Packard Bell DPA30 vs DPA20?

[Twmangrove]

Hi there kind folks: This may be off topic slightly but not sure where else to go. There is a P-B stereophonic unit for sale locally: The description and label say it is an rpc-30, a partial label says amp is a DPA- (the rest is missing). It comes with the separate speaker SAC-3. The knobs have a cool atomic symbol on them. I can find very little information but I believe it is from about 1959. I'm wondering if this is a good unit and whether it may be worth 400 bucks. Any help is much appreciated.

 

[biscuithead]

Hi there kind folks: This may be off topic slightly but not sure where else to go. There is a P-B stereophonic unit for sale locally: The description and label say it is an rpc-30, a partial label says amp is a DPA- (the rest is missing). It comes with the separate speaker SAC-3. The knobs have a cool atomic symbol on them. I can find very little information but I believe it is from about 1959. I'm wondering if this is a good unit and whether it may be worth 400 bucks. Any help is much appreciated.

400 is a lot. If it has two amps though and if it is mint... maybe. Questions of value should be posted in dollars and sense. Buy it if YOU value it at that much

 

[FlaCharlie]

I like this evidence-less, speculation of marketing nefariousness, snake oil suspicion...
I think that the truth is a moving target on this one. Perhaps the proof is in the pudding, but like so much in audio, proof and opinion are blended together in taste.

I don't claim that he was trying to outright scam anyone but he certainly knows how to, let's say, use people's natural gullibility to his advantage.

The explanation of how he came to the conclusion that Stu Hegeman designed the output transformer or maybe even the amp, is hilarious. I have to wonder if he actually believes it or if it was written tongue in cheek and nobody called him on it because, well, he's a well known figure in the audio world. It's totally far-fetched yet impossible to disprove. A prime example of creative marketing perfection.

One thing that keeps creeping into my tiny little sleuthing mind though... is why would a prominent and wealthy audio engineer of famed status stoop to "huckster" levels for a thousand bucks?

Neither one of us, I assume, has any knowledge of his financial condition. The auction is from July 2012, towards the end of the Great Recession. I learned long ago that fame and financial health are not necessarily linked, even though most people assume they are. No matter how much money you've made, you can always spend more than you have. Lots of people whose lifestyle says "wealthy" are actually up to their eyeballs in debt.

I admit that I have not measured distortion of either of my Dpa-20 or Dpa-30, but mostly because I don't expect to get better metrics than a similar Maggie or any other console amp.

That would be my expectation too. As I said, it would be interesting if someone could do a comparison. Perhaps the Maggie or other console's transformers measure just as good. He says the zener mod reduces the distortion when the amp is "driven close to its maximum output". I don't doubt that to be true. The question is, in normal use, if you never push it that hard does it have any meaningful effect? And, while it may be measurable on a scope, can you actually hear it?

I know that I'd rather play with these instead of any of the 300-400 dollar tube amps being slapped together overseas and being touted as high quality online.

I agree with that 1000%!

The pics of in guts do surprise me. I suppose it's possible that all those original parts measure fine, but based on my own experience, I'm skeptical. His claim that the screen voltage has some type of voltage regulation applied to it is the most dubious claim. If anyone can point out any modifications in the pic that show that, please point them out. Perhaps I don't know what to look for. I've never built anything with regulated voltage.

I'm surprised he didn't at least replace the coupling caps. He could have thrown in some generic caps with his name printed on them. "Custom made coupling caps made to Bob Carver's personal specifications" would have easily added another $400 to the final price!

Question Carvers claims? Sure, just like today's specs and measuring techniques. Is advertising a dark art ? Yep. And audio is realm of grey area opinions and colorful terminology. It's great!

It's endlessly entertaining.

 

[biscuithead]

I had to look up Carvers net worth... which led me to a possible Emotiva buyout in 2012, then this article:

https://www.stereophile.com/content/jade-design-acquires-bob-carver-llc

Interesting

 

[gadget73]

Kinda makes me want to get one at a reasonable price and actually see what it can do both stock and modified.

5.5K is a bit low for typical EL84 load, but with 8 ohms it ends up at 11k which is high. Sounds like a nice match for some 6 ohm speakers to me. That would give a PI of 8.2k which is right nice.


Are there any numbers on the stock transformers? EIA might reveal the maker. I'm sure you're right that PB did not wind their own.

 

[FlaCharlie]

I had to look up Carvers net worth... which led me to a possible Emotiva buyout in 2012, then this article:

https://www.stereophile.com/content/jade-design-acquires-bob-carver-llc

Interesting

Yes, very interesting. This announcement was made about a year after the auctions for his modded Packard-Bells. It would seem to indicate that Carver was in financial trouble at the time.

High dollar amp sales were likely down for years due to the recession. The price drops on the amps after the sale are huge, not minor adjustments. You don't do that if things are going well. It also illustrates just how overpriced gear like this is. The amps are still grossly overpriced, IMO. But, hey, if buyers are willing to pay silly prices for the privilege of having Carver's name on the amp, that's their choice. There are lots of "high end" audio products out there that are even more grossly overpriced (again IMO), I'm sure. I'll stick with relatively cheap vintage junk and DIY, thank you.

 

[FlaCharlie]

Kinda makes me want to get one at a reasonable price and actually see what it can do both stock and modified.

5.5K is a bit low for typical EL84 load, but with 8 ohms it ends up at 11k which is high. Sounds like a nice match for some 6 ohm speakers to me. That would give a PI of 8.2k which is right nice.

Are there any numbers on the stock transformers? EIA might reveal the maker. I'm sure you're right that PB did not wind their own.

Yeah, the primary rating struck me as odd too. If the OT was designed by Stu Hegeman it seems he either didn't bother to read the tube data sheet or he disagreed with it for some reason. I wonder if the OTs of amps that he is known to have designed are that much different from their expected primary impedance.

They were probably just an off the shelf part that was workable, though not ideal on paper, and that the manufacturer was the low bidder for the contract. People often attribute parts choices to exhaustive research conducted by engineering departments when, in reality, it was the bean counters who had the final say in many cases. That scenario seems much more likely, given that this was a fairly modest console, than Carver's far-fetched theory that they hired a well known designer to engineer it from scratch.

There are no EIA numbers, only a number stamped in ink on the top of the transformer. It corresponds to the stock number listed in the Sams for a manufacturer called Ram, which I've never heard of before. Here's what I found about the current Ram Transformer company. As I said, it may be that they were re-organized in 1995 after a period of inactivity and that they have some historical connection to the earlier company that supplied the Packard-Bell OTs.

 

[Dswankey]

Interestingly enough there is someone selling a pair on eBay touting Bob Carver, Stu Hegman and the Silver Sevens

https://www.ebay.com/itm/PAIR-2-of-...757584?hash=item4d7a34b9d0:g:WqcAAOSw4klbZ38Z

 

[gadget73]

I really wonder if Stu Hegman had anything to do with this, or if its just marketing wank just to make some more $$.

 

[biscuithead]

Interestingly enough there is someone selling a pair on eBay touting Bob Carver, Stu Hegman and the Silver Sevens

https://www.ebay.com/itm/PAIR-2-of-...757584?hash=item4d7a34b9d0:g:WqcAAOSw4klbZ38Z

Hmm

They are in BT also...

 

[biscuithead]

Hmm

 

[FlaCharlie]

5.5K is a bit low for typical EL84 load, but with 8 ohms it ends up at 11k which is high. Sounds like a nice match for some 6 ohm speakers to me. That would give a PI of 8.2k which is right nice.

Are there any numbers on the stock transformers? EIA might reveal the maker. I'm sure you're right that PB did not wind their own.

OK, I was wrong when I said earlier that there are no numbers on the OTs other than the ones stamped on them in ink. First, the part numbers listed in the Sams are: Packard-Bell 89460A and Ram AU-609 is listed as a replacement.

I looked at my amp. Its ink stamp is 909 and there are two lines of numbers:
89460A (same as the one listed in the Sams)
394932

I saw one auction with numbers clearly visible but no ink stamp. The numbers are:
89532
3946118

Perhaps @biscuithead will tell us the numbers on the two amps he is apparently selling. I can see that they have numbers but I can't read them. The ink stamps on his are 903 and 907.

My current speculation is that the EIA code is the first 3 digits of the second line, which are both 394 above. This was a code used by the Foster Transformer Company, which is still in business and has been in operation since 1937, according to their website.

I'm guessing that the numbers stamped in ink are quality control numbers associated with different QC inspectors, especially since the same number appears on the top surface of the can cap on these amps.

On the OTs on the amps sold by Carver there are no visible numbers because the metal frames have been painted with black paint.

So, perhaps there is not a single model of transformer that was used in these amps. Maybe Packard-Bell just bought whatever similar transformers that Foster had in stock at the moment.

Continuing the search . . . I also found pics of one of these on a guitar amp site. The poster wanted to convert it for guitar use and others were walking him thorough the process of checking the transformers. These OTs had 311 in ink and:
89532
- 606 - 3 - 40

They measured this version and found it had a 31.5 : 1 turns ratio
8k : 8 ohms

I saw yet another pic of one with no ink stamp and:
89532
- 606 - 3 - 30

The EIA code 606 was for another transformer manufacturer, Woodward - Schumacher.

So, it seems P-B used a lot of different OTs, made by at least two manufacturers. As I said earlier, they probably just bought batches of whichever OTs they could get the best deal on. It's highly doubtful there was anything magical about any of them, just normal, off the shelf, parts available at the time.

 

[biscuithead]

OK, I was wrong when I said earlier that there are no numbers on the OTs other than the ones stamped on them in ink. First, the part numbers listed in the Sams are: Packard-Bell 89460A and Ram AU-609 is listed as a replacement.

I looked at my amp. Its ink stamp is 909 and there are two lines of numbers:
89460A (same as the one listed in the Sams)
394932

I saw one auction with numbers clearly visible but no ink stamp. The numbers are:
89532
3946118

Perhaps @biscuithead will tell us the numbers on the two amps he is apparently selling. I can see that they have numbers but I can't read them. The ink stamps on his are 903 and 907.

My current speculation is that the EIA code is the first 3 digits of the second line, which are both 394 above. This was a code used by the Foster Transformer Company, which is still in business and has been in operation since 1937, according to their website.

I'm guessing that the numbers stamped in ink are quality control numbers associated with different QC inspectors, especially since the same number appears on the top surface of the can cap on these amps.

On the OTs on the amps sold by Carver there are no visible numbers because the metal frames have been painted with black paint.

So, perhaps there is not a single model of transformer that was used in these amps. Maybe Packard-Bell just bought whatever similar transformers that Foster had in stock at the moment.

Continuing the search . . . I also found pics of one of these on a guitar amp site. The poster wanted to convert it for guitar use and others were walking him thorough the process of checking the transformers. These OTs had 311 in ink and:
89532
- 606 - 3 - 40

They measured this version and found it had a 31.5 : 1 turns ratio
8k : 8 ohms

I saw yet another pic of one with no ink stamp and:
89532
- 606 - 3 - 30

The EIA code 606 was for another transformer manufacturer, Woodward - Schumacher.

So, it seems P-B used a lot of different OTs, made by at least two manufacturers. As I said earlier, they probably just bought batches of whichever OTs they could get the best deal on. It's highly doubtful there was anything magical about any of them, just normal, off the shelf, parts available at the time.

Ok... you made me get off my butt and snap some pics of what I could get to easily.

DPA20 (A) - 89460a, 394909

DPA20 (b) - 89460a, 394901

DPA30 -89532, 3946136.

I actually have never looked very close at these... my three have the 394 similarities.

 

[biscuithead]

OK, I was wrong when I said earlier that there are no numbers on the OTs other than the ones stamped on them in ink. First, the part numbers listed in the Sams are: Packard-Bell 89460A and Ram AU-609 is listed as a replacement.

I looked at my amp. Its ink stamp is 909 and there are two lines of numbers:
89460A (same as the one listed in the Sams)
394932

I saw one auction with numbers clearly visible but no ink stamp. The numbers are:
89532
3946118

Perhaps @biscuithead will tell us the numbers on the two amps he is apparently selling. I can see that they have numbers but I can't read them. The ink stamps on his are 903 and 907.

My current speculation is that the EIA code is the first 3 digits of the second line, which are both 394 above. This was a code used by the Foster Transformer Company, which is still in business and has been in operation since 1937, according to their website.

I'm guessing that the numbers stamped in ink are quality control numbers associated with different QC inspectors, especially since the same number appears on the top surface of the can cap on these amps.

On the OTs on the amps sold by Carver there are no visible numbers because the metal frames have been painted with black paint.

So, perhaps there is not a single model of transformer that was used in these amps. Maybe Packard-Bell just bought whatever similar transformers that Foster had in stock at the moment.

Continuing the search . . . I also found pics of one of these on a guitar amp site. The poster wanted to convert it for guitar use and others were walking him thorough the process of checking the transformers. These OTs had 311 in ink and:
89532
- 606 - 3 - 40

They measured this version and found it had a 31.5 : 1 turns ratio
8k : 8 ohms

I saw yet another pic of one with no ink stamp and:
89532
- 606 - 3 - 30

The EIA code 606 was for another transformer manufacturer, Woodward - Schumacher.

So, it seems P-B used a lot of different OTs, made by at least two manufacturers. As I said earlier, they probably just bought batches of whichever OTs they could get the best deal on. It's highly doubtful there was anything magical about any of them, just normal, off the shelf, parts available at the time.

I am now researching Foster Transformer co. To see if Stu was on the roster at Foster

 

[gadget73]

So, it seems P-B used a lot of different OTs, made by at least two manufacturers.

Magnavox did this too. Found that out by way of Dave G's thread on the 9300, another member had one that had different mfg transformers than Dave's did. I rebuilt one for someone that had the same different transformers. They perform somewhat differently too. I had to fiddle with the HF tuning to make it come out right.

 

[biscuithead]

Magnavox did this too. Found that out by way of Dave G's thread on the 9300, another member had one that had different mfg transformers than Dave's did. I rebuilt one for someone that had the same different transformers. They perform somewhat differently too. I had to fiddle with the HF tuning to make it come out right.

Isn't it reasonable to conclude that if a manufacturer doesn't build a component in-house, then it is likely to "bid out" a spec version to different companies?
Didn't Dynaco, Altec, Heathkit, Stromberg, etc ... all have different transformer suppliers throughout their tenure as "manufacturers" ?

They just didn't have Bob Carver touting their magic.

 

[gadget73]

I'd expect thats how it is done, its the usual way of buying stuff at least.

 

[FlaCharlie]

I really wonder if Stu Hegman had anything to do with this, or if its just marketing wank just to make some more $$.

Well, here's another bit of info. According the Bob Carver's "source", the young apprentice who briefly worked at Packard-Bell, the visiting consultant was an "old man". The date on the Sams for this console is April 1960 so it was probably a 1959 model, and the amp itself may have been designed even earlier. In 1959, Stu Hegeman was only 46. He died in 1986 at age 72. Would a young apprentice, maybe 18 or 20 himself, describe a 46 year-old as an "old man". I doubt it.

 

[biscuithead]

Well, here's another bit of info. According the Bob Carver's "source", the young apprentice who briefly worked at Packard-Bell, the visiting consultant was an "old man". The date on the Sams for this console is April 1960 so it was probably a 1959 model, and the amp itself may have been designed even earlier. In 1959, Stu Hegeman was only 46. He died in 1986 at age 72. Would a young apprentice, maybe 18 or 20 himself, describe a 46 year-old as an "old man". I doubt it.

Let's just pretend that Stu Hegeman did design this great little amp... so what.

Now let's pretend that we've dispelled the myth that Stu was involved with the design... so what.

I'm not trying to be rude or antagonistic...
but can we agree that it is a better than average design for the time, on par with the likes of the late 50s Maggie's ?

I know we all had suspicions that Carvers story was a marketing "stretch"... but this thread started out as "difference between the dpa20 vs the Dpa 30" . Now I've helped derail it into a rabbit hole, and I'd rather not let it develope into a "Carver smear campaign " .
I say this with magnanimous yet culpable and cheery guilt/intent.

 

[gadget73]

Its probably a better design than the Magnavox if we're being honest about it, but mostly its because of the phase inverter. Fisher, Scott, Dynaco, and probably a laundry list of others ran a split load design like this. There are only so many ways to cost-effectively build a push-pull amp so the fact that this amp shares design traits with some more high brow equipment doesn't really mean a whole bunch.