Please review schematic

dstockwell · 17th September 2005, 02:06 AM

I found a 300B schematic from Bob Danielak and tried the e-amil with no response. I have some issue's with some 1K vs 100K vs 100 (no K marked), would you experts please review my redraw and help, please.

These are the orginals

dstockwell · 17th September 2005, 02:07 AM

PS

dstockwell · 17th September 2005, 02:09 AM

Redraw

jsn · 17th September 2005, 03:29 AM

I just designed this direct-coupled 1626 driver for an amp I am building. Very similar to this design, but driver is direct coupled and choke loaded (use cheap 60H/30mA Handmade Electronics choke).

This should be a big bad driver stage - it could be a 1W amp all by itself. In fact, I plan to build it as a DC-Darling amp at some point.

I am using a 6sn7/6j5 as the input tube.

If you do this DC thing, use a 12vct filament transformer for each 1626 and connect the canter tap to the cathode to minimize filament-cathode potential, often a problem with DC designs.

jsn

jsn · 17th September 2005, 03:36 AM

2 things:

1) The values on the schematic you posted look correct. I didn't see any obvious errors.

2) I forgot to draw a grid resistor in the scematic I just posted. please use whatever your preamp wants (or a pot or whatever). 100k seems to be "standard".

I am working on a followup to my little "hi fi primer" that will show folks how to work through a direct-coupled design and will probably use this 6j5/6sn7-1626 amp as the example. I promise to build it and everythig to prove it works.

Check here for updates:

http://boozhoundlabs.com/

jsn

kmtang · 18th September 2005, 11:21 AM

4.8K impedance OPT seems too large for the 300B. I prefer running it with 2.5K to 3.5K.

dstockwell · 18th September 2005, 12:59 PM

Quote:

Originally posted by kmtang
4.8K impedance OPT seems too large for the 300B. I prefer running it with 2.5K to 3.5K.

If I use a lower K OPT @ which MA value do I use. The one in the schematic is 110MA.

jsn · 18th September 2005, 03:49 PM

The current through the out put transformer will be the same. The impedance listed is not DC Resistance, but the ac impedace presented to the 300b, determined by the ratio of primary and secondary windings and the load placed across the secondary - the speaker.

A higher impedance ususally results in lower distortion, and slightly less power.

jsn

analog_sa · 18th September 2005, 04:03 PM

Bob Danielak's values seem all fine. In the 'redraw' the gridstoppers are 100k which is obviously silly - they should be 100R on the 300B and anything between 100R-1k on the other tubes depending on taste.

dstockwell · 18th September 2005, 05:17 PM

thanks analog, it will fix the redraw.

17th September 2005, 03:36 AM	#5
jsn diyAudio Member Join Date: Sep 2004 Location: The Atomic City	2 things 2 things: 1) The values on the schematic you posted look correct. I didn't see any obvious errors. 2) I forgot to draw a grid resistor in the scematic I just posted. please use whatever your preamp wants (or a pot or whatever). 100k seems to be "standard". I am working on a followup to my little "hi fi primer" that will show folks how to work through a direct-coupled design and will probably use this 6j5/6sn7-1626 amp as the example. I promise to build it and everythig to prove it works. Check here for updates: http://boozhoundlabs.com/ jsn

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18th September 2005, 11:21 AM	#6
kmtang diyAudio Member Join Date: Nov 2004 Location: Vancouver	4.8K impedance OPT seems too large for the 300B. I prefer running it with 2.5K to 3.5K.

18th September 2005, 03:49 PM	#8
jsn diyAudio Member Join Date: Sep 2004 Location: The Atomic City	The current through the out put transformer will be the same. The impedance listed is not DC Resistance, but the ac impedace presented to the 300b, determined by the ratio of primary and secondary windings and the load placed across the secondary - the speaker. A higher impedance ususally results in lower distortion, and slightly less power. jsn

18th September 2005, 04:03 PM	#9
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Bob Danielak's values seem all fine. In the 'redraw' the gridstoppers are 100k which is obviously silly - they should be 100R on the 300B and anything between 100R-1k on the other tubes depending on taste.

18th September 2005, 05:17 PM	#10
dstockwell diyAudio Member Join Date: Jul 2005 Location: Georgia	thanks analog, it will fix the redraw.

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