Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Sep Thu 21, 2017 6:14 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 1487 posts ]  Go to page Previous  1 ... 62, 63, 64, 65, 66, 67, 68 ... 75  Next
Author Message
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 3:26 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
I am working slowly on the preamp. It is laying out pretty well. A joy to build as all my projects are, thanks to you guys.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 3:39 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Men
I need to know about the shielding of inputs. One shielded cable for both channels, or separate?

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 4:15 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
john8750 wrote:
Flip
Why the driver stage, V3? More output power, a buffer for less THD. Really good looking design. Is there any form of CCS there? How to balance the output tubes?
I could always use one more amp project, after the transmitter and tuner.
Of course I will need a tone stack. :lol:
You'll have a tone stack in your preamp. That's the advantage of building a separate preamp instead of having to build one for each amplifier.

The driver stage is basically to get enough gain. It takes 80 V peak to peak to drive the grids to max power, and then you need some overdrive capability. Calculate it out, 290 mV to 27 V(rms) takes a gain of 93, without using any negative feedback. 20 dB of feedback is x10, so now you're at 930. Look at the gain of my circuit. It's 63 x 14.6 for 920 (rounded). The '10' difference is accumulated measurement rounding (voltages, gain, etc.).

Now, you might think we could do it with a pentode, like we did on Prince John, but triodes have less distortion and, in any event, a gain of 930 is just too much for a single pentode gain stage. We got away with it in Prince John because it takes only 7 volts, or so, to drive it to max power, so we didn't need as much gain, plus we didn't use as much feedback, 14dB (in UL) vs 20dB. That 6dB cut Prince John's gain requirement in half.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 4:20 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
john8750 wrote:
Men
I need to know about the shielding of inputs. One shielded cable for both channels, or separate?
I do separate.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 5:22 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Flipperhome wrote:
john8750 wrote:
Flip
Why the driver stage, V3? More output power, a buffer for less THD. Really good looking design. Is there any form of CCS there? How to balance the output tubes?
I could always use one more amp project, after the transmitter and tuner.
Of course I will need a tone stack. :lol:
You'll have a tone stack in your preamp. That's the advantage of building a separate preamp instead of having to build one for each amplifier.

The driver stage is basically to get enough gain. It takes 80 V peak to peak to drive the grids to max power, and then you need some overdrive capability. Calculate it out, 290 mV to 27 V(rms) takes a gain of 93, without using any negative feedback. 20 dB of feedback is x10, so now you're at 930. Look at the gain of my circuit. It's 63 x 14.6 for 920 (rounded). The '10' difference is accumulated measurement rounding (voltages, gain, etc.).

Now, you might think we could do it with a pentode, like we did on Prince John, but triodes have less distortion and, in any event, a gain of 930 is just too much for a single pentode gain stage. We got away with it in Prince John because it takes only 7 volts, or so, to drive it to max power, so we didn't need as much gain, plus we didn't use as much feedback, 14dB (in UL) vs 20dB. That 6dB cut Prince John's gain requirement in half.



I see. I like the incredible calculated THD. What, in that amp circuit is that related to? What about the alignment method.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 5:23 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Flipperhome wrote:
john8750 wrote:
Men
I need to know about the shielding of inputs. One shielded cable for both channels, or separate?
I do separate.



Thanks Flip. I will also separate, and shield only at the input jack common.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 5:51 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
john8750 wrote:
Flipperhome wrote:
You'll have a tone stack in your preamp. That's the advantage of building a separate preamp instead of having to build one for each amplifier.

The driver stage is basically to get enough gain. It takes 80 V peak to peak to drive the grids to max power, and then you need some overdrive capability. Calculate it out, 290 mV to 27 V(rms) takes a gain of 93, without using any negative feedback. 20 dB of feedback is x10, so now you're at 930. Look at the gain of my circuit. It's 63 x 14.6 for 920 (rounded). The '10' difference is accumulated measurement rounding (voltages, gain, etc.).

Now, you might think we could do it with a pentode, like we did on Prince John, but triodes have less distortion and, in any event, a gain of 930 is just too much for a single pentode gain stage. We got away with it in Prince John because it takes only 7 volts, or so, to drive it to max power, so we didn't need as much gain, plus we didn't use as much feedback, 14dB (in UL) vs 20dB. That 6dB cut Prince John's gain requirement in half.
I see. I like the incredible calculated THD. What, in that amp circuit is that related to? What about the alignment method.
I think "incredible" is right. That's a SPICE number and SPICE uses 'ideal' components of the 'exact' value; like the two 47.5k Ohm are exactly 47.5k Ohm each, which will never be the case, and the same goes for everything else. That distortion number is more a 'theoretical' best it could be and actual will be something a little less fantastic.

I use those numbers to compared circuit changes but not as an entirely faithful indicator of the 'real life' circuit.

Even discounting the results, however, distortion should be exceptionally low and that's due to 1. the UL OPT and 2. the 20dB of feedback, and 3. the bootstrapped first gain stage.

I haven't quite worked out the bias adjust procedure yet and that portion of the circuit is still a little bit in question. The idea behind it is it's 'failsafe'. Like, if the pot wiper is dirty and disconnects then the bias goes low (current wise) but the amp will still function. The issue is as bias changes, i.e. the resistor is adjusted, the grid resistance changes but it's less than 1%, the tolerance of the resistor itself, so it should be a non issue.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 7:35 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Flipperhome wrote:
john8750 wrote:
Flipperhome wrote:
You'll have a tone stack in your preamp. That's the advantage of building a separate preamp instead of having to build one for each amplifier.

The driver stage is basically to get enough gain. It takes 80 V peak to peak to drive the grids to max power, and then you need some overdrive capability. Calculate it out, 290 mV to 27 V(rms) takes a gain of 93, without using any negative feedback. 20 dB of feedback is x10, so now you're at 930. Look at the gain of my circuit. It's 63 x 14.6 for 920 (rounded). The '10' difference is accumulated measurement rounding (voltages, gain, etc.).

Now, you might think we could do it with a pentode, like we did on Prince John, but triodes have less distortion and, in any event, a gain of 930 is just too much for a single pentode gain stage. We got away with it in Prince John because it takes only 7 volts, or so, to drive it to max power, so we didn't need as much gain, plus we didn't use as much feedback, 14dB (in UL) vs 20dB. That 6dB cut Prince John's gain requirement in half.
I see. I like the incredible calculated THD. What, in that amp circuit is that related to? What about the alignment method.
I think "incredible" is right. That's a SPICE number and SPICE uses 'ideal' components of the 'exact' value; like the two 47.5k Ohm are exactly 47.5k Ohm each, which will never be the case, and the same goes for everything else. That distortion number is more a 'theoretical' best it could be and actual will be something a little less fantastic.

I use those numbers to compared circuit changes but not as an entirely faithful indicator of the 'real life' circuit.

Even discounting the results, however, distortion should be exceptionally low and that's due to 1. the UL OPT and 2. the 20dB of feedback, and 3. the bootstrapped first gain stage.

I haven't quite worked out the bias adjust procedure yet and that portion of the circuit is still a little bit in question. The idea behind it is it's 'failsafe'. Like, if the pot wiper is dirty and disconnects then the bias goes low (current wise) but the amp will still function. The issue is as bias changes, i.e. the resistor is adjusted, the grid resistance changes but it's less than 1%, the tolerance of the resistor itself, so it should be a non issue.



Great. I guess there is no need for a CCS then. I like the OPT's on my 6V6. IT, and the 5902 are some real nice amps. Why don't you try that same garter circuit we have on the Prince John? It seems to work well, and very easy to align.
Could you please explain the theory of the bootstrap and how it operates? Sounds very interesting.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 8:17 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
john8750 wrote:
Flipperhome wrote:
I think "incredible" is right. That's a SPICE number and SPICE uses 'ideal' components of the 'exact' value; like the two 47.5k Ohm are exactly 47.5k Ohm each, which will never be the case, and the same goes for everything else. That distortion number is more a 'theoretical' best it could be and actual will be something a little less fantastic.

I use those numbers to compared circuit changes but not as an entirely faithful indicator of the 'real life' circuit.

Even discounting the results, however, distortion should be exceptionally low and that's due to 1. the UL OPT and 2. the 20dB of feedback, and 3. the bootstrapped first gain stage.

I haven't quite worked out the bias adjust procedure yet and that portion of the circuit is still a little bit in question. The idea behind it is it's 'failsafe'. Like, if the pot wiper is dirty and disconnects then the bias goes low (current wise) but the amp will still function. The issue is as bias changes, i.e. the resistor is adjusted, the grid resistance changes but it's less than 1%, the tolerance of the resistor itself, so it should be a non issue.
Great. I guess there is no need for a CCS then. I like the OPT's on my 6V6. IT, and the 5902 are some real nice amps. Why don't you try that same garter circuit we have on the Prince John? It seems to work well, and very easy to align.
Could you please explain the theory of the bootstrap and how it operates? Sounds very interesting.
For the bootstrap, see my post to Peter on what C5 does. It's explained there.

The garter bias takes twice the cathode voltage to work but cathode voltage on this one is already 40V so a garter would take 80 volt. With 100 mA x2 (since it's stereo) bias current that's a heck of a lot of power, 16 Watt, to waste.

Prince John has a lot lower bias voltage, as well as current. On top of that, the 6HB6 is almost half the normal bias voltage of a 6BQ5 (the tube it was replacing) so the garter was virtually 'free'.

Btw, besides a CCS being 1940's impossible (they didn't have solid state then), it's getting up there in power too. Of course, you can solve any heatsinking problem if you throw enough iron at it but 2 Watt of dissipation is non trivial, times 4 for the whole amp, because you then have the problem of where to mount them. Inside is rather warm to begin with (meaning a bigger heatsink to compensate) but top side is problematic because the mounting tab is likely at voltage. I'm dealing with that issue right now for the MOSFET cap multiplier, which is at 450 V.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 11:23 pm 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Flipperhome wrote:
john8750 wrote:
Flipperhome wrote:
I think "incredible" is right. That's a SPICE number and SPICE uses 'ideal' components of the 'exact' value; like the two 47.5k Ohm are exactly 47.5k Ohm each, which will never be the case, and the same goes for everything else. That distortion number is more a 'theoretical' best it could be and actual will be something a little less fantastic.

I use those numbers to compared circuit changes but not as an entirely faithful indicator of the 'real life' circuit.

Even discounting the results, however, distortion should be exceptionally low and that's due to 1. the UL OPT and 2. the 20dB of feedback, and 3. the bootstrapped first gain stage.

I haven't quite worked out the bias adjust procedure yet and that portion of the circuit is still a little bit in question. The idea behind it is it's 'failsafe'. Like, if the pot wiper is dirty and disconnects then the bias goes low (current wise) but the amp will still function. The issue is as bias changes, i.e. the resistor is adjusted, the grid resistance changes but it's less than 1%, the tolerance of the resistor itself, so it should be a non issue.
Great. I guess there is no need for a CCS then. I like the OPT's on my 6V6. IT, and the 5902 are some real nice amps. Why don't you try that same garter circuit we have on the Prince John? It seems to work well, and very easy to align.
Could you please explain the theory of the bootstrap and how it operates? Sounds very interesting.
For the bootstrap, see my post to Peter on what C5 does. It's explained there.

The garter bias takes twice the cathode voltage to work but cathode voltage on this one is already 40V so a garter would take 80 volt. With 100 mA x2 (since it's stereo) bias current that's a heck of a lot of power, 16 Watt, to waste.

Prince John has a lot lower bias voltage, as well as current. On top of that, the 6HB6 is almost half the normal bias voltage of a 6BQ5 (the tube it was replacing) so the garter was virtually 'free'.

Btw, besides a CCS being 1940's impossible (they didn't have solid state then), it's getting up there in power too. Of course, you can solve any heatsinking problem if you throw enough iron at it but 2 Watt of dissipation is non trivial, times 4 for the whole amp, because you then have the problem of where to mount them. Inside is rather warm to begin with (meaning a bigger heatsink to compensate) but top side is problematic because the mounting tab is likely at voltage. I'm dealing with that issue right now for the MOSFET cap multiplier, which is at 450 V.



Thanks for explaining about those durned details.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Mon 09, 2017 11:50 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20379
Location: Haledon, NJ, usa
BTW John/ Flip:
If John does want to make another beefy amp... I have some 6DQ5 tubes.
Flip, can those 6DQ5s make a good audio amp?
Have you seen a schematic with them in PP?
Have you ever tried them yourself?
What do you think of that tube
Image

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 1:41 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Guess what. The Mallory deal that I won and paid for was cancelled. How can that happen. The deal was done and finished. I cant believe that is legal business on ebay. :evil:

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 1:58 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20379
Location: Haledon, NJ, usa
john8750 wrote:
Guess what. The Mallory deal that I won and paid for was cancelled. How can that happen. The deal was done and finished. I cant believe that is legal business on ebay. :evil:

Some ppl try those tricks when they don't get the money they had hoped for. So they claim it's no longer available... as though it was sold elsewhere... or some such crap.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:05 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
Pbpix wrote:
BTW John/ Flip:
If John does want to make another beefy amp... I have some 6DQ5 tubes.
Flip, can those 6DQ5s make a good audio amp?
Have you seen a schematic with them in PP?
Have you ever tried them yourself?
What do you think of that tube
While you can make an amp out of almost anything sweep tubes often have low screen voltages and high heater current (to get the emissivity necessary for high output at low voltages) as does the 6DQ5. The low screen voltage makes them unsuitable for UL (unless you have a separate UL winding, which is almost impossible to find nowadays).

The 807 is legendary as it has been called "the tube that won the war" and the classic coke bottle shape is hard to beat for sheer 'tube' appeal.

Image

And since it's basically a 6L6 modified for a plate cap (RF use) there are a ton of amplifier schematics for it.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:14 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Flipperhome wrote:
Pbpix wrote:
BTW John/ Flip:
If John does want to make another beefy amp... I have some 6DQ5 tubes.
Flip, can those 6DQ5s make a good audio amp?
Have you seen a schematic with them in PP?
Have you ever tried them yourself?
What do you think of that tube
While you can make an amp out of almost anything sweep tubes often have low screen voltages and high heater current (to get the emissivity necessary for high output at low voltages) as does the 6DQ5. The low screen voltage makes them unsuitable for UL (unless you have a separate UL winding, which is almost impossible to find nowadays).

The 807 is legendary as it has been called "the tube that won the war" and the classic coke bottle shape is hard to beat for sheer 'tube' appeal.

Image

And since it's basically a 6L6 modified for a plate cap (RF use) there are a ton of amplifier schematics for it.



Heck ya. Remember the amp Dr. Brown built with the 6 foot speaker? Must of used those tubes. Till Marty hit a chord and blew it up.

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:16 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
OK, here is the transmitter I settled on. If I cant get the PT, we will need to improvise. I remember Flip saying we could rework the B+. Thanks Flip. You suggested this one.
viewtopic.php?f=12&t=132867

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:19 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
Pbpix wrote:
john8750 wrote:
Guess what. The Mallory deal that I won and paid for was cancelled. How can that happen. The deal was done and finished. I cant believe that is legal business on ebay. :evil:

Some ppl try those tricks when they don't get the money they had hoped for. So they claim it's no longer available... as though it was sold elsewhere... or some such crap.



That sucks. I cant believe this could be legal on ebay. I will try for another one.
http://www.ebay.com/itm/162343718159?_t ... EBIDX%3AIT

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:23 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20379
Location: Haledon, NJ, usa
From the standpoint of kool-looking, how about this dual heptode 5894?
I think it was listed somewhere as an AF/RF power amplifier.
Is that true?
Image

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:40 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 7584
Location: Texas. USA
john8750 wrote:
Flipperhome wrote:
While you can make an amp out of almost anything sweep tubes often have low screen voltages and high heater current (to get the emissivity necessary for high output at low voltages) as does the 6DQ5. The low screen voltage makes them unsuitable for UL (unless you have a separate UL winding, which is almost impossible to find nowadays).

The 807 is legendary as it has been called "the tube that won the war" and the classic coke bottle shape is hard to beat for sheer 'tube' appeal.

Image

And since it's basically a 6L6 modified for a plate cap (RF use) there are a ton of amplifier schematics for it.
Heck ya. Remember the amp Dr. Brown built with the 6 foot speaker? Must of used those tubes. Till Marty hit a chord and blew it up.
Since it took place in the mid 80's I always assumed it was solid state but if you pay attention to the controls when Marty's powering it up it's clearly tube.

Attachment:
Doc Brown Amp.jpg
Doc Brown Amp.jpg [ 56.28 KiB | Viewed 506 times ]


Top
 Profile  
 
 Post subject: Re: PRINCELY PAUPER
PostPosted: Jan Tue 10, 2017 2:51 am 
Member
User avatar

Joined: Dec Mon 29, 2014 9:39 pm
Posts: 2776
Location: Los Angeles
OK, lets try this one. Don't know if it used a tube rectifier. But a nice looking unit for $24.
http://www.ebay.com/itm/162343718159?_t ... EBIDX%3AIT

_________________
John Smith, over and out.
If I did something right, I made a mistake.


Top
 Profile  
 
Post New Topic Post Reply  [ 1487 posts ]  Go to page Previous  1 ... 62, 63, 64, 65, 66, 67, 68 ... 75  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB