First off, I agree that HexFreds are not required, and the grounding can be improved, no doubt. The original rectifiers in the Cit II were the "top hat" silicon diodes rated at .5 amps and 600 PIV - the 600 volt rating required two diodes be used in series in each leg to get PIV high enough to be reliable. With new modern fast/soft recovery diodes in place, the capacitance in the doubler and the decoupling caps especially can be increased significantly and of course cap quality should be improved as well. Kevin was concerned about the ripple out of a doubler - it's not an issue with caps rated for 2.6 amps of ripple and ESR under .2 Ohms along with 105 C temp ratings (it's WARM under the hood of a Cit II!).
FYI - I use a number of metal films in my kits and when I redo a Citation II amp. There have been ZERO problems, because they're used in the right positions in the amp. To redo all the resistors you'll need wirewounds, metal oxides, metal films, and even a couple carbon comps - all of them have a role to play.
And the stock coupling cap values are fine, but at their age they gotta go!
There is no need to enlarge any holes. There are FAR better parts that fit the stock locations and require no cutting - which I DO NOT recommend.
There are no PCBs, there are two turret boards. And be aware the sockets are small opening/narrow mounting saddle sized - they fit a 1" opening.
I agree to a point, go slow, take your time, don't make ill-advised changes to the amp. A Cit II is not an easy amp to work on in any case, as it is crowded in there.
Yes, to each his own - but this is the 1st time I've ever heard this said. As SY said in a post sometime back - the amp didn't become a legend because it was poorly done (or words to that effect). I've worked on both amps - and I absolutely do not agree that the HF-87 is better.
The youngest Cit II in the world is about 50 years old - well past the design life for the caps, resistors, etc. It all has to go at this point.
You have no choice in the front end, 12BY7As are not in production anymore. And while the EH is an excellent tube (and an excellent value) my choice of tubes for the output are either the Ei KT-90 type I or type II (if you have them, if you don't forget it) or the Genalex reissue KT-88.
Unless you are intimately familiar with the Cit II it's difficult to grasp how different it is as compared to a typical Williamson or Mullard circuit. Stu Hegeman was no slouch, the design was first rate all the way. There has never been an amp like it since - and fully redone/upgraded it is an amazing audio product.
Back in the day many of the cans were -10% +50% (or more) tolerance. Second I challenge your statement that significant increases in cap value are inappropriate. As Kevin said the limitations of capacitor (and rectifier) technology of the day made even the top hat diodes and 200 uf caps in the voltage doubler extremely costly for a production amp. I can imagine what the H-K bean counters said when Hegeman told them what parts he needed to use!
I find significant increases in capacitance (increases of about 4x) - and the huge leaps in quality of modern caps as compared to what was available then - make the amp come alive. But when it was designed/built that was simply not possible - now it is.
So you are saying use of inrush limiters is inappropriate? Addition of (2) strategically located limiters allows us to drop the stock fuse value from 8 amps to 6 amps, and as Eli said it stops the magnetostriction-induced CLANNNGGG! from the power trafo you will hear at times at turn on. I think those are significant gains in performance!
Sure, some sort of time delay based method is fine - but with all the other things going on it's hard to find room under the hood for the components needed for it.
I agree, the EH and the other New Sensor brands are excellent. But there are no 12BY7As (or drop-in subs) in current production, so there we have no choice...
Cripes,, look at when that was written, (~15yrs ago, and it dates much further back to an early issue of the original paper edition of Positive Feedback) thanks for pointing it out to me. It should be removed, but I have little enough time as it is, rewriting stuff from decades ago is not high on my list of priorities, (not that I even remember writing that) and I agree that photoflash aren't suitable, but enjoyed a brief spurt of popularity back in the 1980s due to their extremely low ESR and before people figured out that they caught on fire. The load current in the bias supply is pretty low and I never had any problems with those caps, but I don't recommend this approach any longer. (And haven't since early in the Clinton era.)
Kevin, if you wrote that 15 years ago you were what, 27-28 years old back then??
All kidding aside, I agree that the modern extremely compact photoflash caps are not suitable. But I've used the late 70s Marcon photoflashes in my own personal amp for 20 years with zero failures or problems. Until I couldn't get any more I used them in customer's Citation gear - I used probably 150-200 of the Marcon caps - again with ZERO failures.
I did screen them by running them at 10% over rated voltage and measuring leakage current through them. If it wasn't under 1 ma after 30 minutes I didn't use the cap.
I just had the good fortune to get (free!) some recent date code CDE 7P series photoflashes. These are heavy and well made and I wouldn't hesistate to use them today as long as the temperature was within the caps' spec.
Agreed. At idle the stock amp draws over 400 ma. since the (6) 12BY7As use roughly 50 ma in total as well. V1 and V4 (the input tubes) each draw over 15 ma. That speaks to the need for substantial decoupling capacitance as well - it's not some 12AX7 running under 1 ma. you are working with.
You're correct, the HV secondary is rated at 1.7 amps and 170 volts. And managing inrush apparently was a problem for H-K - I have a couple service bulletins from the 60s that dealt with a) reducing power tube idle current from 100 ma. per tube to 90 ma. per tube, and b) adding 2.2 meg resistors across each top hat. They must have blown some...
Again, I have installed or sold probably 1000 or more inrush limiters (not just any NTC device, these have very long time constants and are designed to operate at higher temps).
FWIW...
The matter of voltage doubler PSUs has been raised. It's (IMO/IME) important to note that McIntosh (several models), the Marantz 8B, and the H/K Cit. 2, all highly revered, use a Greinacher ("full wave") doubler for B+. Attention to detail is (IMO) what yields a high performance PSU, as long as the topology selected is rational.
In the case of the "Deuce", the OEM filter choke is low DCR. While an inductance of 1.5 H. is not particularly powerful at the ripple's fundamental freq., that's not its principal function. The primary functions of the choke are to kill ripple overtones off and (possibly) SS diode switching noise. The ripple waveform in a cap. I/P filter is "triangular". That brings Fourier's theorem into play and we are informed that overtones are present, extending into RF. When, as Jim McShane does, the I/P capacitance is large, the waveform is quite "sharp" and that implies lots of overtone energy is present. The effective capacitance of the filter choke is large enough to act as a bypass at RF. Adding a LC "hash" filter made from a high current RF choke and a 1000 pF. cap. (either mica or NPO ceramic) between the doubler stack and the 1.5 H. choke blackens the background by killing the worst of the RF energy off, before it gets to the main inductance.
In the case of the "Deuce", the OEM filter choke is low DCR. While an inductance of 1.5 H. is not particularly powerful at the ripple's fundamental freq., that's not its principal function. The primary functions of the choke are to kill ripple overtones off and (possibly) SS diode switching noise. The ripple waveform in a cap. I/P filter is "triangular". That brings Fourier's theorem into play and we are informed that overtones are present, extending into RF. When, as Jim McShane does, the I/P capacitance is large, the waveform is quite "sharp" and that implies lots of overtone energy is present. The effective capacitance of the filter choke is large enough to act as a bypass at RF. Adding a LC "hash" filter made from a high current RF choke and a 1000 pF. cap. (either mica or NPO ceramic) between the doubler stack and the 1.5 H. choke blackens the background by killing the worst of the RF energy off, before it gets to the main inductance.
Thanks for the memories!
The Citation 11 is very dear to my heart not only because it was my first major DIY rebuild back in the early 1980s, but because of the sheer enjoyment of listening to music with that system - it came from Olympic Studios in SW London [and had been used for bass guitar work on the Stones' 'Sticky Fingers' album!!]. It worked but was a bit 'woolly' so I replaced all caps and resistors and links - in fact virtually everything other than the iron. [The associated Citation 1 was too much work and was left alone. It was not much good.] The refurbished Citation 11 was absolutely wonderful....from memory it had some areas to criticise but it could certainly involve me in the music - it is one of the few amps I have owned which I really regret selling. Others include Radford 15 and TT100....these also came from Olympic when it changed hands to Richard Branson's Virgin Studios as did 10 Tannoy 15" Gold drivers and xo units, a pair of Silvers and a couple of c24 mics.......Had I had the room in my small London house to keep all of this stuff I would still own it . Sadly Olympic Studios is no more since EMI bought the Virgin interest and closed the operation.
The Citation 11 is very dear to my heart not only because it was my first major DIY rebuild back in the early 1980s, but because of the sheer enjoyment of listening to music with that system - it came from Olympic Studios in SW London [and had been used for bass guitar work on the Stones' 'Sticky Fingers' album!!]. It worked but was a bit 'woolly' so I replaced all caps and resistors and links - in fact virtually everything other than the iron. [The associated Citation 1 was too much work and was left alone. It was not much good.] The refurbished Citation 11 was absolutely wonderful....from memory it had some areas to criticise but it could certainly involve me in the music - it is one of the few amps I have owned which I really regret selling. Others include Radford 15 and TT100....these also came from Olympic when it changed hands to Richard Branson's Virgin Studios as did 10 Tannoy 15" Gold drivers and xo units, a pair of Silvers and a couple of c24 mics.......Had I had the room in my small London house to keep all of this stuff I would still own it .
Sadly Olympic Studios is no more since EMI bought the Virgin interest and closed the operation.The Citation 11 is very dear to my heart not only because it was my first major DIY rebuild back in the early 1980s, but because of the sheer enjoyment of listening to music with that system - it came from Olympic Studios in SW London [and had been used for bass guitar work on the Stones' 'Sticky Fingers' album!!]. It worked but was a bit 'woolly' so I replaced all caps and resistors and links - in fact virtually everything other than the iron. [The associated Citation 1 was too much work and was left alone. It was not much good.] The refurbished Citation 11 was absolutely wonderful....from memory it had some areas to criticise but it could certainly involve me in the music - it is one of the few amps I have owned which I really regret selling. Others include Radford 15 and TT100....these also came from Olympic when it changed hands to Richard Branson's Virgin Studios as did 10 Tannoy 15" Gold drivers and xo units, a pair of Silvers and a couple of c24 mics.......Had I had the room in my small London house to keep all of this stuff I would still own it .
Just to avoid any confusion, you had the Citation TWO tube amp, correct? There is a Citation ELEVEN solid state amp as well. I'm sure you were referring to the tube amp even though you typed Citation 11, not Citation II. Yes?
Also - there are a LOT of people who would disagree strongly with your statement about the Citation I preamp being "not much good". I do agree it is a LOT of work to redo, but it's quite good when it's properly redone - especially the phono stage. When you look at a stock one and see (6) .47 uf 3 volt CERAMIC discs used as couplers in the phono stage you KNOW it needs help to be its best! Yes, the complexity can be a PITA; but a lot of people use them for old pre-RIAA curve records since it can handle a wide range of EQ recordings.
Thanks for sharing the story about the use in the studio!! Stu Hegeman - the Cit II designer - was a recording engineer and understood the process very well. I'm not surprised to hear the amp was used in the studio, but this is the first time I have heard of any specifics. Much appreciated!!
Kevin, if you wrote that 15 years ago you were what, 27-28 years old back then??
All kidding aside, I agree that the modern extremely compact photoflash caps are not suitable. But I've used the late 70s Marcon photoflashes in my own personal amp for 20 years with zero failures or problems. Until I couldn't get any more I used them in customer's Citation gear - I used probably 150-200 of the Marcon caps - again with ZERO failures.
I did screen them by running them at 10% over rated voltage and measuring leakage current through them. If it wasn't under 1 ma after 30 minutes I didn't use the cap.
I just had the good fortune to get (free!) some recent date code CDE 7P series photoflashes. These are heavy and well made and I wouldn't hesistate to use them today as long as the temperature was within the caps' spec.
Agreed. At idle the stock amp draws over 400 ma. since the (6) 12BY7As use roughly 50 ma in total as well. V1 and V4 (the input tubes) each draw over 15 ma. That speaks to the need for substantial decoupling capacitance as well - it's not some 12AX7 running under 1 ma. you are working with.
You're correct, the HV secondary is rated at 1.7 amps and 170 volts. And managing inrush apparently was a problem for H-K - I have a couple service bulletins from the 60s that dealt with a) reducing power tube idle current from 100 ma. per tube to 90 ma. per tube, and b) adding 2.2 meg resistors across each top hat. They must have blown some...
Again, I have installed or sold probably 1000 or more inrush limiters (not just any NTC device, these have very long time constants and are designed to operate at higher temps).
FWIW...
Hi Jim,
Good to hear from you..
The article in question dates back to about 1989 - 1991 or so which would have made me early 30s at the time. 
(I'm a bit fuzzy as to when I wrote it as I put it up on the site a long time later.)In fact those photoflash were Marcon, and I had problems with one in just one specific instance, and that cap was operated within 10% of its voltage rating in the power supply of my first serious pre-amp design, and it caught fire on a very, very hot day. This was the only problem I ever had with those caps, but I did stop using them in new designs at that point. This particular cap had operated for over a year without any obvious issues, and the pre-amp where it was used continued to play unphazed as it burned - the cloud of smoke rising from the power supply chassis was the only obvious clue.
I replaced the original silicon rectifiers with modern ones of various sorts over the years I ran that amp. Never had any problems with them. My concern in replacing the originals was the significant additional inrush current from the cap upgrades.
Sounds like you have found the right NTC for this application..
You have to use an inrush limiter, you need the longer time constant and the ability to operate at higher temps and remain well within the limiter's specs.
And I don't use them in the "traditional" spot for a variety of reasons.
If you haven't as yet look at the Thermometrics data sheet, it's very good reading!
Yes, CITATION 2. Tubes. way:er than the eleven!!!
The matching Citation 1 pre amp was beyond my scope at the time, I used a Counterpoint preamp it. I sold it to a very keen West Indian who had as a younger man been to a NY show and had hankered for these items from that time on. I guess he almost certainly still uses it.
AS I say I would like to still have it with me.
er than the eleven!!!The matching Citation 1 pre amp was beyond my scope at the time, I used a Counterpoint preamp it. I sold it to a very keen West Indian who had as a younger man been to a NY show and had hankered for these items from that time on. I guess he almost certainly still uses it.
AS I say I would like to still have it with me.
Hi Jim,
Hey, we are mostly saying the same thing. On top of that, I have another Citation II (2) that I am working on right now. I am pretty familiar with all these beasts, although I don't tend to make a lot of noise about it. Most of your issues were splitting hairs anyway.
I strongly disagree with you on the increased filter capacitors though. I disagree for a number of reasons, none of which are something you would listen to and report as an upgrade. Also, back when I worked in the parts end of the trade, electrolytic can caps had a tolerance of - 20% and + 50 %. Earlier ones were even looser with the tolerances. The exact value wasn't so much an issue back then - within reason! Leakage was more the issues we worried about. Another point was that a flash capacitor was designed for an entirely different service than normal filter capacitors. I guess you could search and find one or two brands that put up with the filter cap use. The problem is that many happy souls reading this on the internet do not make that distinction. They grab surplus flash caps, or cheap new ones, and away they go. Personally, I have always found that you are better off using parts designed for the application you are using them for. And absolutely yes! The ripple current in a doubler circuit is a factor to consider when you are buying replacement capacitors.
I also do not agree with enlarging chassis holes, but the reality is - people always want to use the hot new part. The main concern is that chassis changes are done now, not later once the parts are back in. That was my point, no where did I suggest that this is a good thing to do. I learned a long time ago that many people will ignore good advice and do what they wanted to do anyway.
An NTC resistor needs to remain hot in order for the resistance to be at a low level - yes? At least that is how every single solitary NTC resistor I have ever known about works. In contrast, a relay contact shorting out the surge resistor (this is what I preferred, remember?) does not incur any power loss due to a voltage drop. Wouldn't you agree that this is a true statement? That is all I said, and I'll stand by that idea. Put them where you figure they work best, whatever you installed.
The only place for a carbon composition resistor is in high frequency work. That includes grid stoppers to prevent oscillation. Their voltage co-efficient precludes their use anywhere else in sound reproduction equipment. In guitar amps (and similar), they do play a part in "the tone" of an amplifier. Yes, I restore guitar amps as well. Information on resistors for those does not apply to amplifiers for sound reproduction.
The first Eico HF-87 I restored was found in a recording studio called "The Metalworks" up here in Canada. I did some work out of there. It was rebuilt from the ground up using my methods and part choices. I did not use the internet or any magazine for any information in order to determine the parts I ought to use. What I did do was to make sure the new parts fit properly, and they ended up in the same physical space that the originals did. I had to use the service manual since someone already hacked the amp trying to "improve" it. It is the cleanest amp I have ever heard, a real keeper (which I did). SY heard it, but it was failing at the time. Time to service it again, but it was pretty much stock the way I built it. Is it possible that the way you build them, they don't perform to their best? Oh, 6CA7's for the outputs. Makes a difference. Anyway, heard both models. I disagree with you, but it's all about preference, isn't it?
I'm sure there are other statements you made that I could take issue with. Just stop to consider that we are two technicians, and we each have our ways to do things. Beyond things that may be technical, the rest is only opinion.
Jim, on a different topic ... Recently rebuilt a Citation IV preamp. The tone controls seem to be really messed up. No control position will give you a flat response. Is the manual wrong somewhere? Both channels exhibit identical response. I had to rely on the manual since this poor thing had been "done up" following some popular web information. Not your site, and I'm not aware you have anything on it or not. The Citation II I'm working on was bone stock (thank god!).
-Chris
Hey, we are mostly saying the same thing. On top of that, I have another Citation II (2) that I am working on right now. I am pretty familiar with all these beasts, although I don't tend to make a lot of noise about it. Most of your issues were splitting hairs anyway.
I strongly disagree with you on the increased filter capacitors though. I disagree for a number of reasons, none of which are something you would listen to and report as an upgrade. Also, back when I worked in the parts end of the trade, electrolytic can caps had a tolerance of - 20% and + 50 %. Earlier ones were even looser with the tolerances. The exact value wasn't so much an issue back then - within reason! Leakage was more the issues we worried about. Another point was that a flash capacitor was designed for an entirely different service than normal filter capacitors. I guess you could search and find one or two brands that put up with the filter cap use. The problem is that many happy souls reading this on the internet do not make that distinction. They grab surplus flash caps, or cheap new ones, and away they go. Personally, I have always found that you are better off using parts designed for the application you are using them for. And absolutely yes! The ripple current in a doubler circuit is a factor to consider when you are buying replacement capacitors.
I also do not agree with enlarging chassis holes, but the reality is - people always want to use the hot new part. The main concern is that chassis changes are done now, not later once the parts are back in. That was my point, no where did I suggest that this is a good thing to do. I learned a long time ago that many people will ignore good advice and do what they wanted to do anyway.
No, completely the opposite. Read more carefully.
An NTC resistor needs to remain hot in order for the resistance to be at a low level - yes? At least that is how every single solitary NTC resistor I have ever known about works. In contrast, a relay contact shorting out the surge resistor (this is what I preferred, remember?) does not incur any power loss due to a voltage drop. Wouldn't you agree that this is a true statement? That is all I said, and I'll stand by that idea. Put them where you figure they work best, whatever you installed.
Okay. Sure. You are the tech working on a given amplifier. You are the one who decides where the customer's money is best spent. You decide how much room each change will take up.
Listen Jim, you know as well as I do that you can certainly spend more money on parts where they may not improve the performance if you want. This in itself will not cause problems down the road. In fact, I also use close tolerance metal film resistors with low tempco's in certain places (notice the secrecy?). However, there are locations in that amplifier that will exceed some voltage ratings for modern resistors. Remember that this information is not aimed at building up an ego. It is aimed at those people who are learning and need to be made aware of these situations. I have seen (recently) metal film resistors rated at 50 VDC, 100 VDC and other various ratings on up to 750 VDC. Then we get into the expensive 3 KV parts that are also available. People need to be aware that these parts (resistors) can have voltage ratings that are lower than their power ratings would suggest. It is important to make people aware of this.
The only place for a carbon composition resistor is in high frequency work. That includes grid stoppers to prevent oscillation. Their voltage co-efficient precludes their use anywhere else in sound reproduction equipment. In guitar amps (and similar), they do play a part in "the tone" of an amplifier. Yes, I restore guitar amps as well. Information on resistors for those does not apply to amplifiers for sound reproduction.
No kidding. I work on stuff that's much older. I enjoy restoring test equipment as well. What's your point? This issue wasn't something you disagreed with to the best of my knowledge.
The first Eico HF-87 I restored was found in a recording studio called "The Metalworks" up here in Canada. I did some work out of there. It was rebuilt from the ground up using my methods and part choices. I did not use the internet or any magazine for any information in order to determine the parts I ought to use. What I did do was to make sure the new parts fit properly, and they ended up in the same physical space that the originals did. I had to use the service manual since someone already hacked the amp trying to "improve" it. It is the cleanest amp I have ever heard, a real keeper (which I did). SY heard it, but it was failing at the time. Time to service it again, but it was pretty much stock the way I built it. Is it possible that the way you build them, they don't perform to their best? Oh, 6CA7's for the outputs. Makes a difference. Anyway, heard both models. I disagree with you, but it's all about preference, isn't it?
I'm sure there are other statements you made that I could take issue with. Just stop to consider that we are two technicians, and we each have our ways to do things. Beyond things that may be technical, the rest is only opinion.
Jim, on a different topic ... Recently rebuilt a Citation IV preamp. The tone controls seem to be really messed up. No control position will give you a flat response. Is the manual wrong somewhere? Both channels exhibit identical response. I had to rely on the manual since this poor thing had been "done up" following some popular web information. Not your site, and I'm not aware you have anything on it or not. The Citation II I'm working on was bone stock (thank god!).
-Chris
I don't agree Chris, there are major differences in many of the positions taken.
Meaning what? What reasons are you referring to?
The proof is in the eating, as the old saying goes. People who have heard the amps I've done or have been done with the parts I supply...
1. Absolutely rave about the sonics, and
2. Have ZERO problems - and many of the amps have 10 years on them now. I've had ZERO diode failures; ONE bad cap in a voltage doubler, none anywhere else; ZERO inrush limiter failures; and not a single failure of any sort related to power supply performance.
Many 100s of Cit IIs have been done using the revised power supply with the much larger capacitance and the results have been superb. So while you are certainly entitled to disagree there is overwhelming empirical evidence that speaks the the success of my approach.
Yes, that's pretty much exactly what I said. But to think that back in the day the COST of larger amounts of capacitance wasn't a factor impacting what went in the amp is a bit naive IMHO. There's a famous story about old man Grommes (Grommes Precision tube gear from Franklin Park IL) who would go to the engineer who had completed an amp design and tell him to start removing parts from the design until the amp didn't work right! That was not an isolated case, the cost of silicon diodes and large high quality capacitors was a major contributor to the overall cost of manufacturing the gear so the pressure to economize was strong.
I can't control what other people do. But I can use good practices in selecting what I provide/use in these amps. And the parts I use and the way I use them has a long track record of success.
Read WHAT more carefully??
Yes.
Let me make this clear - as I wrote before the concept of using time delays is fine with me. I use a two-stage delay in my own amp because I use about 1800 uf of Marcon photoflash caps per channel, and that requires it. But to imply that is the ONLY way to achieve the goal is inaccurate.
I use specialized parts that are designed to be used as inrush current limiters. They are designed to run "hot", and I ensure they don't run too hot by selecting the right location and right part from the series. And ZERO failures, as I mentioned.
I think we agree that proper selection - paying attention to ALL the specs - is the right way!
I don't agree - a grid stopper is an IDEAL place for a carbon comp. The current through a grid stopper is vanishingly low, so the "micro-arcing" that causes so much of a carbon comp resistor's noise is not occurring; and the exact Ohmic value is not critical so the drift that occurs with CCs is not a concern.
Enough on that.
There is a front panel Tone Defeat switch that takes the tone controls out of the circuit. But if it was reworked before who knows what's connected to what. If you use the switch does the problem go away?
There is nothing inherently wrong with the Cit IV tone controls. Do make sure the pots are in good shape - we find some with the carbon element starting to crumble. Also the resistors and caps in the tone circuits are often pretty tired. Finally, be sure that V2 is in good shape.
I hate to dredge up an old thread, but I've gone and picked up another Citation II. I was reading this thread where Jim suggests the use of a CL150. I think my first Citation II rebuild back around 1998 used one of those. But I've settled on the CL-50. It's a larger disk, (0.75" vs 0.55") and is also a 5 amp part. It has a bit higher resistance at 25% of rated load, but given the bias current and filament draw, the amp never operates down that low on the load line anyway.
The important metric in the data sheet is Dissipation Constant. The larger disks have a constant of 25mW/degC. And the smaller ones (like the CL-150) have a constant of 15mW/degC. Which means that the CL-150 will be running about twice as hot as the CL-50. Not a huge deal in an amp that is more space heater than amplifier, but given the lack of cost difference, I go with the cooler running part.
Sheldon
The important metric in the data sheet is Dissipation Constant. The larger disks have a constant of 25mW/degC. And the smaller ones (like the CL-150) have a constant of 15mW/degC. Which means that the CL-150 will be running about twice as hot as the CL-50. Not a huge deal in an amp that is more space heater than amplifier, but given the lack of cost difference, I go with the cooler running part.
Sheldon
Using 2 chokes in Cit II for better channel isolation
Hi,
Has anyone thought of using 2 chokes in the power supply for better channel isolation? Basically, right after the voltage doubler stack, you connect the chokes; one goes to the right channel and it's bank of capacitors, and the other choke goes to the left channel and it's capacitors. There's room under the other output transformer for the 2nd choke.
Hi,
Has anyone thought of using 2 chokes in the power supply for better channel isolation? Basically, right after the voltage doubler stack, you connect the chokes; one goes to the right channel and it's bank of capacitors, and the other choke goes to the left channel and it's capacitors. There's room under the other output transformer for the 2nd choke.
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