Hi Zaphod Beeblebrox,
Right on! I'm very happy you still have yours. If you were closer I would try and buy it from you. The voltages were adjustable back then.
The rebuild will consume a couple days. You're going to pull and clean the heat sinks as part of this. What you will end up with is one heck of a nice amplifier.
PM me when you're ready.
-Chris
Right on! I'm very happy you still have yours. If you were closer I would try and buy it from you. The voltages were adjustable back then.
The rebuild will consume a couple days. You're going to pull and clean the heat sinks as part of this. What you will end up with is one heck of a nice amplifier.
PM me when you're ready.
-Chris
Will do. Mine will likely end up in the US, anyway, as prices are pretty good for that model. Mine still has the original packing box (a bit shabby though) and instruction manual. Front cover is still there of course. Still has the original meter lamps (working)!
I think the shipping costs from Oz will be extreme. That might price your amp out of the competition. A friend of mine has one in process for $2,400 US, so that is an actual sold price as opposed to what people are asking for them.
-Chris
-Chris
How is it even possible to answer this question. It all depends on your personal preferences and is (in my opinion) almost impossible to answer. The technical properties you list is met by a lot of tube preamps, my suggestion is to, if possible, try several preamps and let your ears decide witch one to go for.
There is no definitive answer to the question you asked, it all depends on what you prefer.
There is no definitive answer to the question you asked, it all depends on what you prefer.
I did post the schematic for the JP200 a few times...that is the preamp I will be using, and I need to attach some kind of buffer, most likely opt transformer based. The Z-output of the JP300 is ~3K
TS, IMO you'd be better off with a line amp that does not have so many stages. That and 12AX7 arranged like you showed have issues you'll discover once you get your hands on something simpler.
cheers,
Douglas
cheers,
Douglas
I have decided on getting this one going - I have also most of the parts...specific to this preamp...
That's a very good decision. Enjoy the rebuild. A matching transformer may give you the drive the amp needs.
-Chris
-Chris
Thanks...however, looking at the schematic, how would you apply opt transformers to reduce the Z-value, which ones would you use to get no sonic degradation with maximum frequency range/response...and how/where would you connect them up to the schematic...
I had an ME 850 back some years ago now, it was a very good amplifier - for what it was. I'm not sure the input impedance of that particular unit but 10k or 47k seems more reasonable.
Given the choice, if I were to drive a 1k load with a tube stage and did not need much gain, I'd avoid cathode follower, and go with low Rp triode as standard grounded cathode plate loaded stage into a step-down transformer. The build would then be based on the best transformer (and ratio) on a cost basis, as there are many <2k Rp tubes with decent current drive and medium to high mu. Of course not all of them are strictly triodes (in their native state).
I think the other guy said it best when he suggested you need to try and find what works best for you.. but I would agree, having lived some years with ME 850, a tube based front end can be a very good thing - to the point where... well, let that be your journey and not a recant of mine.
Enjoy!.
Hanze.
Given the choice, if I were to drive a 1k load with a tube stage and did not need much gain, I'd avoid cathode follower, and go with low Rp triode as standard grounded cathode plate loaded stage into a step-down transformer. The build would then be based on the best transformer (and ratio) on a cost basis, as there are many <2k Rp tubes with decent current drive and medium to high mu. Of course not all of them are strictly triodes (in their native state).
I think the other guy said it best when he suggested you need to try and find what works best for you.. but I would agree, having lived some years with ME 850, a tube based front end can be a very good thing - to the point where... well, let that be your journey and not a recant of mine.
Enjoy!.
Hanze.
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Best value for money in my book would be 5687 (or use JJ ECC99) into a Lundahl Transformer, model LL1660; a very versatile unit and user configurable transformer. I would suggest 4.5:1 gapped for 10mA, run the tube (one dual triode with one section per channel) 150V plate and 10mA, just as a starting point.
The same transformer could be used with 6922 - it doesn't lock you in to one design, gives freedom to experiment and they also have very good re-sale value.
As you lower the current through the tube you will find the sound which you prefer, but at least the inductance is there and the capacitance is low (enough). In other words, low and high frequency response will be more than adequate.
Voltage gain ~4, output impedance <100 ohms.
Your source might output 2vRMS, but that is at 0dBFS.. you might find that some voltage gain will come in handy.
Cheers.
The same transformer could be used with 6922 - it doesn't lock you in to one design, gives freedom to experiment and they also have very good re-sale value.
As you lower the current through the tube you will find the sound which you prefer, but at least the inductance is there and the capacitance is low (enough). In other words, low and high frequency response will be more than adequate.
Voltage gain ~4, output impedance <100 ohms.
Your source might output 2vRMS, but that is at 0dBFS.. you might find that some voltage gain will come in handy.
Cheers.
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Hi TigerScent,
Everything has a cost. The better the transformer is, the less quality is lost. You could also have a look at the various tube based output buffers as well.
-Chris
Everything has a cost. The better the transformer is, the less quality is lost. You could also have a look at the various tube based output buffers as well.
-Chris
Thanks for the info. I am just looking at reducing the Z-value of the JP200 from ~3Kohm to <10ohm...perhaps I can just use a couple of good audio transformers with that ratio...
...actually I have a couple of Tannoy ceiling speakers that have transformers in them quite heavy - which I don't need - I wonder what the ratio would be and whether I could somehow use them...hmmm??
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Those are "70 V" line to speaker transformers and will not be of high enough quality for your purpose.
Have a look at Hammond and Jensen and the others.
-Chris
Have a look at Hammond and Jensen and the others.
-Chris
Me thinks u will be paying top dollar,,,,I would shop around and refurb yourself as u have the knowhow...
Hi TS,
I had no intention of buying anything that didn't need work. I can't even afford the broken 500's.
-Chris
I had no intention of buying anything that didn't need work. I can't even afford the broken 500's.
-Chris
Hi Hanze,
Yes I do, I have the circuit board and most of the parts for it ... just waiting to see if I might need to do some mods for it to suit my requirements more...
Take note, with regards to the link (which I read before) that those who built the JP200 are pleased with it, yet those who criticise it - have not, nor have they heard it --- speaks volumes...
However a number have made mods, ie: used a couple of 12AT7's and some different res. values...etc...overall the consensus with all that have made one has been 100% positive.
At the moment have been listening to Rotel 990BX with cheap chinese Guanzo (Sainsmart has used it also) valve preamp with an amazing sound result...for the interim...
...however need to get the ME550 up and running properly - which has been dragging on for a few years with zero assistance whatsoever from those who are in the know about this amp and who would know how to get things going..., instead being insistent on marketing a finished product...
...so a solution - that works with no sonic degradation - would be gr8 right now...
I think, as a number have suggested - the use of output transformers would be easiest and most ideal to the task...I find the valve front-end - and even used as a buffer in SS pre to main amp - gives the most desirable natural sounding result with transparent soundstage etc..., yet with the dynamics of the SS main amp ... quite addictive...
Cheers...
Yes I do, I have the circuit board and most of the parts for it ... just waiting to see if I might need to do some mods for it to suit my requirements more...
Take note, with regards to the link (which I read before) that those who built the JP200 are pleased with it, yet those who criticise it - have not, nor have they heard it --- speaks volumes...
However a number have made mods, ie: used a couple of 12AT7's and some different res. values...etc...overall the consensus with all that have made one has been 100% positive.
At the moment have been listening to Rotel 990BX with cheap chinese Guanzo (Sainsmart has used it also) valve preamp with an amazing sound result...for the interim...
...however need to get the ME550 up and running properly - which has been dragging on for a few years with zero assistance whatsoever from those who are in the know about this amp and who would know how to get things going..., instead being insistent on marketing a finished product...
...so a solution - that works with no sonic degradation - would be gr8 right now...
I think, as a number have suggested - the use of output transformers would be easiest and most ideal to the task...I find the valve front-end - and even used as a buffer in SS pre to main amp - gives the most desirable natural sounding result with transparent soundstage etc..., yet with the dynamics of the SS main amp ... quite addictive...
Cheers...
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