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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
ethanh
48 posts
 
Thanks, Kehut. Looks like I'll be giving these a try.
montytx
138 posts
 
I would bet the main difference is as mentioned...screening. However, there is an advantage to screening tubes for low noise and matching sections and the gold pins would likely be along the lines of having gold plated inputs on a preamp.

The key element on these tubes is the spiral filament and heavy envelope that keeps noise to a minimum. I'm just hazarding a guess, but I bet the regular tube would sound as good most of the time with a slight variance depending on how well the sections match up.
robxmccarthy OP
10 posts
 
After letting the tung-sol 12ax7's burn in for a bit I'm willing to make some observations in the difference between these tubes and the EH's.

Unlike the E-H tubes the Tung-Sol's aren't dry sounding. There isn't that 600+ hz air, and low volume level playback benefits immensely.

However, there's still some problems. The TS tubes seem to play a bit hotter in the upper end. There's some added sibilance and at higher volume levels rock playback can become a bit grating. I'm not saying that this is a problem for all speakers; mine happen to be rather bright to begin with. Equalization fixes the problem to some degree, and it's definitely easier to fix some frequency ineqaulities than the overall sonic character.

I'm probably going to try out some mullards.
telescope_trade
555 posts
 
Hmmm...Robx,

I recieved my TS 12AX7's today for my 302BRC and although
they improved the bass & center image, they are a bit
hard, and I lost the air that my Dali's have a ton of
that I love. I was blaming burn in, but since you have
burnt yours in, and have basically the same effect, I will
look for other tubes as well. I am trying to improve
on the stock 12AX7's (Which I assume are Sovteks??) but
I put them back in, and the magic came back to the Dali's.
Let me know what you find that you think is better
than the stockers. Maybe some Telefunkins or Mullards??

Bob
montytx
138 posts
 
I'm sorry to hear the Tung-Sol tubes didn't work out for you. The Mullards will likely be juuuuuust right. They certainly have a very lush and harmonic tone to them and are far from the last word in top end extension.

If you start rolling some of your other tubes, the TS might come in handy. If you find that you enjoy tube rolling, don't pass up the chance to try the 5751 (lower gain) tube in place of the 12AX7. Conrad Johnson used to use them in a lot of their gear and they almost always have balanced sections...at least the early milspec tubes tend to.

Let us know how you like the Mullards.
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