Search found 1578 matches

by dave slagle
Sun Nov 27, 2022 2:40 pm
Forum: Playing With Airgaps
Topic: Magnetized AVC?
Replies: 8
Views: 61

Re: Magnetized AVC?

I cannot think of anything within the AVC that could cause this.... The apparent short between 12 & 13 should not be there and it is highly unlikely that the problem is internal to the autoformer

dave
by dave slagle
Sat Nov 26, 2022 2:39 pm
Forum: Playing With Airgaps
Topic: Magnetized AVC?
Replies: 8
Views: 61

Re: Magnetized AVC?

it sure seems somehow pins 12 & 13 are shorted to each other. carefully retrace your wiring looking for an error. I am assuming it was functioning properly and then "broke at some point"? The fact that it is happening the same in both channels points to some external cause since it is ...
by dave slagle
Thu Nov 24, 2022 1:17 pm
Forum: Playing With Airgaps
Topic: Magnetized AVC?
Replies: 8
Views: 61

Re: Magnetized AVC?

can you re-check you numbers?

the source impedance (867,2354 ohms) number does not make sense unless it rounds down to 867Ω

the measurements between steps 12 & 13 are the same which should not be the case. what is the DCR between 12&13 (at the switch and at the autoformer.

dave
by dave slagle
Fri Nov 18, 2022 12:53 pm
Forum: Attenuators
Topic: $200 avc wiring diagram
Replies: 6
Views: 2066

Re: $200 avc wiring diagram

it is not possible to get a balanced output from a single ended circuit but two units per channel can attenuate a balanced to balanced line.


dave
by dave slagle
Fri Nov 18, 2022 12:51 pm
Forum: Playing With Airgaps
Topic: Magnetized AVC?
Replies: 8
Views: 61

Re: Magnetized AVC?

Hey, There really isn't any possibility of the AVC to become magnetized or break. The two things that come to mind are a leaky cap putting DC on the core and a possible shorted turn (two pins shorted to each other). A DVM should help diagnose the first and a visual search might point to the second. ...
by dave slagle
Sat Oct 08, 2022 12:56 pm
Forum: Phono
Topic: High Impedance cartridges and SUT's
Replies: 8
Views: 4055

Re: High Impedance cartridges and SUT's

this is a "loaded" question. My answer for myself is I always simply use a DVM to measure the resistance. HOWEVER! I am not going to ever suggest that to anyone else due to the small chance that something goes wrong in the process with a multi-thousand dollar cartridge. and I get blamed. T...
by dave slagle
Sat Oct 08, 2022 12:31 pm
Forum: Playing With Airgaps
Topic: Restacking lams of speakerformers
Replies: 9
Views: 4555

Re: Restacking lams of speakerformers

interesting.

My two questions on the situations:

Was the shunt resistor the same in both cases?

What was the nature of the crossover driving each autoformer?

dave
by dave slagle
Mon Oct 03, 2022 1:50 pm
Forum: Playing With Airgaps
Topic: Restacking lams of speakerformers
Replies: 9
Views: 4555

Re: Restacking lams of speakerformers

It seems odd that the change in the gap would effect the level in the measurements and it really needs to be driven from a ~1Ω source for reasonable results. My guess on the sonic results have to do with the lower inductance value of the 3X3 creating a high pass for information beyond what the speak...
by dave slagle
Fri Sep 23, 2022 1:32 am
Forum: Phono
Topic: High Impedance cartridges and SUT's
Replies: 8
Views: 4055

Re: High Impedance cartridges and SUT's

The difference between 12 and 15 on the step up is only 2dB so for the most part I would consider them interchangeable.

dave
by dave slagle
Thu Sep 22, 2022 12:19 am
Forum: Phono
Topic: High Impedance cartridges and SUT's
Replies: 8
Views: 4055

Re: High Impedance cartridges and SUT's

right.... and from the perspective of the SUT it is being driven from a 2Ω source or 3X the published 0.6Ω. I used to do SUT's specific to the sub 1Ω carts until I realized that the tonearm DCR has a dominant effect on the situation.
dave
by dave slagle
Wed Sep 21, 2022 12:17 am
Forum: Phono
Topic: High Impedance cartridges and SUT's
Replies: 8
Views: 4055

Re: High Impedance cartridges and SUT's

The achilles heel of a 0.6Ω cartridge is the tonearm wiring is often double that value effectively turning it into a 2Ω cartridge.

I would confirm the tonearm DCR prior to committing to a design.

dave
by dave slagle
Sun Sep 04, 2022 1:19 pm
Forum: Attenuators
Topic: Autoformer modules q re second (fine adjustment) switch
Replies: 4
Views: 3491

Re: Autoformer modules q re second (fine adjustment) switch

yes...

I might still have some boards for them though. send me a private email.

dave
by dave slagle
Sun Sep 04, 2022 12:09 am
Forum: Attenuators
Topic: Autoformer modules q re second (fine adjustment) switch
Replies: 4
Views: 3491

Re: Autoformer modules q re second (fine adjustment) switch

Hey.

The modules attenuate completely by selection of taps on the autoformers. I see adding an additional resistive attenuation as a liability rather than an asset.

dave
by dave slagle
Sun Aug 07, 2022 8:35 pm
Forum: Playing With Airgaps
Topic: Restacking lams of speakerformers
Replies: 9
Views: 4555

Re: Restacking lams of speakerformers

it simply comes down to inductance. if you have an excess then increasing the gap is worth a try.

dave
by dave slagle
Thu Jul 28, 2022 3:20 pm
Forum: Phono
Topic: High Impedance cartridges and SUT's
Replies: 8
Views: 4055

High Impedance cartridges and SUT's

I have noticed a trend lately of people asking for high ratio SUTs for higher impedance cartridges. The current request was for a 1:50 for a 22Ω cartridge and the following is why I think that is a bad idea. There are two different places where you can get into trouble here and they both have to do ...
by dave slagle
Mon Jul 18, 2022 11:59 am
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

At this point I think it is probably best to take the unit back to stock and make sure it operates noise free when used single ended.

dave
by dave slagle
Sun Jul 17, 2022 12:31 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

Pins 5,7,8 go to ground.... I cannot use specific ground terminology since I did not design or build the circuit. The negative outputs that were tied to pins 5 & 7 have B+ on them so shoring them to ground is not a good move. I think we may have gotten way off point here and without me being int...
by dave slagle
Sat Jul 16, 2022 11:14 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

5, 7 & 8 all can tie together and go to signal ground.
by dave slagle
Sat Jul 16, 2022 9:21 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

the shield appears to be pin 8 from the diagram

dave
by dave slagle
Sat Jul 16, 2022 12:21 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

Tha autoformers and transformer secondaries should attach to the same ground as the RCA jacks and the signal tubes which appears to be "ref" for the balanced circuit. Ultimately they will all tie together at some point and the goal is to connect them in the manner that gives the least nois...
by dave slagle
Fri Jul 15, 2022 11:54 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

than needs to be tied to audio ground at some point.

dave
by dave slagle
Fri Jul 15, 2022 8:29 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

central tap???

you mean the junction of pins 1 & 3 on the 1674?

dave
by dave slagle
Fri Jul 15, 2022 12:32 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

did you also reference the secondary of the 1674 to ground?

It is unclear what the large cap is.... there is nothing power supply related on the output board. Only the parafeed cap and the mute circuit.
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Screen Shot 2022-07-15 at 8.28.25 AM.png (68.65 KiB) Viewed 8360 times
by dave slagle
Tue Jul 12, 2022 6:11 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

they should be interchangeable the autoformer just has a single ground wire and the TVC has two (primary and secondary) which are connected together.


dave
by dave slagle
Sun Jul 10, 2022 12:12 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

that depends on the preamp design and ultimately the signal levels involved. The 6H30 has a mu of 15 so call it a gain of 3.75 after the stepdown. Feed it with 2V in and you net a meax of 7.5V out which is fine for the autoformers. Feed it with 4V and you might start to run into low frequency overlo...
by dave slagle
Thu Jun 30, 2022 11:44 am
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

The pinout of the transformer appears to match the datasheet. the only difference is one is mirrored from the other 1:4 in the spec sheet and 4:1 in the schematic. It looks to me like the connections you need to change are at the input and output of the board so no traces should need to be cut. dave
by dave slagle
Wed Jun 29, 2022 2:44 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

ugh... slicing traces gets interesting... it looks like the 1674's are on their own boards with yellow wires to connect to the main board.

where is the 680nF 'parafeeed cap'

dave
by dave slagle
Wed Jun 29, 2022 12:30 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

The 1674 appears to be a 1+1:4+4 that is being used as a 4+4:1+1 so the mirror image of the spec sheet matches the schematic above.

dave
by dave slagle
Tue Jun 28, 2022 1:27 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

I now see the TVC's and they are early versions prior to john working with me so they may have been doing the SE>>balanced conversion at the input. To test for proper function I would put a SE signal between L+ and "ref" and groundL- to Ref. Then on the LL1674 disconnect pin 7 from L- and ...
by dave slagle
Mon Jun 27, 2022 2:12 pm
Forum: Circuits
Topic: When and where to ground
Replies: 54
Views: 13584

Re: When and where to ground

Since John mentioned you needed 4 "TVC" units I suspect they were not TVCs but my autoformers. The original bent units used S&B TVC's which could fo bal>>SE and SE>>bal connections (albeit not very well). Your autoformers are ready to ship but I want to hold off until I am sure things ...