...this is what others are saying about the 'Guanzo':
"Say Hello! to my new little friend" | Audiokarma Home Audio Stereo Discussion Forums
...and while I agree...I feel if properly tweaked and modified, the JP200 will perform admirably going by all the feedback of those that built it so far...
"Say Hello! to my new little friend" | Audiokarma Home Audio Stereo Discussion Forums
...and while I agree...I feel if properly tweaked and modified, the JP200 will perform admirably going by all the feedback of those that built it so far...
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...something that has been on my mind: I want to have 3 sets of outputs from the JP200 the first 2 going to one amp each; and the third to a powered subwoofer; so I can use them all at once, or isolate them by switching whichever one I wish to 'off'.
...what I am wondering is this. Will the Z-value be affected if I do this, and how?? Will it increase or decrease?? ... and what would be the overall effect - if any??
...what I am wondering is this. Will the Z-value be affected if I do this, and how?? Will it increase or decrease?? ... and what would be the overall effect - if any??
Peter Stein was concerned that I add his warnings to the information given to this forum when I communicated with him. Previously I asked him about adding a 'switch' to be able to switch from 1K to 15K to 68K and his response was:
"This is something I would not try as adding wiring to a very sensitive part of the circuitry is likely to cause issues ranging from instability to sound degradation. The location of components and tracks was very carefully considered and tested in thousands of hours testing - adding wires to these locations is a huge increase in track length and a big aerial to pick up stray signals (just being close to speaker leads of similar length will allow positive feedback at very high frequencies).
Without a lot of testing I would not attempt this myself. You can try it in your situation however I would at least use a good oscilloscope (100Mhz) to monitor things for a few weeks after you have added such wiring - damage to speakers and or amplifier is something that could happen very quickly."
...and
"- quality of wire has little to do with the aerial effects as mentioned earlier - a path for positive (or regenerative) feedback - and when we are dealing with a very wide band power amp the implications are that length of wire - inductance and capacitance, are changed. "
...and
"... we warn those if they later forget or sell the amplifier to someone else - it should be returned to factory standard.'
"This is something I would not try as adding wiring to a very sensitive part of the circuitry is likely to cause issues ranging from instability to sound degradation. The location of components and tracks was very carefully considered and tested in thousands of hours testing - adding wires to these locations is a huge increase in track length and a big aerial to pick up stray signals (just being close to speaker leads of similar length will allow positive feedback at very high frequencies).
Without a lot of testing I would not attempt this myself. You can try it in your situation however I would at least use a good oscilloscope (100Mhz) to monitor things for a few weeks after you have added such wiring - damage to speakers and or amplifier is something that could happen very quickly."
...and
"- quality of wire has little to do with the aerial effects as mentioned earlier - a path for positive (or regenerative) feedback - and when we are dealing with a very wide band power amp the implications are that length of wire - inductance and capacitance, are changed. "
...and
"... we warn those if they later forget or sell the amplifier to someone else - it should be returned to factory standard.'
Warning - just in case someone attempts to follow TigerScent instructions, I have the following suggestion - please don't - Not only does TigerScent not understand electronics, he fails to listen to and understand clear instructions and advice. When reading his post regarding ME 550 series 1 impedance change - even I was confused as to what he is talking about. My suggestion to all, is to have an experienced ME Service agent perform this modification.
I just followed Peter Steins (the designers) instructions --- and it worked. I don't assume to understand electronics which is why I have been asking a lot of questions. As far as instructions go, I did what was communicated to me to the degree it was.
I cannot see how anyone be able to make a remark that 'I fail to listen to or understand instructions' ?? and I follow things meticulously as explained. I went over them multiple times in any case.
I would say that this is an assumption based on not knowing how difficult it was to end up getting all the instructions to the point they made sense and worked - as he is busy and makes short replies.
I also responded to a request to convey what I did - which I did to save others the hassle of trying to find out how. It worked for me. If someone wants to see an ME service agent - good for them.
Others who have an ME550 have commented on this modification stating a child could do it and its just moving 2 resistors - and how it is simple to do - in other forums...
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Does anyone know what the issues are with valve pre-amps driving multiple loads?? Is it possible, ie: driving 2 amps and subwoofer from one valve preamp?? Is there degradation due to aerial effects and is there a way to circumvent this??
PS: when I ask a question, I am not giving advice...I am asking because I don't know...
PS: when I ask a question, I am not giving advice...I am asking because I don't know...
BTW - if someone is unsure or does not understand what is going on with the Z-value mod for the ME550 that I did; then go and see a ME service agent. Any attempts to follow what I did are solely at the persons own risk doing so.
I just posted what 'I did' due to a request, however it is not advice --- just what I understood and did - that worked.
What I did/posted on this mod can subsequently be viewed as some kind of 'historical record'.
Perhaps you could convey less confusing advice and instruction for such a simple modification so that all could understand ?? Since this is a DIY forum - just a thought.
Since you appear to assume to know so much about me and my character - and a great deal more than what I conveyed, being exactly what P.Stein said to me on all this (which was the most I could possibly do based on how he communicated things to me) - please - show some altruism and enlighten us all of the correct way to go about this - so that many are spared of needing to send their 550 to a ME technician for a 5 minute very simple mod (once its clear on how to do it)
To state in public that I 'fail to listen to and understand clear instructions and advice' is quite demeaning - to say the least. So, please - communicate - in a better manner giving 'clear instructions and advice' regarding what I did my utmost to communicate with the best of intentions to others about this Z-value mod --- so that they benefit and are safe with your communication on how to achieve this...again --- it IS a DIY forum...(and remember - it worked for me)
Just to lay this to rest; I am posting all relevant quotes of every word given to me by Peter Stein relating only on how to do this Z-value mod --- as he instructed me. This is all I had to go on, and you can compare this with what I wrote.
PS - "Please find attached layout of main PCB showing parts that affect Impedance." (this relates to the diagram I posted) -and-
"...read the owners manual carefully. It is necessary to reverse the red input plug on one channel." and "...the section that is important for you is headed "wiring for common earth systems"
My comment: (I have posted that part of the manual 'wiring for common earth systems as a pdf - It appeared he was talking about the RCA red input plug at first, but it became apparent he was speaking of the flat plug it is connected to that - which plugs into the circuit board)- I posted a photo of this plug.
PS -"...both red plugs need to be fitted to the board such that the red wire in both channels are connected to the board marked as "0" so that your clipped resistor set up will work as you wanted."
My comment: (these are the flat plugs I mentioned, that plug into the circuit board and extend to the RCA inputs externally, being Red and Black, Black for left, Red for right - in addition, after looking inside with a magnifier, I discovered the '0' he was referring to was printed on the circuit board, and the markings were '180, E, 0'. On the flat plugs there is a red wire which is one of the 3 wires attached to the plug. The red wire is one of them on one end of the plug, and it needs to be plugged in so that it is directly plugged into the pin marked '0'. )
PS -"...you do need to make both sides the same (that means removing resistors in the left and right channel) otherwise you will have input z on left as being 68k and right side 1k - would not worry a solid state preamp like an ME but can't imagine how poor the result would be with a cheap preamp.
As both boards are identical (otherwise it would not be a stereo amplifier) there is only one diagram. What could be confusing you is that one board is rotated around 180 degrees - so the things on the back side of amplifier on one channel are now reversed and are facing the front of the amplifier.
To make things a little more understandable and convenient - you could rotate the diagram (easiest) or if the wording orientation on the diagram needs to be upright, you could rotate the amplifier (front to back) by 180 degrees. You will then find that both boards are identical."
...so you can compare this to what I wrote after going over this a few times...now 'listening to and following instructions' as 'ozfossil' states - is now up to the reader - and to 'ozfossil' himself ...as these are P.Steins exact words only relating to making this change. All other correspondence which I did not include relates to other issues, some of which I posted previously as 'warnings' pertaining to other additional questions I had relayed to him.
PS - "Please find attached layout of main PCB showing parts that affect Impedance." (this relates to the diagram I posted) -and-
"...read the owners manual carefully. It is necessary to reverse the red input plug on one channel." and "...the section that is important for you is headed "wiring for common earth systems"
My comment: (I have posted that part of the manual 'wiring for common earth systems as a pdf - It appeared he was talking about the RCA red input plug at first, but it became apparent he was speaking of the flat plug it is connected to that - which plugs into the circuit board)- I posted a photo of this plug.
PS -"...both red plugs need to be fitted to the board such that the red wire in both channels are connected to the board marked as "0" so that your clipped resistor set up will work as you wanted."
My comment: (these are the flat plugs I mentioned, that plug into the circuit board and extend to the RCA inputs externally, being Red and Black, Black for left, Red for right - in addition, after looking inside with a magnifier, I discovered the '0' he was referring to was printed on the circuit board, and the markings were '180, E, 0'. On the flat plugs there is a red wire which is one of the 3 wires attached to the plug. The red wire is one of them on one end of the plug, and it needs to be plugged in so that it is directly plugged into the pin marked '0'. )
PS -"...you do need to make both sides the same (that means removing resistors in the left and right channel) otherwise you will have input z on left as being 68k and right side 1k - would not worry a solid state preamp like an ME but can't imagine how poor the result would be with a cheap preamp.
As both boards are identical (otherwise it would not be a stereo amplifier) there is only one diagram. What could be confusing you is that one board is rotated around 180 degrees - so the things on the back side of amplifier on one channel are now reversed and are facing the front of the amplifier.
To make things a little more understandable and convenient - you could rotate the diagram (easiest) or if the wording orientation on the diagram needs to be upright, you could rotate the amplifier (front to back) by 180 degrees. You will then find that both boards are identical."
...so you can compare this to what I wrote after going over this a few times...now 'listening to and following instructions' as 'ozfossil' states - is now up to the reader - and to 'ozfossil' himself ...as these are P.Steins exact words only relating to making this change. All other correspondence which I did not include relates to other issues, some of which I posted previously as 'warnings' pertaining to other additional questions I had relayed to him.
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...all the above instructions quoted by P.Stein on how to do this Z-value mod spanned over 5 emails over a period of time - from 4.Jan to 21.Jan 2018, which I cut and pasted the relevant parts-sentences from each short email in an easy and logical sequence in the above post...(and I also conveyed this same information previously in my post on how to do this based on what he told me (above) and on what I did, which was exactly the same - which is why it worked.)
I emailed him a number of times asking for more clarity and instructions in each email so that things become clearer - as only one channel was working - which is when the comment about turning the diagram 180 degrees came about; in order to do the same with regards to snipping the resistors on the other side, as on first glance each board looked different, and I wanted to be certain --- so that after all that time, it finally worked - however once properly understood - it is an easy ~ 5 minute procedure with the cover off...I found.
I emailed him a number of times asking for more clarity and instructions in each email so that things become clearer - as only one channel was working - which is when the comment about turning the diagram 180 degrees came about; in order to do the same with regards to snipping the resistors on the other side, as on first glance each board looked different, and I wanted to be certain --- so that after all that time, it finally worked - however once properly understood - it is an easy ~ 5 minute procedure with the cover off...I found.
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It is interesting that 'ozfossil' has only made this one and only post since 2011 - his join date.
Could this be someone we already know with another nickname - who has been unhelpful in this thread for a very long time - and who is wishing to appear as someone else??
...hmmm, I wonder...
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Hi TS,
He obviously doesn't want to participate in the threads and is more comfortable just reading. That's fine. We have thousands of people who prefer to just read. They are called lurkers, but that by no means implies anything negative about them.
For some reason he felt the need to post a warning, but without any other comments or references, it is difficult to take it that seriously. Only you and Peter know what was actually said, and we'll leave it at that.
Do not post any more content copies from personal PM's or emails without the consent of the other party please. I'll allow this as it is a condensed listing of instructions only.
-Chris
He obviously doesn't want to participate in the threads and is more comfortable just reading. That's fine. We have thousands of people who prefer to just read. They are called lurkers, but that by no means implies anything negative about them.
For some reason he felt the need to post a warning, but without any other comments or references, it is difficult to take it that seriously. Only you and Peter know what was actually said, and we'll leave it at that.
Do not post any more content copies from personal PM's or emails without the consent of the other party please. I'll allow this as it is a condensed listing of instructions only.
-Chris
...I must say, the modification to convert the ME550 to a input Z-value of 68K was very easy and very successful --- regardless of some naysaying and mindless paranoia-inducing remarks. It has saved me a lot of time and mucking around. (Why this was not suggested to me by those in the 'know' about the ME550 is mindboggling!!) - however...never-the-less, now its clear to anyone who comes across the same issue - of what is possible with just a pair of sharp wire snips; via a list of instructions as P.Stein communicated them to me; of how simple this mod. is --- however all attempts to duplicate my results are at the persons own risk.
It was difficult to decipher how to do this in the beginning since I only got short part-answers in each email, but putting the relevant sentences extracted from emails pertaining to the steps I needed to take, starts making some sense after going through them all very carefully a few times and reading the manual pages (which I posted). I also had to make a phone call to get further clarification.
On another note; I was told however, that its dangerous to connect 2 amps to a valve pre-amp output...but it was not explained why in any understandable manner - does anyone know?? or if this is so, how to circumvent this so that it is possible to connect 2 amps to the same valve pre-amp output??
It was difficult to decipher how to do this in the beginning since I only got short part-answers in each email, but putting the relevant sentences extracted from emails pertaining to the steps I needed to take, starts making some sense after going through them all very carefully a few times and reading the manual pages (which I posted). I also had to make a phone call to get further clarification.
On another note; I was told however, that its dangerous to connect 2 amps to a valve pre-amp output...but it was not explained why in any understandable manner - does anyone know?? or if this is so, how to circumvent this so that it is possible to connect 2 amps to the same valve pre-amp output??
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...well, P.Stein simply told me that all I had to do was turn his diagram with his handnotes (posted) 180 degrees and it would correspond to the other side. Its like a mirror --- at it works...he was quite confident in saying that, so...it worked very nicely...That was his response when I informed him I found only one channel working nicely and the other channel sounded muffled. As soon as I did what he said, the whole thing came alive.
...incidently however, it was interesting comparing the volume and dynamism from the left 68K channel being modded, and the right one being left as it was at 1K ... converting to 68K actually increased the dynamic output and volume quite considerably - I daresay this amp now could possibly be more than 80W RMS per channel, in fact it seems to have the same or similar volume output level leaving the preamp set at the same volume level; compared to the 200W RMS per channel Rotel 990BX I was comparing it with..., to the ears anyway...
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...the 'mysterious comments' made by the alleged 'ozfossil' appear (to me) to be referring to Z.B's 'instructions' (an ME technician) to simply give up and get a ME preamp (from him)... (ie: not following 'instructions' and seeing a 'ME technician' instead)..., and because I keep asking ?? - of course I know little about electronic circuitry and design..., otherwise I would not ask...
...in addition, its also something someone could do - using an old nick - to appear anonymous --- just a thought LOL
...ahhh, the world is fully of seeming 'mysteries'... we can only nod and smile
Apologies for delay, was in the 'sin bin' for speaking my mind. I agree with your assessment, although increasing the gap will impact on primary inductance, and I do prefer low noise tubes like 6922, available as twin triodes with shielded sections and the Gm is not so crazy, or as to make matching of single high Gm triodes a requirement, careful layout still required and some prevention to scotch oscillations etc. but the slightly higher Rp will IME help damp ringing. 5687 single section run low 4mA Ip 150V.. good enough and for a bright burner will have it last a bit longer, those in Japan use it as such and for good reason. All single stage, low output impedance, run rings around previously mentioned in this thread (in my experience, and as such a formulated opinion).
Ex Safer - have worked with a few, and in general took a liking to them. As for myself.. just a clumsily spelled moniker based on the SA Cricketer.
Always interesting to see some simplifying things with multiple additions. Not my bag, but then again, its not my bag.
Best to all.
Hanze.
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What I did/posted on this mod can subsequently be viewed as some kind of 'historical record'.
Yes it can...
just so we know what sort of record is, that amp works better with a low input impedance. Your pre can't tolerate it. Your pre can only tolerate input impedances around 2 orders of magnitude higher.
I await your discovery that a solid, low output impedance, valve design that allows you to return it to low input impedance configuration sounds better.
cheers,
Douglas
Having being made aware that the apparently profound information contained above, which forms the so called basis of 'setting a record for the historians', the consensus of considered opinions is that this has succumb to its inevitable laborious and fruitless end, as a result of its excruciating meandering waywardness, and deviation from the OP questions, and therefore should be closed.
Respectfully.
Respectfully.
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