HF-81 Kiwame Resistors and Auricaps

[NOSValves]

Mobile,

That is 1% tolerance do you have any idea what that relates to in voltage difference across the resistor ? Trust me the difference is almost unmeasurable !!

Craig

[mike stehr]

Craig,

What has been the usual readings you have been measuring from the cathode bypass resistors in the Eico units you have checked into so far?

That kinds weird, my Eico HF-12's 165 ohm resistors measured in that 170, 174 range.

I wonder if they just drift up like that from todays voltages.

When I had the guy I know look at these Eicos, he couldn't understand the 165 ohm resistors, and mentioned to use 174 or 180 ohm resistors to make the tubes run cooler.

So did Kondo San cut his teeth on Eico trannies or what?

[mobile homeless]

That is what I was suggesting to do with the modern voltages. I had questioned this earlier and was even more prone to leave it at 165 but after Jean-Francois tried the 180 himself, he said the sound was just as good with the reduced voltage which more aligned with modern voltages anyway. An additional benefit was the Ei EL-84 running without the christmas tree affect. If the sound is kept the same, going to the higher resistor rating to match the voltages and cool that amp makes sense. That being said, I have kept mine the same. Still, just as in these, mine measure over 170 anyway.

kh

[NOSValves]

Mike,

Not sure if they have drifted from time or if they just started out life like that. You have to remember these parts in the 60s were + - 20% so those 165 ohm resistors could measure 132 to ohms to 198 ohm and still be considered within tolerance. Isn't that a kick !! Wirewound resistors like this are very tuff and really don't go bad for the most part. But really raising that resistor from 165 to 180 ohms will do very little to the voltage that the cathode see's !! Thats why I find this comical. As far as them matching between channels doesn't really matter all that much either for it to matter as much as its being trumped here you would have to be running absolutely perfectly matched Quad of tubes which just aren't available and probably never were this just isn't all the crucial to the sound of the amp.

Craig

[mobile homeless]

I really don't understand this line of thought, Craig. This type of logic makes no sense to me and when you get into this frame of mind, we part company big time. First of all, the difference between 180 and 165 WILL make a difference. Jeff was reporting his Ei 6BQ5 were AGLOW and putting in the 180 reduced this to a significant amount and allowed the Ei to run much better; Roger Stevens reported the EXACT same thing with his EICO. DITTO with Mike's friend. The voltage difference between 1959 and now is a difference to be reckoned with.

Your argument that since the tubes measure differently and are hard to find matched, it is not that necessary to worry about the cathode resistors being the same is also faulty logic. You WANT the ability to be equal when you start out, despite what the tubes measure. And having both sides of this aspect the same is a GOOD start and worth the extra trouble for a balanced amp.

Lastly, once again, you miss the point on the measurements. Granted, there is near a 20% difference sometimes with these old parts. THAT IS WHY YOU BUY FOUR OR FIVE of these resistors and pick the two closest measuring examples! Why start the imbalance from the top of the chain????

One could follow your logic with picking MANY parts and come out with a hell of a piece of gear. This reverse arguing tactic of "it's close enough and doesn't make a bit of difference" is not one I think productive.

Again, the further the BIAS resistors are apart in measurement, the more difference these tube will WEAR as well. The bias of a cathode bias amp depends a good part on the tubes and these parts. Thankfully, at least with the HF-81, you are dealing with PAIRS instead of needing a matched QUAD like others such as the Dynaco SCA-35.

Personally, if replacing these, I would buy a handful at the desired voltage, and once again, use the CLOSEST two in measurement. The attitude of this being "comical" is not too comical to me.

Just one question: WHY?

kh

ps- I know you have been feeling bad, but what's your deal here? IF I pasted in all the times you thought things were COMICAL in the past, from better Turntables (remember that one) to oil caps vs Orange drops to parts to etc etc, you would be a little shocked. It has been an uphill battle.

[AndyKubicki]

The voltage difference between 1959 and now is a difference to be reckoned with.

Pardon me while I ask what may be a basic question, but what has been the change in the voltage from the early 60s and were these changes regional or all across the fruited land? I have seen you refer to this and am curious myself as that would have to be taken into account for most vintage equipment.

[mobile homeless]

Yes, the voltage almost across the board is now HIGHER than it was back then. I think with vintage gear with auto bias circuits, this can be an important difference. Is it life threatening or hugely problematic? I dont really think so, however, it is something to be aware of and could have affect on the amps performance in some parameters.

But I wouldnt lose a ton of sleep over it if you have not adjusted some specs for this. There IS a lot of variation in the specs, voltage, and parts etc across the board so this IS not an exacting science in some ways. Yet, it is best to try to be as close as you can in all undertakings for obvious reasons.

But to answer your question, there is an increase in modern voltages. If you use a tube tester, especially the Hickoks, you have a pot that actually adjusts the voltage for the time you are going the measuring. It is suprising to see how much it varies!!! But I believe the average voltage was 110V in the 50s while 117-120V is typical today. My Quebecian buddy measured about the same difference in Canada (Quebec City) as well.

kh

[AndyKubicki]

Was it not always 110-115v? Is it now 117v? I also thought that the AC frquency was about 60cps and it was pretty stable depending on the equipment. I heard of a design by Tesla which although is mechanical, it kept the frequency and voltage within a range that is still acceptable by today's standards. How much of a difference are we talking here?

[mobile homeless]

We are talking most of the voltage was around 110 or slightly below in the 50s while it is not 117 or slightly above on average today. Yes, there are variations now and then, but the 7-10 increase on the average is across the board.

see my edit above.

kh

[NOSValves]

Mobile,

You really should stick to giving people advise on what sounds good because you obviously don't have a clue about how resistance applies to voltage and the outcome of such a small change will do !! You are talking from expereince that this guy and that guy told you. You don't know any of this from expereince. If this friend of yours tubes were glowing with 165 Ohm resistors then he better check the rest of the amp out. They should not glow at all with 165 ohm resistor in this position do yours ?? I'm sure they don't !! either does chris's or mine or pauls. In fact if you like I'll get mine out and crack my variac to 130 volts and I'll garrantee the plates won;t glow on my HF-81 with 165 ohm resistors if anyone has voltage higher than that they are in trouble. The difference between the voltage today and from 1959 are different indeed and in some houses this differences is more than others changing one resistor by 15 ohms in a amp doesn't cure this difference period.

Your making it sound like I think if its within 20% tolerance thats okay and that is NOT what I said I was answering someone elses question.Your taking things out of context again. I also will repeat that changing this resistor by such a small amount isn't going to do much at all !!! Maybe the 2 people that your hearing this from house voltage is on ragged edge there are houses like that but if there plates were glowing they have a problem elsewhere in the amp also. But all this equipment from the 50s was built to run at 117V and that is the standard today !! My house never gets over 120 ever !! It just depends on where you live. If this is all that important why haven't you change them in your amps ??

When I was saying that this isn't that crucial I guess I should of treated you like a kid. I meant that 1% tolerance of these 2 is Dam good !!! Your nit picking here !

Craig

PPPPPPPPPPPPPSSSSSSSSSSSSSSS I will refrain from comments on the difference on the MMF-7 versus 90s mid fi turn table becuase it just won't help this situation at all !!!!!!!!!!!!!

[NOSValves]

Andy

If you read any schematic from the 50s they were all designed on a 117V spec. this is a fact !! There were indeed many areas of the country back then that didn't see these voltages but the products were all designed to run between 110V and 125V with 117V being optimal.

Craig

[NOSValves]

Mobile,

Just to prove a point I just went and measured the current on these 165 ohm resistors to show you what little 1% makes ....... There both a 12.08 to 12.12 !!!!!!!! It varies slightly between these 2 figure for both resistors.

Craig

Update and I just went down and tested my HF-81 its resistors are at 164 and 165 ohms 10 ohms less than chris's and its measure 12.23 to 12.34 a very small difference !! This is why I say this small of a change does very little you would need to change it more to really cool things down. Is there a chance that your friends resistors were way under value ?

[Tom Mobley]

FYI, my Eico schematic specifically notes that the test values given are at 117V, FWIW. My line voltage at my reasonably recent house and neighborhood is 117, I never see it more than a volt different from that.

Kelly, did you decide to send that assembly manual? I got my trusty HP scanner fired up.

Tom

[Pland]

Hi,

Allen Bradley type carbon resistors all drift up(less resistance )with age,and also heat.Craig is correct about cathode bias resistors in that a 5% deviation would have been well within spec for new carbon comps.Ditto for house current(mine is spot on at 117v nominal).The idea that household current has increased may have merit in some areas,but again,not enough to glow plates unless you're waaaaaay past 120-125v.I'd wager that increased household current is more myth than fact.

Matching resistors makes good sense on a self biasing amp,but again,just because it isn't much trouble to try to blueprint the circuit as much as possible.Matching output tubes would have as much or greater impact on sound.It's all cumulative.

One of the reasons Peter Qvortrup lists for the parting of the ways with Kondo San is the fact that Kondo came to believe that PP could be improved to the point that it offset any advantages to be found in SET.I'd be very interested to see if Mobile's Canadian buddy has info that an HF 81 circuit is somehow congruent with Kondo's latest thinking via PP.

Best,

Pat

[mobile homeless]

The plates in question were the Ei EL-84, Ei being the specific tube I gave for example. I have read in countless articles that the voltage has crept up and is more consistent in the 117-125 range with a more consistent 110 and average back 45 years ago. Having not been around then, I can only go on the number of references I have seen to this aspect.

I would think that an on average of 10% increase in voltage from that time would not be insignificant in the spec-ing of an amp, especially one that is cathode biased using these voltages as a standard. This has been talked about in many articles and discussed in vintage forums as well. Of course, perhaps it is an amazing leap of faith moving from the these differences make little matter to the opposite, ALL differences have some affect.

If were ARE redoing an amp and have the chance to match components, especially something like the BIAS RESISTORS, I tend to side with moving them as close to spec as possible, in addition to taking into account the different time frames and operating conditions. Everyone I have talked to points to the careful matching of the cathode bias resistors since it will change the tone of the amp. Will a few volts make a difference? Perhaps not as much in the short term, or perhaps nothing to those that don't hear much of a difference in things in the first place. But to me, a supposed 10% across the board increase in actual voltage should be accounted for if possible. And if doing something over, why disregard specifics? (When I manually bias my EL-34 UL amp, 44 is not the same as 46)

As in car engines, I personally believe in the blueprinting aspect. Yes, these differences are subtle to some, greater to others, and wholly non-existent to a vast many. But might I bring into measure the difference between 1st and 6th on an Olympic Slalom course...or perhaps the end of a 1/4 mile? Different comparisons perhaps, but maybe someone gets my point here. Obviously, this is no race...but differences do add up in all arenas.

Regardless, it's a moot point really as it's not my amp; although I was asked by the amp owner to please list all the things I considered important. I have done so. In addition, if this was MY amp, I would want the cathode bias resistors to be as close as possible. I guess it's my nature. Others prefer to focus on the "if it's a bit different it doesn't matter" approach to construction. I guess I always believe that ALL DIFFERENCES create different results. IT is just some are harder to ascertain than others. And the more precise measuring tool, whether it by a machine or the human mind, can come closer to ascertaining these differences, not to mention appreciating the distance.

Perhaps in this example, the reward is slight or the wear and/or performance inconsequential. I just don't happen to believe so.

kh

Note: Pat is right concerning Kondo and the PP circuits vs SET. The link to the EICO HF-81 is not as straightforward however. But there is a connection...

[NOSValves]

Mobile,

You are stubborn aren't you

First off whether or not the voltage creeping up on average over the years isn't the point this stuff was engineered with 117V as its ideal operating range ! Read any schematics notes and you will see this.

Yes you were asked to guide in this rebuild. I just think you showed up about 3 weeks late. I ordered parts for this project way back then. Little hard to pull 180 ohm resistors out of my a$$ here.

Now as far as Chris's amp if you would stop and listen..... the figures that I listed above for his amp at operating conditions were close to 1/10 of 1% range and that is indeed vary close !! You are never going to correct the higher wall voltage by changing the value of 2 resistors in a amp. You would have to change many many resistors to do this properly. This cathode resistor is in direct operation with pin 7 and 9 on this tube (Plates) and there voltage is directly related to the wall voltage also so by changing this value you would also need to change the voltage getting to these pins and this could go on and on throughout the amp. Do you see what I'm getting at here ?

Craig

[Deang]

Ah c'mon Craig, lemme see you pull those resistors out of your arse.

Man Kelly, I don't know, it does boggle my trying to imagine that ANYONE could ANY difference with the tolerences that are involved here. I understand what you're saying -- but damn.

[mobile homeless]

Christ Dean, we are not just simply talking about hearing the differences here....we are also talking about getting the parts right and in spec for the amp and conditions in 2002 and beyond, not to mention the various parts substitutions. Is having the damn amp biased differently descernable; well, you make the call. Does raising the resistors from 165 to 180 affect the operating points? You make the call. These are the cathode bias resistors with one dealing with one pair of tubes and the other the second pair both needed in an auto bias circuit. This is also why people call for MATCHED PAIRS of TUBES. Again, are all tubes perfectly matched? Nope, this is unfortunately not always the case. Of course, it CAN be done. Again, will all tube wear the same? Certainly not if the bias resistors are too far off... heh.

Look, it's probably fine and no reason to remove. At the described readings in the low 170s that close together, it is probably ok. The manual calls for a 5% total tolerance so there you go. Given a handful of the same reading, I know what I would do. But then again, I am like that if going through the trouble. Craig did a great job and wasnt really asked to change these values.

So there you have it. GO listen to some music!

kh

[mike stehr]

Can a guy even find a 165 ohm 5 watt cement boat resistor?

I've seen 174, and plenty of 180 ohm boat resistors.

I'd like to know if one could source a better quality resistor in these values, other than the coffin ones for the cathode bypass resistor application.

I know there is something.

[Chris Robinson]

I'm going to (once again) take on the wimpy role as moderator and say that I see merits on both sides.

From a normative view, yes -- given the option and opportunity to precisely match those resistors -- that would have been great. And from a subjective view point, if Craig asked me if I would want to wait another two weeks for them, I probably would have passed because I find it hard to be without Klipschorns and vinyl for that length of time.

I have proxied my vote on this one -- but I did take Kelly's (and others') advice on two points early on, which I then passed on to Craig and he accommodated them happily (try the Auricaps and secure the big blue caps to the chassis).

There is one curve ball here which noboby's brought up and I haven't volunteered because I didn't want to muddy the waters of this discussion. I -- um, how do I put this -- live in kind of a small town. We're slated to get a traffic light in 2008. Hell, we just got plumbing. Our power goes out about three times a week when the weather's good (all our clocks are battery-powered and synch'ed with Colorado) and our voltage regularly goes between 105 and 120, depending. I think our power plant/grid is about as old as Edison. I would think this would have an effect?

So .... about the only solution I think would be to put a decent UPS between the wall and the amp ... but I've heard in other threads that they degrade the sound by themselves.

Jeez, I think I need to move It's just the weather up here that I love (as I look out the window at 3/4" of ice on everything).

Where's that Zamboni?