I’m VERY interested in a simple balanced/XLR conversion. Seen a few choices on eBay, one complete uses/comes w/a wall wart ($35) or a bare PCB and parts list $10 - but I’m keeping my options open from those smarter than I.
Cardas Adapters
I am aware of these options, it is a simple and elegant solution (several versions are made) and while pricey, it is built to a level of quality which supports the cost.
I have spoken to both Ralph Karsten of Atma-Sphere and Josh Meredith at Cardas about these options... Ralph recommended a resister across the unused pin, and Josh asked to confirm which pin that was. I asked Ralph about my concern if it would asymmetrically load the cascode follower output stage... he said that it would in a minor way, but that it would not be a problem.
XLR to RCA male (allows for a variety of cable use, across different amps)
Cardas Connector MXLR to MRCA Adaptor
XLR to RCA Female (solves the preamp feeding SE amps only)
Cardas Connector FXLR to FRCA Adaptor
~ decisions ~ decisions ~ several years has past, I am still undecided.
I have considered installing Jensen transformer(s) in the MP1 pre-amp (electrically, the most sound solution) but then I cannot take advantage of the primo balanced cable...
I really want to hear the Atma-Sphere pre-amp drive (various) "Hafler" amp(s) but want to optimally load it. (it to be happy)
I am aware of these options, it is a simple and elegant solution (several versions are made) and while pricey, it is built to a level of quality which supports the cost.
I have spoken to both Ralph Karsten of Atma-Sphere and Josh Meredith at Cardas about these options... Ralph recommended a resister across the unused pin, and Josh asked to confirm which pin that was. I asked Ralph about my concern if it would asymmetrically load the cascode follower output stage... he said that it would in a minor way, but that it would not be a problem.
XLR to RCA male (allows for a variety of cable use, across different amps)
Cardas Connector MXLR to MRCA Adaptor
XLR to RCA Female (solves the preamp feeding SE amps only)
Cardas Connector FXLR to FRCA Adaptor
~ decisions ~ decisions ~ several years has past, I am still undecided.
I have considered installing Jensen transformer(s) in the MP1 pre-amp (electrically, the most sound solution) but then I cannot take advantage of the primo balanced cable...
I really want to hear the Atma-Sphere pre-amp drive (various) "Hafler" amp(s) but want to optimally load it. (it to be happy)
Attachments
Last edited:
Correction to "auto correct"
The MP1 pre-amp is fully balanced from phono input to pre out. There is a CATHODE FOLLOWER, as the final output, that I am concerned about uniformly loading both plate sections [when driving SE] my "Hafler" based amps.
My intent would be, adding the Jensen transformers would take the balanced signal, convert and terminate to an (added pair) of MP1 chassis mounted RCA jacks, in addition to the XLR pre-amp outputs.
All A/S amps have balanced and SE inputs (I can and do use either). However, the pre-amp [to be clear] has balanced and SE line inputs and outputs... but the pre-amp output is only balanced. Ralph can and does offer an added pair of RCA outputs (as an option) which mine does not have. *I am concerned (which admittedly, is OCD'esk) about uniformly loading both plate sections of the cathode follower... with one plate section as + and the other as - signal.
The positive and negative opposites [would not be summed] the negative simply would not be used or seen by the SE amplifiers input stages.
The MP1 pre-amp is fully balanced from phono input to pre out. There is a CATHODE FOLLOWER, as the final output, that I am concerned about uniformly loading both plate sections [when driving SE] my "Hafler" based amps.
My intent would be, adding the Jensen transformers would take the balanced signal, convert and terminate to an (added pair) of MP1 chassis mounted RCA jacks, in addition to the XLR pre-amp outputs.
All A/S amps have balanced and SE inputs (I can and do use either). However, the pre-amp [to be clear] has balanced and SE line inputs and outputs... but the pre-amp output is only balanced. Ralph can and does offer an added pair of RCA outputs (as an option) which mine does not have. *I am concerned (which admittedly, is OCD'esk) about uniformly loading both plate sections of the cathode follower... with one plate section as + and the other as - signal.
The positive and negative opposites [would not be summed] the negative simply would not be used or seen by the SE amplifiers input stages.
Last edited:
Some of you may want to know that using an XLR to RCA adapter provides no advantages of a balanced cable. In order to reap the benefits of a balanced interconnect, you must have a true balanced driver and receiver circuit.
These is one trick that does provide some benefit. That is connecting an unbalanced source to a balanced input. Instead of tying the shield to ground at the balanced destination, you connect the shield to the minus input and NOT tie the shield to ground at the receiving end. This does help reduce noise pickup from the cable. This was done extensively with analog broadcast video equipment because video cables are unbalanced. The video input stages were true differential amplifiers with the BNC connector shell connected to the diff amp minus side and not grounded. The main benefit was due to the USA 60hz AC line and the 59.94hz vertical rate modified for color TV in the 1950s and AC line ground loops causing rolling hum bars in the picture.
There are also some caveats mixing balanced and unbalanced depending if either device has a transformer or electronic balanced circuit. This relates to what you do with the minus side. Do you tie it to ground or let it float? Those here with electronics backgrounds will see the issue. You can't have an open transformer winding. And you really don't want to short out the minus side driver on a balanced electronic interface circuit.
Then there is the level problem. Consumer gear signal levels are loosely defined. Anywhere from -10db to 0db. Modern pro gear is now standardized at +4db. Vintage gear may even be +8db. You can see the problem here.
In a small home HiFi setup there is really no benefit to balanced I/O. The cable lengths are not significant. And for the purists, a balanced I/O circuit has more parts. And good transformers are expensive - starting at $100. And they too are not 100% transparent at any price.
Now I do run all balanced audio in my HT system. But I have four racks of AV gear including many computers. So I have a lot bigger risk of noise pickup. I also use pro DACs which are balanced so it made sense to put balanced inputs on my amps. But again for most people balanced I/O is unnecessary and not desirable.
These is one trick that does provide some benefit. That is connecting an unbalanced source to a balanced input. Instead of tying the shield to ground at the balanced destination, you connect the shield to the minus input and NOT tie the shield to ground at the receiving end. This does help reduce noise pickup from the cable. This was done extensively with analog broadcast video equipment because video cables are unbalanced. The video input stages were true differential amplifiers with the BNC connector shell connected to the diff amp minus side and not grounded. The main benefit was due to the USA 60hz AC line and the 59.94hz vertical rate modified for color TV in the 1950s and AC line ground loops causing rolling hum bars in the picture.
There are also some caveats mixing balanced and unbalanced depending if either device has a transformer or electronic balanced circuit. This relates to what you do with the minus side. Do you tie it to ground or let it float? Those here with electronics backgrounds will see the issue. You can't have an open transformer winding. And you really don't want to short out the minus side driver on a balanced electronic interface circuit.
Then there is the level problem. Consumer gear signal levels are loosely defined. Anywhere from -10db to 0db. Modern pro gear is now standardized at +4db. Vintage gear may even be +8db. You can see the problem here.
In a small home HiFi setup there is really no benefit to balanced I/O. The cable lengths are not significant. And for the purists, a balanced I/O circuit has more parts. And good transformers are expensive - starting at $100. And they too are not 100% transparent at any price.
Now I do run all balanced audio in my HT system. But I have four racks of AV gear including many computers. So I have a lot bigger risk of noise pickup. I also use pro DACs which are balanced so it made sense to put balanced inputs on my amps. But again for most people balanced I/O is unnecessary and not desirable.
Last edited:
My intended use (possible misunderstandings)
Great points and contributions to the topic. I AGREE implicitly, thank you for clearly spelling it out.
To be clear... my principle intent(s) are.
~ To be able to use my UBER FANTASTIC pre-amp with home made SE amps. I would like to experience the MP1 driving my amps...
~ To use my high(er) end Kimber, and Audioquest, Cardas [short runs of] balanced cables and the longer runs of 'pro' balanced cable for (strictly) subwoofer use.
**I am not seeking CMMR or gain uniformity prospects... particular to a balanced world. I live in the country with limited RFI or EMI pollution... LOLS, I barely get cell phone, FM or TV signals in this valley, and no WiFi, 5G or 6G around me.
To paraphrase, though you may not have said exactly like this (there are compromises) mixing SE and balanced components... If I have my preferences, I would only use (design and build) balanced gear and cables.
**I was not trying to infer ANY ADVANTAGES of a complicated series of options to connecting different gear and cables...
Great points and contributions to the topic. I AGREE implicitly, thank you for clearly spelling it out.
To be clear... my principle intent(s) are.
~ To be able to use my UBER FANTASTIC pre-amp with home made SE amps. I would like to experience the MP1 driving my amps...
~ To use my high(er) end Kimber, and Audioquest, Cardas [short runs of] balanced cables and the longer runs of 'pro' balanced cable for (strictly) subwoofer use.
**I am not seeking CMMR or gain uniformity prospects... particular to a balanced world. I live in the country with limited RFI or EMI pollution... LOLS, I barely get cell phone, FM or TV signals in this valley, and no WiFi, 5G or 6G around me.
To paraphrase, though you may not have said exactly like this (there are compromises) mixing SE and balanced components... If I have my preferences, I would only use (design and build) balanced gear and cables.
**I was not trying to infer ANY ADVANTAGES of a complicated series of options to connecting different gear and cables...
Last edited:
If any one is interested I built and measured the THD on the DH220C front end with the mods for use at 90Vdc rails:
https://www.diyaudio.com/forums/solid-state/362313-hafler-dh-500-p500-mods-3.html#post6578315
-Dan
https://www.diyaudio.com/forums/solid-state/362313-hafler-dh-500-p500-mods-3.html#post6578315
-Dan
you need the 56/176 for 90 VDC (maybe the 2SJ55 / 2SK175 will survive, maybe not - no guarantee. But these are hard to find, although I got some really nicely matched sets last year from Swedish DIY member
2SJ48 / 2SK133 7A 120 VDC
2SJ49 / 2SK134 7A 140 VDC
2SJ50 / 2SK135 7A 160 VDC
2SJ55 / 2SK175 8A 180 VDC
2SJ56 / 2SK176 8A 200 VDC
DIVIDE the voltage rating by 2 when used in a dual rail supply to allow for output stage to be at full voltage of the opposite rail.
2SJ48 / 2SK133 7A 120 VDC
2SJ49 / 2SK134 7A 140 VDC
2SJ50 / 2SK135 7A 160 VDC
2SJ55 / 2SK175 8A 180 VDC
2SJ56 / 2SK176 8A 200 VDC
DIVIDE the voltage rating by 2 when used in a dual rail supply to allow for output stage to be at full voltage of the opposite rail.
Last edited:
!Hi Dan, these look like quite good distortion numbers, and I salute you for taking the measurements up to 20 KHz. To me, stupendous 1 kHz THD numbers are not as meaningful (but still worthwhile).
I was confused by the the step 2 and step 3 curves. What is the difference?
What instrumentation did you use to make the distortion measurements?
Best regards,
Bob
You make a very good point about the ability of the 2SJ50 and 2SK135 to safely operate with +/- 90-V rails. I don't have a DH-500 and don't recall which output devices it came with. Was it the '50 and '135?
In order to test the DH-220C circuit in a DH-500 arrangement, I used a P230 (that has 3 output pairs) with a high supply voltage in the range of +/- 90 V or maybe a little less. I did this test without even thinking about the breakdown voltage of the '49 and '134 devices used in it. My bad. Lucky it did not blow up. Anyway, it ended up performing well as long as I did not run it at high power levels long enough to seriously heat up the P230 heat sinks.
The danger of breakdown in the DH-500 situation would be greatest when running at maximum output voltage into no load, since the power supply does sag substantially under load. Also, the gate-source voltage drop in the output transistors increases substantially when delivering high current to the load.
If Hafler supplied the DH-500 with '50 and '135 devices and thought that was OK for a reliable commercial product, then it is probably OK.
Cheers,
Bob
The DH 500 i’ve seen had 176/56 devices and those are what is specified in the Hafler DH 500 and 600 manuals parts list.
The Perreaux 3150 had 135/50 devices with 96 VDC rails that sagged with load. It made 35 years on the original devices so must be OK. Were they selected or a special run? Theres no source degeneration so they were at least matched sets.
The Perreaux 3150 had 135/50 devices with 96 VDC rails that sagged with load. It made 35 years on the original devices so must be OK. Were they selected or a special run? Theres no source degeneration so they were at least matched sets.
Last edited:
The Exicon TO3 laterals are stated to effectively replace the Hafler Hitachis. The single die ones are 8A, 200VDC devices.
They work great in my DH-220C! I got the ‘matched’ ones.
ECF10N20 Metal Lateral MOSFET | Profusion
They even offer double-die ones for 16A, 200VDC.
ECF20N20 Metal Lateral MOSFET | Profusion
They work great in my DH-220C! I got the ‘matched’ ones.
ECF10N20 Metal Lateral MOSFET | Profusion
They even offer double-die ones for 16A, 200VDC.
ECF20N20 Metal Lateral MOSFET | Profusion
Thanks for the information re the use of the 176/56 devices specified in the DH-500.
Cheers,
Bob