Jolida JD-9A Phono Preamp

madmax

I only know of the 9A, that is the one I had. Maybe you are reading something about different levels from a place that modifies them? www.jolida.com is their website.
madmax

analog97

Maybe you are reading something about different levels from a place that modifies them? www.jolida.com is their website.
madmax

Below are the specs I question, as stated on the website for Jolida.

Rated sensitivity at .25 mV – 95 dB

Again, I am saying that 95db CAN NOT be for gain. It could refer to "noise", i.e. SNR. However, they did not publish what this was referred to (i.e what signal, and whether it was A-weighted). I doubt this figure as well, i.e. a -95db SNR that is fairly referenced. That is why I challenged the stated figures and wrote to Jolida. I suspect marketing. Hey, it's 2008. Everyone uses "performance enhancers"...:D:D

madmax

I was refering to trietz3 comment about offering different stages.
madmax

analog97

I just got a response from Jolida. They tell me the 3 figures (70db, 85db and 95db) listed in the specifications are GAIN. So, i wrote back and asked my question be referred to a technical person and thanked them for the reply. My basic problem is this: If I use my low-output MC (0.3mv) and apply 95db gain, my calculation is that this yields >15 VOLTS output. Anybody know what I'm missing here??:):)

BaggedLancer

Sorry analog, im a dummy when it comes to this stuff....what is a more respectable number for volts output?

analog97

Take an easy example. A typical low-out MC puts out .5 mv. Every 20db of gain is a 10-fold amplification. So, .5 x 10 = 5mv. Then, that 5 mv requires another 2 rounds of 10-fold amplification, for a total of 60db. A typical MM-input for a phono pre-amp is about 40db. That means 5mv x 10= 50mv x 10 =500 mvolts (1/2 volt). That is a typical case for a low-output MC, generally wanting a total of 60db (usually 20 db coming from a step-up transformer and another 40db from the phono stage).

Moving magnet (MM) carts generally put out about 3-7mv (much higher output than MC'c). So, a typical MM cart needs about 40 db of gain from the phono pre-amp. Note here, that the Jolida MM specs quoted say 70db gain!! Again, something is wrong here. That's why I repeated the question to Jolida and asked for a "technical" person to review.

madmax

analog97 wrote: »

If I use my low-output MC (0.3mv) and apply 95db gain, my calculation is that this yields >15 VOLTS output. Anybody know what I'm missing here??:):)

Is it 15V or 1.5V?
madmax

analog97

.3mv x 20 db = 3mv
3mv x 20 db = 30mv
30mv x 20db= 300mv (that's an appropriate output to a pre-amp)
300mv x 20db= 3 Volts (that's after only 80db gain)

Another round of 20 db (for a total of 100db gain) takes it to 30 VOLTS!! Remember, Jolida claims 95db gain. That's why I'm estimating 15 Volts.

madmax

I hope they reply. 15V is certainly too high. Aren't really hot line drivers maybe 5V at the most? I will say again that the output is REALLY high on the Jolida if setup that way but certainly 15V wouldn't work at all.
madmax

analog97

I will say again that the output is REALLY high on the Jolida if setup that way but certainly 15V wouldn't work at all.

Mad One:

Do you recall what cartridge you used with the Jolida and what setting you used for the input? That could help us figure things out.

madmax

I used a Goldring 1042 and used one of the MM settings. I went through the tube stage for awhile and then bypassed for awhile. I think when I used the tube stage I lowered the gain value by switching to a different input. At the end before I sold it I used a Benz Ruby 3 cart at full gain. I remember it being louder than my CD setup was at the time.
madmax

m00npie

I just bought one of these and after reading this I’m starting to question my purchase. The item is in transit so there is no going back now since it was purchased used. Oh well, I'll give her a run anyway and see what happens.

madmax

m00npie wrote: »

I just bought one of these and after reading this I’m starting to question my purchase. The item is in transit so there is no going back now since it was purchased used. Oh well, I'll give her a run anyway and see what happens.

Its an awesome preamp. Only the validity of the gain spec on the website is in question.
madmax

analog97

I used a Goldring 1042 and used one of the MM settings. I went through the tube stage for awhile and then bypassed for awhile. I think when I used the tube stage I lowered the gain value by switching to a different input. At the end before I sold it I used a Benz Ruby 3 cart at full gain. I remember it being louder than my CD setup was at the time.
madmax

That is good information. I also used a 1042. It puts out about 6-7 mv, i.e. a lot!! I used mine with a 40db gain phono pre-amp. Yes, at this level it approaches that of a CD. BTW, at 40db gain, that's about 600-700mvolts. At 60db gain, that's 6-7 VOLTS!! Yet, the spec for the MM gain setting on the Jolida is 70db!!!! Again, we're pushing > 15-20 VOLTS!! :eek:

thehawkman

m00npie wrote: »

I just bought one of these and after reading this I’m starting to question my purchase. The item is in transit so there is no going back now since it was purchased used. Oh well, I'll give her a run anyway and see what happens.

Not to worry m00npie. Trust your ears. I think you'll be happy with your purchase. I love my JoLida phono stage and have become a real vinyl fan.

madmax

analog97 wrote: »

Again, we're pushing > 15-20 VOLTS!! :eek:

Maybe they need to attach one of those labels on the output that says "DANGER HIGH VOLTAGE".

analog97

So, have not yet gotten a response from a "technical" person at Jolida, so I wrote to a reputable dealer for Jolida. He agreed with me that the specs must be wrong and said he would follow this up with Jolida on Monday! Hard to get answers in 2008. Ever notice that it's getting more and more difficult?? :D

madmax

Yep.
madmax

analog97

I have communicated with Jolida several times trying to get a response. I also communicated with a Jolida dealer, Galen Carol, who said he would ask Jolida about my concern. Apparently, all e-mail goes to Michael Allen, President of Jolida. At this time, no satisfactory answer has been received about the gain figures for the Jolida pre-amp. My conclusion is that the published specs are wrong. I believe there is NO PHONO PRE-AMP THAT HAS 95db of GAIN!!!! Like most any potential customer, the lack of response bothers me. Each and every time I have asked POLK CS a question, I get an answer. Wow, POLK does it right, eh? :):):):):)

BaggedLancer

damn still nothing.....I always heard that Jolida had a decent CS too.

m00npie

Well, I finally received mine and as with most things, I hookup first, read the directions later:eek:

I put Brother in Arms on the TT and let it play. It sounded like I was standing outside a bar listening to the house band play 'So far Away'

I promptly shut it down and read the manual. I set up the pre-amp based on my Cartridge specs and played the TT again. Not bad, but not much better than the Parasound I was using. I think I have some other things going wrong that I need to start a thread on but as for now, I’ll just say inconclusive.

analog97

Finally starting to make progress. Jolida responded to me and asked me what formula I was using to calculate the voltage output. I never knew there was more than one!! :D:D:D

dB= 20log(V1/V2)

BaggedLancer

hah, sounds like you got a tech person on the other end now.

analog97

What's surprising to me is that the president of the company asked me what formula I was using to support my calculations. There is only one and it's been around for a long time. Very strange. I should point out, though that they have responded to me and have assured me they are taking my inquiry seriously. That's all I ask. For those who are interested, see the definitions and formula here: http://en.wikipedia.org/wiki/Decibel :D

madmax

m00npie wrote: »

It sounded like I was standing outside a bar listening to the house band play 'So far Away'

I heard that same type of sound when I was playing with phono interconnects once. Certainly the Jolida can sound much better than that. Keep at it.
madmax

mulveling

analog97 wrote: »

What's surprising to me is that the president of the company asked me what formula I was using to support my calculations. There is only one and it's been around for a long time. Very strange. I should point out, though that they have responded to me and have assured me they are taking my inquiry seriously. That's all I ask. For those who are interested, see the definitions and formula here: http://en.wikipedia.org/wiki/Decibel :D

Your calculations and assumptions are absolutely correct. Looks to me like Jolida really dropped the ball here, not a good sign.

More specifically calculating for a 0.3mv cart (just like my low-MC Benz Glider), 95dB of gain gives 0.0003*10^(95/20)=16.87 Volts, so your estimate of 15V was very close. For a bit of perspective, given a typical CD player outputs 2.2V, that means the hypothetical 95dB setting would be 20*log(10,16.87023/2.2)=17.69dB LOUDER than a CD player. That invokes almost SIXTY TIMES the audio power of the downstream components compared to a CD player. This would bring everything to its knees if you accidentally set the preamp volume too high (or switched from CD without adjusting). A completely unusable and dangerous setting that makes no sense - clearly this is not the case; they screwed up the calculations (assuming they even attempted any).

analog97

Your calculations and assumptions are absolutely correct. Looks to me like Jolida really dropped the ball here, not a good sign.

Thanks mulveling for the second opinion. I have no axe to grind with Jolida. I just questioned their specs as printed, knew they were wrong, checked the math and sent them a few letters, including their request for the formula I used to calculate the gain estimate. I now have visions of off-shore engineers and on-shore lawyers spending thousands of dollars in "billable-time" dealing with this. These costs will probably drive up the cost of their products! Now, that would be a real shame.......:(:(:(.......still no final response from Jolida......stay tuned, hopefully for a response taking "the high road"....:)

madmax

I doubt they go any further with it at jolida. Maybe they will change the number on the website or give a definition of stages or something. Part of it is the way the thing is setup possibly. If you wanted to not use the tube section you could input at the beginning of the chain and grab the output before going through the tube gain section. If you had the same cart but wanted to go through the tube section you could set it differently and do that. My guess is that is why this thing may have so much gain. I think it has 3 or 4 stages all together that you can switch in and out depending on switch settings and where you plug in the output. I'm wishing now I had mine back just so I could play with it and figure out this mystery.
madmax

analog97

I doubt they go any further with it at jolida. Maybe they will change the number on the website or give a definition of stages or something. /QUOTE]

Mad One:

You're probably correct. BUT, if they choose to go down this path, that will speak VOLUMES to me. The simple fact is that there is no phono pre-amp that puts out 95db gain. Yes, maybe they will change the specs on their website. Yes, maybe they will be lowered to something reasonable, like 38-44db for a typical MM cartridge and 58-70db for MC's. Something like that....fine..... BUT NOT 95db!!!!!!!!!!!!!!!!!!!!!!!!:eek::eek::eek::eek::eek::eek::eek::eek::eek:

madmax

Yeah, if no one will ever use it at 95 then why even print it?? It just looks bad.
madmax