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EL 34 question

I have a VAC PA 35.35 EL 34 push-pull amp, that has had factory upgrades. I was quite happy with it, until I started using a modified SET 300B amp, which has blown the VAC completely out of the water.

I am actually giving thought to selling it, but decided to see if tube rolling might bring it closer in performance to the SET amp.

I have two sets of output tubes that are used, a matched quad of reissue Genelex KT 77, and a matched quad of reissued Mullard EL 34's.

The small tubes are NOS Telefunken 12AU7 and 12AT7, all aound three years in use.

I'm just hoping I can get some insight as to whether better performance can be gleaned from this old amp.

My experience with tubes is recent, lots I don't know, so any old salts that care to help with suggestions would be great.

By the way, the speakers are 94db sensitive custom Tannoy HPD's.

Best regards,
Dan
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jjrenman
279 posts
 
I used to have a pair Dynaco MKIV's which is basically a mono block versions of a stereo 70. Besides extensive tube rolling I had converted them from fixed bias to cathode bias, from pentode to triode operation as well as lowering the negative feedback. Each was an improvement in sound quality. Each was a step toward a SET "type" of amplification but in the end it does not come close to what my current 300b SET does.

In the end only you will be able to decide if you can get your VAC close enough to suit your needs.
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islandmandan OP
1,260 posts
 
Thanks guys, for your responses. I have been more than mildly surprised by the improvement wrought by the modest Assemblge SET 300B, however, it does have fresh factory upgrades w/new carbon film reisitors, Jupitor foil and paper beeswax capacitors, and it just seems to keep getting better and better.

I won't give up on the VAC yet though, until I do a bit more tube rolling. It's still a very good amp, with high current output. I'll see how it goes.

Thanks again,
Dan
justlisten's avatar
justlisten
489 posts
 
Hello Dan

Derrick here, I purchased your Plinius. I was a strong EL-34 guy , until I tried the Plinius.

How many El34s do your VACs use?

I have some Fat Boys and you are welcome to try them out if you'd like.

Shoot me a message if interested
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logenn
91 posts
 
I use two different el 34 based amps and depending on the rest of the system if you use real Mullard XF 2 dual halo el 34's, not the reissues, you will get a huge performance boost in areas of midrange depth and image density or riichness. Also with the right input tubes- long plate square halo Mullards from the 1950's-your bass impact and neutrality will also improve markedly. What you will not get is the liquid immediacy of a 300b but again this also comes at a price. To put it another way, if you voice the system around an el 34, much gains are possible with tubes, cables and pc cords , and cartridges, etc
With the 300 b, you have an entirely different blueprint that requires in most cases a different compliment of accessories.
If the set 300 b has enough power it may be the ideal path.
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