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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

Showing 5 responses by montytx

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.
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.
montytx
138 posts
 
Nah, if it's a Blackburn production, it will have the Mullard characteristics. There are many Mullards with different labels. The main thing is to look for the characteristic code of B in the date codes.
montytx
138 posts
 
Mullard used the Philips code system on their tubes. The first 3 digits of the code, usually found on the lower part of the glass and very hard to see, are of little consequence. The 4th digit, often beginning right under the first 3, will designate the Philips factory that produced the tube. The "B" indicates the tube was made in the Blackburn factory and is a genuine Mullard, regardless of what the label says. The last 2 digits will indicate the year and month...sometimes another digit indicating the week that the tube was made.

The Telefunken tubes are more linear, pure and focused. The Mullards more warm, thick and texturally harmonic. If I were after all my gear could take, I would go with Telefunken. If I wanted to add a liitle more syrup and give up a little extension, I would go with Mullard.

I hope that helps a little. Personally, I like the reissue Tung-Sol so much I would never spend the extra money on a NOS Tele as they command silly money. Valvos, if the price is reasonable will get you most of the Telefunken sonics for a fraction of the cost.
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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