Jolida 801 triode mod, sound??

00p225 · « **on:** 18 Nov 2004, 11:12 pm »

Has anyone converted their Jolida 801 from ultralinear to triode, and if so, any comments on the sound? I'm going try it on mine, but was looking for some input on the differences. Thanks in advance.

Zane

Bill Baker · « **Reply #1 on:** 19 Nov 2004, 01:41 am »

HI Zane,
These question was recently mentioned at the "other" audio discussion site. Here was my response:

The 302/502/801 can easily be converted to triode (I haven't personally done it to the 801 yet) but the transformers can't always handle it. There have been cases in the past where the transformers would fail after a while.
I can say that I have several customers that have purchased pieces from me and have been running their Jolida's in triode for some time without a hitch. I even have one that has been in tride for several months. It's a 302/502 amp that I switch between EL34s and KT88s. This would obviously be done at your own risk. When I build these amps in the triode mode, it voids any warranty offered. To protect my own ass, I don't recommend it.
The 502 sounds very sweet in triode.

Yes, these amps sound very sweet in triode mode and for the most part, I have not had any personal problems with any of the amps I have built that are running in triode. Again, to protect my own ass, I do not recommend it. If you do convert your amp to triode and have problems daon the road, please don't come back at me. (But please do let me know your thoughts on the sound).

00p225 · « **Reply #2 on:** 19 Nov 2004, 01:43 pm »

Thanks for the quick reply. The Jolida I purchased was a demo unit from my local dealer. It's been on the shelf for several years, and is the model SJ 801a. Being a demo, there is no warranty.

As far as changing this one to triode, I was planning on running a pair of switches, one for the ultralinear taps and another for the bridging resistors so this can be switched from triode to pentode and back at will (with the power of when switching). I'm glad you mentioned the transformer failures, the speakers I'm driving are a pair of 1989 vintage Polk SDA-1C's which have a nominal impedance of 5 ohms, but have some fairly complex impedance dips for the amp to deal with. I'm currently running the 4 ohm taps on the Jolida, and it sounds nice, smooth, and lush now that it's been running for about 100+ hours, but was hoping for a bit more detail running in triode. Right now, it doesn't sound strained at all, but with the power loss in triode, I may find myself pushing it too hard so perhaps it's better left ultralinear, and possibly upgrading the signal coupling caps for more detail and clarity. Thanks again for the info, it's greatly appreciated!

Zane

Bill Baker · « **Reply #3 on:** 19 Nov 2004, 03:21 pm »

Hi Zane,
I would not run the 801 in triode with the SDA's. I am a big fan of the old monitor series of Polk. I had several pair of them but found they like more power. The last pair I had were the SDA-2 and they sounded very nice with a 502 but not in triode.
Sounds like you have an older 801 with biasing done on the underside? A few well thought out mods within this amp can really bring out a lot of inner detail and resolution.

00p225 · « **Reply #4 on:** 19 Nov 2004, 07:12 pm »

Yes, the bias pots are on the bottom, kind of a pain. The tube compliment I got with this one are nice, Svet 6550c's, 1980's Ratheon 6SN7wgts, and a Sovtek 12AX7LPS which I like, very detailed. I did roll some vintage 12AX7's and the next fav was a 60's vintage ratheon.

Well I think I'll keep this one pentode per your suggestion. I'll just go ahead and upgrade the coupling caps and signal caps, possibly the volume pot as well. Other than that, this one should do ok. I don't listen at ear splitting levels, but once in a while I like to rip up the floorboards with classic rock, and the SDA's do like a lot of juice to open them up. Before the Jolida I ran my homebrew tube preamp along with a Soundcraftsmen PM-840 mosfet amp of 200wpc into 8ohms, the polks really like this combo.

Thanks again for the info!

Zane

Bill Baker · « **Reply #5 on:** 21 Nov 2004, 09:20 pm »

I think you will find some well thought out critical upgrades wil make quite an improvement. Look at the following areas:

Coupling caps
Diodes
Grid stop resistors
Internal wiring

Have fun and keep me posted.