Need help with tube test data - fast

HugoR · 7th November 2005, 03:16 PM

Hi,

Would like advice before buying tubes. I am about to buy 4 6AN8A pairs (2 pairs/brand) and asked triode matching datas from the dealer.

Circuit uses a pair of 6AN8s for gain/phase splitting and has bias adjustment for each channel as well as test points and trimmer pots for DC and AC balance of each channel.

Is triode matching important in these conditions?

Here's the test data from the Zenith, Rogers valves.
Data is Triode / Pentode, in uMhos, measured/tested on Stark 9-66 Mutual Transconductance test set.

Rogers
4900/4100
4900/4700
4650/4200
4850/4250
4250/3800
3400/4100

Zenith (USA)
3400/3600
4500/3800
5000/4100
3900/3700

Zenith (UK)
5100/4100
5000/4050
3900/3650
4550/3850
3400/3950

As you can see, "matching" sets of triode-pentode tubes in brands is difficult.

Thanks for any and all help.
HugoR

SY · 7th November 2005, 03:18 PM

If the triodes are used as a split load (like the Dyna circuit), matching them is not terribly important.

HugoR · 7th November 2005, 03:31 PM

The circuit is a three-stage feedback amp employing a common 6AN8 triodepentode as the voltage amp and phase inverter. The input signal is applied to the 6AN8 penthode grid, after being coupled through a 15000 ohm isolating resistor. The penthode acts as a voltage amp and DC-couples the signal to the grid of the triode phase inverter.

HugoR

SY · 7th November 2005, 03:34 PM

That sounds like the Dyna circuit. Are the plate and cathode resistors of the triode equal? If so, it's a split load, it's operating under nearly 100% feedback, and the matching is not critical.

HugoR · 7th November 2005, 03:46 PM

IIRC, plate and cathode resistors are equal to 27000 ohm, 1W.

HugoR · 7th November 2005, 04:27 PM

I am wrong.
Plate resistor are different. See the circuit bellow.
R7 = 27000 ohm
R9 = 39000 ohm

Thanks

SY · 7th November 2005, 05:43 PM

Without commenting that the guy who drew this schematic should be taken behind the barn and spanked with an axe, you left off the important bit- the triode phase splitter in question.

HugoR · 7th November 2005, 06:26 PM

SY,
I am sorry. Image was too big!
The link of the complete schema is bellow... Hope it will work.
I appreciate your help.
Hugor

HugoR · 7th November 2005, 06:41 PM

Retrying with the link

.

Don't know how to handle IMG If link doesn't work. Sorry.

Thanks alot.
H

HugoR · 7th November 2005, 06:43 PM

Wow! Works this way.

7th November 2005, 03:16 PM	#1
HugoR diyAudio Member Join Date: Oct 2005	Need help with tube test data - fast Hi, Would like advice before buying tubes. I am about to buy 4 6AN8A pairs (2 pairs/brand) and asked triode matching datas from the dealer. Circuit uses a pair of 6AN8s for gain/phase splitting and has bias adjustment for each channel as well as test points and trimmer pots for DC and AC balance of each channel. Is triode matching important in these conditions? Here's the test data from the Zenith, Rogers valves. Data is Triode / Pentode, in uMhos, measured/tested on Stark 9-66 Mutual Transconductance test set. Rogers 4900/4100 4900/4700 4650/4200 4850/4250 4250/3800 3400/4100 Zenith (USA) 3400/3600 4500/3800 5000/4100 3900/3700 Zenith (UK) 5100/4100 5000/4050 3900/3650 4550/3850 3400/3950 As you can see, "matching" sets of triode-pentode tubes in brands is difficult. Thanks for any and all help. HugoR

7th November 2005, 03:18 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	If the triodes are used as a split load (like the Dyna circuit), matching them is not terribly important. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

7th November 2005, 03:34 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	That sounds like the Dyna circuit. Are the plate and cathode resistors of the triode equal? If so, it's a split load, it's operating under nearly 100% feedback, and the matching is not critical. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

7th November 2005, 05:43 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Without commenting that the guy who drew this schematic should be taken behind the barn and spanked with an axe, you left off the important bit- the triode phase splitter in question. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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7th November 2005, 03:31 PM	#3
HugoR diyAudio Member Join Date: Oct 2005	The circuit is a three-stage feedback amp employing a common 6AN8 triodepentode as the voltage amp and phase inverter. The input signal is applied to the 6AN8 penthode grid, after being coupled through a 15000 ohm isolating resistor. The penthode acts as a voltage amp and DC-couples the signal to the grid of the triode phase inverter. HugoR

7th November 2005, 03:46 PM	#5
HugoR diyAudio Member Join Date: Oct 2005	IIRC, plate and cathode resistors are equal to 27000 ohm, 1W.

7th November 2005, 06:26 PM	#8
HugoR diyAudio Member Join Date: Oct 2005	SY, I am sorry. Image was too big! The link of the complete schema is bellow... Hope it will work. I appreciate your help. Hugor

7th November 2005, 06:41 PM	#9
HugoR diyAudio Member Join Date: Oct 2005	Retrying with the link . Don't know how to handle IMG If link doesn't work. Sorry. Thanks alot. H

7th November 2005, 06:43 PM	#10
HugoR diyAudio Member Join Date: Oct 2005	Wow! Works this way.

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