[Rocko1]

Quote:

Not exactly the same. There are resistors in there to step the power down. They also raise output impedance.
300 ohms is actually a very easy load to drive. It's low impedance loads that make an amp sweat.

Yep, just took this last night from my Sherwood 7100A. Two resistors. The switch is the speaker outputs. Resistor value is 271K if I am not mistake. Not sure how much that lowers this 17 watt receiver.

 

[ardgedee]

Quote:

Well, to be honest, I'm not planning on driving a specific set of cans. At the moment, all I have is JVC harx700's, which I'm sure anything will be able to drive. I was thinking more on terms of when I have a little more funding (which should be fairly soon) and I can actually afford to upgrade to some higher quality phones. So, any unit with 10 watts per channel for the power amp, will be enough even after the stepdown for the headphone output?

 
It's impossible to say without knowing exactly what equipment you're thinking of. There are high-quality phones which are extremely efficient, and there are some that are not. Some thrive on lots of current and others are somewhat indifferent to it. Similarly, some receivers might not have any significant damping at the headphone jack, and others do.
 
It's good to know what your options are, and to use this time to learn more about them, but I recommend not worrying about matching equipment until the opportunity to get some particular receiver or headphone presents itself.

 

[palmfish]

Quote:

Yep, just took this last night from my Sherwood 7100A. Two resistors. The switch is the speaker outputs. Resistor value is 271K if I am not mistake. Not sure how much that lowers this 17 watt receiver.

 
Good for you!
 
That's my next step. I have a Carver Receiver and have downloaded schematics and even sent Bob an e-mail with no reply to find out the output impedance of my headphone jack. Now if only I could remember how to read those colored bands - it's been 28 years since I went to AIT...

 
I'm no tech, so I'm wondering if anyone has ever just replaced the resistors with straight wire? Seems a lot easier than making a speaker tap (which I have also done just for grins and practice). It seems obvious enough, but are there any other considerations/hazards involved?

 

[Skylab]

Yes, some folks have removed the dropping resistor. The only issue is if you have very sensitive headphones, you may not get much play with the volume control, and you may get some hiss. But for some amp/receiver and headphone combos it can be a good idea.

 

[moodyrn]

I did something similar with my fisher when I owned the he-5. I didn't completely remove the resistor, but instead dropped the value from 330ohm to 165ohm essentially doubling the power from the headphone jack. This gave me the ability to drive them from the headphone out while still being able to driver lower impedance cans as well.Now after owning my he-6, I've gone back to the stock value since I used the speaker taps for those anyway. But during that time, I had great results, and could even use the low impedance d7000 I also had at the time with no hiss or hum whatsoever. This could work fine on a 17wpc receiver, but I wouldn't dare try it on any of the higher powered ones.

 

[wotts]

Quote:

 
Good for you!
 
That's my next step. I have a Carver Receiver and have downloaded schematics and even sent Bob an e-mail with no reply to find out the output impedance of my headphone jack. Now if only I could remember how to read those colored bands - it's been 28 years since I went to AIT...

 
I'm no tech, so I'm wondering if anyone has ever just replaced the resistors with straight wire? Seems a lot easier than making a speaker tap (which I have also done just for grins and practice). It seems obvious enough, but are there any other considerations/hazards involved?

Briefly,
 
Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Grey - 8
White - 9
 
Silver/gold are tolerance bands 10%/5%
 
Put the numbers from the first two colors together then multiply it by 10 raised to the power of the third band. So the pictured resistors have Red, Violet, Yellow (as far as I can tell) so 27 x 10^4 = 270,000 = 270K +/- 10%
 
More info here: http://en.wikipedia.org/wiki/Electronic_color_code
 
Quote:

Yep, just took this last night from my Sherwood 7100A. Two resistors. The switch is the speaker outputs. Resistor value is 271K if I am not mistake. Not sure how much that lowers this 17 watt receiver.
 

 

[palmfish]

Quote:

Quote:
Briefly,
 
Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Grey - 8
White - 9
 
Silver/gold are tolerance bands 10%/5%
 
Put the numbers from the first two colors together then multiply it by 10 raised to the power of the third band. So the pictured resistors have Red, Violet, Yellow (as far as I can tell) so 27 x 10^4 = 270,000 = 270K +/- 10%
 
More info here: http://en.wikipedia.org/wiki/Electronic_color_code
 

Copied and pasted for posterity. Thank You!

 

[wotts]

 
Happy to help!!
 
I picked up a 2230 recently. It's in need of some TLC - lights burnt out, dusty, etc. It does have some channel imbalance as well. I plan to get it on the bench when work slows down. I have a question for those of you who have done some restoration: how do you get teh caked on dust out? I tried some vacuuming, but there is a lot of residue still left.

 

[Rocko1]

Quote:

Quote:
Briefly,
 
Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Grey - 8
White - 9
 
Silver/gold are tolerance bands 10%/5%
 
Put the numbers from the first two colors together then multiply it by 10 raised to the power of the third band. So the pictured resistors have Red, Violet, Yellow (as far as I can tell) so 27 x 10^4 = 270,000 = 270K +/- 10%
 
More info here: http://en.wikipedia.org/wiki/Electronic_color_code
 

Ah, thanks. I was adding the third color to the total. Makes sense now. Thank you.
 
Can you tell me how these resistors differ from the sand block type? I would think that this little resistor would overheat with all that power going through it. 

 

[Rocko1]

Quote:

 
Happy to help!!
 
I picked up a 2230 recently. It's in need of some TLC - lights burnt out, dusty, etc. It does have some channel imbalance as well. I plan to get it on the bench when work slows down. I have a question for those of you who have done some restoration: how do you get teh caked on dust out? I tried some vacuuming, but there is a lot of residue still left.

Many use a isopropyl alcohol and water mixture with a paint brush with the bristles cut down-tape the metal edges. Gently scrub the boards with this and then use compressor to dry it and then let it set a day or two with the cover off to make sure it's dry. I have seen boards brought back to brand new condition using this method.

 

[Rocko1]

Quote:

I did something similar with my fisher when I owned the he-5. I didn't completely remove the resistor, but instead dropped the value from 330ohm to 165ohm essentially doubling the power from the headphone jack. This gave me the ability to drive them from the headphone out while still being able to driver lower impedance cans as well.Now after owning my he-6, I've gone back to the stock value since I used the speaker taps for those anyway. But during that time, I had great results, and could even use the low impedance d7000 I also had at the time with no hiss or hum whatsoever. This could work fine on a 17wpc receiver, but I wouldn't dare try it on any of the higher powered ones.

 
I see. I can't get past 9 O'Clock on any of my receivers, even my Marantz 2270 but I am only driving the Panasonic HTF600's which are 56ohm and 100db sensitivity, so they are no sweat. I can't imagine any headphones needing a full 20 watts RMS but I am new to this game.
 
Are their higher quality resistors that would be better suited for the headphone power reduction?

 

[BGRoberts]

I've seen mention of driving headphones off of the speaker taps............. can anyone tell me how you'd setup to do that?
Thanks!
~BG

 

[Maverickmonk]

Skylab, you're vintage HiFi collection is truly incredible. Mad jelly over here, enjoy it!

I'm still definitively mid-fi on the vintage scale, I've added my 3rd 40-50w receiver to my collection, a Fisher RS-1035. It's the smallest of its class, and from the mid 70's. It's not from the Avery era of Fisher but it's still quite well built. If all goes well, I might keep this free unit at school for the tv-stereo and sell the SX-780 to recoup the costs spent on it.

 
 
 
Quote:

 

 

[Skylab]

Thanks.  Nice looking Fisher - I'm not really familiar with that era Fisher - how does it sound?

 

[Maverickmonk]

The controls are still really scratchy, but what sound I'm getting out of it sounds good. Fairly neutral, with a little bass warmth, but since its all old capacitors and it still needs to be cleaned (inside and out), we'll see how that changes.
 
 
Fisher trade?

JK