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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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ryriken's avatar
ryriken
164 posts
 
Try some 6ca7 Fatboy tubes from the 60's.......
ryriken's avatar
ryriken
164 posts
 
Try some 6ca7 Fatboy tubes from the 60's.......I owned a pair of these amps, no way you will get SET sound.....I should of kept them, sorri sold them
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islandmandan OP
1,260 posts
 
Thanks Ryriken,

I checked last night, thinking I had the Mullard reissue EL 34's in but, instead, the EH EL 34's were in. I quickly swapped the Mullards back, and the amp sounded a bit better, but still no match for the SET 300B mesh plates.

I'll see if some 6CA7 Fatboys can be found and give them a try.

Regards,
Dan
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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