TBC choices; Hotronic AP41-SF for starters

[videobruce]

I never owned a TBC untill now. Back in the 80's these were $5k and up, which was out of my price range. I use to do video production and had to find something less expensive. I used a number of consumer 'Proc amps', but they only adjusted Y and chroma levels and boosted 'sharpness' (usually incorrectly). I did wind up with one that reinserted H&V sync and burst, but didn't do that great of a job at it. It solved the probelm of rolled off burst and reduced sync (a huge problem with consumer equipment), but didn't do any 'Time base correction'.

I didn't have a clue where to go, so I took a look on e-bay to see what was available. There I saw alot of old names I remembered back in the 80's. In the under $500 catgory it was hard to find one that had both S-video input and outputs. Some had a S-video input, but no output. I did find these Hotronic AP41's that had/have several options/versions. This one, the "SF" version did have a S-video input and output. The S-VHS deck (JVD HR-S5800U) and the DVD/HDD recrorder (Funai/Maggotbox H2160MW9) I have both have S-Video in's and out's. My past experiance with composite vs S-video wasn't that impressive, Yes, there is a difference, but depending on the monitor's comb filter and the material itself, many times it didn't make much of a difference. But, I wanted the best signal route, so I ruled out any TBC w/o S-video.

Well, I stumbled across a AP41-SF (which also is a current model that sells over $1,000) for $120. No box or manual etc, but it worked (sort of). Here is my review. I didn't really look into any of these consumer versions that have been mentioned here. What would be nice, if any of you that have any of these and have a scope and signal generator that could run similar tests and post pics as I have for a somewhat meanful comparision. The next closest thing would be looping a DVD test disc that has multiburst patterns through the TBC.

[videobruce]

Pros;
1. Cheap: $120,
2. US made (at least was when this was made in 1992), professional model,
3. Current model (important for support and parts). I didn't want a 'boat anchor',
4. S video in and out,
5. Tweakable. Plenty of 'pots' for alignment,
6. Has internal R&B gain controls for white balance (easy to move these to front panel access)
7. Lightweight (compared to many older boat anchors), but with an aluminum case (for proper RF shielding) as opposed to a cheap plastic box,
8. OK S-video bandwidth (but could be better).

Cons,
1. Since it is a 'rack mount' model (just about all professional models are), it is large: 17"x17" (but could easily be placed under other equipment, much as a power switch center is placed under a computer monitor),
2. Composite input almost useless. Terrible bandpass, rolls off above 2.5 MHz making it only useable for standard VHS and Beta (no S-VHS),
3. Bypass switch is only for composite,
4. No center detent controls,
5. Non removeable power cord (very unusual for this type of equipment).

[videobruce]

Using a B&K 1253 portable signal generator and a plain oscilloscope, here are screen shots of a multiburst pattern. The packets are not the standard they normally are. They are as follows; .75, 1.125, 2.25, 3.375, 4.5 and 6.75 MHz. All are visable, but the last packet in the shot from the 57" DLP they were viewed on (S video in) is nonexistent.

[videobruce]

Here is looping through the TBC's S video input. (the video level of the TBC was not adjusted properly, it's a little low, so disregard that aspect). It's hard to tell with the screen shot, (it was reduced to much), but the last packet is slightly worst than running direct. The scope shot clearly shows the difference. Not great, but very useable for S-VHS, but not for a DVD;

[videobruce]

Now the same signal using the composite input. Note the obvious 'bump' to the 2nd packet to make up for the roll off of the third (forget about everything beyond that). Useable for VHS or Beta, but that is pushing it. Remember the 3rd burst packet is only 2.25 MHz which is around 190 lines of horitzontal resolution;

[videobruce]

For a more meaningful pattern, here is a sceen shot of a standard camera resolution pattern that was recorded on S-VHS with a three chip camera (1st generation, not a copy). The shot is looping through the TBC. I compared it direct off the recorder, but there wasn't any real noticeable difference on the 1080 DLP. Again, the pics off the TV were reduced way too much, making it very hard to see much difference.

[lordsmurf]

These older TBCs are often known for degrading quality, mostly because they've been used to death. From what I see here, this might be acceptable. I'm not a test pattern fan, I'd want to see it under usage against a AVT-8710 or TBC-1000, known good TBCs.

[videobruce]

Test patterns tell you far more than subjective viewing of varable quality material. They are consistant, repeatable tests which is why they are called 'test patterns'. I understnad no one watches 'color bars', but anytime any product is speced, it is done using these methods (but with far better equipment that what was used here). What doesn't show up here is noise tests, especially chroma, since the output of the generator is only a Y signal. It was designed for component video, not composite or S-video. I wish I still had my WM monitor and vetroscope.
Yes, I would like to see this AVT-8710 and especially the CBT-530 in similar tests. That TBC-1000 I would rule out since it does not have any proc amp controls which makes it a deal breaker AFAIC.

BTW, it does solve the 'problem AGC' of the Funai DVR (which I figured it would) that I posted elsewhere.

[videobruce]

I decided to return this TBC for the stated issues and the fact their support borders on useless. Between a phonne call and a e-mail, none of the questions were answered.
I just called the importer regarding this popular AVT08710, and talked to a salesman. He tells me the more expensive 1T-TBC is a overall better proformer than the AVT-8710.

It has continuously variable adjustments (eg.: like a volumne control) vs 'stepped' adjustments (eg.: bass & treble controls for a car radio) with the 8710. He also says it has better freq. response than the 1T-TBC and can lock to lower quality signals. I asked him about the freq. response and S/N ratio of the 8710 and how many steps and resulting db change each press of the button would provide when using the Proc Amp controls. He had no idea (no surprise). He offered to pass me over to someone in technical.

I repeated the questions, but didn't really get any answers. There are published specs for the 1T-TBC, but none for the AVT-8710 other than size, weight and ins and outs. He then talked to someone else and admitted both have the same circuit board. $230 more for a metal case, BNC connectors, two inputs and audio pass through.

My questions are;
1. Can the plastic case of the 8710 be opened (screws), or is it glued?,
2. Has anyone opened it and took pictures?,
3. How many 'steps' plus and minus from center for each proc amp control?

The last one might need a scope to verify unless you have a good eye.

[lordsmurf]

After your recent PM to me, I answer those here:
http://www.digitalfaq.com/forum/showthread.php/avt-8710-tbc-1496.html

I took my AVT-8710 apart for you, and took some photos that are posted up there. (Note: Fixed the image errors made the first time I posted it!)

[videobruce]

I tried viewing those pics, but the forum doesn't let me (after I created a new account and signed in) with this message:
"you do not have permission to access this page"
How about posting thme here?

BTW, there is another version; AP41-SP that has a wide band filter for the composite input that should solve the poor response problem.[/i]

[videobruce]

The following is a report on a ForA FA-300 TBC. This was manufactured 5/89. These pics are the two boards inside this TBC;

This board is just memory;


This is the main board;

[videobruce]

The unit is heavt. Around 20 lbs. Unlike the Hotronic, it was made in Japan.

Pro's;
1. Component out (not tested),
2. Better composite frequency response (see photos),
3. Cheaper service manual ($36 vs $100 for the Hotronic),
4. S-video and Y/358 7 pin inputs and outputs.

Cons;
1. Heavy,
2. Controls behind a flip down front panel, some switches hard to throw,
3. Noisey fans (2),
4. Slightly higher power consumption.

Composite multiburst (color burst is missing due to signal generator used);


For conveinance, here is the Hotronic composite multiburst;


S-video multiburst;


For conveinance, here is the Hotronic S-video multiburst;

[Brad]

I recently bought a Hotronic AP41-SP, so I will probably post my findings here when I get a chance to try it. For now I just want to attach the images that are still working since some of them have already been removed from videobruce's Photobucket account.

The following is a report on a ForA FA-300 TBC. This was manufactured 5/89. These pics are the two boards inside this TBC;

This board is just memory;


This is the main board;

Composite multiburst (color burst is missing due to signal generator used);


S-video multiburst;

[Brad]

Gah. I don't know where I got the idea that the one I ordered was the "-SP" variant, but not only is it the barebones model, the BNC input is actually deformed like it was bashed upward with a hammer. So much for that.