DCAudioDIY.com

DC Area Audio DIYer's Community
It is currently March 28th, 2024, 6:15 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 37 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
PostPosted: October 12th, 2017, 4:47 pm 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Roscoe,

Something looks strange regarding your voltages, looks like you have 180V across the tube (Plate to cathode), and 18V (grid to cathode) of bias. At that op point, the current is over 60 mA according to the plate curves, but your cathode resistor size is sized for 35 mA. I would expect a bias voltage closer to 28V, not 18V if the tube was operating in spec.

No matter really, the cathode resistor size is going to keep the current down, and the voltage is low, so you are not pushing the tube at all.

David

Roscoe Primrose wrote:
I was using 5AR4/GZ34 rectifiers, which heat up more slowly that the 45. AC heated, direct coupled...

http://n4rp.com/images/5842-45.pdf

Roscoe


Top
 Profile  
 
PostPosted: October 12th, 2017, 4:56 pm 
Offline

Joined: April 22nd, 2013, 12:58 pm
Posts: 285
Cogito wrote:
Why do you say that?


Because the basic architecture of this circuit is both very ordinary and very old.
To say that Pass adapted a Rosenblit circuit implies a lack of creativity on the part of Nelson Pass.

The devil is in the details, as both Rosenblit and Pass know very well. The hard work that went into making each of the respective amps work as well as they do, given the inherent deficiencies of both the architecture and the devices, was considerable. They both faced different challenges because of the different devices they used, and the subtle design details they employed that mitigate or remediate those challenges are very different.


Top
 Profile  
 
PostPosted: October 12th, 2017, 5:07 pm 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
I am not sure my reply ever posted but I would like to point out that just because you take output from the source or cathode does not mean the topology is the same. Remember, there are no complementary pairs of tubes, whereas the Pass F4 uses NPN/PNP Mosfets in a source follower. Rosenblit's design is a Circlotron, right?. Completely different animals. There is no patent on which way you take output on a device, just because the connections look the same at a high level doesn't mean the circuits are the same or even similar in operation. The difference is in the details, not the superficial similarities.

David


Top
 Profile  
 
PostPosted: October 12th, 2017, 5:33 pm 
Offline

Joined: April 22nd, 2013, 12:58 pm
Posts: 285
I concur David,

Let's get back to talking about 45 SETs........
They are much more my cup of tea, even though I have never owned a set of speakers that are compatible.
Did you bring your 45 amp to Roscoe's once? This is back when he had the big bass horns. I seem to remember listening to them and comparing to Roscoe's 2A3 amps. Towards the end he put in some monoplate RCA 2A3's and I heard first hand why people pay silly prices for them.

David McGown wrote:
I am not sure my reply ever posted but I would like to point out that just because you take output from the source or cathode does not mean the topology is the same. Remember, there are no complementary pairs of tubes, whereas the Pass F4 uses NPN/PNP Mosfets in a source follower. Rosenblit's design is a Circlotron, right?. Completely different animals. There is no patent on which way you take output on a device, just because the connections look the same at a high level doesn't mean the circuits are the same or even similar in operation. The difference is in the details, not the superficial similarities.

David


Top
 Profile  
 
PostPosted: October 13th, 2017, 9:48 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
FerdinandII wrote:
Did you bring your 45 amp to Roscoe's once? This is back when he had the big bass horns. I seem to remember listening to them and comparing to Roscoe's 2A3 amps. Towards the end he put in some monoplate RCA 2A3's and I heard first hand why people pay silly prices for them.


I cannot remember if I brought them over to Roscoe, but distinctly remember hearing those monoplate RCA 2A3s in his convertible amp. It was fun with the horns, even though were kind of overpowering in his listening room, especially with the big midrange horns ontop of the bass horns.


David


Top
 Profile  
 
PostPosted: October 13th, 2017, 10:14 am 
Offline

Joined: March 12th, 2013, 11:12 am
Posts: 738
Yea, original monoplate 2A3s just sound great. The 45 is also a really nice tube (clear, extended, detailed, transparent) but lacks a little bit of the tonal lushness that monoplane 2A3s bring to the table IMHO. Too bad original monoplate 2A3s are so difficult to find.


Top
 Profile  
 
PostPosted: October 13th, 2017, 10:46 am 
Offline
User avatar

Joined: April 20th, 2014, 5:21 pm
Posts: 233
I built one of those Bugle amps before I even published the article. Yeah, 45 is hard to beat. Also, I liked the flavor of that 12AY7 SRPP driver more than I have liked other tubes in SRPP.

I am not surprised that you like this more than a lot of other amps...Then you are faced with the crushing reality of having 2 watts and you have to figure out the speaker side of the equation.

A dilemma all who go down this rabbit hole must face. Life's a bitch.

The booster amp concept is almost as old as the triode amp itself, e.g WE 43, WE 87, Altec 287. In the olden days, a pr of 211 or 845s per side would have been the ticket for your ~25W class A.

We tried a lot of 211 845 GM70 and WE variants 284D 242A etc at Silbatone and never came up with anything that would smoke or even equal a good 300B amp.

The 45 might be a good choice to drive that Pass booster but I would expect no free lunch, not that free lunch and 25W Class A should ever be in the same paragraph! Possibly an excellent bass amp though, or use it on the woofs and biamp with the 45 atop.

But if the goal is bass amp, a PP 2A3/6B4G might be the driver you want. Or just use the PP 2A3 and forget the Pass booster!

Triode wired 6AV5s will be extremely close to 6B4Gs electrically and in fact Sylvania sold such internally strapped as 6B4Gs in the waning years. The main application for 6B4Gs by then was regulator pass tubes and directly heated wasn't valued as a "thing" for that service.

Really, the whole thing comes down to a speaker management issue. If addressed through a rising lust for power, usually some sacrifices must be made and the subtlety of presentation you're getting from a bareback 45SE will be the first thing to go.


Top
 Profile  
 
PostPosted: October 13th, 2017, 11:24 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Joe,

I have lots of options to play with currently working 2A3 SET, 300B SET, GM70 SET amps, and a PP2A3 that needs work, in addition to the Bugle. I could have a great time with a high quality electronic crossover and tri-amp my system. (maybe my next project???).

The last time I ran the Bugle was when I had a horn setup several years ago, and used that on the midrange/tweeter horns, with PP2A3's on the midbass horns.

Frankly, I really don't NEED the Pass F4, but got the bug to build something that doesn't take a lot of time and work (i.e chassis build, layout), just out of curiosity. Also, I have heard of other Basszilla owners who like this setup, so wanted to see how well it works. After I build and listen to it, if other wanted to try it out, I could loan it out to the curious. Of course, I first need to try it with all my SET amps in biamp mode or gain stage mode first, and that could take some time. Sounds like a great thing to bring to a meet.

David


Top
 Profile  
 
PostPosted: October 13th, 2017, 1:06 pm 
Offline
User avatar

Joined: April 20th, 2014, 5:21 pm
Posts: 233
Yeah I totally understand the crazed DIY impulse. I am building a modified EAR 834 phono stage right now and I don't remember why! Saw a bunch of guys over on Lenco Heaven building the China ripoff PCBs so that got me started. I'm using all surplus precision wirewounds to see what they sound like, otherwise 12AX7s with FB EQ is not what I would usually gravitate toward. WTF...who is steering this vessel anyway? :confusion-confused:

Especially when I have a set of silver wire LCR modules and a pr of Silk 10k LCR modules I need to try, and all of the parts on hand to build those swankier options.

If you have the goods for a PP 2A3, that amp should have pretty good control, especially if you drive the snot out of the 2A3s with a topology that can provide current, such as the Brook 12A hookup (use the primary of a cheap PP trans as the split choke, or Heyboer can make you one).

Don't know how far you have to go to run Basszillas.

My bud Mike Quinn just bought a Yamamoto 45 amp and found a pr of Zu speakers that he likes with them, more than his old Zus or DeVores, both of which he sold off. Initially he was all worried about the low power but he outgrew that phobia after a week. It is what it is and does what it does, which is very good.

The concept of multiamp seems appealing on paper but do we really need all of that segmentation of the continuum? In my mind, a widerange LF speaker with a widerange horn in a two way with only the filters needed to make the speakers work where they are most compelling is the most complex technology that the SE45 deserves, if you want to revel in that SE45 holism.

I'm feeling that multiway multiamp setups might trade off some organic wholeness for impressive sonics, which might be a fun and educational experiment. Also, playing around with a flexible digital xover can tell you a lot about what working conditions your drivers/horns are most happy under, for future reference. Then, if you want to back down to a simpler arrangement, you can do so with some guiding experience.

At a recent Munich show, we had a multiamp setup using two $150 DBX analog xovers, with a Marantz 9 on low bass, say under 60 hz (EV-30"s), a 300B SE on midbass up to 120 (Lansing 415 field coils), then a 750 mW 6900 SE on six WE 555 drivers with 11A horns and one pr of 24A horns. No xover on the horns, which were good to like 125hz. It hung together fairly well and it was spectacularly "impressive" as a demo item. Crazy stuff. Hard on the brain to process compared with a simple singe or two way though. Too much information processing going on.

https://www.youtube.com/watch?v=iUy-S9Miynw

The humble DBX223 crossovers sounded quite good in this and other experiments and they are cheap. Something like a couple miniDSPs would give a lot more flexibility though, at the cost of a roomful of junk, which most of us have already anyway.


Top
 Profile  
 
PostPosted: October 13th, 2017, 1:39 pm 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Joe,

That is a crazy setup, Kurt Weill seemed right at home on that system.

My PP2A3 amp is a simple single stage driver (WE417/5842) into a transformer phase splitter (Lundahl L1660). Some, but not alot of drive. I need to revisit that amp, since it has some nice Hashimoto output transformers that I packed in my luggage on a trip back from Tokyo well over a decade ago, so with that nice iron, I should do something to get it working again.

Yeah, I have been doing "fast food" DIY audio recently, since I have not had time for a real gourmet "slow food" project since my GM70 SETs. Winter is coming....

David


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 37 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 45 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group