Driver Rca
Building an almost RCA OP6 Mic Preampimage sourceThe RCA OP 6 Portable Amplifier is one of a handful of truly visually iconic vintage mic preamps. The OP 6 was designed as a remote, as in, on location single channel mic preamp for radio station broadcasts. It uses three 1. J7 tubes most mic pre designs of the period use two. Furthermore, the 1. All Driver Pack For Windows 7. The result a ton of gain. MrxC2cKyD8o/Tz9A8YMtRpI/AAAAAAAABVI/PGLLREsEE68/s1600/pair%2Bright%2Bside.jpg' alt='Mt65xx Preloader Driver Rca Tablet' title='Mt65xx Preloader Driver Rca Tablet' />This is almost twice as much gain as the classic RCA BA1 and BA2 mic pres. OP 6s are in high demand click here for a seller asking 2. Further indication Blackbird Rentals in Nashville has thirteen in stock as rental units. The first time I heard an OP 6 in use was at Blackbird I was producingdirecting a live in the studio performance for Martina Mc. Bride and John Mc. Bride was engineering he was using the OP 6 for something I cant remember what exactly. Anyway, it caught my eye and we talked about it a bit later I learned that he has an especially strong appreciation for these units. A strong endorsement coming from the man who likely owns more vintage pro audio gear than anyone who ever has or ever will live. The OP 6 schematic is pictured above this file is readily available in high res on the internet. So anyhow, if we consider how in demand the OP 6 is, it seems striking that no one offers a modern equivalent for sale, even on a small scale level. If you take a close look at the circuit, the reasons become apparent. There are two big obstacles to re creating even a semblance of an OP 6. First is the input attenuator Sure, its a voltage divider probably constant impedance but what exactly are the values And what about that value of that feedback path issuing from the attenuator back to the input stage If I could get my hands on an original OP 6 and open up the attenuator, sure I could maybe sort it out. But I imagine that re creating that part on custom order could cost hundreds of dollars frankly I have no idea. The second obstacle to re creating the OP 6 is the output stage choke. The choke is designated L 1 in the schematic. Curiously enough, its actually physically part of the output transformer. Based on this fact, there is zero chance that this was an off the shelf choke, say a UTC for example, that we could track down. OK but the crucial value of a choke in a circuit like this is the inductance. So long as the voltage an current handling values are sufficient, any choke of same inductance should give a similar result. Now again, if I had an original OP 6, I could measure the inductance and maybe a current off the shelf part exists to satisfy the requirements. But I dont think anyone out there is gonna send me their prized OP 6 to open up. And 2. RD cost. So what do we do Well, in the absence of any actual electrical engineering training, I looked for some good advice and then I guessed. Classic/speakers/rca-mi-9584-a-driver-speakers-horns-pair-org/rca-mi-9584-a-driver-speakers-horn-5.jpg' alt='Driver Rca' title='Driver Rca' />The very friendlytalented John Atwood sent me the diagram above in response to what I cant recall. This diagram explains why the choke is necessary in order to get the best possible performance from a single ended vacuum tube line output stage. Looks pretty similar to our OP 6 output stage, right Based on this I made a wild guess. I ordered the very inexpensive Hammond 1. C choke. 1. 50mh inductance with 8ma current capacity. I have found that Hammond really undersells the specs of their transformers, so Im not worried. Alright so now weve got a choke that might work. What about that input attenuator The best course of action would probably be to get a used 1. Driver Rca W101' title='Driver Rca W101' />Daven T pad, but without implementing the feedback path that the stock OP 6 attenuator has, it seems like this is slightly pointless vis a vis maintaining originality. So instead I used the input stage from my favorite, yes yet again, the RCA BA 2. The BA 2 schematic is pictured above. The input stage uses a 1. So I just took this input stage, up to the pot output, and wired it in front of the second two OP 6 stages starting at the grid of stage 2. When I did this, the whole system worked fine except when the volume pot was a zero IE., when the grid of tube 2 is shorted to ground. This caused weird noise and a little humming. Not sure if this is due to the negative feedback in that stage, or if this is simply a general characteristic of 1. The easy solution I added a 1. M resistor from the grid to ground, and isolated this from the pot with a 1. K grid stopper resistor. Done and done. The BA2OP6 Hybrid is born. The finished piece is shown above. I used a 6. X5 rectifier tube like the OP 6 uses in fact, with the exception of using DC filament voltage, I kept the power supply the same as the OP 6. The audio portion of the circuit is shown above. What with the three pentode stages and feedback paths, this is extremely complicated for a mic preamp. A lot of parts. On the left you can see my usual Jensen 1. Audio caps are a mix of Solen, sprague, and some random Russian ones. Basically whatever would fit. Resistors are random as well now that I have confirmed that the piece works well, I will probably replace the carbon comp resistors in the B chain with some quieter modern resistors. On the right is the output transformer. I used an edcor 1. K 6. 00 1. 0. 2. Even though this edcor is unshielded, there is zero hum following the volume pot. And as for performance I did a frequency sweep through the entire unit response is absolutely flat from 1. At 1. 0k there is a rise of about 1db up to 2. This is really excellent performance considering the inexpensive transformers. I did not measure the gain but there is a lot of. The output level can get extremely hot. Anyhow. Thats it for now. As soon as I have a minute I will provide some audio test examples Ill post some AB examples of this unit versus an API 5. Thanks to DW at EMRR for helpful suggestions regarding this project. UPDATE Listening test has been done and results are posted here. RCA 6. AS7. G Vintage Tube Tube Socket. Very Good Upgrade over stock Chinese tubes. Replaced the power tube on my Dark. Voice 3. 36. SE headphone amp with this tube. It sounds a lot sweeter, fuller, better mid range and a wider soundstage. The bass is not quite as fast as the stock Chinese tube, but it sounds fatter and rounder. Overall, this tube is far more musical and will not cause listener fatigue. Verified purchase Yes. Extron Electronics is a leading manufacturer of computervideo interfaces, switchers, distribution amplifiers, computervideo scan converters, line doublers. With very few exceptions like RCAsee below, the proponents of original pressings have provided absolutely no supporting scientific or technological explanations. Preview The Gallery Guide, in print and online, lists current visual art exhibitions in galleries and museums in Calgary, Edmonton, Portland, Seattle, Vancouver and.