I've been directed here by a kind member in the tube sub-forum of DIYAUDIO.
I've pulled two output transformers and a power transformer out of storage.
There's clearly a bit of cleaning up to do on the output trannies!
Can anyone recommend a suitable TUBELAB amplifier to build using these pieces of iron?
Output transformer specs:
5K to 8 ohms
Frequency Response 20 Hz to 90 kHz
Maximum DC Bias Current: 90 mA
Primary DC Resistance: 370 ohm
Primary Inductance: 40 H
Part Number Transcendar TT-012-OT
Power transformer specs:
I've pulled two output transformers and a power transformer out of storage.
There's clearly a bit of cleaning up to do on the output trannies!
Can anyone recommend a suitable TUBELAB amplifier to build using these pieces of iron?
Output transformer specs:
5K to 8 ohms
Frequency Response 20 Hz to 90 kHz
Maximum DC Bias Current: 90 mA
Primary DC Resistance: 370 ohm
Primary Inductance: 40 H
Part Number Transcendar TT-012-OT
Power transformer specs:
Your power transformer was likely intended for a small guitar amp with less than 20 watts of power, likely using 6AQ5's, 6V6's, 6CW5's or possibly EL84's. It can only deliver a B+ voltage of 225 to 250 volts depending on the rectifier being used. It does not have the power capability needed for any of the typical Tubelab HiFi stereo amps.
The output transformers are good for any single ended HiFi amp that uses a tube that is compatible with a 5K ohm load impedance. The Tubelab SSE board with any of the typical audio output tubes, 6L6GC, EL34, KT88, 6550 and many others would be one possibility. Another is the TSE-II with 45s or 300Bs.
Single ended OPT's are specifically gapped to allow for a DC current through the primary. You can see this gap as a parting line in the laminations about 1.5 cm from the bottom in your picture. The width of this gap is critical to the performance of the transformer. Some transformers use an air gap and some use a non conductive shim, usually some sort of plastic or fiberboard. Disassembly of an SE OPT is generally not recommended especially if the gap is air. The four bolts that hold the end bells on are usually what keeps the gap constant so they should not be loosened or removed.
Each individual lamination is usually coated with a non conductive varnish to eliminate unwanted "eddy currents" in the core. Attempting to sand off the rust can actually make matters worse in some cases since rust is less conductive than bare steel, though I have seen conflicting opinions on this. I have just taped up the end bells and painted over the rust on the laminations in transformers with surface rust like this.
The output transformers are good for any single ended HiFi amp that uses a tube that is compatible with a 5K ohm load impedance. The Tubelab SSE board with any of the typical audio output tubes, 6L6GC, EL34, KT88, 6550 and many others would be one possibility. Another is the TSE-II with 45s or 300Bs.
Single ended OPT's are specifically gapped to allow for a DC current through the primary. You can see this gap as a parting line in the laminations about 1.5 cm from the bottom in your picture. The width of this gap is critical to the performance of the transformer. Some transformers use an air gap and some use a non conductive shim, usually some sort of plastic or fiberboard. Disassembly of an SE OPT is generally not recommended especially if the gap is air. The four bolts that hold the end bells on are usually what keeps the gap constant so they should not be loosened or removed.
Each individual lamination is usually coated with a non conductive varnish to eliminate unwanted "eddy currents" in the core. Attempting to sand off the rust can actually make matters worse in some cases since rust is less conductive than bare steel, though I have seen conflicting opinions on this. I have just taped up the end bells and painted over the rust on the laminations in transformers with surface rust like this.
Thx @Tubelab_com
SSE EL34 sounds like a plan!
Re the rusty output transformers, very good advice! I emailed a friend of mine Jack Elliano who used to make transformers for Electra Print.
He gave the following similar suggestion:
"The transcendar’s rust means they did not varnish them why? I have no idea!!
Rust is just another oxide on the lams will not hurt anything in the transformer,
Just paint them with a dark grey paint (DO NOT SAND OFF THE RUST!!)
That will alter the low frequency due to removing the original oxide on them will make the lams metal contact themselves!!
Just paint over the rust. And paint the bell ends too, those you can sand if needed.
The laminations are each an individual oxide covered lamination!!
That is why they work. Notice no one used just a block of steel!!! Because it will not work at all!!!
The frequency response indicated is not correct, should have its sloop limit/s or -1db points.
1db is the least change you can hear. -3db is half power!!
Do not know about Transcendar fate if any, out of touch these days."
SSE EL34 sounds like a plan!
Re the rusty output transformers, very good advice! I emailed a friend of mine Jack Elliano who used to make transformers for Electra Print.
He gave the following similar suggestion:
"The transcendar’s rust means they did not varnish them why? I have no idea!!
Rust is just another oxide on the lams will not hurt anything in the transformer,
Just paint them with a dark grey paint (DO NOT SAND OFF THE RUST!!)
That will alter the low frequency due to removing the original oxide on them will make the lams metal contact themselves!!
Just paint over the rust. And paint the bell ends too, those you can sand if needed.
The laminations are each an individual oxide covered lamination!!
That is why they work. Notice no one used just a block of steel!!! Because it will not work at all!!!
The frequency response indicated is not correct, should have its sloop limit/s or -1db points.
1db is the least change you can hear. -3db is half power!!
Do not know about Transcendar fate if any, out of touch these days."
I used both the 3 and 5K Transcendars with the SSE board. They are a good match for the SSE.
You might consider using 6V6 ( or with an adapter 6AQ5 - same tube, different bottle ) - there is a fair amount of information on using 6V6 in the SSE board here in this sub forum, a number of people have done it. 5K will work okay with 6V6. Your power transformer current is fine for 6V6; voltage will be marginal but should be okay for almost a watt or so of output.
Win W5JAG
You might consider using 6V6 ( or with an adapter 6AQ5 - same tube, different bottle ) - there is a fair amount of information on using 6V6 in the SSE board here in this sub forum, a number of people have done it. 5K will work okay with 6V6. Your power transformer current is fine for 6V6; voltage will be marginal but should be okay for almost a watt or so of output.
Win W5JAG