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Jolida 202a Tube Rolling Question 12ax7 12at7

Hi guys, a while back I purchased a jolida 202A to power my desktop speakers. I like the combination very much for accoustic/percussion music as nothing can quite beat it. However my $200 14 watt hong-kong amp is better for rock.
Before testing the other amp I thought it was simply a property of the speakers. But after putting the Jolida in my main setup I'm experiencing the same downfalls.

I don't really know how to pick tubes in order to get the qualities I'm looking for, so I was hoping that you guys could help out.

What I like about the sound now:
-Crisp details throughout the frequency spectrum
-Very speedy attack and decay on accoustic instruments

What I don't like:
-Very dry quality in the upper mids / lower HF
-Not enough tube bloom and warmth, too sterile
-The distortion at high power isn't like my little class A, (which just tends to get more blended and bloomy) but instead sounds rather grating in the high end and loses the bass.

Tubes I'm using right now:
4x JJ E34L's - Power
2x Electro-Harmonix 12ax7's in the preamp circuit
2x PhillipsECG 12AT7's as power drivers

I believe that the amp originally came with 4x 12AT7's though.
robxmccarthy
robxmccarthy OP
10 posts
 
Forgot one detail

What I want:
A warmer fuller sound (less dry and sterile)
More in the upper bass (for rock)

Thanks for any suggestions
mechans
3,048 posts
 
You must extirpate the EH 12AX7s. They are the culprit. The tube with the most midrange warmth and bloom is likely to be a long plate Blackburn Mullard ECC83. Any British tube would be better, The Brimar CV4004 is still widely available. The Russian tubes are not known for a pronounced midrange. The Germans make the best of 12AX7 type according to many, however more for clean transparent but strong signals but they have become outrageously expensive the 12AX7 smooth plates and ECC803s by Telefunken are legendary. Also try JJ new production KT77s outputs for headbanging. Do the same with the 12AT7s use Mullard 50s or 60s Blackburn ECC81s
kehut's avatar
kehut
668 posts
 
www.tubedepot.com/ts-12ax7g.html

You really should try this tube. Its a winner. Drive, bass,excellent imaging and stage, with the smoothness of NOS Mullard or Brimar. Many NOS types are nice sounding, but just dont have the drive that make music sound real with the exception of the Tele ECC803s in the 12AX7 family IMHO.

I agree that the EH 12AX7 are not helping you. Your JJ's and Philips are good tubes.
ethanh
48 posts
 
I strongly agree with the above posts recommending new 12AX7s. The EH12AX7s were the stock preamp tubes in my amp and replacing them definitely yielded the the most noticeable and profound changes in sound. I found the the Groove Tubes GT12AX7M to be a huge improvement in warmth, dimensionality, and overall listenability (really helped eliminate much of the hardness I previously heard in the upper frequencies). I think both the Groove Tubes and Tung-Sol reissues would provide you with a much nicer sound than your EH12AX7s provide, and would be a cost effective upgrade if NOS tubes are out of your budget.
Good luck.
montytx
138 posts
 
I agree with the comment to get rid if the EH tubes. I have two Jolida amps and have done a lot of rolling. My favorite combination is the new Tung-Sol reissue ECC803S to replace the 12AX7, the GE 12AT7 where applicable (yes, the lowly GE) and Ei 6CA7 fat bottles for the power tubes.

The Tung-Sols are the only current 12AX7 I like and the only one that doesn't lose out to the 5751. I like it a lot. The GE 12AT7 is very inexpensive and is a little on the warm side, which balances the Tung-Sol nicely. The Ei fat bottles can be had from Kevin Deal at Upscale and are far less strident than many of the current production types.

In order of priority, in my opinion, would be to replace the pre tubes, then the power tubes, and the 12AT7s last.

Having said all that, I do not find Jolida amps to be particularly problematic when it comes to stridency. The Mullards in the pre section would certainly warm things up...maybe too much. I find them to be a bit too much toward the Yin, but they do offer a very nice and warm dimensionality to the mix. I certainly see why some like them.
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