🔊 Audio The Vacuum Tube Geeks Thread

I had a bit of an issue here almost three weeks ago--it sounded like the stylus was mistracking on the records. (Jumping ahead for a second, it's like there's a fuzziness and weakness in the highs.) Tried another phono stage and removed an attenuator with no change, and then I tried digital and got a similar result. After some deduction, I figured since I had a lot of hours on them, the tubes in the power amp were getting old. Swapped in a pair of GE JAN 5751s, and I thought it might have improved things a bit, so I bit the bullet and got two new Tung-Sol 5751s and a quad of KT120s from Uncle Kevvy.

Those arrived, got them installed. Went to bias the KT120s and noticed the bias LEDs aren't illuminating, even if I turn the adjustment pots briefly through the entire range. So, there's something internal going on here. Contacted Music Technology in Virginia and it looks like I'll send it down to them for a repair. The president was the technical director at C-J, and worked there over 20 years, so he's the go-to guy for repairs. C-J can also repair directly, but they tend to want to push their teflon capacitor upgrade, which costs more than I paid for the amp, and I'd never get that out of it if I tried to sell it. (I've seen others try to sell similar models and try to recover the capacitor upgrade, and they sit unsold.)

I'll miss it while it's gone, but have the PA-7 to shlep out of the basement and drag into my system. (It's a heavy beast.) The site shows a 10-12 week turnaround time. While it's there, I'm having him address the very slight channel imbalance, check on doing the upgrade to the 11A (from the 11, which is the addition of a diode), and add an IEC socket so I can use my own power cord, as the original was nicked and taped up by the prior owner, and I have a couple of spare power cords here.
 
Temporarily, I may move the new-ish amp from my desktop into my main system. (The other tube amp did not work out, and is mothballed for now.) I may do a little write-up here of that piece, as it's impressive for its size and is a good go-to for some looking for a small but flexible component to build a system around.
 
I'll miss it while it's gone, but have the PA-7 to shlep out of the basement and drag into my system. (It's a heavy beast.)
And I did that this afternoon. It's a nice amp, but right away I could hear the (not good) change in sound. Back to that metallic, "steely" sound that I've heard with McIntosh solid state amps (which I do not like, and never have). So this will do, but it's no tube amp. Granted the PA-7 needs a refresh also, as the electrolytic capacitors are at or near end of life, and Nelson Pass (who designed it) mentions that they can stand to be recapped when they are this old. But my choice there is to do it myself and figure out how to adjust the bias when I'm done, or send it off, 2/3 of the way across the country and hope that UPS or FedEx don't destroy it along the way.
 
We once got a shipment of reel tapes at work that FedEx had not only dropped off the truck but had run over. :cussing:
 
Back to that metallic, "steely" sound that I've heard with McIntosh solid state amps (which I do not like, and never have)
I know what you mean. I remember my father switched out his Scott 340A for some solid state affair in the late '70s...The new receiver punched harder -- as a teenager I thought it was great. As an adult I've been on tubes for over 20 years now. I've had two vintage amps from the early '60s but now run a nice little Luxman (with those sweeeet EL84s). I could never return to solid state.
But my choice there is to do it myself and figure out how to adjust the bias when I'm done
Lo! The other side of the coin with tube amps. Everyone I know (except me) maintains their amps -- particularly the '50s/'60s equipment, which in all cases is refurbished or even rebuilt. I've just never developed an interest in EE (much to dad's chagrin I studied chemistry). In any event, it is fascinating when my friends start talking all that well your rectifier isn't syncing with your floating parahprase inverter producing the capacitance required to... business. Once the music conversations switch gears into electrical engineering, I go to the ice box and grab a Schlitz...
 
I've had two vintage amps from the early '60s but now run a nice little Luxman (with those sweeeet EL84s). I could never return to solid state.
I know of some who run those old H.H. Scott or Fisher integrated amps or receivers that are tube powered, and love 'em to bits. The only thing is, now that the secret is out, finding a clean, refurbished example of either one will run several hundred dollars. That is something I'd use in a second system (in a den or other small room)--it'd be perfect size-wise, and sound really nice. It's one of those things where I hope to luck across an old one at an estate sale, pick it up for $50, and freshen it up to keep as a spare, or hand it down.

Lo! The other side of the coin with tube amps. Everyone I know (except me) maintains their amps -- particularly the '50s/'60s equipment, which in all cases is refurbished or even rebuilt.
Some of the newer amps today (like those by PrimaLuna, and others) are self biasing. But with mine, it's a simple process, and you only have to attend to it when you replace the tubes, and maybe tweak it a week or so after the tubes settle in, then once or twice a year. Essentially, you turn the potentiometer for each tube in one direction until the LED illuminates, then back it off until it juuust extinguishes. Since I run mine with the tube cage off (as most C-J owners do), the pots are accessible right on top of the panel for easy access. No opening up the case, and no multimeter needed. The biasing in this case promotes longer tube life, and ensures the channels are balanced.

I know a few who build their own tube amps, and I'm envious of the skills they have acquired in being able to tune those things, and know exactly which values to change to affect the sound in the way they desire. They also seem to have encyclopedic knowledge of dozens of tubes and how they act in a circuit.

I'm great with soldering, and could easily build a tube amp kit but my electronics years were in the solid state era, and our textbooks never covered vacuum tube circuits. For me, I'd have to relate how a tube functions to its solid state equivalent, to get a grasp on it. For tube amp kits, I was for a while considering the Bob Latino M-125 kits, which are basically higher-powered monoblock variations on the old Dynaco Stereo 70 amps.

But I can't complain--I got my amp four years ago from a seller who was facing some dental bills and wanted to get rid of it, and it's worked fine. But it's almost 30 years old, so it was destined for a look-over anyways. And I've wanted the IEC socket so I could replace the power cord, and the repair shop can do that for me.
 
We once got a shipment of reel tapes at work that FedEx had not only dropped off the truck but had run over. :cussing:
I think they were a better company back before they got into ground-based delivery. They took on ground delivery when the Roadway freight company sold off their RPS spin-off, basically a UPS clone, to Federal Express a long time ago.

I've had good luck with our drivers at the house--they deliver to an area that isn't easily accessible, vs. leaving things on the front porch in full view of the street. But I've heard of others who have careless delivery drivers, who would toss packages from a distance, leave them in poor areas, or deliver to the wrong address. Not to mention problems at the distribution centers where boxes are tossed around, or allowed to fall off the conveyors. Not pretty!

I did have that happen once with a set of struts for one of the cars here. I had gotten a delivery notification when I was leaving a local audio club meetup (which was more about drinking and eating than listening to music 😁). Got home...nothing. Looked at a couple of neighbors' houses, nothing there either. Got a text message the following day--a neighbor one street over with the same street address number had gotten my two heavy boxes. I thanked her and picked them up. As these things go, not too long after, I got a package for her, and we had to arrange a similar pickup.

We keep meeting like this, and people are gonna talk. 😁
 
Wow--what a great hobby to have dealing with audio electronics, vacuum tubes and the like. My uncle in the 1960s, in his opinion, felt that the Mac Intosh tubes were the top of the heap for his audio system.
 
As a follow up--I just read that tubes in their heyday were very powerful and not vulnerable to electromagnetic pulses. Also today some musicians still prefer tube amps over their solid state counterparts.
 
Tubes are kind of a tradeoff. They burn a lot of energy that does not directly translate into power that eventually ends up going to the speakers. They aren't really "powerful" per se--the most powerful audio tube made today is the new production Tung-Sol KT170, a pair of which could probably put out 160-175 watts. But there's power in numbers. Three classic Conrad-Johnson amplifiers have the same basic circuitry but have different outputs based on the number of output tubes. The Premier 11 gets 70 watts out of a pair of 6550s (or equivalents like the KT88 or KT120) per channel. Premier 12, same circuit but in a monoblock configuration, puts out 140 watts from four 6550s and the Premier 8 is at 275 watts with eight 6550s. (For reference--at idle, a single Premier 8 I believe draws over 500 watts. So it's over 1,000 watts to run a stereo pair.) So theoretically you can (putting this really simply, without getting into electronics theory) chain many tubes together to get more output. Taken to an extreme, the Carver Silver Seven uses twenty (!) KT120 tubes per channel to output 900 watts RMS.

Silver Seven | bobcarvercorp.com

The other thing with tubes is that even today, you still see some lower powered tube amps driving high-efficiency speakers, which are often horns. One watt into a pair of Klipschorns would be louder than we can stand it, and it's not uncommon to see some horn speakers driven by 10-15 watt amplifiers. (The opposite would be an old pair of Advent speakers--they were very inefficient in comparison, and would need hundreds of watts to theoretically play as loud....only, the drivers would burn up before they could ever play as loud as Klipschorns!)

For uses beyond audio, there were more powerful vacuum tubes for things like radio transmitters. Such as this 100 kilowatt tube that was introduced almost 100 years ago.


For guitar amplifiers? My buddy had a Fender from the 70s and sold it in the mid 80s for under $100. I saw a larger version of that same amp, in somewhat ratty condition, for sale at Guitar Center for $1,100. Where a new, similar-sized solid state amp probably would have cost $250. There are also new production tube guitar/bass amplifiers. One of the characteristics of tubes is how they overload--they have a smoother distortion than a solid state amp when overdriven, so they are more in demand.

Today's polar opposite are Class D (switching) amplifiers. What's amazing is that the better Class D modules sound excellent, yet they are very small, and run cool. I have a 50W RMS x 4 Class D power amp in the car that I can fit in the palm of my hand; in the past, I need a huge "plate" amp mounted in the trunk for the same amount of power.
 
Brief update on the tube situation...thanks to the ongoing "festivities" with Russia, new tubes have gone up in price. Some tube sellers are saying there isn't yet a shortage, but many new tubes today are made by New Sensor Corp. in Russia and marketed under various brand names (including many historic brands like Tung-Sol, Mullard, Gold Lion, etc.). Unfortunately, the now-common power tubes like the KT-120, KT-150 and the new KT-170 are made only by Tung-Sol/New Sensor, so supplies on those could dry up.

Prices have already gone up on KT-120s--normally they would be around $50/tube from reputable dealers. Now they are as much as double the price, depending on the dealer.

Thankfully, the KT-120s are direct interchanges for the KT-88 and 6550 tubes, at least in my application. But that doesn't mean those smaller tubes might sound as good as a KT-120, which is also capable of higher output depending on the circuit. (The KT-120s are not at all stressed in my amp, maybe at about 60% of full capacity, so they'll have a long life...and I have a spare set as well.)

Being older designs, though, the 6550, KT-88 and their equivalents were made decades ago, so those are still available as new old stock.
 
The world tube situation hasn't changed and if anything, some tubes have gotten harder to find and more expensive. Upscale Audio no longer sells KT120s except to current customers of their Prima Luna amps. There are still KT120s out there at other sellers but the price has gone up 50% or more from what it used to be. Thankfully my newer quad set in the amps is doing well, and my older set had nothing wrong with them, so I'm glad to have them as spares. As they are only made by New Sensor (in Russia) under the Tung-Sol brand, there is no other source for them.

For the more common output tubes like EL34, EL84, KT88/6550, there are still supplies of new old stock tubes out there, and the small signal tubes (5751, 12AX7, 12AU7, 6DJ8, etc.) likewise are easy to find as new old stock or even new production as the supplies are not quite as limited.

I do get concerned about the M8080/CV4058 tube used in my preamp though. The only reliable tube I've used is the CV4058 from Mullard in the UK, which was a military tube. It is electrically equivalent to the 6C4. It arrived with Phillips/ECG 6C4s, and I had ordered Tung-Sol 6C4s to try (they weren't too expensive), but both were microphonic. (If you turned the volume up, you could hear the grids "ringing" inside the tubes, through the speakers.) Only the Mullard is rugged enough. The only reliable seller I've found is in the UK and he sells matched pairs of the Mullards.

I had considered having my amp modified when I had it in for repair--the KT120 tubes can output more power than what they are getting through my amp. But that would not only make my amp non-standard, it would also shorten the life of the tubes. They live an easy life. And at best, I could only less than double the output power of the amp, and that would be less than a 3dB increase, barely noticeable.
 
Well, I've made a decision on the Chi-fi tube amp I bought three years ago. I was going to sell it off cheap since I did not like the sound of it--way too dull. I poked around and found modifications online for the model A12--mine is an A10, but the only difference is they wired the input tubes in the A12 to use 12AX7 or equivalent, vs. the odd Russian tube they spec'd. There are socket adapters that will switch from the original tube socket to 12AX7 compatible, but since I bought the point-to-point wired version of the amp, I can simply go in and change the wiring myself.

The modification I found is by Skunkie Designs, and changes many of the values. The side benefit is that the no-name Chinese capacitors are dumped in favor of a name brand--I would go with Nichicon or Panasonic. For the metal film resistors, I'd be replacing with Vishay/Dale. The bill of materials for the modification lists the parts in the modification, but there are only six or seven more components beyond that which would completely swap out all the Chinese parts.

One thing I noticed in the modification is that the input side is only using one side of the 12AX7, where the original uses both sides.

The person who designed the modification hooked the amp up to a scope and found the stock measurements were lacking quite a bit; the response graph of the stock unit corresponds with what I was hearing. Tube circuits are really simple, so it doesn't take much to make changes to the circuit. I can get away with about $40 in parts to do the upgrade.

The only drawback is that it is a low-powered amp, and I really don't have a use for it. I think it can muster up about 6 watts per channel. It is an EL45 amp and would be running in single-ended mode (not push/pull). It will still be an interesting project though.
 
Inside the amp. I'll probably order the parts later in the year when my travel schedule dies down.

PXL_20230920_024044756.jpg

PXL_20230920_024010970.jpg

I should also round up some parts for the Grundig radio and RCA 45-EY-3, as those also need attention. With shipping costing what it does, ordering everything at once will save a few bucks. These parts are not expensive, even going with better options (like Nichicon capacitors, thin film resistors, etc.).
 
C-J Premier 11 here, with a PV14L preamp and EV1 phono stage. Got hooked on the C-J sound. 😊 I found the Premier 11 on our local Craigslist, of all places--I think it was in Livonia or Westland. Seller ended up needing to pay some dental bills and it sat on CL at a low price for months. (Knowing the flippers around here, he probably got offered a small percentage of what it was worth.)

I wasn't sure how the 11 would work with stats in terms of power but since they are more efficient than the Vandersteen 2CEs, they play louder than I can handle it. I replaced the tired stock GE 6550s with the Tung-Sol KT120s and along with the other new tubes, it really brought the amp to life. (It was a bit dull and lifeless, but was on the original tubes after decades.) I got all of those tubes from Uncle Kevvy myself--don't we all, at some point? 😁

BTW, are you over at AudioKarma or HiFi Haven?
I'm thinking of selling my PV5, which was modded by Bill Thalmann, who designed it. Amperex foil D-getter 12ax7's in the phono stage and GE 5 star 5751's metal clip and other stuff. Do you know anyone who might be interested?
 
I'm thinking of selling my PV5, which was modded by Bill Thalmann, who designed it. Amperex foil D-getter 12ax7's in the phono stage and GE 5 star 5751's metal clip and other stuff. Do you know anyone who might be interested?
I would check the HiFi Shark site for the PV5, but search for sold/expired listings to see what they are currently selling for. It would probably move at the right price on US Audio Mart (or Canuck Audio Mart if you're in Canada). It might not hurt to see if you can list it on the conradjohnsonowners.com site as well--it is lower traffic but occasionally someone is looking for an older piece.

Bill got my Premier 11 fixed, and added a couple of mods for me. I had him replace the damaged power cord with an IEC inlet, and upgraded it from an 11 to an 11A. (That was a small modification to the driver circuit for the biasing LEDs which caused some faint noise.)

BTW, there's a listing right now for a rare pair of Premier 140 monoblocks. Jeff @ C-J thinks they are the only pair they ever made. They weren't a 140 bridged to mono, but built specifically as monoblocks. So, about 280 watts each. Sure I'd love the set, but that's not the kind of disposable cash anyone has laying around these days. 😁 Plus, running those two amps would put a big dent in the utility bill. As would retubing the amps when it was time, especially with the supply of new tubes still questionable.
 
I am currently have an Audio Research SP3a1 fully restored to original specs and my PV5 has been sitting dormant because it doesn't mesh well with my McIntosh MC30's and modded La Scalas. The CJ was sublime with my Pass X250's and Peter Gunn Maggies, but the midrange "bloom" that was voiced into this preamp is more accentuated with my current system.
Bill also put an IEC connect on mine which is a nice benefit to have power cord options. It's too bad that Bill had to close shop.
I just posted on the CJ site you mentioned. Thanks for the info!
At my age I would rather it find a good home rather than being poached at an estate sale when I'm too feeble to protest!
 
It looks like Bill is still doing repairs as Thalmann Audio Inc., but they have shuttered the building. Which is good, as I wouldn't trust anyone other than Bill or another former C-J employee to work on my equipment. I'd gotten an estimate from C-J to work on my amp, but they were instead pushing me to do the Teflon capacitor upgrade, which would have cost me more than what I paid for the amp.

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I can't believe that they sent my piece back six months ago saying that Bill wasn't doing any more work.
Those m-fr's. That really gets under my skin after being in a 6 month queue after sending my preamp to MT.
 
I can't believe that they sent my piece back six months ago saying that Bill wasn't doing any more work.
Those m-fr's. That really gets under my skin after being in a 6 month queue after sending my preamp to MT.
I haven't contacted anyone--the site could be outdated.
 
I haven't contacted anyone--the site could be outdated.
This all happened pretty recently, but Bill told me to send it in even though his health wasn't so good and he was going to call it quits after September of 2022. I told him it was ok if he took me out of queue because his health is more important. He thanked me and said that it wasn't a problem. Then one of the people a at Music Technology told me that my piece was being sent back because they were closing and needed to clear out the shop of any gear that hadn't been worked on and provided no explanation. They told me to contact Bill but I didn't receive a reply from him. I was under the assumption that he wasn't doing well and found another person to work on my Audio Research SP3a1. All of this transpired within the last year.
I have the utmost respect for Bill and his work ethic and heard other people say that he was still doing work, but I can't say either way. That being said I would rather his health was good and my piece was an oversight or MT's way to disconnect from Bill's pending workload.
I was, however, irritated that his assistant wanted me to pay for return shipping, and had no intention to reimburse me for the cost of shipping the unit to them. Just downright unprofessional, and I couldn't imagine Bill doing something like that.
Still think he's a great guy and give him the benefit of the doubt, albeit, MT will never get any business from me, and doubt they care because they probably have more than enough work without it, even if Bill is retired.
All things must pass.
 
I saw your post on vintage Fisher gear. I restored a 500C that I got for free some years ago with a $100 restoration kit. Looked like it was dredged from the bottom of a lake. It ended up performing better than a Fisher Doc restored one that I sold soon thereafter. I replaced the output tubes with JJ 7591's and one of them shorted and fried the 5W plate resistor. I have major league neuropathy in my fingers from arthritis so I can't even tie my shoes properly, but I might get motivated to replace it one day! Really nice sounding receiver, but they ran hot.
A real sleeper in vintage tube amps is the Bogen DB-20. I restored a pair of them and they still sound great, and quiet as a church mouse. Give them the edge over the Eico HF-20's.
Can I post pictures from my computer to this site? Doesn't want to let me load them directly from my hard drive.
 
Still think he's a great guy and give him the benefit of the doubt, albeit, MT will never get any business from me, and doubt they care because they probably have more than enough work without it, even if Bill is retired.
The entire shop shut down in mid 2023, and I just found out today that Bill passed away back on January 24 this year from pneumonia, and was diagnosed with Parkinson's in 2018.

There's a nice career overview and tribute on the Music Technology site:

 
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