|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
107.213.0.168
besides the McShane build and that's the low Mu low resistance chokes that Jeff Medwin recommended..I have been putting those in everything from Mc30s to Eico HF87s. Even tho they are only 10 ohms or 30ohms,I put the 30ohm in place of the 50 ohm power resistor that ties the doubler to the reservoir caps.They help with speed and power and accuracy in a big way IMHO and they don't raise the B+ believe it or not.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Follow Ups:
Would you care to tell us exactly what chokes those might be, Mr. S?
"
These are the chokes I use most of the time. Either of them will work but the one on the right has a higher current ratings and lower DCR and lower inductance.I use these in the Mc30s and I also use the one on the left in the Mc30s.You use one or the other and put it in place of the 150 ohm resistor in the Mc30s and the B+ goes up by a whole 2.8vdc. BFD eh?
The C36X on the left is the one I use in the HF87 in place of the 50 ohm resistors because it has plenty of current and the DCR is a little higher at 30 ohms.This fits nicely under the HF87 and you don't have to drill any holes.
Get these Chokes at Allied or Mouser.The Triad C-36X and Triad C-40X
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I just want to point out again that Hammond markets similar products that aren't made in China like the Triads you're using. I make a concerted effort not to put Chinese parts in high-end audio gear, and I know many others do too.
--------------------------
Buy Chinese. Bury freedom.
At some point I will probably try one of these low DCR chokes, using a ST-70 as a test-bed. I'll be honest and say that I'm confused regarding a lower H making an improvement, since the overwhelming opinion over the years seems to be that Dynaco's 1.5 H, 200mA C-354 choke is undervalued for that power supply.
"Buy Chinese. Bury freedom." I appreciate you taking the time to remind me of that, and offering an alternative.
"...opinion over the years seems to be that Dynaco's 1.5 H, 200mA C-354 choke is undervalued for that power supply."The output tubes draw 200ma. so that's a problem.
As for the Henry value, 1.5Hy is better than no inductance. They could have just used a resistor. 1.5Hy is better than that.
When we use a choke as an input choke, to get the full effect of a input choke (each diode, in turn, stays on for it's entire half cycle and therefore the charging current remain low without current spikes) we need to calculate and use at least the critical inductance value.
The definition of critical inductance is the inductance value that will cause the diodes to each, in turn, stay on for the entire half cycle.
That value is calculated by, critical inductance (in Hy) = ((current in amps / voltage) + the DCR of the choke) / 1000
But in a pi filter (CLC, like the Dyna uses) things are different.
"The component value for the inductor can be estimated as an inductance that resonates the smoothing capacitor(s) at or below one tenth of the minimum AC frequency in the power supplied to the filter (100 Hz from a full-wave rectifier in a region where the power supply is 50Hz). Thus if reservoir and smoothing capacitors of 2200 microfarads are used, a suitable minimum value for the inductor would be that which resonates 2200 microfarads (μF) to 10 Hz, i.e. 115 mH. A larger value is preferable provided the inductor can carry the required supply current."
I would think (but I haven't bothered to figure it out) that the 1.5Hy does meet the minimum. More would be better.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 09/16/16
Thanks for the feedback, Trè.
As for the Henry value, 1.5Hy is better than no inductance. They could have just used a resistor. 1.5Hy is better than that
Not necessarily..It depends on a lot of other factors such as filtering before and after the choke.
The HF87 that I love so much lately is powering my family room system which are Newform Research 645s..I put the typical McShane power supply in with the 820uf doublers and dual 100s downstream..This particular amp has Hexfreds in doubler and I may change over to Schotkys.I did take out the 50 ohm 10 watt resistor that ties the doubler stack to the reservoir caps.
I used a 1.5hy,50 ohm 250ma in its place and it sounded very good and I used the amp on and off for six years when I tested EL34s/6CA7s and KT77s for evaluation.
Two months ago I took out the 1.5hy choke and put in a .5hy,300ma choke that was 30 ohms.Every aspect of this amplifier changed for the better and it's like you are listening to another amp just from going to that low mu,low DCR choke. I've been streaming JAZZRADIO.com direct out of my I-PAD and I even took the DAC off..The accuracy and harmonic structure of the percussion and piano section is like none I've heard except on the big ML CLXs driven by the Citation 2s.I have never cared much for EL34s but in the HF87 with the McShane upgrades and that added choke,I've been listening non stop with unbelievable enjoyment. I wish you could hear this amp.I run the Gen reissue KT77s most of the time but this amp is a sonic marvel and I know that low DCR choke is responsible because it's the only thing I changed from the 1.5hy.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
A little late to the discussion, but, when you put in a lower value choke with lower resistance you could also change the output voltage of the power supply, especially if you're going from an inductance that is above the critical value to one that is below. If that is the case, and I'm speculating here, the voltage could change enough to alter the operating point of the circuit and that might be what you're hearing. At least worth checking out.
Thanks Mike.
What I'd be curious to know is if the power supply in your HF87 measures worse, but sounds better with the lower inductance choke.
I hear you on that and I totally agree with you.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Gee Mike, it makes me sad that I don't understand a single word of what you said. But I will stand behind your right to say it!
And by the way if that amp is so good then why only a B+. Yeah can't answer that can ya!
"The only thing I have to the Hf-50 so far is put in a 51uf solen poly off the GZ34. I also put in some Vitamin Q couplers and and a decoupler..Everything else is original including the downstream can.It's a nice sounding amp but the HF-87 murders it right now for dynamics and that's running JJ KT77s..They sound really nice if you can get a good safe pair..I prefer the Genelex RI KT77s but still it's a nice sounding tube.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
"The only thing I have to the Hf-50 so far is put in a 51uf solen poly off the GZ34. I also put in some Vitamin Q couplers and and a decoupler..Everything else is original including the downstream can"
Which of the two chokes would you advise for a HF-50?
Any other "low hanging fruit" for the HF-50? Including the "downstream can"?
FWIW… I'm running El 37's currently (with a variac).
" This is kind of tricky because you will notice that the output tubes source go directly to the GZ34.I plan on doing the Dave Gillepsie mod to all four of my Hf50s and my one pair of HF60s.If you add a choke series with the rectifier up to the output trafo B+,I would use the .5hy at 300ma as that will fit under the chassis..Wheezer things we should use a 30hy to 40 hy for the earlier stages so I'm looking into that as well.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I made the assumption that you are modding all your HF-50's to 6550's?
Any comment on using KT77's and following the front end and power supply of Dave's mod?
A couple of questions:
Are you increasing the 20mfd caps on the B+ due to the .5Hy choke?
Is the DC resistance of the .5Hy choke the same as the 3Hy on DG's mod, as this would impact the values of the R24.
Lokie
Iam modding it to 6550s.. I use a 51uf film cap,a big solen can and I will be using a choke as well..Keep in mind the that the originals were a pair of 20uf lytics in parallel for the first..The output trafo goes directly into the rectifier and the 51uf Solen.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I bet it sounds especially nice missing a 6CA7
Proudly serving content-free posts since 1984.
I bet it sounds especially nice missing a 6CA7
I took both KT77s out of the HF87 as well as the 6SN7 because I was comparing one channel of the McShaned HF87 to the HF50.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I sure like that tube lineup.
EF86 6SN7 EL34
After all these years, it still doesn't get much better than that!
--------------------------
Buy Chinese. Bury freedom.
I changed over to the Gen RI KT77 from the metal based EL34 and the KT77s are just plain better all the way thru.The EL34s sound fine if you listen and let your hearing mechanism tube and acclimate to them but the minute go to the KT77s,you gain top and bottom dynamics and definition that can't be denied..Even the JJ KT77s are fabulous,just not quite as good as the Genelex sonically.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
There could be many reasons for that other than the 77s simply being better. Have you attempted to measure the performance difference between the two types? Was NFB readjusted to accommodate differences?
--------------------------
Buy Chinese. Bury freedom.
"There could be many reasons for that other than the 77s simply being better. Have you attempted to measure the performance difference between the two types? Was NFB readjusted to accommodate differences?"
That is very true and I seem to remember doing a sweep test with the EL34s where the distortion product broadened out in the higher frequency ranges.
There is a reason that this happened and part of that could be the fact that EL34s might not like being run in UL as they would in pure pentode.
I have also come to the conclusion that Peter Walker of Quad chose the KT66 kinkless Tetrode as opposed to the EL34 to power his new speakers for the reasons I had mentioned.He could have easily chosen the less expensive and easier to drive EL34 if he thought it would produce the detailed and open sound he wanted out of his ESL-57 speakers at the time.
Keep in mind that the EL34 was out at the same time that the KT66 was.
I'm going to once again measure the EL34s on the sweep analyzers and see what happens.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: