Hello, I was wanting to know if anyone can Identify these vintage tube monoblock amplifiers - they use 6973 , 7199, and 5u4 Tubes ..... Thanks!
I'm not sure if it's still the same as original or been modified inside the chass ..
I'm not sure if it's still the same as original or been modified inside the chass ..
Look to be DIY monoblocks, probably using something close to the RCA schematic.
compare to page 10: http://www.tubebooks.org/file_downloads/RCA_HiFi.pdf
compare to page 10: http://www.tubebooks.org/file_downloads/RCA_HiFi.pdf
Hi, there are two different sets of them from different people on estay..... so seems like not a diy .... reconditioned but both of them same ... in different stages of repair... plus i have see a couple of older threads, asking question on similar amplifiers --- so I don't know .....
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Looks custom (DIY) to me. Factory will use rivets. Kits or dyi usually use screws. To me, the design has a Pilot kinda vibe.
those look like Dynaco MKIII transformers?
It sure looks like a custom/DIY job or perhaps a variation of the Dynaco MKIII. Also looks like a DC regulated supply, could be for driver B+ or even perhaps DC filaments for the driver tubes.
It sure looks like a custom/DIY job or perhaps a variation of the Dynaco MKIII. Also looks like a DC regulated supply, could be for driver B+ or even perhaps DC filaments for the driver tubes.
Hi carlthess40 , they are for sale on -- estay - ( so here's a question, why don't people call that selling place by it's name ... is it advertising for them or something? - 🙂 ) - by the way they are selling for $ 793.00 + 93.00 shipping .
- I was interested in them because the transformers looked impressive for the size of the amplifier -- and was surprised there wasn't a name on them- so I was trying to learn what I could about them....
- I did see that someone changed another vintage amplifier , an Ampex Amplifier from using that same 6973 vacuum tube to 6bQ5 tubes.
- picture below - ( $ 949.00 )
- I was interested in them because the transformers looked impressive for the size of the amplifier -- and was surprised there wasn't a name on them- so I was trying to learn what I could about them....
- I did see that someone changed another vintage amplifier , an Ampex Amplifier from using that same 6973 vacuum tube to 6bQ5 tubes.
- picture below - ( $ 949.00 )
Hi carlthess40 , I did some checking around about the tubes in that 50 watt amplifier -- (I'm the newbie so anyone feel free to set things straight if they get too off base ) - anyway - it looks like the 50 Watt - 7027 amplifier you were looking at is really basically a 6L6 tube amp. The article I read said that they renamed those 7027 tubes to make them look different and be competitive during wattage wars that were going on back then. - does that sound right -- anyone?
When push comes to shove, the 7027A equates to a 6L6GC. A good case can be made for the 7581A being the "mightiest" 6L6 family member, ever.
IMO, if somebody wants to get approx. 50 WPC from a PP pair of 6L6 family tubes, the H/K Cit. 5 is the place to start. The H/K Cit. 5 is a superior implementation of "classic" Mullard style topology. Attention is called to the selection of high gm types for the small signal positions.
IMO, if somebody wants to get approx. 50 WPC from a PP pair of 6L6 family tubes, the H/K Cit. 5 is the place to start. The H/K Cit. 5 is a superior implementation of "classic" Mullard style topology. Attention is called to the selection of high gm types for the small signal positions.
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The original 6L6, 6L6GA, 6L6GB, 807, and 6BG6 were all very similar and had a plate structure with minimal fin or wing structure. Plate dissipation ratings varied from 19 to 24 watts.
The 6BD5GT is also a 6L6 stuffed into a 6V6 size bottle for TV sweep use. Due to the close proximity of the glass and the plate, they are rated for 10 watts plate dissipation.
The 6L6GC was similar, but the plates had extra metal where the two halves were joined creating heat radiating fins, or wings. The maximum plate dissipation spec was increased due to these wings. Again ratings vary from 26 to 30 watts. The screen grid voltage and power ratings were increased due to "design improvements."
The RCA 7027 (not 7027A) was indeed a 6L6GC in a slightly fatter bottle.
The RCA 7027A was different due to even larger fins, allowed by the bigger bottle. It has a 35 watt plate dissipation rating. It appears that the 7581A was GE's answer to the RCA 7027A, but I have not used them and can't really say.
It is important to note that the methods for determining and specifying the maximum plate dissipation rating changed a few times in the 40+ years that the 6L6 types were in production. The biggest was the change from "design center" ratings, to "design maximum" ratings. This brought about a 10% boost in ratings with NO changes in the tubes.
It should also be noted that several manufacturers "stuffed the glass" with whatever guts they had as tube manufacturing was declining and production lines were being shut down. Sylvania was the biggest player in this game. I have seen 6L6GB's, 6L6GC's 6BG6GA's and even 807's with 7027 or 7027A guts inside them.
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"I’d like to find someone to build that 50 watt mode on page 15 from that link Kstagger posted" no problem, if you have enough cash, there's a good few hours in that not to mention the price of the components. That design will need some alterations too, in order to use different valves to the the less common types like the 7199 triode/pentode. From a quick look there looks to be several less than optimal parts of the circuit like the g2's on the 6CB6's for instance.
Andy.
Andy.
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