xlr-rca balanced to single ended adaptors - help needed

[recstar24]

Developing from the last thread I was on, a simpler and cheaper solution for my speaker rig to get some extra voltage gain I need would be to use xlr-rca adaptors from the balanced output. I understand I don't necessarily get the benefit of the dual differential output from the dacs and output stage of the meridian, therefore lose the common mode noise rejection, but technically, I still get the 2x voltage, correct? Impedance issues should not be a concern, as my moth integrated input impedance is 100kohm and my IC's are very low capacitance.

If that all makes sense and you guys are on board, what differentiates a well made adaptor and a poor one? They sure come in a variety of price points, that is for sure. What constitutes a well made adaptor, or are they all the same?

[n_maher]

Nope, you'd only get 1x (the normal) voltage output or half the balanced since the signal would be swinging referenced to ground rather than both the in phase and out of phase total swing.

And rather than use adapters I'd just have a set of balanced to RCA cables built. I can think of 3 or 4 folks around here who could do that for you for a reasonable sum of $$. I don't like adapters all that much when a single cable can be used efficiently.

Edited November 10, 2008 by n_maher

[Salt Peanuts]

Ditto on just having a XLR-RCA cable built. I had a pair built by Blue Jeans when my Cardas XLR-RCA adaptors didn't play nice with 840c.

[recstar24]

Nope, you'd only get 1x (the normal) voltage output or half the balanced since the signal would be swinging referenced to ground rather than both the in phase and out of phase total swing.

And rather than use adapters I'd just have a set of balanced to RCA cables built. I can think of 3 or 4 folks around here who could do that for you for a reasonable sum of $$. I don't like adapters all that much when a single cable can be used efficiently.

That solves it, its a moot point as I don't get the voltage gain benefit of the balanced. Active preamplification it is...unless I can get that balanced IC line receiver built.

[deepak]

That solves it, its a moot point as I don't get the voltage gain benefit of the balanced. Active preamplification it is...unless I can get that balanced IC line receiver built.

http://www.head-case.org/forums/speakers/4623-dht-preamps.html

Somebody here dew eet!

[JBLoudG20]

Ryan,

If you want cables, I have a set of 1 foot XLR male -> RCA Male 's laying around from an old amp I had. You can have them for the cost of shipping.

[n_maher]

You need the additional gain from the balanced outputs? If so they you'll want a proper active preamp, not some wunder chip sum of the balanced outputs deal (IMO). As a start I'd take a hard look at something like the Twisted Pair Ballsie which I think would suit your needs and be of good quality. But again, I might opt for a true preamp over something like that if I were you.

[recstar24]

You need the additional gain from the balanced outputs? If so they you'll want a proper active preamp, not some wunder chip sum of the balanced outputs deal (IMO). As a start I'd take a hard look at something like the Twisted Pair Ballsie which I think would suit your needs and be of good quality. But again, I might opt for a true preamp over something like that if I were you.

Thanks Nate - those are my thoughts as well. One idea is a used adcom gfp-750, its a nelson pass design that the circuit is basically identical to the aleph p that was released in the late 90's. Knowing pass it should sound great and be technically sound. Doesn't hurt to have a remote either.

[luvdunhill]

Thanks Nate - those are my thoughts as well. One idea is a used adcom gfp-750, its a nelson pass design that the circuit is basically identical to the aleph p that was released in the late 90's. Knowing pass it should sound great and be technically sound. Doesn't hurt to have a remote either.

There are some significant differences. The CCS is a different type (passive) and there are electrotylics in the gain circuit in the Adcom. Finally, the Adcom has very cheap DC coupling caps on both the input and the output. I'd call the GFP a "poor mans" Aleph P. There are a few other differences, but it's been a while. You're definitely not pulling a "Sherwood" here, but just figured I'd let you know that you're not quite on target

FWIW, the Nakamichi Nelson Pass implementations (CA7II and PA7II) are quite a bit better.

[aerius]

One option is using transformers to do the balanced to single-ended conversion, this keeps the full output voltage of the balanced outputs on the CD player and you have noise rejection all the way up to the transformer. Meaning if you stuck the tranformer right before in the inputs on the amp, you'd have almost all the benefits of a conventional balanced connection.

[luvdunhill]

One option is using transformers to do the balanced to single-ended conversion, this keeps the full output voltage of the balanced outputs on the CD player and you have noise rejection all the way up to the transformer. Meaning if you stuck the tranformer right before in the inputs on the amp, you'd have almost all the benefits of a conventional balanced connection.

... and maintains proper phase.

[recstar24]

There are some significant differences. The CCS is a different type (passive) and there are electrotylics in the gain circuit in the Adcom. Finally, the Adcom has very cheap DC coupling caps on both the input and the output. I'd call the GFP a "poor mans" Aleph P. There are a few other differences, but it's been a while. You're definitely not pulling a "Sherwood" here, but just figured I'd let you know that you're not quite on target

FWIW, the Nakamichi Nelson Pass implementations (CA7II and PA7II) are quite a bit better.

Actually, I was able to find that out after some searching. Thanks for the confirmation.

I am getting an aleph p1.0 clone commissioned from Tim Rawson, should be decent. The price is right, that is for sure.

Aerius,

I did think about that, and was probably near the top of simple, elegant solutions. I think I just won't bother anymore, and the active option will give me some flexibility for the future if I ever decide to expand or change the system. The aleph is fully balanced, and while I won't be taking full advantage of its performance in my current setup, with the balanced in from the meridian, and the unbalanced out from the aleph into the moth, I do think it will more than get the job done.

luvdunhill,

Can you clarify one thing for me on the aleph p for the unbalanced out? I believe it just takes the balanced signal and connects only the out+, leaving the out- unconnected, correct?

[luvdunhill]

Actually, I was able to find that out after some searching. Thanks for the confirmation.

Can you clarify one thing for me on the aleph p for the unbalanced out? I believe it just takes the balanced signal and connects only the out+, leaving the out- unconnected, correct?

actually, the Adcom is a perfect unit for modding, but I didn't get the impression that was the direction you wanted to persue.

edit: oh I was confused... anyways, yes your correct.

[luvdunhill]

I am getting an aleph p1.0 clone commissioned from Tim Rawson, should be decent. The price is right, that is for sure.

recstar24:

I don't know where your ethics lie, but you might be interesting in reading this thread:

diyAudio Forums - Someone's DIY Aleph J for Sale - Page 1

[recstar24]

recstar24:

I don't know where your ethics lie, but you might be interesting in reading this thread:

diyAudio Forums - Someone's DIY Aleph J for Sale - Page 1

Yeah, I read that too...to be honest, a part of me cares, a part of me does not...I guess that is where the issue of ethics lie.

Quick aside - I am currently working on my master's in educational administration and leadership. Basically, I will get the type 75 certification to become a principal or other administrative position if I so desire. A big part of my previous class was regarding ethical behavior, put into the connotation of an administrator making ethical decisions putting the community of students, parents, and school stakeholders first.

The clone is going to be about $300 - there is also an pass aleph p on audiogon currently for $1400, which I have a line on as well, and am awaiting for his previous committment to fall through. I will personally need to evaluate the value of that $1100 of savings, balancing the personal, selfish aspect or the idea of putting the community first.

[luvdunhill]

Yeah, I read that too...to be honest, a part of me cares, a part of me does not...I guess that is where the issue of ethics lie.

Quick aside - I am currently working on my master's in educational administration and leadership. Basically, I will get the type 75 certification to become a principal or other administrative position if I so desire. A big part of my previous class was regarding ethical behavior, put into the connotation of an administrator making ethical decisions putting the community of students, parents, and school stakeholders first.

The clone is going to be about $300 - there is also an pass aleph p on audiogon currently for $1400, which I have a line on as well, and am awaiting for his previous committment to fall through. I will personally need to evaluate the value of that $1100 of savings, balancing the personal, selfish aspect or the idea of putting the community first.

my opinion on the matter, which is irrelevant really, is that a nice compromise here is to commission a build from someone who doesn't build these on a full time basis. This way, I think you could achieve your monetary goals without supporting someone who very likely in the near future will get shut down like the others that have tried this in the past.

Also, another member here bought an amplifier from this guy, I can tell you 100% that the parts in fact cannot be to spec, as this builder upon cross-examination said it was, which calls into question his honesty in addition to his ethics.

[spritzer]

I would stay away from DIYFS units unless they take the original design and build on it, with better parts and execution. With this you have no guaranty of getting something even resembling the quality of the Pass stuff and with no after market value to boot.

[recstar24]

my opinion on the matter, which is irrelevant really, is that a nice compromise here is to commission a build from someone who doesn't build these on a full time basis. This way, I think you could achieve your monetary goals without supporting someone who very likely in the near future will get shut down like the others that have tried this in the past.

Also, another member here bought an amplifier from this guy, I can tell you 100% that the parts in fact cannot be to spec, as this builder upon cross-examination said it was, which calls into question his honesty in addition to his ethics.

Thank you for your valuable input, in this situation I think it does matter because I know you are familiar with the circuit and builder. I will shoot you a PM and we can talk further about the subject.

I would stay away from DIYFS units unless they take the original design and build on it, with better parts and execution. With this you have no guaranty of getting something even resembling the quality of the Pass stuff and with no after market value to boot.

Normally, I would agree. But reading the feedback about Tim Rawson and his particular builds, it appears that he is keeping it pretty close to the source on execution. Rawson's clones also seem to go within days from being posted up for sale as well.

[Sherwood]

You're definitely not pulling a "Sherwood" here, but just figured I'd let you know that you're not quite on target

Well that's ironic... I just bought the GFP-750 and found this thread. It appears I am yet again on the wrong end of this thing.

[luvdunhill]

Well that's ironic... I just bought the GFP-750 and found this thread. It appears I am yet again on the wrong end of this thing.

sweet! know anyone who's handy with a soldering iron, or looking to get into DIY?

[Sherwood]

I'm sure I could hunt someone down. I wouldn't call what I do with a soldering iron "handy", but I've some acquaintances whose degrees relied on their soldering skills, to some small measure. Surely one of them can be bought off with alcohol.

Anywhere I should look for mods, or is it really so simple as replacing the DC coupling caps on the input and output?

You also mention that they're in the gain stage -- does that mean that if the unit is in passive mode those caps are bypassed? I intend to use it in passive if I at all can.

[luvdunhill]

I'm sure I could hunt someone down. I wouldn't call what I do with a soldering iron "handy", but I've some acquaintances whose degrees relied on their soldering skills, to some small measure. Surely one of them can be bought off with alcohol.

Anywhere I should look for mods, or is it really so simple as replacing the DC coupling caps on the input and output?

You also mention that they're in the gain stage -- does that mean that if the unit is in passive mode those caps are bypassed? I intend to use it in passive if I at all can.

The input caps are still present when it's in passive mode. They are 10uF 'lytics bypassed with a 1uF polyester. Depending on your sources, you could eliminate these caps, or replace them with Black Gates. If the latter, you'll need to get a hold of some BG N 47uF/50V and BG N 10uF/50V, which are getting scarce. If you want to avoid BG, you'll have to fit a ton of films in there, which will be hard and not cheap.

[Sherwood]

Thanks for the help, luvdunhill, The BGs are in my shopping cart and the preamp comes in the mail today. I'm going to do my due diligence and put some hours of listening into it before I roll the caps, so I can appreciate the difference.

I'll open it up and post some pictures before I do the work. My DIY legacy is a handful of failed cmoys and a slightly manlier handful or working cables, so this represents a big step for me. Out of the kiddie pool, into the shark tank.

[Sherwood]

Also, the only non polar 10uf 50v cap I could find was the AC series, not the N series. The description of the AC series was high current for x-overs -- would that be detrimental in my application?

[Pars]

Look at Sonic Craft High-End DIY Audio Parts. They have the C series as well as the AC and Std. If you could use a K series (VK, etc.) that is what I would get, but it doesn't look like there is anything close to what you need. I assume you also checked Michael Percy Audio?