Bass tones and low cost tubes for a Jolida 502B


Hi everybody.

I asked in another thread looking for advice with the Jolida tubes but I decided open a new topic focus on it.

I have the Jolida 502B with Paradigm Monitor 11 speakers, with Xindaq DAC and reader, waiting to upgrade this periferials.

I really like to hear jazz as Joshua Reed, Herbie Hancock, Spyro Gyra, Chick Corea, Yellow Jackets... rock as Everything But The Girl, Depeche Mode, even Metalica or Rammstein... and electronic DJ"S as Armin Van Buuren, Oakenfold, Chicane, Enigma...

At this moment I have a Electro Harmonix salad in the Jolida, last owner legacy.

The sound that I have is very "shinny" or in excess sharp...with a feel of "we need a subwoffer", despite the Paradigme Monitor 11 and the 502B punch. I'm conscious about some room reflection yet but I can't improve it more...family matters :)

In my country Costa Rica, a $45 individual tube will cost around $110 with the custom taxes and shipping costs. So I have to be low profile about it.

I REALLY APPRECCIATE YOUR ADVICE ABOUT IT! I know is difficult but a good tube is a good tube and a poor brand too.

Reading the reviews on tube depot and tubestore on this tubes:

AX7
large plate AX7's ?? I read that this get more medium bass and tight bass presence:

- BLACK SABLE Sovtek 12AX7LPS
- SOVTEK 12AX7LPS Preamp Vacuum Tube
- JJ ECC803s / Hi-Performance 12AX7 / tubedepot.com

- Mullard 12AX7 / ECC83 / thetubestore.com
""Microphonics is not an issue despite the larger that average plate structure. The transconductance on my sample was the same as two NOS samples I measured. Not really high gain at all, but a real good noise floor and a nice smooth tone that doesn’t encourage ear fatigue the way some preamps can be."

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AT7's:

- 12AT7 / ECC81 Mullard / tubedepot.com

or

- Mullard 12AT7WA / CV4024 / thetubestore.com
"The NOS Mullard 12AT7WA / CV4024 tube is low noise and long lasting. This 12AT7 tube is a very good choice for hifi preamps, driver stages, and guitar amp reverb circuits. The Mullard 12AT7 is original production from Great Britain."
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For the KT88;s

- Sovtek 6550WE / tubedepot.com
"The Sovtek 6550WE has higher gain / output than most others and really has a ballsy sound. Recommended for any bass application and most Hi-Fi amps. This tube has a slight bump in the midrange making it a great choice for lead guitar."

- Sovtek KT88 / thetubestore.com
""The Sovtek KT88 tube has smooth, warm and clear with excellent imaging. The bass (except for the very bottom end) is tight and the high end is crystal clear. The separation of parts and balance is better than any of the 6550 tube types."

- JJ KT88 / thetubestore.com
"The JJ KT88 tube has the best imaging of all the tubes in this category. The bass is unique in that it compresses the very bottom end. This provides incredible bass response without ever losing control. Overall a great KT88 tube for orchestral, opera, and jazz music."
edoll

Showing 7 responses by edoll

Thanks Xti16... that Octave V70SE...OMG! It's a treasure!! Germany power!

@Ghosthouse: I really appreciate your advice, I already read your post "Tube upgrades for Jolida 502B?" Thumbs Up!!!!

I need to tell you that your advice is very important, as a Jolida 502B owner...don't let it many time in the bench!

About the tubes, I was looking at the web info about the Winged SED reviews and each one said the same: very reliable tube with tight bass.

As a retired bass player, I really understand what means bass heft...so that is a very good direction to me.

I think maybe it will be interesting attach the Winged C with the Mullard's AT and Ax's... as this could represent around $350 at USA but certainly $600 after customs here in Costa Rica. Think that Winged C get me that money back for sure...

I'm trying all this days to do my homework, learning about tubes. And the Bias issue it is a big issue to me, I never hear about it until reading the topic at this forum.

So, sorry but I need to bother you Ghosthouse! and any other guy of course if has this knowledge and experience.

FYI... I don't have the manual, just a scan page that I found at polkaudio forum...weird certainly!

As I try to understand, this is the basic procedure to manual Bias a Jolida 502b:

1- Unplug the AC power cord from the Wall and replace the tubes / replace the AC power once got replaced the tubes, with God help and if Danica Patrick keep quiet without crashes...

2- Remove all the audio inputs (??) what for ? not necessary to know ? :)

3- Depress the AC power switch to OFF

4- Adjust the bias levels to the lowest setting = counter clockwise until cannot turn any further (v3, v4, v7, v8)

5- Make certain the left and right speakers cables are attached

6- Volume control at lowest setting

7- Turn On the Amp

8- Let the amp warm around 30 minutes ??

9- Get the multimeter set to D.C.V. / milivolt range setting

10- Get the 5 female jack terminal behind the Power Tubes / Black or Negative probe goes into the center terminal = #0

11- Red or Positive probe goes in the hole numbered according to the tube I want to bias (v3 correspond to hole #3, etc)

12- Starting the bias procedure by turn the relative screw via the small recessed pot closest, clockwise until 45-55 millivolts or .045 to .055 appear at the multimeter -It is true that is better set 45-46 to extend the tubes life ?

13- ?? What else ?

Sorry if my post is too confuse to read fellas...it will be my very first time as electrician and learning this stuff from english language, I'm not very good with both themes!

Thanks again!
Thanks Cayin!! I read before that Sovtek's has pretty good construction and has a very good reliability.

Tonight I installed a quad match of KT88's EH that I received at final 2009 . Turn on the Jolida and plum! One of the left channel got blowed?

I'm in Costa Rica, I don't know if some transportation issue happened.

So, I'm back with the original 65550's EH....

So, I'm waiting for a little bit more of advice to put my order @tubedepot or tubestore, the only store's that I have some reference in USA.

Thanks buddy.
Thanks Johnsonwu, can you confirm if the bias is Bias Settings: 50 millivolts + 5 mV ?
Newbee, i'm consider the KT's , your conclusions are exactly as happened with my 6550 EH's vs the Sovtek Kt88's (the few hour that the KT's works before the blow they was with more bass delivery but maybe eith some "enclosure" or "inside the box" sound.

But i'm sure that after two swaps at 4 years the amp has been never biased.

Si, if I get new KT's, and with the Mullards AT's and AX's and doing the Bias procedure, hope to share you and enjoy a new sound as I never have it before.
Well, after compare your recommendations and research in another sites and forums, finally I bought new tubes at Upscale Audio tonight.

I found very good references of this store, especially very good references from Kevin Deal everywhere.

I think I'm very lucky to find with Kevin four matched SED Winged C KT88"s, and a matched pair of Mullard CV's 4024 and another Mullard's 12AX7 (this one the most popular)

I really was in love of the Mullard AT7 CV 4004, but this tube is very expensive, around $90 and this price rise to ¢195 each tube after customs here in my country...insane! That exceeds my budget and compromise have the KT's winged C...

The Jolida at this moment has never been biased, at least the last 4 years...and operate with the basics 6550 EH's and THREE!! 12AT7 EH's and just one 12AX7...

I hope that doing Bias Procedure, swap the EH's with the Winged C SED KT88's and get the new pair of 12AT7/ 12AX7 Mullards, results in a sound experience as I never have it before with the actual status.

Thanks a lot guys for your advice.

I learn a lot from each one of your posts.