[Krispy Kirk]

[I trust the moderators will move this post if I've put it in the wrong circle...]

I've owned a second hand Jolida 302b for a few years and have lately done some tinkering with it.  There is an old archived thread (in (David) Ellis Audio > https://www.audiocircle.com/index.php?topic=17354.100) with mucho good info about mods that can be done to this amp (in fact, that one thread is the main reason I joined Audiocircle!)  Unfortunately, I am unable to post any replies (perhaps because it is archived and not an active thread?)

My 302b was remanufactured for its previous owner by Bill Baker in his old Response Audio days (I'm guessing about 10-15 years ago) and should more accurately be identified by its RA nomenclature IIRC: "Bella EXtreme 3205".  I've discussed the amp with Bill personally but he was unable to help me further determine its provenance since a flood had destroyed his company records from that period.

This is the point where I wanted to chime in and re-start the conversation about 302b mods: the one mod everybody seems to accept as essential is bypassing the balance control.  Bill did this to my amp and I've lived with it that way...until last week.  From what I understand, the stock Chinese balance pot is junk.  Okay, I totally get why you'd want to cut it out of the circuit especially if this is the easiest and quickest way to improve soundstaging.

But what if you need a balance control?  What if you have a weird shaped room that needs a boost on one side?  What if you play source material that was poorly recorded and need to occasionally be re-balanced?  Or, horror of horrors, what if your hearing is damaged but mostly in just one ear and you hear the world "out of balance"?

I won't say which case I'm in but let's just accept that I need a balance control on my amplifier.  There is nowhere else in my system where I can adjust channel levels independently.

So what did I do?  I opened up my Jolida/Bella and poked around.  Then I got out my Parts Express catalog and ordered an Alps 100k "Blue Velvet" volume pot (pretty sure it's the same one as Bill installed as part of his modification process).  When it arrived, I slapped it in where the stock balance control had been.  Then I split the channel input leads and sent the right channel through the second Alps pot.  Now I have dual side-by-side volume controls and the ability to alter the balance in a super-smooth way.  I believe this modification is superior to your basic "bypass the balance pot and forget about it" modification.  The amp has indeed never sounded better.  FWIW I'm running all EH tubes (KT88s for power), a Pangea AC-9 power cord out back, and Vibrapods underneath.

Of course, while I was poking around I saw that the real culprit for all kinds of grunge, mistracking, and foul play is the stock input selector switch.  It's another Chinese junk piece and it's next on my list of things to replace/upgrade inside this amp...

What do you think?  Has anybody else out there contemplated/attempted to undo the standard balance bypass mod on a modified Jolida 302b?

[Early B.]

Years ago, I owned a 502B which is essentially the same amp. I did some mods to it, so my suggestion is to evaluate whether or not you'd be better off selling the 302B and upgrading instead of pouring more money into upgrades. That amp was built with low grade parts throughout, so you could spend a ton of money on more upgrades and still not be satisfied with the quality of the sound. My 502B taught me a lot about how to buy components based, in part, on the quality of its parts.

Consider your alternatives -- that's all I'm trying to say.

[Krispy Kirk]

To put it in perspective, my 302b sold for maybe $800 new.  The Response Audio remanufacture process cost another five or six hundred bucks.  By the time I saw the amp for sale on Audiogon, it was going for $600.  To be fair, this is not the most I've ever spent on an amplifier.  I purchased a Jolida 502 new from Audio Advisor back in the late 90s for over $800.  Back then, that was a fortune to me.  I was running an Adcom pre-/power combo (GFA-545/GFP-555ii that together cost me nearly $800) but the Jolida 502 didn't seem to raise the sonic bar enough for me so I sent it back.  That was 20 years ago...

The Alps pot I put in cost me $13.75 plus a few cents for the solder.  Almost every other part that matters on my amp has been upgraded with an audiophile part - it even had an $85 audiophile-grade mains fuse in it when I bought it! - this is why that junky selector switch jumps out at me. 

I appreciate the advice about going in another direction but I already have a house full of gear.  A quick inventory of just my amps: NAD 2600A, Jolida 302, Jolida 1701, a pair of Audiosource AMP-100s, and Pioneer & Onkyo receivers.  After 30+ years in this hobby, I'm done "chasing a sound".  From now on I want to improve (via tweaks/mods) the sound I already have!   

[Steve]

To put it in perspective, my 302b sold for maybe $800 new.  The Response Audio remanufacture process cost another five or six hundred bucks.  By the time I saw the amp for sale on Audiogon, it was going for $600.  To be fair, this is not the most I've ever spent on an amplifier.  I purchased a Jolida 502 new from Audio Advisor back in the late 90s for over $800.  Back then, that was a fortune to me.  I was running an Adcom pre-/power combo (GFA-545/GFP-555ii that together cost me nearly $800) but the Jolida 502 didn't seem to raise the sonic bar enough for me so I sent it back.  That was 20 years ago...

The Alps pot I put in cost me $13.75 plus a few cents for the solder.  Almost every other part that matters on my amp has been upgraded with an audiophile part - it even had an $85 audiophile-grade mains fuse in it when I bought it! - this is why that junky selector switch jumps out at me. 

I appreciate the advice about going in another direction but I already have a house full of gear.  A quick inventory of just my amps: NAD 2600A, Jolida 302, Jolida 1701, a pair of Audiosource AMP-100s, and Pioneer & Onkyo receivers.  After 30+ years in this hobby, I'm done "chasing a sound".  From now on I want to improve (via tweaks/mods) the sound I already have!   

You made a smart decision to go dual volume control vs balance and single volume control.

Continued good luck on your adventures.

steve

[bummrush]

Qed int. I have used a ganged volume control,and in essence needs no separate balance control. But all the technical stuff of it all is beyond me.

[Early B.]

To put it in perspective, my 302b sold for maybe $800 new.  The Response Audio remanufacture process cost another five or six hundred bucks.  By the time I saw the amp for sale on Audiogon, it was going for $600.  To be fair, this is not the most I've ever spent on an amplifier.  I purchased a Jolida 502 new from Audio Advisor back in the late 90s for over $800.  Back then, that was a fortune to me.  I was running an Adcom pre-/power combo (GFA-545/GFP-555ii that together cost me nearly $800) but the Jolida 502 didn't seem to raise the sonic bar enough for me so I sent it back.  That was 20 years ago...

The Alps pot I put in cost me $13.75 plus a few cents for the solder.  Almost every other part that matters on my amp has been upgraded with an audiophile part - it even had an $85 audiophile-grade mains fuse in it when I bought it! - this is why that junky selector switch jumps out at me. 

I appreciate the advice about going in another direction but I already have a house full of gear.  A quick inventory of just my amps: NAD 2600A, Jolida 302, Jolida 1701, a pair of Audiosource AMP-100s, and Pioneer & Onkyo receivers.  After 30+ years in this hobby, I'm done "chasing a sound".  From now on I want to improve (via tweaks/mods) the sound I already have!   

If you're on an audio forum asking us about more mods, you're still on the "chasing a sound" merry-go-round, and it doesn't stop, even after 30+ years in this hobby. I'm predicting that you won't be satisfied by doing more mods to your 302B. Before you dive in deeper, one option is to forget about the mods and enjoy your system as is. Another option is to sell all of your amps and invest in a "mid-fi" amp such as an Odyssey Stratos. If you do, prepare for a mind blowing sonic experience.
 

[Krispy Kirk]

Why do I get the feeling everybody on AC is selling something?  Heck the "industry" circles alone make up over half this site!

$2700 for a pair of bespoke monoblocks isn't what I (or anyone else) would call "mid-fi".  But then again, I'm a real person living in a real world with a mortgage, taxes, car repair bills, several other (expensive) hobbies, and a very modest income.  The old rules - four figure price tags are typically the entry level point of the high end - still apply for the vast majority of us...

But if you want to wax philosophical comparing/contrasting "chasing a sound" with "diving in deeper" with "enjoying your system as-is" I'm totally game! 

*Some background about me before we go any further: https://www.audiocircle.com/index.php?topic=158148.msg1689785#msg1689785

[Tyson]

Why do I get the feeling everybody on AC is selling something?  Heck the "industry" circles alone make up over half this site!

$2700 for a pair of bespoke monoblocks isn't what I (or anyone else) would call "mid-fi".  But then again, I'm a real person living in a real world with a mortgage, taxes, car repair bills, several other (expensive) hobbies, and a very modest income.  The old rules - four figure price tags are typically the entry level point of the high end - still apply for the vast majority of us...

But if you want to wax philosophical comparing/contrasting "chasing a sound" with "diving in deeper" with "enjoying your system as-is" I'm totally game! 

*Some background about me before we go any further: https://www.audiocircle.com/index.php?topic=158148.msg1689785#msg1689785

I actually totally understand what you are saying.  I think it takes a while (and a lot of experience) to finally settle on the type of sound that you actually prefer.  It's a bit wasteful because it mostly involved buying new gear and trying it out for a while.  Eventually the stuff you like will stay and the stuff you don't will end up in storage. 

You have an amp now that you love, and just want to make it better.  I totally get that.  It sounds like all the parts quality is fairly maxed out already, so you might look at the tubes.  What tubes are you running in that amp?  And have you tried the Herbie's Audio tube damper rings? 

And nice score with the Elac speakers - I've heard them several times and they are phenomenal. 

Oh, and to answer your original question re: the dual volume controls - that's a far better solution than a single volume control followed by a separate balance control unit.  You get the functionality you want (the ability to dial in the balance) while retaining the fewest devices in the signal path possible.  Nicely done.

[Krispy Kirk]

Thanks Tyson for the nice reply.   

Re: tubes.  When I got the amp, it was equipped with NOS Mullard pre/driver tubes (12AX7 & 12AT7) and Shuguang "Treasure" 6CA7-Z power tubes (Chinese "fat bottle" EL34s with black glass).  After researching how ridiculously expensive these tubes would be to replace, and not knowing how many hours were on them (amp was bought used on Audiogon remember), I almost immediately yanked them and stored them away for safekeeping.  I wanted spares and these would be very nice ones indeed.  They sounded very sweet and seductive.

First tubes I tried were JJ Electronics (formerly known as "Tesla") 12AX7/12AT7s and Valve Art EL34s.  This was a nice, well-balanced sound (for the money) that I could've happily lived with forever.  But I knew there was a fatter, punchier sound out there and I was determined to find it.

For the record, I've used this amp exclusively with a pair of 1989 Klipsch Forte II (a 36" tall three-way with horns up top and a 12" woofer + 15" passive radiator that dig down to the low 30's, rated sensitivity is 99dB/W, mods: Crites crossovers and tweeters) in a medium-sized room with both vinyl and CD sources.  I am a "Rock Guy" and I like it loud and clean with all the bass that's on the recording.

From speaking with Bill Baker, I knew my amp would accept 6550s or KT88s in place of the EL34s that the 302b was originally designed around.  So I got a full set of ElectroHarmonix (12AX7/12AT7/KT-88) and found the sound I was craving.  Midrange is now almost as "glowing" as with EL34s, there's little-to-no "glare", and the bass quality and quantity is the best I've heard from this amp.  Put on Shelby Lynne's "Just A Little Lovin'" and that bass guitar just purrrrrs like a big kitty right there in the room with you.

The really great thing about the KT88 is that if you want that midrangey "glow" of the EL34 but don't want to swap tubes, all you gotta do is turn down the bias a bit.  If you want more slam and meat on the bone, turn the bias back up.  None of the other power tubes I've used changed their sound with increased/decreased bias settings like these EH KT88s.  After much listening, I've settled on between 500 and 550 mV (they're at 530 right now).  There are certainly better KT88s out there but ElectroHarmonix makes an affordable one that sounds so good I'm done shopping for others.

The only downside to running KT88s in this amp is that I now get a tiny amount of transformer buzz (using 8 ohm taps with the high-impedence Klipsches).  It's totally inaudible from the listening position, however, so I can ignore it.

I used Cary silicone o-ring tube dampers an a different tube amp a long time ago and they melted to the tubes.  I see Herbie's are a completely different design and might be worth a try.  The only thing holding me back is the simple fact that tubes are not grossly microphonic on my amp in my system (light taps on a tube with a pencil are almost inaudible through the speakers).  The amp is on Vibrapods in the middle of a well-isolated rack situated between and slightly behind the speakers (5'-6' separation on each side and my speakers are rather directional with deep nulls to their sides).  What kind of improvements do you think I could expect from Herbie's Audio tube dampers?

[Early B.]

Why do I get the feeling everybody on AC is selling something?  Heck the "industry" circles alone make up over half this site!

$2700 for a pair of bespoke monoblocks isn't what I (or anyone else) would call "mid-fi". 

You can get into a used Odyssey for $800. That's a bit more than the sales price for your 302B. So it would cost you very little to upgrade. 

Oh, and $2,700 is definitely mid-fi for brand new monoblocks. Brand new "high end" solid state monoblocks will cost you the sticker price of a decent automobile.   

[Tyson]

KrispyKirk,
Nice job working through various tube combos and keeping the NOS tubes safe as backups.  If/when you feel like you want to experiment some more, here's a few thoughts from my own tube rolling in my VTA ST70 tube amp.  For the 12ax7 and 12at7, try out Siemens NOS - they are not crazy expensive vs some other NOS options, and they have a great punchy sound.

For power tubes, I actually agree with you, the EH tubes are actually pretty good, and NOS power tubes are just too expensive.  One other tube you might want to try out is the Golden Lion KT66.  IME, the KT66 is the best tube Golden Lion makes and is one of the best new production tubes period, especially if you value a more visceral sound, but still with great tone.  Better than the KT77 or KT88 tubes I've heard, actually. 

The tube dampers aren't just for microphonic tubes - one thing they do to the sound is increase focus.  Some people really like what they do, others don't.  I'd start with a couple of the small dampers for the 12ax7s and 12au7s, if you like them there, then try out some of the bigger ones on the power tubes. 

[raindance]

Dual volume control can sound good, but I despise it as I am too OCD and can never seem to get the channels the same  A single blue velvet dual audio taper pot works and tracks fine. Evidently Jolida used the Alps volume pot from the factory. I know they did (a motorized one) in the JD1000BRC which I had.

The input selectors on all the Jolidas are complete junk. I have experimented with a relay input selector from ebay that works great and can use the old input selector switch to control the relays. I use one of the boards below as an input selector in my AMC CVT1030 preamp. The challenge with the Jolida amps is typically there is limited space to add such an item and I even toyed with adding a module on the back of my JD1000BRC to house the input selector relays and a small power transformer. Ultimately I never did it.

https://www.ebay.com/itm/Input-Selector-DIY-Kit-for-Audio-With-Relay-and-LED-/112295423934

There are plenty of other choices also.

[raindance]

PS: the biggest improvement you can make to any Jolida amp is removing the "subwoofer" output if it was so equipped. This comes straight off the volume pot wiper and ANY sub you connect will load the input stage down.

[Krispy Kirk]

No subwoofer outputs here (thankfully).  I've owned three different Jolida amps and none of them were "blessed" with them - it must be some new fad like wifey or blootoof.  In fact, I view sub outs on two channel gear with much disdain and derision.  Some audiophiles turn their noses up at tone controls, loudness (or "contour") adjustments, and other kinds of EQ on amplification gear.  Me?  I scoff at anyone who thinks a low- to mid-powered stereo Class AB push-pull tube amp needs an output for their big box full of air over in the corner of their listening room the sole purpose of which is to make various farting noises with greater fidelity and impact.

Really.  If you use a subwoofer, hurray for you!  But have you ever considered that using a sub in a two channel system merely reveals how inadequate your main speakers are?  I mean, if they were of a healthy full-range size, properly designed, and properly set up, you wouldn't need that big black fart-box in the corner of your listening room!  Subwoofer use rose precipitously in the early 90s.  I blame Dr. Bose and Gangsta Rap.  If you were there, you know what I mean.

Two places I can tolerate subwoofers: 1) in a vehicle (nothing helps out a mobile rig quite like a 12" in a sealed box on a dedicated 200w-400w amp crossed over at about 100Hz, and, no, I don't listen to Rap - it's just that a sub seems to overcome most "road noise" generated in a moving vehicle, increasing perceived signal-to-noise ratios and dynamic range...the very best car audio systems I've ever heard all had a subwoofer or two); 2) in a Home Theater (if your favorite movies have explosions, gun fights, car chases, space ships, etc - and almost all do these days - you absolutely need one or more subwoofers, otherwise you might as well not even bother.)

If I want a subwoofer output, I will buy an audio-video receiver.  But for every music-only two channel system I've owned, audition, or lusted after, there is a notable absence of fart-box in the corner of the room.  They draw too much attention to themselves and are nearly impossible to execute seemlessly.  Just buy bigger speakers and be done with it.

/rant off

 

[Early B.]

Really.  If you use a subwoofer, hurray for you!  But have you ever considered that using a sub in a two channel system merely reveals how inadequate your main speakers are?  I mean, if they were of a healthy full-range size, properly designed, and properly set up, you wouldn't need that big black fart-box in the corner of your listening room!  Subwoofer use rose precipitously in the early 90s.  I blame Dr. Bose and Gangsta Rap.  If you were there, you know what I mean.

The main reason separate subs are superior to full range speakers is placement. It's well known that proper placement of subs in the room can make a significant difference, but if the bass is tethered to the mids and highs, those options are very limited. In terms of placement, full range speakers are a compromise between soundstage, imaging and good bass. You're not likely to get all three of them precise, no matter how good your full range speakers are. Besides, separate subs often have separate amps, so you have more control to dial them in. Of course, full range speakers have their benefits -- less clutter, high wife acceptance factor, and plug & play. They're convenient, too, but they don't necessarily offer the best sound.

Oh, and there's lots of open baffle subwoofer options, so there's no need to put "that big black fart-box in the corner of your listening room."

[Steve]

The main reason separate subs are superior to full range speakers is placement. It's well known that proper placement of subs in the room can make a significant difference, but if the bass is tethered to the mids and highs, those options are very limited. In terms of placement, full range speakers are a compromise between soundstage, imaging and good bass. You're not likely to get all three of them precise, no matter how good your full range speakers are.

I have to disagree with the broad generalization, although one of the big reasons for compromised sound in speakers is no controls. I have been testing my two way full range speakers, with controls, and obtain superior sound vs others costing up to 28 grand, in my room.

I think another compromise over the years, the building of smaller type woofers to very low frequencies. I have yet to hear a subwoofer anywhere, that sounds right; always seems to be a compromise.

Small size seems to rule these days and after designing an older type large design, the sonic difference is quite apparent.
I will take my full range large size test speaker vs a separate sub any time, any day. (caveat: I am retired.)

I think the OPs question is dual controls vs balance/single volume control, so we should probably get back on topic.

cheers

steve