Dummy-head again... I found a mistake in my simulations, so the HF drop was not a result of the tranny primary coil. It was a connection error within the circuit in the simulator.
Time for bed!
-Frank
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GK rails in a pedal?
- Thread starter sprag
- Start date
Dummy-head again... I found a mistake in my simulations, so the HF drop was not a result of the tranny primary coil. It was a connection error within the circuit in the simulator.
Time for bed!
-Frank
Here is the freq response that I get on the simulator with the TY250 primary coil attached to the circuit thru 1K resistor at R1/R2:
This shows more HF roll-off than John's actual measurement. So the actual circuit is performing a bit better than the simulated one.
The freq response before all of the recent changes was perfectly flat past 20KHz, but this would still considered to be very good with the -3dB point at approx 15KHz and John's actual amp is only measuring a -1dB drop at 20KHz, which is very, very good.
-Frank
This shows more HF roll-off than John's actual measurement. So the actual circuit is performing a bit better than the simulated one.
The freq response before all of the recent changes was perfectly flat past 20KHz, but this would still considered to be very good with the -3dB point at approx 15KHz and John's actual amp is only measuring a -1dB drop at 20KHz, which is very, very good.
-Frank
This is the output clipping with a 200Hz 0.5Vp-p input signal (red trace) and with the supply voltages that John measured from his amp.
-Frank
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
hmmm. it tried it again this morning with the TY250P connected to the 1K coming from R1/R2 and it has a TON of top end rolloff, so I've yet to hear the transformer sound right in the circuit.
I'm thinking that the tranny may have an issue with high a level input signal from the output drivers. That's why I suggested connecting it to VR1, so you can try different levels to see if that is the problem. If we find the tranny doesn't take large levels well, we can easily fix that.
-Frank
- Feb 16, 2008
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This is crazy! OK, let's nix the tranny from V5 and when I get some time I will experiment with the tranny and come up with a circuit for it. I started another thread about this tranny where I will post that information when I get it.
New V5 schematic in a few mins.
-Frank
New V5 schematic in a few mins.
-Frank
***IMAGE REMOVED- WE HAVE A NEWER VERSION LATER IN THIS THREAD***
V5 without tranny:
On this V5 I added a switch to simulate cabs without tweeters. If you use a double throw switch with a center off position you can have three settings... full bandwidth, 7.2KHz roll-off and 16Khz roll-off. You can change the freqs by calculating a simple RC filter with the 1K resistor at R7. If you change the value of R7 these cap values will need to be recalculated.
-Frank
V5 without tranny:
On this V5 I added a switch to simulate cabs without tweeters. If you use a double throw switch with a center off position you can have three settings... full bandwidth, 7.2KHz roll-off and 16Khz roll-off. You can change the freqs by calculating a simple RC filter with the 1K resistor at R7. If you change the value of R7 these cap values will need to be recalculated.
-Frank
Last edited:
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
okay, i'm pretty sure that I have the latest V5 PCB drawn up correctly so i'll be etching, building and testing it soon. 
John, when you tried the VR1 level test on the primary with the TY250, what was hooked to the secondary?
And I will be testing that TY250 today with my SWR amp.
:***:
-Frank
okay, i'm pretty sure that I have the latest V5 PCB drawn up correctly so i'll be etching, building and testing it soon.
And I will be testing that TY250 today with my SWR amp.
:***:-Frank
- Feb 16, 2008
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- 23,634
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- John K Custom Basses
- May 20, 2000
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- Endorsing Artist: Aguilar Amplification, Spector, Dingwall, Tech 21 NYC, Darkglass
While it hasn't been my #1 amp in some time I've owned and use G-K 800RB amps for 20 years, and still use one weekly.
This is a great project, I also just sent John $10 for supplies (be they pedal bits or tacos). I own a couple of JohnK built boxes and they're excellent.
Frank, if you post your paypal I'll send you a matching $10 for brain fuel.
This is a great project, I also just sent John $10 for supplies (be they pedal bits or tacos). I own a couple of JohnK built boxes and they're excellent.
Frank, if you post your paypal I'll send you a matching $10 for brain fuel.
Thanx Andrew! But I am doing this for fun and to exercise dormant brain cells. But if you do get one of these I would appreciate a sound clip though.
-Frank
John. When you did your listening tests with the tranny, what amplifier did you connect the secondary output to? I am trying to recreate the results that you were hearing.
For anyone that's interested, I have posted some TY250 tranny tests in this thread:
http://www.talkbass.com/threads/an-...sformer-for-the-diyers.1113802/#post-16795141
-Frank
For anyone that's interested, I have posted some TY250 tranny tests in this thread:
http://www.talkbass.com/threads/an-...sformer-for-the-diyers.1113802/#post-16795141
-Frank
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
This thread is really making me want to spend that $300 burning a hole in my pocket on a 400rb. I have a feeling it would sound monstrous when cranked through my 810e.
I happen to know an 800RB cranked thru an 810 is a Most Beautiful Thing!
...and now back to the Boomer & John Show!
