these, and it will certainly tell you whether or not you need to find NOS right away, or if you can hold out for a good deal.Best,
Jim
a
I was hesitant to repllace the rectifier, but the change does make a difference, not huge but worth it.
Charles,A tired rectifier starts to sag too early. Sometimes, guys think the power tubes are tired, as the tone with a tired rectifier is similar. Weak transients, early onset of distortion, flabby bass, odd overtones in midrange and high when the unit is pushed.
As stated by the others, best to try a new replacement unit---and I like using new rectifiers on healthy power tubes, as the new rectifier can push a marginal power tube over the edge.
This is from upscale audio:""5AR4/GZ34 -says made in Great Britain, but Japanese made, based on Mullard design. Super quality. Branded GE,
Raytheon, RCA, etc $45 each5AR4/GZ34 - Mullard made in England, branded RCA, GE, Dumont, etc. We have a super stock of perfect ones! The most
famous 5AR4 ever. Call for price.5AR4/GZ34 - Sylvania large bottle U.S. made excellent quality in white box. $out each ""
This is from Triode:
USA Made Philips
large bulb 5AR4/GZ34.
These are unmarked &
in white boxes but we
guarantee that they're
the genuine item. Note
that they're slightly
larger (1 1/2"
[38mm]wide by about
3 1/4" [82mm] tall) so
check clearance on
your amp before
ordering.
Hi,Have you thought of using :-
GZ34 Mullard doulble d-getters made in Holland or
GZ34 Valvo doulble d-getters made in Holland or
GZ34 Philips/Miniwatt doulble d-getters metal base made in Holland
SO airframe there are plenty of Tubes NOS out there is the world you just need to know where to look, and they are not tired out
ones. But real NOS/NIB types.Nicolas
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